Principles of Surgery, Companion Handbook - page 8

Chapter 6 Trauma

Principles of Surgery Companion Handbook

CHAPTER
6
TRAUMA

Initial Evaluation and Resuscitation of the Injured Patient
 Primary Survey of the Trauma Patient
 Secondary Survey
 Regional Assessment of Injury and Special Diagnostic Tests
Treatment
 Head
 Neck
 Thoracic Outlet
 Chest
 Abdomen
 Pelvis
 Extremities
Bites and Stings of Animals and Insects
 Rabies
 Snakes
 Stinging Insects and Animals

INITIAL EVALUATION AND RESUSCITATION OF THE INJURED PATIENT

Primary Survey of the Trauma Patient

Airway Management Ensuring an adequate airway is the first priority in the primary survey. Efforts to restore cardiovascular integrity will be futile if the oxygen content of the blood is inadequate.

Patients who are conscious and have a normal voice do not require further evaluation or early attention to their airway. Exceptions to this principle include patients with penetrating injuries to the neck and an expanding hematoma; patients with evidence of chemical or thermal injury to the mouth, nares, or hypopharynx; and patients with extensive subcutaneous air in the neck, complex maxillofacial trauma, or airway bleeding. These patients initially may have a satisfactory airway, but it may become obstructed if soft tissue swelling or edema progresses.

Patients who have an abnormal voice or altered mental status require further airway evaluation. Direct laryngoscopic inspection often reveals blood, vomit, the tongue, foreign objects, or soft tissue swelling as sources of airway obstruction. Suctioning can offer immediate relief in many patients. Altered mental status is the most common indication for intubation because of the patient's inability to protect the airway. Options for airway access include nasotracheal intubation, orotracheal intubation, or operative intervention.

Orotracheal intubation can be performed in patients with potential cervical spine injuries provided that manual in-line cervical immobilization is maintained. The advantages of orotracheal intubation are direct visualization of the vocal cords, the ability to use larger-diameter endotracheal tubes, and applicability to apneic patients. The disadvantage of orotracheal intubation is that conscious patients usually require neuromuscular blockade or deep sedation.

Patients in whom attempts at intubation have failed or are precluded because of extensive facial injuries require a surgical airway. Cricothyroidotomy and percutaneous transtracheal ventilation are preferred over tracheostomy because of their simplicity and safety. One disadvantage of cricothyroidotomy is the inability to place a tube greater than 6 mm in diameter because of the limited aperture of the cricothyroid space. Cricothyroidotomy also is contraindicated in patients under the age of 12 because of the risk of damage to the cricoid cartilage and the subsequent risk of subglottic stenosis.

Percutaneous transtracheal ventilation is accomplished by inserting a large-bore intravenous catheter through the cricothyroid membrane into the trachea and attaching it with tubing to an oxygen source capable of delivering 50 lb/in2 or more. A hole cut in the tubing allows for intermittent ventilation by occluding and releasing the hole. Adequate oxygenation can be maintained for more than 30 min. Because exhalation occurs passively, ventilation is limited, and carbon dioxide retention can occur.

Breathing Once a secure airway is obtained, adequate oxygenation and ventilation must be ensured. All injured patients should receive supplemental oxygen therapy and be monitored by pulse oximetry. Immediate threats to life because of inadequate ventilation are (1) tension pneumothorax, (2) open pneumothorax, and (3) flail chest/pulmonary contusion. The diagnosis of tension pneumothorax is implied by the finding of respiratory distress in combination with any of the following physical signs: tracheal deviation away from the affected side, lack of or decreased breath sounds on the affected side, distended neck veins or systemic hypotension, or subcutaneous emphysema on the affected side. Immediate tube thoracostomy is indicated without awaiting chest x-ray confirmation.

An open pneumothorax or sucking chest wound occurs with full-thickness loss of the chest wall, permitting a free communication between the pleural space and the atmosphere. In addition to collapse of the lung on the injured side, if the diameter of the injury is greater than the narrowest portion of the upper airway, air preferentially moves through the injury site rather than the trachea and impairs ventilation on the contralateral side. Occlusion of the injury may result in converting an open pneumothorax into a tension pneumothorax. Definitive treatment requires wound closure and tube thoracostomy.

Flail chest occurs when four or more ribs are fractured in at least two locations. Paradoxical movement of this free-floating segment of chest wall may be sufficient to compromise ventilation. It is of greater physiologic importance that patients with flail chest frequently have an underlying pulmonary contusion. Respiratory failure in these patients may not be immediate, and frequent reevaluation is warranted.

Circulation With a secure airway and adequate ventilation established, circulatory status is determined. A rough first approximation of the patient's cardiovascular status is obtained by palpating peripheral pulses. External control of hemorrhage should be obtained before restoring circulating volume. Manual compression and splints frequently control extremity hemorrhage as effectively as tourniquets. Blind clamping should be avoided because of the risk to adjacent structures. Digital control of hemorrhage for penetrating injuries of the head, neck, thoracic outlet, groin, and extremities is important. Scalp lacerations through the galea aponeurotica tend to bleed profusely; these can be controlled temporarily with Rainey clips or a full-thickness large nylon continuous stitch.

Intravenous access for fluid resuscitation is begun with two peripheral catheters, 16-gauge or larger in an adult. Blood is drawn simultaneously and sent for typing and hematocrit measurement. For patients requiring vigorous fluid resuscitation, saphenous vein cutdowns at the ankle or percutaneous femoral vein catheter introducers are preferred. The saphenous vein is reliably found 1 cm anterior and 1 cm superior to the medial malleolus.Venous access in the lower extremities provides effective volume resuscitation in cases of abdominal venous injury, including the inferior vena cava.

In hypovolemic pediatric patients less than 6 years of age, percutaneous femoral vein cannulation is contraindicated because of the risk of venous thrombosis. If two attempts at percutaneous peripheral access are unsuccessful, interosseous cannulation should be performed in the proximal tibia or in the distal femur if the tibia is fractured.

Initial Fluid Resuscitation Initial fluid resuscitation is a 1-L intravenous bolus of isotonic crystalloid in an adult or 20 mL/kg of body weight lactated Ringer's solution in a child. This is repeated once in an adult and twice in a child before administering red blood cells. The goal of fluid resuscitation is to reestablish tissue perfusion. Classic signs and symptoms of shock are tachycardia, hypotension, tachypnea, mental status changes, diaphoresis, and pallor. None of these signs or symptoms taken alone can predict the patient's organ perfusion status.

Hypotension is not a reliable early sign of hypovolemia. In healthy patients, blood volume must decrease by 30–40 percent before hypotension occurs (Table 6-1). Younger patients with good sympathetic tone can maintain systemic blood pressure with severe intravascular deficits until they are on the verge of cardiac arrest.



TABLE 6-1 SIGNS AND SYMPTOMS FOR DIFFERENT CLASSES OF SHOCK



Acute changes in mental status can be caused by hypoxia, hypercarbia, or hypovolemia, or they may be an early sign of increasing intracranial pressure (ICP). Urine output is a quantitative and relatively reliable indicator of organ perfusion. Adequate urine output is 0.5 mL/kg/h in an adult, 1 mL/kg/h in a child, and 2 mL/kg/h in an infant less than 1 year of age.

Central venous pressure (CVP) determines right ventricular preload; in otherwise healthy trauma patients, its measurement yields objective information regarding the patient's overall volume status. A hypotensive patient with flat neck veins and a CVP of less than 5 cmH2O is hypovolemic and is likely to have ongoing hemorrhage. In trauma patients, the differential diagnosis of cardiogenic shock is indicated by (1) tension pneumothorax, (2) pericardial tamponade, (3) myocardial contusion or infarction, and (4) air embolism. Tension pneumothorax is the most frequent cause of cardiac failure. Traumatic pericardial tamponade most often is associated with penetrating injury to the heart. As blood leaks out of the injured heart, it accumulates in the pericardial sac. Because the pericardium is not acutely distendible, the pressure in the pericardial sac rises to match that of the injured chamber. This pressure usually is greater than that of the right atrium; right atrial filling is impaired, and right ventricular preload is reduced. This leads to decreased right ventricular output and increased CVP. This cycle may progress insidiously with injury of the venae cavae or atria or precipitously with injury of either ventricle. The classic findings of Beck's triad (hypotension, distended neck veins, and muffled heart sounds) and pulsus paradoxus are not reliable indicators of acute tamponade. Ultrasound imaging in the emergency room using a subxiphoid or parasternal view is helpful if the findings are clearly positive, but equivocal findings are common. Early in the course of tamponade, blood pressure and cardiac output transiently improve with fluid administration.

Once the diagnosis of cardiac tamponade is established, pericardiocentesis should be performed. Evacuation of as little as 15–25 mL of blood can dramatically improve the patient's hemodynamic profile. While pericardiocentesis is being performed, preparation should be made for emergent transport to the operating room. Emergent pericardiocentesis is successful in decompressing the tamponade in approximately 80 percent of patients; most failures are a result of clotted blood within the pericardium. If pericardiocentesis is unsuccessful and the patient remains severely hypotensive (systolic blood pressure < 70 mmHg) or shows other signs of hemodynamic instability, emergency room thoracotomy should be performed.

Myocardial contusion from direct myocardial impact occurs in approximately one-third of patients sustaining significant blunt chest trauma. The diagnostic criteria for myocardial contusion include specific electrocardiogram (ECG) abnormalities, i.e., ventricular dysrhythmias, atrial fibrillation, sinus bradycardia, and bundle branch block. Transient sinus tachycardia is not indicative of contusion. Serial cardiac enzyme determinations (CPK-MB fraction) lack sensitivity. Arrhythmias are treated by pharmacologic suppression. The management of cardiogenic shock from cardiac pump failure includes an urgent ECG to rule out septal or free wall rupture, valvular disruption, or pericardial tamponade.

Air embolism is a frequently overlooked lethal complication of pulmonary injury. It occurs when air from an injured bronchus enters an adjacent injured pulmonary vein and returns to the left side of the heart. Air accumulation in the left ventricle impedes diastolic filling, and during systole, it is pumped into the coronary arteries, disrupting coronary perfusion. The typical scenario is a patient with a penetrating chest injury who appears hemodynamically stable but suddenly goes into cardiac arrest after being intubated and placed on positive-pressure ventilation. The patient should be placed in the Trendelenburg position to trap the air in the apex of the left ventricle. Emergency thoracotomy is followed by cross-clamping the pulmonary hilum on the side of the injury to prevent further introduction of air. Air is aspirated from the apex of the left ventricle with an 18-gauge needle and 50-mL syringe. Vigorous open cardiac massage is used to force the air bubbles through the coronary arteries. The highest point of the aortic root also is aspirated to prevent air from entering the coronary arteries or embolizing to the brain. The patient should be kept in the Trendelenburg position and the hilum clamped until the pulmonary venous injury is controlled.

