Frequency and duration of ambulance officer exposure to nitrous oxide and methoxyflurane in New Zealand.

OBJECTIVE: Nitrous oxide (Entonox® ) and methoxyflurane (Penthrox® ) are inhaled analgesics administered in paramedicine. Occupational exposure to nitrous oxide has been associated with negative health effects, and may inhibit professional capability. The effect of occupational exposure to methoxyflurane has not yet been clearly determined. This study identifies the frequency and duration of ambulance officer (AO) occupational exposure to nitrous oxide and methoxyflurane to provide a foundation for future assessments of occupational toxicity risk.

METHODS: A retrospective database review of Patient Report Forms (PRFs) in 11 months between February 2016 and February 2018 was conducted. Nitrous oxide was available for the first 5 months studied, followed by 6 months methoxyflurane availability. AO-specific measures of attendance, rate of inhaled analgesic use, and duration of analgesic use were determined. Subgroup analysis by AO qualification and rostered work hours was undertaken.

RESULTS: A total of 46,759 PRFs were examined, identifying 1,033 cases of nitrous oxide administration and 1456 cases of methoxyflurane was administration. There was a significant increase in the proportion of cases where inhaled analgesia was administered following the replacement of nitrous oxide with methoxyflurane. Relative risk of exposure to methoxyflurane compared with nitrous oxide was 1.22, while median duration of each exposure remained unchanged (32 vs. 33 min).

CONCLUSIONS: Methoxyflurane via the Penthrox® inhaler was more likely to be administered than nitrous oxide. Most AOs are infrequently exposed to inhaled analgesics and are exposed for durations slightly greater than previously reported. Relative risk of exposure was greatest for lower-qualified AOs. Peak number of exposures and duration values suggest a subset of AOs with higher occupational health risk.