Protective effect of ischaemic preconditioning against ischaemia-induced reperfusion injury of skeletal muscle: how many preconditioning cycles are appropriate?

We investigated the efficacy of ischaemic preconditioning (IPC), consiting of repeated brief episodes of vascular occlusion followed by reperfusion, as protection against ischaemia-reperfusion injury of skeletal muscle, using a rat amputation-like model. Wistar rats underwent temporary amputation at the level of the femur, excluding the femoral vessels. The femoral artery and wein were clamped for 4h, using a micro-clamp, in the groups exposed to ischaemia. The rats were randomly divided into eight groups: a control (C) group (n=7) with non-amputated and non-ischaemic hind limbs; a sham control (SC) group (n=7) with amputated but non-ischaemic hind limbs; an ischaemia-reperfusion (IR) group (n=7) with amputated and ischaemic hind limbs; and five IPC groups (n=7 in each) with hind limbs that were subjected to 4h of ischaemia after one to five cycles of brief ischaemia and reperfusion for 10 min each, respectively. All rats were sacrificed 24 h after reperfusion. The, viability of the anterior tibial muscles was evaluated using nitroblue tetrazolium staining. The total viable area ratio (T-VAR) of the muscle tissue was calculated in each animal as follows: T-VAR=total viable area/total slice area x 100%. The T-VAR values of the eight groups were as follows: C group, 100%+/-0%; SC group, 100%+/-0%; IR group, 73.5%+/-1.7%; IPC1 group, 79.4%+/-6.5%; IPC2 group, 70.5%+/-6.2%; IPC3 group, 90.6%+/-2.8%; IPC4 group, 90.0%+/-1.6%; and IPC5 group, 87.8%+/-1.8%. The T-VARs in the IPC3, IPC4 and IPC5 groups were significantly higher (@a<0.01) than those in the IR group. In contrast, there were no significant differences between the T-VARs of the IPC1 and IPC2 groups and those of the IR group. In conclusion, three to five cycles of IPC could protect skeletal muscle against ischaemia. le against ischaemia. 2002 The British Association of Plastic Surgeons