Secondary Survey

When the conditions that constitute an immediate threat to life have been attended to or excluded, the patient is examined in a systematic fashion to identify occult injuries. Patients should undergo digital rectal examination to evaluate sphincter tone and to look for blood, perforation, or a high-riding prostate. A Foley catheter should be inserted to decompress the bladder, obtain a urine specimen, and monitor urine output. Stable patients at risk for urethral injury should undergo urethrography before catheterization. A nasogastric tube should be inserted to decrease the risk of gastric aspiration and allow inspection of the contents for blood suggestive of occult gastroduodenal injury.

Selective radiographs are obtained early in the emergency room. For patients with severe blunt trauma, anteroposterior chest and pelvic radiographs should be obtained as soon as possible. For patients with truncal gunshot wounds, posteroanterior and lateral radiographs of the chest and abdomen are warranted.

Regional Assessment of Injury and Special Diagnostic Tests

Head A score based on the Glasgow Coma Scale (GCS) should be determined for all injured patients (Table 6-2). Examination of the head should focus on potentially treatable neurologic injuries. The presence of lateralizing findings is important; e.g., a unilateral dilated pupil unreactive to light, asymmetric movement of the extremities either spontaneously or in response to noxious stimuli, or a unilateral Babinski's reflex suggests a treatable intracranial mass lesion or major structural damage. Stroke syndromes should prompt a search for carotid dissection or thrombosis using duplex scanning or angiography. Otorrhea, rhinorrhea, “raccoon eyes,” and Battle's sign (ecchymosis behind the ear) can be seen with basilar skull fractures.



TABLE 6-2 GLASGOW COMA SCALE*



Cerebral pathologic lesions from blunt trauma include hematomas, contusions, hemorrhage into ventricular and subarachnoid spaces, and diffuse axonal injury (DAI). Epidural hematomas occur when blood accumulates between the skull and the dura and are caused by disruption of the middle meningeal artery or other small arteries in that potential space from a skull fracture. Subdural hematomas occur between the dura and the cerebral cortex and are caused by venous disruption or laceration of the parenchyma of the brain. Because of the underlying brain injury, the prognosis is worse with subdural hematomas. Intraparenchymal hematomas and contusions can occur anywhere within the brain. Hemorrhage may occur into the ventricles, and though usually not massive, this blood may cause postinjury hydrocephalus. Diffuse hemorrhage into the subarachnoid space may cause vasospasm and reduce cerebral blood flow. DAI results from high-speed deceleration injury and represents direct axonal damage. Early evidence of DAI on computed tomographic (CT) scan is associated with a poor outcome.

Neck In evaluating the neck of a blunt trauma victim, attention should be focused on signs and symptoms of an occult cervical spine injury. Because of the devastating consequences of quadriplegia, all patients should be assumed to have cervical spine injuries until proved otherwise. The presence of posterior midline pain or tenderness should provoke a thorough radiologic evaluation. A cervical spine series including lateral view with visualization of C7–T1, anteroposterior view, and transoral odontoid view are sufficient to detect most significant fractures and subluxations. If pain or tenderness persists despite normal appearance on plain x-ray films, a CT scan should be done. CT identifies most fractures but can miss some subluxations. A combination of plain film and CT imaging can identify virtually all injuries; an exception is a purely ligamentous injury. These rare and dangerous injuries may not be visible with standard imaging techniques. Flexion and extension views can be performed and may reveal opening of the intervertebral space. This should only be done in the presence of an experienced surgeon; patients with injuries have become permanently quadriplegic when flexed and extended by inexperienced individuals.

There are several partial or incomplete spinal cord injury syndromes. Central cord syndrome usually occurs in older persons who suffer hyperextension injuries. Motor function, pain, and temperature sensation are preserved in the lower extremities but diminished in the upper extremities. Some functional recovery usually occurs, but it is seldom a return to normal. Anterior cord syndrome is characterized by diminished motor function and pain and temperature sensation below the level of the injury. Position, vibratory, and crude touch sensation is maintained. Prognosis for recovery is poor. Brown-Séquard's syndrome usually is the result of a penetrating injury in which the right or left half of the spinal cord is transected. This rare lesion is characterized by ipsilateral loss of motor function, proprioception, and vibratory sensation; pain and temperature sensation is lost on the contralateral side.

Penetrating injuries of the anterior neck that violate the platysma are considered significant because of the density of critical structures in this region. Selective management is based on the neck's division into three zones (Fig. 6-1). Zone I is between the clavicles and the cricoid cartilage and is also referred to as the thoracic outlet. Zone II is between the cricoid cartilage and the angle of the mandible, and Zone III is above the angle of mandible. Because the operative incision to be made may depend on the injured structures, a precise preoperative diagnosis is desirable. Patients with Zone I injuries should undergo angiography of the great vessels, soluble-contrast esophagram followed by barium esophagram, esophagoscopy, and bronchoscopy. Hemodynamically unstable patients should not undergo this extensive evaluation but should be taken directly to the operating room.



FIGURE 6-1 Algorithm for the selective management of penetrating neck injuries.



Patients with Zone II injuries are the easiest to evaluate. Unstable patients or those with evidence of airway compromise, an expanding hematoma, or significant external hemorrhage (including hemorrhage into the mouth) should be explored promptly. Stable patients without these findings can be evaluated selectively. Penetrating neck wounds in stable patients should be explored locally to determine the depth of penetration. Patients with right-to-left transcervical gunshot wounds may require diagnostic studies. Carotid and vertebral angiography, direct laryngoscopy, tracheoscopy, esophagoscopy, and esophagram might be necessary, depending on the bullet's trajectory.

Patients with Zone III penetrating injuries require carotid and vertebral angiography if there is evidence of arterial bleeding. This is important for three reasons: (1) exposure of the distal internal carotid and vertebral arteries is difficult, (2) the internal carotid artery may have to be ligated, a maneuver associated with a high risk of stroke, and (3) active hemorrhage from the external carotid and vertebral arteries can be controlled by selective embolization.

Chest The most threatening occult injury in trauma surgery is a tear of the descending thoracic aorta. Widening of the mediastinum on anteroposterior chest x-ray strongly suggests this injury. The widening is caused by the formation of a hematoma around the injured aorta that is temporarily contained by the mediastinal pleura. Posterior rib fractures and laceration of small vessels also can produce similar hematomas. Other findings suggestive of an aortic tear are noted in Table 6-3. This injury may be present with an entirely normal chest x-ray, although the incidence is approximately 2 percent. Because of the dire consequences of missing the diagnosis, CT and angiography are frequently performed after certain types of injury. In 2–5 percent of patients the tear occurs in the ascending aorta, in the transverse arch, or at the diaphragm. Dynamic, spiral CT is an excellent screening test. A clearly widened mediastinum on chest x-ray or abnormalities on CT are an absolute indication for emergent aortography.



TABLE 6-3 FINDINGS ON CHEST X-RAY SUGGESTIVE OF AN AORTIC TEAR*



Penetrating thoracic trauma is considerably easier to evaluate. Depending on the estimated trajectory of the missile or blade, bronchoscopy should be performed to evaluate the trachea. Esophagoscopy can be performed to evaluate the esophagus, but injuries have been missed with the use of this technique alone. Patients at risk also should undergo a soluble-contrast esophagram. Stable patients should be evaluated carefully for tracheal and esophageal injuries. Angiography occasionally is indicated.

Abdomen For the majority of patients suffering blunt abdominal trauma, it is not clear whether exploration is needed. Serial examinations by the same surgeon can detect early peritoneal inflammation and the need for laparotomy before serious infections and hemorrhagic complications occur. In contrast to gunshot wounds, stab wounds that penetrate the peritoneal cavity are less likely to injure intraabdominal organs. Superficial anterior and lateral stab wounds to the trunk may be explored under local anesthesia in the emergency room to determine whether the peritoneum has been violated. Stab wounds to the flank and back are more difficult to evaluate. Some authorities have recommended a triple-contrast CT scan to detect occult retroperitoneal injuries of the colon, duodenum, and urinary tract. Diagnostic peritoneal lavage (DPL) is the most sensitive test available for determining the presence of intraabdominal injury.

Blunt abdominal trauma is evaluated by ultrasound imaging in most major trauma centers and, in selected patients, with CT scanning to refine the diagnosis. Ultrasound performed by a surgeon or an emergency physician in the emergency room has largely replaced DPL. Ultrasound is used in specific anatomic regions (e.g., Morison's pouch, the left upper quadrant, the pelvis) to identify free intraperitoneal fluid. Despite these limitations, CT is an important diagnostic tool because of its specificity for hepatic, splenic, and renal injuries. CT is indicated primarily for hemodynamically stable patients who are candidates for nonoperative therapy. CT also is indicated for hemodynamically stable patients who have unreliable physical examinations or other conditions (i.e., intracranial injury) requiring CT evaluation.

Pelvis Blunt injury to the pelvis frequently produces complex fractures. Plain x-rays reveal gross abnormalities, but CT scanning may be necessary to assess the pelvis for stability. Urethral injuries are suspected by the findings of blood at the meatus, scrotal or perineal hematomas, and a high-riding prostate on rectal examination. Urethrograms should be done in stable patients before placing the Foley catheter to avoid false passage and subsequent stricture.

Life-threatening hemorrhage can be associated with pelvic fractures. The source may be the lower lumbar arteries and veins or branches of the internal iliac arteries and veins. These injuries are frequently not amenable to surgical repair and usually occur with disruption of the posterior elements of the pelvis.

Extremities Injury of the extremities from any cause requires plain x-ray films to evaluate fractures. Physical examination serves to identify and localize arterial injuries in many instances. Physical findings are classified as hard signs or soft signs (Table 6-4). Hard signs constitute indications for operative exploration, whereas soft signs are indications for observation or additional testing. Arteriography may be helpful in localizing the injury in some patients with penetrating injuries and hard signs.



TABLE 6-4 SIGNS AND SYMPTOMS OF ARTERIAL INJURY



The controversy in vascular trauma is in the management of patients with soft signs of injury, particularly injuries that are in proximity to major vessels. Some of these patients will have arterial injuries that require repair. One approach is to measure systolic blood pressures using Doppler ultrasound and compare the injured side with the uninjured side. If the pressures are within 10 percent of each other, a significant injury is excluded, and no further evaluation is performed.

