HEMODYNAMIC AND ANESTHETIC EFFECTS OF ETOMIDATE INFUSION IN MEDETOMIDINE-PREMEDICATED DOGS

Hemodynamic and analgesic effects of medetomidine (15 mu g/kg of body weight, IM) and etomidate (0.5 mg/kg, IV, loading dose; 50 mu g/kg/min , constant infusion) were evaluated in 6 healthy adult Beagles. Instru mentation was performed during isoflurane/oxygen-maintained anesthesia . Before initiation of the study, isoflurane was allowed to reach end- tidal concentration less than or equal to 0.5%, when baseline measurem ents were recorded. Medetomidine and atropine (0.044 mg/kg) were given IM after recording of baseline values. Ten minutes later, the loading dose of etomidate was given IM, and constant infusion was begun and c ontinued for 60 minutes. Oxygen was administered via endotracheal tube throughout the study. Analgesia was evaluated by use of the standard tail clamp technique and a direct-current nerve stimulator. Sinoatrial and atrial-ventricular blocks occurred in 4 of 6 dogs within 2 minute s after administration of a medetomidine-atropine combination, but dis appeared within 8 minutes. Apnea did not occur after administration of the etomidate loading dose. Analgesia was complete and consistent thr oughout 60 minutes of etomidate infusion. Medetomidine significantly ( P < 0.05) increased systemic vascular resistance and decreased cardiac output. Etomidate infusion caused a decrease in respiratory function, but minimal changes in hemodynamic values. Time from termination of e tomidate infusion to extubation, sternal recumbency, standing normally , and walking normally were 17.3 +/- 9.4, 43.8 +/- 14.2, 53.7 +/- 11.9 , and 61.0 +/- 10.9 minutes, respectively. All recoveries were smooth and unremarkable. Me concluded that this anesthetic drug combination, at the dosages used, is a safe technique in healthy Beagles.