Cortisol suppression in cats after induction of anesthesia with etomidate, compared with ketamine-diazepam combination

Abstract

Objective - To evaluate duration and magnitude of adrenocortical function suppression after administration of etomidate to cats. Animals 15 purpose-bred, healthy cats. Procedure - Cats were allotted to 2 groups. Anesthesia was induced with etomidate (ET, 2 mg/kg of body weight, IV; n = 8) or a mixture (KD, n = 7) of ketamine (5 mg/kg, IV) and diazepam (0.25 mg/kg, IV). Anesthesia was maintained with halothane in all cats for 2 hours. ACTH gel (2.2 U/kg, IM) was administered 30 minutes after anesthesia induction. Blood samples for cortisol assay were taken before anesthesia induction (T - 30), and before (TO) and at 30, 60, 120, 180, 300, and 420 minutes after ACTH administration. Anesthesia was discontinued after the T120 sample was obtained. Results - After anesthesia induction, median (interquartile range [Q1-Q3]) cortisol values were significantly lower in the ET group (4 [3 to 4] μg/dl) at TO, compared with T -30 values and with TO values in the KD group (5 [3 to 9] μg/dl). After ACTH administration, cortisol values in the ET group continued to decrease two- to threefold below T -30 values and remained decreased over the 2-hour anesthesia period. After ACTH administration, cortisol values increased twofold for 2 hours in the KD group, compared with T -30 values. One hour after anesthesia recovery, cortisol values in the ET group (3 [2 to 3] μg/dl) remained significantly lower than values in the KD group (9 [7 to 11] μ/dl) and preanesthesia values. By T300, both groups had cortisol concentration near 7 μg/dl, similar to preanesthesia values. Conclusion - Induction of anesthesia with etomidate caused suppression of adrenocortical function during 2 hours of halothane anesthesia and 1 hour of recovery in cats. Cortisol concentration did not return to baseline until after 2 additional hours. Clinical Relevance - Results from these healthy cats suggest profound suppression of important stress hormones after anesthesia induction with etomidate, use of which could put critically ill cats at further risk.