Depth of Anesthesia Flashcards
Signs used to monitor anesthetic depth
- Physical signs (subjective)
2. Physiologic parameters of the autonomic system
How do you monitor neurologic depression?
EEG- Bi-spectral analysis
Bispectral analysis
Processed EEG that monitors cortical activity
The lower the number, the more depressed (0-100)
Is BIS always accurate and useful?
No, depends on the person, but not a practical modality in vet med
Physical signs of anesthetic depths
- Prescence/absence of purposeful movement in response to stimuli
- Muscle relaxation
- Lack of reflexes
- Autonomic signs
Which muscles are checked for tones?
Eyeball rotation, jaw tone, anal tone, abdominal muscle tone
Which reflexes are checked?
Palpebral, corneal, anal, pupillary light (not terribly useful
Four stages of gas anesthetic depth
I- Analgesia
II- Delirium
III- Surgical Anesthesia
IV- Medullary paralysis
Are there clear demarcations between stages?
No
What order do the reflexes dissapear in?
Palpebral–Pharyngeal–corneal–light
Can these signs/stages be disrupted by the use of other drugs?
Yes, they are only based on gas anesthesia so using any injectable with disrupt the signs
T/F:If there is no response to a particular stimulation, there will be no response to any stimulation.
False
Eg, lack of movement to a toe pinch does not mean that there will be lack of movement to a surgical stimulus
What reflex should always be present in an anesthetized patient?
Corneal
Gag/swallow and palpebral reflexes present indicate they are too light
What is assessed for a baseline idea of anesthesia depth?
Jaw tone- should be easily moved by two fingers and tested throughout anesthesia
What position of the eye suggests that an animal is too deep?
Central
Eyes should be rolled ventrally with no palpebral reflex
What is indicated with the size of the palpebral fissure
Small- light anesthesia, may/may not have palpebral reflex
Large- deeper plane
Always assess with jaw tone
What is an ocular sign of light anesthesia in a horse?
Tearing
Which way do eyes tend to roll in large animals?
Forward
Which animals are eye signs not helpful in?
Swine
Is pupil size a good indication of anesthetic depth?
No, typically appears as pin point to mid size depending on drugs used
What pupil sign is bad?
Fixed and dilated- medullary paralysis
Should both eyes be assessed?
Yes
Equine eye sign
Brisk nystagmus- reliable sign of very light anesthesia, movement risk
Signs of Light anesthesia
Toe pinch +/- Palpebral + esp horses Corneal + Lacrimation +/- Eye position Central Jaw tone + Abdominal breathing +/-
Signs of Moderate anesthesia
Palpebral
Corneal - (may be +/- in horses)
Eye position Deviated
Signs of Deep anesthesia
Corneal - when too deep
Eye position central
Abdominal breathing +/-
Gradual decrease in HR/RR is an indication of?
Adequate depth
Autonomic response is responsible for…
Increase in HR/RR at induction
Avoid excessive excitation at induction
Common causes of Increased RR
- Too light (pain/stimulation)
- Hypercapnia
- Hypoxemia
- Hyperthermia
Common causes of Increased BP
- Pain/stimulation
2. Renal dz/ catecholamine releasing tumors
Common causes of Increased HR
- Pain/stimulation
- Hypovolemia/hypotension
- Hypercapnia
- Hypoxemia
- Recovery phase
Common causes of Decreased RR
- Drugs- Opioids
- Too deep
- Medullary ischemia (apnea)
Common causes of Decreased BP
- Effect of most anesthetic agents
2. Shock/hypovolemia
Common causes of Decreased HR
- Vagal stimulation- drugs, visceral manuvering
- Hypothermia
- End stage overdose
What can be heard with an esophageal stethoscope?
Heart rate and rhythm, breath sounds
Ideal heart rates
Small dogs 70-120 Large dogs 50-100 Cats 120-180 Horse 25-40 Calves/Sheep/Goats 80-120 Bovine 60-90
What respiratory rates is appropriate?
Depends on tidal volume
If adequate PaCO2 then monitor as normal
Pulse quality
Always feel pulse from femoral, radial, or lingual artery prior and after induction/intubation
Get an impression of SV or BP
What are pale MM indicative of?
Low CO, poor perfusion, anemia, vasoconstricion, hypothermia
What are pink/red MM indicative of?
May be normal or sepsis/vasodilation
Anesthesia records
Allows of trends of vital signs
Permanent legal document
Fulfills requirement of good practice standards
What is recorded on an anesthesia record?
Patient info, conditions, medications Procedure name and performers Drug information HR, RR, BP, ETCO2, spO2, Temp Any issues
