Histopathology of muscle flap microcirculation following prolonged ischemia.

The purpose of this study was to evaluate histological changes occurring in the microcirculation of a muscle flap following prolonged ischemia and to correlate them with the flow hemodynamics. The cremaster muscle flap model was used for direct in vivo studies of the microcirculation. In 45 rats, vascular clamps were applied to the iliac and femoral vessels following flap isolation. Flaps were subjected to various periods of ischemia, ranging from 4 to 6 hours, and 2 hr of reperfusion. In vivo observations of the microcirculation and vessel diameter measurements were taken at 1 hour intervals for an 8 hr period. With prolonged ischemia, return of circulation to the flap was delayed and no flow was observed following 6 hr of ischemia. Morphologic changes at 6 hr revealed red cell and platelet thrombi formation within the capillaries, marked dilatation of postcapillary venules, endothelial swelling in the capillaries, and microhemorrhage formation around the venules.