Fat Elimination in Acute Renal Failure: Long‐Chain vs Medium‐Chain Triglycerides W. DRUML, M. FISHER, S. SERTL, ET AL American Journal of Clinical Nutrition 55:468–472, 1992

This study compared the metabolism of intravenously infused fat in patients with acute renal failure (ARF) vs that in healthy control subjects, using either a long‐chain triglycerides (LCT) emulsion or a 50:50 mixture of LCT and medium‐chain triglycerides (MCT). The test subjects consisted of seven medical intensive care unit patients who had developed ARF due to various causes (sepsis in two; postoperative pancreatitis, vascular surgery, acute interstitial nephritis, poststreptococcal nephritis, and drugs in one each). These patients were considered otherwise clinically stable and were all close to ideal body weight (109 ± 3% ideal body weight). Prior to this study, the patients had been on parenteral nutrition, which provided 130% of resting energy expenditure and consisted of amino acids (15%), glucose (55%), and LCT lipids (30%). The control subjects were six healthy volunteers of somewhat younger age (32 ± 7 years vs 51.9 ± 4.4 years in the study group) and similar weight (103 ± 5% ideal body weight) and had been on a mixed oral diet providing an average of 8800 kJ/d, 80 g protein, and 35% of calories as fat. Fat clearance and hydrolysis were studied using a two‐stage constant infusion of the fat emulsion, infusing 0.75 g fat per kilogram of body weight per hour for 90 minutes, then 1.25 g fat per kilogram of body weight per hour for the next 90 minutes. The emulsions compared were Intralipid 10% (Kabi‐Vitrum, Stockholm, Sweden) as the LCT product and Lipofundin‐MCT 10% (Braun, Melsungen, Germany) as the 50:50 mixture of LCT and MCT. The infusions were administered after a 12‐hour break in nutrition support and at least 20 hours after the last dialysis in the test patients, and after a 12‐hour overnight fast in the controls. Triglyceride clearance was markedly reduced in ARF (0.53 ± 0.10 vs 1.55 ± 0.30 mL per kilogram body weight per minute) during LCT infusion and showed no improvement with MCT (0.59 ± 0.12 vs 1.93 ± 0.34 mL per kilogram body weight per minute). Elimination half‐lives were accordingly prolonged more than three times in patients with ARF as compared to controls. In both groups, triglyceride hydrolysis, as reflected by the rise in plasma free fatty acids, was higher with MCT than with LCT, but the difference was blunted in patients with ARF. Plasma glucose and lactate levels were not affected by either one of the fat infusions in the controls. In contrast, patients with ARF had significantly higher baseline glucose levels, which rose further (p <.05) with both fat infusions; similarly, their plasma lactate levels started out slightly higher and rose further with both fat infusions. The authors concluded that fat clearance is reduced in ARF and that this impairment is not alleviated by use of MCT.