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Cardiovascular reflex responses to ischemia during occlusion of celiac and/or superior mesenteric arteries
S V Rendig1, P S Chahal, J C Longhurst
1Department of Internal Medicine, University of California, Davis 95616, USA.
Insights
Occluding the superior mesenteric artery (SMA) causes a greater blood pressure reflex than celiac artery occlusion, likely due to increased lactic acid. Combined occlusion has an additive effect.
Area of Science:
- Physiology
- Cardiovascular Reflexes
- Gastrointestinal Ischemia
Background:
- Global abdominal visceral ischemia triggers significant cardiovascular reflex adjustments.
- The distinct roles of the celiac artery and superior mesenteric artery (SMA) vascular beds in these reflexes remain unclear.
Purpose of the Study:
- To compare the cardiovascular reflex responses to isolated and combined occlusions of the celiac artery and SMA.
- To investigate the contributions of tissue mass, pH, blood gases, and lactate to these reflexes.
Main Methods:
- Anesthetized cats underwent single and combined occlusions of the celiac artery and SMA.
- Measurements included blood pressure, organ tissue mass and pH, regional blood gases, pH, and lactate levels.
Main Results:
- SMA occlusion yielded a greater blood pressure increase (30 mmHg) than celiac artery occlusion (18 mmHg).
- Combined occlusion resulted in a significantly larger blood pressure augmentation (53 mmHg).
- SMA occlusion led to increased venous lactate and greater pH decline in SMA-perfused tissues compared to celiac occlusion.
Conclusions:
- The more pronounced cardiovascular reflex from SMA occlusion may stem from greater lactic acid accumulation in SMA-perfused tissues.
- The additive blood pressure response during combined occlusion is likely due to larger organ mass and increased sensory nerve fiber recruitment.
Abstract:
Global abdominal visceral ischemia leads to profound cardiovascular reflex adjustments. However, the separate contributions of the celiac artery and superior mesenteric artery (SMA) vascular beds to this reflex are unknown. Accordingly, we compared the effects of single and combined 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. Occlusion 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, occlusion, 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-perfused organs during SMA occlusion was significantly greater than in celiac-perfused organs during celiac occlusion. Conversely, tissue mass subserved by the celiac artery was significantly greater than that subserved by the SMA (182 +/- 27 vs. 131 +/- 17 g, respectively). These data suggest that the larger cardiovascular reflex produced by SMA occlusion compared with celiac occlusion may be related to a greater increase of lactic acid concentration in tissue supplied by the SMA. In addition, 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.