Neurological Monitoring and LOC
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| Define explicit memory | conscious recall or remembering of previous experiences
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| Define implicit memory | movement and ability to respond to commands without conscious recall of events; "awareness without recall"
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| What are 3 ways that awareness can occur? | light anesthesia, patients who require increased levels of anesthetics, an anesthetic delivery problem (rare)
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| BIS monitors analyze _____________________ using a sensor on the forehead. Memory is considered a biochemical function occurring in the _____________ | cortical electrical activity; hippocampus
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| 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
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| 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)
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| What are some drugs that mask physiological responses to light anesthesia? | amphetamines, beta blockers, calcium channel blockers, neuromuscular blockers, high levels of vitamin C
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| There is a ________ increase in patient reported awareness when a NMB was on board during the case. | 17 x
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| 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
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| How does an EEG work? | it detects decreases in perfusion and ultimately ischemia based on reductions in electrical brain activity
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| Describe what is seen on an EEG that is indicative of an ischemic state? | decreased amplitude and increased latency
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| What is the average cerebral blood flow? | 50 mL/100 gm/min; but it can vary regionally from 30 - 300 mL/100 gm/min
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| At what cerebral blood flow will you see slowing on an EEG? | < 25 mL/100 gm/min
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| At what cerebral blood flow will you see an isoelectric EEG? | ~ 15-20 mL/100 gm/min
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| Does an isoelectric EEG mean cell death? | No; decreased electricity from cell to cell but the inside of the cells are still alive
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| At what cerebral blood flow is there decreased cell integrity and irreversible cell injury? | < 10 mL/100 gm/min
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| At what cerebral perfusion pressure will you see EEG changes? | < 50 mmHg (or torr)
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| What cerebral perfusion pressure indicated decreased cell integrity and irreversible cell death? | < 25 mmHg (or torr)
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| Hypothermia, hypercapnia, electrolyte imbalances, and volatile anesthetics show EEG readings that resemble what? | ischemic changes
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| What two pathological events in a patient's history make the reliability of the EEG questionable? | tumors and prior brain damage
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| Normally EEG is a measurement of the differences in ______________ in groups of neurons between brain regions | electrical potentials
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| The amount of cerebral blood flow that creates electrical failure on the EEG reading is ________ than the amount needed to maintain cell integrity. | greater
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| The EEG picks up ischemia _________ cell integrity is compromised. | before
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| Which type of wave on the EEG is 8 - 12 Hz and is a major rhythm seen in normal resting awake adults? | alpha waves
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| Which type of wave on the EEG is 13 - 40 Hz and represent fast activity, alertness, concentration, anxious or busy thinking? | beta waves
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| 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
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| 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
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| Which type of EEG wave is representative of an awake patient? | beta
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| Which type of EEG wave is representative of a patient under moderate sedation? | alpha
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| Which type of EEG wave is representative of a patient under general anesthesia? | theta
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| Which type of EEG wave is representative of a patient under deep anesthesia? | delta
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| How do barbiturates and benzodiazepines affect EEG recordings? | initially accentuate frequency but then decrease it
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| How do opioids affect EEG recordings? | slow frequency but increase amplitude
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| How do inhalation agents affect EEG recordings? | decrease frequency and decrease amplitude
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| Does myoclonus that can occur with induction agents like etomidate show up on EEG recordings? | No!
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| 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
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| The BIS monitor assumes slow electoral activity correlates with ____________ | deep anesthesia
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| With the BIS, what number value correlates with general anesthesia? | 40 - 60
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| What BIS value correlates with an increased probability of recall? | 70
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| What BIS value correlates with a deep hypnotic state? | 20 - 40
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| What BIS value correlates with burst suppression? | 0 - 20
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| What BIS value correlates with a flat line EEG? | 0
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| What BIS value correlates with a patient who is responsive to loud commands or mild prodding/shaking? | 60 - 80
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| What BIS value correlates with a patient who is awake and responsive to a normal voice? | 80 - 100
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| 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)
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| What is an SSEP? | stimulation of a peripheral nerve sends electrical signal to brain where electrodes sense response
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| What does an SSEP assess anatomically? | the integrity of the sensory pathway - the dorsal column of the spinal cord
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| What does increased latency and decreased amplitude indicate on an SSEP? | damage to the neuronal pathway
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| What produces a dose dependent increase in SSEP latency and decrease in amplitude? | volatile anesthetics
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| 60% nitrous decreases SSEP amplitude but has ____ effect on latency | no
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| IV anesthetics affect SSEP _____ than volatile anesthetics | less
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| Which two anesthetic drugs increase SSEP amplitude? | etomidate and ketamine
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| True or false: opioids have the most effect on SSEP amplitude | False! opioids have little to no effect on SSEP amplitude
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| 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
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| What does an MEP assess anatomically? | the ventral spinal cord (motor pathways)
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| Do neuromuscular blocking drugs affect MEP readings? | Yes
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| Anesthesia affects the transcranial MEP method _____ than the direct spinal stimulation MEP method | more
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| 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
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| Describe Stage I Anesthesia. | analgesia and disorientation with no substantive changes in respiration, HR, pupillary activity, reflexes or muscle tone
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| 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
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| 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
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| 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
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| 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
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| 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
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| Medullary paralysis and progressive cardiovascular collapse are characteristic of which stage of anesthesia? | Stage IV
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| True or false: the rate, rhythm and muscles used for respiration are calculable indicators of depth of anesthesia | True!
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| 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
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| Tearing indicates _________ while dry eyes can indicate ___________ | light anesthesia; deep anesthesia
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| What cerebral oximetry reading indicates a possible reduction in cerebral O2? | regional sat < 40% OR changes > 25% of baseline
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| 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.
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| When is cerebral oximetry indicated? | cardiac surgery, carotid endarterectomy, cerebral autoregulation, and beach chair position surgeries
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| What is the evidence to support cerebral oximetry? | evidence is weak, and it is not a standard of care
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Created by:
Mary Beth
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