Intermittent enteral nutrition--a comparative study examining the effect on gastric pH and microbial colonization rates

In a prospective randomized study we aimed to examine the effect on gastric pH and microbial colonization of enteral nutrition (EN) delivered both by intermittent and continual infusion. Forty-three mechanically ventilated patients were randomized to receive EN by one of three methods, intermittent or continual gastric or continual jejunal. We sampled gastric aspirate for pH and culture in all patients at 0600 hours and pH in gastric intermittent feeders at 2200 hours daily. Patients were studied for 12 days or until extubated. Data was obtained on 41 patients, of whom 73% had a diagnosis of trauma. Median APACHE II score was 17 and ventilation time 11 days. Twelve patients received gastric continuous, 15 gastric intermittent and 14 jejunal nutrition. No significant difference was observed between the three groups with regard to median 0600 pH (P = 0.16). This was lowest in the jejunal group (3.2) followed by the gastric intermittent group (4.0) and then gastric continuous group (5.0). With overnight cessation of EN in the gastric intermittent group, the median pH fell from 5.2 at 2200 to 4.0 at 0600 (P = 0.01) with no effect on gastric colonization. The probability of gastric colonization over time however was significantly lower in the jejunal group compared with the two gastric groups (Log rank test, P = 0.02). These results demonstrate that in a patient population consisting predominantly of trauma, overnight cessation of EN made no overall difference to 0600 gastric pH or colonization rates. The preservation of pH and lowered colonization in those given jejunal feeding may have implications in the pathogenesis of ventilator-associated infection and may warrant further study using larger patient numbers.