EQUIVALENCE OF LITMUS PAPER AND INTRAGASTRIC PH PROBES FOR INTRAGASTRIC PH MONITORING IN THE INTENSIVE-CARE UNIT

Objective: To compare the accuracy of litmus paper-determined gastric pH to a nasogastric graphite antimony pH probe. Design: A prospective clinical trial of gastric pH determination in patients enrolled in a s tudy of histamine-2-receptor (H-2) antagonists. Setting: The medical i ntensive care unit (ICU) of a 450-bed county hospital. Patients: Criti cally ill ICU patients requiring stress ulcer prophylaxis. Interventio ns: Using a crossover design, the patients were randomized to initiall y receive an H-2 antagonist by continuous infusion or intravenous bolu s, and subsequently were crossed over to the other limb of the study. Measurements and Main Results: Gastric pH was determined using pH-sens itive litmus paper at the initiation of each limb of the study and at 1, 2, 4, and 8 hrs after the initiation of H, receptor antagonist ther apy. in addition, gastric pH was continuously determined over the same time period utilizing a graphite antimony pH probe, Gastric pH measur ements determined with litmus paper and intragastric pH probes demonst rated an excellent correlation (r(2) = .93, p < .001). McNemar's test of correlated proportions could not demonstrate a significant differen ce between the two monitoring methods (chi-square = 0.5, p > .47), and the kappa statistic (0.95, p < .001) demonstrated excellent concordan ce, Bias measurement was 0.01 (95% confidence interval = -0.155 to 0.1 76). Conclusions: Measurement of intragastric pH, using pH-sensitive l itmus paper, is both sensitive and specific when utilizing a graphite antimony nasogastric pH probe as a reference standard. Litmus paper-de termined gastric pH testing is both easy to perform and inexpensive. T herefore, based on the current data, we believe this technique (i.e., litmus paper determined gastric pH testing) to be the method of choice for determination of intragastric pH in patients at risk for stress g astric ulcers in the medical ICU.