Enteral feeding in burn hypermetabolism: nutritional and metabolic effects of different levels of calorie and protein intake.

Enteral nutrition was provided by continuous pump-controlled gastrostomy tube feeding for 14 days in 97 guinea pigs bearing a 30% full thickness burn. Seven defined combinations of caloric and protein intake were studied. With a caloric intake of 175 kcal/kg/day, equaling the measured energy expenditure, the animals receiving 10% of calories as protein had a significantly greater postburn weight loss (p less than 0.05) and muscle mass depletion (p less than 0.05), and a significantly lower muscle nitrogen concentration (p less than 0.05), serum albumin level (p less than 0.01) and liver nitrogen content (p less than 0.01). With the same caloric intake but with more than 20% of calories as protein, the weight loss and the muscle wasting were reduced, but not abolished, and the serum albumin level and liver nitrogen content were normalized. Also with the diets containing 200 kcal/kg/day the muscle tissue depletion could not be abolished. However, with this caloric intake, the animals given 20% of calories as protein had a lower weight loss and a higher serum albumin level (p less than 0.01), but also a greater fat infiltration of the liver (p less than 0.01). At both levels of caloric intake, the nitrogen balance correlated significantly with the level of nitrogen intake but did not correlate with the changes of body weight. The incidence of diarrhea was lowest in animals fed 20% protein calories at a caloric intake of 175 kcal/kg/day. All things considered, the best metabolic and nutritional results were obtained with diets containing 20 to 30% of calories as protein and providing a caloric intake that paralleled the measured energy expenditure.