Microcirculatory effects of experimental acute limb ischaemia—reperfusion

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Abstract
Background: The object of this study was to develop an animal model in which changes in microvascular haemodynamics and leucocyte–vessel wall interactions due to acute limb ischaemia–reperfusion (I/R) can be measured in the skin. Furthermore, it was investigated whether these changes are related to local muscle injury. Methods: Male Lewis rats were subjected to unilateral limb ischaemia for 1 h (n = 8) or 2 h (n = 8) by cuff inflation, or to a sham protocol (n = 6). Intravital video microscopic measurements of leucocyte–vessel wall interactions, venular diameter, red blood cell velocity and reduced velocity (which is proportional to wall shear rate) were performed in skin venules before ischaemia and at 0·5, 1, 2, 3 and 4 h after the start of reperfusion. Oedema and leucocyte infiltration of ischaemic/reperfused skeletal muscle were quantified histologically. Results: In skin venules, both 1 and 2 h of ischaemia induced a significant increase in leucocyte rolling (six and five times baseline, respectively; P < 0·05) and adherence during reperfusion (eight and four times baseline; P < 0·05). No significant increase in muscular leucocyte infiltration was detected. After an initial hyperaemic response of 180 per cent of baseline values (P < 0·05), blood flow decreased to about 60 per cent after 4 h of reperfusion in skin venules of both experimental groups. I/R induced tibial muscle oedema, the severity of which depended on the ischaemic interval (wet to dry ratio: control, 4·0; 1 h, 4·5 (P not significant); 2 h, 5·8 (P < 0·05)). Conclusion: A non-invasive animal model was developed that enables investigation of the consequences of acute limb I/R.