• J van der Kooy, J P De Graaf, Z M Kolder, K D Witters, E Fitzpatrick, J J Duvekot, I J J Dons-Sinke, E A P Steegers, and G J Bonsel.
• Department of Obstetrics and Gynecology, Division of Obstetrics & Prenatal Medicine, Erasmus Medical Centre, Rotterdam, The Netherlands. j.vanderkooy@erasmusmc.nl
• Acta Anaesthesiol Scand. 2012 Aug 1;56(7):920-5.

ObjectiveNitrous oxide (N(2) O) is routinely used as an analgesic in obstetrics during labour. Epidemiological studies have linked chronic occupational exposure to N(2) O to specific health problems, including reproductive risks. Occupational exposure limits (OELs) allow the use of N(2) O once appropriate preventive and safety measures have been taken. We assessed the effectiveness of a scavenger system (Anevac P-system®, Medicvent Heinen & Löwestein Benelux, Barneveld, the Netherlands) applied in N(2) O administration during labour in a midwifery-led birthing centre in the Netherlands.MethodsAfter informed consent, non-pregnant midwives were trained to administer N(2) O. N(2) O was delivered as a 50 : 50 mixture with oxygen and was self administered by the patient. The scavenging device, containing a double mask and a chin mask, was connected to the local evacuation system vented outside the building. Data on the 8-h time-weighted average (8-h TWA) as well as the 15-min TWA (15-min TWA) were obtained.ResultsThirteen patients were included. Six patients were included in the first study period. In this period the 8-h TWA was not exceeded, however, in all patients, the 15-min TWA occasionally exceeded the OELs. After four additional measures, seven patients were included. After implementation of these measures, the 8-h TWA and 15-min TWA never exceeded the OELs. System leakage was not observed during both study periods.ConclusionThe Anevac P-scavenging system during N(2) O analgesia in labour prevents exceeding OELs in professional workers. The scavenging system appeared acceptable and effective, and can be considered in hospital settings that use N(2) O as analgesic during labour.© 2012 The Authors. Acta Anaesthesiologica Scandinavica © 2012 The Acta Anaesthesiologica Scandinavica Foundation.

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