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 Pao2/fraction of inspired oxygen (Fio2) ratio (p = 0.005) compared with LCT emulsion alone. The mean (± SD) Pao2/Fio2 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 Pao2/Fio2 ratio and had a further beneficial effect on oxygen delivery.