Regional Blood Flow Distribution and Oxygen Metabolism During Mesenteric Ischemia and Congestion

BackgroundAcute mesenteric ischemia is a potentially fatal vascular emergency with mortality rates ranging between 60% and 80%. Several studies have extensively examined the hemodynamic and metabolic effects of superior mesenteric artery occlusion. On the other hand, the cardiocirculatory derangement and the tissue damage induced by intestinal outflow obstruction have not been investigated systematically. For these reasons we decided to assess the initial impact of venous mesenteric occlusion on intestinal blood flow distribution, and correlate these findings with other systemic and regional perfusion markers.MethodsFourteen mongrel dogs were subjected to 45 min of superior mesenteric artery (SMAO) or vein occlusion (SMVO), and observed for 120 min after reperfusion. Systemic hemodynamics were evaluated using Swan-Ganz and arterial catheters. Regional blood flow (ultrasonic flow probes), intestinal O2-derived variables, and mesenteric-arterial and tonometric-arterial pCO2 gradients (Dmv-apCO2 and Dt-apCO2) were also calculated.ResultsSMVO was associated with hypotension and low cardiac output. A significant increase in the regional pCO2 gradients was also observed in both groups during the ischemic period. After reperfusion, a progressive reduction in Dmv-apCO2 occurred in the SMVO group; however, no improvement in Dt-apCO2 was observed. The histopathologic injury scores were 2.7 ± 0.5 and 4.8 ± 0.2 for SMAO and SMVO, respectively.ConclusionsSMV occlusion promoted early and significant hemodynamic and metabolic derangement at systemic and regional levels. Additionally, systemic pCO2 gradient is not a reliable parameter to evaluate the local intestinal oxygenation. Finally, the Dt-apCO2 correlates with histologic changes during intestinal congestion or ischemia. However, minor histologic changes cannot be detected using this methodology.