LAUSR

Objectives: To evaluate the interchangeability of oxygen consumption variations measured with the Fick equation (&Dgr;VO2Fick) and indirect calorimetry (&Dgr;VO2Haldane) in critically ill burns patients. Methods: Prospective observational single-center study conducted in a university hospital. Twenty-two consecutive burns patients with circulatory insufficiency and hyperlactatemia (>2 mmol/L) who required a fluid challenge (FC) were included. All patients had cardiac output monitoring (transpulmonary thermodilution technique) and were ventilated and sedated. Simultaneous measurements of VO2Fick and VO2Haldane were performed before and immediately after the FC, at rest, and in hemodynamic conditions stabilized for at least 1 h. VO2Fick and VO2Haldane were measured, respectively, with the standard formulae (using arterial and central venous saturation measured with a blood gas analyzer) and with a metabolic monitor. Results: Forty-four paired measurements of VO2 were obtained. At each timepoint, the median (interquartile range, 25–75) VO2Haldane values were significantly higher than the median VO2Fick values (126 (103–192) vs. 90 (66–149) mL O2/min/m2 (P = 0.004) before FC and 129 (105–189) vs. 80 (54–119) mL O2/min/m2 (P = 0.001) after FC). Correlation between the &Dgr;VO2Fick and the &Dgr;VO2Haldane (%) measurements was poor, with an r = 0.06, (P = 0.77). The mean bias was 8.6% [limits of agreement (LOA): −75.7%, 92.9%]. Conclusions: Analysis of agreement showed poor concordance for the &Dgr;VO2Haldane and the &Dgr;VO2Fick (%) with a low mean bias but large and clinically unacceptable LOA. &Dgr;VO2Haldane and &Dgr;VO2Fick (%) are not interchangeable in these conditions.