Gastric tonometry and enteral nutrition: a possible conflict in critical care nursing practice.

BACKGROUND Gastric tonometry is used to assess gastrointestinal mucosal perfusion in critically ill patients. However, enteral feeding is withheld during monitoring with gastric tonometry because enteral feeding is thought to influence tonometric measurements. OBJECTIVES To examine the effect of enteral feeding on the tonometric measurement of gastric mucosal carbon dioxide. METHODS Gastric tonometers were placed in 20 critically ill patients, and the PCO2 of the gastric mucosa was measured in both the full and the empty stomach during a 48-hour period. RESULTS The PCO2 measured by the tonometer increased after enteral feeding, and a significant difference in the PCO2 of the full versus the empty stomach was evident at 24 and 48 hours. PCO2 at 4, 24, and 48 hours differed significantly in the full stomach and in the empty stomach. However, the data did not reveal a significant difference in either the full stomach or the empty stomach between PCO2 at 24 hours and PCO2 at 48 hours. CONCLUSION After 24 hours of feeding, the initial increase in PCO2 observed at 4 hours was not evident, suggesting stabilization of the intragastric environment. However, a higher PCO2 was evident in the empty stomach, indicating that the presence of the feeding solution may reduce the diffusion of carbon dioxide into the tonometer balloon. Consequently, measurements of intragastric PCO2 obtained after 24 hours of feeding may be reliable if the stomach is emptied by aspiration via the tonometer immediately before measurement.