Multi-capillary column-ion mobility spectrometry (MCC-IMS) as a new method for the quantification of occupational exposure to sevoflurane in anaesthesia workplaces: an observational feasibility study

Abstract

Background: Occupational exposure to sevoflurane has the potential to cause health damage in hospital personnel. Workplace contamination with the substance mostly is assessed by using photoacoustic infrared spectrometry with detection limits of 10 ppbv. Multi-capillary column-ion mobility spectrometry (MCC-IMS) could be an alternative technology for the quantification of sevoflurane in the room air and could be even more accurate because of potentially lower detection limits. The aim of this study was to test the hypothesis that MCC-IMS is able to detect and monitor very low concentrations of sevoflurane (<10 ppbv) and to evaluate the exposure of hospital personnel to sevoflurane during paediatric anaesthesia and in the post anaesthesia care unit (PACU).

Methods: A MCC-IMS device was calibrated to several concentrations of sevoflurane and limits of detection (LOD) and quantification (LOQ) were calculated. Sevoflurane exposure of hospital personnel was measured at two anaesthesia workplaces and time-weighted average (TWA) values were calculated.

Results: The LOD was 0.0068 ppbv and the LOQ was 0.0189 ppbv. During paediatric anaesthesia the mean sevoflurane concentration was 46.9 ppbv (8.0 - 314.7 ppbv) with TWA values between 5.8 and 45.7 ppbv. In the PACU the mean sevoflurane concentration was 27.9 ppbv (8.0 - 170.2 ppbv) and TWA values reached from 8.3 to 45.1 ppbv.

Conclusions: MCC-IMS shows a significantly lower LOD and LOQ than comparable methods. It is a reliable technology for monitoring sevoflurane concentrations at anaesthesia workplaces and has a particular strength in quantifying low-level contaminations of sevoflurane. The exposure of the personnel working in these areas did not exceed recommended limits and therefore adverse health effects are unlikely.

Keywords: Ion mobility spectrometry; Limit of detection; Occupational exposure; Room air analyses; Sevoflurane; Volatile anaesthetics.

Figure 1

Topographic MCC-IMS plot marking the positions and intensities of the monomer and the dimer of sevoflurane at a concentration of 200 ppbv during calibration with the x-axis indicating the inverse ion mobility involt seconds per square centimeter (Vs/cm ² ) and the y-axis indicating the MCC retention time in seconds (s). Signal intensities are indicated by the peak colour, whereas white indicates lowest and yellow highest signal intensities.

Figure 2

Results of the calibration of the MCC-IMS to sevoflurane concentration of 10–250 ppbv with the graph indicating the 5th order polynomial correlation of the measurements with a coefficient determination index r ²  = 0.993. The solid line indicates the regression line and the dotted lines indicate the 95% confidence intervals.

Figure 3

Results of the room air measurements in the paediatric dental surgical theatre with the whiskers indicating the minimum and maximum concentrations, (☐) indicating the median concentrations, and (○) indicating single measurement data points. General anaesthesia was induced by sevoflurane mask induction and maintained as total intravenous anaesthesia.

Figure 4

Results of the room air measurements in the post anaesthesia care unit (PACU). Measurements were performed between October 27th 2009, 10:00 am and October 29th 2009, 04:30 pm and covered six 8-hour shifts (see Table 5). Sevoflurane concentrations are indicated as columns and the numbers of patients in the PACU after sevoflurane anaesthesia are indicated as (….).