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The effect of acidified enteral feeds on gastric colonization in critically ill patients: Results of a multicenter randomized trial

Heyland, Daren K. MD, FRCPC, MSc; Cook, Deborah J. MD, FRCSC, MSc; Schoenfeld, Phillip S. MD, MSEd; Frietag, Andreas MD, FRCSC; Varon, Joseph MD, FACP, FCCP; Wood, Gordon MD, FRCPC for the Canadian Critical Care Trials Group

Clinical Investigations

Objective: To evaluate the effect of acidified enteral feeds on gastric colonization in critically ill patients compared with a standard feeding formula.

Design: Randomized, double-blind, multicenter trial.

Setting: Eight mixed intensive care units at tertiary care hospitals

Patients: We recruited mechanically ventilated critically ill patients expected to remain ventilated for >48 hrs. We excluded patients with gastrointestinal bleeding, acidemia, and renal failure requiring dialysis. We enrolled 120 patients; 38% were female, age (mean ± SD) was 57.6 ± 19.3 yrs, and Acute Physiology and Chronic Health Evaluation II score (mean ± SD) was 21.6 ± 7.6.

Interventions: Vital High Nitrogen (Abbott Laboratories, Ross Products Division, Columbus, OH) was used as the standard feeding formula for the control group (pH = 6.5). Hydrochloric acid was added to Vital High Nitrogen to achieve a pH of 3.5 in the experimental group.

Measurements and Main Results: The main outcome measure was gastric colonization. Secondary outcomes included gastric pH, pneumonia, and mortality. The mean gastric pH in patients receiving acid feeds was lower (pH = 3.3) compared with controls (pH = 4.6; p < .05). One patient (2%) on acid feeds was colonized in the stomach with pathogenic bacteria, compared with 20 patients (43%) in the control group (p < .001). There was no difference in the incidence of pneumonia (6.1% in the acid feeds group vs. 15% in the control group; p = .19). Overall, there were 15 deaths in the acid feeds group and seven in the control group (p = .10); four patients in the acid feeds group and three in the control group died during the study period (p not significant).

Conclusions: Acidified enteral feeds preserve gastric acidity and substantially reduce gastric colonization in critically ill patients. Larger studies are needed to examine its effect on ventilator-associated pneumonia and mortality.

From the Department of Medicine, Queen's University, Kingston, ON, Canada (Drs. Heyland and Wood); the Department of Medicine, McMaster University, Hamilton, ON, Canada (Drs. Cook and Frietag); the Division of Gastroenterology, National Naval Medical Center, Bethesda, MD (Dr. Schoenfeld); and the Pulmonary and Critical Care Section, Baylor College of Medicine, Methodist Hospital, Houston, TX (Dr. Varon).

Supported, in part, by an investigator-initiated grant from Ross Products Division, Abbott Laboratories.

Drs. Heyland and Cook are Career Scientists of the Ontario Ministry of Health.

Address requests for reprints to: Dr. Daren K. Heyland, Angada 3, Kingston General Hospital, 76 Stuart Street, Kingston, ON, Canada K7L 2V7. E-mail:

© 1999 Lippincott Williams & Wilkins, Inc.