Comparison of gastric mucosal pH and clinical judgement in critically ill patients

Objectives: To compare gastric tonometry (pHi) with estimates of pH in ill injured patients, and to correlate pi-Ii with haemodynamic variables. Design: Prospective, non-interventional study. Setting: ICU of Level I trauma centre, USA. Main outcome measures: 154 gastric tonometry measurements were compared with physicians' estimates of adequacy of resuscitation. Resuscitation was categorised as inadequate (pHi < 7.35) or adequate (pHi greater than or equal to 7.35). Measured and estimated pHi were also compared with oxygen delivery, oxygen consumption, cardiac index, mixed venous O-2 saturation, and critical illness scores. Results: Estimated pHi was often higher than measured pi-Ii in the judgement of all four surgical intensive care physicians. Measured pHi correlated positively with mixed venous O-2 tension (r = 0.21). There were significant negative correlations between measured pHi and both oxygen delivery (r = -0.25) and oxygen consumption (r- = -0.28). Estimated pHi correlated positively with mean arterial pressure (r = 0.21) and hospital day (r = 0.26); it correlated negatively with pulmonary arterial elastance (r= -0.35). Conclusion: Experienced intensive care physicians tended to overestimate visceral perfusion, which suggests that gastric tonometry adds useful information over and above routine haemodynamic indices. Arterial blood pressure and mixed venous oxygen saturation correlated better with measured pHi than with other indices of perfusion.