Small bowel tonometry is more accurate than gastric tonometry in detecting gut ischemia

Abstract

Gastric tonometer[Formula: see text] measurement may help identify gut ischemia in critically ill patients but is frequently associated with large measurement errors. We tested the hypothesis that small bowel tonometer [Formula: see text]measurement yields more accurate information. In 10 anesthetized, mechanically ventilated pigs subject to progressive hemorrhage, we measured gut oxygen delivery and consumption. We also measured tonometer [Formula: see text] minus arterial[Formula: see text]([Formula: see text]) and calculated the corresponding intracellular pH from tonometers placed in the stomach and jejunum. We found that the correlation coefficient ( r 2) for biphasic gut oxygen delivery-[Formula: see text]relationships was 0.29 ± 0.52 for the gastric tonometer vs. 0.76 ± 0.25 for the small bowel tonometer ( P < 0.05). In addition, the critical gastric tonometer [Formula: see text]was excessively high and variable (62.9 ± 39.6) compared with the critical small bowel tonometer[Formula: see text] (17.0 ± 15.0, P < 0.01). Small bowel tonometer[Formula: see text] was closely correlated with superior mesenteric vein [Formula: see text]( r 2 = 0.81, P < 0.001), whereas gastric tonometer [Formula: see text] was not ( r 2 = −0.13, P = not significant). We conclude that measurement of gastric tonometer[Formula: see text] yields excessively noisy and inaccurate data on the onset of gut anaerobic metabolism in hemorrhagic shock. Small bowel tonometer [Formula: see text] is less noisy and, as a result, is superior in detecting gut hypoperfusion and the onset of anaerobic metabolism.