Possible Interaction: Homocysteine and Nitrous Oxide

“Previous studies of patients have shown that anaesthesia with nitrous oxide (N2O) increases the plasma levels of total homocysteine.”

“ Nitrous oxide increases total homocysteine (tHcy) plasma levels, which are associated with an increase in perioperative myocardial ischemia.”

“Implications Use of nitrous oxide during carotid artery surgery induces increases in postoperative plasma homocysteine concentration and is associated with increases in postoperative myocardial ischemia.”

“Postoperatively in the postanesthesia care … and at 48 h the nitrous oxide group had … mean plasma homocysteine concentrations of 15.5 ± 5.9 and 18.8 ± 14.7 when compared with the nonnitrous … of 11.4 ± 5.2 and 11.3 ± 4.0 &mgr;mol/L, P < 0.001.”

“This study reconfirmed that intraoperative nitrous oxide is associated with postoperative increases in plasma homocysteine concentration.”

“Implications: Short-term exposure to nitrous oxide led to significant increases in plasma homocysteine.”

“ Nitrous oxide inhibits methionine synthase, which aids in the conversion of homocysteine to methionine.”

“The change in plasma homocysteine concentrations in the nitrous oxide group was significantly different from that in the nonnitrous group (P = 0.0031).”

“We conclude that the use of intraoperative nitrous oxide leads to significant increases in perioperative plasma homocysteine concentrations.”

“Besides, the N2O metabolic side effects are well-known: N2O , by activating a complex of intracellular signaling pathways through Hcys , can trigger unexpected consequences.”

“We believe that the adhesion prevention property of N2O is possibly related to its well-known side effects: N2O oxidizes the cobalt atoms of the vitamin B12, inactivating the methionine synthase and causing a dose-dependent increase in plasma homocysteine (Hcys) concentrations.”

“The enhancement of homocysteine export rate of some cell types during nitrous oxide exposure probably reflects inhibition of homocysteine remethylation in intact cells, and highlights the utility of extracellular homocysteine as an indicator of metabolic flux through the methionine synthase pathway.”

“ Nitrous oxide alters vitamin B12 and increases the blood levels of homocysteine and methylmalonyl CoA. The magnetic resonance of the spinal cord shows abnormalities in the majority of cases.”

“ Nitrous oxide is known to inhibit methionine synthase, a vitamin B12-dependent enzyme responsible for the breakdown of homocysteine , resulting in homocysteine elevation, and should be avoided in these patients.”

“The nitrous oxide group had significantly higher mean plasma homocysteine concentrations than the nitrous oxide-free group (P = .021).”

“By irreversible oxidation of vitamin B12, nitrous oxide effectively impairs conversion of homocysteine to methionine, and consequently this impairment leads to dose-dependent plasma homocysteine Nitrous Oxide and Cardiovascular Outcome: Perspective from the POISE Trial”