Endotracheal tubes

Made of either rubber, vinyl plastic, or silicone plastic rubber tubes (red color)

dry and crack over time with exposure to disinfectant can kink or collapse(some have metal insert)

vinyl plastic (transparent) don’t crack but become stiff with age

Silicone Rubber are best but most expensive. Resistant to cracking and are smooth and flexible Most expensive

Endotracheal Tubes

2 different types used commonly Murphy and Magill Murphy has eye near end and Magill

doesn’t eye prevents plugging end with mucous and

tracheal wall

sized by internal diameter, French, or Magill scale. Internal diameter is best

can be supplied with or without cuff

Endotracheal Tubes

Sizes ID of 2mm to 11mm most common sizes use in vet med. Written on outside of tube

Cuffs advantages

prevent leakage of waste gas reduce risk of aspiration prevent patient breathing room air

disadvantages Excessive pressure on larynx may result in irritation or

necrosis of larynx make extubation more difficult- it is not smooth

Inflation of cuff

Place largest tube possible Close pop off Squeeze reservoir bag Inflate cuff while listening for air

leakage around tube in larynx

Anesthetic machines and components

Include compressed gas tanks (02 and N02) Flow meter vaporizer fresh gas delivery circuit 02 flush valve Pop off valve C02 canister pressure manometer negative-pressure relief valve

Anesthetic Machine

Designed to deliver volatile gas anesthetic to and from a patient by means of a circuit of tubing in combination with 02 or 02+N02.

Important functions deliver 02 at a precise controlled rate vaporize anesthetic precisely and mix it with

delivery gas moves exhaled gas away from patient and

dispose of or recirculate it after removingC02.

Anesthetic Machine Also used to deliver 02 to critically ill patient.

(when vaporizer is turned off) Put mask on patient and hook it to hoses.

Components (pages 172 & 173) Gas cylinders

provide 02 at 100% concentration (room air is ~20%) anesthetic patient has higher 02 requirement anesthetic patient has reduced tidal volume 100% 02 decreases anesthetic induced hypoxia

provides carrier for volatile anesthetic

Anesthetic Machines O2 obtained as a compressed gas in a cylinder. Can obtain in various sizes

E-size attaches directly to the machine G and H cylinders stand alone

Open valve “lefty loosie, righty tighty” Be very careful if N02 is also used. It is also sent through

the same system. If oxygen runs out the Nitrous will carry the anesthetic and patient will die of hypoxia

Attached to machine by yoke and flexible gas line designed so wrong gas cannot be attached to the

anesthetic machine. 02 is white or white/green N02 is blue

Anesthetic Machines Volume of E tank is PSI x 0.3= volume in liters

full E tank has~ 660L of 02

linear relationship between volume and pressure. should change tank when ~ 10% left or about 200-250 psi at the

very latest. N02 behaves differently as a gas.

It is liquid and gas in tank pressure remains high until liquid is gone and then it disappears

quickly. Should evaluate amounts by weight not pressure. Change

when pressure less than 500 lb. Both N02 and 02 are run through a pressure reduction valve before

entering anesthetic machine. Will take 2200 psi down to 50 psi ( the pressure that is acceptable for the anesthetic machine)

Anesthetic Machine

Flow meter allows the anesthetist to set gas flow rate very

precisely. Separate meters for 02 an N02

Gas enters bottom of meter and exits from top. Measure flow at top of rotor and center of ball. Never exceed 3:1 N02:02 ratio Flow rate of 120-200 ml/kg/min with a minimum

of 1 liter per minute for non-rebreathe 15 ml/kg/min for full rebreathe Median for partial rebreathe

Anesthetic Machine Vaporizer

air from flow meter goes directly to vaporizer. functions to vaporize anesthetic and mix it in

controlled amounts with 02 will not deliver any anesthetic if there is no flow of

gas It is outside the anesthetic circle circuit.

Anesthetic Machine

Fresh Gas Inlet after gas leaves vaporizer it enters a low

pressure hose in a one way circular pattern.

02 and anesthetic is call ”fresh gas”. Circular Pattern is called anesthetic

circuit.

Anesthetic Machine

Reservoir bag or rebreathing bag first destination of fresh gas bag gradually fills with fresh gas and is emptied

when the patient inhales. The bag continually inflates and deflates in time

with the patients respiration. Bags should be minimum of 60ml/kg patient sizes from 500ml to 30L depending on the size

of the patient.

