Anesthetic management of the thoracic surgical patient may improve operative conditions, efficiency, and outcome. Overlap exists in the territories of responsibility between thoracic surgeons and anesthesiologists, highlighting the importance of communication and mutual understanding. This chapter provides a brief overview of the general conduct of anesthesia for pulmonary resections, followed by a discussion of selected concepts in thoracic anesthesia of utility to thoracic surgeons.
Overview: Conduct of Thoracic Anesthesia for Pulmonary Resection
Barring extremes of pathophysiology (e.g., end-stage chronic obstructive pulmonary disease), lesion-related hazards (e.g., compression of vital structures), or important coexisting disease states, the conduct of anesthesia for pulmonary resection is largely dictated by the surgical approach. For thoracotomy, the most common strategy consists of general anesthesia with paralysis, an arterial catheter (and possibly a central venous catheter), double-lumen tube (DLT), thoracic epidural, and immediate postoperative extubation.
Before induction, antibiotics, sedatives, and nebulized bronchodilator treatments are administered as indicated and the epidural is positioned and tested. After induction, diagnostic bronchoscopy may be performed via a large (8–8.5 mm) endotracheal tube or laryngeal mask airway (LMA). Findings that may affect the lung isolation plan should be noted by the anesthesia team at this time. Lung isolation by DLT or bronchial blocker (BB) then is imposed, with confirmation of position by pediatric fiberoptic bronchoscopy. After lateral decubitus positioning, repeat bronchoscopy is recommended. Ventilator parameters must be adjusted with initiation of one-lung ventilation (OLV) to ensure adequate gas exchange and to prevent barotrauma. Surgical entrance of the pleural space permits direct evaluation of the quality of lung isolation. Suctioning of secretions may aid atelectasis. Blood products should be available and checked before hilar dissection. Cross-clamp of the pulmonary artery typically does not cause changes in central venous pressure (CVP) or hemodynamics in patients with adequate cardiopulmonary reserve, and oxygenation should improve (see below). On cross-clamping of the bronchus, unchanged ventilatory compliance should be confirmed. If available, bronchoscopic visualization of the stump is useful before stapling. A “leak test” is commonly used by providing 20 to 30 cm H2O of positive pressure ventilation to the submerged stump. Recruitment of any remaining lung is accomplished with incremental 5-second periods of 20 to 40 cm H2O of positive pressure (recruitment maneuvers). After closure and supine repositioning, a final bronchoscopy via a large tube or LMA may necessitate a tube exchange. Rapid emergence and extubation depend on the strategic use of short-acting anesthetic agents; limited narcotic use; full reversal of muscle relaxation; control of secretions, bronchospasm, and pain (thoracic epidural); and return of airway reflexes, sensorium, and adequate respiratory efforts. Respiratory mechanics are greatly aided by raising the head of the bed more than 30 degrees at emergence (see Chapter 8).
Variations on the foregoing and procedure- or lesion-specific issues are presented as “bullet points” at the conclusion of this chapter.