Determinants of Tissue PCO2 in Shock and Sepsis: Relationship to the Microcirculation
The development of gastrointestinal tonometry was an important step in the monitoring of tissue dysoxia. It rapidly became a useful tool in basic research. In addition, and for the first time, a regional parameter could be used to detect and to treat hypoperfusion. From an experimental point of view, tonometry adequately tracks intramucosal acidosis , i.e., the increase in intramucosal-arterial PCO2 difference (ΔPCO2). Likewise, the increase in ΔPCO2 is better than other systemic and intestinal variables to show tissue hypoperfusion in normal volunteers  and in experimental models . Intramucosal acidosis is a sensitive predictor of gastric  and colonic mucosal ischemia . Furthermore, gastric tonometry is an insightful predictor of outcome. This usefulness has been shown in postoperative , critically ill , septic  and shock  patients. Gastric tonometry might also be used to assess the effect of vasoactive drugs [10, 11]. Finally, intramucosal pH (pHi) has been evaluated as a guide for resuscitation. Gutierrez et al.  demonstrated in a randomized controlled trial that pHi-guided therapy could decrease mortality in critically ill patients.
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