The Effect of gradual increase in blood flow on ischemia-reperfusion injury in the rat hindlimb model

38 SUMMARY THE EFFECT OF GRADUAL INCREASE IN BLOOD FLOW ON ISCHEMIA- REPERFUSION INJURY IN THE RAT HTNDLIMB MODEL Introduction: Methods for reducing the production of free oxygen radicals and altering the composition of blood in order to prevent ischemia-reperfusion injury have been well-studied; however, they are still far from clinical application. There are studies on the effect of gradual reperfusion on ischemia-reperfusion injury in the myocardial muscle, and it seems to be clinically applicable, since it is a simple surgical manipulation. In this study, we aimed to investigate the effect of gradual reperfusion on ischemia-reperfusion injury in the skeletal muscle, using the rat hindlimb model. Materials and Methods: Fifteen male Wistar rats were used in three groups. In all groups, the right hindlimb of the animals were detached from the body, leaving he femoral artery and vein intact. Following a 15-minute stabilization period, pre-ischemic arterial blood flow was measured with a transonic flowmeter, in every 30 seconds during the next 5 minutes, and the mean value was taken. Group I (n=5): Control - The hindlimb of the animals were amputated, leaving the femoral artery and vein intact, but ischemia was not induced. Group II (n=5): Conventional release of the clamps - Following the stabilization period, microvascular clamps were applied on the femoral artery and vein, and the hindlimbs were subjected to 150 minutes of ischemia. At the end of the ischemic period, the clamps were released at once and post-ischemic blood flow was measured for 15 minutes. Group III (n=5): Gradual release of the clamps - The ischemia was induced as described in the previous group. At the end of the ischemic period, the arterial clamps were gradually39 Group 111 (n=5): Gradual release of the clamps - The ischemia was induced as described in the previous group. At the end of the ischemic period, the arterial clamps were gradually released by using the Sheey ossicle holding clamp. The clamps were released at a rate that the blood flow velocity would reach to the % of the mean pre-ischemic value at 30 seconds, Vi at 60 seconds, % at 90 seconds and a similar pre-ischemic value at 120 seconds. The clamps were totally released after 1 5 minutes of blood flow below the 1.5 fold of the pre-ischemic values. The animals were euthanized at 24 hours, and samples from the soleus muscle were taken for histological and biochemical evaluation. Histologically, the inflammatory cell infiltration, the loss of the lining and nuclei in the muscle and internal nuclealization was evaluated. Biochemically, the levels of malonylaldehyte and myeloperoxidase were assessed by spectrophotometric evaluation. Results: The mean pre-ischemic blood flow velocity was 13.6 ± 2.24 ml/kg/min in all groups. In the conventional release group, the post-ischemic blood flow reached 4 to 5 fold of its pre- ischemic values at 40 seconds (61.06±27,96ml/kg/min). Histopathological evaluation revealed less damage in the gradual release group comparing to the conventional release group. Similarly, the malonylaldehyte and myeloperoxidase levels were lower in the gradual release group. Conclusion: Depending on the histological and biochemical data, we have demonstrated that gradual increase in blood flow reduced the intensity of the ischemia-reperfusion injury in the muscle. Further investigation comparing the gradual reperfusion with the conventional one on various tissues and organs, is required for the future use of this technique in reconstructive microsurgery.