Impact of energy deficit calculated by a predictive method on outcome in medical patients requiring prolonged acute mechanical ventilation

To assess energy balance in very sick medical patient,; requiring prolonged acute mechanical ventilation and its possible impact on outcome, we conducted an obserlational study of the first 14 d of intensive care unit (ICU) stay in thirty-eight consecutive adult patients intubated at least 7 d. Exclusive enteral nutrition (EN) was started within 24 h of ICU admission and progressively increased, in absence of gastrointestinal intolerance, to the recommended energy of 125.5 kJ/kg per d. Calculated energy balance was defined as energy delivered - resting energy expenditure estimated by a predictive method based on static and dynamic biometric parameters. Mean energy balance was -5439 (SEM 222) W per d. EN was interrupted 23% of the time and situations limiting feeding administration reached 64% of survey time. ICU mortality was 72%. Non-survivors had higher mean energy deficit than ICU survivors (P=0.004). Multivariate analysis identified mean energy deficit as independently associated with ICU death (P=0.02). Higher ICU mortality was observed with higher energy deficit (P=0.003 comparing quartiles). Using receiver operating characteristic curve analysis, the best deficit threshold for predicting ICU mortality was 5021 kJ per d. Kaplan-Meier analysis showed that patients with mean energy deficit >= 5021 kJ per d had a higher ICU mortality rate than patients with lower mean energy deficit after the 14th ICU day (P=0.01). The study Suggests that large negative energy balance seems to be an independent determinant of ICU mortality in a very sick medical population requiring prolonged acute mechanical ventilation, especially when energy deficit exceeds 5021 M per d.