Preoperative oral B vitamins prevent nitrous oxide-induced postoperative plasma homocysteine increases

Nitrous oxide increases total homocysteine (tHcy) plasma levels, which are associated with an increase in perioperative myocardial ischemia. We design ed this study to determine whether oral B vitamins, which are cofactors in homocysteine metabolism, can prevent nitrous oxide anesthesia-induced tHcy increases in patients undergoing elective surgery scheduled to last longer than 3 h. Fifty-three patients presenting for elective revision knee or hip arthroplasty received in random, double-blinded fashion oral vitamin B com plex (folate 2.5 mg, B-6 25 mg, and B-12 500 mug) or placebo daily for 1 wk before surgery. Anesthesia was induced with propofol and maintained with a n opioid, isoflurane, and nitrous oxide/oxygen (inspired nitrous oxide > 50 %). Blood samples for measurement of tHcy concentration were obtained at st udy enrollment, before induction, on arrival in the postanesthesia care uni t, and on Day 5. Fourteen patients had their surgery rescheduled after taki ng their vitamins and were removed from the study. The Placebo group had a mean increase in tHcy concentration from baseline of 15% +/- 31% compared w ith the Vitamin group, which had an initial decrease of 9.1% +/- 11% (P = 0 .035). This was maintained throughout the 5-day study period. The use of an oral B vitamin complex prevented the increase in postoperative tHcy by nit rous oxide.