18 - Video-Assisted Thoracic Surgery as a Diagnostic Tool
Editors: Shields, Thomas W.; LoCicero, Joseph; Ponn, Ronald B.; Rusch, Valerie W.
Title: General Thoracic Surgery, 6th Edition
Copyright 2005 Lippincott Williams & Wilkins
> Table of Contents > Volume I - The Lung, Pleura, Diaphragm, and Chest Wall > Section VI - Anesthetic Management of the General Thoracic Surgical Patient > Chapter 23 - The Shared Airway: Management of the Patient with Airway Pathology
Chapter 23
The Shared Airway: Management of the Patient with Airway Pathology
Anne C. Kolker
The patient with airway pathology presents a challenge to the surgeon and anesthesiologist. A coordinated approach to evaluating and securing the airway and ultimately treating the underlying problem is critical. Both surgeon and anesthesiologist must have a coherent plan for airway management including alternatives in cases of difficulty or failure of the initial plan. The patient's symptoms may range from mild hoarseness to acute dyspnea and agitation, depending on the location, size, and type of lesion. Preoperative evaluation, when possible, helps to define the area and type of the lesion. Appropriate radiologic studies and laboratory tests are valuable. Planning for both the surgical procedure and the conduct of anesthesia is crucial because airway control and the ability to ventilate may be severely limited. Both the surgeon and anesthesiologist require knowledge of various possible approaches and treatments to complex airway problems, particularly in instances in which they must share airway control during manipulation, treatment, or repair of various anatomic problems related to airway patency. Preoperative planning requires a well-organized approach to the various options available for surgery and anesthesia so that the patient receives adequate anesthesia as well as surgical repair.
CAUSES AND PRESENTATION OF PATIENTS WITH AIRWAY PATHOLOGY
The underlying airway pathology has many etiologies (Table 23-1). Airway obstruction may be due to intrinsic lesions, including tumors, strictures, and foreign bodies. Extrinsic compression can arise from a range of benign or malignant conditions that result in mediastinal pathology as well as lung or esophageal tumors. Airway disruption can be due to trauma or iatrogenic injury associated with airway manipulation and evaluation. Planned surgery requiring tracheal resection or bronchial sleeve may involve airway disruption during the resection. Prior surgery, tumor, or infection may result in fistulae that evolve over time and are usually small disruptions connecting with a chest cavity or the esophagus. Hemoptysis may be associated with any lesion that connects to the airway.
Intrinsic Lesions
Internal obstruction is most commonly associated with tumors that can be found at all levels of the trachea and bronchi. These may be primary lung tumors, metastatic lesions, or local invasion from the esophagus or mediastinal areas. Strictures can be associated with several types of preexisting lesions. They can arise from pulmonary tuberculosis, as stated by Wan and colleagues (2002), or from other infectious etiologies, including diphtheria, syphilis, and typhoid. Chronic inflammatory conditions can result in tracheal stenosis. Fibrosing mediastinitis and systemic diseases such as Wegener's granulomatosis or amyloidosis can produce benign strictures. Tracheostomy sites can develop granulation tissue that can mimic a mass or that eventually becomes a stricture. Airway burns can develop strictures over time. Prior airway surgery, including tracheal or sleeve resections and lung transplantation, may stricture at an anastomotic, site as reported by Sonett and associates (1995). Radiated areas are prone to swelling followed by strictures. Webs, another cause of airway narrowing, may arise from tracheostomy sites or be congenital in the pediatric population. Foreign body aspiration, more often found in the pediatric population or in demented or obtunded patients, presents as an intrinsic obstruction.
Extrinsic Lesions
Extrinsic airway obstruction is most often due to malignancy. Wright and Mathisen (2001) described enlarged mediastinal
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lymph nodes, thyroid, or thymus tissue compressing the anterior trachea. Esophageal lesions impinge on the membranous tracheal wall. Benign conditions, such as fibrosing mediastinitis, tuberculosis, sarcoidosis, and aortic aneurysms, may also compress the airway. Large lung tumors close to the hilum can constrict a main bronchus. Large mediastinal masses can also compress cardiac chambers and restrict cardiac outflow in addition to causing airway compression.