TREATMENT

TRANSFUSION

Most trauma patients receive between 1 and 5 units of packed red blood cells (pRBCs) and no other components, but major trauma centers have the capability of transfusing tremendous quantities of blood components. It is not unusual for 100 component units to be transfused during one procedure. Red cell transfusion rates of 20–40 units of pRBCs per hour are common in severely injured patients.

Transfusion practices in trauma require the surgeon to identify the insidious signs of coagulopathy, such as excessive bleeding from the cut edges of skin, fascia, and peritoneum that were previously controlled. The usual measurements of coagulation capability, i.e., prothrombin time (PT), partial thromboplastin time (PTT), and platelet count, have a turnaround time of more than 30 min in most institutions. Under such conditions, transfusion must be empiric and based on the surgeon's observations. At the first sign of coagulopathic hemorrhage, the previously lost plasma proteins and platelets must be restored with fresh frozen plasma (FFP) and platelet packs.

Platelet dysfunction is a well-documented complication of massive transfusion that is aggravated by associated hypothermia. Consequently, the recommended target of more than 100,000/mm3 for platelet transfusion in other high-risk patients should be extended to the severely injured.

Blood typing and, to a lesser extent, crossmatching are essential to avoid life-threatening intravascular hemolytic transfusion reactions. A complete type and crossmatch requires 20–45 min to complete and reduces the risk of an intravascular hemolysis to approximately 0.004 percent. Trauma patients requiring emergency transfusions are given type O, type-specific, or biologically compatible red blood cells. As a cross-check for ABO compatibility, a saline crossmatch often is performed.

The administrative and laboratory time required is approximately 5 min, and the risk of intravascular hemolysis is about 0.05 percent. The risk increases to 1.0 percent with a history of previous transfusions or pregnancy and up to 3.0 percent with both. If blood is subsequently needed urgently, low-titer, type-specific red cells can be administered with the same risk of intravascular hemolysis as with fully typed and crossmatched blood, provided the screen for irregular antibodies is negative. Unstable patients should receive O-negative, O-positive, or type-specific red cells, depending on the patient's age and sex and the availability of blood cell types. Other components should be type specific or biologically compatible.

PROPHYLACTIC MEASURES

All injured patients undergoing an operation should receive preemptive antibiotic therapy. Recommended are second-generation cephalosporins for laparotomies and first-generation cephalosporins for all other operations. Tetanus prophylaxis is administered to all patients according to the American College of Surgeons guidelines. Deep venous thrombosis and other venous complications occur more often in injured patients than generally is believed. This is particularly true for patients with major fractures of the pelvis and lower extremities, those with spinal cord injury or in a coma, and those with injury of the large veins in the abdomen and lower extremities.

Another prophylactic measure is thermal protection. Hemorrhagic shock impairs perfusion and metabolic activity throughout the body. With declining metabolism, heat production and body temperature decrease. The injured patient receives a second thermal insult with the removal of insulating clothing. As a result, trauma patients can become seriously hypothermic, with temperatures as low as 34°C by the time they reach the operating room. Hypothermia impairs coagulation and myocardial contractility and increases myocardial irritability. Intentional hypothermia has protective features for patients with massive head injuries, but most physicians agree that the deleterious effects outweigh the potential benefits. Injured patients whose intraoperative core temperature drops below 32°C are at risk for fatal arrhythmias and defective coagulation.

VASCULAR REPAIR

The initial control of vascular injuries should be accomplished digitally by applying enough pressure directly on the bleeding site to stop the hemorrhage. The exposed intima and media at the site of the injury are highly thrombogenic, and small clots often form. These clots should be removed carefully to prevent thrombosis or embolism when the clamps are removed. Because of the frequency that embolism occurs, routine balloon catheter exploration of the distal vessel has been recommended. Ragged edges of the injury site should be judiciously debrided using sharp dissection.

Injuries of the large veins such as the venae cavae or the innominate and iliac veins pose a special problem for hemostasis. Numerous large tributaries make adequate hemostasis difficult to achieve, and their thin walls render them susceptible to additional iatrogenic injury. If hemostasis is not adequate to expose the vessel proximal and distal to the injury, sponge sticks can be placed strategically on either side of the injury and carefully adjusted to improve hemostasis.

Some arteries and most veins can be ligated without significant sequelae. Arteries for which repair should always be attempted include the aorta and the carotid, innominate, brachial, superior mesenteric, proper hepatic, renal, iliac, femoral, and popliteal arteries. In the forearm and lower leg, at least one of the two palpable vessels should be salvaged. The list of veins for which repair should be attempted is the superior vena cava, the inferior vena cava proximal to the renal veins, and the portal vein. There are notable vessels for which repair is not necessary, e.g., the subclavian artery and the superior mesenteric vein. The portal vein can be ligated successfully provided adequate fluid is administered to compensate for the dramatic but transient edema that occurs in the bowel. Some arterial injuries have been treated by observation without subsequent complications. These include small pseudoaneurysms, intimal dissections, small intimal flaps and arteriovenous fistulas in the extremities, and occlusions of small (<2 mm) arteries. Lateral suture is appropriate for small arterial injuries with little or no loss of tissue. End-to-end anastomosis is used if the vessel is transected or nearly so. The severed ends of the vessel are mobilized, and small branches are ligated and divided as necessary to obtain the desired length. Arterial defects of 1–2 cm usually can be bridged.

Interpositional grafts are used when end-to-end anastomosis cannot be accomplished without tension despite mobilization. For vessels less than 6 mm in diameter, autogenous saphenous vein from the groin should be used because polytetrafluoroethylene (PTFE) grafts less than 6 mm in diameter have a prohibitive rate of thrombosis. Injuries of the brachial, popliteal, and internal carotid arteries require the saphenous vein for interpositional grafting. Larger arteries must be bridged by artificial grafts.

Arterial injuries are often grossly contaminated from enteric or external sources, in which case many surgeons are reluctant to place artificial grafts in situ. This situation arises most often in injuries to the aortic or iliac artery when the colon also is injured. For the aorta, there are few options. Even in the presence of fecal contamination, it is common practice to use PTFE or Dacron in situ for aortic injuries. A similar approach can be used for injuries to the iliac artery, but in most cases this can be avoided by the innovative use of transposition procedures.

Venous injuries are more difficult to repair successfully because of their propensity to thrombose. Small injuries without loss of tissue can be treated with lateral suture. More complex repairs often fail. Thrombosis does not occur acutely but rather gradually over 1–2 weeks. Adequate collateral circulation, sufficient to avoid acute venous hypertensive complications, usually develops within several days. It is reasonable to use PTFE for venous interpositional grafting and accept a gradual but eventual thrombosis while waiting for collateral circulation to develop.

STAGED OPERATIONS

Staged operations are indicated when a coagulopathy develops and core temperature drops below 34°C. A refractory acidosis is almost always present. Several unorthodox techniques can be used to expedite wound closure. Bleeding raw surfaces, often of the liver, are packed with laparotomy pads. Small enteric injuries are closed with staples, and large ones are stapled on both sides with the GIA stapler and the damaged segment removed. Clamps may be left on unrepaired vascular injuries, or the vessels may be ligated. Injuries of the pancreas and kidneys are not treated if they are not bleeding. No drains are placed, and the abdomen is closed with sharp towel clips placed 2 cm apart, which include only the skin. The goal is to complete the procedure as soon as possible. If the patient's condition improves, as evidenced by normalization of coagulation studies, the correction of acid-base imbalance, and a core temperature of at least 36°C, the patient should be returned to the operating room for removal of packs and definitive treatment of injuries.

A second complication is referred to as the abdominal or thoracic compartment syndrome, and it is caused by an acute increase in intracavitary pressure. In the abdomen, the compliance of the abdominal wall and the diaphragm permits the accumulation of many liters of fluid before intraabdominal pressure (IAP) increases. The resulting edema may be dramatic. As fluid continues to accumulate, the compliant limit of the abdominal cavity is eventually exceeded, and IAP increases. When IAP exceeds 15 mmHg, serious physiologic changes begin to occur. As IAP exceeds 25–30 mmHg, life-threatening hypoxia and anuric renal failure occur. Cardiac output is further reduced but can be returned toward normal with volume expansion and inotropic support. The only method for treating hypoxia and renal failure is to decompress the abdominal cavity by opening the incision. This results in an immediate diuresis and a resolution of hypoxia. Failure to decompress the abdominal cavity eventually causes lethal hypoxia or organ failure.

NONOPERATIVE MANAGEMENT

Nonoperative treatment for blunt injuries of the liver, spleen, and kidneys is the rule rather than the exception. Up to 90 percent of children and 50 percent of adults are treated in this manner. The primary requirement for this therapy is hemodynamic stability. The extent of the patient's injuries should be delineated by CT scanning. Recurrent hemorrhage from the liver and kidneys has been infrequent, but delayed hemorrhage or rupture of the spleen is an important consideration in the decision to pursue nonoperative management. The patient should be monitored in the intensive care unit for the first 24 h.

Head

Attention is focused on maintaining or enhancing cerebral perfusion rather than merely lowering intracranial pressure (ICP). Hyperventilation to a PCO2 below 30 mmHg to induce cerebral vasoconstriction exacerbates cerebral ischemia despite decreasing ICP. Secondary iatrogenic cerebral injuries cause more harm than previously appreciated. Other treatments or conditions that must be avoided include decreased cardiac output because of the excessive use of osmotic diuretics, sedatives, or barbiturates, and hypoxia. The tube also permits the withdrawal of cerebrospinal fluid, which is the safest method for lowering ICP. Although an ICP of 10 mmHg is believed to be the upper limit of normal, therapy usually is not initiated until the ICP reaches 20 mmHg. Cerebral perfusion pressure (CPP), which is equal to the mean arterial pressure (MAP) minus the ICP, is an important measurement that is used to monitor therapy. The lowest acceptable CPP is 60 mmHg.

Indications for operative intervention for space-occupying hematomas are based on the amount of midline shift, the location of the clot, and the patient's ICP. A shift of more than 5 mm usually is considered an indication for evacuation.

Neck

Cervical Spine Treatment of injuries to the cervical spine is based on the level of injury, the stability of the spine, the presence of subluxation, the extent of angulation, and the extent of neurologic deficit. Surgical fusion usually is reserved for those with neurologic deficit, those who demonstrate angulation greater than 11 degrees on flexion and extension x-rays, or those who are unstable after external fixation.

