Impaired vitamin B12 metabolic status in healthcare workers occupationally exposed to nitrous oxide.
BACKGROUND
Previous studies demonstrated inactivation of vitamin B12 by nitrous oxide (N(2)O). The intraoperative exposure to N(2)O was shown to induce megaloblastic anaemia and myelopathy in subjects with subclinical vitamin B12 deficiency. In contrast, no data concerning the influence of occupational exposure to N(2)O on vitamin B12 metabolic status are available to date. In the present study, the vitamin B12 status in operating theatre personnel was assessed in relation to the extent of exposure.


METHODS
Ninety-five operating theatre nurses with the history of exposure to N(2)O and 90 unexposed counterparts were examined. Vitamin B12 and folic acid were measured by immunoassay. Total homocysteine (tHcy), an indicator of impaired vitamin B12 metabolism, was determined by high performance liquid chromatography. N(2)O concentration was monitored by adsorption gas chromatography and mass spectrometry.


RESULTS
No significant differences were found between both groups with respect to haematological parameters and folic acid. However, subjects exposed to N(2)O presented with lower vitamin B12 [372.8 (12.1) vs 436.8 (13.2) pmol litre(-1), P<0.001] and higher tHcy [11.2 (0.5) vs 8.9 (0.5) micromol litre(-1), P=0.006]. The changes in vitamin B12 status were aggravated in subjects exposed to N(2)O in concentrations substantially exceeding occupational exposure limit (180 mg m(-3)) [vitamin B12: 341.9 (17.7) vs 436.8 (13.2) pmol litre(-1), P=0.006; tHcy: 12.9 (0.7) vs 8.9 (0.5) micromol litre(-1), P=0.047].


CONCLUSIONS
Exposure to N(2)O in healthcare workers is associated with alterations of vitamin B12 metabolic status, the extent of which depends on the level of exposure.
Krajewski
W
W
Department of Anaesthesia and Intensive Care Medicine, The Polish Mother Memorial Hospital, Lodz, Poland.
Kucharska
M
M
Pilacik
B
B
Fobker
M
M
Stetkiewicz
J
J
Nofer
J-R
JR
Wronska-Nofer
T
T
D000328:Adult; D018685:Anesthetics, Inhalation / Q000032:analysis / Q000494:pharmacology*; D001800:Blood Specimen Collection / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004784:Environmental Monitoring / Q000379:methods; D005260:Female; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000097:blood; D006801:Humans; D008875:Middle Aged; D009609:Nitrous Oxide / Q000032:analysis / Q000494:pharmacology*; D016273:Occupational Exposure / Q000032:analysis*; D009871:Operating Room Nursing; D009873:Operating Rooms; D014691:Ventilation / Q000379:methods; D014805:Vitamin B 12 / Q000097:blood*
D018685:Anesthetics, Inhalation; D006710:Homocysteine; D005492:Folic Acid; D009609:Nitrous Oxide; D014805:Vitamin B 12