1. 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

2. 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

3. 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

4. Inflation of cuff Place largest tube possible Close pop off
Squeeze reservoir bag
Inflate cuff while listening for air leakage around tube in larynx

5. 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

6. 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.

7. 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

8. 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

9. 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 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)

10. 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 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

11. 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.

12. 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.

13. 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.

14. 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

15. 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

16. 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.

17. 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.

18. 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 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.

19. 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.

20. 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.

21. 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.

22. 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 cm. H20 when bagging patient.

23. 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.

24. Anesthetic Breathing Systems
Pages 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.

25. 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.

26. 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.

27. 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.

28. Non-rebreathing System
Can convert a partial re-breathing system to non-rebreathing by simply increasing the flow rate up to ml/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.

29. 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

30. 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.

31. 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.

32. 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.

33. 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.

34. 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

35. 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

36. 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.

37. 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.

38. 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

39. 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.

40. Flow rates during induction
Maintenance flow rates
non-rebreathing ml/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 ml/kg/min
minimal rebreathing- flow of ml/kg/min

41. 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.

42. 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

43. 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

44. 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.

45. 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.

46. Hazards of Anesthetic Gas
Pages 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.

47. 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

48. 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.

49. 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.

50. 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.

51. 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.

52. 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.

53. 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.

54. 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

55. 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.

56. Neurological Effects
N20 has been shown to increase neurological disease x the population norms.
Muscle weakness, tingling sensations, and numbness.
Probable decline in motor skills and short-term memory.

57. 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.

58. 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.

59. Leak Tests High pressure test for 02 and N20 Low pressure test
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.

60. 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.

61. 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.

62. 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.

63. 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

64. 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

65. 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

66. 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.

67. Monitoring Waste gas levels
Can be done by an occupational Health tech. Cost $.
Can get detector tubes and badges cost 50$ per badge (includes analysis)

68. 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

69. Anesthetic monitoring devices
Pulse oximeter
Doppler
Silogic cardiac and respiratory monitor
Temperature probes
Oscilloscopes
Esophageal stethoscope
Audio patient monitor
Beeper
Dinamap

70. 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.

71. 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

72. 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

73. Beeper Cheaper version of the silogic respiratory monitor.
Sensitivity is adjustable
Beeps with every respiration
Apnea alarm

74. 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

75. 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.

76. 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.