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Metabolic effects of repeated exposure to nitrous oxide: a preliminary report
Author(s) -
Chen H.,
Lovell M.,
Baines D.,
De Lima J.,
Ahearn V.,
Wilcken B.,
Curtin J.,
Carpenter K.
Publication year - 2010
Publication title -
pediatric anesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.704
H-Index - 82
eISSN - 1460-9592
pISSN - 1155-5645
DOI - 10.1111/j.1460-9592.2010.03280_2.x
Subject(s) - medicine , vitamin b12 , nitrous oxide , adverse effect , methylmalonic acid , prospective cohort study , repeated measures design , anesthesia , cohort , population , statistics , mathematics , environmental health
Background: N 2 O irreversibly inhibits the vitamin B12‐dependent enzyme, methionine synthase, and has the potential to cause hematological, neurological and cardiovascular adverse effects [1–5]. Repeated exposure to N 2 O is common in certain pediatric settings (burns dressing and radiotherapy). There are no published clinical studies investigating the effects of nitrous oxide anesthesia on vitamin B12 and folate metabolism in a pediatric population. Aims: To study the effect of repeated exposure to N 2 O on metabolic indices in a cohort of children predisposed to metabolic and nutritional disturbance. Method: In an on‐going, prospective study of children undergoing radiotherapy for cancer, homocysteine, methylmalonic acid, vitamin B12, folate and red cell indices were measured at regular intervals. Results were correlated with cumulative N 2 O exposure in those children who required repeated general anesthesia. Results: Forty children have been studied so far. Fifteen required general anesthesia to complete therapy. Median exposure to N 2 O was 28 min per exposure for an average of 13 exposures. The median cumulative exposure to N 2 O in this cohort was 397 min. Four children each had a cumulative exposure of more than 15 h. In these cases, nitrous oxide was delivered in 30 or more anesthetics over periods ranging from 6 to 11 weeks. Preliminary results show that homocysteine levels are not consistently correlated with N 2 O exposure. No clinical or biochemical adverse effects related to the gas have been detected. Conclusion: This interim analysis suggests that repeated N 2 O has a marginal effect on vitamin B12 metabolic indices in predisposed children. The study is on‐going. This study is supported by a grant from SPANZA. References 1 Nunn JF. Clinical aspects of the interaction between nitrous oxide and vitamin B12. British Journal of Anaesthesia 1987; 59 :3‐13 2 Myles PS, Leslie K, Chan MTV, Paech MJ, Peyton P, Pascoe E. Avoidance of nitrous oxide for patients undergoing major surgery: a randomised controlled trial. Anesthesiology 2007; 107 :221‐231. 3 Nagele P, Zeugswetter B, Wiener C, Burger H, Hupfl M, Mittlbock M et al. Influence of methylenetetrahydrofolate reductase gene polymorphism on homocysteine concentration after nitrous oxide anesthesia. Anesthesiology 2008; 109 :36‐43. 4 Badner NH, Beattie WS, Freeman D, Spence JD. Nitrous oxide induced increased homocysteine concentrations are associated with increased postoperative myocardial ischemia in patients undergoing carotid endarterectomy. Anesthesia and Analgesia 2000; 91 :1073‐1079. 5 Badner NH, Drader K, Freenab D, Spence JD. The use of intraoperative nitrous oxide leads to postoperative increases in plasma homocysteine. Anesthesia and Analgesia 1998; 87 :711‐713