Objectives: Ambulance officers administering methoxyflurane as an inhalational analgesic may be exposed to trace vapor. Fluoride is a methoxyflurane metabolite, and has been associated with acute renal failure in anesthesia patients and skeletal fluorosis with chronic elevated serum levels from other sources. However, there has been no direct measurement of serum fluoride in occupationally exposed ambulance officers. Thus, this study directly measures serum fluoride over a prolonged period in order to determine renal toxic and skeletal fluorosis risk to ambulance officers who are administering methoxyflurane.
Material and methods: Serum inorganic fluoride concentrations were measured in a prospective observational study of 12 emergency medical technicians (EMTs). The study took 7 serum fluoride measurements over 24 months. A meta-analysis of healthy adult serum fluoride ranges was also conducted.
Results: The typical healthy adult serum fluoride range was determined to be 0.21-2.11 μmol/l (p < 0.001). The EMTs' baseline median (IQR) serum fluoride concentrations were 0.4 μmol/l (0.2; 1.0) with maximum 1.6 μmol/l. The EMTs' overall median serum fluoride was 0.4 μmol/l (0.2; 1.3) with maximum 4.0 μmol/l, usually within healthy reference ranges. All results were ≤10% of the suggested single-dose renal toxic threshold. One result was above a threshold for skeletal fluorosis. The highest measured serum fluoride was 24% of the lowest level associated with radiologic evidence of fluorosis. There was no evidence overall of increasing serum fluoride levels.
Conclusions: There was no evidence that EMTs' exposure to methoxyflurane resulted in sustained increased serum fluoride. These results imply EMTs' occupational safety from acute renal toxicity when activated carbon filtration is used on patient exhalation. However, 1 serum fluoride result above a skeletal fluorosis threshold suggests that the risk of mild skeletal fluorosis cannot be excluded. Int J Occup Med Environ Health. 2021;34(6):767-77.
Keywords: ambulances; fluoride poisoning; fluorides; meta-analysis; methoxyflurane; prospective studies.
This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.