Monitoring Depth Of Anesthsia Flashcards
Anesthesia i a controlled and reversible loss of consciousness, nociception, and mobility. Where do these functions originate?
Consciousness: cortical and subcortical activities
Nociception: subcortical activity
Mobility: spinal cord (ventral horn)
T/F: 3 times more anesthetic is needed to inhibit movement than to inhibit consciousness
True
** if the patient does not move, it is extremely unlikely to be conscious
What is the common method of monitoring anesthetic depth of animals?
Subjective monitoring of subcortical activities/reflexes
What are the subcortical activities and reflexes that we usually monitor during anesthesia?
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
T/F: during neuromuscular blockade, immobility cannot be used to ensure unconsciousness
True
Many subcortical signs are lost
—> monitor with end-tidal anesthetic % (about 3% isoflourene is required for unconsciousness)
T/F: an EEG can be used to monitor response to noxious stimulus and predict arousal in an anesthetized patient
False
Arousal and response to noxious stimulus are subcortical functions
EEG only gives information about consciousness with is a cortical activity
What is a BIS monitor ?
Bispectral index
-based on EEG but is easier to interpret
What regions are inhibited by anesthesia first?
Brain stem
Spinal cord
Cortex
Cortex -> brainstem -> spinal cord
What is stage 1 of anesthesia?
From drug administration to loss of consciousness
What is stage 2 of anesthesia?
Involuntary movement - From loss of consciousness until onset of regular breathing
What is stage 3 of anesthesia ?
General anesthesia
From onset of regular breathing until the cessation of effective breathing
What is stage 4 of anesthesia ?
Overdose
Don’t do this
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
Stage 1: voluntary movement
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
Stage 2: involuntary movment
What stage of anesthesia is this…
No movement to noxious stimulation
Progressive muscle relaxation, loss of reflexes and respiratory depression
Stage 3
How many planes are there in stage 3 anesthesia?
3 (sometimes a 4th is distinguished)
What plane of anesthesia is this…
Nystagmus, lacrimation Weakening of palpebral and corneal reflexes No swallow reflex Pupils constricted No voluntary moment
Stage 3- plane 1
What plane of anesthesia is this..
Progressive intercostal paralysis
Stable respiration and pulse
Loss of laryngeal reflexes
Weak palpebral, strong corneal reflex
Stage 3- plane 2
What plane of anesthesia is this..
Diaphragmatic breathing
Pupils dilate, eyes central
No palpebral/corneal reflexes
Stage 3- plane 3
What stage of anesthesia is most suitable for most procedures?
Stage 3- plane 2
What stage of anesthesia is this…
Respiratory failure
Cardiac arrest
Stage 4 - overdose
T/F: apnea is a sign of stage 4 anesthetic depth, therefore you should reduce your anesthetic
False
Apnea can occur at lighter planes due to drug effect (opioids, propofol, ISO)
-> can be treated easily my mechanical ventilation and 100% O2
What should you do if your patient develops a concerning hypotension during anesthesia?
Decrease anesthetic admin
-> may have to administer fluid bolus
T/F: ketamine as an inductive agent suppresses brain activity
False
Dissociative anesthetic
- does not suppress brain activity
- neural information is processed without proper coordination in space and time
What can rotated eyes indicate about your anesthetic depth?
Stage 3- plane 2
Rotation is ideal but not mandatory
Central eye and dilated pupils can indicate what about your anesthesia ?
Too light or too deep
Need to distinguish !!
What does a nystagmus indicate about anesthesia?
Too light - arousal may be imminent
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?
This could indicate anesthesia is too light
But remember ketamine can cause a nystagmus even at an appropriate anesthetic depth
Blinking may indicate what about anesthesia ?
Too light
-unless this is a horse-> can have slow blinking at acceptable depth of anesthesia
What should you see for a palpebral reflex at appropriate anesthetic depth?
Slow reflex, or lack of reflex
If your respiration rate is high (>20br/min) this can indicate?
Too light anesthesia (changing respiratory rate and pattern in response to surgical stimulus)
OR
Low lung volume
What are common causes of HR increase?
Surgical stimulus
Life threatening stress
Anemia, hypovolemia, shock, hyperthermia
What are common causes of HR decrease?
Drug and hypothermia
