The effect of pretreatment with ischaemic preconditioning or cromakalim onperfusion in skeletal muscle during ischaemia-reperfusion injury

Background. Ischaemia-induced damage of skeletal muscle may lead to side ef fects in orthopaedic and reconstructive surgery where tourniquet ischaemia is applied to ensure a bloodless operative field. In this study we investig ated the effect of ischaemia-reperfusion injury with and without preconditi oning by studying the skeletal muscle microcirculation. A further aim was t o establish whether ischaemic preconditioning or pretreatment with cromakal im, a potassium channel opener reduces ischaemia-reperfusion injury. Methods. Twenty-eight Wistar rats were randomised into four groups (n=7 per group). Group 1, control with no treatment; Group 2, two and a half hours tourniquet ischaemia. followed by two hours of reperfusion to the left hind limb. Furthermore, we pre-treated two groups prior to the ischaemia-reperfu sion period; Group 3 with three short cycles of ischaemia-reperfusion (5'/5 ') and Group 4 pre treated with cromakalim (100 mug/kg bw). We monitored th e gastrocnemius muscle blood flow invivo. Results. There were no significant changes in the skeletal muscle microcirc ulation and temperature at the baseline in the four groups (p=0.110). In th e ischaemic reperfusion, ischaemia preconditioning and cromakalim groups, t he recorded skeletal muscle microcirculation during ischaemia decreased sig nificantly (p <0.001) with respect to the baseline. In Group 2 the microcir culation recovered rapidly after release of the tourniquet, but was signifi cantly lower (37% of baseline value, p <0.001) within two hours of reperfus ion. In the ischaemia preconditioning group the microcirculation as in the ischaemia-reperfusion group recovered rapidly after release of the tourniqu et, although failing to reach the baseline value within two hours of reperf usion. The mean microcirculation value of the left limb was slightly higher than Group 2 but significantly lower compared to the baseline after two ho urs of reperfusion (p<0.001). The change in the skeletal muscle microcircul ation with cromakalim after two hours of reperfusion was not significant wh en compared to baseline values (p<greater than>0.05). The cromakalim group after two hours reperfusion had significantly higher microcirculation value s when compared with Groups 2 and 3 (p<0.001). During ischaemia-reperfusion in Groups 2-4, there was no significant alteration in the systemic haemody namic circulation. Conclusions. This study supports the hypothesis that cromakalim reduces pos tischaemic skeletal muscle damage and reperfusion injury.