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Principles I Test 4

Neurological Monitoring and LOC

Define explicit memory conscious recall or remembering of previous experiences
Define implicit memory movement and ability to respond to commands without conscious recall of events; "awareness without recall"
What are 3 ways that awareness can occur? light anesthesia, patients who require increased levels of anesthetics, an anesthetic delivery problem (rare)
BIS monitors analyze _____________________ using a sensor on the forehead. Memory is considered a biochemical function occurring in the _____________ cortical electrical activity; hippocampus
True or False: there is only one reliable indicator of light anesthesia and/or increased incidence of awareness False!!! There are NO reliable indicators of light anesthesia and/or increased incidence of awareness
What are some clinical signs of being under light anesthesia minor patient movement, tearing and sweating (SNS outflow), tachycardia, hypertension, increased respiratory rate and depth (if spontaneous respiration)
What are some drugs that mask physiological responses to light anesthesia? amphetamines, beta blockers, calcium channel blockers, neuromuscular blockers, high levels of vitamin C
There is a ________ increase in patient reported awareness when a NMB was on board during the case. 17 x
What are some ways to help prevent the occurrence of awareness? premedicate with an amnestic, volatile anesthetic at > 0.7 MAC (end-tidal, not dial set), develop awareness policy & educate staff, informed consent, multiple monitors, avoid complete NMB unless required, redose induction agent during difficult intubation
How does an EEG work? it detects decreases in perfusion and ultimately ischemia based on reductions in electrical brain activity
Describe what is seen on an EEG that is indicative of an ischemic state? decreased amplitude and increased latency
What is the average cerebral blood flow? 50 mL/100 gm/min; but it can vary regionally from 30 - 300 mL/100 gm/min
At what cerebral blood flow will you see slowing on an EEG? < 25 mL/100 gm/min
At what cerebral blood flow will you see an isoelectric EEG? ~ 15-20 mL/100 gm/min
Does an isoelectric EEG mean cell death? No; decreased electricity from cell to cell but the inside of the cells are still alive
At what cerebral blood flow is there decreased cell integrity and irreversible cell injury? < 10 mL/100 gm/min
At what cerebral perfusion pressure will you see EEG changes? < 50 mmHg (or torr)
What cerebral perfusion pressure indicated decreased cell integrity and irreversible cell death? < 25 mmHg (or torr)
Hypothermia, hypercapnia, electrolyte imbalances, and volatile anesthetics show EEG readings that resemble what? ischemic changes
What two pathological events in a patient's history make the reliability of the EEG questionable? tumors and prior brain damage
Normally EEG is a measurement of the differences in ______________ in groups of neurons between brain regions electrical potentials
The amount of cerebral blood flow that creates electrical failure on the EEG reading is ________ than the amount needed to maintain cell integrity. greater
The EEG picks up ischemia _________ cell integrity is compromised. before
Which type of wave on the EEG is 8 - 12 Hz and is a major rhythm seen in normal resting awake adults? alpha waves
Which type of wave on the EEG is 13 - 40 Hz and represent fast activity, alertness, concentration, anxious or busy thinking? beta waves
Which type of wave on the EEG is 4 - 7 Hz, is considered abnormal in awake adults but normal in young children, and can indicate encephalopathy or subcortical lesions? theta waves
Which type of wave on the EEG is 1 - 3 Hz, is indicative of subcortical lesions or encephalopathy or hydrocephalus, and is normal in babies? delta waves
Which type of EEG wave is representative of an awake patient? beta
Which type of EEG wave is representative of a patient under moderate sedation? alpha
Which type of EEG wave is representative of a patient under general anesthesia? theta
Which type of EEG wave is representative of a patient under deep anesthesia? delta
How do barbiturates and benzodiazepines affect EEG recordings? initially accentuate frequency but then decrease it
How do opioids affect EEG recordings? slow frequency but increase amplitude
How do inhalation agents affect EEG recordings? decrease frequency and decrease amplitude
Does myoclonus that can occur with induction agents like etomidate show up on EEG recordings? No!
