title: Vitamin C supplementation in patients receiving peripheral parenteral nutrition after gastrointestinal surgery.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Surgery, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Yamazaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Horikawa
authors.forename: Ryoji
authors.initials: R
authors.lastname: Fukushima
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001205:Ascorbic Acid / Q000097:blood / Q000494:pharmacology* / Q000652:urine; D019587:Dietary Supplements; D015237:Dinoprost / Q000031:analogs & derivatives / Q000652:urine; D005260:Female; D041981:Gastrointestinal Tract / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000187:drug effects*; D010288:Parenteral Nutrition / Q000379:methods*; D011182:Postoperative Care; D016037:Single-Blind Method; D014815:Vitamins / Q000097:blood / Q000494:pharmacology* / Q000652:urine
chemical_list: D014815:Vitamins; C075750:8-epi-prostaglandin F2alpha; D015237:Dinoprost; D001205:Ascorbic Acid