Effect of Acid Feeds on Feeding System Contamination

Abstract

Background and Objective:

Bacterial contamination of the enteral nutrition delivery system (FS) has been well described. Case reports and prospective cohort studies suggest that bacterial contamination is a cause of morbidity and mortality in the critically ill patient. Because bacterial growth and replication is pH dependent, we hypothesized that acidified enteral feedings would lower incidence of bacterial contamination of the FS and potentially infectious morbidity and mortality of critically ill patients. Our objective was to evaluate the effect of acidified enteral feedings on bacterial growth in the FS and subsequent gastric and tracheal bacterial growth.

Design:

Randomized, double-blind, placebo-controlled, multicenter study.

Setting:

Eight mixed intensive care units at tertiary care hospitals.

Patients:

We recruited mechanically ventilated critically ill patients expected to remain ventilated ≥48 hours. We excluded patients with overt gastrointestinal bleeding, persistent acidemia, and renal failure requiring dialysis. We enrolled 120 patients: women, 38%; age, 57.6 ± 19.3 years, and mean APACHE II score, 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. Hydrochloric acid was added to achieve a pH to 3.5 in the experimental group.

Main Outcome Measures:

Microbial growth in the FS, stomach, and trachea.

Results:

Compared with patients in the control group, patients who received acid feedings were less likely to have potentially pathogenic microorganisms in their FSs (19% versus 80% of patients [p ≤ .001] and 0.1 versus 0.8 organisms per specimen [p ≤ .001]). There were 151 organisms that were cultured in two or more sites. Of the 146 organisms cultured from the stomach, 22 (15%) were first cultured in the feeding system and 32 (22%) were cultured simultaneously in the feeding system and the stomach. Of the 58 organisms cultured in the trachea, 19 (33%) were first cultured in the feeding system and 6 (10%) were cultured simultaneously in the feeding system and the trachea.

Conclusions:

The feeding system is a frequent source of gastric and tracheal contamination. Acidified enteral feedings reduces contamination of the feeding system and therefore may have an impact on subsequent colonization and infection. Larger studies of acidified enteral feedings are needed to examine their effect on infectious morbidity and mortality.