Table 23-1. Types of Airway Pathology | ||||||||||||||||
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Airway Disruption
Loss of airway continuity may present as an emergent problem associated with trauma, as reported by Huh and associates (1997); with iatrogenic injury secondary to intubation, as described by Ross and collaborators (1997); or with biopsy, rigid bronchoscopy, or laser. Tracheal or bronchial surgery, including tracheal, carinal, and sleeve resections, creates a temporary loss of airway continuity. Airway fistulae, including bronchopleural or tracheoesophageal fistulae, also constitute a loss of continuity.
Hemoptysis
Hemoptysis is associated with any airway lesion that can erode into a blood vessel. It can also be associated with a friable or vascular endotracheal or endobronchial tumor. Hemoptysis can appear minor as with blood-tinged sputum, or it can be massive requiring urgent surgical treatment. If the source for hemoptysis is known or suspected, great care must be taken to avoid any manipulation that will induce bleeding before the patient enters a controlled operating room area.
PREOPERATIVE EVALUATION
Diagnostic evaluation of patients with obstructive lesions of the airway consists of a detailed history and physical examination, pulmonary function studies, radiographic studies, magnetic resonance (MR) imaging, and bronchoscopy. The indications for each study and the potential benefit derived from the information vary from patient to patient. In addition, the severity and urgency of airway compromise often dictate the diagnostic regimen that is followed. In life-threatening situations in which there is a high index of suspicion as to the nature of the airway pathology, diagnosis may consist only of chest radiograph and bronchoscopy. However, in the patient presenting for elective surgery with symptoms of airway obstruction, a detailed evaluation is generally warranted.
History and Physical Examination
The signs and symptoms produced by airway obstruction are affected by the anatomic location, the degree of airway obstruction, and the presence of preexisting cardiopulmonary disease. The clinical symptoms generally consist of dyspnea, especially with effort; wheezing, which may present as frank stridor; difficulty clearing secretions; inability to lie flat or lying preferentially on one side; and eventually airway obstruction. These nonspecific symptoms are frequently misdiagnosed, particularly in early stages. It is not uncommon in cases of tracheal tumors to find patients who have been misdiagnosed with asthma that fails traditional treatment modalities and who ultimately come for additional studies. Patients who have extrinsic compression of the airway involving large mediastinal masses need to be questioned carefully about their ability to sleep supine. These patients often report that they sleep very little or can sleep only sitting upright. The preferred position is important because the patient is describing the best position for minimal airway compromise and therefore anesthesia induction. If cardiac outflow is known or suspected to be compromised, the preferred position is also critical for anesthesia induction and surgical manipulation. A patient who cannot lie flat owing to the presence of an extrinsic mediastinal mass or intrinsic airway obstruction requires an awake fiberoptic intubation while sitting upright. Any attempt to induce anesthesia with the patient supine or without first securing the airway may lead to respiratory arrest and subsequent cardiac arrest.
Patients presenting with loss of airway continuity may be asymptomatic unless there is a large external communication between the airway and another space. A large airway
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rupture could result in significant dyspnea due to increased work of breathing from loss of tidal ventilation. Generally, with small lacerations, there can be crepitus that develops over time. However, if there is any chance for a ball valve effect to exist, there should be concern for the possibility of a tension pneumothorax or tension pneumomediastinum. Fistulae develop slowly and may cause no significant respiratory symptoms unless there is associated aspiration through the fistula.
Hemoptysis is reported as blood-tinged sputum in most minor cases. The frequency and amount of hemoptysis may herald increased bleeding. Massive or active ongoing hemoptysis can require emergent treatment without benefit of thorough history, physical examination, or preoperative studies.
Physical examination is essential but may be of limited value in cases of airway obstruction. Chest auscultation frequently reveals diffuse inspiratory and expiratory wheezing that is difficult to differentiate from typical asthma. Audible stridor, which is characterized by both inspiratory and expiratory wheezing, either occurring at rest or provoked with a maximal expiratory effort with an open mouth, is a common finding. Stridor signifies high-grade obstruction (>75%), which requires urgent surgical intervention. Crepitus is the most common presenting sign in instances of airway rupture.
