Comparison of methohexital and propofol as induction agents for evaluation of laryngeal function in healthy dogs

OBJECTIVE: To determine the influence of propofol or methohexital, with and without doxapram, on the examination of laryngeal function in dogs. STUDY DESIGN: Experimental study. ANIMALS: Forty healthy dogs randomly assigned to 4 groups: propofol with saline (n = 10), propofol with doxapram (n = 10), methohexital with saline (n = 10), or methohexital with doxapram (n = 10). METHODS: Propofol and methohexital were administered to effect. Investigators examined laryngeal function (initial) simultaneously with video laryngoscopy. Doxapram or saline was administered, and laryngeal function was reevaluated (second). Laryngeal motion, quality of laryngeal exposure, and the degree of swallowing, laryngospasm, and jaw tone were scored at each evaluation. Adverse events were recorded. Initial and second videos were evaluated by a masked observer, and still images obtained from both evaluations were evaluated for change in rima glottidis size by 2 masked observers. RESULTS: Administration of doxapram and saline was delayed with propofol (P = .001). Laryngeal function did not differ between dogs receiving propofol or methohexital, irrespective of doxapram administration. Doxapram improved breathing scores in both groups (P < .001). Jaw tone increased with propofol during the second evaluation (P = .049). Swallowing was more prevalent at initial examination (P = .020). Methohexital resulted in an increased heart rate (P < .001) compared with propofol. Twenty‐five percent of dogs receiving methohexital developed seizure‐like activity (n = 5/20). CONCLUSION: Evaluation of laryngeal function did not differ between healthy dogs anesthetized with propofol or methohexital. Methohexital provided shorter examination times with less jaw tone but was associated with adverse events. CLINICAL SIGNIFICANCE: This study provides evidence to recommend propofol over methohexital as an induction agent for laryngeal function examination.