Effect of Nitrous Oxide on Folate and Vitamin B12 Metabolism in Patients

@article{Koblin1990EffectON,
  title={Effect of Nitrous Oxide on Folate and Vitamin B12 Metabolism in Patients},
  author={Donald D. Koblin and Barbara W. Tomerson and Frederic M. Waldman and George H. Lampe and Linda Z. Wauk and Edmond I. Eger},
  journal={Anesthesia \& Analgesia},
  year={1990},
  volume={71},
  pages={610–617}
}
Exposure to nitrous oxide (N2O) markedly enhances excretion of formic acid and formiminoglutamic acid (FIGLU) in the urine of rats, suggesting a disruption in the normal pathways of folic acid metabolism secondary to an N2O-induced inactivation of methionine synthase. We tested whether surgical patients (23 having total hip replacements and 26 having resection of acoustic neuromas) exposed to isoflurane alone or combined with N2O responded similarly. We found no increase in urinary formic acid… Expand
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TLDR
It is suggested that the effect of nitrous oxide as used in surgical anesthesia may be considered insignificant in patients with normal vitamin-B12 values. Expand
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TLDR
It was concluded that the folate deficiency that develops in the N2O‐treated rat is due to massive urinary loss of folate which appears to be secondary to impaired cellular uptake of folates which leads to a raised plasma folate level. Expand
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TLDR
There is a marked increase in the excretion of formiminoglutamic acid in the urine following exposure to nitrous oxide and a significant decrease is produced, while on N2O, by giving methionine. Expand
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TLDR
There was thus a parallel with megaloblastic anaemia and a working hypothesis for the agranulocytosis and the teratogenesis which had previously been observed as toxic effects of nitrous oxide. Expand
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TLDR
Results in humans are similar to those in animals and suggest that inactivation of methionine synthetase may play a role in the development of the pathologic effects seen in patients and medical personnel after exposure to nitrous oxide. Expand
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TLDR
Megalo‐blastosis was associated with abnormal dU suppression which showed a correction pattern similar to that seen in vitamin Bi2 deficiency and Administration of N20 was also associated with a progressive rise in serum folate and fall in serum methionine levels. Expand
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TLDR
It is suggested that nitrous oxide interferes with the function of vitamin B12 in vitro and probably also in vivo when premixed 50% Nitrous oxide and 50% oxygen mixture ('Entonox') is given. Expand
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TLDR
The addition of N2O administration decreased the isoflurane requirement for clinical anesthesia but did not alter most of the clinical variables measured in practice, including blood pressure, heart rate, rate of recovery from anesthesia, development of postoperative pain, patient satisfaction with anesthesia, or duration of anesthesia or of hospitalization. Expand
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TLDR
The findings are consistent with the hypothesis that nitrous oxide combines with the vitamin B12 molecule of methionine synthase to form a hydroxyl radical that reacts with an inactivates the enzyme, and that DMTU slows this inactivation by scavengingHydroxyl radicals. Expand
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