Pulmonary Function Studies
Pulmonary function testing may be useful in helping to define the extent of obstruction. However, patients who present in acute respiratory distress need not be subjected to studies that would further compromise their limited reserve and might precipitate an acute crisis. Although standard spirometry is of limited value in diagnosing obstructive lesions, the use of flow volume loops has been shown to be very reliable. With standard spirometry, measured airflow during inspiration and expiration may be reduced. Maximal expiratory or inspiratory flow is affected to a far greater degree than is the forced expiratory volume in 1 second (FEV1). The ratio of peak expiratory flow to FEV1 has been used as an index of obstruction. When this ratio is 10:1 or greater, it is suggestive of airway obstruction. The flow volume loop is the most specific test for the diagnosis of upper airway obstruction. During a forced expiration from total lung capacity, the maximal flow achieved during the first 25% of the vital capacity is dependent on effort alone. In the case of fixed airway obstruction, the peak expiratory flow is markedly reduced, producing a characteristic plateau. With fixed intrathoracic or extrathoracic lesions, the inspiratory flow has the same characteristic plateau (Fig. 23-1). In the case of a variable obstruction, such as that seen with tracheomalacia, the maximal cutoff of inspiratory or expiratory flow depends on the location of the lesion. Extrathoracic or cervical lesions produce a plateau during inspiration, with minimal effect on expiratory flow (Fig. 23-2), whereas intrathoracic lesions that are variable tend to demonstrate alterations in the expiratory flow curve with minimal or no effect on inspiration (Fig. 23-3). In general, stenoses that are circumferential, such as those produced by cuff lesions, are fixed in origin. Tumors and tracheomalacia frequently produce a variety of intermittent obstructions. It is theoretically possible to estimate the functional impairment of the tracheal lesion by using a restricted orifice in the patient's mouthpiece as the patient undergoes the flow volume study. When the limited orifice begins to show additional effect on the flow volume loop, it can be assumed that the intrinsic lesion has reduced the trachea to that cross-sectional area. In general, airway obstruction must reach 5 to 6 mm in cross-sectional diameter
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before signs and symptoms become clinically evident. The peak expiratory flow rate decreases to about 80% of normal when the airway diameter is reduced to 10 mm.
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Fig. 23-1. Solid line shows characteristic plateau (both inspiratory and expiratory) of a fixed obstruction. Dotted lineshows normal flow volume loop. |
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Fig. 23-2. Solid line shows plateau during inspiration seen with extrathoracic obstruction. Expiration is normal. Dotted line shows normal flow volume loop. |
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Fig. 23-3. Solid line shows plateau during expiration seen with intrathoracic obstruction. Inspiration is normal. Dotted line shows normal flow volume loop. |
Pulse oximetry and room air blood gases give baseline status and indicate the patient's level of respiratory compensation. Hypoxemia and hypercarbia can result from large airway obstruction of any type and, as such, should not restrict a patient's suitability for surgery. Routine preoperative testing, including blood studies and electrocardiogram, should also be performed.
Radiologic Studies
Routine and special radiologic studies often precisely demonstrate the location and extent of airway pathology, as reported by Brown and Aughenbaugh (1991). Virtual bronchoscopy, a technique that uses a three-dimensional reconstruction of helical computed tomography (CT) data, can be used to navigate through the airways in a fashion similar to bronchoscopy, as described by Boiselle and Ernst (2002). Internal renderings allow for visualization of areas beyond a high-grade stenosis and can also be used to examine the airway serially after stent placement. External rendering of images can be used to detect subtle stenosis and tracheomalacia.
Once areas of pathology are identified, tomograms using CT or MR imaging are useful to define the lesion further. CT scans are used to examine the mediastinum, lung parenchyma, pleura, and chest wall. MR imaging is better used to delineate the extent of invasive chest wall tumors, including bone marrow and soft tissue involvement as well as vascular invasion. Some patients who are severely compromised cannot tolerate lying supine for these additional studies. When available, these studies are equally important for the surgeon and anesthesiologist in planning an approach to the airway.
ANESTHESIA PREPARATION
Monitors
Before any surgical procedure, the patient must be connected to appropriate monitors. Standard monitors for general anesthesia include establishment of a functional intravenous line, electrocardiogram and blood pressure monitors, and a reliable site and waveform for pulse oximetry. The pulse oximeter tone should be loud enough so that all involved staff can easily hear it. If cardiac compromise is anticipated, an arterial line should be placed before anesthesia induction.
Airway Evaluation
Careful attention must be taken to evaluating the anatomic configuration and function of the upper airway. Inspection of jaw motion, prominence of upper teeth, adequacy of the oral pharynx, and problems relating to mask fit must be viewed with great concern because prolonged induction with inhalation agents, if required, relies heavily on the ability to maintain an adequate natural airway. In addition, adequate neck extension is required for placement of a rigid bronchoscope.
