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Personal breathing zone exposure monitoring for an anesthetic agent at a

research and development facility in India

Ankit Sharma, CIH, LFOH

International Safety Systems, Inc.

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Agenda

• Background • Anesthetic agent monitored • Methods used • Monitored locations / exposure groups • Processes • Results • Recommendations • Lessons Learnt

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Background

Anesthetic agents are administered to animals during surgeries in research and development procedures.

Anesthesia:

• analgesia (pain relief)

• amnesia (loss of memory)

• immobilization.

The drugs used to achieve anesthesia usually have varying effects in each of these areas.

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Background (contd.)

Inhalation Anesthesia

Advantages: • Superior to most injectable forms in safety and efficacy.

• Easy to adjust the anesthetic depth.

• Less potential for drug-induced toxicity.

Disadvantages: • The complexity and cost of the equipment.

• Potential hazards to personnel.

• Volatile liquids, should not be stored in animal rooms because the vapors are either flammable or toxic to inhale over extended periods of time.

Source: http://www.ahc.umn.edu/rar/anesthesia.html

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Background (contd.) Comparison of inhalant agents:

Important terminology: MAC: • % concentration of the drug needed to anesthetize 50% of animals. • Varies somewhat by species and by individual. • 1.2X MAC is an approximate vaporizer setting for maintenance of

anesthesia. Induction generally requires 2-3X MAC.

Response: • How rapidly concentrations in the blood change when the lung alveolar

concentration is changed. • Slow anesthetics have slow induction and recovery times. Source: http://www.ahc.umn.edu/rar/anesthesia.html

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Drug MAC Response Toxicity Comments

Ether 3.2 Slow Hepatoxicity Pre-medication with an anticholinergic may be necessary to reduce excessive respiratory secretions. Induction and recovery can be rough.

Methoxyflurane 0.2 Slow Nephrotoxicity (potentiated by tetracyclines)

This drug is not currently being manufactured. For a replacement, consider ether or diluted isoflurane.

Isoflurane 1.5 Fast None Respiratory depression, cardiovascular depression

Enflurane 2.5 Fast None Minimal respiratory depression, cardiovascular depression

Halothane 0.9 Moderate Nephrotoxic, mutagenic

Cardiopulmonary depression, risk of hyperthermia

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Anesthetic agent monitored

Isoflurane:

• HSE UK established Workplace Exposure Limit(WEL)-TWA: 50 ppm (used as guideline value)

• Halogenated hydrocarbon – mild ether-like odor

• Acute exposure: nausea, vomiting, headache, dizziness

• Chronic exposure: Tachycardia, respiratory depression, reproductive effects

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Methods

Sampling methods: • Monitoring device – active air sampling pumps for personal breathing

zone monitoring • Media - Anasorb 747 • Flowrate - 0.05 lpm • Duration - ~ 8 hours Analytical methods: • OSHA 103; Gas Chromatography/Flame Ionization Detector

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Monitored Locations / Exposure Groups

Full shift TWA personal breathing zone air samples were collected during surgery (PCO surgery lab) and investigation/ immunization (immunology laboratory) for support staff. Task based samples collected for surgeons / investigators and normalized into TWA exposures.

Surgery: • Surgeons • Support staff Investigation / Immunization: • Investigators / Surgeons • Support staff

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Surgery - Process Different surgeons performed different surgeries, common support staff assisting different surgeons throughout the shift. • Rats kept in induction chamber prior to surgery. • Induction chamber supplied with < 5 % isoflurane in oxygen at

approximate flowrate of 3 liters per minute (lpm) through a manifold with pressure regulated supply system.

• After desired sedation / induction, rats were lifted from and placed on surgery bench.

Scavenging: Spot extractor available over the induction chamber. Waste anesthetic gases passed through an activated charcoal filter.

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Surgery was performed by surgeon.

• Pre-sedated rat/mice was supplied with continuous oxygen supply (with less than 5 % Isoflurane) through a ‘nose hose’ during surgery.

Engineering controls during surgery:

• Prototype LEV

Work Surface

Engineering controls validated by face velocity measurements.

Nose Hose

Rat/mice placed

between two

extraction arms

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Investigation - Process

• Similar process as compared to surgery. Major difference is that testing / investigation being performed on rats / mice were slightly different than surgery.

Differences in engineering controls between Investigation and Surgery

Investigation Surgery

Induction chamber was provided with a prototyped Local Exhaust Ventilation

Induction chamber was provided with spot extractors.

The waste gas discharge hose was terminated at the inlet of prototype LEV.

The waste gas discharge hose was terminated through activated charcoal filter.

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Results Process Exposure Group* Number of samples

collected** Results

Surgery Surgeons 5 < 10 % of guidance value

Support Staff 3 < 10 % guidance value

Investigation Investigators 2 < 10 % of guidance value

Support Staff 3 < 10 % of guidance value

** - The number of samples collected varied due to limited availability of activities for investigation process.

*- Full shift samples were collected for support staff , as they were potentially exposed to Isoflurane throughout the shift. Surgeons / Investigators were rotated between surgeries and hence task based samples were collected , which were normalized to TWA after ensuring that there was no potential for exposure to isoflurane before or after activity.

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Discretionary Recommendations:

• Review feasibility of clamping the flexible waste anesthetic gas hose near the suction arm of the prototyped LEV (in case site decides to stop use of activated charcoal canisters for discharging waste gases).

• Consider providing emergency power back-up for the prototype LEVs and spot extractors used for performing surgery.

(As observed in case of a power failure, the mixture (isoflurane and oxygen) supply had remained operational through the power cut to provide life support to rat, thus releasing isoflurane in breathing zone air of surgeon in temporary absence of prototype LEV)

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Lessons Learnt

• Engineering controls provided by the site were effective in reducing employee exposures below the HSE UK established WEL-TWA considered as guideline value.

• Considering variation in number of surgeries performed by surgeons, the employee exposures are still expected to be considerably below the exposure limit during higher work-load for surgeons / investigators than observed during the assessment.

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Thank You

Any questions?

Ankit Sharma, CIH, LFOH

ankit.sharma@issehs.com