CARDIOVASCULAR REFLEX RESPONSES TO ISCHEMIA DURING OCCLUSION OF CELIAC AND OR SUPERIOR MESENTERIC-ARTERIES/

Global abdominal visceral ischemia leads to profound cardiovascular re flex adjustments. However, the separate contributions of the celiac ar tery and superior mesenteric artery (SMA) vascular beds to this reflex are unknown. Accordingly, we compared the effects of single and combi ned occlusions of these vessels on blood pressure (BP) in anesthetized cats. Tissue mass and pH of selected organs, regional blood gases, pH , and lactate also were measured as potential contributing factors. Oc clusion of the SMA or celiac artery produced significantly (P < 0.05) different increments in BP (30 +/- 4 vs. 18 +/- 4 mmHg, respectively). Combined occlusion of the two vessels augmented BP by 53 +/- 12 mmHg, a significantly greater increase than during celiac ligation. Venous lactate levels increased significantly during SMA, but not celiac, occ lusion, and the decline in venous pH was significantly greater in the SMA than in the celiac vascular bed (-0.20 +/- 0.03 vs. -0.08 +/- 0.02 pH units, P < 0.05, respectively). The decline in tissue pH of SMA-pe rfused organs during SMA occlusion was significantly greater than in c eliac-perfused organs during celiac occlusion. Conversely, tissue mass subserved by the celiac artery was significantly greater than that su bserved by the SMA (182 +/- 27 vs. 131 +/- 17 g, respectively). These data suggest that the larger cardiovascular reflex produced by SMA occ lusion compared with celiac occlusion may be related to a greater incr ease of lactic acid concentration in tissue supplied by the SMA. In ad dition, the large reflex increase in BP produced by combined occlusion of these vessels is an additive effect, presumably related to larger organ mass and recruitment of more sensory nerve fibers.