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Does pH paper accurately reflect gastric pH?
E D Dobkin1, A Valcour, C R McCloskey
1Department of Surgery, Hartford Hospital/University of Connecticut.
Insights
Color-scaled pH paper testing for gastric pH in intensive care units (ICUs) is inaccurate for preventing stress gastritis. This method risks undertreatment and may require more reliable monitoring for critically ill patients.
Area of Science:
- Critical Care Medicine
- Gastroenterology
- Medical Device Accuracy
Background:
- Gastric pH monitoring is standard for critically ill patients in the ICU.
- Maintaining gastric pH > 3.5 prevents upper GI bleeding; lower pH increases hemorrhage risk.
Purpose of the Study:
- To compare nasogastric pH measurement accuracy using pH electrodes versus color-scaled pH paper.
- To evaluate the clinical utility of pH paper for stress gastritis prophylaxis.
Main Methods:
- 16 critically ill surgical ICU patients hospitalized for 3-10 days were studied.
- 370 gastric specimens were analyzed comparing pH electrode readings to pH paper results.
- Therapeutic endpoint set at paper pH (pH[p]) ≥ 4.
Main Results:
- pH paper showed 66.7% sensitivity and 94.5% specificity for gastric pH ≥ 4.
- For clear buffered solutions, pH paper achieved 100% sensitivity and specificity.
- Inaccuracy was not linked to observer error or paper quality/age.
Conclusions:
- Color-scaled pH paper lacks clinical accuracy for monitoring therapy to prevent stress gastritis.
- This method can lead to significant undertreatment of at-risk patients.
- More accurate gastric pH monitoring methods may be necessary for guiding stress-related hemorrhage prevention.
Abstract:
The testing of gastric pH in the ICU has become the standard of care for most critically ill patients. It has been demonstrated that maintaining a gastric pH of greater than 3.5 confers protection from upper GI bleeding, while lesser pH values subject the patient to hemorrhagic risk. We compared nasogastric pH, as measured by pH electrode, to color-scaled pH paper in 16 critically ill patients hospitalized 3 to 10 days in the surgical ICU. Statistical analysis of 370 gastric specimens revealed a sensitivity of 66.7% and specificity of 94.5% when a paper pH (pH[p]) of greater than or equal to 4 was used as the therapeutic end-point. The sensitivity and specificity of the same pH(p) for clear buffered solutions were 100%. We conclude that the use of pH(p) lacks the clinical accuracy for determining the effects of therapy for the prophylaxis of stress gastritis and will lead to a significant degree of undertreatment. This lack of accuracy is not due to observer error or the quality or age of the testing paper. Our results suggest that if the measurement of gastric pH by pH(p) analysis is to be used as a guide for the prevention of stress-related hemorrhage, a more accurate method of monitoring may be warranted.