A preliminary study on cardiopulmonary effects of medium-chain triglyceride (MCT) - enriched lipid emulsions following major valvular heart surgery

The administration of in travenous fat emulsions (IVFE) based on long-chain triglycerides (LCT) has been associated with adverse effects on both hemodynamic status and pulmonary gas exchange, in particular in patients with severe cardiopulmonary disease. No data are currently available on the effects of IVFE enriched with medium-chain triglycerides (MCT) on cardiovascular and respiratory systems under the same clinical conditions. A constant i.v. infusion (1 ml/kg/hour - i.e. 3.3 mg/kg/min - for two hours) of 20% lipid emulsion con taining 50% MCT and 50% LCT was thus administered to 10 spontaneously breathing ICU patients (1 m, 9f, mean age 55 yrs, range 34-67 yrs) starting 18 hours from open heart surgery (mitral valve replacement). Written informed consent for the study was obtained before surgery. Hemodynamic parameters/pulmonary and radial artery indwelling catheters), oxygen and carbon dioxide partial pressures, oxygen saturation, oxygen delivery and consumption, and intrapulmonary shunt were obtained before, during and after lipid infusion, (for two hours), at 30' intervals. No changes in heart rate, cardiac index, systemic and pulmonary pressures and resistances, central venous and pulmonary capillary pressures, and blood gases were observed during infusion. The arterial carbon dioxide partial pressure was constantly reduced throughout and after the end of lipid infusion, as compared to baseline values, while oxygen consumption was significantly increased (p < 0.05 to p < 0.01) without any change in oxygen delivery. No adverse effects on the intrapulmonary shunt were found. Neither arrhythmias nor adverse clinical reactions were observed as a consequence of MCT/LCT infusion. In critically ill cardiac patients 20% MCT/LCT fat emulsions (at 3.3 mg/kg/min or less) do not exert negative cardiopulmonary effects, and could represent a source of rapidly metabolized substrates.