Observations on the patterns of 24-hour energy expenditure changes in body composition and gastric emptying in head-injured patients receiving nasogastric tube feeding.

BACKGROUND

Although intolerance to nasogastric feeding is commonly observed after head injury, quantitative measurements of gastric emptying are lacking. Concepts about energy requirements are limited by the lack of long-term measurements of total energy expenditure.

METHODS

Six male subjects with severe head injury had their gastric emptying measured by the phenol red technique. N and energy balances were measured by classic balance techniques, which included continuous indirect calorimetry for up to 24 hours (days 3 to 5). Measurements of body composition were made on days 3 to 5 and 12 to 19 (4 subjects only).

RESULTS

The subjects lost a mean of 9.8 kg of which 2.3 kg was estimated to be due to fat (equivalent to -14 g N/d and -1690 kcal/d). On days 3 to 5, basal metabolic rate (BMR) was 130% to 135% of predicted. The low dietary intake (650 kcal and 4.2g N/d) was associated with negative energy (-1710 +/- 520 kcal/d) and N balances (-19 +/- 5 g N/d). Gastric emptying was delayed twofold (days 3 to 5) compared with controls (p < .001) and was associated with significant regurgitation of feed into the mouth (16 of 31 saliva samples contained glucose at a concentration of > 0.5 mmol/L compared with control values of < 0.2 mmol/L.

CONCLUSIONS

The large negative energy balance in the subjects studied was largely due to the inadequate nasogastric feeding, which was associated with a twofold reduction in the rate of gastric emptying and frequent regurgitation of feed. The large negative N balance and the high contribution of protein oxidation to total energy expenditure (25% to 28%) was predominantly due to the injury sustained and immobility. An increase in BMR is not necessarily associated with increased total energy expenditure or energy requirements.