Spinal Cord Injuries of the spinal cord, particularly complete injuries, are essentially untreatable. Approximately 3 percent of patients who present with flaccid quadriplegia have concussive injuries, and these patients represent the very few who seem to have miraculous recoveries. Methylprednisolone improves the outcome (usually one or two spinal levels) for those who receive the corticosteroid within 8 h of injury.

Larynx The larynx may be fractured by a direct blow, which can result in airway compromise. A hoarse voice in a trauma patient is highly suggestive of laryngeal fracture. In patients with severe fracture, a cricothyroidotomy or tracheostomy should be performed to protect the airway. The larynx is repaired with fine wires and sutures. If direct repair of internal laryngeal structures is necessary, the thyroid cartilage is split longitudinally in the midline and opened like a book. This is referred to as a laryngeal fissure.

Carotid and Vertebral Arteries Blunt injury to the carotid or vertebral artery may cause dissection, thrombosis, or pseudoaneurysm. More than half the patients with such injuries have a delayed diagnosis. Facial contact resulting in hyperextension and rotation appears to be the mechanism of injury. To reduce delayed recognition, CT angiography is performed in patients at risk to identify these injuries before neurologic symptoms develop. The injuries frequently occur at or extend into the base of the skull and usually are not surgically accessible. Accepted treatment for thrombosis and dissection is anticoagulation therapy with heparin followed by warfarin sodium (Coumadin) for 3 months. Pseudoaneurysms also occur near the base of the skull. If they are small, they can be followed with repeat angiography. If enlargement occurs, consideration should be given to the placement of a stent across the aneurysm by an interventional radiologist. Another method is to approach the intracranial portion of the carotid artery by removing the overlying bone and performing a direct repair.

Venous Injuries Thrombosis of the internal jugular veins caused by blunt trauma can occur unilaterally or bilaterally. These injuries usually are discovered incidentally and generally are asymptomatic. Bilateral thrombosis can aggravate cerebral edema in patients with serious head injuries. Stent placement should be considered in such patients if their ICP remains elevated. Laryngeal edema resulting in airway compromise also can occur.

PENETRATING INJURIES

Penetrating injuries in Zone II or Zone III that require operative intervention are explored using an incision along the anterior border of the sternocleidomastoid muscle. If bilateral exploration is necessary, the inferior end of the incision can be extended to the opposite side. Midline wounds or significant bilateral injuries can be exposed via a large collar incision at the appropriate level. Alternatively, bilateral anterior sternocleidomastoid incisions can be used.

Carotid and Vertebral Arteries Exposure of the distal internal carotid artery in Zone III is difficult. The first step is to divide the ansa cervicalis and mobilize the hypoglossal nerve. Next, the portion of the posterior belly of the digastric muscle that overlies the internal carotid artery is resected. The glossopharyngeal and vagus nerves are mobilized and retracted. If accessible, the styloid process and attached muscles are removed. At this point, anterior displacement of the mandible may be helpful, and various methods for accomplishing this have been devised. Some authorities have advocated division and elevation of the vertical ramus, but two remaining structures prevent exposure of the internal carotid to the base of the skull, the parotid gland and the facial nerve. Unless the surgeon is willing to resect the parotid and divide the facial nerve, division of the ramus seldom is helpful. Penetrating carotid artery injuries, regardless of the patient's neurologic status, usually require repair, except in comatose patients. Otherwise, the artery will need to be thrombosed or ligated. If ligation is necessary, the patient should be given anticoagulation therapy with heparin followed by warfarin sodium (Coumadin) for 3 months.

Vertebral artery injuries usually result from penetrating trauma, although thrombosis and pseudoaneurysms can occur from blunt injury. The diagnosis is made by angiography or when significant hemorrhage is noted posterior to the carotid sheath during neck exploration. Exposure of the vertebral artery above the C6 vertebra where it enters its bony canal is complicated by the overlying anterior elements of the canal and the tough fascia covering the artery between the elements. The artery is approached through an anterior neck incision by retracting the contents of the carotid sheath laterally. The muscular attachments to the anterior elements are removed. Care must be taken to avoid injury to the cervical spinal nerves that are located directly behind and lateral to the bony canal. Some authorities have recommended using a high-speed burr to remove the anterior aspect of the canal, thereby avoiding the venous plexus between the elements. We have not found this to be a problem and often have excised the fascia between the elements and lifted the artery out of its canal with a tissue forceps. The treatment for vertebral artery injuries is ligation proximal and distal to the injury.

Trachea and Esophagus Injuries of the trachea are repaired with a running 3-0 absorbable monofilament suture. Tracheostomy is not required in most patients. Esophageal injuries are repaired in a similar fashion. If an esophageal wound is large, or if tissue is missing, a sternocleidomastoid muscle pedicle flap is warranted, and a closed-suction drain is a reasonable precaution. The drain should be near but not in contact with the esophageal or any other suture line. It can be removed in 7–10 days if the suture line remains secure.

Thoracic Outlet

Great Vessels Most injuries of the great vessels of the thoracic outlet (Zone I) are caused by penetrating trauma. Angiography is desirable for planning the incision. If this is not possible because of hemodynamic instability, a reasonable approach can be inferred from the chest x-ray and the location of the wounds. A median sternotomy is used for exposure of the innominate, proximal right carotid and subclavian, and proximal left carotid arteries.

The proximal left subclavian artery presents a unique challenge. Because it arises from the aortic arch far posteriorly, it is not readily approached via a median sternotomy. A posterolateral thoracotomy provides excellent exposure but severely limits access to other structures and is not recommended. The best option is to create a full-thickness flap of the upper chest wall. This is accomplished with a third or fourth interspace anterolateral thoracotomy for proximal control, a supraclavicular incision with a resection of the medial third of the clavicle, and a median sternotomy, which links the two horizontal incisions. The ribs can be cut laterally for additional exposure, which allows the flap to be folded laterally with little effort. The subclavian vein is mobilized, and the artery is directly underneath. The anterior scalene muscle is divided for injuries just proximal to the thyrocervical trunk; the relatively small phrenic nerve should be identified on its anterior aspect and spared. Iatrogenic injury to cords of the brachial plexus can occur.

Trachea and Esophagus The trachea and esophagus are difficult to approach at the thoracic outlet. The combination of a neck incision and a high anterolateral thoracotomy may be used. Alternatively, these structures can be approached via a median sternotomy, provided the left innominate vein and artery are divided. Temporary division of the innominate artery is tolerated well in otherwise healthy people, but the vessel should be repaired after treatment of the tracheal or esophageal injury. The vein does not need to be repaired. As in the neck, adjacent suture lines should be separated by viable tissue. A portion of the sternocleidomastoid can be rotated down for this purpose.

Chest

The most common life-threatening complications from blunt and penetrating thoracic injury are hemothorax, pneumothorax, or a combination of the two. Approximately 85 percent of these patients can be treated definitively with a chest tube. Common sources of blood loss include intercostal vessels, internal thoracic artery, pulmonary parenchyma, and the heart. Less common sources are the great vessels, aortic arch, azygos vein, superior vena cava, and inferior vena cava. Blood also may enter the chest from an abdominal injury through a perforation or tear in the diaphragm. The indications for thoracotomy in blunt trauma are based on specific preoperative diagnoses. These include pericardial tamponade, tear of the descending thoracic aorta, rupture of a main bronchus, and rupture of the esophagus.

Thoracic Incisions The selection of incision is important and depends on the organs being treated. For exploratory thoracotomy for hemorrhage, the patient is supine, and an anterolateral thoracotomy is performed. Depending on findings, the incision can be extended across the sternum or even farther for a bilateral anterolateral thoracotomy. The fifth interspace usually is preferred unless the surgeon has a precise knowledge of which organs are injured and knows that exposure would be enhanced by selecting a different interspace. The heart, lungs, aortic arch, great vessels, and esophagus are accessible with these incisions. Care should be taken to ligate the internal thoracic artery and veins if they are transected. This step often is overlooked, resulting in continuous blood loss that obscures the field and endangers the patient.

The heart also can be approached via a median sternotomy. Because little else can be done in the chest through this incision, it usually is reserved for stab wounds of the anterior chest in patients who present with pericardial tamponade. Posterolateral thoracotomies rarely are used because ventilation is impaired in the dependent lung, and the incision cannot be extended. There are two specific exceptions. Injuries of the posterior aspect of the trachea or main bronchi near the carina tracheae are inaccessible from the left or from the front. The only possible approach is through the right chest using a posterolateral thoracotomy. A tear of the descending thoracic aorta can be repaired only through a left posterolateral thoracotomy. Because we use left heart bypass for these procedures, the patient's hips and legs are rotated toward the supine position to gain access to the left groin for femoral artery cannulation. It is also helpful for optimal exposure to resect the fourth rib and enter the chest through its bed.

Heart Most cardiac injuries are the result of penetrating trauma, and any part of the heart is susceptible. Control of hemorrhage while the heart is being repaired is crucial, and several techniques can be used. The atria can be clamped with a Satinsky vascular clamp. If the hole is small, a “peanut” sponge clamped in the tip of a hemostat can be placed into the wound, or the blood loss may be accepted while sutures are being placed. For larger holes, a 16F Foley catheter with a 30-mL balloon can be inflated with 10 mL of saline solution.

Immediate repair of valvular damage or acute septal defects rarely is necessary and requires total cardiopulmonary bypass, which has a high mortality in this situation. Most patients who survive to make it to the hospital do well with only external repair. The right coronary artery can be ligated anywhere, but the resulting arrhythmias may be extremely resistant to treatment. The left anterior descending and circumflex arteries cannot be ligated proximally without causing a large infarct.

Lungs Pulmonary injuries requiring operative intervention usually result from penetrating injury. Formerly the entrance and exit wounds were oversewn to control hemorrhage. This allowed for air embolism, which occasionally caused sudden death in the operating room or in the immediate postoperative period. Pulmonary tractotomy has been used to reduce this problem as well as the need for pulmonary resection. Linear stapling devices are inserted directly into the injury tract and positioned to cause the least degree of devascularization Lobectomy or pneumonectomy rarely is necessary. Lobectomy is indicated only for a completely devascularized or destroyed lobe. Parenchymal injuries severe enough to require pneumonectomy rarely are survivable, and major pulmonary hilar injuries necessitating pneumonectomy usually are lethal in the field.

Trachea and Esophagus Injuries of the trachea and esophagus are managed in the same fashion as described earlier for lung injuries. Because exposure can be difficult, provisions should be made to deflate the lung on the operative side by using a double-lumen endotracheal tube. Repair of injuries of the main bronchi and the trachea near the carina tracheae can result in a complete loss of ventilation when the overlying pleura is opened. Gases from the ventilator preferentially escape from the injury, and neither lung will be ventilated.