An airway evaluation should include a discussion between surgeon and anesthesiologist. If any difficulty is anticipated in securing the airway owing to difficult anatomy, compromised respiratory status, or bleeding, there should be rigid and flexible bronchoscopes ready as well as a skilled intubator. The surgeon should be available before and throughout the induction of anesthesia. Preoperative drug administration is optional depending on the patient's underlying condition. Antisialagogues may be useful to attempt to diminish secretions associated with repeated airway manipulation. Anxiolytics, usually benzodiazepines, should be used with caution so as not to obtund a patient who is severely compromised.
SURGERY AND ANESTHESIA
Bronchoscopy for Intrinsic and Extrinsic Obstruction
Intrinsic Obstruction
Intrinsic lesions can range from distal masses or small areas of stenosis to nearly total airway occlusion from large central airway masses or high-grade stenosis. In cases in which airway patency is not considered to be a significant
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problem, the induction of anesthesia and subsequent airway evaluation may be carried out in a routine fashion. However, patients with significant intrinsic lesions must be approached with concern for possible airway occlusion during anesthesia induction and manipulation of the airway. Intubation with an endotracheal tube may not be possible owing to limited size from stenosis or tracheal obstruction secondary to a mass.
Extrinsic Obstruction
Extrinsic lesions may cause no airway compromise unless the size and location of the lesion compresses the airway. Patients with airway compression report an inability to lie flat or a position preference for lying on one side. In cases of airway compression, the intravenous induction of anesthesia may be accompanied by airway collapse. In some instances, extrinsic lesions can compress cardiac chambers. These patients also exhibit a position preference. In these cases, induction of anesthesia may be associated with cardiovascular collapse if the patient's position is changed. Therefore, the approach to anesthesia induction and securing the airway must be well planned.
Evaluation
Evaluation of a patient with airway pathology includes some type of bronchoscopy for definitive diagnosis. The type of bronchoscopy, flexible or rigid, depends on several factors. The location and size of the lesion may make intubation with an endotracheal tube difficult because of limited airway size or precarious because of the possibility of causing obstruction or bleeding. Both the anesthesiologist and the surgeon must decide whether there will be an adequate airway if intravenous induction is used. After the airway has been secured either by endotracheal tube or rigid bronchoscopy, the evaluation of the lesion should be carefully carried out.
When intravenous induction is not considered safe because of any factors associated with limited airway size, obstruction, compression, or bleeding, other techniques to secure the airway should be chosen. One option would be to conduct an awake-sedated and well-topicalized airway evaluation using a flexible bronchoscope. An endotracheal tube may be loaded on the bronchoscope for insertion after airway evaluation. However, in cases in which airway obstruction is high-grade with severe dyspnea owing to intrinsic or extrinsic obstruction or in which anxiety or emotional instability makes patient management more difficult, anesthetic induction with the patient breathing spontaneously may be required. In the case of high-grade obstruction, intrinsic or extrinsic, rigid bronchoscopy is preferred to both evaluate the area and establish airway control, as reported by Mathisen and Grillo (1989) and stated by Cavaliere and collaborators (1996). It is imperative that the surgeon be present for induction of anesthesia in case there is sudden loss of airway requiring intervention with a rigid bronchoscope.
When inhalation anesthesia for securing the airway is planned, induction with the patient spontaneously breathing potent inhalation anesthetics is usually well tolerated. Patients often prefer to be positioned semierect during the initial phase of induction. If airway collapse or cardiovascular compromise is not considered a problem, the patient may be gradually placed supine as the anesthetic is deepened. The patient must be given constant coaching to breathe and reassurance that all is well. The patient's own airway should remain open without assistance during spontaneous ventilation. Once the patient is adequately anesthetized, as judged by a significant (10% to 20%) decrease in blood pressure and heart rate, an attempt at laryngoscopy can be made and the airway secured with either a rigid bronchoscope or an endotracheal tube. Patients who are severely compromised, as judged by their tachypnea, dyspnea, agitation, and upright position, need a gentle induction with gradual increase in concentration of inhaled agent over time so as not to induce coughing or breath holding. The entire induction may take place in the preferred position in which the patient has arrived. In cases in which extrinsic compression of the airway or cardiac outflow is anticipated with position change, the patient may need to remain upright until the moment of intubation in order to retain airway patency and blood pressure. If cardiovascular compromise is a known factor delineated by preoperative studies, an arterial line should be placed before anesthesia induction, if at all possible. If an arterial line cannot be placed, once the airway is secured, blood pressure must be rapidly checked to ensure that the patient's position is not a factor in cardiac outflow.
