Occlusive mesenteric ischemia and its effects on jejunal intramucosal pH, mesenteric oxygen consumption and oxygen tensions from surfaces of the jejunum in anesthetized pigs

Objective: To investigate the effects of superior mesenteric artery (SMA) flow reduction on the jejunal intramucosal pH (pH(i)) and to compare these effects with corresponding changes of mesenteric oxygen transport variables and oxygen tensions on the surfaces of the jejunal serosa and mucosa. Design: Prospective, randomized, controlled, experimental study. Setting: Animal research laboratory. Subjects: 20 domestic pigs. Interventions: Mechanical flow reduction in the SMA. The animals were randomized to have an SMA flow of 0%, 25%, 38%, 50% or 100% (control). Measurements and main results: Measurements (baseline, ischemia, reperfusion) consisted of hemodynamic and oxygen transport variables, SMA blood flow, mesenteric oxygen transport variables, pH(i) and oxygen tensions of the jejunal serosa and mucosa. Flow reduction in the SMA resulted in a significant decrease of pH(i) indicating ischemia earlier than mesenteric oxygen transport variables. The relationship between mesenteric oxygen delivery (DO2ms) and pH(i) during acute ischemia is best described by a sigmoid curve. There was a linear correlation between the changes of the jejunal surface oxygen tensions and pH(i) due to SMA flow reduction. Conclusion: The sigmoid relationship between pH(i) and DO2ms indicated that pH(i) is a sensitive parameter for detecting ischemia at 50% of the baseline oxygen delivery and that below 25% there was no further decrease of pH(i). In contrast, mesenteric and whole body oxygen transport parameters were not indicative of impaired mucosal oxygen supply.