Is routine blood test of value for evaluating health effects among midwives working with nitrous oxide for pain relief in delivery unit

G. Abascall, M. Johansson, K. J. Jakobsson

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DOI: 10.4236/health.2011.33031                

Abstract

Chronic workplace exposure to high nitrous oxide concentrations has been suggested to potentially be associated to negative health effects caused by the interference with the vitamin B12, methionine synthase pathway. The objective of the present study was to determine if delivery unit work place ambient air nitrous oxide exposure results in detectable hyperhomocysteinemia or signs of macrocytocis in personnel. Blood samples from thirty healthy female fulltime employees, midwives, aged 43 (range 25-62) years were studied. Routine blood test analysed for plasma homocysteine and blood status; haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration, blood status was analysed once before going on vacation and repeated after at least 10 days’ leave, nitrous oxide free period. Median time weighted average was 41 [10 - 547] ppm; 3 out of 11 TWA measurements were above recommended100 ppm limit. Median homocysteine concentrations were 10.7 [5.6 - 16] micromol/L with reference limits of 5.0 – 15 micromol/L. Megaloblastic erythrocytes was not detected in any personnel and no changes in blood status could be detected between before and after a nitrous oxide-free period. Conclusions: One of 3 delivery units’ ambient air quality measures exceed recommended ranges. No signs of routine blood test pathology could be seen in the personnel studied.

Keywords

Nitrous oxide; ambient air quality; TWA; homocysteine; megaloblastic anaemia.

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Krajewski, W., Kucharska, M., Pilacik, B., Fobker, M., Stetkiewicz, J., Nofer, J.R. and Wronska-Nofer, T. (2007) Impaired vitamin B12 metabolic status in healthcare workers occupationally exposed to nitrous oxide. British Journal of Anaesthesia, 99, 812-818. doi:10.1093/bja/aem280
[2]	Krajewski, W., Kucharska, M., Wesolowski, W., Stet-kiewicz, J. and Wronska-Nofer, T. (2007) Occupational exposure to nitrous oxide - the role of scavenging and ventilation systems in reducing the exposure level in op-erating rooms. International Journal of Hygiene and En-vironmental Health, 210, 133-138. doi:10.1016/j.ijheh.2006.07.004
[3]	Henderson, K.A., Matthews, I.P., Adisesh, A. and Hutchings, A.D. (2003) Occupational exposure of mid-wives to nitrous oxide on delivery suites. Occupational and Environmental Medicine, 60, 958-961. doi:10.1136/oem.60.12.958
[4]	Westberg, H., Egelrud, L., Ohlson, C.G., Hygerth, M. and Lundholm, C. (2008) Exposure to nitrous oxide in delivery suites at six Swedish hospitals. International Archives of Occupational and Environmental Health, 81, 829-836. doi:10.1007/s00420-007-0271-3
[5]	Chessor, E., Verhoeven, M., Hon, C.Y. and Teschke, K. (2005) Evaluation of a modified scavenging system to reduce occupational exposure to nitrous oxide in labor and delivery rooms. Journal of Occupational and Envi-ronmental Hygiene, 2, 314-322. doi:10.1080/15459620590959722
[6]	Chanarin, I. (1980) Cobalamins and nitrous oxide: A review. Journal of Clinical Patholology, 33, 909-916. doi:10.1136/jcp.33.10.909
[7]	Louis-Ferdinand, R. T. (1994) Myelotoxic, neurotoxic and reproductive adverse effects of nitrous oxide. Ad-verse Drug Reaction Toxicology Review, 13, 193-206.
[8]	Szymanska, J. (2001) Environmental health risk of chronic exposure to nitrous oxide in dental practice. Annals of Agricultural & Environmental Medicine, 8, 119-122.
[9]	Byhahn, C., Wilke, H.J. and Westpphal, K. (2001) Occu-pational exposure to volatile anaesthetics: Epidemiology and approaches to reducing the problem. CNS Drugs, 15, 197-215. doi:10.2165/00023210-200115030-00004
[10]	Anderson, R.E., Barr, G, and Jakobsson, J.G. (2005) Op-erating room nitrous oxide trace concentrations: A clini-cal study in ambulatory surgery. Ambulatory Surgery, 12, 23-26. doi:10.1016/j.ambsur.2004.10.002
[11]	Ermens, A.A., Refsum, H., Rupreht, J., Spijkers, L.J., Guttormsen, A.B. and Lindemans, J. (1991) Monitoring cobalamin inactivation during nitrous oxide anesthesia by determination of homocysteine and folate in plasma and urine. Clinical Pharmacolology Therapeutics, 49, 385-393. doi:10.1038/clpt.1991.45
[12]	Stabler S.P, Allen R.H, Savage D.G, Lindenbaum J. (1990) Clinical spectrum and diagnosis of cobalamin de-ficiency. Blood, 76, 871-881.
[13]	Deleu, D., Louon, A., Sivagnanam, S., Sundaram, K., Okereke, P. and Gravell. (2000) Long-term effects of ni-trous oxide anaesthesia on laboratory and clinical pa-rameters in elderly Omani patients: A randomized dou-ble-blind study. Journal of Clinical Pharmacy and Thera-peutics, 25, 271-277. doi:10.1046/j.1365-2710.2000.00287.x
[14]	Salo, M., Rajam?ki, A. and Nikoskelainen, J. (1984) Absence of signs of vitamin B12--nitrous oxide interaction in operating the theatre personnel. Acta Anaesthesiologica Scandinavica, 28, 106-108. doi:10.1111/j.1399-6576.1984.tb02021.x