Anesthetic Machine

Functions of anesthetic re-breathing bag easier for patient to breathe-decreases resistance enables anesthetist to monitor breathing

both depth and rate

useful check on endotracheal tube function can bag animal to deliver more 02

prevents hypoxia and hypercapnea prevents atelectasis can be lifesaving during an arrest

Anesthetic Machine Rebreathing Bag

cautions do not over inflate. Can hinder breathing if under inflated it will not serve any useful

purpose. Close pop off valve and squeeze bag to a

minimum pressure of 15 inches of water to breathe for animal. After bagging open pop off.

Anesthetized patients tend to breathe shallowly, bagging allows full inflation of lungs and keeps oxygen levels up even when patient is not breathing

Anesthetic Machine Inhalation flutter valve

unidirectional valve allowing gas only in one direction, towards patient.

As patient inhales the valve opens allowing fresh gas to the anesthetic hose in one direction of flow.

Anesthetic Machine

Inhalation hose Y piece adapter- joins inhalation hose

with exhalation hose. Exhalation hose Exhalation flutter valve- prevents

exhaled gases from passing back to patient. It helps direct exhaled gas to the CO2 absorber canister.

Anesthetic Machine

Oxygen flush valve. Allows 02 to bypass the flow meter and vaporizer

and enter the circuit, often at the C02 absorber. (only in rebreathe mode)

Delivers pure 02 at a rate of 30-50 L/min. Useful to:

deliver 02 to a critical patient rapidly fill a depleted reservoir bag dilute the residual anesthetic being exhaled after

machine is turned off at the vaporizer We do not use in Bain system because it will

damage the patients lungs easily.

Anesthetic Machine

Pop off valve is a pressure relief valve. Can be kept fully or

partially open or closed. Usually kept open except when bagging patient or

when very low flow rates of 02 are used. Uses:

waste gases exit at this valve and enter scavenger prevents excessive pressure from accumulating in

circuit. Allows bagging of animal. Be careful not to rupture

alveoli.

Anesthetic Machine

C02 Absorber any gas that does not exit at the pop-off

valve is directed to a canister containing soda-lime or barium hydroxide lime.

Absorbing ingredient is calcium hydroxide. Ca(OH)2.

2C02+Ca(OH)2+2NaOH>Na2CO3+CaCo3+ 2H20+heat

Granules do not last indefinitely and must be changed when depleted.

Anesthetic Machine

C02 Absorber- baralyme Reacts with C02 to produce water, heat and sodium

and calcium carbonate. signs baralyme needs to be replaced.

Functional granules crumble easily while depleted granules become hard and brittle.

Color of granules. They contain a pH indicator that causes the granules to change color when saturated with C02. Change when 1/2 has changed color Color reaction is time limited and the color may revert over time

even though the granules are still saturated with C02.

Anesthetic Machine

Pressure Manometer on top of C02 canister and it indicates pressure

being generated in the circuit and therefore in the animals lungs.

Pressures over 15cm H20 indicate the 02 flow is too fast or the pop off is closed too much.

Is a useful gauge when bagging animal because it prevents the anesthetist from over or under-inflating lungs. Maintain pressure of 15-20 cm. H20 when bagging patient.

Anesthetic Machine

Negative Pressure Relief Valve designed to allow entry of room air if a

negative pressure is detected in the circuit. Most commonly seen in systems with active scavenger apparatus.

Can be a safety to prevent hypoxia in systems that run out of bottled 02.

Anesthetic Breathing Systems

Pages 195-207 in text 3 types in common use

closed (total rebreathing) semi closed (partial rebreathing) Open (non-rebreathing) rebreathing implies re-circulation of exhaled

gases from patient into the fresh gas circuit. It is also called a circle system.

Closed and semi-closed systems have different 02 flow rates and different closure of the pop-off valve.

Total Re-breathing System For patient over 7 kg.

Uses less 02 and anesthetic and is therefore more economical to use.

Has some serious safety concerns C02 accumulation can be a problem if the C02

absorber is not maintained properly. Increased pressure in system is easily able to get out

of hand and become dangerous. 02 depletion and N20 accumulation occurs over time. Leaks can increase danger markedly. Must monitor the rebreathing bag closely may not accurately deliver the proper % of anesthetic

from some vaporizers if flow rate is inadequate.

Partial Re-breathing System

Like full rebreathing system except 02 flow is greater and the pop off valve is left open to a greater extent.

Much safer than a full rebreathe system.

Non-Re-breathing System

Little or no exhaled gas is returned to the patient. Evacuated by a scavenger.

