GASTRIC-MUCOSAL PH AS A PROGNOSTIC INDEX OF MORTALITY IN CRITICALLY ILL PATIENTS

Objective: To determine if measurements of gastric intramucosal pH have prognostic implications regarding ICU mortality. Design: Prospective comparison of outcome. Setting: General adult ICUs in two teaching hospitals. Patients: Eighty consecutive patients age 18 to 84 yrs (mean 63.4), 50 men and 30 women, 55% in the medical and 45% in the surgical services. Methods: Gastric intramucosal pH was measured on ICU admission and again 12 hrs later. A value of greater-than-or-equal-to 7.35 was used to differentiate between normal and low gastric intramucosal pH. Measurements and Main Results: Fifty-four patients had a normal gastric intramucosal pH and 26 patients had a low gastric intramucosal pH on ICU admission. The mortality rate was greater in the low gastric intramucosal pH group (65.4% vs. 43.6%; p < .04). The frequency of sepsis and the presence of multisystem organ failure also were greater in the low gastric intramucosal pH group (p < .01). Further stratification of patients according to gastric intramucosal pH measured 12 hrs after admission showed a greater mortality rate in patients with persistently low gastric intramucosal pH when compared with patients with normal gastric intramucosal pH during the first 12 hrs (86.7% vs. 26.8%; p < .001). Conclusions: Measurements of gastric intramucosal pH on ICU admission, and again 12 hrs later, have a high specificity for predicting patient survival in this ICU patient population (77.8% to 80.6%). Furthermore, given its relative noninvasive nature, tonometrically measured gastric intramucosal pH may be a useful addition to patient monitoring in the ICU.