 4. Cardiopulmonary bypass: the venous reservoir of the cardiopulmonary bypass circuit will be primed with 2L of crystalloid solution Plasma-lyteR Baxter Healthcare and maintained at a temperature of 35 degrees Celsius. Cardiopulmonary bypass will be performed in a standardized technique with cannulation of the ascending aorta and with a single two-staged right atrial-caval cannula with non-assisted venous drainage. After initiation of cardiopulmonary bypass the patients nasopharyngeal temperature will be allowed to drift progressively down to 34 degrees Celsius at which point it will be maintained by a heat exchanger until rewarming is initiated. Patients haemoglobin will be maintained above 70 gl. The ascending aorta will be cross-clamped and cardiac arrest will be induced by administration of tepid blood cardioplegia at a temperature ranging from 20-25 degrees Celsius. The ratio of blood to the initial crystalloid cardioplegia required to achieve arrest will be 4:1 in order to obtain a potassium concentration in the induction cardioplegia of at least 20 mmoll. Arrest will be achieved by antegrade administration of cardioplegia through an aortic root catheter, followed by retrograde administration through a coronary sinus catheter. Left ventricular distension will be monitored for by transoesophageal echocardiography. Further doses of maintenance cardioplegia are given following completion of graft anastomoses. Rewarming of the patient will commence at the beginning of the last distal anastomosis or 15 minutes prior to aortic cross clamp removal. The temperature of the heat exchanger used to achieve this will not exceed 37 degrees Celsius. Atrial pacing wires will be attached if electrical activity has not been established after 5 minutes of reperfusion or if pre-operative heart rate is less than 60 per minute or if the patient is on B-adrenergic antagonists. The patient will remain on full cardiopulmonary bypass support for a period of time approximately equal to 20-25 of cross clamp time or until the anaesthetist, perfusionist, and surgeon are satisfied that cardiac function is appropriate to achieve separation. 