45. | Principles of Surgery, Companion Handbook

Chapter 44 Minimally Invasive Surgery

Principles of Surgery Companion Handbook

CHAPTER

44
MINIMALLY INVASIVE SURGERY

Physiology
General Principles of Access
Imaging Systems
Energy Sources
Balloons and Stents
Instrumentation
Room Setup
Minimally Invasive Surgical Procedures

PHYSIOLOGY

Laparoscopy The pneumoperitoneum required for laparoscopic surgery deserves special physiologic considerations. CO₂ is used because it is not combustible and it is rapidly absorbed. Absorption of this can create a respiratory acidosis once body buffers are exhausted. With normal respiratory function, increases in minute ventilation can easily compensate. Pressure effects from insufflation also are important. Reverse Trendelenburg position, combined with inferior vena cava compression by insufflation, can cause loss of venous return from the lower half of the body, most significant in the hypovolemic patient. Most common arrhythmia is bradycardia, vagally induced. This is managed with atropine and desulfation. Decreased lower extremity venous return also increases risk of deep venous thrombosis (DVT) and pulmonary embolism (PE). Subcutaneous heparin and sequential compression stockings usually are preventive. Increased intraperitoneal pressures also (1) is transmitted to the thoracic cavity and (2) decreases renal blood flow. Other consequences include gas embolus, which should be suspected when sudden hypotension develops during insufflation. Treat with head-down, left lateral decubitus position and central venous pressure (CVP) catheter to aspirate air from the right ventricle.

Alternatives to insufflation include bulky, difficult-to-use abdominal wall lift devices. The stress hormone response to laparoscopic surgery is very similar to that of open surgery except that there is more rapid normalization after operation.

Thoracoscopy This is different from laparoscopy because it is not necessary to use insufflation because of the bony thorax. However, double-lumen endotracheal tubes are needed to collapse the lung on the operative side.

Other Procedures Extracavitary insufflation can cause subcutaneous emphysema with carbon dioxide and metabolic acidosis.

Anesthetic Management Most important are carbon dioxide ventilation and rapid venous return at the end of the procedure when the pneumoperitoneum is released and the patient is laid flat. Little intravenous fluid should be used during the operation.

GENERAL PRINCIPLES OF ACCESS

Thoracoscopic access is similar to a chest tube. Trocars are inserted over the top of a rib. The lung is collapsed with a double-lumen endotracheal tube. Insufflation is unnecessary.

Laparoscopic access requires maintenance of a pneumoperitoneum. This may be begun by direct puncture (Veress needle) or direct peritoneal access technique (Hasson, cutdown). Both require a pressure-limited carbon dioxide insufflator to maintain a pressure of 15 mmHg. The latter access method is used in patients who have had previous abdominal surgery and adhesions. Additional trocars are then placed under direct vision using the first trocar. Lower abdominal trocar sites 10 mm and larger must be closed to prevent herniation.

For retroperitoneal procedures, balloon dissection of this anatomic space is accomplished through a Hasson trocar. Pressures should not go above 10 mmHg for the subsequent insufflation. Subcutaneous access (i.e., saphenous vein harvesting) uses 5-mm scopes with lighted holding retractors. Gas insufflation can cause subcutaneous emphysema.

IMAGING SYSTEMS

Flexible endoscopy uses CCD camera chips on the end of flexible endoscopes. Laparoscopy and thoracoscopy use rigid telescopes with a camera head attached to the external end. The scope lens may be flat (0 degrees) for a head on view or angled (30 degrees) for a wider field and a top-down or side-in view. Cameras may be single-chip or three-chip. Three-chip cameras have separate red, green, and blue CCDs (RGB), with the greatest resolution and color fidelity. Laparoscopic imaging is limited to two dimensions. Three-dimensional systems that add depth of field are being developed but are not in practical use yet.

ENERGY SOURCES

Most common is radiofrequency (RF) electrosurgical for coagulation and desiccation, either by monopolar or bipolar delivery. Argon beam coagulation also is available. This uses an ionized argon gas jet. It is good for diffusely bleeding surfaces. The abdomen must be vented during laparoscopic argon beam use! Lasers also are used, less so for laparoscopic procedures than for endoscopic procedures. Ultrasonic energy is being used for coagulation and division of small blood vessels (harmonic scalpel or laparoscopic coagulation shears) with a minimal amount of lateral damage. It is good for short gastric division during fundoplications.

