Comparison of propofol and propofol/ketamine anesthesia for evaluation of laryngeal function in healthy dogs.

Thiopental is an excellent choice for evaluation of laryngeal function. Unfortunately, thiopental is no longer manufactured. In its absence, the ideal anesthetic protocol for laryngoscopy has not been determined. Propofol and propofol/ketamine were compared for the evaluation of laryngeal function in 48 healthy dogs. Laryngeal exposure was moderate to excellent in all dogs and not significantly different between protocols. Saturation of peripheral O2 (SPO2) readings were decreased in the propofol/ketamine group, and deeper respirations were more likely to correlate with normal laryngeal function regardless of treatment group. Doxapram was administered to apneic patients to stimulate respiration and allow for evaluation of laryngeal function. No significant difference in frequency of doxapram administration between groups was noted. Doxapram resulted in higher respiratory scores and significantly increased the ability to determine normal laryngeal function. Ketamine did not allow for a reduction in propofol dose and caused increased respiratory depression, making ketamine a poor addition to propofol for laryngeal function examination. Regardless of the protocol used, laryngeal function should be determined in conjunction with the respiratory phase and depth of respirations. Patients with either absent or shallow respirations should receive doxapram for accurate evaluation of laryngeal function.