What are the GHGs (greenhouse gases) used in anaesthetics in New Zealand?
New Zealand (NZ) uses two classes of inhaled anaesthetics: nitrous oxide (N2O) and halogenated agents. The most commonly used halogenated agents are Desflurane, Sevoflurane and Isoflurane used in hospitals (Ang et al., 2021). N2O is usually co-administered as a carrier, in a mixture with a halogenated gas (Sherman, J., & McGain, F., 2016), and is prohibited in veterinary services (Environmental Protection Authority [EPA], 2021a).
These volatile gases are considered GHGs as they absorb infrared radiation on emissions that would otherwise have left the earth’s lower atmosphere (Anderson et al., 2012; Australian and New Zealand College of Anaesthetists [ANZCA], 2019).
The sedative Propofol, an intravenous (IV) sedative, is used with intubation for intensive care adults and is a controversial but commonly used anaesthetic in paediatric intensive care units (Festa et al., 2002).
The most common IV anaesthetics used by veterinarians for induction are IV anaesthetics such as propofol, alfaxalone, ketamine, and to a lesser extent thiopentone, whereas isoflurane is the most commonly used maintenance volatile gas for both dogs and cats (Sano et al., 2017).
For dentists, according to a 2018 survey (Lee et al., 2018), 95% of 204 dentists used local anaesthetic: 24% IV, 23% N2O, and 20% oral sedatives. Articaine (77%), followed by mepivacaine (41%), and lidocaine (36%) were the preferred choice of anaesthetics (Lee et al., 2018).
Specific information for primary care is unavailable, however, primary healthcare organisations are funded by District Health Boards (DHBs) (Ministry of Health [MOH], 2021), but whether primary care data would be included in DHBs statistics would require verification.
A 2012 workforce study showed that 29% of anaesthetists work in public hospitals, 7% in private practice, and 65% in both sectors (ANZCA, 2012), whereas a 2017 survey showed that 45% worked in public hospitals, 21% in private practice, and 80% in a metropolitan area (McGain et al., 2019a).
A 2018 survey on dental anaesthetists from the Dental Council of NZ found that of 204 practitioners, 76% worked in partnership group practices, while 24% were sole practitioners, with 82% of patients treated in private practice (Lee et al., 2018).
With regard to preference of anaesthetic, the same 2017 survey by the Australian (AU) and NZ College of Anaesthetists (ANZCA) on their AU and NZ Fellows, indicated that of the 359 respondents of 1000 surveyed, 72% preferred to use sevoflurane, 16% prefer propofol, 12% desflurane, and 1% isoflurane. 66% additionally use N2O in 0-20% in a mixture with general anaesthesia (McGain et al., 2019a).
Another study on three NZ DHBs; namely Auckland District Health Board (ADHB), with 39 operating rooms, Counties Manukau District Health Board (CMDHB), with 24 operating rooms, and Waitemata District Health Board (WDHB), with 12 operating rooms, found that between 2015-2018, the average annual use of desflurane (240mL/bottle) was 31%, sevoflurane (250mL/bottle) was 66%, and isoflurane (250mL/bottle) was 3% (Ang et al., 2021).
According to Pharmac (2020a), the volume of funded anaesthetic gases recorded were 9,173 bottles of sevoflurane (2015/216), down to 7,077 bottles for 2019/20; 3,152 bottles of desflurane (2015/16) to 576 (2019/20), and 296 bottles of isoflurane (2015/16) down to 84 in 2019/2020.
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