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  • Title: A local scavenging system to remove waste anesthetic gases during general anesthesia.
    Author: Li SH, Li SN, Shih HY, Chiou SF, Yi HD.
    Journal: Acta Anaesthesiol Taiwan; 2004 Jun; 42(2):61-7. PubMed ID: 15346700.
    Abstract:
    BACKGROUND: A local scavenging system was constructed and tested in both the operating room and the laboratory to remove the waste anesthetic gases so as to lower the exposure risk of the anesthetic personnel. METHODS: A local scavenging system was developed to suck away the waste anesthetic gases (e.g., N2O and sevoflurane) escaping from the mouth and nostrils of a patient. The local scavenging system used was composed of an inlet funnel (with a diameter of 20 cm), a flexible connecting tubing, a high efficiency particulate air (HEPA) filter and a vacuum pump. To help evaluate the performance of the local scavenging system, a tracer gas (SF6) of a fixed concentration (= 200 ppm) and flow rate (= 5 l/min) was introduced around the nostrils of the patient during anesthesia. The concentrations of the gases (SF6, N2O and SEV) drawn away by the scavenging system were then determined by an extractive Fourier transform infrared (FTIR) spectrometer and those spreading around the breathing zone of the anesthesiologist were obtained by the other FTIR. In the laboratory tests, the relationship between the scavenging efficiency and the inlet funnel position was obtained using the aforementioned SF6-FTIR techniques. RESULTS: With the application of this local scavenging system, during three surgical operations, the average personnel exposure concentrations of N2O and sevoflurane (SEV) as measured were 8.7 and 0.06 ppm, respectively. Both measured concentrations were lower than the TWA values recommended by the US-NIOSH for N2O (= 25 ppm) and SEV (= 2 ppm). Based on the tracer gas (SF6) results, it was found that the average scavenging efficiency was equal to 87%, which was lower than the laboratory testing results of 95%. The (scavenging) efficiency difference between the laboratory and on-site tests could be due to the movement and action of the anesthesiologist during anesthesia. To optimize the performance of the local scavenging device, the inlet (funnel) should be placed close to the breathing region (e.g., noses and mouth) of the patient in the front direction. CONCLUSIONS: The application of the local scavenging system was found to greatly reduce the concentrations of the waste anesthetic gases (e.g., N2O and SEV) to the levels lower than those recommended by the US-NIOSH. With this scavenging device, the exposure health risk of the anesthesiologists could be greatly reduced.
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