RESUMO
INTRODUCTION: The use of rabbits as a cardiopulmonary bypass(CPB) animal model is extremely difficult mainly due to technical problems. On the other hand, deep hypothermic circulatory arrest(CA) is used to facilitate surgical repair in a variety of cardiac diseases. Although steroids are generally known to be effective in the treatment of cerebral edema, the protective effects of steroids on the brain during CA are not conclusively established. Objectives of this study are twofold: the establishment of CPB technique in rabbits and the evaluation of preventive effect of steroid on the development of brain edema during CA. MATERIAL AND METHODS: Fifteen New Zealand white rabbits(average body weight 3.5kg) were divided into three experimental groups; control CA group(n=5), CA with Trendelenberg position group(n=5), and CA with Trendelenberg position + steroid(methylprednisolone 30 mg/kg) administration group(n=5). After anesthetic induction and tracheostomy, a median sternotomy was performed. An aortic cannula(3.3mm) and a venous ncannula(14 Fr) were inserted, respectively in the ascending aorta and the right atrium. The CPB circuit consisted of a roller pump and a bubble oxygenator. Priming volume of the circuit was approximately 450ml with 120~150ml of blood. CPB was initiated at a flow rate of 80~85ml/kg/min. Ten min after the start of CPB, CA was established with duration of 40min at 20 degrees C of rectal temperature. After CA, CPB was restarted with 20min period of rewarming. Ten min after weaning, the animal was sacrificed. One-to-2g portions of the following tissues were rapidly dissected and water contents were examined and compared among groups: brain, cervical spinal cord, kidney, duodenum, lung, heart, liver, spleen, pancreas, stomach. Statistical significances were analyzed by Kruskal-Wallis nonparametric test. RESULTS: CPB with CA was successfully performed in all cases. Flow rate of 60-100 ml/kg/min was able to be maintained throughout CPB. During CPB, no significant metabolic acidosis was detected and aortic pressure ranged between 35-55 mmHg. After weaning from CPB, all hearts resumed normal beating spontaneously. There were no statistically significant differences in the water contents of tissues including brain among the three experimental groups. CONCLUSION: These results indicate (1) CPB can be reliably administered in rabbits if proper technique is used, (2) the effect of steroid on the protection of brain edema related to Trendelenburg position during CA is not established within the scope of this experiment.