Descending Thoracic Aorta The occurrence of paraplegia from ischemic injury of the spinal cord has been a concern in injuries to the descending thoracic aorta. Conceptually, two techniques have been advocated. The simpler technique, often referred to as “clamp and sew,” is accomplished with the application of vascular clamps proximal and distal to the injury and repair or replacement of the damaged portion of the aorta. This method results in transient hypoperfusion of the spinal cord distal to the clamps as well as all abdominal organs. If the clamping time is short, less than 30 min, paraplegia is uncommon. An alternative approach is to provide some method for maintaining a reasonable degree of perfusion for organs distal to the clamps. Two techniques have been used to accomplish this goal. The first is with the use of a shunt, a temporary extraanatomic route around the clamps. A heparin-impregnated tube, the Gott shunt, has been designed specifically for this purpose, but the volume of blood flow to the distal aorta is marginal. The second method is to use left heart bypass. With this method, a volume of oxygenated blood is siphoned from the left side of the heart and pumped into the distal aorta. The left superior pulmonary vein, rather than the left atrium, is cannulated to remove blood from the heart because the vein is tougher and less prone to tearing. The left femoral artery is cannulated to return the blood to the distal aorta.

Injuries of the transverse aortic arch do occur from blunt trauma. The proximal clamp usually can be placed between the innominate and left carotid arteries without cerebral infarction. The proximal clamp, however, cannot be placed proximal to the innominate artery. A possible approach to injuries in which the clamps completely exclude the cerebral circulation is to use profound hypothermia and circulatory arrest.

Abdomen

All abdominal explorations in adults are performed using a long midline incision because of its versatility. For children under the age of 6 years, a transverse incision may be advantageous. If the patient has been in shock or is currently unstable, no attempt should be made to control bleeding from the abdominal wall until major sources of hemorrhage have been identified and controlled.

If exsanguinating hemorrhage is encountered on opening the abdomen, it usually is caused by injury to the liver, aorta, inferior vena cava, or iliac vessels. If the liver is the source, the hepatic pedicle should be immediately clamped (a Pringle maneuver) and the liver compressed posteriorly by tightly packing several laparotomy pads between the hepatic injury and the underside of the right anterior chest wall. This combination of maneuvers temporarily controls the hemorrhage from most survivable hepatic injuries.

If exsanguinating hemorrhage originates near the midline in the retroperitoneum, direct manual pressure is applied with a laparotomy pad, and the aorta is exposed at the diaphragmatic hiatus and clamped. The same approach is used in the pelvis except that the infrarenal aorta can be clamped, which is easier and safer because splanchnic and renal ischemia is avoided. Injuries of the iliac vessels pose a particular problem for emergency vascular control. Because there are so many large vessels in proximity, multiple vascular injuries are common. Venous injuries are not controlled with aortic clamping. A helpful maneuver in these instances is pelvic vascular isolation. For stable patients with large midline hematomas, clamping the aorta proximal to the hematoma also is a wise precaution.

Vascular Injuries Injury to the major arteries and veins in the abdomen is a technical challenge to the surgeon and often is fatal. All vessels are susceptible to injury in penetrating trauma. Vascular injuries in blunt trauma are far less common and usually involve the renal arteries and veins, although all other vessels, including the aorta, can be injured. Several vessels are difficult to expose: the retrohepatic vena cava, the suprarenal aorta, the celiac axis, the proximal superior mesenteric artery, the junction of the superior mesenteric, splenic, and portal veins, and the bifurcation of the vena cava. The suprarenal aorta, the celiac axis, and the proximal superior mesenteric and left renal arteries can be exposed by left medial visceral rotation. This is accomplished by incising the left lateral peritoneal reflection beginning at the distal descending colon and extending the incision past the splenic flexure, around the posterior aspect of the spleen, behind the gastric fundus, and ending at the esophagus. This incision permits the left colon, spleen, pancreas, and stomach to be rotated toward the midline. Division of the left crus of the diaphragm permits access to the aorta well above the celiac axis. In contrast, mobilization of the right colon and a Kocher maneuver expose the entire inferior vena cava except the retrohepatic portion, and they are technically simple. These are referred to as a right medial visceral rotation. The kidney can be left in situ or mobilized with the remaining viscera with right and left medial rotations.

The junction of the superior mesenteric, splenic, and portal veins can be exposed in elective surgery by dissecting the vessels from the pancreas, as required when performing a distal splenorenal shunt. In the presence of massive bleeding from a venous injury, this may be impossible. Therefore, the neck of the pancreas is divided without hesitation. This provides excellent exposure of this difficult area.

The bifurcation of the vena cava is obscured by the right common iliac artery. This vessel should be divided to expose extensive vena caval injuries of this area. The artery must be repaired after the venous injury is treated. Amputation occurs in approximately 50 percent of patients in whom the vessels are not repaired.

Liver The lower costal margins impair visualization and a direct approach to the liver. Exposure of the right lobe can be improved by elevating the right costal margin with a large Richardson retractor. The right lobe can be mobilized by dividing the right triangular and coronary ligaments. After division of the right triangular ligament, the dissection is continued medially, dividing the superior and inferior coronary ligaments. The right lobe then can be rotated medially into the surgical field. Mobilization of the left lobe is accomplished in the same fashion. Care must be taken when dividing any of the coronary ligaments because of their proximity to the hepatic veins and the retrohepatic vena cava. It may be necessary to extend the midline abdominal incision into the chest. This is best accomplished with a median sternotomy. The pericardium and diaphragm can be divided toward the center of the inferior vena cava. The combination of incisions provides outstanding exposure of the hepatic veins and retrohepatic vena cava while avoiding injury to the phrenic nerves.

The Pringle maneuver is one of the most useful techniques for evaluating the extent of hepatic injuries. In patients with extensive hepatic injuries, the Pringle maneuver differentiates between hemorrhage from the hepatic artery and portal vein, which ceases when the clamp is applied, and hemorrhage from the hepatic veins and retrohepatic vena cava, which does not. The prefered method is to manually tear the lesser omentum and place the clamp from the left side while guiding the posterior blade of the clamp through the foramen of Winslow with the aid of the left index finger. This approach has the advantage of avoiding injury to the structures within the hepatic pedicle, ensuring that the clamp will be placed properly the first time, and including any anomalous or accessory left hepatic arteries between blades of the clamp. The temporizing hemostatic techniques that have proved most useful are hepatic compression, the Pringle maneuver, and perihepatic packing. Manual compression is best suited for immediate attempts to prevent exsanguination and for periodic control during a complex procedure. Perihepatic packing also is capable of controlling hemorrhage from most hepatic injuries, and it has the advantage of freeing the surgeon's hands. The laparotomy pads, two or three stacked together, should remain folded. The right costal margin is elevated, and the pads are strategically placed over and around the bleeding site. Additional pads should be placed between the liver, diaphragm, and anterior chest wall until the bleeding has been controlled. Ten to fifteen pads may be required to control the hemorrhage from an extensive right lobar injury. Hemorrhage from the left lobe usually can be controlled by mobilizing the lobe and compressing it between the surgeon's hands. Tight packing can compress the inferior vena cava and reduce cardiac filling, and the right diaphragm will be forced cephalad, increasing airway pressure and decreasing tidal volume and functional residual capacity.

Another option for temporary control of hepatic hemorrhage is to use a tourniquet. After mobilization of the bleeding lobe, a 1-in Penrose drain is wrapped around the liver near the anatomic division between the left and right lobes. The drain is cinched until hemorrhage ceases; tension is maintained by placing a clamp on the drain. Tourniquets are difficult to use, however, because they often slip off or even tear through the parenchyma. Special techniques have been developed for controlling hemorrhage from juxtahepatic venous injuries. These formidable procedures include hepatic vascular isolation with clamps, the atriocaval shunt, and the Moore-Pilcher balloon. Hepatic vascular isolation with clamps is accomplished by the application of a Pringle maneuver, clamping the aorta at the diaphragm, and clamping of the suprarenal and suprahepatic vena cava. Although this technique has success in elective procedures, its use in trauma patients has had mixed results because patients in profound hemorrhagic shock do not tolerate the precipitous loss of venous return to the heart.

The atriocaval shunt was designed to achieve hepatic vascular isolation while permitting venous blood to enter the heart from below the diaphragm. Enthusiasm for the shunt has declined because mortality rates with its use range from 50–80 percent.

Numerous methods for the definitive control of hepatic hemorrhage have been developed. Minor lacerations may be controlled with manual compression applied directly to the injury site. For similar injuries that do not respond to compression, topical hemostatic techniques have been successful. Small bleeding vessels may be controlled with electrocautery, although the power output of the machine may have to be increased. Bleeding surfaces immune to electrocautery may respond to the argon beam coagulator. Microcrystalline collagen can be used.

Suturing of the hepatic parenchyma is an effective hemostatic technique. This treatment has been maligned as a cause of hepatic necrosis, but hepatic sutures often are used for persistently bleeding lacerations less than 3 cm in depth. It also is an appropriate alternative for deeper lacerations if the patient will not tolerate further hemorrhage. The preferred suture is 2-0 or 0 chromic attached to a large, curved, blunt needle. The large diameter of the suture helps to prevent it from pulling through Glisson's capsule. A simple running technique is used to approximate the edges of shallow lacerations. Deeper lacerations can be managed with interrupted horizontal mattress sutures placed parallel to the edge of the laceration. When tying the suture, adequate tension exists when visible hemorrhage ceases or the liver blanches around the suture.

Hepatic arterial ligation may be appropriate for patients with recalcitrant arterial hemorrhage from deep within the liver. Its utility is limited because hemorrhage from the portal and hepatic venous systems continues. Its primary role is in transhepatic injuries when application of the Pringle maneuver results in the cessation of arterial hemorrhage.

An uncommon, perplexing hepatic injury is the subcapsular hematoma. This lesion occurs when the parenchyma of the liver is disrupted by blunt trauma, but Glisson's capsule remains intact. Subcapsular hematomas discovered during an exploratory laparotomy that involve less than 50 percent of the surface of the liver and are not expanding or ruptured should be left alone or packed. Hematomas that are expanding during an operation may require exploration. An alternative strategy is to pack the liver to control venous hemorrhage, close the abdomen, and transport the patient to the angiographic suite for hepatic arteriography and embolization of the bleeding vessel. Ruptured hematomas require exploration and selective ligation, with or without packing. Omentum has been used to fill large defects in the liver, with the rationale that it provides an excellent source for macrophages and that it fills a potential dead space with viable tissue.

