Personnel exposure to waste sevoflurane and nitrous oxide during general anesthesia with cuffed endotracheal tube.

Background: Waste anesthetic gases may have adverse effects on the health of operating room personnel. To reduce the risk of exposure, the United States National Institute of Occupational Safety and Health (US-NIOSH) recommends a time-weighted average (TWA) of 25 ppm (part-per-million) for nitrous oxide (N2O) and a ceiling of 2 ppm for sevoflurane (SEV). This study investigated the concentrations of these two gases in the atmosphere of operating room to which the working personnel (anesthetists) were exposed during anesthetic practice.

Methods: An extractive Fourier transform infrared (FTIR) spectrometer, with an optical path length of 10 meters, was used to monitor the concentrations of waste general anesthetics in the operating rooms. The FTIR in application could simultaneously determine the concentrations of several gases in a near real-time manner, which helped to accurately obtain the varying concentrations of gases in different anesthetic condition. The sampling Teflon tube of the FTIR was conveniently installed in the breathing zone of the anesthetic personnel to obtain the personal exposure concentrations of N2O and SEV.

Results: Nitrous oxide (N2O) and sevoflurane (SEV) concentrations for five surgeries in four different operating rooms were determined. In normal condition during maintenance, the SEV concentrations as measured were less than 2 ppm but the average N2O concentration was greater than 25 ppm. In addition, in three abnormal or specific conditions, the N2O and SEV concentrations increased dramatically. Firstly, at the end of maintenance (right before emergence), peak concentrations of 751 ppm for N2O and 26 ppm for SEV were measured. These unusually high concentrations resulted from flushing the tubing of the anesthetic machine to speed up the emergence of wakefulness of the patient from anesthesia. Secondly, when the cuff of the endotracheal tube was not well inflated or unserviceable, peak concentrations of 631 ppm for N2O and 32 ppm for SEV were measured. Thirdly, malfunction of or loose connection (or disconnection) between the anesthetic machine and the exhaust venting system of operating theater almost doubled the N2O and SEV concentrations.

Conclusions: To decrease the exposure of the operating personnel to waste anesthetics, minimization of the use of N2O is recommended. Besides, the three extraordinary conditions as disclosed in this study were tubing flushing, illy managed endotracheal tube cuff and disconnection of scarvenging system, the first of which sometimes is unavoidable but the last two of which should be avoided.