The combined influence of hemorrhage and tourniquet application on the recovery of muscle function in rats.

OBJECTIVE The objective of this study was to compare the effect of tourniquet-induced ischemia/reperfusion (I/R) injury on the recovery of muscle function with and without prior hemorrhage. METHODS Male Sprague-Dawley rats (initially 400-450 g) were randomly assigned to 1 of 4 groups (n=8 per group): (1) hemorrhage (33% of estimated blood volume) plus tourniquet +H/+TK; (2) tourniquet alone (-H/+TK); (3) hemorrhage alone (+H/-TK); and (4) surgical control (-H/-TK). A pneumatic tourniquet was applied to the upper leg for 4 hours, followed by 2 weeks of recovery. For +H animals, tourniquets were applied at the conclusion of blood withdrawal. The predominantly fast-twitch plantaris and the predominantly slow-twitch soleus muscles were examined using in situ isometric muscle function 2 weeks following treatment. RESULTS Tourniquet application resulted in significantly greater loss of force production [peak tetanic force (Po)] in the plantaris compared with the soleus. The decrease in Po was a result of both a loss of muscle mass and a reduction in specific force [force per unit weight; Po (n/g)]. Hemorrhage prior to tourniquet application significantly increased the extent of functional loss compared with tourniquet alone in the plantaris but not the soleus. Hemorrhage prior to tourniquet application significantly reduced the rate of postsurgical recovery of body weight. CONCLUSION The functional loss resulting from tourniquet application is exacerbated by the superimposition of hemorrhage in the predominantly fast-twitch plantaris but not the predominantly slow-twitch soleus. This was likely a result of metabolic derangement resulting from the combination of hemorrhage and tourniquet application. The development of interventions designed to attenuate the loss of muscle mass and function following complex trauma is necessary for optimal patient recovery.