INFLUENCE OF BODY-TEMPERATURE, WITH OR WITHOUT SEDATION, ON ENERGY-EXPENDITURE IN SEVERE HEAD-INJURED PATIENTS

Objective: To quantify the effect of body temperature and sepsis on en ergy expenditure in head injured patients. Design: Prospective, nonran domized, observational study, Setting: Neurosurgical intensive care un it, Patients: Severe head-injured patients, Interventions: Use of an i ndirect calorimeter to measure energy expenditure. Measurements and Ma in Results: Mean arterial pressure (MAP), heart rate (HR), body temper ature, and mean hourly energy expenditure were recorded. Twenty four p atients had 1,919 hourly measures of the above parameters, The measure ment periods were divided into four groups, according to the anestheti c agents used for sedation: fentanyl and midazolam (group FM); fentany l, midazolam, and curarization (group C); thiopental (group T); and no sedation (group NS), The energy expenditure/basal energy expenditure ratio (EE/BEE) was significantly lower in group T (1.20 +/- 0.15) than in group FM (1.32 +/- 0.24) or group C (1.32 +/- 0.20) and was signif icantly higher in group NS (1.60 +/- 0.33). There was a significant co rrelation between body temperature and EE/BEE (p < .0001, r(2) = .27) only in sedated patients, Using the equation of the regression line to correct energy expenditure for differences in body temperatures betwe ens groups, the difference in energy expenditure between groups with s edation disappeared, This finding suggested that the low energy expend iture under thiopental was due only to hypothermia. Sepsis significant ly increased energy expenditure independently of fever, There was a we ak but statistically significant correlation between energy expenditur e and HR (p < .01, r(2) = .13) but not between energy expenditure and MAP. Conclusions: Sedation had a major effect on energy expenditure. I n sedated patients, body temperature was the main determinant of energ y expenditure; the anesthetic agent used had little influence on the l evel of energy expenditure. Sepsis increased energy expenditure indepe ndently of fever, probably through hormonal changes.