Effects of muscle relaxants on ischaemia damage in skeletal muscle

Muscle ischaemia is frequently induced intraoperatively by i.e. a surgical tourniquet or during the re-grafting phase of a free muscle transplant. The resulting muscle cell damage may impact on postoperative recovery. Neuromuscular paralysis may mitigate the effects of ischaemia. After ethics approval, 25 male Sprague-Dawley rats were anaesthetized and randomly assigned to 1 of 4 groups: Sham operation, treatment with normal saline, treatment with rocuronium (muscle relaxant) 0.6 or 1 mg kg^-1, respectively. In the non-sham groups, ischaemia of one hind leg was achieved by ligation of the femoral vessels. Muscle biopsies were taken at 30 and 90 min, respectively. Cell damage was assessed in the biopsies via the expression of dystrophin, free calcium, as well as the assessment of cell viability. Pre-ischaemia muscle relaxation led to a reduction in ischaemia-induced muscle cell damage when measured by the expression of dystrophin, cell viability and the expression of free calcium even after 90 min of ischaemia (i.e. ratio control/ischaemic site for dystrophin expression after saline 0.58 ± 0.12 vs. after 1 mg/kg rocuronium 1.08 ± 0.29; P < 0.05). Muscle relaxation decreased the degree of ischaemia-induced muscle cell damage. The results may have significant clinical implications.