Vitamin C supplementation in patients receiving peripheral parenteral nutrition after gastrointestinal surgery.

OBJECTIVE: We investigated an adequate vitamin C dose during peripheral parenteral nutrition therapy in patients after gastrointestinal surgery by measuring blood concentrations and urine excretions of vitamin C. We also sought to identify the effects of vitamin C on the oxidative status. METHODS: In a randomized trial, 2 d after undergoing gastrointestinal surgery, 16 patients started to receive a 5-d continuous intravenous infusion of vitamin C, either 100 or 500 mg/d. Blood concentrations of vitamin C and inflammatory and immunologic parameters were measured preoperatively, the day after surgery, and 3 and 5 d after starting administration of vitamin C (day 3 and day 5). Also, excretions of vitamin C and oxidative stress markers in 24-h, cumulative urine samples, collected and stored under light protection at 0°C, were measured on day 3 and day 5. RESULTS: Mean blood vitamin C concentration decreased markedly after surgery. The concentration returned to normal on day 3 and on day 5 in the 500-mg group and only on day 5 in the 100-mg group. Concentrations differed significantly between the groups on day 3 and on day 5 (P < 0.001 for both days). Urinary vitamin C excretion was above normal on both days in the 500-mg group, but it never reached normal in the 100-mg group (P < 0.001 for both days). Urinary excretion of 8-isoprostane, a marker of oxidative stress, was significantly lower in the 500-mg than in the 100-mg group on day 3 (P = 0.002). CONCLUSION: Vitamin C dose of 500 mg/d, not 100 mg/d, is adequate for patients undergoing gastrointestinal surgery and receiving peripheral parenteral nutrition therapy. Vitamin C may decrease postsurgical oxidative stress.

Vitamin C requirement in surgical patients.

PURPOSE OF REVIEW: To summarize recent findings on vitamin C status and assess the requirement and optimal dose of supplementation in surgical patients. RECENT FINDINGS: Blood vitamin C concentration falls after uncomplicated surgery and further decreases in surgical intensive care unit patients. The decline may be owing to increased demand caused by increased oxidative stress. To normalize plasma vitamin C concentration, much higher doses than the recommended daily allowance or doses recommended in parenteral nutrition guidelines are needed in these patients. In uncomplicated surgical patients, more than 500 mg/day of vitamin C may be required, with much higher doses in surgical intensive care unit patients. In uncomplicated gastrointestinal surgery, continuous parenteral administration of 500 mg/day of vitamin C reduced postoperative oxidative stress as manifested by reduced urinary excretion of isoprostane. In some studies, postoperative atrial fibrillation was prevented after cardiac surgery by perioperative vitamin C supplementation. In critically ill patients, some prospective randomized controlled trials support parenteral supplementation of high doses of vitamin C, E and trace elements. SUMMARY: Vitamin C requirement is increased in surgical patients, and the potential advantage of supplementation is to increase the plasma and tissue levels of vitamin C and thereby reduce oxidative stress. Although some clinical benefits of high-dose vitamin C supplementation have been shown in the critically ill, the optimal dose for supplementation and the clinical benefits remain to be investigated in surgical patients.