BALLOONS AND STENTS

Endoluminal balloons are used during endoscopic procedures to dilate strictures. Once dilatation is accomplished, stenting is used to maintain patency. Stents are plastic or expandable metal. Metal stents have tissue ingrowth that may cause future obstruction.

INSTRUMENTATION

Most instruments replicate standard instruments but are 20–45 cm (standard 30 cm) long and 3–10 mm (standard 5 mm) wide. Cautery often is incorporated into instruments. Unique laparoscopic instruments have been designed, such as the electrocautery hook.

ROOM SETUP

For upper abdominal procedures, two video units, one at each upper corner of the field, are used. For pelvic procedures, the video monitor is placed at the patient's foot with the surgeon facing that end. The ideal trocar placement is procedure-dependent but should form an equilateral triangle between the surgeon's hands and the laparoscope, with the hand trocars at least 10 cm apart.

MINIMALLY INVASIVE SURGICAL PROCEDURES

Laparoscopic Cholecystectomy “Lap chole” revolutionized general surgical laparoscopy. It greatly reduced length of stay and recovery time from this common operation. The most important operative point is lateral retraction of the infundibulum and cephalic retraction of the fundus to “open up” the triangle of Calot to provide optimal visualization and minimize bile duct injury.

Laparoscopic Appendectomy This is useful in patients with right-sided pelvic pain of uncertain etiology; it is also useful in obese patients. The appendix is removed based on standard surgical principals (as in open technique). This requires three ports: (1) camera, (2) suprapubic for retraction, and (3) left lower quadrant for dissection and endo-GIA division of the appendiceal base and mesentery.

Inguinal Hernia Repair This is the most controversial minimally invasive procedure. The transperitoneal mesh onlay approach has all but been abandoned. Approaches today are: (1) TAPP, or transabdominal preperitoneal, and (2) TEP, or totally extra-peritoneal. The TEP repair is preferred, especially for recurrent hernias. Bilateral hernias also are a good indication. Overall, the recurrence rate is approximately 5 percent. The procedure uses three trocars. A balloon is used to open the space anterior to the posterior rectus sheath. This opens Hesselbach's triangle posteriorly. The cord is then dissected free from the sac. The sac is ligated, and a 10 × 15 cm mesh is affixed to Cooper's ligament, the public tubercle, the posterior rectus muscle, and laterally to the transversalis fascia.

Fundoplication Antireflux surgery has been demonstrated to be superior to medical therapy for the treatment of severe gastroesophageal reflux disease (GERD), and the laparoscopic approach provides the same results as the open technique. Workup should include endoscopy and biopsy of esophagitis, 24-h pH probe, barium swallow, and esophageal motility studies. Gastric emptying should be studied in diabetes. For those with diminished esophageal motility, a partial wrap (Toupet) should be performed instead of a full wrap (Nissen). For trocar placement, see Fig. 44-1.

FIGURE 44-1 Laparoscopic Nissen fundoplication, with the “baseball diamond” positions of trocar, target, monitor, and surgeon (X = location of gastroesophageal junction; S = location of surgeon). (From Hunter JG: Advanced laprascopic surgery. Am J. Surg 173:14–18, 1977, with permission.)

Laparoscopic Assisted Colectomy Indications are benign or premalignant diseases of the colon. The use of laparoscopy for malignant disease of the colon is being evaluated under a prospective, randomized protocol to assess the true incidence of trocar site malignant implantation, which seems to be twice that of the open technique.

Splenectomy Most common indication is idiopathic thrombocytopenic purpura (ITP). This should be limited to spleens less than 500 g. The patient is placed in the left lateral decubitus position with the spleen “hanging.” Major vessels are controlled with individual ligation or a linear stapler. Short gastrics are divided in a similar fashion or with the harmonic scalpel. Finally, the spleen is placed in a retrieval bag, morcellated, and removed through the neck of the bag, avoiding any spillage.

For a more detailed discussion, see Hunter JG: Minimally Invasive Surgery, chap. 44 in Principles of Surgery, 7th ed.