Effects of continuous infusion of etomidate at various dose rates on adrenal function in dogs.

Background: Etomidate is a commonly used sedative in intravenous anesthesia. The aim of this study was to compare the effects of various etomidate doses administered by continuous infusion on adrenal function in dogs under general anesthesia.

Methods: Thirty-six healthy adult male dogs were randomly divided into six groups. Sodium pentobarbital alone was administered to the control group (group C); five experimental groups (E1, E2, E3, E4, and E5) were also given etomidate at doses of 10, 15, 20, 25, and 30 μg · kg(-1) · min(-1), respectively, to maintain anesthesia. Heart rate (HR), mean arterial pressure (MAP), and bispectral index (BIS) were monitored. Serum cortisol, aldosterone, adrenaline, and noradrenaline levels were measured, and HR, MAP, and BIS values recorded, before intubation (T0), and at 1 h, 2 h, and 3 h after intubation (T1-3).

Results: Cortisol and aldosterone levels in groups E1-5 decreased as the doses and times of continuous infusion of etomidate increased. The cortisol level was significantly decreased compared with baseline at T3 in group E1 and at T1-3 in groups E2-5 (P < 0.05). Compared with the corresponding levels in group C, cortisol levels were significantly lower than T0 values at T3 in group E1 and at T1-3 in groups E2-5 (P < 0.05). The aldosterone level was significantly lower at T3 in group E2 and at T1-3 in groups E3-5 (P < 0.05). Significant reductions in cortisol levels at T2-3 in group E2 and at T1-3 in groups E3-5 compared with group C were also observed (P < 0.05). The plasma adrenaline and noradrenaline levels, HR, MAP, and BIS in groups E1-5 were within the normal range at the different times and with the different doses (P > 0.05).

Conclusions: Cortisol and aldosterone levels decreased with time and continuous infusion of etomidate; there were no significant changes in adrenaline and noradrenaline levels, HR, MAP, and BIS in any group.