Monitoring Depth of Anesthesia Flashcards
anesthesia is a controlled and reversible loss of
consciousness (cortical and subcortical activites)
nociception (subcortical activity)
mobility (ventral horn)
when monitoring depth of anesthesia
both coritcal and subcortical activites need to be assessed
T/F 3x more anesthetic is needed to inhibit movement then to inhibit consciousness
True
if patient does not move it is extremely unlikely to be conscious
subcortical acitivites and reflexes
eye movement and position
eyelid, eyelash and corneal reflexes
pupillary light reflex
jaw and tongue tones
anal tone and reflex
muscle tone
repiratory/ pulse rate and rhythm
response to nociceptive stimulus
the subcortical activities and reflexes are evaluating
brainstem
craninal nerves
spinal cord reflexes
automonic nervous system
T/F during neuromuscular blockade immobility cannot be used to ensure unconsciousness
True
how can cortical activity (consciousness) be monitored during neuromuscular blockade
end-tidal anesthetic % can be measured
EEG or BIS monitor can be used
T/F EEGs give information about coritcal but not subcortical activites
True
T/F EEGs correlate with aesthetic depth but does not predict arousal (or movement) in response to noxious stimulus
True
nociception is a subcortical function
stages of anesthesia are based on:
observing subcortical brain activities and reflexes
stage 1
voluntary movement
drug administration → loss of consciousness
pupillary dilation, tachycardia, irregular breathing
stage 2
involuntary movement (excitement phase)
loss of consciousness → onset on regular breathing
tachycardia, pupillary dilationm strong palpebral and eyelash reflexes
strong jaw tone - intubation not possible/difficult
Stage 3
general anesthesia
onset of regular breathing → cessation of effective breathing
no movement in response to noxious stimuli
progessvie muscle relaxation, loss of reflexes and respiratory depression
stage 3 plane 1
light anesthesia
nystagmus, weakend palpebral and corneal reflexes
simple procedures/examinations may be possible
stage 3 plane 2
medium plane of anesthesia
weak palpebral, strong corneal reflexes
adequate muslce relaxation for most surgical procedures
stage 3 plane 3
deep anesthesia
no palpebral/corneal reflexes
some patients may have to be maintained at this stage but ideally should decrease to plane 2
stage 4
overdose
respiratory failure, cardiac arrest, death from overdose
T/F cardiovascular adverse effects are possible even if isoflurane is not overdosed
True
T/F overdosing isoflurane may not always cause hypotension, shock and death (or not as soon)
True
T/F if hypotension is concerning, anesthetic administration may have to be decreased regardless of current anesthetic depth
True
what stage are most surgeries and intubation are performed at
stage 3, planes 2-3
T/F adverse behavioral effects during stages 1-2 before and after anesthesia are treated with sedatives
True
what can be seen with ketamine
nystagmus, blinking, central eye position and dilated pupils
goals of anesthetic depth
acceptable cardiovascular function
fully relaxed and immobile patient
least necessary anesthetic depth
T/F central eye + fixed pupils may indicate both too light or too deep anesthesia
True
nystagmus
most likely indicate too light anesthesia
may happen with ketamine even at appropriate depth
if spontaneous RR is high (>20 br/min) it may indicate
too light anesthesia
low lung volume or tidal volume
T/F absolute HR does not aid determining anesthetic depth
True
common causes of increased HR
surgical stimulus (nociception)
life threatening stress (hypoxemia)
anemia, hypovolemia, shock, hyperthermia
common cause of decreased HR
drugs (opioids, alpha 2 agonists)
hypothermia