Treatment of intrinsic lesions includes numerous modalities available to alleviate the obstruction. The planned therapy for each problem will dictate surgical equipment as well as anesthetic technique, as stated by Rampil (1992) and Hanowell and co-workers (1991). Dumon and associates (1984, 1982) reported that neodymium:yttrium-aluminum-garnet (Nd:YAG) laser therapy is widely used to resect airway tumors. It is also beneficial for treatment of strictures of all types. Laser fibers can be placed through a channel in the flexible bronchoscope in a patient who is already intubated. The rigid bronchoscope, however, is safest for laser treatment because it is inflammable. It also provides a large opening for suctioning blood and secretions and removal of pieces of lasered tissue. Resection of large airway tumors, as seen in Fig. 23-4, may cause significant ventilation compromise during removal of the mass. Resected fragments can block the distal airway. When fragments fall into the distal airway, ventilation should be suspended when feasible to limit pushing the fragments farther distally while attempts are made to retrieve the pieces using suction or grasping
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forceps. Cooperation between surgeon and anesthesiologist is critical so that adequate oxygen saturation is maintained. Bleeding from the resected mass may also interfere with ventilation. Topical dilute epinephrine (20 g/mL) can be applied to the area or injected into the base of a mass to help attain vasoconstriction.
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Fig. 23-4. A. CT scan of tumor mass in left main bronchus. B. Endoscopic view of trachea with near-total airway occlusion due to tumor arising from left main bronchus. C. Carina and both main-stem bronchi patent after rigid bronchoscopy and removal of tumor. |
Gerasin and Shafirovsky (1988) and Marasso and colleagues (1993) reported that cryotherapy and electrocautery might be useful in instances in which laser expertise is not available. Cryotherapy is not indicated in emergency situations owing to the delay required to achieve tissue necrosis. Electrocautery is also less expensive than laser surgery.
Dilation of strictures can be accomplished with rigid bronchoscopy alone using increasing sizes of rigid bronchoscope to enlarge the opening. Sheski and Mathur (1998), as well as Noppen (1997) and Ball (1991) and their colleagues, reported using balloon catheters as a useful adjunct for dilating strictures. If a balloon dilator is used, there will be periods of apnea during which the balloon will totally obstruct the airway. Patients who have been ventilated for several minutes with 100% oxygen often tolerate several minutes of apnea before desaturation becomes evident. Similarly, hypercarbia occurs during apnea, so that Paco2 rises 6 mmHg during the first minute and 3 to 4 mmHg each minute thereafter. Hypercarbia may be considered a problem after several minutes, evidenced by hypertension, tachycardia, or arrhythmias.
Mediastinal masses that do not cause airway compromise are usually of little concern. Extrinsic masses associated with mediastinal pathology with resultant airway or cardiovascular compromise require additional planning for anesthesia and surgery. As already described, both airway and cardiovascular compromise may limit positioning for induction of anesthesia and surgery. In cases in which the surgery is diagnostic and no change in the patient's postoperative respiratory status or cardiovascular status is expected, both induction and emergence are critical times during which the patient may exhibit severe airway obstruction or cardiovascular compromise. Induction, described previously, must be a gentle inhalation technique with the patient positioned so that their airway and cardiovascular status are least compromised. Emergence from anesthesia is safest with the patient returned to his or her preferred position on the operating table. The patient should remain in the operating room after extubation before transport to ensure that the airway is patent and that the patient is fully awake. The intubating equipment, including rigid bronchoscope, if used, should remain set up and ready for
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use until the patient is safely transported from the operating room.
In cases in which extrinsic masses are scheduled for resection, a lower extremity intravenous line should be inserted once the patient is asleep. Large-bore intravenous lines in the upper extremities or neck may be useless if venous return above the heart is clamped to control bleeding during the surgery. Extubation after resection of mediastinal masses may be immediate or delayed depending on the extent of surgery, blood loss, and the patient's underlying medical condition.
