lecture 5- monitoring depth of anesthesia

wilson

what is general anesthesia

1. loss of consciousness and sensation

2. include muscle relaxation, analgesia, suppression of stress response and hyponosis

3. reversible process

4. produced with I drug or a combination of drugs

explain stage of of anesthesia

positive reaction tot surgical stimulation

positive palpebral reflex

normal to dilated eye and pupil reflex

normal to low jaw tone

normal to high HR

normal to high RR

explain stage II of anesthesia

positive reaction to surgical stimulation

positive palpebral reflex

dilated eye and pupil reflex

tense jaw tone

increase HR

increase RR

when does the third eyelid become elevated during anesthesia

plane I and II

when does RR start to decrease during anesthesia

plane 2

when does jaw tone start to decrease during anesthesia

plane 2

when would apnea and cardiac arrest occur during anesthesia

stage IV

defined as the time from the start of administration of induction drugs until loss of consciousness

stage one

stage I is known as stage of ________

voluntary movement

if patient is excited during stage I what will occur

struggling, breath holding, increased heart rate, and pupil dilation due to epinephrine release, defecation, urination, salivation

what anesthesia stage is the most variable

stage I

how can stage II be characterized

stage of delirium and involuntary movement and last from loss of consciousness to onset of regular breathing pattern

a dog is starting to go into anesthesia what stage are they in with these signs

• vomiting

• laryngospasm

• jaw tone present

• increase HR

• increased or irregular respiratory

stage II

what is the stage of surgical anesthesia

stage III

why is stage III known as stage of surgical anesthesia

due to level of unconsciousness with progressive depression of reflexes, muscles relaxation and slow, regular breathing pattern

what is the main thing that can occur in plane I

vomiting reflex abolished

what is the main this occuring at plane 2

swallowing reflex abolished

what main thing do we notice going into stage III

loss of jaw tone

also known as “light” plane of anesthesia

stage III, plane I

what stage is mainly useful to note horse waking up

stage III, plane I

what is called a “medium” plane of anesthesia

stage III, plane II

most surgical procedures are performed at what plane

stage III, Plane II

a dog is going into anesthesia you notice these signs

• progressive intercostal paralysis

• respiration and heart rate stabilized

• sluggish palpebral reflex

• strong corneal reflex

• adequate muscle relaxation and analgesia

• abolished laryngeal reflexes

what stage is this

stage III, plane II

may be called “deep” plane of anesthesia or “deep plane of surgical anesthesia”

stage III, plane III

a dog is starting to go under anesthesia they are showing these signs what stage do you think they are in

• Decrease in heart rate

• Slow, shallow abdominal breathing pattern (“diaphragmatic respiration”)

• No jaw tone

• No reaction to surgical stimulation, profound muscle relaxation

• No palpebral reflex, weak corneal reflex

• Pupil progressively dilated and central

stage III, plane III

a dog is starting to go under anesthesia and is showing these signs what stage are they in

• Pupils dilated

• Hypotension progressing to shock

• Slow CRT

• Slow, irregular respirations

• Lack of muscle tone

• No anal sphincter tone

stage III, plane IV

this is your first time monitoring a dog during anesthesia. You thought that you might have noticed there was slight reaction so you decided to crank the anesthesia WAY up. When you did this you started to notice wide dilated pupils, pale mucus membrane, extreme CNS depression, absent ocular reflexes, flaccid muscle tone. what is happening, what did you do wrong, and what will happen

the animal is now in stage IV of anesthesia this is due to anesthetic over dose and if you do not decrease the amounts RIGHT NOW the animal will die. This is due to drastically increase the anesthetic amount more than required

you are checking ocular signs during anesthesia what should you be checking

papebral reflex

eye position

lacrimation

nystagmus

corneal reflex

what are the main things to check to monitor death of anesthesia

ocular sign

jaw tone

anal reflex

pedal reflex

ovreall muscle tone or degree of patient relaxation

what is the goal for a surgical anesthesia plane

• Relaxed jaw tone…is it easy to open with 2 fingers?

• Mild to no palpebral reflex

• Ventral medial eye rotation

• Relaxed anal tone

• Smooth, regular respiratory pattern

• Normal heart rate and BP

• No swallowing, coughing, vomiting or laryngospasm

horse specific signs to look for

lacrimate in light stages of anesthesia. Eyes stay central instead of ventral medial eye rotation. Nystagmus in lighter stage. Corneal reflex persists into deeper anesthesia plane

cat specific anesthesia signs

may go into laryngospasm and/or may retain cough, swallow, and vomiting refelx until they reach a deeper plane of anesthesia

cattle specific signs to look for with anesthesia

consistent, reliable eyeball rotation

rodent specific signs

obeserve feet, ears, muzzle for pallor or cyanosis

pedal reflex

poultry specific signs

examine comb and/or wattle for pallor

vent reflex

rabbit specific signs

can use the color of light reflected from the eye to determine circulation status

what drugs are known to make a difference with depth monitoring

ketamine- typical eye signs not produced

propofol-apnea not a problem for intubation

hypoxia and hypothermia are _____

anesthetic

what is another method for monitoring measure depth and how is it used

anesthetic gas analyzer

• perform MAC

what also could be used for monitoring

bispectral index (BIS)

what are important things to remember for recovery

progresses in reverse order

every species and patient will recover differently

treat post-op pain if suspected, start before awake

stage II can be a difficult time due to delirium/dysphoria, especially in equine patients

horses are typically sedated with

alpha 2 agonist going into inhalant anesthesia