Monitoring bolus nasogastric tube feeding by the Brix value determination and residual volume measurement of gastric contents

Abstract

BACKGROUND: Critically ill patients do not always tolerate nasogastric tube feeding. Gastric residual volumes (GRVs), obtained by aspiration from a nasogastric tube, are widely used to evaluate feeding tolerance and gastric emptying, but controversy exists about what constitutes the true GRV (diet formula or digestive juice) and how it should affect management. In this pilot study, we used the Brix value (BV) measurement of gastric contents to monitor both GRV and food content in patients receiving nasogastric feeding. METHODS: Forty-three patients receiving bolus nasogastric feeding were monitored for 24 hours before entry into the study and then divided into 2 groups according to traditional use of GRV; patients with low GRVs ( < 75 mL) were placed in group 1, whereas patients with higher GRVs (> 75 mL) were placed in group 2. All subjects were given 250 mL of polymeric formula by bolus nasogastric infusion, followed by BV measurement of gastric contents at 0, 30, 60, 120, and 180 minutes. All gastric fluid was aspirated after 180 minutes of feeding; the volume was recorded and BV measurement made, then reinstilled with an added 30 mL of dilutional water, after which a final aspiration and BV measurement was performed. Calculated GRV and volume of formula remaining in the stomach was determined by derived equations. RESULTS: Serial BV measurements decreased in both groups after bolus feeding. For patients in group 2, the decrease was less such that at 180 minutes, the mean BV for gastric contents was significantly higher than for those patients in group 1 (10.1 vs 5.1, respectively; p < .01). Aspirated GRV, calculated GRV, and volume of formula remaining in the stomach at 180 minutes were significantly greater for patients in group 2 compared with those in group 1. Use of refractometry in combination with traditional use of GRV identified 4% (1/25) of patients in group 1 with low GRVs who might have possible gastric dysmotility (> 20% of initial 250-mL volume of formula remaining at 180 minutes) and ensured that 72% (13/18) of patients in group 2 with higher GRVs had sufficient gastric emptying ( < 20% of initial 250 mL volume of formula remaining). CONCLUSION: This pilot study raises the feasibility that refractometry and the BV measurement of gastric juice may be a promising tool for bedside monitoring of tolerance and gastric emptying in patients receiving nasogastric feeding, providing valuable complementary information to traditional use of GRV.