Ann Thorac Surg 2003;75:1927-1928
© 2003 The Society of Thoracic Surgeons
Original article: cardiovascular
Invited commentary
Stanley J. Aukburg, MDa,
Albert T. Cheung, MDa
a Department of Anesthesia, Hospital of the University of Pennsylvania, 3400 Spruce StPhiladelphia, PA 19104-4283, USA
e-mail: cheunga{at}uphs.upenn.edu
The report by Mierdl and colleagues demonstrated that occupational exposure to insoluble inhaled anesthetic agents during cardiopulmonary bypass (CPB) exceeded National Institute for Occupational Safety and Health (NIOSH) standards. Ambient desflurane concentrations of 0.62–0.82 ppm exceeded the NIOSH limit of 0.5 ppm even when it was used only before CPB. Environmental contamination would have been greater if inhaled anesthetics were administered during CPB or if the more commonly used soluble agent, isoflurane, was administered.
The hazards of occupational exposure to volatile anesthetics are well established. NIOSH recommends, and other hospital accrediting groups and professional organizations support, that gases inhaled by operating room personnel contain no more than 0.5 ppm of volatile anesthetics and no more than 25 ppm of nitrous oxide. Anesthesia machine standards require scavenging systems that port all waste gases from the breathing circuit to a reservoir for evacuation to the outside atmosphere via a suction system. The scavenging device includes safety features to prevent transmission of excessive negative or positive pressure to the breathing circuit.
Neither the physics of gas elimination nor the risks of occupational exposure are changed when the gas exchange surface is moved from living lung tissue to a synthetic one. Furthermore, gas flows and volatile agent concentrations used for CPB are similar to those used in anesthesia machines. As demonstrated in the current report, it was not surprising that CPB circuits without scavenging systems introduced unsafe levels of anesthetic agents into operating rooms. The problem of environmental contamination by volatile anesthetics during CPB has been reported previously [1–3], but has not been addressed in the surgical literature. In addition, volatile anesthetic use for cardiac operations has increased because it is economical, safe, and facilitates "fast-tracking". More important, there are no standards in practice for preventing unsafe contamination of operating rooms by CPB circuit exhaust gas.
Simple solutions exist for CPB waste gas scavenging, but no commercial devices are available. An explanation for why no progress has been made in addressing this problem is that the handling of anesthetic gases during CPB has not been perceived as the direct responsibility of the anesthesiologist, surgeon, perfusionist, medical device manufacturers, or any other single group. As a result, CPB waste gas scavenging systems are usually improvised, used inconsistently, and may not have safety features to prevent excess pressure from being transmitted to the membrane oxygenator. It is time for a joint committee of anesthesiologists, surgeons, perfusionists, medical device manufacturers and government agency representatives to establish voluntary standards for CPB waste gas scavenging, perhaps under the auspices of the American Society of Testing and Materials (ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959). Designs could be modeled after commercial standards used for anesthesia machine scavenging systems, ASTM F1343-02.
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References
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- Hoerauf K, Harth M, Wild K, Hobbhahn J. Occupational exposure to desflurane and isoflurane during cardiopulmonary bypass: is the gas outlet of the membrane oxygenator an operating theatre pollution hazard? Br J Anaesth 1997;78:378–80
- McNulty SE, Bartkowski R, Schmitz T. Should the gas outlet port on membrane oxygenators be routinely scavenged during cardiopulmonary bypass? J Cardiothorac Vasc Anesth 1992;6:697–9
- Homishak M, Widmer S, Stauffer R. Scavenging anesthetic gas from a membrane oxygenator during cardiopulmonary bypass. J Extra-Corp Tech 1996;28:88–90
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