Both intrinsic masses and extrinsic compression due to mediastinal pathology can require airway stenting. However, once symptoms of compression or obstruction arise, initial establishment of a patent airway with induction of anesthesia may require rapid introduction of a rigid bronchoscope to prevent airway collapse. Airway stents require detailed planning for equipment and anesthesia, as discussed later.
Loss of Airway Continuity
Airway continuity can be disrupted in several ways. Tracheal or bronchial tears associated with trauma usually require surgical repair. Presenting signs and symptoms can be subtle, as described by Devitt and Boulanger (1996). Most frequently, patients have subcutaneous emphysema and dyspnea. If an airway tear is suspected, a preoperative chest radiograph is required to evaluate the possibility of a pneumothorax. Even so, the pneumothorax may not respond to chest tube insertion without repair of the injury. If the location of an airway tear is known or suspected, there should be a conservative approach to securing the airway unless urgent intubation is required, as reported by Mussi and collaborators (2000). When possible, the airway should be examined with a flexible bronchoscope loaded with an endotracheal tube so that the tear can be located and the endotracheal tube placed beyond the injury. The airway examination can be accomplished using the topical, awake, sedated technique or spontaneous ventilation using inhalation anesthesia. The endotracheal tube can be passed over the bronchoscope after the airway has been evaluated at all levels, and the cuff can be positioned at some distance from the lesion. Spontaneous ventilation helps to limit the air leak around an airway tear and may avoid the possibility of a tension pneumothorax, which could easily occur in the presence of positive-pressure ventilation. If emergent intubation is required, it should be accomplished rapidly with the understanding that a leak may become more significant and a tension pneumothorax is possible. In all cases, nitrous oxide is to be avoided.
When airway resection is planned, the approach to intubation and ventilation should be coordinated before surgery. In the case of tracheal resection, intubation may be straightforward, or the airway may be secured and dilated in cases of severe stenosis with rigid bronchoscopy followed by an endotracheal tube. Once the airway is opened, either in the neck or chest, there are several choices for ventilation. The patient may maintain spontaneous ventilation, or controlled ventilation with paralysis may be chosen. An endotracheal tube and sterile anesthesia setup can be inserted on the field distal to the divided trachea to allow for ventilation during the resection of the airway. An alternative method of ventilation is to pass a catheter through the endotracheal tube past the divided trachea and to use either machine jet ventilation or a handheld Sander's injector (Fig. 23-5). The catheter may be a simple No. 14F suction catheter that has been cut to remove side holes. With the airway open, the surgeon can place the catheter into the left main bronchus under direct vision. In some instances, when the airway resection is carinal or right bronchial, an extended endotracheal tube can be fashioned from two endotracheal tubes. An endotracheal tube is lengthened using alcohol to fix the two sections together with a proximal extension from a half-size-smaller tube (Fig. 23-6). The tube can be placed initially in the trachea. Once the airway is divided, the tube can be advanced into the left main bronchus to ventilate the left lung during the resection. However, the cuff of a standard endotracheal tube is longer than the bronchial cuff of a double-lumen tube. Therefore, the large cuff has the potential to interfere with a carinal resection. Once the resection is completed, the endotracheal tube cuff is placed either above or below the resection margin. The patient can be awakened and extubated as per routine as detailed by Wilson (1991).
Both tracheoesophageal and bronchopleural fistulae may be insignificant, requiring no respiratory maneuvers. However, when air loss through a fistula is problematic, induction of anesthesia may be accomplished safely by using a spontaneous inhalation technique. The endotracheal tube requires bronchoscopy for positioning. A fistula located in the trachea can usually be bypassed by placing the endotracheal tube cuff beyond the fistula. If a fistula communicates through a bronchus, a standard double-lumen tube can be placed with the aid of bronchoscopic postioning. Jet ventilation also provides an alternative method of ventilating in a patient with a bronchial fistula.
Bleeding
Hemoptysis may be a presenting complaint before surgery. Small amounts of hemoptysis are well tolerated. If the location of the lesion is known, it is best to avoid the area by choosing either a single-lumen endotracheal tube for airway evaluation or a double-lumen tube that does not touch the affected area. Fiberoptic placement of either a single- or a double-lumen tube may be required to avoid a bleeding lesion. In the case of ongoing hemoptysis, it is desirable to protect the unaffected lung, if possible. If the site of a lesion is known, rapid placement of a double-lumen tube would be desirable if at all possible. However, rigid bronchoscopy
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may be needed to establish an airway and both suction the airway and attempt to provide hemostasis.
