Pre‐operative vitamin B infusion and prevention of nitrous oxide‐induced homocysteine increase

Abstract

Summary Nitrous oxide inactivates vitamin B12 with detrimental consequences for folate and methionine metabolism. This inactivation can be clinically detected by an increase in plasma total homocysteine. In a clinical trial, we tested the hypothesis that a preoperative infusion of vitamin B12 and folate prevents the nitrous oxide-induced homocysteine increase. Sixty-three healthy patients scheduled for elective surgery were randomly allocated to receive (a) B-vitamins and nitrous oxide; (b) placebo and nitrous oxide or (c) normal saline and no nitrous oxide. Fifty-nine patients were included in the final study population. After intravenous B-vitamin infusion, plasma vitamin B12 and folate concentrations increased 35-fold and 12-fold on the first postoperative measurement, respectively. Patients who received B-vitamins developed a similar increase (+18%) in homocysteine after nitrous oxide (+ 1.9 μmol.L−1; 95% CI: 0.2 – 3.6 μmol.L−1) as patients who did not receive B-vitamins (+ 22%; + 2.7 μmol/L; 95% CI: 0.6 – 4.8 μmol.L−1). Patients who did not receive nitrous oxide (“air control”) had no change in homocysteine (+ 0.5 μmol.L−1; 95% CI: −0.8 – 1.9 μmol.L−1). This trial indicates that preoperative IV B-vitamins may not prevent nitrous oxide-induced hyperhomocysteinemia.

Nitrous Oxide Anesthesia and Plasma Homocysteine in Adolescents

“…Second, it has been repeatedly shown in more than 6 human studies (>1,000 patients) that in the absence of N 2 O, patients will not develop an increase in postoperative plasma tHcy. 3,4,14,40-42 Based on these preexisting data, it is a reasonable prediction that we would have observed a similar result (no increase in plasma tHcy without N 2 O), if our study had a formal control group.…”

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

“…Woodside et al 26 showed the positive significant effect of vitamin B on plasma homocysteine levels in men. In contrast, Rao et al 7 found intravenous injections of vitamin B to be ineffective on hyperhomocysteinemia after nitrous oxide anesthesia. This inconsistency can be explained by the absence of standard techniques of anesthesia and different durations of exposure to nitrous oxide in the mentioned studies.…”

“…6 During this period, cobalamin-dependent enzymes, namely methionine synthase are inhibited, the ability of the cells to produce methionine from homocysteine is impaired, and consequently plasma homocysteine level increases. [2][3][4][5][6][7] Since homocysteine has atherogenic properties that can lead to endothelial dysfunction, [8][9][10][11] its higher plasma levels augment the risk of myocardial infarction, stroke, and dementia in the general population, particularly in individuals with cardiovascular risk factors. 12,13 Therefore, the effects of elevated plasma homocysteine levels are very important in cardiac patients.…”

“…The only available study on the effects of vitamin B injection on plasma homocysteine levels after nitrous oxide anesthesia revealed the inefficacy of the applied method. 7 Considering limited research and existing controversies in this field, the aim of present study was to evaluate the effects of pre and postoperative single-dose intravenous infusion of vitamin B12 on homocysteine levels in patients receiving nitrous oxide anesthesia.…”

Is Remifentanil Superior to Nitrous Oxide Regarding the Clinical Effects?

“…Çalışmamızdan farklı olarak, Lee ve ark. (13) , yaptıkları çalışmada, remifentanili bolus (1-2 μg kg (15) . Böylece redükte durumdaki kobalaminden okside kobalamin oluşur.…”