The complications after significant hepatic trauma include hemorrhage, infection, and various fistulas. Postoperative hemorrhage can be expected in a considerable percentage of patients treated with perihepatic packing. Arteriography with embolization can be considered in selected patients. Infections within and around the liver occur in about 3 percent of injured patients. Perihepatic infections develop more often in victims of penetrating trauma than blunt trauma, presumably because of the greater frequency of enteric contamination of the former.

Gallbladder and Extrahepatic Bile Ducts Injuries of the gallbladder are treated by lateral suture or cholecystectomy, whichever is easier. Injuries of the extrahepatic bile ducts are a challenge. Because of the proximity of the portal vein, hepatic artery, and vena cava, associated vascular injuries are common, and the patient's physiologic status often is poor. These injuries can be treated by the insertion of a T tube through the wound or by lateral suture using 4-0 to 6-0 monofilament absorbable suture. Most transections and any injury associated with significant tissue loss require a Roux-en-Y choledochojejunostomy.

Injuries of the hepatic ducts are almost impossible to repair satisfactorily under emergency circumstances. One approach is to intubate the duct for external drainage and attempt a repair when the patient recovers. Alternatively, the duct can be ligated if the opposite lobe is normal and uninjured. For patients who are critically ill, the common duct also can be treated by intubation with external drainage.

Spleen Splenic injuries are treated by splenic repair (splenorrhaphy), partial splenectomy, resection, or nonoperatively, depending on the extent of the injury and the condition of the patient. Enthusiasm for splenic salvage has been driven by the evolving trend toward nonoperative management of solid organ injuries and the rare but often fatal complication of overwhelming postsplenectomy infection (OPSI).

Partial splenectomy can be used in patients in whom only a portion of the spleen has been destroyed, usually the superior or inferior half. After removal of the damaged portion, the same methods used to control hemorrhage from hepatic parenchyma can be used for the spleen. When placing horizontal mattress sutures across a raw edge, gentle compression of the parenchyma by an assistant facilitates hemostasis. After ligation of the sutures and release of compression, the spleen expands slightly and further tightens the sutures. If splenectomy is performed, vaccines against the encapsulated bacteria are administered. The pneumococcal vaccine is given routinely, and those effective against Haemophilus influenzae and Neisseria meningitidis should be used.

Diaphragm In blunt trauma the diaphragm is injured on the left in 75 percent of cases, presumably because the liver diffuses some of the energy on the right side. For blunt and penetrating trauma, the diagnosis is suggested by an abnormality of the diaphragmatic shadow on chest x-ray. Many of these are subtle, particularly with penetrating injuries, and additional diagnostic evaluation may be warranted. The typical diaphragmatic injury from blunt trauma is a tear in the central tendon that may be large.

Duodenum Duodenal hematomas are caused by a direct blow to the abdomen, and they occur more often in children. Blood accumulates between the seromuscular and submucosal layers, eventually causing obstruction. Most duodenal hematomas in children can be managed nonoperatively with nasogastric suction and parenteral nutrition. If surgical intervention is necessary, evacuation of the hematoma is associated with equal success and fewer complications than bypass procedures.

Duodenal perforations can be caused by blunt and penetrating trauma. Mortality can exceed 30 percent if the lesion is not identified and treated within 24 h. The perforations are not reliably identified by initial oral contrast CT examinations. Most perforations of the duodenum can be treated by primary repair. The wound should be closed in a direction that results in the largest residual lumen.

Challenges arise when there is a substantial loss of duodenal tissue. Extensive injuries of the first portion of the duodenum can be repaired by debridement and anastomosis because of the mobility and rich blood supply of the distal gastric antrum and pylorus. In contrast, the second portion is tethered to the head of the pancreas by its blood supply and the pancreatic and accessory pancreatic ducts (ducts of Wirsung and Santorini) so that the length of duodenum that can be mobilized from the pancreas is limited to approximately 1 cm. As a result, suture repair of the second portion when tissue is lost often results in an unacceptably narrow lumen, and an end-to-end anastomosis is almost impossible, requiring more sophisticated repairs. For extensive injuries proximal to the accessory papilla, debridement and end-to-end anastomosis are appropriate. For lesions between the accessory papilla and the papilla of Vater, a vascularized jejunal graft, either a patch or a tubular interposition graft, may be required. Experience with these procedures is limited. Duodenal injuries with tissue loss distal to the papilla of Vater and proximal to the superior mesenteric vessels are best treated by Roux-en-Y duodenojejunostomy.

Injuries to the third and fourth portions of the duodenum with tissue loss pose other problems. Because of the short mesentery of the third and fourth portions of the duodenum, the risk of ischemia limits mobilization. While end-to-end duodenojejunal anastomoses are possible in these regions, the technique used must resemble that of a hand-sewn low anterior rectal anastomosis. Resection of the third and fourth portions and a duodenojejunostomy on the right side of the superior mesenteric vessels are recommended.

An important adjunct for high-risk or complex duodenal repairs is the pyloric exclusion technique. By occluding the pylorus and performing a gastrojejunostomy, the GI stream can be diverted away from the duodenal repair. If a fistula does develop, it is functionally an end fistula, which is easier to manage and more likely to close than a lateral fistula, and the patient can take food by mouth to maintain nutritional status. A linear staple line across the outside of the pylorus provides the most enduring pyloric closure.

Pancreas Blunt pancreatic transection at the neck of the pancreas can occur with a direct blow to the abdomen. As an isolated injury, it is more difficult to detect than blunt duodenal rupture, but a missed pancreatic injury is more benign. CT will not identify a significant number of transections if performed within 6 h of injury.

Optimal management of pancreatic trauma is determined by the location of the injury and whether or not the main pancreatic duct is injured. Pancreatic injuries in which the pancreatic duct is not injured may be treated by drainage or left alone. In contrast, pancreatic injuries associated with a ductal injury always require treatment to prevent pancreatic ascites or a major external fistula.

No ideal method exists for identifying pancreatic ductal injuries that cannot be ruled out by direct exploration. This dilemma tends to encourage aggressive local exploration, which may create a ductal injury where none existed. For injuries involving the neck, body, or tail of the pancreas, this is of minor consequence because a simple resection distal to the injury cures the lesion. This is not the case for injuries to the head of the pancreas, which cannot be treated with a simple resection. Rather than accepting the risks of pancreatography or aggressive local exploration, an option for identifying ductal injuries in the head of the pancreas is to do nothing other than drain the pancreas. If a pancreatic fistula or pseudocyst develops, the diagnosis is confirmed. The majority of pancreatic fistulas close spontaneously with only supportive care. This is the preferred approach to operative pancreatography when the diagnosis of ductal injury in the head of the pancreas is not apparent and endoscopic retrograde pancreatography (ERP) is not promptly available.

Several options are available for treating injuries of the neck, body, and tail of the pancreas when the main duct is transected. Distal pancreatectomy with splenectomy has been the preferred approach, but increasing interest in splenic preservation has stimulated the use of the splenic-preserving distal pancreatectomy.

For injuries to the head of the pancreas that involve the main pancreatic duct but not the intrapancreatic bile duct, there are few options. A more limited resection from the site of the injury to the neck of the pancreas, with preservation of the pancreaticoduodenal vessels and common duct, allows closure of the injured proximal pancreatic duct. Pancreatic function can then be preserved by a Roux-en-Y pancreatojejunostomy with the distal pancreas.

In contrast to injuries of the pancreatic duct, diagnosis of injuries to the intrapancreatic common bile duct is simple. The first method is to squeeze the gallbladder and observe the pancreatic wound. Small tangential perforations of the intrapancreatic bile duct may heal with simple drainage, but it is seldom recommended. Most authorities advocate division of the common bile duct superior to the first portion of the duodenum, ligation of the distal common duct, and reconstruction with a Roux-en-Y choledochojejunostomy.

Pancreaticoduodenal Injuries Because the pancreas and duodenum are in physical contact, combined pancreaticoduodenal injuries are not uncommon, particularly in penetrating trauma. These lesions are dangerous because of the risk of duodenal suture line dehiscence and the development of a lateral duodenal fistula. The simplest treatment is to repair the duodenal injury and drain the pancreatic injury. This method is appropriate for combined injuries without major duodenal tissue loss and without pancreatic or biliary ductal injuries. With more extensive injuries, consideration should be given to providing additional protection for the duodenal suture line. Pyloric exclusion is preferred to other alternatives.

While most pancreatic and duodenal injuries can be treated with relatively simple procedures, a few require extensive operations, such as pancreatoduodenectomy. Examples of such injuries include transection of the intrapancreatic bile duct and the main pancreatic duct in the head of the pancreas, avulsion of the papilla of Vater from the duodenum, and destruction of the entire second portion of the duodenum. Most injuries of that nature are caused by higher-energy gunshot wounds. In patients with a pancreaticoduodenal injury who also have an intrapancreatic bile duct injury, it is possible to use the combination of a pyloric exclusion and Roux-en-Y choledochojejunostomy to avoid a pancreatoduodenectomy.

Colon There are three conceptually different methods for treating colonic injuries: primary repair, colostomy, and exteriorized repair. Primary repairs include lateral suture of perforations and resection of the damaged colon with reconstruction by ileocolostomy or colocolostomy. The advantage of primary repairs is that definitive treatment is performed at the initial operation.

The advantage of colostomy is that it avoids an unprotected suture line in the abdomen. The disadvantage is that a second operation is required to close the colostomy. Often overlooked disadvantages are the complications associated with the creation of a colostomy, some of which may be fatal. Numerous large, retrospective and several prospective studies have demonstrated that primary repair is safe and effective in most patients with penetrating injuries. One approach is to repair all injuries regardless of the extent and location (including colocolostomy) and reserve colostomy for patients with protracted shock and extensive contamination. Systemic factors are more important than local factors in determining whether a suture line heals.

Complications related to the colonic injury and its treatment may include intraabdominal abscess, fecal fistula, wound infection, and stomal complications. Intraabdominal abscess occurs in approximately 10 percent of patients, and most are managed with percutaneous drainage. Fistulas occur in 1–3 percent of patients. Stomal complications include necrosis, stenosis, obstruction, and prolapse. Taken together, they occur in approximately 5 percent of patients, and most require reoperation. Necrosis is a serious complication that must be recognized and treated promptly. Failure to do so can result in life-threatening septic complications, including necrotizing fasciitis.