Do not need C02 canister, flutter valves, and the pressure manometer.

Most anesthetic machines are designed as rebreathe but are converted by the attachment of a Bain system or other similar non-rebreathe system.

Non-rebreathing System

Can convert a partial re-breathing system to non-rebreathing by simply increasing the flow rate up to 200-300ml/kg/min of 02.

Bain system is the most commonly used of the systems. Consists of an inner inspiration hose and a

larger corrugated outer expiration hose. Allows slight warming of inspired gases by

expired gases.

Bain System

Gas from outer, exhalation tube enters a reservoir bag then proceeds to pop off valve and a scavenger system.

At low flow rates there is some rebreathing of exhaled gas and can lead to hypercapnea because there is no C02 absorber available.

Pop off is before reservoir bag on exhalation side of circuit

Rebreathing vrs. Non-rebreathing

Base on the following factors: Size

use Bain if patient less than 10Kg. There is less resistance to respiration when the flutter valves are absent, and there is no C02 canister in the system.

It is felt small patients have greater difficulty inhaling against a rebreathe system although the size of the endotracheal tube is much more significant source of resistance to air flow.

Rebreathing vrs. Non-rebreathing

Convenience Bain is smaller and less cumbersome with a small

patient. Cost

rebreathe systems use less 02 and anesthetic than non rebreathe systems in the same size of animal.

Control can change depth of anesthetic more quickly in a

non-rebreathe system. Conservation of heat and moisture is greater in a

rebreathe system.

Rebreathe vrs. Non-rebreathe

Inspired fresh gas in a non rebreathe system is 0% humidity and 16 C, while exhaled gas is 25 C and near 100% humidity.

Total rebreathe systems produce the least amount of waste gas of all systems.

Vaporizers

The most expensive and complicated part of the anesthetic machine.

All vaporizers convert liquid anesthetic to gas and mix it with a carrier gas.

Can be precision or non-precision If you get the wrong anesthetic in a

precision vaporizer you must have it serviced by a medical tech before using it again. They will have to change filters and recalibrate it.

Precision Vaporizer

Has: temperature compensation flow compensation back pressure compensation high maintenance requirements high relative cost used for isoflurane, halothane concentration of gas given as % positioned out of the anesthetic circuit.

View amount of gas in window on side of vaporizer Also indicates whether the anesthetic is contaminated by

color. Should be serviced on a yearly basis

Non-precision vaporizer

Used for less volatile gas anesthetics Almost out of date like ether Output

is affected by temperature is affected by flow rate is affected by back pressure

has minimal maintenance is low cost is used for methoxyflurane (only used at U of A) non-precision control positioned in the anesthetic circle

Non precision vaporizers More anesthetic is delivered at higher temperatures more anesthetic is delivered at high flow rates more anesthetic is delivered when there is higher

pressure in the system. This occurs with respirators and bagging. You must therefore turn down the anesthetic when assisting the breathing of a patient.

It is harder to monitor a patient especially in the initial stage of anesthesia.

Hard to use this type with non-rebreathing anesthetic delivery systems.

VOC versus VIC

Vaporizer out/in circuit all precision vaporizers are out of circuit

because it offers too much resistance to the flow of gas.

Non precision vaporizers offer little resistance to flow and do not impede breathing and are therefore kept in the anesthetic circuit.

Carrier Gas Flow Rates If N20 is used, its flow rate should be 1.5 to 2

times the 02 flow rate. Customary to use higher flow rates during

induction and then reduced when the desired plane of anesthesia is achieved.

Mask induction- use 30 times the tidal volume ie. 30 x 10 ml/kg/min = 300 ml/kg/min. <10kg use 1-3 L/min >10kg use 3-5 L/min chamber induction 5 L/minute

Flow rates during induction For animals induced with injectable and then

connected to an anesthetic machine: minimum flow rate initially is respiratory

minute volume which is tidal volume(10ml/kg/min)x respiratory rate. 200ml/kg/min is commonly used.

Flow rates during induction Maintenance flow rates

non-rebreathing 130-200ml/kg/min rebreathing 15 ml/kg/min if it is a closed

circuit but you must have a minimum flow rate of 1000 ml/min

partial rebreathing- flow of 25-50 ml/kg/minminimal rebreathing- flow of

150-200ml/kg/min

Flow rate at end of anesthesia

Increase flow rate immediately after turning off the vaporizer. This dilutes and flushes out the

anesthetic and results in a quicker recovery.

