Effect of neuromuscular blockade on energy expenditure in patients with severe head injury

Abstract

BACKGROUND: The purpose of this study was to determine the effect of neuromuscular blockade on energy expenditure in severely head-injured patients; to determine the effects of body temperature, nutrition support, and morphine use on metabolic rate; and to compare measured energy expenditure with values from predictive equations. METHODS: Energy expenditure was measured using indirect calorimetry in 2 groups of ventilated patients-18 with severe head injury during and after administration of pancuronium bromide and morphine, and second, 14 severely traumatized patients without severe head injury (trauma group) who received morphine without neuromuscular blockade. RESULTS: The mean energy expenditure of head-injured patients increased significantly once pancuronium was discontinued, ie, from 24.2 +/- 3.1 to 28.7 +/- 4.6 kcal/kg (p = .002). This effect was independent of other relevant variables such as morphine dose, body temperature, and nutrition support. When compared with the Harris-Benedict and World Health Organization predictive equations, neuromuscular blockade resulted in a stress factor of only 0.96 and 0.95, respectively, which increased to 1.19 and 1.18, respectively, once blockade was discontinued. Head-injured patients not on neuromuscular blockade had a significantly greater energy expenditure when compared with the trauma group (p = .02). CONCLUSIONS: Neuromuscular blockade in severely head-injured patients decreases energy expenditure to basal levels, independent of morphine use, body temperature, and feeding. Levels of hypermetabolism in both the head-injured and trauma groups were relatively low, at 19% and 5% above predicted values, respectively. This study provides useful information for the management of nutrition support in severely traumatized patients.

The use of pancuronium during the first week after severe head injury resulted in a significant decrease in energy expenditure measured by indirect calorimetry. Multiple regression analysis revealed that this decrease could not be explained by concomitant morphine use, body temperature, or feeding.