Cardiopulmonary effects of lipid emulsions in patients with ARDS.

STUDY OBJECTIVES

Lipid emulsions have been suspected of inducing certain modifications in gas exchange and pulmonary hemodynamics. The aim of this prospective study was to evaluate the hemodynamic and pulmonary effects of two lipid emulsions.

DESIGN

Prospective, randomized, double-blind, crossover study.

SETTING

Medical and surgical ICU in a French university hospital.

PATIENTS

Eighteen patients presenting ARDS.

INTERVENTIONS

Each patient received a 6-h infusion of a 20% fat emulsion containing 100% long-chain triglycerides (LCTs) and a 6-h infusion of 50% LCTs/50% medium-chain triglycerides (MCTs) 20% lipid emulsion at the rate of 1.0 mL/kg/h. An 18-h period with no lipids separated the two periods. An additional 18-h period after the end of the second lipid emulsion administration was observed prior to the final measurements.

MEASUREMENTS AND RESULTS

The MCT/LCT emulsion increased the PaO(2)/fraction of inspired oxygen (FIO(2)) ratio (p = 0.005) compared with LCT emulsion alone. The mean (+/- SD) PaO(2)/FIO(2) ratio increased from 165 +/- 55 to 191 +/- 64 mm Hg after 1 h of LCT/MCT administration (p < 0.03), and to 175 +/- 46 mm Hg after 6 h. Moreover, there was an increase in oxygen delivery after 6 h of LCT/MCT administration (p < 0.001 vs baseline). While a time-related increase in mean pulmonary artery pressure (p = 0.012) during lipid administration was found, no effect of the kind of lipid emulsion was observed. The time-related increase in cardiac index (p = 0.002) was more marked when the patients received the LCT/MCT emulsion (p = 0.002). Pulmonary vascular resistances were not affected by the kind of lipid emulsion.

CONCLUSIONS

The present work showed that while the LCT emulsion induced no deleterious effects on oxygenation in ARDS patients, the LCT/MCT emulsion improved the PaO(2)/FIO(2) ratio and had a further beneficial effect on oxygen delivery.