Monitoring Depth Of Anesthsia

Question 1

Anesthesia i a controlled and reversible loss of consciousness, nociception, and mobility. Where do these functions originate?

Answer 1

Consciousness: cortical and subcortical activities

Nociception: subcortical activity

Mobility: spinal cord (ventral horn)

Question 2

T/F: 3 times more anesthetic is needed to inhibit movement than to inhibit consciousness

Answer 2

True

** if the patient does not move, it is extremely unlikely to be conscious

Question 3

What is the common method of monitoring anesthetic depth of animals?

Answer 3

Subjective monitoring of subcortical activities/reflexes

Question 4

What are the subcortical activities and reflexes that we usually monitor during anesthesia?

Answer 4

Eye movement and position

Eyelid, eyelash, and corneal reflexes

Pupillary light reflex

Jaw and tongue tone

Anal tone and reflex

Muscle tone

Respiratory/pulse rate and rhythm

Responses to nociceptive stimulus

Question 5

T/F: during neuromuscular blockade, immobility cannot be used to ensure unconsciousness

Answer 5

True

Many subcortical signs are lost

—> monitor with end-tidal anesthetic % (about 3% isoflourene is required for unconsciousness)

Question 6

T/F: an EEG can be used to monitor response to noxious stimulus and predict arousal in an anesthetized patient

Answer 6

False

Arousal and response to noxious stimulus are subcortical functions

EEG only gives information about consciousness with is a cortical activity

Question 7

What is a BIS monitor ?

Answer 7

Bispectral index

-based on EEG but is easier to interpret

Question 8

What regions are inhibited by anesthesia first?

Brain stem
Spinal cord
Cortex

Answer 8

Cortex -> brainstem -> spinal cord

Question 9

What is stage 1 of anesthesia?

Answer 9

From drug administration to loss of consciousness

Question 10

What is stage 2 of anesthesia?

Answer 10

Involuntary movement - From loss of consciousness until onset of regular breathing

Question 11

What is stage 3 of anesthesia ?

Answer 11

General anesthesia

From onset of regular breathing until the cessation of effective breathing

Question 12

What is stage 4 of anesthesia ?

Answer 12

Overdose

Don’t do this

Question 13

What stage of anesthesia is this..

Excitement and struggle may occur 
Epinephrine release, tachycardia, and pupillary dilation 
Irregular breathing, coughing 
Salivation, urination, defecation 
Ataxia, recumbency

Answer 13

Stage 1: voluntary movement

Question 14

What stage of anesthesia is this..

State of delirium
Struggling and exaggerated rxn to stimuli
Epi release, tachycardia, pupillary dilation
Strong palpebral and eyelash reflexes
Irregular breathing
Vomiting, regurgitation, salivation
Strong jaw tone

Answer 14

Stage 2: involuntary movment

Question 15

What stage of anesthesia is this…

No movement to noxious stimulation
Progressive muscle relaxation, loss of reflexes and respiratory depression

Answer 15

Stage 3

Question 16

How many planes are there in stage 3 anesthesia?

Answer 16

3 (sometimes a 4th is distinguished)

Question 17

What plane of anesthesia is this…

Nystagmus, lacrimation 
Weakening of palpebral and corneal reflexes 
No swallow reflex 
Pupils constricted 
No voluntary moment

Answer 17

Stage 3- plane 1

Question 18

What plane of anesthesia is this..

Progressive intercostal paralysis
Stable respiration and pulse
Loss of laryngeal reflexes
Weak palpebral, strong corneal reflex

Answer 18

Stage 3- plane 2

Question 19

What plane of anesthesia is this..

Diaphragmatic breathing
Pupils dilate, eyes central
No palpebral/corneal reflexes

Answer 19

Stage 3- plane 3

Question 20

What stage of anesthesia is most suitable for most procedures?

Answer 20

Stage 3- plane 2

Question 21

What stage of anesthesia is this…

Respiratory failure
Cardiac arrest

Answer 21

Stage 4 - overdose

Question 22

T/F: apnea is a sign of stage 4 anesthetic depth, therefore you should reduce your anesthetic

Answer 22

False

Apnea can occur at lighter planes due to drug effect (opioids, propofol, ISO)
-> can be treated easily my mechanical ventilation and 100% O2

Question 23

What should you do if your patient develops a concerning hypotension during anesthesia?

Answer 23

Decrease anesthetic admin

-> may have to administer fluid bolus

Question 24

T/F: ketamine as an inductive agent suppresses brain activity

Answer 24

False

Dissociative anesthetic

• does not suppress brain activity
• neural information is processed without proper coordination in space and time

Question 25

What can rotated eyes indicate about your anesthetic depth?

Answer 25

Stage 3- plane 2

Rotation is ideal but not mandatory

Question 26

Central eye and dilated pupils can indicate what about your anesthesia ?

Answer 26

Too light or too deep

Need to distinguish !!

Question 27

What does a nystagmus indicate about anesthesia?

Answer 27

Too light - arousal may be imminent

Question 28

You have used ketamine to induce your anesthesia, you start to see a nystagmus during your procedure, should you increase the amount of anesthetic agent?

Answer 28

This could indicate anesthesia is too light

But remember ketamine can cause a nystagmus even at an appropriate anesthetic depth

Question 29

Blinking may indicate what about anesthesia ?

Answer 29

Too light

-unless this is a horse-> can have slow blinking at acceptable depth of anesthesia

Question 30

What should you see for a palpebral reflex at appropriate anesthetic depth?

Answer 30

Slow reflex, or lack of reflex

Question 31

If your respiration rate is high (>20br/min) this can indicate?

Answer 31

Too light anesthesia (changing respiratory rate and pattern in response to surgical stimulus)
OR
Low lung volume

Question 32

What are common causes of HR increase?

Answer 32

Surgical stimulus
Life threatening stress
Anemia, hypovolemia, shock, hyperthermia

Question 33

What are common causes of HR decrease?

Answer 33

Drug and hypothermia