Rectum Rectal injuries are similar to colonic injuries with respect to the ecology of the luminal contents, the structures and blood supply of the wall, and the nature and frequency of complications. They differ in two important ways: mechanisms of injury and accessibility.

The diagnosis is suggested by the course of projectiles, the presence of blood on digital examination of the rectum, and history. Patients in whom a rectal injury is suspected should undergo proctoscopy. Hematomas, contusions, lacerations, and gross blood may be seen. If the diagnosis is in question, x-ray examinations with soluble contrast medium enemas are indicated.

Injuries of the intraperitoneal portion (including its posterior aspect) are treated as previously outlined in the section on colonic injuries. Access to extraperitoneal injuries is so restricted, especially in the narrow male pelvis, that indirect treatment usually is required. While colostomies proximal to a suture line are avoided in patients with colonic injuries, there is often no option in patients with extraperitoneal injuries; sigmoid colostomies are appropriate for most patients. Properly constructed loop colostomies are preferred because they are quick and easy to fashion. If a perforation is inadvertently uncovered during dissection, it should be repaired as described previously. Otherwise, it is not necessary to explore the extraperitoneal rectum to repair perforation. It may be extremely difficult or impossible to accomplish exploration.

Extraperitoneal injuries of the rectum should be drained via a retroanal incision. There have been reports of treating small extraperitoneal rectal injuries by suture or drainage alone. The outcomes have been acceptable, and colostomies have been avoided. There is insufficient experience to recommend this approach because pelvic sepsis associated with rectal injury is highly lethal.

Stomach and Small Intestine Injuries of the stomach and small bowel pose no special problems. Gastric injuries can be missed occasionally if a wound is located within the mesentery of the lesser curvature or high in the posterior fundus. A running two-layer suture line is preferred for the stomach because of its rich blood supply and because postoperative hemorrhage has occurred when the single-layer technique has been used in the stomach.

Wounds of the mesenteric border can be missed if the exploration is not comprehensive. Most injuries are treated with a lateral single-layer running suture. Multiple penetrating injuries often occur close together. Rather than performing many lateral repairs, judicious resections with end-to-end anastomoses can save considerable time.

Kidneys Three imaging techniques—CT, intravenous pyelography (IVP), and arteriography—can be used to evaluate accurately the extent of renal injury. Almost 95 percent of all blunt renal injuries are treated nonoperatively. The diagnosis is suspected by the finding of microscopic or gross hematuria and confirmed by CT or IVP. Most cases of urinary extravasation and hematuria resolve in a few days with bed rest. Persistent gross hematuria can be treated by embolization. Persistent urinomas can be drained percutaneously. If a perinephric hematoma is encountered during laparotomy from blunt trauma, exploration is indicated if it is expanding or pulsatile.

Hemostatic and reconstructive techniques used to treat blunt renal injuries are similar to those used to treat the liver and spleen. The collecting system should be closed separately and the renal capsule preserved to close over the repair of the collecting system. Permanent sutures should be avoided because of the risk of calculus formation. We prefer absorbable monofilament sutures because of their lack of abrasiveness.

The renal arteries and veins are uniquely susceptible to traction injury caused by blunt trauma. As the artery is stretched, the inelastic intima and media may rupture. This causes thrombus formation, resulting in high-grade stenosis or thrombosis. The injury can be detected by CT, IVP, or duplex scanning. If the patient does not have more urgent injuries and treatment and repair can be accomplished within 3 h of admission, it should be attempted.

Ureters Injuries of the ureters from external trauma are rare. They occur in a few patients with pelvic fractures and are uncommon in penetrating trauma because the silhouette they present is small. The diagnosis in blunt trauma may be made by CT, IVP, or retrograde ureterography. If an injury is suspected but not identified, methylene blue or indigo carmine is administered intravenously. Staining of the tissue adjacent to the injury can facilitate identification of the injury site. Most injuries can be repaired primarily using the same technique as that described earlier for small arteries, using 5-0 absorbable monofilament suture. When the ureter is mobilized, the dissection should be at least 1 cm lateral and medial to the ureter to avoid injury to its delicate vascular plexus.

Bladder Bladder injuries are diagnosed by cystography, CT, or during laparotomy. A postvoid view enhances the accuracy of cystography. Blunt ruptures of the intraperitoneal portion are closed with a running single-layer closure using 3-0 absorbable monofilament suture. Blunt extraperitoneal rupture is treated with a Foley catheter; direct operative repair is not necessary. Penetrating bladder injuries are treated in the same fashion, although injuries near the trigone should be repaired through an incision in the dome so that iatrogenic injury to the intravesicular ureter is avoided by direct visualization.

Urethra Blunt disruption of the posterior urethra is managed by bridging the defect with a Foley catheter. This usually requires passing catheters through the urethral meatus and through an incision in the bladder. Once the catheter bridges the defect, healing occurs as the intervening hematoma resorbs. Strictures are not uncommon but can be managed electively. Penetrating injuries are treated by direct repair.

Gynecologic Injuries Occasionally, the vagina is lacerated by a sharp bone fragment from a pelvic fracture. The usual hemostatic techniques are used to control bleeding, and suture repair is used to close defects that communicate with a lumen. Transection at the injury site with proximal ligation and distal salpingectomy is a more prudent approach.

Trauma in pregnancy also is rare. Blunt trauma can cause uterine rupture, which almost always results in fetal demise. The outcome of penetrating uterine injuries is more variable and depends on penetration of the uterine cavity, damage to the placenta, and fetal injury.

Pelvis

Pelvic fractures can cause exsanguinating retroperitoneal hemorrhage without associated major vascular injury; branches of the internal iliac vessels and the lower lumbar arteries often are responsible. Hemorrhage also comes from small veins and from the cancellous portion of the fractured bones. A direct surgical approach rarely is effective because many of the sources of hemorrhage are outside the surgical field.

Several methods have been used to control hemorrhage associated with pelvic fractures. These include immediate external fixation, medical antishock trousers (MAST), angiography with embolization, and pelvic packing. No single technique is effective for treating all fractures, and there is little agreement among specialists as to which should be used. Anterior external fixation is not intended to provide definitive fracture stabilization in most instances. It is intended to decrease pelvic volume, to tamponade bleeding, and to prevent secondary hemorrhage that may occur if the fractured bones shift. Antishock trousers can provide some stability for the fracture and probably tamponade venous hemorrhage. Disadvantages are the loss of access to the abdomen and the risk of lower extremity compartment syndrome. Angiography with embolization is effective for controlling arterial hemorrhage.

Another challenge is the open pelvic fracture. In many instances the wounds are located in the perineum, and the risk of pelvic sepsis and osteomyelitis is high. To reduce the risk of infection, a sigmoid colostomy is recommended. The pelvic wound is manually debrided and irrigated daily with a high-pressure pulsatile irrigation system until granulation tissue covers the wound. The wound is then left to heal by secondary intention. This approach has been highly successful (Fig. 6-2).



FIGURE 6-2 Algorithm for the management of mechanically unstable pelvic fractures in hemodynamically unstable patients.



Extremities

Vascular Injuries with Fractures Vascular injuries associated with fractures are rare and also are more severe than isolated vascular injuries or fractures, and amputation rates of more than 50 percent have been noted. These injuries can be caused by blunt and penetrating trauma. Particular fractures and dislocations are more likely to be associated with vascular injury than others. In the upper extremity, a fracture of the clavicle or the first rib may lacerate the distal subclavian artery. The axillary artery may be injured in patients with dislocations of the shoulder or proximal humeral fractures. Supracondylar fractures of the distal humerus and dislocations of the elbow are known for their association with brachial artery injuries. In all these fractures and dislocations, vascular injuries are uncommon and occur in only a small fraction of patients.

In the lower extremity, the orthopaedic injury most commonly associated with vascular injury is dislocation of the knee, in which the popliteal artery or vein may be injured in as many as 30 percent of patients. The popliteal vessels also may be injured in patients with supracondylar fractures of the femur or tibial plateau fractures. Vascular injury can occur in patients with combined fractures of the tibia and fibula.

Compartment Syndrome A compartment syndrome can occur anywhere in the extremities, including the thighs, buttocks, arms, and hands. The pathophysiology is an acute increase in pressure in a closed space that impairs blood flow to the structures within. The causes of extremity compartment syndrome include arterial hemorrhage into a compartment, venous ligation or thrombosis, crush injuries, infections, crotalid envenomation, and ischemia/reperfusion. In conscious patients, pain is the prominent symptom.

Treatment consists of measures to reduce compartment pressure, including elevation of the extremity, evacuation of hematomas, and fasciotomy. The evacuation of hematomas as a consequence of arterial injury almost always results in a fasciotomy because the compartment must be opened to treat the vascular injury. Note that the soleus muscle must be detached from the tibia to decompress the deep flexor compartment.

Prognosis is related to the severity, duration, and cause of the compartment syndrome. The best results are obtained in patients with arterial hemorrhage and venous ligation or thrombosis who undergo early fasciotomy. Those who develop compartment syndrome from crush injuries, crotalid envenomation, and particularly ischemia/reperfusion have a poor prognosis because of the preexisting muscle and nerve damage caused by the original insult. Fasciotomy should be attempted, although infection and amputation are a frequent outcome.

BITES AND STINGS OF ANIMALS AND INSECTS

Rabies

Circumstances surrounding the attack frequently furnish vital information as to whether or not vaccination is indicated. Most domestic animal bites are provoked attacks; if this history is obtained, rabies vaccine usually can be withheld if the animal appears healthy. Bites during attempts to feed or handle an apparently healthy animal are generally regarded as provoked. Postexposure prophylaxis combining local wound treatment, passive immunization, and vaccination is over 90 percent effective when applied appropriately.

Clinical signs of rabies in wild animals cannot be interpreted reliably; therefore, any wild animal that bites or scratches a person should be killed at once (without unnecessary damage to the head) and the brain examined for evidence of rabies. It is accepted that the incubation period for rabies in human beings ranges from 10 days to 1 year, with most cases occurring within 20–90 days of exposure. In cases of exposure of the head, neck, or upper extremities, the incubation period is potentially less than 30 days.

Postexposure prophylaxis in addition to local wound treatment consists of human rabies immune globulin (HRIG) (Imogam Rabies) and vaccine (Table 6-5). There are two rabies vaccines available in the United States: human diploid cell rabies vaccine (HDCV) or rabies vaccine adsorbed (RVA) (Imovax). Either is administered in conjunction with HRIG at the beginning of postexposure therapy. A regimen of five 1-mL doses of HDCV or RVA is given intramuscularly.



