The measurement of gut mucosal carbon dioxide has been used to detect decreased blood flow. Accumulation of carbon dioxide is predominantly a result of hypoperfusion and not hypoxia. Because the introduction of a nasogastric tube is almost routine in critically ill patients, the measurement of gastric carbon dioxide can be an easy method to monitor tissue perfusion. The gastric mucosal pH is measured according to an equation that assumes that arterial bicarbonate is equal to intramucosal bicarbonate, an argument that is not always valid. Given that the gastric mucosal carbon dioxide is the directly measured value, whereas the gastric mucosal pH is the derived and possibly inaccurate value, studies that used gastric pH to monitor perfusion may be inherently flawed. Most studies have failed to effectively affect gastric pH and for this reason failed to produce improvements in outcome. One study, by Gutierrez and colleagues, has shown that therapeutic interventions guided by gastric tonometry improved survival in critically ill patients. In a direct comparison of splanchnic-oriented therapy as guided by gastric tonometry with conventional shock management of trauma patients, there was no difference in mortality rates, organ dysfunction rates, or length of stay. After a surge in popularity, the use of gastric tonometry waned and it is currently found with less frequency in surgical ICUs.
- Carlesso E, Taccone P, Gattinoni L (June 2006). "Gastric tonometry". Minerva Anestesiol 72 (6): 529–32. ISSN 0375-9393. PMID 16682926.
- George C. Velmahos MD, PhD, MSE and Hasan B. Alam MD (July 2008). "Advances in Surgical Critical Care". Current Problems in Surgery 45 (7): 453–516. doi:10.1067/j.cpsurg.2008.03.003. PMID 18503823.
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