RESUMO
This study was carried out on 20 healthy adult patients who were undergone major orthopedic surgery. Patients were premedicated by atropine sulphate and pethidine hydrochloride. Anaesthesia was induced by thiopentone sodium. Cuffed endotracheal tube was inserted after succinyl choline injection. Anaesthesia was maintained by nitrous oxide, oxygen, pancuronium and controlled ventilation. After stabilization of anaesthesia sodium nitroprusside 0.01% in 5% dextrose was infused at a rate of 20-40 drops/min.to maintain systolic blood pressure around 80 mmHg. It was found that the heart rate increased significantly and mean arterial pressure decreased significantly during infusion. The serum cortisol level was significantly increased, Pa02 was significantly decreased with a significant increase in Pac02. There were no significant change in PH, standard bicarbonate and base excess. At the end of operation, all the studied parameters returned to their preoperative values without any complication or residual effects