TABLE 6-5 RABIES POSTEXPOSURE PROPHYLAXIS SCHEDULE, UNITED STATES, 1991



HRIG is administered only once to provide immediate antibodies until the patient responds to the vaccine by actively producing antibodies. If HRIG was not given when vaccination was begun, it can be given through the seventh day after administration of the first dose of vaccine.

Snakes

In North America, all the poisonous snakes of medical importance are pit vipers, of the family Crotalidae, and the coral snake, of the family Elapidae. The pit vipers include the rattlesnake, the cottonmouth moccasin, and the copperhead. Over 98 percent of bites occur on the extremities. Rattlesnakes are responsible for approximately 70 percent of deaths from snakebites, whereas death from the bite of a copperhead is extremely rare.

The venoms of poisonous snakes consist of enzymatic complex proteins that affect all soft tissues. Venoms have been shown to have neurotoxic, hemorrhagic, thrombogenic, hemolytic, cytotoxic, antifibrinolytic, and anticoagulant effects. Most venoms contain hyaluronidase, which enhances the rapid spread of venom by way of the superficial lymphatics.

Pain from the bite of a pit viper is excruciating, and probably the symptom that most easily differentiates poisonous from nonpoisonous snakebites. Pit vipers characteristically produce one or two fang marks. Hypotension, weakness, sweating and chills, dizziness, nausea, and vomiting are other systemic symptoms. Symptoms can include swelling, tenderness, pain, and ecchymosis and may appear within minutes at the site of venom injection. If no edema or pain is present within 30 min after injury, the snake probably did not inject any venom. Swelling may continue to increase for 24 h.

The venom from rattlesnakes produces deleterious changes in the blood cells, defects in blood coagulation, injuries to the intimal linings of vessels, damage to the heart muscle, alterations in respiration, and to a lesser extent, changes in neuromuscular conduction. Pulmonary edema is common in severe poisoning, and hemorrhage into the lungs, kidneys, heart, and peritoneum can occur.

Blood should be drawn immediately for typing and crossmatching because hemolysis may later make this difficult. Because hemolysis and injury to kidneys and liver may occur, it is important to follow alterations in clotting mechanism, renal and liver function, and electrolyte status.

Management of Snake Bites Application of a tourniquet, incision, and suction are appropriate if used within 1 h of the time of the bite. The snake injects venom into the subcutaneous tissue, which is absorbed by capillaries and lymphatics. The tourniquet should be applied loosely to obstruct only venous and lymphatic flow. The tourniquet is not released once applied and may be left in place during the 30 min that suction is applied. The tourniquet may be removed after definitive treatment has been instituted and the patient is not in shock.

Incision and suction for 30 min may be beneficial if accomplished within 30 min after snakebite. The incision should be longitudinal and not cruciate. When two fang marks are seen, the depth of the venom injection is generally considered to be one-third of the distance between the fang marks.

The average snakebite does not require surgical excision. This procedure is reserved for the most severe envenomations. The most important treatment for a snakebite is antivenin, although many patients do not require it. Copperhead envenomation rarely necessitates antivenin. Most snakebite fatalities in the United States during the past 20 years have involved either delay in obtaining treatment, no antivenin treatment, or inadequate dosage. Because antivenin contains horse serum, before its administration, skin testing is required. Epinephrine 1:1000 in a syringe should be available before antivenin is given. Physicians confronted with this situation may obtain advice from the local poison center or the Antivenin Index Center of the Oklahoma Poison Information Center, Oklahoma City, Oklahoma (405–271–5454).

Antivenin should be withheld until a physician can determine whether it is indicated. Approximately 30 percent of all poisonous snakebites in the United States result in no envenomation. The indication for antivenin is governed by the degree of envenomation. With frequent observations using the classification presented in Table 6-6, the severity of the bite is often found to increase with time, and therefore, a change in grade is observed. Most bites will have reached a final staging within 12 h.



TABLE 6-6 GRADING OF CROTALID ENVENOMATION



Stinging Insects and Animals

HYMENOPTERA

The most important insects that produce serious and possibly fatal anaphylactic reactions are arthropods of the order Hymenoptera. This group includes the honeybee, bumblebee, wasp, yellow and black hornet, and the fire ant. The venom of these stinging insects is just as potent as that of snakes and causes more deaths in the United States yearly than are caused by snakebites.

Symptoms are one or more of the following: localized pain, swelling, generalized erythema, a feeling of intense heat throughout the body, headache, blurred vision, injected conjunctivae, swollen and tender joints, itching, apprehension, urticaria, petechial hemorrhages of the skin and mucous membranes, dizziness, weakness, sweating, severe nausea, abdominal cramps, dyspnea, constriction of the chest, asthma, angioneurotic edema, vascular collapse, and possible death from anaphylaxis. Fatal cases may manifest glottal and laryngeal edema, pulmonary and cerebral edema, visceral congestion, meningeal hyperemia, and intraventricular hemorrhage. Death results from a combination of shock, respiratory failure, and central nervous system changes. Most deaths from insect stings occur within 15–30 min.

STINGRAYS

Approximately 750 persons each year are stung by stingrays. As the spine, which is curved and has serrated edges, enters the flesh, the sheath surrounding the spine ruptures, and venom is released. As the spine is withdrawn, fragments of the sheath may remain in the wound. The wound edges are often jagged and bleed freely. Pain usually is immediate and severe, increasing to maximum intensity in 1–2 h and lasting for 12–48 h. Treatment consists of copious irrigation with water to wash out any toxin and fragments of the spine's integumentary sheath. Venom is inactivated when exposed to heat. The area of the bite should be placed in water as hot as the patient can stand without injury for 30 min to 1 h. After soaking, the wound may be further debrided and treated appropriately.

PORTUGUESE MAN-OF-WAR

After a severe sting by a Portuguese man-of-war, there may be almost immediate severe nausea, gastric cramping, and constriction and tightness of throat and chest with severe muscle spasm. There is intense, burning pain with weakness and perhaps respiratory distress. The most important emergency treatment is to inactivate the nematocysts immediately to prevent their continuous firing of toxins. This is accomplished by applications of a substance of high alcohol content, such as rubbing alcohol, followed by application of a drying agent, such as flour, baking soda, talc, or shaving cream. The tentacles may then be removed by shaving. An alkaline agent such as baking soda is then applied in order to neutralize the toxins, which are acidic. Demerol and Benadryl may dramatically relieve the pain and symptoms. Aerosol corticosteroid-analgesic balm is helpful.

SPIDERS

Black Widow Spider The most common biting spider in the United States is the black widow (Latrodectus mactans). The female spider has a reddish orange hourglass-shaped marking on its ventral surface. L. mactans venom is primarily neurotoxic in action and centers on the spinal cord. After a bite by the black widow spider, the majority of patients experience pain within 30 min, and a small wheal with an area of erythema appears. Nausea and vomiting occur in approximately one-third of patients, headache in one-fourth, and dyspnea may develop. The time of onset of symptoms after the bite is 30 min to 6 h. The severe symptoms last from 24–48 h. Generalized muscle spasm is the most prominent physical finding. Cramping muscle spasms occur in the thighs, lumbar region, abdomen, or thorax. Priapism and ejaculation have been reported. Most patients recover within 24 h. Treatment consists of narcotics for the relief of pain and a muscle relaxant for relief of spasm. Methocarbamol (Robaxin) or 10 mL of a 10% solution of calcium gluconate relieves the symptoms. It is believed that calcium acts by depressing the threshold for depolarization at the neuromuscular junctions. Calcium gluconate may give instant relief of muscular pain, and methocarbamol can be administered intravenously 10 mL over a 5-min period, with a second ampule started in a saline solution drip. Although L. mactans antivenin is available, it rarely is required.

Brown Recluse Spider The distinguishing mark of the Loxosceles reclusa is the darker violin-shaped band over the dorsal cephalothorax. The spider is native to the south central United States. The body ranges from 7–12 mm; including the legs, the spider's size ranges from 2–3 cm.

The initial bite may go unnoticed or be accompanied by a mild stinging sensation. Pain may recur 6–8 h afterward. A mild envenomation is associated with local urticaria and erythema that usually resolve spontaneously. More severe bites result in progression to necrosis and sloughing of skin with residual ulcer formation. A generalized macular and erythematous rash may appear in 12–24 h. Erythema develops, with bleb or blister formation surrounded by an irregular area of ischemia. A zone of hemorrhage and induration and a surrounding halo of erythema may develop peripherally. The central ischemia turns dark, and eschar forms by day 7; by day 14, the area sloughs, leaving an open ulcer. Approximately 3 weeks is required for the lesion to heal. The pain may be out of proportion with the size of the area involved. The progression from blue to black gives the bite a necrotic appearance, and the more severe bites develop within a few hours to 2 days.

Treatment is conservative because of the difficulty in predicting the severity of the bite. Various treatments have been advocated in addition to early excision, including treatment with corticosteroids, heparin, phentolamine, dextran, and infusion, but clinical studies have failed to identify the benefit of these agents. A leukocyte inhibitor, dapsone (used in leprosy), is effective in reducing inflammation at the site of the brown recluse venom injection. Treatment with dapsone is 100 mg daily for 14 days before surgical excision, if required.

SCORPIONS

Of the numerous species of scorpions in the United States, only one, Centruroides exilicauda, or the bark scorpion, is medically significant. It is found primarily in the desert Southwest. Ranging in length from 1–7 cm, it usually is yellowish brown in color and may have vertical bands on its dorsum. A tubercle at the base of the stinger distinguishes the bark scorpion from other species. The venom is neurotoxic and causes the release of neurotransmitters from the autonomic nervous system and the adrenal glands. The sting causes intense pain with few other local symptoms. Hyperesthesia persists at the site so that a light tap will reproduce the intense pain. The tap test reinforces the diagnosis. In addition to pain, other symptoms reflect the neurotoxic nature of the venom, including anxiety, blurred vision or temporary blindness, wandering eye movements, dyspnea, wheezing, dysphagia, involuntary urination and defecation, and opisthotonos. Somatic muscular contractions resembling seizures, hypertension, supraventricular tachyarrhythmias, and fever also are seen. These stings have been of little significance in adults and are satisfactorily treated with cold compresses. Conversely, infants and small children have died from scorpion envenomation, although not since 1968. Small children with signs of envenomation should be admitted to the hospital and monitored.

For a more detailed discussion, see Burch JM, Franciose RJ, and Moore EE: Trauma, chap. 6 in Principles of Surgery, 7th ed.

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Copyright © 1998 McGraw-Hill
Seymour I. Schwartz
Principles of Surgery Companion Handbook