Energy expenditure and severity of injury and illness indices in multiple trauma patients

Objective: To determine whether the energy expenditure of mechanically vent ilated multiple trauma patients correlates with the severity of injury and illness indices before important systemic infection has complicated the cli nical course, and to compare the energy expenditure with the energy expendi ture expected from the Harris-Benedict equation adjusted with correction fa ctors for trauma. Design: Prospective, clinical study. Setting: General intensive care unit of a university teaching hospital. Patients: Immediate multiple trauma adult patients who required mechanical ventilation. Interventions: Metabolic cart connected to the ventilator, Measurements and Main Results: Data on admission to the emergency departmen t and during the first 24 hrs of intensive care unit admission were collect ed for computation of severity of injury and illness indices, respectively. Resting and total energy expenditures were derived at least 48 hrs after i ntensive care unit admission by continuous indirect calorimetry. Predicted basal energy expenditure was obtained using the Harris-Benedict equation an d predicted total energy expenditure was calculated using the Harris-Benedi ct value adjusted with correction factors for trauma. Twenty-six multiple t rauma adult patients completed the study. No statistically significant corr elations were observed between both the resting energy expenditure and the total energy expenditure and the Injury Severity Score, Revised Trauma Scor e, Simplified acute Physiologic Score II, Acute Physiology and Chronic Heal th Evaluation II score, and Glasgow Coma Scale score. A regression model of total energy expenditure was developed with the following variables: Harri s-Benedict equation, heart rate, and minute ventilation (p = .01; r(2) = .7 4). The resting energy expenditure/predicted basal energy expenditure ratio was 1.17 +/- 0.2 and the total energy expenditure/predicted total energy e xpenditure ratio was 0.76 +/- 0.1. Conclusions: In mechanically ventilated multiple trauma patients the energy expenditure is not correlated to the severity of injury and illness indice s but is dependent on the Harris-Benedict equation in addition to heart rat e and minute ventilation. Furthermore, this patient population is character ized by a moderate state of hypermetabolism, and the Harris-Benedict predic tion modified with correction factors for trauma systematically overestimat es the total energy expenditure.