Purpose: Chemical and mechanical irritation of the tracheal mucosa influences the incidence of cough at emergence from general anesthesia, potentially leading to significant postoperative complications. This study evaluates the benefits of endotracheal tube (ETT) intracuff alkalinized lidocaine during N2O-free general anesthesia by 1) assessing the in vitro effect of alkalinization on lidocaine diffusion kinetics across the cuff's membrane and 2) evaluating, in a randomized controlled clinical trial, the impact of 160 mg of intracuff alkalinized lidocaine on cough upon emergence from anesthesia for surgery lasting > 120 min.
Methods: In the in vitro study, diffusion kinetics of various intracuff alkalinized lidocaine amounts (40, 80, and 160 mg) were compared to their non-alkalinized lidocaine controls. In the clinical trial, 80 adult patients (American Society of Anesthesiologists physical status I-III) undergoing urological or gynecological surgery expected to last > 120 min and scheduled for N2O-free general anesthesia were enrolled. The ETT cuffs (high-volume, low-pressure) were filled with either 160 mg of alkalinized lidocaine or a comparable volume of 0.9% saline. The primary outcome was the incidence of cough upon emergence from anesthesia. Sore throat, hoarseness, and postoperative nausea and vomiting were evaluated as secondary outcomes.
Results: Our in vitro study confirmed that alkalinization increases lidocaine diffusion across the membrane of ETT cuffs and suggested that the lidocaine diffusion rate is associated with the initial intracuff lidocaine quantity. Our clinical trial demonstrated that, compared with the saline group, 160 mg of intracuff alkalinized lidocaine reduced the incidence of cough upon emergence from N2O-free general anesthesia (76% vs 34%, respectively; difference 42%; 95% confidence interval, 21% to 62%; P < 0.001) while having no clinical impact on secondary outcomes.
Conclusions: The use of 160 mg of intracuff alkalinized lidocaine is associated with a decreased incidence of cough upon emergence from N2O-free general anesthesia > 120 min. This trial was registered at www.clinicaltrials.gov (NCT01774292).