Impact of gradual blood flow increase on ischaemia-reperfusion injury in the rat cremaster microcirculation model.

Introduction: We aimed to evaluate the impact of gradual blood reperfusion on ischaemia-reperfusion injury and to explain the pathophysiology of reperfusion injury in a rat cremaster muscle microcirculation model.

Materials And Methods: Twenty-four Sprague-Dawley rats weighing 150-200 g were evaluated in three groups. Cremaster muscles were prepared for microcirculatory observations. Group I (n=8, control): no ischemia was induced. Group II (n=8, acute reperfusion): microclamps were applied to the right external iliac vessels for 150 min, then venous and arterial clamps were released at once. Group III (n=8, gradual reperfusion): microclamps were applied to the right external iliac vessels for 150 min, and then the first venous clamp was released; the arterial clamp was opened gradually by a specially designed microclamp holder (Sheey ossicle holding clamp). In all groups, following a wait of 150 min blood flow velocity was measured for 15 min and then the animals were reperfused freely for 1h. Next, red blood cell velocity, vessel diameters, functional capillary perfusion and endothelial oedema index were analysed, and rolling, migrating and adhesing leukocytes and lymphocytes were counted. All observations were videotaped for slow-motion replay. Muscle damage was evaluated histologically.

Results: In the acute clamp release group, blood velocities increased up to 600% of their pre-ischaemic values during the post-ischaemia-reperfusion period. The numbers of rolling, adhering and transmigrating leukocytes were significantly higher and histological evaluation revealed more tissue damage in the acute reperfusion group.

Conclusion: Depending on histological and microcirculatory findings, gradual reperfusion was confirmed to reduce the intensity of reperfusion injury.