Estimating energy requirements in patients receiving parenteral nutrition

Adequate nutritional support should use a patient's energy expenditure as a guide for administering sufficient but not excessive caloric intake. Sixty-seven patients were evaluated using indirect calorimetry, to determine the applicability of commonly used predictive equations for energy expenditure in patients requiring parenteral nutrition. The frequently used calculation that involves multiplying a constant value of kilocalories per kilogram by the patients weight consistently underestimated the energy requirements of patients of low body weight and overestimated the requirements for heavy body weight. The Harris-Benedict equation was found to be highly dependent on body weight and was not any more accurate than estimations of individual requirements using a simpler weight or surface area regression equation. We recommend that an actual regression equation incorporating body weight or body surface area be used to predict energy requirements and that the oversimplified but common use of the constant value of kilocalories per kilogram be abandoned.