Lower limb blood flow during transurethral resection of the prostate under spinal or general anaesthesia

Using venous occlusion impedance plethysmography, leg blood flow was measured in seventeen men undergoing transurethral prostatectomy under either amethocaine spinal anaesthesia (SAB) or nitrous oxide-halothane general anaesthesia (GA). Mean leg blood flow doubled (206% of pre-operative control value) following induction of SAB, remained elevated throughout surgery (146% of control at the end of operation) and had returned to pre-operative levels (94%) by two hours postoperatively. Under GA, mean blood flow rose gradually during surgery to 136% of control by the end. However, mean blood flow was only 28% of control at one hour postoperatively, rising to 66% of control by two hours. Analysis of variance showed a significant difference in blood flow changes between the two groups (Greenhouse Geisser P = 0.005). The early postoperative fall in leg blood flow in the GA group might be important in the aetiology of postoperative deep vein thrombosis.