Also helps to use the 02 flush and empty the reservoir bag with the pop off fully opened.

Set up of Anesthetic Machine

Assemble all needed supplies inflate endotracheal cuff check laryngoscope bulb and battery draw up induction agent set up IV fluids and catheters and tape Check vaporizer for quantity of

anesthetic

Set up of Anesthetic Machine

Check Oxygen tank for volume available check flow meter and anesthetic dials for

smoothness of function. Assemble the appropriate circuit attach reservoir bag that is proper size check C02 canister Test machine for leaks

Maintenance of Anesthetic Equipment

Keep 02 off when machine not in use and flush and release pressure in system.

Turn flow meter to off when finished Service precision vaporizer yearly Check baralyme after each procedure and change

when more than 50 % is blue. This is a hazardous chemical and you should wear

gloves and a mask. Remove flutter valves and clean with soap and

water weekly.

Maintenance of Anesthetic Equipment

Remove and clean flutter valves periodically

Remove and clean hoses after each anesthetic procedure.

Clean and dry endotracheal tubes, masks, and other tools after each usage.

Do not use cleaning agents which are damaging to respiratory epithelium like ethylene oxide or formaldehyde.

Hazards of Anesthetic Gas

Pages 217-237 of text Refers to nitrous oxide, halothane,

isoflurane, or methoxyflurane that escapes from system or patient and affects the personnel working with the patient in the environment and what happens when they are chronically exposed to this waste gas.

Can also refer to short term, high exposures when the gas is accidentally spilled in OR.

Active anesthetic gas scavenging

Removes used gas under vacuum to minimize the residual gas in the environment affecting the or personnel

If there is no negative pressure relief valve we keep the oxygen flow rate high enough to prevent hypoxia in the patient

High pressure leak test

Soap and water on the valves on the tanks

Look for bubbles Should be performed every time a tank

is changed.

Low pressure leak test

Set up system Close pop off Place obstruction at patient end Squeeze reservoir bag and listen for

air leaking Should be done every time machine is

set up.

Short term problems of anesthetic exposure

Result as a direct effect of the anesthetic on the brain. Includes fatigue, headache, drowsiness,

nausea, depression, and irritability. Usually abate when the individual is

removed from the source of the gas. Frequent recurrence of these symptoms

may be an indication of xs waste gases and the possibility of long term problems.

Long term effects

Serious health problems can occur including: reproductive disorders, liver and kidney problems, chronic nervous system dysfunction.

Isoflurane is the least toxic and halothane is the most toxic. This is due to the amount of metabolism of the gas in the body of the recipient.

Effects on reproduction This is probably the most serious effect.

Risk of spontaneous abortion is 1.3-2x avg. Increased rate of infertility. Increased rate of congenital abnormalities. N20 most responsible.

It has the highest correlation to abortion and congenital abnormalities of any of the anesthetic gases. Halothane is the next most implicated.

Cancer induction

It is generally believed that none of the commonly used anesthetic agents used in veterinary hospitals is carcinogenic at the levels commonly measured in the OR’s.

Hepatic Effects

Halothane is particularly hepatotoxic. Metabolism in some individuals produces

toxic metabolites which causes halothane hepatitis.

Rate of hepatitis is 1.5 x that of general population.

Rare induction of malignant hyperthermia

Renal Effects

Methoxyflurane has renal toxicity in anesthetized patients.

Increase of 1.2 to 1.7 x the rate of the general population.

Hard to say whether this is affected by other related occupational hazards.

Neurological Effects

N20 has been shown to increase neurological disease 1.7 - 2.4 x the population norms.

Muscle weakness, tingling sensations, and numbness.

Probable decline in motor skills and short-term memory.

Assessment of Risk

Difficult to do, yet the average AHT is not necessarily at high risk. Studies are contradictory and sometimes poorly

executed. The work place is complicated and anesthesia is

only one component of risk. Most studies have not evaluated the effects of

scavengers and ventilation. Safe levels of anesthetic waste gases have not

been established.

Reduction of exposure

Use scavenging system is the single most important step to reduce waste gas pollution. Reduces measured waste gases from 64-94% in

OR Check system for leaks. Sites include:

connection for N20 lines O rings, washers, and other seals. Valves, C02

canisters, reservoir bags, hoses, pop off valves, endotracheal tube cuffs.

Leak Tests

High pressure test for 02 and N20 put a detergent solution on all tank joints

and connections when turned on and check for bubbles.

