Effects of Enteral Glutamine and Vitamin C Supplementation on Cytokines and Outcomes in Surgical Intensive Care Unit Patients: A Randomized Clinical Trial

Background: The increased requirement for exogenous glutamine in hypermetabolic states which depletes endogenous glutamine, and supplemental glutamine may be needed in critically ill patients. Vitamin C is an antioxidant that has been suggested to have synergistic effect with glutamine to improve the clinical outcomes. This study aimed to investigate the effects of combined enteral glutamine and vitamin C supplementation on proinflammatory cytokines and clinical outcomes in surgical intensive care unit (SICU) patients. Materials and Methods: This prospective double-blind randomized study enrolled SICU patients who were able to sustain enteral feeding. The treatment (GA) group received glutamine and vitamin C; the placebo (C) group received maltodextrin of equivalent calories. Pre- and posttreatment plasma glutamine, interleukin-6 (IL-6), IL-10, and clinical data were collected and analyzed. Results: Thirty-one patients were enrolled in the GA group, and 10 patients in the C group. The nutritional supplements were equal in calories in both groups, but the GA group had more nitrogen (glutamine) and vitamin C. After intervention, the GA group showed significantly increased plasma glutamine levels and decreased IL-6. The mean c-reactive protein (CRP) level was lower in the GA group. The lengths of SICU stay, APACHE II scores, and infectious complications were less in the GA group. While the mortality of SICU patients was associated inversely with the plasma glutamine level, increased pre-treatment IL-6 was correlated with higher levels of IL-10, CRP and longer stays in the ICU. Higher post-treatment IL-6 levels were observed in patients with infectious complications, SICU and hospital mortality. Conclusions: Early administration of combined enteral glutamine and vitamin C supplementation increases plasma glutamine level and is associated with decreased serum IL-6 levels, reduced APACHE II scores, and infectious complications in SICU patients. Whether an appropriate dosage of glutamine/vitamin C can improve clinical outcomes remains to be determined.