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Cortisol suppression in cats after induction of anesthesia with etomidate, compared with ketamine-diazepam
1Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
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, i.v.; n = 8) or a mixture (KD, n = 7) of ketamine (5 mg/kg; i.v) and diazepam (0.25 mg/kg, i.v.). Anesthesia was maintained with halothane in all cats for 2 hours. ACTH gel (2.2 U/kg, i.m.) was administered 30 minutes after anesthesia induction. Blood samples for cortisol assay were taken before anesthesia induction (T -30), and before (T0) 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] micrograms/dl) at T0, compared with T -30 values and with T0 values in the KD group (5 [3 to 9] micrograms/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] micrograms/dl) remained significantly lower than values in the KD group (9 [7 to 11] micrograms/dl) and preanesthesia values. By T300, both groups had cortisol concentration near 7 micrograms/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.