How does the Bispectral Index System (BIS) work? it analyzes raw EEG data and derives a formula driven numerical value to indicate level of consciousness
The BIS monitor assumes slow electoral activity correlates with ____________ deep anesthesia
With the BIS, what number value correlates with general anesthesia? 40 - 60
What BIS value correlates with an increased probability of recall? 70
What BIS value correlates with a deep hypnotic state? 20 - 40
What BIS value correlates with burst suppression? 0 - 20
What BIS value correlates with a flat line EEG? 0
What BIS value correlates with a patient who is responsive to loud commands or mild prodding/shaking? 60 - 80
What BIS value correlates with a patient who is awake and responsive to a normal voice? 80 - 100
What is burst suppression? EEG generally slows but shows random bursts of electrical activity; highly unpredictable and seen with a decrease in cerebral circulation and oxygenation as well as hypothermia (especially during CPB)
What is an SSEP? stimulation of a peripheral nerve sends electrical signal to brain where electrodes sense response
What does an SSEP assess anatomically? the integrity of the sensory pathway - the dorsal column of the spinal cord
What does increased latency and decreased amplitude indicate on an SSEP? damage to the neuronal pathway
What produces a dose dependent increase in SSEP latency and decrease in amplitude? volatile anesthetics
60% nitrous decreases SSEP amplitude but has ____ effect on latency no
IV anesthetics affect SSEP _____ than volatile anesthetics less
Which two anesthetic drugs increase SSEP amplitude? etomidate and ketamine
True or false: opioids have the most effect on SSEP amplitude False! opioids have little to no effect on SSEP amplitude
What is an MEP? transcranial magnetic or electrical stimulation of the cortex or direct stimulation of the spinal cord allows detection of action potentials in the muscles if the neural pathway is intact
What does an MEP assess anatomically? the ventral spinal cord (motor pathways)
Do neuromuscular blocking drugs affect MEP readings? Yes
Anesthesia affects the transcranial MEP method _____ than the direct spinal stimulation MEP method more
Which is the better monitoring choice for spinal surgery and why: MEP or SSEP? MEP - because it monitors motor pathways (ventral spinal cord) & if it is sensitive & specific enough it can indicate which patients may develop a post-op motor deficit
Describe Stage I Anesthesia. analgesia and disorientation with no substantive changes in respiration, HR, pupillary activity, reflexes or muscle tone
Stage II anesthesia is characterized by delirium, agitation, and excitement. What respiratory patterns, reflexes, and muscle tone is associated with this stage? respiratory = irregular/apnea; reflexes = hyperactive; muscle tone = hyperactive often with thrashing extremities
What stage of anesthesia is a patient in if their pharyngeal reflexes and eyelid reflexes are eliminated, respirations are regular, and muscle tone is normal to slightly reduces? Stage III Plane 1
What stage of anesthesia is a patient in if their laryngeal reflex is eliminated, respirations are regular though reduced in volume and rate, and muscle tone progressively reduces? Stage III Plane 2
What stage of anesthesia is a patient in if their carinal reflex is eliminated (no coughing) and respirations have markedly reduced rate? Stage III Plane 3
What stage of anesthesia is a patient in if all reflexes are absent and the physiologic capacity for respiration is virtually eliminated? Stage III Plane 4
Medullary paralysis and progressive cardiovascular collapse are characteristic of which stage of anesthesia? Stage IV
True or false: the rate, rhythm and muscles used for respiration are calculable indicators of depth of anesthesia True!
What is the difference between eye gaze (Ether eye signs) during Stage II and Stage III? In stage II gaze is disconjugate and in stage III gaze becomes congruent again
Tearing indicates _________ while dry eyes can indicate ___________ light anesthesia; deep anesthesia
What cerebral oximetry reading indicates a possible reduction in cerebral O2? regional sat < 40% OR changes > 25% of baseline
Why is it important to establish a baseline cerebral oximetry reading before you give O2 or put the patient to sleep? the change in cerebral oximetry from baseline is a more important indicator of a decrease in blood flow than the actual number itself.
When is cerebral oximetry indicated? cardiac surgery, carotid endarterectomy, cerebral autoregulation, and beach chair position surgeries
What is the evidence to support cerebral oximetry? evidence is weak, and it is not a standard of care
Created by: Mary Beth