Regional hypothermia protects against tourniquet neuropathy

Ischaemic nerve injury has been suggested as the mechanism for post-tourniquet limb paralysis. As hypothermia has been shown to prolong ischaemia time in many tissues, we tested the hypothesis that cold protection would reduce tourniquet induced neural injury. In 16 male Wistar rats a tourniquet was applied to the right hind limb for 3 h. In eight rats both hind limbs were maintained at room temperature (27°C) while the limb temperature was decreased to 4°C by application of cold polyglycol gel packs in the remaining eight animals. Motor nerve conduction velocity (MNCV) and the amplitude of muscle motor units (AMMU) in response to nerve stimulation were measured at Oh, 1 h and 1 week post-tourniquet release. Application of the tourniquet for 3 h abolished nerve conduction in all animals. Hypothermia resulted in a significant improvement in AMMU (5.8 ± vs. 0.6 ± 0.4mv, p < 0.05) at 1 h and in MNCV (26.6 ± 1.6 vs. 8.1 ± 4.4ms^-1, p < 0.05) and AMMU (18.5 ± 2.0 vs. 9.7 ± 4.5mv, p < 0.05) at 1 week. Hypothermia without ischaemia also reduced MNCV (44.2 ± 9.4 vs. 74.3 ± 8.9ms^-1, p < 0.05) and AMMU (28.1 ± 2.8 vs. 36.3 ± 8.4mv, n.s.). These data indicate that hypothermia reduces normal MNCV and protects nerve function during tourniquet ischaemia. These results support the ischaemic hypothesis for post-tourniquet nerve injury. Cold protection may have clinical applications for surgical procedures performed with tourniquet ischaemia.