Test 1 part IV (CM) Flashcards
Electrical activity from the surface of the brain observed through electroencephalogram (EEG)
Electrical Brainwaves
What are indications of EEG monitoring?
diagnosis of hypoxia, brain trauma, ischemic/hemorrhagic CVA
The rate/duration between impulses
Frequency
The peak to peak measurements
Amplitude
The shape comprised of wave amplitude and frequency
Morphology
Which EEG wave: high level information processing
Gamma (>40)
Which EEG wave: normal awake consciousness, alertness, logic, & critical thinking. During an awake state, these are most prominent
Beta (14-40)
Which EEG wave: occurs with eyes closed during deep relaxation
Alpha (7.5 - 14)
Which EEG wave: appear during light sleep. Appear with increases in ischemia/hypoxia.
Theta (4 - 7.5)
Which EEG wave: appear in deep sleep
Delta (0.5 - 4)
The onset of irreversible damage can be determined when there is complete electrical silence, evidenced by an ________ EEG pattern.
Isoelectric
What are the neurophysical parameters that can be monitored during anesthesia & surgery?
- Cerebral electrical activity
- Cerebral blood flow
- Cerebral O2 content
- ICP
- Cerebral metabolic rate of O2 consumption (CMRO2)
The majority of anesthetic agents inhibit neuronal activity and depress EEG waveforms. How does this manifest on the EEG waveform?
Increased frequency and decreased amplitude of the EEG waveform.
What are the effects of inhalational agents on an EEG?
Dose-dependent reduction in CMRO2, decreased regional tissue O2 consumption, and vascular constriction
Global reduction in CBF → dependent on the direct vasodilatory properties of the individual drug and the vasoconstricting effects associated with catecholamine release
Which is worse for depression of an EEG, Inhalational agents or TIVA?
Inhalational > TIVA in depression of EEG
______ & ______ provide a summary of each wave over a period of time & analyze for waveform relationships using amplitude frequency and graphs. Used to determine depth of anesthesia or unilateral injury
Compressed Spectral Array (CSA) & Density Spectral Array (DSA)
An EEG pattern associated with alternating high-voltage, mixed frequency, slow wave activity with periods of electrical suppression.
-Electrical activity is unpredictable, and duration is variable.
Burst Suppression
What conditions usually result in Burst Suppression?
- A decrease in cerebral circulation & oxygenation
- Hypothermia
May be desirable during manipulation of brain tissues as it decreases CMRO2 , which is neuroprotective.
Burst Suppression
What type of burst suppression is indicative of ischemia or injury to the brain?
Unilateral Burst Suppression
Which anesthetic agents cause Burst Suppression?
- Etomidate
- Propofol
- Dexmedetomidine
- Inhalation agents
At what dose range do inhalational agents cause Burst Suppression?
> 1.2 - 1.5 MAC
What is the effect of Etomidate on an EEG?
Suppression of electrical activity (inc frequency and dec amplitude of beta waves) and epileptiform activity.
-Burst Suppression achieved at higher dose ranges
What is the effect of Propofol on an EEG?
Suppression of electrical activity (inc frequency and dec amplitude of beta waves).
-Burst Suppression achieved at higher dose ranges, but at higher doses, Propofol decreases SVR, leading to a drop in CPP.
What is the effect of Dexmedetomidine on an EEG?
Suppression of electrical activity
-Can cause Burst Suppression
Which anesthetic agents do NOT cause Burst Suppression?
- Nitrous Oxide
- Benzos/Opioids
- Ketamine
What is the effect of Benzos/Opioids on an EEG?
Suppression of electrical activity, but do not cause Burst Suppression
What is the effect of Ketamine on an EEG?
Disorganized and epileptiform activity, but does not cause Burst Suppression
Does Nitrous Oxide cause Burst Suppression?
No
Non-invasive transcutaneous monitoring of the adequacy of oxygenation specific to the brain (allows practitioner to detect decreases in CBF in relation to CMRO2).
Cerebral Oximetry
What does Cerebral Oximetry measure?
Near infrared spectroscopy (NIRS)
-Goal is to maintain NIRS at a minimum of 75% of baseline reading
What Law is used in Cerebral Oximetry monitoring?
Beer Lambert Law
If NIRS level is low, what does that indicate?
Cerebral Hypoxia
What are some treatments for a low NIRS score (cerebral hypoxia)?
- Increase BP/CO
- Increase FiO2
- Increase PaCO2 (hypoventilate to decrease vasodilation)
- Transfuse PRBCs
Measures the O2 supply vs demand within a region of the brain
Cerebral Oximetry
What specific types of surgeries is Cerebral Oximetry typically used during?
- Neonatalogy
- Cardiac Surgery
- Cardiac endarterectomy
A non-invasive monitor of CBF within large arteries of the brain (middle cerebral artery) via a probe positioned on the temporal bone that emits ultrasound waves.
Transcranial Doppler
Does a transcranial doppler determine the actual CBF?
No, it determines flow direction, velocity, acceleration time, and intensity of pulsatile flow.
Flow velocity > expected on transcranial doppler indicates what?
- Stenosis
- Emboli
- Spasm
What is transcranial doppler monitoring used for?
Microemboli detection and cerebral integrity during surgery.
Accuracy of transcranial doppler monitoring is limited by ______.
Thick temporal bones.
A type of CBF monitoring that estimates the degree of global O2 extraction by the brain.
Jugular Bulb Venous Oxygenation (SjVO2)
What are some indications for Jugular Bulb Venous Oxygenation (SjVO2) monitoring of CBF?
- Evaluate cerebral ischemia and guide hyperventilation therapy
- Fiberoptic catheter inserted through IJ into jugular bulb
- Estimate global CBF & CMRO2 balance
SjVO2 between _________ with a ________ ICP indicate positive outcomes for TBI.
55-75%; normal ICP
SjVO2 > 75% or <55% with an elevated ICP = ?
Poor Outcomes
What are causes of SjVO2 < 55%?
- Decreased O2 Supply
- Increased O2 Demand
What are some causes of decreased O2 supply and what are the correct treatments?
Causes:
1. Anemia (transfuse)
2. decreased CBF (maintain CPP)
3. Hypoxemia (correct this)
What are some causes of increased O2 supply and what are the correct treatments?
Causes:
1. Agitation (sedation)
2. Pain (analgesia)
3. Fever/sepsis (control temp)
4. Seizure (anticonvulsants)
