CONTROL AND VARIABILITY OF GASTRIC PH IN CRITICALLY ILL CHILDREN

Objectives: To determine the effect of illness severity and acute central nervous system injury on the control and variability of gastric pH in pediatric intensive care unit (ICU) patients receiving ranitidine. Design: Prospective, descriptive study. Setting: Pediatric ICU of a children's hospital. Patients: Fourteen pediatric ICU patients. Interventions: Ranitidine (4 mg/kg/day) was administered to all patients. Measurements and Main Results: Patients enrolled in the study were divided into two groups based on illness type and severity. Illness severity was measured by the Pediatric Risk of Mortality (PRISM) score, with a PRISM score of greater than or equal to 20 defining severe illness. Illness type was designated as central nervous system or noncentral nervous system. Gastric pH was continuously monitored in all patients using an intragastric, pH-sensitive electrode. Poor control of gastric pH was defined as a pH of <4.0 for >20% of the time monitored The statistical significance of the differences between groups was measured using the Wilcoxon two-sample test or Fisher's exact test. Patients with severe illness or acute central nervous system injury had a lower mean gastric pH than all other patients (4.6 vs. 6.4;p = .008) and spent more time with a gastric pH of <4.0 than other patients (47.5% of time monitored vs. 12.5% of time monitored; p = .003). Poor control of gastric pH occurred in 100% of patients with severe illness or acute central nervous system injury, while only 20% of the remaining patients had poor control of gastric pH (p = .01). Using power-spectrum analysis to evaluate gastric pH variability, gastric pH in patients receiving bolus ranitidine was more variable than gastric pH in patients receiving ranitidine continuously (p = .045). Illness severity or type had no effect on gastric pH variability (p = .78). Conclusions: a) Continuous infusion of ranitidine decreases variability of gastric pH in pediatric ICU patients; b) gastric pH variability may make intermittent monitoring of gastric pH inaccurate; c) children with acute central nervous system injury or PRISM scores of greater than or equal to 20 have poor control of gastric pH; d) type of injury and PRISM scores predict response to ranitidine therapy.