Myoelectric and mechanical changes elicited by ischemic preconditioning in the feline hindlimb

Tourniquet use is fraught with potential complications. For example, ischemia produced by the tourniquet may lead to nerve and muscle injuries. One technique shown in cardiovascular and free-flap surgery to improve the viability of muscle subjected to ischemia is preconditioning. This technique involves an initial brief period of ischemia, followed by reperfusion before a prolonged ischemic episode. The purpose of this study was to explore ischemic preconditioning as a method to reduce tourniquet-related morbidity. In six cats, one leg was preconditioned by 10 min of tourniquet-induced ischemia followed by 10 min of reperfusion. The contralateral limb was not preconditioned. Both limbs underwent 1 h of tourniquet inflation followed by a 2-h recovery period. Isometric force and electromyographic (EMG) amplitude were recorded throughout the procedure at 20-min intervals in both medial gastrocnemius muscles. Analysis of variance (ANOVA) with repeated measures shows that, after 60 min of tourniquet application, maximal isometric force was significantly larger in the preconditioned group. Furthermore, the EMG amplitude during recovery was found to be significantly larger in the preconditioned limbs. These results suggest that preconditioning improves skeletal muscle viability in vivo. Further research is needed, however, to assess the long-term effects of this technique, and to delineate appropriate preconditioning protocols that would improve surgical outcome without significantly increasing the complexity of the procedures.