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

Abstract

To investigate the gas exchange and pulmonary haemodynamic responses to two different intravenous fat emulsions in patients with acute respiratory distress syndrome (ARDS). Prospective, randomized, double-blind, placebo-controlled study. Intensive care unit in a university-affiliated hospital. 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. Patients were assigned to three groups (n = 7 each): group A (LCT) received long-chain triglycerides (20% LCT), group B (MCT/LCT), medium-chain triglycerides/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 ml in each group. 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. During LCT infusion, cardiac output, oxygen consumption and oxygen delivery increased (all 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. 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 O2 consumption.