The Dangers of WAG

The Dangers of Regular Exposure to WAG

Chronic, low-level exposure of health care professionals to waste anesthetic gases has been linked to increased incidences of neurologic and reproductive dysfunction, hepatic and renal toxicity, and neoplasia.

All halogenated agents are classified as potent central nervous system depressants. Exposure to halogenated agents in the workplace increases the risk of addiction by sensitizing the reward pathways in the brain, promoting substance use.  To learn more about how WAG can affect you in your place of work, click the links on this page.


This article (below) is particularly interesting to those using induction chambers as it explains the reason for a long and stressful induction time: 

The authors of this article demonstrate: when filling an induction chamber using traditional methods, anesthetic gas does not fill the chamber uniformly, attenuating the effects of anesthetic induction. Anesthetic gas fills the chamber at various levels throughout the chamber.  This causes the animal to search for the area in the chamber where they find the lease amount of anesthetic gas (e.g., the top corner of the chamber).  It can take as long as 7 minutes for the top portion of an induction chamber to reach 3% isoflurane, resulting in a delayed and stressful induction.  

This paper is not available for free download

Induction of anaesthesia with halothane and isoflurane in the rabbit: a comparison of the use of a face-mask or an anaesthetic chamber. P.A. Flecknell, I.J. Cruz, J.G. Liles & G. Whelan. Laboratory Animals (1996) 30, 67-74
(note the word anesthesia is spelled as it is printed in the publication).

In the following publication (below), liquid isoflurane was injected into a vaporization tray mounted to the interior surface of the chamber lid. Their results indicate a significantly shorter interval until recumbency and a smoother induction.  Although this was not discussed by the authors of this paper, we believe it demonstrates; when anesthetic gas is introduced to the chamber in a way that disrupts the flow into the chamber, the chamber is immersed with anesthetic gas efficiently and quickly. 

This paper is not available for free download

Comparison of anesthetic induction in cats by use of isoflurane in an anesthetic chamber with a conventional vapor or liquid injection technique.  Renee D. Schmid, DVM; David S. Hodgson, DVM, DACVA; Rose M. McMurphy, DVM, DACVA, DACVECC July 2008 Journal of the American Veterinary Medical Association 233(2):262-6

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This paper was published following development of the first prototype of the Induction Chamber Evacuation system.  The first prototype was fashioned of a small, hand held, vacuum cleaner.  The small collection bag was removed, this became a blower. The blower was connected to plastic tubing and linked into the induction chamber anesthetic system.  When turned on, the blower would flush WAG from a small induction chamber (1 - 5 liters, like those used for rats and mice in medical research).  In this paper we demonstrated that using a flushing system to remove WAG from an induction chamber, did not alter the time to recovery when the animal was removed from the chamber.  We also demonstrated that using a flushing system did not alter the effectiveness of an activated charcoal filter. Additionally, we demonstrated when activated charcoal canisters, with vents at the bottom, were placed on their sides the activated charcoal would settle, creating dead space within the canister. Waste gas would follow the path of least resistance, enter the canister, pass through the dead space, and exit the canister unchanged.  
The evacuation system became more efficient when the design changed to removing WAG from the induction chamber with a vacuum. We worked with The University of Michigan's OSEH. We measured less than 2ppm of WAG in air samples collected 2cm over the opened lid, after filling and evacuating with a vacuum. We did not publish results.

Flushing Induction Chambers Used for Rodent Anesthesia to Reduce WAG, Janet Wolforth

For information on the risk of increased risk of addiction:

Occupational Exposure & Addictions for Physicians: Case Studies and Theoretical Implications
 
Links:

Anesthetic Gases: Guidelines for Workplace Exposures 

A case report of personal exposures to isoflurane during animal anesthesia procedures.

Evaluation of waste isoflurane gas exposure during rodent surgery in an Australian university.

Research Studies on the Dangers of WAG:

As early as 1967 there were reports from the Soviet Union, Denmark, and the United States (Vaisman 1967Askrog and Petersen 1970Cohen, Bellville, and Brown 1971) that exposure to anesthetic agents including halothane may cause adverse pregnancy outcomes in health-care personnel.

Assessment of Occupational Exposure...: Source: Journal of the American Association for Laboratory Animal Science Volume 37, Number 6, November 1998, pp. 64-67(4)

One (Popova et al. 1979) reported fetal resorption in rats at 9 parts per million.

Several animal studies in rats, mice and hamsters showed embryolethal and teratogenic effects and supported the findings in humans (Basford and Fink 1968Wharton et al. 1979), although often at quite high concentrations (3000-6000 ppm which would not be an unexpected result of opening a 7 or 10 gallon induction chamber such as those used for cats and rabbits).

Discussion on exposure to waste anesthetic gas in the workplace continues to be an interesting topic for publication:

A case report of personal exposures to isoflurane during animal anesthesia procedures. J Occup Environ Hyg. 2018 Feb;15(2):99-104. doi: 10.1080/15459624.2017.1388919

Isoflurane Anesthesia Has Long-term Consequences on Motor and Behavioral Development in Infant Rhesus Macaques. Coleman K1, Robertson ND, Dissen GA, Neuringer MD, Martin LD, Cuzon Carlson VC, Kroenke C, Fair D, Brambrink AM.
Anesthesiology. 2017 Jan;126(1):74-84.