Energy expenditure assessment and validation after acute spinal cord injury

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.

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.

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).

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.