Enhanced thromboxane synthesis with extradural anaesthesia.

Abstract

Reperfusion of a limb following tourniquet ischaemia increases plasma concentrations of thromboxane (TxB2). The study examined TxB2 production during the ischaemia and reperfusion of femoral-popliteal bypass surgery and the effect of anaesthetic technique. Patients (n = 19) were randomly allocated to receive either general (GA) or extradural (EA) anaesthesia. TxB2 concentrations were similar both before and after anaesthesia in the two groups. Clamping the femoral artery in patients given GA resulted in a small but insignificant increase in TxB2 concentration. However, in the EA group clamping resulted in a 10-fold increase in TxB2 concentration (P less than 0.05). To demonstrate that anaesthesia itself was not the stimulus to TxB2 synthesis, patients undergoing inguinal herniorrhaphy (n = 13) received either GA or EA. There were no subsequent changes in TxB2 concentrations in each group. The results indicate that EA but not GA maintains collateral flow during femoral arterial clamping and provides the oxygen needed for generation of TxB2 during ischaemia.