Working Safely with Isoflurane - Guidelines

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1. Purpose and Objectives

This guideline outlines the hazards and safety considerations for using isoflurane

2. Definitions, Terms, Acronyms

DG - Dangerous Goods

Risk Control - Taking action to eliminate health and safety risks so far as is reasonably practicable, or if that is not possible, minimising the risks so far as is reasonably practicable.

RRD - Regulated restricted drug. One of the additional 2 sub-categories of S4 regulated drugs.

RDD - Restricted drugs of dependency. One of the additional 2 sub-categories of S4 regulated drugs.

SDS - Safety data sheet. A document containing information on the health, safety and environmental aspects of a material or chemical for the purposes of storing, using and disposing of the substance in a safe way.

SOP - Standard Operating Procedure

Scavenging – The prevention of a contaminate gas entering the breathing zone of workers through selective capture at the feed gas interface with the animal. The captured contaminate can then be exhausted from the room, or cleaned and return to the work area.

TWA - Time Weighted Average

WES - Workplace Exposure Standard

WHSC - Work Health and Safety Coordinator/Manager

WHSQ - Workplace Health and Safety Queensland

Workers - all UQ Staff and HDR Students, including academics, lecturers, tutors, researchers, sabbatical/visiting staff, casual staff, vacation scholars, volunteers and students on work experience (as interpreted from the Work Health and Safety Act 2011).

3. Guidelines Scope/Coverage

This guideline is for all workers at The University of Queensland (UQ) who handle and use isoflurane.

4. Guidelines Statement

Isoflurane is a highly volatile, fluorinated organic liquid used for the anaesthesia of animals. It is usually delivered by means of a precision vapouriser, but may be administered by means of simpler apparatus for short term anaesthesia.

5. Risk Management

The quantity of isoflurane gas escaping into the workers breathing zone will depend on the type of equipment being used and the size of the animal being anaesthetised. An anaesthetised large animal such as a sheep or pig will exhale a significant amount of waste isoflurane, which, if incompletely scavenged, may lead to the accumulation of isoflurane gas within the room. In the case of a rodent, airborne isoflurane is likely to be from direct leakage from a poorly sealed nose cone.

Other factors influencing worker exposure to isoflurane is the suitability of the animal to be intubated (minimising direct leakage), the physiology of the animal, e.g. dogs are easier to intubate than cats of similar size, and the skill of the worker performing the anaesthetic procedure, e.g. veterinary students will be exposed to higher isoflurane levels intubating a cat than an experience animal anaesthetist.

The variations in the source of contaminate isoflurane, the type of animal being anaesthetised and the level of worker experience must be taken into account when assessing the risk from isoflurane.

Other incidental exposures to isoflurane may also occur, e.g. lab workers filling vapourisers and technicians calibrating or trouble shooting issues with precision vapourisers.

Health effects from short-term, elevated exposure of isoflurane vapour include narcosis with symptoms of drowsiness, dizziness and unconscious. Light to moderate exposures to airborne vapour may result in headache and irritation of respiratory tract in some workers. Isoflurane will cause severe eye irritation if splashed directly into the eyes.

The health effects of long term isoflurane exposure are unknown and published data on isoflurane and related risks to humans is limited. Animal studies indicate possible chronic effects from halogenated anaesthetic vapour include liver and kidney disease, and elevated rates of some forms of cancer. The existing animal data comes from studies with methoxyflurane and halothane both of which, based on their lipophilic properties have oil-gas solubility much greater than isoflurane, increasing systemic health effects.

There is currently no specific workplace exposure standard (WES) for isoflurane however, there is a WES for enflurane (an isomer of isoflurane), which is also a halogenated ether used as an inhalation anaesthetic. The WES for enflurane is set at 0.5 ppm time weighted average (TWA) over an 8 hour day, by Work Safe Australia, based on what should be achievable if good control measures are in place. Other exposure standards in place internationally are: 2, 10 or 50 ppm. The 2 ppm TWA is based on lowest level that can be reliably measured with a direct reading instrument.

A TWA standard 10 ppm comes closest to a conservative, realistic health based standard. Note: the level of isoflurane to produce central nervous system effects is 12,000 ppm and that blood levels of isoflurane fall to zero within a few breaths of discontinued exposure.

5.1 Risk control

5.1.1 As Low as Reasonably Achievable (ALARA) exposure goal

A systematic evaluation of worker exposure to isoflurane during animal anaesthesia was undertaken at six UQ research facilities in 2014. The TWA-8hr exposures ranged from below less than 0.01 ppm (limit of detection) to 1.76 ppm. Direct reading results taken within the breathing zone of workers ranged from 0.1 to 66.9 ppm. From this study it was concluded that the risk of adverse health effects from Isoflurane exposure is low, but due to the lack of comprehensive research on health effects and the contradictory information in the scientific literature, it would be prudent to reduce levels of worker exposure to ALARA. This can be achieved through the control measures detailed below.

5.1.2 Olfactory threshold and exposure level

The reliable odour threshold for airborne isoflurane is about 50 ppm. Therefore, odour is not a reliable indicator for determining airborne levels above the TWA-8hr exposure standard. Likewise, a transitory, low intensity odour does not indicate a risk of acute effects such as narcosis, but continuing levels above the odour threshold are indicative of poor ventilation controls.

5.1.3 Ventilation

  • Procedure done in a chemical fume hood. This is impractical for large animals or where highly controlled anaesthesia is required, as a precision vapouriser will not fit in a fume cabinet.
  • Procedure performed on a down draft table. Down-draft tables provide the most effective LEV extraction, but are expensive as well as impractical for small animals.
  • Procedure done using active scavenging, i.e. portable exhaust extraction built into the nose cone of the anaesthetic delivery system on the animal. Extracted air can either removed from the room or cleaned using charcoal filters and returned.
  • Passive scavenging where a combination of exhalation effort of the animal and positive pressure from the delivery of anaesthetic gas drives the air through an activated charcoal canister.

