Controlled Reperfusion Reduces Reperfusion Injury in Skeletal Muscle After Incomplete Limb Ischemia

Abstract

Systemic and local complications occur after revascularization of extremities exposed to prolonged complete ischemia. Recently the authors demonstrated in experimental and clinical studies that these deleterious effects after normal blood (uncontrolled) reperfusion could be reduced significantly by controlling the composition of the reper fusate (calcium, pH, amino acids, osmolarity, and glucose) and the circumstances of the reperfusion (time, temperature, and pressure; controlled reperfusion) after complete prolonged limb ischemia. In this study the authors test the hypothesis that controlled reperfusion also has a beneficial effect and is safe to apply after a period of six hours of incomplete limb ischemia. Ten adult German house swine were exposed to six hours of incomplete limb ischemia by occlusion of the left iliac artery. This resulted in a significant reduction of limb tissue temperature (P < 0.0003, ANOVA), pH, (P < 0.0003, ANOVA), and adenosine triphosphate (ATP) (P < 0.0003, ANOVA), as well as in increased levels of (continued on next page) (Abstract continued) creatine kinase (CK) in the systemic venous (P < 0.003, ANOVA) and in the femoral vein blood (P < 0.03 ANOVA). To simulate the clinical situation of embolectomy in 5 pigs the authors released the occlusive snares after the ischemic period and let the normal blood flow with systemic pressure occur (uncontrolled reperfusion). In the other 5 pigs (controlled reperfusion) they delivered a controlled reperfusate by with drawing blood from the aorta and mixing it with a crystalloid solution (calcium reduced, hyperosmolaric, hyperglycemic, alkalotic, glutamate and aspartate enriched, and containing a free radical scavenger) under controlled conditions (ratio blood:crys talloid solution 6:1, for thirty minutes, reperfusion pressure < 50 mmHg, and normoth ermia) before establishing normal blood reperfusion. During the initial reperfusion (measured at five minutes after start of reperfusion) the group with controlled reperfusion (as compared with the animals with uncontrolled reperfusion) showed higher oxygen consumption (32.7 ±3.4 vs 15.8 ±1.9 mL/100g/min, P < 0.01, ANOVA), higher glucose consumption (439.0 ±115.7 vs 16.5 ±4.7 mg/100g/min, P < 0.03, ANOVA), less vascular resistance (19.2 ±2.8 vs 31.4 ±2.1 dyn x sec/cm5, P < 0.03, ANOVA) as well as less lactate dehydrogenase (LDH; 286.2 ±38.2 vs 604.6 ±30.7 U/L, P < 0.0003, ANOVA) and creatine kinase (CK; 294.2 ±73.0 vs 602.8 ±85.5 U/L, P < 0.03, ANOVA) concentration in the femoral vein blood. At the end of the observation period (measured at ninety minutes after start of reperfusion), the group with controlled reperfusion showed less tissue water content (81.8 ±0.7 vs 84.3 ±0.7%, P < 0.05, ANOVA), higher tissue ATP content (17.0 ±2.4 vs 9.7 ±4.3 μ Mol/g protein, ns), higher tissue ATP increase as compared with end ischemic values (6.1 ±1.5 vs -2.5 ±1.8 μMol/g protein, P < 0.03, ANOVA), higher tissue pH (7.2 ±0.1 vs 6.8 ±0.1, P < 0.03, ANOVA), less temperature decrease (0.3 ±0.2 vs 1.2 ±0.3°C, P < 0.05, ANOVA), less reduction of flow in the limb (0.2 ±0.2 vs -1.3 ±0.4 mL/100g/min, P < 0.03, ANOVA), less vascular resistance (16.7 ±1.2 vs 22.8 ±1.5 dyn x sec/cm 5, P < 0.03, ANOVA), less CK (355.0 ±87.5 vs 624.4 ±73.4 U/L, P < 0.05, ANOVA) and LDH (369.5 ±42.5 vs 538.4 ±39.1 U/L, P < 0.03, ANOVA) concentration in the femoral vein blood as well as less CK (335.0 ±89.0 vs 595.8 ±76.6, P < 0.05) and LDH (356.5 ±48.9 vs 546.0 ±37.8 U/L, P < 0.0003, ANOVA) concentration in the central venous blood. These data indicate that severe local and systemic damage occurs with uncontrolled (normal blood) reperfusion even after incomplete limb ischemia and that these reper fusion changes can be reduced significantly by delivering a controlled reperfusate under controlled conditions without any observable negative side effects. They confirm the results with controlled limb reperfusion after prolonged complete limb ischemia (aortic occlusion), and this concept has already been successfully applied in 15 patients with complete and incomplete limb ischemia as long as eighteen hours.