OBJECTIVES

The aim of this work was to study alterations induced by the anaesthesia with etomidate on the cardiorespiratory and biochemical parameters in diazepam or medetomidine premedicated dogs.

MATERIALS

Animals: 12 healthy Beagle dogs (5 males and 7 females), 15 ± 6 months old and body weight 14 ± 4 kg. Procedure: 6 dogs were premedicated with diazepam (0.5 mg/kg) and anaesthesia was induced with etomidate (1.5 ± 0.6 mg/kg, i.v.) followed by i.v continuous etomidate perfusion (165 ± 20 µg/kg/min), during 60 minutes. The other 6 dogs were premedicated with medetomidine (10 µg/kg, i.m.), and anaesthesia was induced with etomidate (0.5 ± 0.3mg/kg) followed by i.v. continuous etomidate perfusion (70 ± 20 µg/kg/min), during 60 minutes. Immediately after anaesthesia induction a 18 GA polyethylene catheter was placed in the femoral artery to measure the arterial blood pressure and to extract blood samples every 20 minutes, to determine the PaO2, PaCO2, pH and BE.Heart rate, SAP, MAP, DAP, RR, VT, VM, ETCO2 and SPO2 were measured in t0 and every 5 minutes, for 60 minutes. Body temperature and cortisol levels were measured before and after anesthesia. Times to induction, extubation, sternal recumbency, and walking were measured. The incidence of side effects was also studied.

RESULTS

The time to anaesthesia induction was significantly higher in the diazepam/etomidate combination. Heart rate, RR, PaCO2 and VM were significantly higher, while the values of the blood arterial pressure (mean and diastolic), VT, pH and BE were significantly smaller in the diazepam/etomidate combination respect to medetomidine/etomidate combination. There were no significant differences in mean values of the systolic pressure, PaO2, SPO2 and ETCO2 between the two combinations. There was a significant decrease of the plasma levels of cortisol and of the body temperature in both experiments. A high incidence of myoclonus and excitation as well as nausea and vomiting was observed during recovery in the diazepam/etomidate combination, when compared with weak myoclonus in medetomidine/etomidate combination. Intravascular hemolysis and hemoglobinuria were observed in both experiments. Mean times to extubation, sternal recumbency and walking were smaller in medetomidine/etomidate combination, but only the sternal recumbency time was sadistically significant.

CONCLUSION

Diazepam-etomidate combination provided more cardiorespiratory depression than medetomidine-etomidate combination. Etomidate induction and maintenance doses were greater in diazepam group.