The proposal is designed to clarify: a. The specificity and sensitivity of angiographic abnormalities in the diagnosis of nonocclusive intestinal ischmia (NII). b. The value of angiography, particularly vasodilator pharmacoangiography, in recognizing mucosal or transmural infarction. c. The value of selective vasodilator infusion in preventing or treating NII. d. The role of mesenteric venous catheterization, venography, and biochemical assay. A canine model of NII will be developed, using hemorrhagic hypotension and intravenous Oaubain. Arteriography will be performed before and at intervals up to 72 hours after onset of hypotension. Vasodilated arteriography with papaverine will be performed at intervals to determine the prognostic significance of vasodilator response. Arterial flow rates will be determined by spill back techniques. Subgroups of dogs will have: a. Selective infusions of vasodilator into an ileal branch during or immediately after cessation of hypotension, or b. Percutaneous catheterization of the superior mesenteric vein with control and interval sampling for: 1. A-V O2 difference; 2. Levels of acid phosphatase, ribonuclease or other enzymes or metabolites.