Absence of skeletal muscle lesions after experimental restraint stress induced by pancuronium in normal and stress-susceptible pigs

Stress-susceptible (SS) pigs develop rhabdomyolysis and increased serum levels of muscle enzymes after a 12 min experimental stress induced by the depolarizing myorelaxant succinylcholine. It is suspected that not only the stress situation but also succinylcholine itself contributes to the skeletal muscle lesions. This experiment was performed to study whether rhabdomyolysis occurs after restraint stress when succinylcholine was replaced by the nondepolarizing myorelaxant pancuronium. Four normal and four SS pigs were subjected to restraint stress by intravenous injection of pancuronium. The neuromuscular block was reversed after 12 min by neostigmine. The animals were necropsied approximately 48 h after stress and 24 skeletal muscle groups were examined pathologically. The severity of acute myofibre lesions were graded, and the results were compared with the results from normal and SS pigs which had been subjected to restraint stress induced by succinylcholine. The serum levels of creatine kinase (CK) and aspartate aminotransferase (ASAT) stayed at the base line level after the stress. The scores for muscle lesions were significantly lower, both in normal and SS pigs, than after restraint stress induced by succinylcholine indicating no rhabdomyolysis after restraint stress induced by pancuronium. Thus succinylcholine is synergistic with stress, exacerbating its effect on skeletal muscle in SS pigs.