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ANESTHETIC PHARMACOLOGY

Preoperative Oral B Vitamins Prevent Nitrous Oxide-Induced Postoperative Plasma Homocysteine Increases

Neal H. Badner, MD FRCP(C)^*, Dave Freeman, PhD, and J. David Spence, MD FRCP(C)

Departments of *Anesthesiology, Clinical Pharmacology, and Clinical Neurosciences, University of Western Ontario, London, Ontario, Canada

Address correspondence to Dr. N. H. Badner, Department of Anesthesiology, University Campus, London Health Sciences Center, 339 Windermere Road, London, Ontario Canada N6A 5A5. Address e-mail to nbadner{at}uwo.ca Reprints will not be supplied.

Nitrous oxide increases total homocysteine (tHcy) plasma levels, which are associated with an increase in perioperative myocardial ischemia. We designed 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 complex (folate 2.5 mg, B₆ 25 mg, and B₁₂ 500 µg) or placebo daily for 1 wk before surgery. Anesthesia was induced with propofol and maintained with an opioid, isoflurane, and nitrous oxide/oxygen (inspired nitrous oxide >50%). Blood samples for measurement of tHcy concentration were obtained at study enrollment, before induction, on arrival in the postanesthesia care unit, and on Day 5. Fourteen patients had their surgery rescheduled after taking their vitamins and were removed from the study. The Placebo group had a mean increase in tHcy concentration from baseline of 15% ± 31% compared with 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 nitrous oxide.

IMPLICATIONS: The use of nitrous oxide anesthesia increases postoperative homocysteine concentrations and associated myocardial ischemia. This study indicates that a 1-wk course of oral B vitamins can prevent the increase in homocysteine from nitrous oxide, and, by implication, myocardial ischemia as well.

This article has been cited by other articles:

				P. S. Myles, M. T. V. Chan, K. Leslie, P. Peyton, M. Paech, and A. Forbes Effect of nitrous oxide on plasma homocysteine and folate in patients undergoing major surgery Br. J. Anaesth., June 1, 2008; 100(6): 780 - 786. [Abstract] [Full Text] [PDF]

				M. Enlund B Vitamins and Nitrous Oxide Anesth. Analg., September 1, 2002; 95(3): 787 - 787. [Full Text] [PDF]