Nitrous oxide-induced increased homocysteine concentrations are associatedwith increased postoperative myocardial ischemia in patients undergoing carotid endarterectomy

Nitrous oxide anesthesia causes increased postoperative plasma homocysteine levels. Acute increases in plasma homocysteine are associated with impaire d endothelial function and procoagulant effects. This nitrous oxide-induced plasma homocysteine increase may therefore affect the risk of perioperativ e cardiovascular events. This prospective, randomized study was therefore d esigned to evaluate the effect of nitrous oxide anesthesia and postoperativ e plasma homocysteine levels on myocardial ischemia in patients undergoing carotid endarterectomy. After institutional review board approval and writt en informed consent, 90 ASA Class I-III patients presenting for elective ca rotid endarterectomy were randomized to receive general anesthesia with or without nitrous oxide. Prior to induction, on arrival in the postanesthesia care unit, and after 48 h, blood samples were obtained for homocysteine an alysis. Three hours prior to induction and for 48 h postoperatively patient s were monitored by a three-channel, seven-lead Holter monitor. Postoperati vely in the postanesthesia care unit and at 48 h the nitrous oxide group ha d increased mean plasma homocysteine concentrations of 15.5 +/- 5.9 and 18. 8 +/- 14.7 when compared with the nonnitrous group of 11.4 +/- 5.2 and 11.3 +/- 4.0 mu mol/L, P < 0.001. The nitrous oxide group had an increased inci dence of ischemia (46% vs. 25%, P < 0.05), significantly more ischemia (63 +/- 71 vs. 40 +/- 68 min, P < 0.05), had more ischemic events (82 vs. 53, P < 0.02), and had more ischemic events lasting 30 min (23 vs. 14, P < 0.05) than the nonnitrous group. This study reconfirmed that intraoperative nitr ous oxide is associated with postoperative increases in plasma homocysteine concentration. This was associated with an increase in postoperative myoca rdial ischemia.