Effect of Nitrous Oxide Exposure During Surgery on the Homocysteine Concentrations of Children

Abstract

In this study we determined the effect of nitrous oxide (N 2 O) on homocysteine concentrations in children and whether blood levels of folate, vitamin B12, B6, methylmalonic acid (MMA) and methylenetetrahydrofolate reductase C6777T genotype affected this relationship. Homocysteine was measured before and after N 2 O. Vitamin levels, MMA and genotype were determined preoperatively. Median age of the 32 participants was 11 months (3-126 months). All children had folate and B6 levels above deficiency values (7.4, 20nmol/L respectively). Five children had MMA levels indicating deficiency (≥0.21µmol/L). Postexposure homocysteine concentrations increased by 25% (P= <0.001). Duration of exposure and initial homocysteine concentrations were predictors of the increase (r 2 = 0.821, P= <0.001).Vitamin B12 and initial homocysteine concentrations were inversely associated (r 2 = 0.277, P= 0.004). Folate, vitamin B6 and genotype showed no effect. In conclusion, N 2 O exposure leads to increased homocysteine in children. Studies investigating benefit of pre-surgical vitamin B12 supplementation may prove worthwhile.iii ACKNOWLEDGMENTS

Health Effects Associated With Exposure to Anesthetic Gas Nitrous Oxide-N2O in Clinical Hospital – Shtip Personel

“…Exposure to nitrous oxide causes a moderate increase in the tone of the sympathetic system with subsequent moderate vasoconstriction of the splanchnic vascular system leading to a reduction in v. portae blood flow and moderate vasoconstriction of the hepatic arterial system. As mentioned above, nitrous oxide is known as an inhibitor of the enzyme methionine synthetase in the liver, so long-term exposure can lead to toxic hepatic effects [ 16 - 19 ].…”

The Effect of Vitamin B12 Infusion on Prevention of Nitrous Oxide-induced Homocysteine Increase: A Double-blind Randomized Controlled Trial

“…20 Also, many case studies have shown subacute combined degeneration after nitrous oxide anesthesia. [21][22][23] Pichardo et al 24 evaluated children undergoing plastic surgery. Similar to our findings, they reported that nitrous oxide anesthesia for longer than two hours significantly increased serum homocysteine levels during the first 24 hours after the surgery.…”

Should nitrous oxide ever be used in oncology patients receiving methotrexate therapy?

“…One small paediatric study showed significant correlation between plasma homocysteine rises in response to N2O and pre-operative vitamin B12 levels 46…”