Gas exchange and pulmonary haemodynamic responses to fat emulsions in acute respiratory distress syndrome

Objective:To investigate the gas exchange and pulmonary haemodynamic responses to two different intravenous fat emulsions in patients with acute respiratory distress syndrome (ARDS). Design: Prospective, randomized, double-blind, placebo-controlled study. Setting: Intensive care unit in a university-affiliated hospital. Patients: 21 patients with ARDS [mean age, 57 +/- 3 (SEM) years; Acute Physiology and Chronic Health Evaluation II, 20 +/- 3; Murray's score, 2.85 +/- 0.12] consecutively admitted. Interventions: Patients were assigned to three groups (n = 7 each): group A (LCT) received long-chain triglycerides (20 % LCT), group B (MCT/LCT), medium-chain trigly cerides/long-chain triglycerides (20 % MCT/LCT: 50/50) and group C placebo (0.9 % sodium chloride, NaCl). The infusion was always given at the rate of 2 mg/kg min over a total period of 12 h, with a volume infusion of 500 mi in each group. Measurements: Data were collected before, immediately after and 12 h after infusion ceased. Pulmonary and systemic haemodynamic and gas exchange variables were measured at each time point. Serum triglyceride cholesterol, and non-esterified fatty acids levels were measured. Results: During LCT infusion, cardiac output, oxygen consumption and oxygen delivery increased tall p < 0.05), whereas pulmonary haemodynamics, arterial oxygen tension, mixed venous partial pressure of oxygen and venous admixture ratio remained essentially unaltered. No changes were observed following MCT/LCT infusion. Conclusions: The administration of LCT emulsion given at a slow rate did not alter arterial oxygenation because of the beneficial effect of a high cardiac output, hence offsetting the detrimental effect of increased O-2 consumption.