KINETICS OF MEDIUM-CHAIN TRIGLYCERIDES AND FREE FATTY-ACIDS IN HEALTHY-VOLUNTEERS AND SURGICALLY STRESSED PATIENTS

To determine the hydrolysis rate of medium-chain triglycerides (MCTs) to medium-chain free fatty acids (MCFAs) and the disposition rate of M CFAs, five healthy volunteers (H) and eight surgically stressed patien ts (S) received 0.5 mL of Lipofundin 20% per kilogram body weight as a n intravenous bolus. Serum MCTs (C8 and CIO) and MCFAs were measured b y high-performance liquid chromatography during the 120 minutes postin jection. A linear two-compartment model was found to be descriptive an d robust: the apparent volumes of distribution were found to be simila r in healthy and surgical subjects for both MCTs and MCFAs. The first- order transformation rate constant (hydrolysis) from MCTs to, MCFAs wa s not significantly different between the H and S groups (overall 0.11 2 +/- 0.022/min, C8; 0.078 +/- 0.020/min, C10). The rate constant for tissue MCFA uptake from plasma was significantly different between S a nd H subjects both for CIO alone (H: 0.0337 +/- 0.0078; S: 0.1194 +/- 0.0240; P = .020) and for C8 and C10 together (H: 0.0382 +/- 0.0054; S : 0.1012 +/- 0.0168; p = .008), whereas it failed to attain significan ce when C8 alone was considered (H: 0.047 +/- 0.0077; S: 0.0829 +/- 0. 0230, p = .210). These results show that use of MCTs is increased in s urgical patients because of enhanced tissue uptake of the correspondin g free fatty acids, whereas there does not seem to be an increase of M CT hydrolysis in response to acute disease. This would indicate that t he stressed patient is in fact able to effectively use this alternativ e lipid substrate in the face of increased metabolic demand.