Hemodynamic and respiratory effects of medium-chain and long-chain triglyceride fat emulsions: A prospective, randomized study

Background: Intravenous fat emulsions (IVFE) containing long-chain triglycerides (LCTs) (chain length 20 carbon atoms) have been associated with adverse hemodynamic and respiratory effects in postoperative on intensive care unit patients. Recently, medium-chain triglycerides (MCTs) (chain length 6 to 12 carbons atoms) have been introduced as a component of IVFE. Objectives: The study was aimed at comparing cardiopulmonary effects of IVFE with different composition (MCTs + LCTs vs LCT-based IVFE). Design: Prospective, double-blind, randomized, parallel-group controlled trial. Setting: Heart surgery postoperative intensive care unit. Patients: With approval of the Institutional Review Board of Human Studies, and after obtaining written informed consent, twenty-six spontaneously breathing patients were enrolled in the study 24 hours after open heart surgery for mitral valve replacement (22 females, 4 males, mean age 57 years, range 35-73). Interventions: Patients were randomized into two groups, to receive 1 mL/kg/hour for two hours (3.3 mg/kg/min) of the LCT-based IVFE or the IVFE containing a physical mixture of MCTs + LCTs (50:50%). Group comparisons were made using repeated measures of ANOVA; main statistical comparisons were made in each group between baseline values and data collected during and after two hours of IVFE infusion (Dunnett multiple comparison test). A p < .05 level was used to establish statistical significance. Measurements and main results: In each group hemodynamic measurements and arterial blood gases were obtained before, during and after (for another two hours) IVFE infusion, at 30' intervals; oxygen transport/utilization parameters and intrapulmonary shunt fraction were also calculated. No change in heart rate, cardiac index, systemic and pulmonary pressures or resistance, central venous and pulmonary capillary pressures, nor in arterial blood gases was observed in the MCTs + LCTs group, as compared to pre-infusion values. IVFE administration reduced the cardiac index (-15% at 60' and 120' of infusion) only in the group receiving the LCT-based IVFE; significant increases in both pulmonary artery pressures and vascular resistances were observed in the same group, with PaO2 decrease during IVFE administration. Oxygen consumption was constantly increased (+15% vs baseline values) during and after MCTs + LCTs infusion. Oxygen delivery was unmodified by LCTs + MCTs, but it was significantly reduced by the LCT-based IVFE. Neither changes in the intrapulmonary shunt fraction nor arrhythmias or adverse clinical reactions were observed during or after the infusion of either IVFE. Conclusions: Unlike IVFE based on LCTs only, MCTs + LCTs IVFE do not exert adverse cardiopulmonary effects at clinically useful doses following valvular heart surgery and could represent a safe source of rapidly metabolized substrates.