CORTISOL SUPPRESSION IN CATS AFTER INDUCTION OF ANESTHESIA WITH ETOMIDATE, COMPARED WITH KETAMINE-DIAZEPAM COMBINATION

Objective-To evaluate duration and magnitude of adrenocortical functio n suppression after administration of etomidate to cats. Animals-15 pu rpose-bred, healthy cats. Procedure-Cats were allotted to 2 groups. An esthesia 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 afte r anesthesia induction. Blood samples for cortisol assay were taken be fore anesthesia induction (T -30), and before (T0) and at 30, 60, 120, 180, 300, and 420 minutes after ACTH administration. Anesthesia was d iscontinued after the T120 sample was obtained. Results-After anesthes ia induction, median (interquartile range [Q(1)-Q(3)]) cortisol values were significantly lower in the ET group (4 [3 to 4] mu g/dl) at T0, compared with T -30 values and with TO values in the KD group (5 [3 to 91 mu g/dl). After ACTH administration, cortisol values in the ET gro up continued to decrease two- to threefold below T -30 values and rema ined decreased over the 2-hour anesthesia period. After ACTH administr ation, cortisol values increased twofold for 2 hours in the KD group, compared with T -30 values. One hour after anesthesia recovery, cortis ol values in the ET group (3 [2 to 3] mu g/dl) remained significantly lower than values in the KD group (9 [7 to 11] mu g/dl) and preanesthe sia values. By T300, both groups had cortisol concentration near 7 mu g/dl, similar to preanesthesia values. Conclusion-Induction of anesthe sia with etomidate caused suppression of adrenocortical function durin g 2 hours of halothane anesthesia and 1 hour of recovery in cats. Cort isol concentration did not return to baseline until after 2 additional hours. Clinical Relevance-Results from these healthy cats suggest pro found suppression of important stress hormones after anesthesia induct ion with etomidate, use of which could put critically ill cats at furt her risk.