INTRAOPERATIVE
Anesthetic technique: GETA. Airway management requires careful planning and continuous communication with the surgeon. Surgical requirements include adequate muscle relaxation (movement, coughing, or bucking during endoscopy may have disastrous consequences) and immobile vocal cords for vocal cord surgery. Cardiovascular stability is important: laryngeal, tracheal, and carinal reflexes may provoke severe ↑ BP and ↑ HR, which can be detrimental in some patients. Adequate depth of anesthesia is essential, but the requirements for rapid awakening and return of laryngeal reflexes present additional challenges in anesthetic management. Short-acting β-blockers (e.g., esmolol) may be indicated to treat breakthrough sympathetic responses, especially in patients with cardiac disease. Remifentanil or alfentanil (see Introduction, p. 178) is useful for these procedures, which, although highly stimulating, are characterized by minimal or absent postop pain, and the majority of patients are discharged home from the recovery room.
Special considerations: If flexible bronchoscopy is planned, the patient’s trachea is intubated in routine fashion by the anesthesiologist with a large-diameter ETT (7.5-8.0 mm ID) to acommodate a flexible video bronchoscope. The ETT is usually taped midline. As an alternative, in selected patients, flexible bronchoscopy can be performed without tracheal intubation through the Patil-Syracuse mask during manual bag-mask ventilation. Placement and manipulation of the flexible bronchoscope by the surgeon will be facilitated by the concomitant use of one of the hollow oral airways used for the fiberoptic intubation (e.g., Williams airway). The patient can then be tracheally intubated with a smaller diameter ETT (e.g., 6.0 mm ID), to facilitate surgical access.
Flexible esophagoscopy is rarely performed as an isolated procedure but, if done, would also be facilitated by tracheal placement of a small-diameter (e.g., 6.0 mm ID) ETT. The ETT is usually moved over to the left corner of the mouth and taped to the lower jaw, to provide more room for the esophagoscope advancement and manipulation.
If rigid bronchoscopy is planned first, GA is induced, and the patient is hyperventilated through the face mask with FiO2 = 1.0. Following muscle relaxation, the surgeon may proceed, without securing an airway. Quick and gentle DL for application of topical lidocaine to the larynx and upper trachea (LTA, 4% lidocaine 3-4 cc) before rigid bronchoscopy may help blunt hemodynamic responses to the subsequent surgical manipulation. DL with LTA should be avoided in patients with tumors at the base of the tongue (↑ risk of bleeding; see Anesthetic Considerations for Glossectomy, p. 212) or when preexisting copious secretions or bleeding are present in the upper airway 2° risk of pulmonary aspiration on emergence from anesthesia. It is advisable to demonstrate to the surgical team and document in the chart absence of dental damage after DL has been performed.
After the rigid bronchoscope is introduced into the patient’s trachea, it is connected to an anesthesia circuit through a flexible side port adapter (Racine,
Fig. 3-1), and the patient is ventilated manually. High flows are usually required because of the leak around the bronchoscope. Close communication with the surgeon is essential for adjusting ventilation when the bronchoscope is introduced into the mainstem bronchus to avoid high inflating pressures and to ensure complete exhalation (↓ risk of barotrauma). After rigid bronchoscopy is completed, mask ventilation with FiO
2 = 1.0 before intubation is advisable to ensure adequate oxygenation and normocapnia. A reinforced ETT is useful for
rigid esophagoscopy to avoid possible compression of the ETT. The ETT should be moved to the left side of the patient’s mouth to facilitate introduction of the surgical instruments and taped to the lower jaw because full opening of the patient’s mouth is required.
For operative microlaryngoscopy, a small-diameter (usually 5.0 mm ID), cuffed long microlaryngeal tube (MLT) is most commonly used to facilitate visualization of the larynx, but will interfere with posterior glottis lesions, for which jet ventilation (see below) is most commonly employed. The CO2 laser, which can precisely vaporize superficial tissue, is widely used for vocal cord laser surgery, whereas the Nd:YAG (neodymium-yttrium-aluminumgarnet) laser is usually employed for airway tumor debulking because of its ability to coagulate deeper lesions. The Nd:YAG can be used through the suction channel of the fiber optic or video bronchoscope, whereas the CO2 laser must be aimed directly at the targeted tissue. Both the CO2 and Nd:YAG wavelengths lie outside the visible spectrum, and a separate, lower energy visible beam is used for aiming. The patient must be motionless, the patient’s eyes must be protected with tape and moistened gauze, and OR personnel must wear protective goggles.
An intermittent apnea technique involves hyperventilation, followed by intermittent tracheal extubation for 1-5 min, during which the laser is used. This approach is time consuming and may be associated with a higher incidence of airway trauma and edema 2° repeated intubations. Careful pulse oximeter monitoring is essential for this technique.
Manual low-frequency jet ventilation (
Fig. 3-3), or
automated high-frequency jet ventilation (HFJV) may be necessary when an ETT cannot be used (e.g., some supraglottic and subglottic lesions). For supraglottic manual jet ventilation, the ventilating laryngoscope is most commonly employed. The axis of the jet should be in line with the trachea, and full egress of air (complete chest deflation) should be ensured between the jet ventilator “puffs.” Close communication with the surgeon is essential. The jet should be triggered during pauses between laser firings to keep the vocal cords immobile. If jet ventilation is used for laser resection of papillomas, there is a risk of spreading the virus to OR personnel, and special face masks should be worn in the OR. Jet ventilation generally provides adequate ventilation without introducing flammable material into the airway or obstructing the surgical field. Its use, however, may be associated with potentially severe complications, including barotrauma, pneumothorax and gastric distension (risk of regurgitation), and is hindered by ↓ chest-wall into the airway or lung compliance. Full muscle relaxation is usually required to facilitate precise laser firing. HFJV is most commonly delivered through a subglottic catheter or specialized tube (e.g., Hunsaker tube).
For laser cases, precautions must be taken to prevent airway fire, including
Use special laser ETT (e.g., Mallinkrodt Laser-Flex, Xomed Laser Shield), although none of them provides 100% protection from all types of lasers. Small (5.0 mm ID and smaller) diameter laser ETTs are preferred to facilitate surgical access.
Use the lowest possible FiO2 (≤ 0.3 strongly preferred), that will ensure adequate oxygenation (dilute O2 with air, N2, or helium) and avoid N2O (both O2 and N2O promote combustion).
Use colored (methylene blue-tinged) NS in the ETT cuff (will immediately alert the surgeon in case of a laser hit).
Place the ETT sufficiently deep into the trachea for the cuff to reduce the risk of laser contact.
Similar considerations apply in patients undergoing endoscopic Zenker’s diverticulectomy, when the CO2 laser is used.