For most laboratory situations active scavenging will be employed, and in combination with good general dilution ventilation, a high level of protection from contaminate gas will be provided to workers.

It is important that the scavenging system be part of the regular maintenance and calibration of the anaesthetic equipment. A visual check of the flow-monitoring indicator of the scavenging system and the connections of the associated tubing should be made before equipment use. In the case of passive scavenging equipment a log of usage should be kept to ensure the charcoal filter is replaced regularly, or changed periodically independent of usage.

5.1.4 Optimising equipment

Equipment should be optimised to minimise isoflurane leakage into the air, and steps to be taken include:

  • Researching available rodent nose cones to ensure the best devices are being used, and determining which nose cone gives best seal in different scenarios.
  • Ensuring that only purpose built induction boxes are used. Avoid the use of modified lunch-box type plastic containers.
  • Ensuring that components of anaesthetic circuits are specifically designed for animal anaesthesia, especially connecting tubing and nose cone equipment. Laboratory improvised equipment is likely to leak and expose workers to isoflurane, as well as compromise the anaesthesia of the animal.
  • Ensuring keyed fillers with good seals are used when filling anaesthetic vapourisers.

5.1.5 Isoflurane exposure and pregnancy

All staff working with anaesthetic agents and contemplating pregnancy should be advised that it is sensible to limit exposure to toxic substances to the lowest level achievable. They should be given information about the measures that have been taken to ensure safety, and those contemplating pregnancy can continue working in areas using anaesthetics, where proper precautions are in place. Anyone who has concerns relating to pregnancy should contact the Occupational Health Nurse Adviser, OHS Division.

5.2 Storage requirements

Isoflurane is classified Schedule 4 under the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP), but it is not included in either RRD or RDD S4 sub categories where additional acquisition, storage and usage requirements apply.

To comply with S4 requirements isoflurane must not be accessible to the general public. Laboratory areas with swipe card access, or secured by locking are compliant. For more open labs without controlled access a locked cupboard/drawer/fridge must be used.

Further details of UQ requirements scheduled drugs and poisons usage can be found at PPL 2.70.13 Drugs and Poisons Policy and Guideline.

Isoflurane is non-flammable and is not classified as dangerous goods. It is most often supplied in 500 ml bottles that minimise its acute narcotic effects should a loss of containment incident occur, provided the risk control measures outlined in section 5.1 are followed.

5.3 Training and competency

As a minimum, all personnel working at the University are required to complete the following mandatory online safety training via Learn.UQ:

  • General Workplace Safety Training
  • Annual Fire Safety Training.

In addition, staff and students working in laboratories with chemicals are required to complete additional online training modules for laboratory and chemical safety, also via Learn.UQ:

  • Laboratory Safety Induction
  • Chemical Safety Training.

Supervisors are also responsible for ensuring sufficient resources to implement control measures, where appropriate are provided. Supervisors should also:

  • Implement an educational program to ensure that all persons using isoflurane are aware of the health and safety hazards.
  • Ensure workers receive suitable on the job, task specific training along with adequate supervision, which is part of the assessment of competency, before working unsupervised.

Refer to UQ Training Needs Analysis website for additional information.

5.4 Emergency procedures

5.4.1 Spills

The primary acute hazard of a spill of isoflurane is narcosis and unconsciousness. The quantities for minor and major spills are for guidance only, and risk management strategies should occur in context of a well-ventilated laboratory area. The action plan for minor and major spills must be detailed in the risk assessment, prior to commencing work.

Minor spill (less than 500 ml)

  • Increase ventilation within the room and consider temporary evacuation of the immediate area while vapours disperse.
  • Use protective gloves to avoid skin contact and clean up any remaining liquid using an absorptive material.
  • Dispose of absorptive material as waste through UQ Chemwaste.

Major spill (more than 500ml)

5.4.2 First Aid

  • Small quantities of isoflurane on skin or clothing will evaporate rapidly, but remove excessive isoflurane from the affected area by flushing with water using a laboratory safety shower or eye wash facility. Remove the worker affected by isoflurane vapour to an area with fresh, uncontaminated air.
  • Move the person exposed to the recovery position if unconsciousness and monitor signs and symptoms. Contact your local First Aid Officer and the UQ Health Service for advice on further treatment.

6. Obligations and Responsibilities

6.1 Supervisors

  • Ensure that risks are eliminated or minimized as far as reasonably practicable.
  • Provide supervision and training in the safe use of these materials.
  • Provide assistance with the risk assessment process and to ensure the assessment is comprehensive and accurate.
  • Review and approve the risk assessment, and ensure all controls outlined in the assessment are followed by workers.
  • Ensure that all appropriate safety systems and equipment are in place, fully operational and used correctly.
  • Ensure that all incidents involving these materials are investigated as soon as possible and that corrective actions (including review and modification of risk assessment and SOPs) are implemented to prevent recurrences.

6.2  Workers and students

  • Ensure that risks are eliminated or minimised as far as reasonably practicable.
  • Provide assistance with the risk assessment process to ensure the assessment is comprehensive and accurate.
  • Follow safe operating procedures using the controls outlined in the risk assessment.
  • Wear all PPE required and ensure it is maintained in good condition.
  • Immediately stop work and notify supervisor if there are any changes to procedures or deficiencies in the work process or risk assessment.

7. Contact for Additional Information

Occupational Hygiene Adviser
Occupational Health Nurse Adviser

UQ OHS Division
Phone: 336-52365

Director, Health, Safety and Wellness Mr Jim Carmichael
Director, Health, Safety and Wellness Mr Jim Carmichael