title: Isoflurane leakage from non-rebreathing rodent anaesthesia circuits: comparison of emissions from conventional and modified ports.
abstract: Chronic exposure to low levels of fluorocarbon-based waste anaesthetic gas (WAG) has been linked to a multitude of human health problems. We have shown that isoflurane exhaust from passive gas-scavenging canisters is often quite high when using conventional rodent anaesthesia protocols and equipment. Another likely source of WAG build-up in rodent procedure rooms is leakage at the interface between the breathing circuit and the animal's face. We evaluated this possibility using three non-rebreathing circuits: traditional Bain, modified Bain, and Mapleson (type E). For the Mapleson E circuit, a conical rodent facemask was attached and used in one of two configurations: normal aperture, or aperture modified with a latex diaphragm (cut from an unpowdered surgical glove) to reduce the orifice diameter and tighten the seal. Adult female Sprague-Dawley rats were anaesthetized with isoflurane (5% for induction, 2% or 3.5% for maintenance) in oxygen (2 L/min for induction, 1 L/min for maintenance). Isoflurane leakage was assessed by real-time spectrophotometry. In 94% of the trials, three configurations - traditional Bain, modified Bain, and Mapleson E with unmodified mask - permitted isoflurane leakage approaching or exceeding 100 ppm at the face/port interface. In contrast, the Mapleson circuit with diaphragm-modified mask emitted significantly (P<or=0.0003) less isoflurane (peak of 9.5+/-1.7 ppm [mean+/-standard error]). These data indicate that (1) WAG leakage from standard rodent non-rebreathing circuits is substantial, and that (2) a simple, rapid, and economical modification to a conventional rodent facemask can significantly reduce WAG exposure to workers performing many rodent anaesthesia procedures in one session.
authors.affiliation: Department of Laboratory Animal Resources, Amgen Inc, Thousand Oaks, California, USA. smithj@amgen.com
authors.forename: J C
authors.initials: JC
authors.lastname: Smith
authors.forename: B
authors.initials: B
authors.lastname: Bolon
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D000769:Anesthesia, Inhalation / Q000009:adverse effects / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000032:analysis*; D000818:Animals; D005260:Female; D015920:Gas Scavengers / Q000662:veterinary; D006801:Humans; D007530:Isoflurane / Q000032:analysis*; D016273:Occupational Exposure / Q000009:adverse effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000395:Air Pollutants, Occupational; D018685:Anesthetics, Inhalation; D007530:Isoflurane