Background: Tourniquets are often used as part of orthopedic surgery but may cause local and remote organ injury. The authors hypothesized that the procedures used to induce ischemia (circulatory occlusion or exsanguination) may have differential effects on the metabolic state of the muscle that should be reflected in the interstitial levels of metabolites.
Methods: Microdialysis probes were implanted in both quadriceps femoris muscles of 18 patients. Interstitial fluid was obtained during tourniquet-induced ischemia and reperfusion and was analyzed for glucose, lactate, choline, and purines by high-performance liquid chromatography.
Results: At a flow rate of 2 microl/min, the average baseline concentrations in the dialysate were 2.5 mM for glucose, 1.7 mM for lactate, 5.2 microM for choline, and 14.3 microM for hypoxanthine. Circulatory occlusion by tourniquet caused a 40% decrease of the extracellular glucose concentration within 30 min. Concomitantly, the interstitial levels of lactate and hypoxanthine increased in a linear fashion to 206% (lactate) and 241% (hypoxanthine) of basal values. The extracellular concentration of choline was also significantly elevated. After exsanguination, the glucose levels were significantly more reduced (by 65%), and the levels of lactate (to 268%) and hypoxanthine (to 286%) were more increased than after circulatory occlusion alone.
Conclusion: Our microdialysis results demonstrate that the interstitial concentrations of glucose, lactate, and hypoxanthine, which are indicators of tissue ischemia, change more prominently after exsanguination than after circulatory occlusion alone.