EVALUATION OF THE MICROCIRCULATION OF THE EQUINE JEJUNUM AND ASCENDING COLON AFTER ISCHEMIA AND REPERFUSION

Intramural vascular patterns of the jejunum and colon were evaluated d uring ischemic strangulation obstruction (ISO, 70 minutes) and subsequ ent reperfusion (60 minutes) in 7 adult anesthetized horses. Microvasc ulature of experimental and control segments was described by comparis on of results from microangiography, light microscopy, and scanning el ectron microscopy of vascular replicas. Experimental and control segme nts with isolated vascular arcades were removed either immediately aft er the experimental period or after 60 minutes of reperfusion. Blood w as flushed from the vascular system by use of isotonic NaCl, and the s egments were divided. Half of each segment was perfused with a modifie d radiopaque medium for microangiographic evaluation, and half was per fused with dilute methylmethacrylate to create a vascular replica to b e studied by scanning electron microscopy. Microangiographic section a lso were evaluated for histologic changes. Microvasculature of jejunal control segments and all colon segments was similar to described norm al microvasculature of the equine jejunum and ascending colon, In jeju nal iso segments, intramural perfusion was redistributed away from the mucosa. In the villi, the central arteriole was short and convoluted and the subepithelial capillaries were not filled. The submucosal vess els and crypt capillaries were congested, compared with those of contr ols, and the serosal vessels were not filled in the ischemic segments. Histologic grade II-III mucosal lesion was seen in jejunal ISO segmen ts. Reperfused jejunal segments had a transmural hyperemic response, a nd previously unfilled capillaries were observed in all intestinal lay ers. After reperfusion, the mucosal lesion progressed to grade III-IV and a cellular infiltrate and edema formation were observed in the ser osa. The intramural vasculature of the ischemic and reperfused colon r emain unchanged. Minimal histologic damage was observed in the colon a fter 70 minutes of iso or after 60 minutes of reperfusion.