ENERGY-EXPENDITURE AND WITHDRAWAL OF SEDATION IN SEVERE HEAD-INJURED PATIENTS

Objectives: To determine the outcome of oxygen consumption (Vo(2)) and energy expenditure after cessation of sedation in severe head-injured patients and to assess its usefulness as a predictor of neurologic se verity. Design: Prospective, descriptive study. Setting: Neurosurgical intensive care unit (ICU) in a university hospital. Patients: Fifteen severe head-injured patients with tracheostomies and who were mechani cally ventilated and sedated at the time of the study. Interventions: None. Measurements and Main Results: Vo(2) and energy expenditure were measured, using indirect calorimetry during and after discontinuation of sedation. After the measurement period, the patients were divided into two groups. Group 1 included patients who were completely weaned from sedation; group 2 included patients who had to be sedated again u sing predetermined criteria. In both groups, energy expenditure was cl ose to basal energy expenditure during sedation, and increased to 150% of basal energy expenditure during the recovery period, with maximum hourly values 80% above basal energy expenditure. In group 1, Vo(2) an d energy expenditure changed from 284 +/- 44 mL/min and 1833 +/- 261 k cal/day during sedation to 390 +/- 85 mL/min and 2512 +/- 486 kcal/day for the period without sedation. During this period, there was a sign ificant correlation between Vo(2) and mean arterial pressure. For the recovery period, there was no difference in mean or maximum Vo(2) betw een the two groups of patients. At 24 and 48 hrs after cessation of se dation, Vo(2) and energy expenditure decreased to 30% above basal ener gy expenditure. These changes may be due to the recovery of muscular a ctivity, weaning from mechanical ventilation, or an increase in the am ount of circulating catecholamines. Conclusion: In severe head-injured patients, during the first 12 hrs after the discontinuation of sedati on, the patients experienced a large increase in Vo(2), energy expendi ture, and mean arterial pressure. Although these changes have no progn ostic value in our study, they have potential deleterious effects in h ead-injured patients. Methods that blunt these changes which have prov en efficacious in anesthesia may be effective for intensive care patie nts.