A new model for intestinal ischemia in the rat.

Many models of intestinal ischemia in the rat have been described yielding mortality rates of 8-80% following superior mesenteric artery (SMA) occlusion for periods of 1-85 min. These results have been difficult to reliably reproduce in our lab. Based on our theory that these inconsistent findings are secondary to individual variability in collateral circulation, we have developed a new model for intestinal ischemia with reproducible and consistent mortality. Male Sprague-Dawley rats weighting 300-400 g underwent celiotomy and evisceration. Occlusion of the superior mesenteric artery just distal to the right colic artery was achieved. Collateral arcades from the right colic artery and the jejunal arteries proximal to the site of occlusion were ligated and the bowel was returned to the abdomen for the remainder of the ischemic period. SMA occlusion alone and SMA occlusion with interruption of collateral flow were evaluated and compared for severity of ischemic injury reflected by mortality and for reproducibility of ischemia and mortality. Quantitative measurements of blood flow for each technique were made using radiolabeled microspheres, and a survival curve for SMA occlusion with collateral ligation was constructed. SMA occlusion alone in the rat is not a reliable model for mesenteric ischemia because the resulting ischemic injury is inconsistent and not reproducible. SMA occlusion with collateral ligation produced more severe and reproducible ischemia with greater mortality than did SMA occlusion alone. This technique produced mortality rates that were reproducible and were more consistently related to duration of ischemia.