Investigations of some aspects of atmospheric pollution by anaesthetic gases. I: Diffusion of halothane across plastic and rubber tubes.
Plastic and rubber tubing, of the types used frequently to convey anaesthetic gases to and from the patient, or anaesthetic waste gases out of the operating theatre, were assessed for their capacity to allow diffusion of halothane through the tube wall. The magnitude of this effect has been calculated in relation to pollution of the operating theatre atmosphere under different circumstances.
Anaesthetic uptake and washout characteristics of patient circuit tubing with special regard to current decontamination techniques
The amounts of halothane and isoflurane trapped after exposure for up to 3 h at 2 MAC in commonly used anaesthesia circuit tubing were quantitated by gas chromatography. The decontaminating effects of procedures such as flushing with oxygen, thermal disinfection and/or routine storage were assessed in a similar way. After halothane exposure, anaesthetic content was highest in silicone (398 ± 55 mg 100 g‐1). Lower quantities were found in all other tubings investigated (electrically conductive latex: 64 ± 4, conductive rubber: 62 ± 4, polyethylene‐vinyl‐acetate (PEVA): 293 ± 10 and 149 ± 17 for non‐conductive corrugated and spiral tubes, respectively, polysulfone (Hytrel®): 155 ± 10 mg 100 g‐1). The isoflurane contents were substantially lower (silicone: 278 ± 23; others: 55 ± 7, 61 ± 6, 163 ± 9 and 86 ± 8, 74 ± 4 mg 100 g‐1). The tubings' content did not correlate with the material's partition coefficient as full saturation was not achieved during exposure. Decontamination procedures reduced the content of volatile anaesthetics to a variable extent. Conductive latex and rubber showed the highest residual content, even after thermal disinfection and subsequent storage. Twenty‐minute flushing with oxygen (8 1 min‐1) decreased effluent gas concentrations below 5 p.p.m. in all tubings. With silicone, after 1 h flushing, halothane concentrations still exceeded 10 p.p.m. (isoflurane: 8 p.p.m.). It is concluded that urgent decontamination by a 20‐min flush warrants the safe re‐use of previously ‘contaminated’ conductive rubber and latex as well as polysulfone tubings in critical situations, e.g. in malignant hyperthermia patients if disposable tubing is not immediately available. In contrast, we warn against re‐using silicone and disposable PEVA tubing because of high uptake and considerable release during desorption.
Chronic exposure to anesthetic gases in the operating room.
Halothane present in the ambient atmosphere was continuously measured in each of two operating rooms during the conduct of surgical anesthesia. Concentrations were determined on-line with a mass spectrometer and found to vary with sampling site, breathing system used, and the scavenging system employed to remove overflow anesthetic gases. Concentrations of halothane measured within a 3-foot radius of the anesthesia equipment averaged 8.7 ppm when a nonrebreathing circuit was used (flow 10 l/min), and 4.9 ppm with a semiclosed circle system (flow 4–5 l/min). End-tidal concentrations of halothane averaged 0.21 ppm in 81 samplings from operating room nurses and 0.46 ppm in 36 samplings from anesthetists. Residual concentrations were present in many individuals 16 hours after exposure. A significant reduction in atmospheric contamination of the operating room was obtained by use of appropriate scavenging equipment. The implications of these findings are discussed.