Impact of Anesthetic Choice (Sevoflurane Versus Desflurane) on Airway Reflex Recovery in the Context of Antagonized Neuromuscular Block

Effect of Anesthetic Choice (Sevoflurane Versus Desflurane) on Speed and Sustained Nature of Airway Reflex Recovery in the Context of Antagonized Neuromuscular Block

Protective airway reflexes may be impaired in the postoperative period, creating the potential for aspiration of gastric contents, even after a patient exhibits appropriate response to command. Because assessment of airway reflex recovery is not possible in an intubated patient, the clinician must make an empiric decision as to when a patient is safe to extubate, and choose a combination of techniques least likely to result in pharyngeal impairment. Adequacy of reversal of neuromuscular block by cholinesterase inhibitors (e.g., neostigmine) is unpredictable, especially in the presence of profound paralysis, and tactile assessment of train-of four and sustained tetanus has shown poor correlation with objective assessments. Protective airway reflexes may also be impaired during early recovery by the anesthetics themselves, even when muscle relaxant has been avoided. In the absence of muscle relaxant the investigators previously demonstrated that patients receiving an anesthetic with higher tissue solubility, sevoflurane showed significantly greater impairment of swallowing up to 14 minutes after response to command compared to patients receiving an anesthetic with lower tissue solubility, desflurane. Therefore, we ask whether the combination of the more soluble anesthetic and the presence of neuromuscular block antagonized by neostigmine may create a multiplicative effect that might further prolong pharyngeal recovery. We plan to randomly assign 100 patients scheduled to undergo surgery with general anesthesia to a standardized anesthetic that includes 1) sevoflurane, rocuronium with 70 µg/kg neostigmine + 14 µg/kg glycopyrrolate antagonism (group S); or 2) desflurane, rocuronium with 70 µg/kg neostigmine + 14 µg/kg glycopyrrolate antagonism (group D). Airway reflex recovery will be judged as adequate by the patient's ability to swallow 20 mL of water without coughing or drooling 5, 10, 15, 20, 30 and 60 minutes after response to command. Anesthetic (sevoflurane or desflurane) will be discontinued after administration of reversal agent and recovery to TOF (train-of-four) ratio of 0.7.

Inclusion Criteria:

• ASA 1-2 patients
• Age 18-65 years
• body mass index (BMI) ≤ 35kg/m2
• Planned surgery requiring general anesthesia lasting approximately 1.5-3.0 hours
• Surgery requires or benefits from skeletal muscle relaxation
• All must pass the baseline 20 mL water swallowing test as previously described.

Exclusion Criteria:

• Pre-existing neuromuscular or central nervous system disorder
• Known condition interfering with gastric emptying
• Planned surgical procedure on the head or neck
• Known liver disease
• Serum creatinine > 1.5 mg/dL
• Concurrent use of neuroleptic medications
• Contraindication or previous adverse response to any of the study drugs
• Active asthma or reactive airways disease
• Surgery where upright position or brief cough would be contraindicated
• Inability to provide informed consent