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Measurement technique and variation in intramucosal pH
1Major Injuries Unit, Selly Oak Hospital, Birmingham.
British Journal of Anaesthesia
|April 1, 1996
Summary
Gastric intramucosal pH (pHi) measurements vary significantly based on sample storage and measurement delays. Proper handling is crucial, as even small variations can impact clinical decisions in critical care.
Area of Science:
- Critical Care Medicine
- Gastroenterology
- Physiology
Background:
- Gastric intramucosal pH (pHi) is a valuable indicator of tissue perfusion and cellular metabolic state.
- Accurate pHi measurement is essential for monitoring critically ill patients and guiding resuscitation efforts.
Purpose of the Study:
- To evaluate the impact of different sampling techniques and storage conditions on the accuracy of gastric pHi measurements.
- To determine the variability introduced by delayed measurement of TCO2 (tonometered saline PCO2).
Main Methods:
- Gastric pHi was calculated from Trip catheter saline tonometered samples in two ventilated patients.
- Four distinct sampling techniques were employed, with each repeated five times.
- PCO2 in tonometered saline (TCO2) was measured immediately and at 6-minute intervals for 30 minutes.
Main Results:
- Measurement variation was highest with capped syringes stored at room temperature and lowest with uncapped samples stored on ice.
- TCO2 levels consistently decreased significantly within 12 minutes of sampling.
- The mean difference in calculated pHi across all techniques over 30 minutes was 0.1005 pH units.
Conclusions:
- The method of sample storage and the delay in measurement significantly affect the calculated gastric pHi.
- Potential errors of +/- 0.1 pH units highlight the need for standardized protocols to ensure reliable pHi monitoring in clinical practice.