Extent of Ischemia in Skeletal Muscle Compared during Circulatory Occlusion and Exsanguination Korth et al.(page 1407)
In 18 patients scheduled to undergo elective surgery of the lower limb, Korth et al. obtained permission to insert microdialysis probes into both quadriceps femoris muscles to quantify the extent of ischemia produced by use of a tourniquet. The probes on the side of surgery were placed midline 2 cm below the tourniquet, and the probes on the opposite leg served as controls. The probes were perfused at a rate of 2 μl/min with sterile Ringer’s solution. Samples were collected on ice at 15-min intervals and stored for later analysis. Blood samples were obtained from the femoral vein before ischemia and at 2, 60, and 120 min after deflation of the tourniquet.
The patients were assigned to one of two groups. One group underwent surgery under circulatory occlusion, with the leg elevated for a few minutes followed by tourniquet inflation to a pressure of 380 mmHg to surpass arterial blood pressure. In the second group, the leg was elevated and exsanguination was accomplished with use of an elastic Esmarch bandage wrapped around the ankle and rolled toward the body, followed by tourniquet inflation to 380 mmHg and removal of the bandage.
At a flow rate of 2 μl/min, average baseline concentrations in the dialysate were 2.5 mm for glucose, 1.7 mm for lactate, 5.2 μm for choline, and 14.3 μm for hypoxanthine. Within 30 min of circulatory occlusion by tourniquet, extracellular glucose concentrations decreased 40%. At the same time, interstitial levels of lactate and hypoxanthine increased in linear fashion to 206% and 241% of baseline levels, respectively. These indicators of tissue ischemia change were even more increased after exsanguination—to 268% of baseline for lactate and to 286% of baseline for hypoxanthine. The authors conclude that circulatory occlusion is less demanding on muscle tissue than is exsanguination.