Gastric Tonometry and Intramucosal pH - Theoretical Principles and Clinical Application

Received September 9, 1999
Accepted December 21, 1999

Summary
Gastric or intestinal luminal tonometry is a method for monitoring critically ill patients. It offers an index of the adequacy of aerobic metabolism in a tissue that is particularly sensitive to alterations in its perfusion and oxygenation: the gut mucosa. It is based on the measuring the increase in tissue CO₂ production that accompanies anaerobic metabolism. The method simply consists of a balloon in the stomach, which measures intramucosal pCO₂. From this measurement and from the arterial bicarbonate concentration gastric intramucosal pH (pHi) can be calculated, assuming that bicarbonate concentration in the gastric mucosal tissue is in equilibrium with systemic arterial bicarbonate. Despite possible clinical benefit from the measurement and the therapy of low pHi values in critically ill patients, the theoretical, experimental and pathophysiological implications for the monitoring of intramucosal acidosis in the gut are not yet fully understood. There are still some open methodological questions crucial for further clinical interpretation.

Key words
Shock · Diagnostic techniques and procedures · Anoxia · Intensive care · Tonometry · pHi · Splanchnic perfusion

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Dr. V. Černý, E. Beneše 1537, 500 12 Hradec Králové, Czech Republic, e-mail: cernyvla@fnhk.cz