Effects of high-dose L-carnitine supplementation on diaphragmatic function in patients with respiratory failure: A randomized clinical trial

Objectives Evaluation of diaphragmatic function by bedside ultrasound provides information on the degree of disability and the response to treatment intervention in respiratory failure patients with associated respiratory muscle fatigue. This study aimed to assess the impact of high and low-dose L-carnitine supplementation on diaphragmatic muscle function. Methods This was a prospective, randomized, controlled clinical trial (trial registration number NCT05322447), for which approval was obtained from our institutional ethics committee (R80/2021). Participating patients were randomly assigned to two groups of 30 patients each. In the low-dose group, L-carnitine was administered at a dose of 6 g/day. The high-dose group received an intravenous infusion of 18 g/day of L-carnitine. On days 0, 3, and 7, diaphragmatic function was assessed by ultrasound, and serum levels of L-carnitine were measured. Results Both diaphragmatic excursion (DE) and diaphragmatic thickening fraction (DTf) measurements were positively correlated with serum L-carnitine levels (+r = 0.58 and +r = 0.61, respectively; p< 0.001). High-dose L-carnitine independently influenced the DE only, both in an unadjusted model (p = 0.04) and after adjustment for age and sex (p = 0.02). However, it had no significant effect on DTf, either before (p = 0.25) or after (p = 0.17) adjustment. Conclusion Serum levels of L-carnitine are positively correlated with the two measures of diaphragmatic function (DE and DTf). Moreover, high-dose L-carnitine supplementation had rapid and significant positive effects on DE. This improvement indirectly enhanced patient outcomes and resulted in shorter stays in the Intensive Care Unit and hospital.