Initial Phase. At the simplest level, anesthesia for tracheal reconstruction is an exercise in sharing the airway. After evaluation, induction, and possibly bronchoscopy, the airway is secured with a tube distal to the lesion. Part of the value of the initial bronchoscopy is to assist planning of the means of securing the airway. The anesthesiologist should view the airway with the surgeon, and get a sense of the lumen size and course. Knowing the airway is bloody or friable will help in the management of a sudden obstruction during the operation.
There are three good reasons to start with rigid bronchoscopy: 1) examination of the trachea and assessing resectability, 2) dilating tight stenoses or removing some endoluminal tumor to permit passage of an endotracheal tube, and 3) in the worst cases, providing the airway used for the procedure. Rigid bronchoscopy is essential when the airway lumen is significantly compromised; that is, less than 5 or 6 mm in diameter. Unless the airway is dilated, the initial operative course will feature hypoventilation with attendant hypoxia, hypercarbia, and arrhythmias.
Induction can be either inhalation or intravenous depending on the underlying pathology and the experience of the practitioners. Long-acting agents are unwise since the initial bronchoscopic evaluation may find that a resection should be postponed or cancelled.
Anesthetic maintenance can be achieved in several ways.24,25 Inhalation agents, which blunt airway reflexes well, are inexpensive and are relatively quickly dissipated. The disadvantage is that the airway will be opened intermittently during the procedure, so that much of the agent will contaminate the operating room environment. Also, during those periods, no anesthetic will be administered to the patient, requiring compensatory deeper levels before and after.
Total intravenous anesthesia is well suited to tracheal surgery. The processes of ventilation and anesthesia delivery are decoupled, and the operating room air is not contaminated. Remifentanil and propofol delivered by infusion are an excellent choice. Airway reflexes are well blunted, and the effects wear off quickly at the conclusion. Other intravenous regimens such as ketamine hydrochloride infusions, sufentanil citrate or alfentanil hydrochloride infusions, and barbiturates are certainly possible, but run the risk of producing lingering postoperative sedation, which is undesirable.
Regional techniques are used for simple tracheal procedures, like flexible bronchoscopy and occasionally tracheostomy. In theory, a cervical tracheal resection could also be performed under block, but the level of cooperation required, particularly if rigid bronchoscopy is contemplated, makes it impracticable.
The monitoring required for tracheal surgery concentrates on the assessment of respiration. CO2 measurements in the end-tidal gas and arterial blood are helpful to assess the adequacy of ventilation. Oxygenation is confirmed by pulse oximetry. An arterial catheter is helpful, especially in the postoperative period. It is possible to compress the innominate artery, which crosses the trachea at the sternal notch. Such compression will impair blood flow to the right arm and right carotid. Either an arterial line or pulse oximeter on the right arm will provide warning. More extensive hemodynamic monitoring should be dictated by other coexisting conditions. Intravenous access will be needed, but major volume requirements are rare.
Resection. The preferred position of the endotracheal tube at the start of the resection is distal to the lesion (Figure 18-1A). If the tube is proximal, the surgical manipulation may provoke airway obstruction in some types of tracheal lesions. In some situations, distal intubation will not be feasible. Once the airway is secured, the patient is positioned for the tracheal resection with the neck extended to deliver the trachea out of the thorax. Space will be tight around the patient's head, but access must be preserved to allow the anesthesiologist to manipulate the endotracheal tube, an essential part of the procedure.
Surgical dissection is performed to expose the affected region, and the endotracheal tube is withdrawn sufficiently to allow severing of the trachea (Figure 18-1B). Ventilation is then accomplished with a tube placed in the surgical field into the distal trachea, attached to a circuit that is accessible by the anesthesiologist. If possible, the circuit should include a sampling port to allow assessment of end-tidal CO2.
The tube placed on the field will lie in a tightly curved position, so a nonkinking flexible armored tube is preferable. The tube is also placed into a rather short distal tracheal segment, so that it will easily be advanced into a mainstem bronchus. For all these reasons, as well as the potential that blood and clots can run into the trachea from the surgical field, the anesthesiologist must maintain close vigilance over the tube position and pulmonary compliance.
An alternative to distal intubation with an endotracheal tube is the use of jet ventilation with a jet catheter.26,27 The jet catheter is of smaller caliber and does not require a seal to deliver tidal volume. There are some drawbacks to jet ventilation, including more difficult assessment of the adequacy of ventilation, unless a separate distal sampling catheter is used. Barotrauma is a constant risk if the catheter is advanced into too small a segment of the pulmonary tree. Jetted gases are rarely humidified, so the respiratory tract will become dehydrated, and secretions will be more difficult to mobilize. It is hard to deliver gaseous anesthetics via jet ventilation, and there is the aesthetic problem of aerosolized blood and secretions from the jetting process. Finally, the jet catheter will tend to recoil from the airway, so it must be held in place by a member of the surgical team.
One other proposed method for oxygenation and ventilation is the use of cardiopulmonary bypass (CPB). No airway appliance would be required with this technique. There are substantial disadvantages to CPB, including the need for anticoagulation, microemboli, and more invasive access. More difficult reconstructions, where CPB might be contemplated, usually are intrathoracic, and the substantial lung manipulation required for surgical access would be damaging in the anticoagulated state. Indeed, in experienced centers, CPB is never needed unless major vascular or cardiac work is also required (eg, vascular rings).
Reconstruction. The necessary resection is done and the reconstruction prepared by placing sutures loosely spanning the resected area. Intermittent removal of the endotracheal tube facilitates placement of sutures in the distal margin. When it is time to bring the two tracheal ends together, the surgical tube is withdrawn and the orotracheal tube is carefully advanced into the distal trachea (Figure 18-1C).
Flexion of the neck shortens the distance from the trachea to the carina, so the neck is now flexed to allow the tracheal ends to be reapproximated without tension. This neck flexion will be maintained for the balance of the procedure and throughout the postoperative recovery period.
In some instances, the orotracheal tube will have been withdrawn entirely from the trachea during the reconstruction to allow better exposure of the subglottic larynx for repairs at that level. Direct laryn-goscopy to replace it would be difficult under the surgical drapes, but fiber-optic intubation would certainly be possible. Fortunately, there is a clever alternative method of intubation. A small stiff catheter is passed retrograde from the surgical field, and fished out of the mouth. An endotracheal tube can then be sutured to the end of the catheter, and the whole assembly pulled into the trachea. This maneuver will be necessary if the orotracheal tube is pulled out, if the patient had a preexisting tracheostomy that was used initially, if the rigid bronchoscope served as the airway during the initial phase of the resection, or if the endotracheal tube was damaged when the trachea was entered. For proximal lesions, where the tube will likely need to be pulled out of the trachea, suturing a catheter to the orotracheal tube before it is fully withdrawn may simplify the reintubation.
Emergence. At the end of the procedure, the goal is to have an extubated patient with a patent airway. There are several reasons to prefer extubation. An appliance in the trachea will irritate the tracheal anastomosis, especially if the end of the tube or the cuff is at the suture line. Positive pressure ventilation will also put strain on the suture line, and tend to push air into the tissues until the mucosa has sealed. A tra-cheostomy distal to the repair is possible, but will injure some of the remaining good trachea, so it is avoided. If the airway needs to be secured in the postoperative period, either because of transient swelling or injury to the innervation to the cords, then a small uncuffed tube is preferred. The reintubation can be achieved either with direct laryngoscopy while maintaining strict neck flexion (a straight laryngoscope blade works best) or by fiber-optic intubation.
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