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

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.