T5: Induction

Question 1

To induce anaesthesia means to:

Answer 1

induce unconsciousness

Question 2

Anaesthesia may be induced and maintained by either ….. or ….. agents

Answer 2

injectable or inhalational agents

Question 3

Common induction drugs:
Propofol

Answer 3

• usually given by a bolus and causes rapid induction which allows a short period to intubate.
• Transient apnoea may occur so respiration must be monitored during induction and intubation should occur in a short period to maintain airway.

Question 4

Common induction drugs:
Thiopentone

Answer 4

• distributed through the body fat
• must be given IV
• should not be given in animals exhibiting shock, anaemia, hepatic or renal damage.

Question 5

Common induction drugs:

Alfaxalone

Answer 5

• steroid anaesthetic that can be given IV in dogs and cats & deep IM in cats.
• must be given as a slow IV injection, to effect, never as a bolus.
• Alfaxan is also suitable for TIVA (total IV venous anaesthesia)
• Recovery is usually within 60- 80 minutes.

Question 6

Explain the process of intubation

Answer 6

1. select correct ET tube, apply lube
2. use a long peice of bandage or drip tubing placed under the front teeth, support the upper arcade of the animals jaw. Ensure the neck is extended while straight to allow good visualisation
3. Felines must now have topical local anaesthetic sprayed on the larynx to prevent laryngeal spasms
4. Gently pull tongue out and down, enure that the blade of the laryngoscope does not touch the epiglottis, but just sits on the base of the tongue in front of the larynx.
5. Insert the ET tube gently past the vocal folds into trachea.
6. Check proper placement by checking for patients breath as it exits the ET tube during exhalation
7. Once correct, tube should be tied in place. Cuff should be inflated gently and the patient placed on the oxygen. Carefully listen for any leaks around the tube

Question 7

Should you disconnect the ET tube when moving a patients postition?

Answer 7

YES!!!

Question 8

Is Isoflurane always delivered with oxygen?

Answer 8

YES

Question 9

Reflexes to check for level of anaesthesia?

Answer 9

• Palpebral reflex (blinking)
• Pupillary light reflex -pupils constrict to light
• Nystagmus -eye flicking
• Pedal reflex -pinching toes causes w/drawal of leg
• Ear flick
• Jaw tone
• Pharyngeal (swallowing)
• Laryngeal (coughing)
• Anal tone
• Visceral -touching an organ increases resp. effort
• Corneal -touch cornea and animal blinks, last to disappear before death

Question 10

Levels of Anaesthesia:
Stage 1

Describe

Answer 10

• Voluntary Excitement
• begins with the induction of anaesthesia.
• Animals are conscious and may display “fear, fight, flight” reactions.
• These may be modified with pre-anaesthetic agents

Question 11

Levels of Anaesthesia:
Stage 2

Describe

Answer 11

• Involuntary Excitement
• begins with the onset of unconsciousness and lasts until rhythmic breathing is established.
• There is reflex struggling and there may be loss of bladder and bowel control.

Question 12

Levels of Anaesthesia:
Stage 3

Describe

Answer 12

• Surgical Anaesthesia
• This stage is sub-divided into four “planes”
• Plane 1: Light Surgical
• Plane 2: Medium surgical
• Plane 3: Deep Surgical
• Plane 4: Excessively Deep Surgical

Question 13

Levels of Anaesthesia:
Stage 3: Surgical

Describe plane 1

Answer 13

• light surgical
• Intubation is possible
• Minor examinations and surgical procedures are possible.
• Pupil is located centrally
• Palpebral and corneal reflexes are present
• Withdrawal reflex is present
• Laryngeal and pharyngeal reflexes are present
• Jaw tone is strong
• Respiration is variable

Question 14

Levels of Anaesthesia:
Stage 3: Surgical

Describe plane 2

Answer 14

• Medium surgical
• Suitable for most procedures
• Pupil is rolled downwards
• Palpebral reflex disappears
• Withdrawal reflex is absent
• Laryngeal and pharyngeal reflexes are absent
• Jaw tone is relaxed
• Heart and respiratory rate are steady
• Painful stimuli increase the heart and respiratory rate
• Corneal reflex present

Question 15

Levels of Anaesthesia:
Stage 3: Surgical

Describe plane 3

Answer 15

• Deep surgical
• This depth is not necessary for most surgical procedures except where profound muscle relaxation is required
• Pupil is centrally fixed
• Palpebral reflex is absent
• Jaw tone is minimal
• Painful stimulus does not affect heart or respiratory rate
• Corneal reflex is barely present

Question 16

Levels of Anaesthesia:
Stage 3: Surgical

Describe plane 4

Answer 16

• Excessively Deep Surgical
• This stage is characterised by severe cardiovascular and respiratory depression
• Pupil is located centrally and is dilated
• All reflexes are absent

Question 17

Levels of Anaesthesia:
Stage 4

Describe

Answer 17

• Death
• Reflexes are absent, respiratory and cardiac arrest.

Question 18

How does deep levels of anaesthesia impair cardiac and respiratory function?

Answer 18

• tissue perfusion and oxygenation can become impaired leading to tissue damage and cell death.
• Respiratory rate and pulse rates on their own do not reflect the adequacy of the function of the lungs or the heart.

Question 19

What vital signs should be measured during anaesthesia?

Answer 19

• Pulse and heart rate (note also the rhythm and strength of pulse)
• Mucous membrane colour
• Capillary refill time
• Respiratory rate/effort/sounds
• Tidal volume
• Temperature

Question 20

How often should anaesthesia monitoring records be updated?

Answer 20

every 5 mins

Question 21

What is an oesophageal stethoscope used for?

Answer 21

to continuously monitor the heart and respiratory sounds.

The signal may be listened to via the earpieces or transmitted through a speaker

Question 22

What is an ap-alert respiratory monitor used for?

Answer 22

device sounds and alarm if a patient suffers apnoea (i.e. has not taken a breath after a specified time).

A beeping sound is usually emitted with each breath.

The disadvantage with this device is that no information is given on the adequacy of each breath

Question 23

What is a pulse oximeter used for?

Answer 23

• measures the pulse rate and the degree of oxygen saturation of arterial blood, by measuring the absorbency of particular wavelengths of red and infer-red light.
• Most instruments require a probe placed on non-pigmented skin

Question 24

What should be included on an anaesthetic record?

Answer 24

• Animal and procedure details
• Baseline vital signs (i.e. before anaesthesia)
• Drugs given before, during and in the immediate recovery period-drug name, dose and time given
• Anaesthetic regime or equipment used (e.g. endotracheal tube size, rates of administration of anaesthetic gases and vapours, type of anaesthetic machine)
• Vital signs recorded at five minute intervals
• Any relevant comments