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Fig. 23-5. Sander's injector with blender valve for delivery of air-oxygen mixture. Inset: Handheld injector fitted with plastic tubing and side port connector for rigid bronchoscope. |
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Fig. 23-6. A 7-mm inner diameter (ID) endotracheal tube, circuit connector removed, lengthened with the proximal end of a 6.5-mm (ID) endotracheal tube. |
Ventilation
In routine cases in which airway evaluation is not expected to be compromised by significant lesions, a patient can be intubated with an endotracheal tube and evaluated with flexible fiberoptic bronchoscopy while anesthesia is administered using a standard anesthesia machine and inhaled agents or intravenous drugs. More commonly, however, the patient with airway pathology will require rigid bronchoscopy for evaluation or treatment. The use of both rigid and flexible bronchoscopy is reviewed by Prakash (1999).
The rigid bronchoscope provides an open, uncuffed airway. Jet ventilation, initially described by Sjostrand and Eriksson (1980), is particularly well suited to rigid bronchoscopy because jet ventilation requires an open system. Early descriptions of jet ventilation by Sanders (1967) and associated anesthesia techniques reported by Carden (1978) are still valuable today. Anesthesia is induced either with intravenous drugs or inhaled agents. Bourgain and collaborators (2001) described transtracheal jet ventilation in a multicenter study. Once the bronchoscope is placed in the airway, the side port can be connected to some form of jet ventilation. Anesthesia can be maintained with an intravenous infusion of propofol, which can be regulated to attain deep levels of anesthesia often without the need to add paralytic agents after the initial intubation. Small supplements of a short-acting narcotic such as alfentanil can also be used to deepen the anesthesia. The handheld Sander's injector is easy to use and allows for simple control of intermittent ventilation during bronchoscopic manipulation of the airway. The stand-alone jet ventilator can be used as an alternative. Machine ventilators allow for high-frequency ventilation and measurement of expiratory airway pressure. Another option that has been described is to use spontaneous assisted ventilation in which no muscle relaxant is used and an Ambu bag with a high-flow oxygen source, which is connected to the side port of the rigid bronchoscope, as described by Perrin and co-workers (1992). It is also possible to use the anesthesia ventilator with a rigid bronchoscope if the pharynx is packed with damp gauze; however, this system is associated with significant leakage of anesthetic gases and difficulty ventilating with adequate tidal volumes. The laryngeal mask airway, as reported by Adelsmayr (1998) and Biro (2001) and their co-workers, has also been used in conjunction with high-frequency jet ventilation for high tracheal and laryngeal procedures. As already mentioned, various types of catheters can be placed in the airway to allow for jet ventilation in the divided or distal airway.
Jet ventilation, either by ventilator or handheld equipment, should be adjusted to attain oxygen saturations above 90%. A mixing valve allows for variable oxygen concentration to be delivered via the jet. In laser cases, the Fio2 should be less than 0.5. However, higher oxygen concentrations may be required intermittently to increase oxygen saturations above 90%. Driving pressure and the inspiratory-to-expiratory ratio can also be varied until adequate oxygen saturation is achieved. End tidal CO2 is not able to be accurately determined in an open system, although transcutaneous CO2 monitoring can be used. If ventilation is inadequate and CO2 increases, hypertension and cardiac arrhythmias are usually seen. Visual inspection of the chest should show equal bilateral excursion, if possible. In cases of tumor or foreign body obstruction, bilateral chest excursion may be limited by the obstruction. Communication between surgeon and anesthesiologist during jet ventilation is essential. If the bronchoscope is placed past an obstruction and the open system becomes closed, there is significant risk for tension pneumothorax.
If rigid bronchoscopy is used for airway access and surgical treatment, once the problem has been adequately resolved, the bronchoscope can be removed. Alternatively, the patient may awaken with the rigid bronchoscope in place. Once that patient's spontaneous respirations are adequate, the bronchoscope may be withdrawn and a mask anesthesia circuit used for further emergence. If any question of airway patency arises, the rigid bronchoscope can be removed before awakening, and the patient can be reintubated with an endotracheal tube to allow for further evaluation using a flexible bronchoscope and eventual extubation.
