Haemodynamic effects of subarachnoid blockade: 20% lignocaine versus 0.5% plain bupivacaine.

BACKGROUND: Our study compared the haemodynamic changes after spinal anaesthesia with 2% lignocaine and 0.5% plain bupivacaine. METHODS: A controlled, randomized trial was performed on 30 patients scheduled for arthroscopic knee surgery. Two percent lignocaine and 0.5% plain bupicacaine was used for spinal anesthesia. We measured cardiac output, blood pressure and level of sensory blockade before and for 25 minutes after spinal anaesthesia. RESULTS: In patients developing sensory block below T6 there were no differences between the study drugs in heamodynamic measurements. In patients who developed a sensory block at or above T6 there was a greater drop in mean arterial pressure and cardiac output and a faster decrease in heart rate in patients receiving bupivacaine. CONCLUSION: In patients developing a sensory block at or above the T6 dermatome, the decrease in cardiac output and mean arterial pressure in the first 25 min. after spinal anaesthesia is smaller if 2% lignocaine rather than 0.5% bupivacaine is used for blockade.