Energy consumption rate of critically ill patients: a prognostic factor?

Introduction

Energy consumption of critically ill patients is increased in relation to basic metabolic rate due to post aggression metabolism. The aim of the present study is to assess the effect of various energy consumption rates in critically ill patients referring to the outcome of these patients.

Materials and methods

40 critically ill patients on a surgical intensive care unit were included in a prospective clinical trial (6 female and 34 male patients). The following criteria for these patients were fixed: mechanical ventilation for at least 3 days, clinical criteria of MODS or SIRS, APACHE-II-score >10, TISS-score >20, total parenteral nutrition for at least 6 days, FiO₂ >40%, informed consent. The basic metabolic rate was calculated daily (Harris-Benedict). Current metabolic rate was measured by indirect calorimetry using a Deltatrac II(Datex-Engström) in the respiratory mode. Data aquisition (oxygen consumption VO₂ and CO₂ production VCO₂) was performed in 6-h periods over average 5.7 days. Energy consumption was determinated by calculation of respiratory quotient. We compared the energy consumption rates with the patients outcome during the trial (14 days).

Results

30 patients survived the first 14 days, 10 patients died due to multi organ failure. The mean calculated basal metabolic rate in the group of survivors was 1662 kcal/24 h, the measured energy consumption was 2109 kcal/24 h. The mean increase was 26.9% in relation to basal rate. Non-survivors had a basal rate of 1653 kcal/24 h, a measured rate of 2097 kcal/24 h. That is a mean increase of 25.4%. The increase in both groups was statistically not significant (t-test, P < 0.05). Energy consumption rates of critically ill patients show no significant differences between survivors and non-survivors during 2 weeks. Deviations of energy consumtion in these patients could not use as a prognostic factor.