Skeletal muscle blood flow after prolonged tourniquet ischaemia and reperfusion with and without intervening reoxygenation: an experimental study in rats using laser Doppler perfusion imaging.

Abstract

The total, safe, time available for operating during tourniquet ischaemia is thought to be prolonged by short, intervening episodes of reperfusion. However, animal experiments have suggested that this may cause a reduction of the postischaemic reperfusion injury. The purpose of the present study was to investigate the effect on final postischaemic reperfusion of intermittent, short periods of reperfusion compared with that of prolonged, continuous tourniquet ischaemia. A rat tourniquet model of total limb ischaemia and laser Doppler imaging to measure postischaemic microvascular perfusion in skeletal muscle was used in a total of 25 anaesthetised rats. Four were non-ischaemic controls. In 21 rats one hind leg was made totally ischaemic by a tourniquet. Fourteen were exposed to uninterrupted periods of either 1.5 hours or three hours, and seven to interrupted total ischaemia of three hours, with a 20 minutes reperfusion interval after 1.5 hours of ischaemia. The postischaemic blood flow was monitored 20 minutes after release of the tourniquet. Postischaemic skeletal muscle blood flow was significantly reduced after three hours of continuous ischaemia compared with the group that had an intervening short period of reoxygenation. The postischaemic reperfusion after three hours of ischaemia with a short reperfusion interval was not reduced after ischaemia compared with either that in controls or to that in the group exposed to only 1.5 hours of tourniquet ischaemia. These findings support the clinical practice of using intervening periods of reperfusion to prolong the total tourniquet time that can safely be used. There were no adverse effects on postischaemic reperfusion from intermittent reoxygenation.