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Veterinary technicians must be familiar with the human safety considerations involved in

veterinary anesthesia

Workplace Safety

Chapter 13

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Hazards of Waste Anesthetic Gas

Sources of waste inhalant anesthetic gas Exhaled by patient or escaped from anesthetic

machine during anesthetic period Inhaled when emptying or filling anesthetic

vaporizers Inhaled after an accidental anesthetic liquid spill

Measurement of waste anesthetic gas in parts per million (ppm)

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Hazards of Waste Anesthetic Gas (Cont’d)

Short-term effects of exposure to high levels of waste anesthetic gas Direct effect of anesthetic agent on brain neurons Resolve spontaneously when area is left Frequent occurrence indicates excessive waste

gas levels

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Long-term effects of exposure to high levels of waste anesthetic gas Serious health problems

Reproductive OncogenicHepatic RenalHematologic Neurologic

May be the result of toxic metabolites produced by the liver

Anesthetics eliminated through the lungs are less likely to produce long-term effects

Hazards of Waste Anesthetic Gas (Cont’d)

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Long-Term Effects of High Level Exposure to Waste Anesthetic Gas

Reproductive effects Risk of spontaneous abortion Infertility Congenital anomalies in children

Oncogenic effects None of the commonly used agents are

associated with an increased risk of developing cancer

Hepatic effects Hepatotoxicity

• Rare, most common with halothane exposure

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Long-Term Effects of High Level Exposure to Waste Anesthetic Gas (Cont’d)

Renal effects Possible renal toxicity with methoxyflurane

exposure Neurologic effects

Possible loss of motor skills and short-term memory

Possible increased incidence of neurological disease

Hematologic effects Possible bone marrow abnormalities

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Measuring Waste Gas Levels

Highest levels are in surgery suites, surgical prep rooms, and anesthesia recovery rooms

Highest levels during the anesthetic period are nearest the anesthetic machine

Factors that determine levels Duration of anesthesia Flow rate of carrier gas Anesthetic machine maintenance Effective scavenging system Anesthetic techniques used Room ventilation (15-20 air changes per hour is ideal) Anesthetic spills

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Reducing Exposure to Waste Anesthetic Gas

Use a scavenging system Collects waste gas from the anesthetic machine and

conducts it to a disposal site outside the building Installation and consistent use are most important factors Include exhaust from anesthetic machine, nonrebreathing

systems, ventilators, anesthetic chambers, and capnometers Active (high vacuum, low vacuum) or passive Active system with dedicated vacuum pump is most efficient Passive system is least expensive and is best used in rooms

with exterior walls

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Active and Passive Scavenging Systems

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Potential Difficulties with a Scavenging System

Prevent the negative (vacuum) pressure on the breathing circuit Reservoir bag will collapse Negative pressure relief valve will open

Obstructions may block waste gas from entering the scavenging system Anesthetic gas will accumulate in the anesthetic

circuit Excess pressure develops in circuit and patient’s

lungs Positive-pressure relief valve will open

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Alternative to Scavenging System

Activated charcoal cartridges Used in rooms not set up for scavenging Charcoal absorbs anesthetic vapors Replace cartridge every 12 hours or when weight

increases 50 g Don’t absorb nitrous oxide vapors Inefficient at flow rates >2 L/min

Masks with charcoal filters Worn by personnel at special risk Not effective for nitrous oxide Don’t use masks designed for particulate matter

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Reducing Exposure to Waste Anesthetic Gas

Check equipment for leaks Common sites for leaking equipment

Nitrous oxide connections not tightly secured Rings, washers, other seals joining tanks to machine hanger

yokes are missing, worn, or out of position Covering of unidirectional valve is not tightly closed Carbon dioxide absorber canister is not securely sealed Pop-off valve/scavenger connection is not airtight Holes in or loose connections for breathing hoses, reservoir

bag, or ET tubes Vaporizer cap missing

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Types of Leak Tests for Anesthetic Equipment

High-pressure tests Check for leaks between the gas tanks and the

flow meter Gas pressure ≥50 psi Only oxygen or nitrous oxide (the carrier gasses)

is released through any leaks

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Types of Leak Tests for Anesthetic Equipment (Cont’d)

Low-pressure tests Check for leaks in the anesthetic machine and

breathing circuit Gas pressure ≤15 psi Oxygen, nitrous oxide, and anesthetic gas

released through any leaks

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Reducing Exposure to Waste Anesthetic Gas

What type of leak test to perform High-pressure and low-pressure: both nitrous oxide and oxygen

carrier gasses Low-pressure test alone: oxygen carrier gas alone Low-pressure test: prior to machine use each day High-pressure test: nitrous oxide tank weekly or when tank is

changed Leaks may be found by locating a hiss of escaping air

or by using a detergent solution Don’t use machine with a leak until the source of the

leak has been identified and repaired

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Monitoring Waste Gas Levels

Important considerations Hospital employee becomes pregnant Odor of anesthetic gas is frequently detected Special concerns about waste gas levels

Professional monitoring Accredited industrial hygiene laboratory

In-house monitoring Detector tubes or badge dosimeters

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Safely Handling Compressed Gases

Fire safety Oxygen and nitrous oxide support combustion Static electricity can cause fire when oxygen and

combustibles are present Eliminate all sources of ignition or flames from any

room where cylinders are stored or used

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Safely Handling Compressed Gases (Cont’d)

Use and storage Cylinders are storehouses of large amounts of energy Wear impact-resistant goggles when connecting cylinders to

anesthetic machine Turn valve slowly and with proper wrench when turning on

the cylinder Chain or belt cylinders to wall Store in an upright position to prevent damage Store cylinders away from high traffic areas Don’t drag or roll a cylinder Keep full and empty cylinders separate Label with tear-off labels Use cylinders in the order they are received

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Labeling Compressed Air Cylinders

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Accidental Exposure to Injectable Agents

Opioids used for restraint and capture of wild animals Etorphine (Immobilon, M99) and carfentanil

(Wildnil) More potent than morphine Absorbed through mucous membranes or broken

skin Accidental exposure through accidental injection,

eye splash, or oral ingestion

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Accidental Exposure to Injectable Agents (Cont’d)

Precautions Become educated on potent opioids before using

them Don’t work alone and wear gloves when using

potent opioids Have reversal agents drawn up and ready for use Have a treatment plan in place Dispose of needles and syringes in a closed

container immediately

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Accidental Exposure to Injectable Agents (Cont’d)

Cyclohexamines (ketamine, tiletamine) Accidental eye splash may cause disorientation,

excitement, dizziness, or unconsciousness Alpha2-agonists

Xylazine, detomidine, medetomidine, dexmedetomidine

Accidental injection or skin contact may cause sedation, hypotension, bradycardia, respiratory depression, coma

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Accidental Exposure to Injectable Agents (Cont’d)

Precautions Personal protective equipment Carefully load syringes Properly dispose of needles and syringes First aid, including eye wash, readily available