Energy expenditure assessment and validation after acute spinal cord injury

Abstract

Background: This study was designed to determine the applicability of the Harris Benedict (HB) equation in predicting energy requirements after acute spinal cord injury (SCI) and to evaluate the accuracy of a 30-minute energy expenditure measurement to determine 24-hour requirements. Prealbumin (PAB) was monitored weekly to assess the patient's response to the nutrition support regimen.

Methods: Patients with acute isolated SCI requiring mechanical ventilation were studied for 4 weeks postinjury. Predicted energy expenditure was estimated using a modified HB equation (HBEE). The protein goal was 2.0 g/kg or 0.23 g nitrogen/kg admission body weight/day. Nutrition support was initiated within 48 hours if medically feasible. Indirect calorimetry was performed weekly to obtain 24-hour measured total energy expenditure (MTEE) and measured resting energy expenditure (MREE) values. Respiratory quotient, PAB levels, urinary urea nitrogen (UUN), and calculated nitrogen balance were evaluated weekly.

Results: Eleven tetraplegic men with a mean age of 32 +/- 8 years were studied. Mean MTEE equaled 95% to 100% HBEE. Mean MREE was not significantly different from the mean MTEE. There was a significant correlation between mean predicted and measured 24-hour energy expenditure for each data point. Mean UUN excretion ranged from 22.3 to 28.5 g/d that resulted in a mean negative nitrogen balance for all 4 weeks. PAB improved significantly over the 4-week study period (p < .001).

Conclusions: There was a strong correlation between HBEE and MTEE. A brief REE measurement is adequate to determine daily calorie requirements. Visceral protein synthesis can be achieved despite a negative nitrogen balance.