Anesthesia for Diagnostic Thoracic Procedures
Rigid bronchoscopy for removal of foreign bodies or tracheal dilatation is usually performed under gen-eral anesthesia. These procedures are complicated by the need to share the airway with the surgeon or pulmonologist; fortunately, they are often of short duration. After a standard intravenous induction, anesthesia is often maintained with total intrave-nous anesthesia, and a short- or intermediate-acting NMB. Brief airway procedures are among the few remaining indications for a succinylcholine infusion. One of three techniques can then be used during rigid bronchoscopy: (1) apneic oxygenation using a small catheter positioned alongside the broncho-scope to insufflate oxygen (above); (2) conventional ventilation through the side arm of a ventilating bronchoscope (when the proximal window of this instrument is opened for suctioning or biopsies, ventilation must be interrupted); or (3) jet ventila-tion through an injector-type bronchoscope.
Mediastinoscopy, much more commonly employed in the past than at present, provides access to the mediastinal lymph nodes and is used to establish either the diagnosis or the resectability of intratho-racic malignancies (above). Preoperative CT or MR imaging is useful for evaluating tracheal distortion or compression.
Mediastinoscopy is performed under general tracheal anesthesia with neuromuscular paralysis. Venous access with a large-bore (14- to 16-gauge)intravenous catheter is mandatory because of the risk of bleeding and the difficulty in controlling bleeding when it occurs. Because the innominate artery may be compressed during the procedure, blood pressure should be measured in the left arm.
Complications associated with mediastinos-copy include: (1) vagally mediated reflex bradycardia from compression of the trachea or the great ves-sels; (2) excessive hemorrhage (see above); (3) cere-bral ischemia from compression of the innominate artery (detected with a right radial arterial line or pulse oximeter on the right hand); (4) pneumotho-rax (usually presents postoperatively); (5) air embo-lism (because of a 30° head elevation, the risk is greatest during spontaneous ventilation); (6) recur-rent laryngeal nerve damage; and (7) phrenic nerve injury.
Bronchoalveolar lavage may be employed for patients with pulmonary alveolar proteinosis. These patients produce excessive quantities of surfactant and fail to clear it. They present with dyspnea and bilateral con-solidation on the chest radiograph. In such patients, bronchoalveolar lavage may be indicated for severe hypoxemia or worsening dyspnea. Often, one lung is lavaged, allowing the patient to recover for a few days before the other lung is lavaged; the “sicker” lung is therefore lavaged first. Increasingly, both lungs are lavaged during the same procedure, creating unique challenges to ensure adequate oxygenation during lavage of the second lung.Unilateral bronchoalveolar lavage is performed under general anesthesia with a double-lumen bronchial tube. The cuffs on the tube should be properly positioned and should make a watertight seal to prevent spillage of fluid into the other side. The procedure is normally done in the supine posi-tion; although lavage with the lung in a depen-dent position helps to minimize contamination of the other lung, this position can cause severe ventilation/perfusion mismatch. Warm normal saline is infused into the lung to be treated and is drained by gravity; treatment continues until the fluid returning is clear (about 10–20 L). At the end of the procedure, both lungs are well suctioned, and the double-lumen tracheal tube is replaced with a single-lumen tracheal tube.
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