Rabbit model of cardiopulmonary bypass

Mainly because of technical problems, the use of rabbits as a cardiopulmona ry bypass (CPB) animal model with direct cannulation of the ascending aorta is known to be extremely difficult. The objectives of this study were the establishment of a CPB model in rabbits with direct cannulation of the asce nding aorta, and the evaluation of the protective effect of steroid on the development of brain edema during circulatory arrest (CA) in an established rabbit CPB model. Fifteen New Zealand white rabbits were divided into thre e groups; control CA group, CA with Trendelenberg position, and CA with Tre ndelenberg position and steroid administration. After anesthetic induction and tracheostomy. median sternotomy was performed. An aortic cannula (3.3 m m) and a venous cannula (14 Fr) were inserted into the ascending aorta and the right atrium. respectively. The CPB circuit consisted of a roller pump and a bubble oxygenator. With 120-150 ml of blood, the priming volume of th e circuit was approximately 450 ml, and CPB at a flow rate of 80-85 ml/kg/m in was initiated. Blood in the priming solution was obtained from donor rab bits through cardiac puncture. Ten minutes later. CA with cessation of CPB was established for 40 min at 20 degrees C (rectal temperature). After CA, CPB was restarted with a 20 min period of rewarming. Ten minutes after wean ing, the animal was sacrificed. Between 1 and 2 g of the brain was removed and the water content was determined and compared between groups. CPB with CA was successfully performed in all cases, with a flow rate of 60-100 ml/k g/min maintained throughout the! CPB procedure. At that time, blood gases w ere reasonably maintained and aortic pressure ranged from 35 to 55 mmHg. Af ter weaning from CPB, all hearts resumed beating spontaneously. Among the t hree groups, there were no statistically significant differences in the wat er content of the brain. These results indicate that: (1) if the proper tec hnique is used, CPB in rabbits with direct cannulation of the ascending aor ta is a reliable procedure, and (2) the effect of steroid on the prevention of brain edema related to the Trendelenburg position during CA is not esta blished within the scope of this study.