Stent Placement
Airway stent placement can present a significant challenge for ventilation. Baraka and associates (2001) reported the use of jet ventilation for stent placement in tracheal stenosis. Expandable stents can be placed using a flexible bronchoscope and may be accomplished with the patient either under general anesthesia or with sedation and topical agents. Silicone stents are most often placed using rigid bronchoscopy, as described by Montgomery (1965) and Dumon (1990). Surgical techniques for stent placement are well documented by Cooper and colleagues (1989). Anesthetic management throughout stent insertion requires constant communication and cooperation between surgeon and anesthesiologist. After anesthetic induction, the airway is given over to the surgeon for placement of the rigid bronchoscope to evaluate the lesion and determine the appropriate stent size and shape. The rigid bronchoscope may then be removed for stent preparation and application. Airway control should return to the anesthesiologist, and the patient should be hyperventilated and well oxygenated, preferably with 100% oxygen using a mask anesthesia circuit. During the stent placement, ventilation is suspended. Patients who have adequate underlying lung function can tolerate several minutes of apnea without hypoxemia or hypercarbia. Strict
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attention must be paid to the pulse oximeter tone during apnea. If the oxygen saturation drops below 90% and the stent is not in place, the patient should be ventilated again if possible. Jet ventilation through the rigid scope should improve oxygenation unless the stent blocks the airway. If the stent is a distal Y stent or a T tube, it is important to ascertain that both limbs are patent. Folding of a limb of a T or Y tube can make ventilation impossible and could require emergent removal of the stent. Once a stent is placed, the patient may awaken with the rigid bronchoscope in place or with mask ventilation. If a stent reaches into the upper trachea, standard intubation should be avoided because an endotracheal tube may attach to the stent and remove it with extubation.
COMPLICATIONS
Both anesthesia and surgery for airway pathology cases are associated with complications of technique that are well documented. (Table 23-2). Airway manipulation with a rigid bronchoscope can be associated with bleeding from the resected area despite laser coagulation. Bleeding from friable tissue can cause significant compromise of ventilation. Rapid suctioning may be useful, but irrigation with a solution of epinephrine (20 g/mL) or injection at the base of a mass with the epinephrine may be required to control bleeding. A rigid bronchoscope can also be used to tamponade a bleeding site. Use of lasers is associated with the risk for fire and airway perforation, as reported by Denton and collaborators (1988) with comments by Brutinel and co-workers (1988). In cases in which the rigid bronchoscope is used to shave off a mass or in which laser treatment is used, pieces of necrotic or friable tissue, as well as clots from bleeding, can block the distal airway. Brief suspension of ventilation with retrieval of the tissue is required.
Airway perforation, as documented by Conacher (1992), may be associated with manipulation of the bronchoscope or attempted resection of a mass or stricture. Foreign body retrieval can also cause an airway perforation. Rigid bronchoscopy can result in vocal cord injury because of insertion difficulty. Barotrauma can occur suddenly when jet ventilation is being used. Jet ventilation requires an open airway to avoid air trapping and barotrauma. If a mass causes a ball valve effect or a bronchoscope in a distal airway closes the route of air exit, air pushed behind the mass or bronchoscope with the jet ventilator can result in a tension pneumothorax, as reported by Oliverio and co-workers (1979). It is imperative that the position of the bronchoscope be clear to the anesthesiologist so that ventilation can be suspended for short periods of time during bronchoscopic manipulation in narrowed airways. Absence of chest excursion, sudden tachycardia, and hypotension are all signs associated with pneumothorax. Rapid decompression is required to prevent cardiovascular collapse.
Table 23-2. Complications | ||||||||
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Inadequate oxygenation and ventilation are always of concern with both jet ventilation and intermittent ventilation, which are used during airway surgery. Strict attention to the loud pulse oximeter tone should signal the need for ventilation. Early intervention with ventilation is prudent in patients who have high-grade airway obstruction or poor underlying lung function because the oxygen saturation may fall quickly and return slowly. Evidence of hypertension or arrhythmias may indicate hypoventilation. Although transcutaneous CO2 monitoring is possible, it is not usually required when close attention is paid to vital signs.
Ultimately, airway sharing requires communication and planning. With knowledge of the underlying lesion and the planned procedure, both the surgeon and anesthesiologist should formulate an approach to the problem. During the procedure, strict attention should be given to the patient's clinical state and all vital signs so that the outcome is safe and successful.
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