MIDAZOLAM IN COMBINATION WITH FENTANYL FLUANISONE AND NITROUS-OXIDE AS ANESTHESIA IN RABBITS - CARDIOVASCULAR PARAMETERS/

When establishing a rabbit model for cardiovascular research in our la boratory we have used midazolam in combination with fentanyl/fluanison e (MFF) and nitrous oxide as anaesthesia. In this study we focused on the effect of the anaesthetic regimen on cardiovascular parameters dur ing open-chest surgery in 12 rabbits. Rabbits were tranquillized by in tramuscular injection of fentanyl/fluanisone (0.2 ml/kg of the drug th at contained 10 mg/ml fentanyl and 0.2 mg/ml fluanisone). After an int raperitoneal injection of midazolam (4 mg/kg) and additional i.m. inje ction of fentanyl/fluanisone (0.1 ml/kg) the rabbits were tracheotomiz ed and ventilated on a respirator delivering a gas mixture of 50% N2O, 47.5% O-2, and 2.5% CO2. The femoral vein and artery were cannulated and then rabbits received a supply of MFF intravenously. The chest was opened by midline sternotomy and the left ventricle was instrumented with piezo-electric crystals for measurement of regional left ventricu lar function and with a pressure catheter to measure left ventricular pressure. Radiolabelled microspheres were used to assess cardiac outpu t and left ventricular tissue blood now. Blood gas analysis showed no difference in the values of pH, pCO(2) and pO(2) between the open-ches t and the closed-chest states. Mean aortic pressure was 74 +/- 4 mmHg in the closed-chest state and 65 +/- 4 mmHg in the open-chest state. T issue blood flow showed that the left ventricle was well perfused, and mean tissue blood flow values varied between 1.80 and 2.36 ml/min . g . We conclude that the anaesthetic regimen used is easy to control. It is well tolerated in rabbits and is suitable for studies on myocardia l contraction in rabbits.