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

Abstract

Gastric tonometer PCO2 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 PCO2 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 PCO2 minus arterial PCO2 (DeltaPCO2) and calculated the corresponding intracellular pH from tonometers placed in the stomach and jejunum. We found that the correlation coefficient (r2) for biphasic gut oxygen delivery-DeltaPCO2 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 DeltaPCO2 was excessively high and variable (62.9 +/- 39.6) compared with the critical small bowel tonometer DeltaPCO2 (17.0 +/- 15.0, P < 0.01). Small bowel tonometer PCO2 was closely correlated with superior mesenteric vein PCO2 (r2 = 0.81, P < 0.001), whereas gastric tonometer PCO2 was not (r2 = -0.13, P = not significant). We conclude that measurement of gastric tonometer PCO2 yields excessively noisy and inaccurate data on the onset of gut anaerobic metabolism in hemorrhagic shock. Small bowel tonometer PCO2 is less noisy and, as a result, is superior in detecting gut hypoperfusion and the onset of anaerobic metabolism.

Monitoring technologies in the neonatal intensive care unit: implications for the detection of necrotizing enterocolitis

“…The intramucosal pH has been shown to be a valuable indicator of gut ischemia, 19 early hypovolemia, 20 mortality and sepsis. 21 Gastric tonometry has been applied to two term infants with hypoplastic left heart syndrome, which is generally regarded to be a risk factor for NEC.…”

“…To improve accuracy or to gain easier access, several studies tested measurements from alternate sites such as small intestine, 19 rectum 23 and sublingual. 24 In detecting the onset of anaerobic metabolism caused by hemorrhagic shock in 10 anesthetized and mechanically ventilated pigs, small bowel P CO2 was more accurate with less noise compared with gastric P CO2 , showing significant correlation with superior mesenteric vein P CO2 (r 2 ¼ 0.81, P<0.001).…”

“…24 In detecting the onset of anaerobic metabolism caused by hemorrhagic shock in 10 anesthetized and mechanically ventilated pigs, small bowel P CO2 was more accurate with less noise compared with gastric P CO2 , showing significant correlation with superior mesenteric vein P CO2 (r 2 ¼ 0.81, P<0.001). 19 In premature neonates, the small intestine is difficult to access, but the rectum could be a more accessible and less fragile alternate location. Rectal tonometry was shown to be poorly correlated with gastric measurement in a study of 26 adult cardiac surgery patients in the perioperative period (elective coronary artery bypass grafting with cardiopulmonary bypass) and 4 h postsurgery.…”

Assessing anemia and hypovolemia related altered oxygen balance

“…This is in accordance with previously published reports. 59 In contrast, there was no significant change in the Ga-PCO2. Regarding the importance and the value of gastric mucosal pH is controversial and its routine use has declined in intensive care over the last decades.…”

“…Hb (g/L) 7.8(7.1-9.2(8.0-9.9)* 7.7(7.1-8.1) 8.9(7.9-9.6)* ScvO 2 (%) 62 (57)(58)(59)(60)(61)(62)(63)(64) LG HG …”