Low pressure test Secure all connections an place a hand

over the Y piece. Fill the system until the rebreathe bag is full and the system can maintain 30 cm H20 for 30 seconds.

Anesthetic techniques to reduce waste gas

Faulty work practices results in 95-99% of all the released waste gas.

Avoid masking and using anesthetic chambers.

Used functional cuffed endotracheal tubes when possible.

Use closed rebreathing systems when possible.

Anesthetic techniques to reduce waste gas

Do not turn on anesthetic until patient connected to hose.

Do not disconnect patient during procedure unnecessarily. Always turn vaporizer to 0 when disconnecting patient.

Evacuate the rebreathe bag into the scavenger.

Keep animal connected to scavenger with pure 02 for several minutes after the procedure to flush gas from animals system.

Anesthetic techniques to reduce waste gas

Make sure anesthesia room is well ventilated (15 air changes/hr)

Service anesthetic machines annually. Inspect equipment frequently and replace

anything that leaks. Wash hoses frequently to get rid of xs gas

and bacterial contaminants. Do low pressure leak test every time you set

up machine.

Anesthetic techniques to reduce waste gas

Fill vaporizers in well ventilated area, wear gloves and wash hands after. Store filling devices in a plastic bag between uses.

Clean thoroughly after an anesthetic spill. Cap empty anesthetic bottles when

discarding. Wash rubber parts with mild detergent and

discard when the rubber is hard and cracking

Anesthetic techniques to reduce waste gas

Monitor the rebreathe bag. It should coordinate well with patient respirations.

Use lower gas flows, this leads to less environmental contamination.

Remember the recovery area will have high levels of gas blown of from patient. Have it well ventilated.

Washing removes waste gas from accessories.

Fill vaporizers with closed system

Anesthetic spills

Close room and ventilate Turn off central vac, it will spread throughout

the hospital Cover with kitty litter Wear protective clothing and gloves Wear cartridge mask Put litter in sealed container and remove

from building Change clothing afterwards Call fire department if you can’t handle it

Anesthetic chambers

Very high environmental contamination Patient absorbs gas into fur and it is released from

the chamber. Use with a scavenging system Should have a flow through system that can be

flushed with 0 2 after patient is down but before you remove it from the chamber.

Reclose chamber after removing the patient and continue to flush with air or oxygen to a scavanger.

Chamber should be well sealed Use only in a well ventilated room. Wash chamber after every use.

Monitoring Waste gas levels

Can be done by an occupational Health tech. Cost 250-700$.

Can get detector tubes and badges cost 50$ per badge (includes analysis)

Compressed gas cylinders

No open flames Do not knock over. It becomes a torpedo.

(Watch: “Gone in 60 Seconds”) Do not stop leaks with hands (hamburger). Chain cylinders to the wall. Use in the order they were received. Keep valve caps on until they are attached

to the machine. Open with proper tools Store in safe area with little traffic

Anesthetic monitoring devices

Pulse oximeter Doppler Silogic cardiac and respiratory monitor Temperature probes Oscilloscopes Esophageal stethoscope Audio patient monitor Beeper Dinamap

Esophageal stethoscope

Inexpensive and easy to use Only used with patient with an endotracheal

tube Not useful in oral and cervical surgery. Lubricate tube and pass down esophagus

while listening to stethoscope. Stop when heart is loudest. Can hear respiration as well.

Don’t have to reach under drape with this.

Audio patient monitor

Audible beep with heart beat and respiration.

Will amplify other movements Noise is distracting to some

I find it comforting We may listen to the noise and stop

monitoring patient Attached to esophageal tube

Silogic

Monitors EKG, respiration, Respiratory monitor is attached to the

endotracheal tube. Can set levels at which an alarm will

sound. Very sensitive and can be broken easily

Heart monitor is a six lead EKG setup

Beeper

Cheaper version of the silogic respiratory monitor.

Sensitivity is adjustable Beeps with every respiration Apnea alarm

Dinamap

Uses a blood pressure cuff placed on a front leg, back leg, or tail. Cuff must be placed with arrow over

artery to work Shivering interferes with measurement

Measures BP several times and reports an average

Doppler

Senses turbulent blood flow Can use with a cuff and a manometer

to monitor BP Can use to monitor heart Crude measure of BP just with the

volume of the sound.

Pulse oximeter

Measures arterial oxygen saturation Probe can be placed on tongue, ear, foot or

with rectal probe Also gives heart rate. Has alarms for high and low levels which

can be changed for various patient types. Perfusion indicator gives an indication of

how accurate the reading is.