APEX: MISC MONITORS Flashcards
Best describes the CEREBRAL OXIMETRY
A greater than 25% change from baseline suggests a REDUCTION in CEREBRAL OXYGENATION
Cerebral oximetry is a
noninvasive technique that utilizes near infrared spectroscopy NIRS to measure regional (NOT GLOBAL) cerebral oxygenation
What is cerebral oximetry based on
The principle that decrease cerebral oxygen delivery lead to increase cerebral oxygen extraction and decrease venous hgb saturation
Cerebral oximetry sensor is placed where
Patient’s scale over the frontral lobe
Cerebral oximetry contains a light emiting
Diode and 2 light sensor: surface photodetector and a DEEP photodetector
The infrared light in cerebral oximetry follos
Elliptical pathway from the emitting diode –>scalp –> skull –> brain–> skull –> scalp–> Photodetectors
Cerebral oximetry relies on the facts that
Cerebral blood volume is 1 part arterial and 3 parts venous. 75% of the blood in the brain is on the venous side of circulation
Can NIRS detect pulsatile blood flow?
no
Since NIRS does not have ability to detect pulsatile BF, it is primarily a measure of what?
Venous oxyhemoglobin saturation and Oxygen extraction.
Can contaminate the signal of NIRS
Scalp hypoxia , may falsely interpret it as brain ischemia
EEG waves from high to low frequency (BAT-D)
Beta
Alpha
Theta
Delta
EEG measures the difference between
Electrical potentials in multiple regions of the brain.
EEG Provides information about electrical activity of the
Cerebral cortex
EEG provide little information about the
Subcortical structures, spinal cord and the cranial and peripheral nerves.
High Frequency low voltage waves
beta waves
Beta waves associated with
Awake mental stimulation and LIGHT ANESTHESIA
Beta frequencies
13-30 cycles/sec
Alpha waves associated with
Awake but RESTFUL STATE WITH EYES CLOSED.
Alpha frequencies
8-12 cycles/second
Theta waves frequencies
4-7 cycles/second
Theta wave associated with
GA
Waves associated with children during normal sleep
Theta waves
Delta waves associated with
GA, DEEP SLEEP, brain ischemia or injury
Burst suppression is associated with
GA, hypothermia, CBP, Cerebral ischemia (especially if its UNILATERAL burst suppression)
Isoelectricity is
absence of electrical activity
Associated with very deep anesthesia and death.
How brain waves change during anesthesia? Induction
Increased beta wave activity
How brain waves change during anesthesia? light anesthesia
Increased beta wave activity
Waves the predominate during GA
Theta and beta
Produces burst suppresion
Deep anesthesia
At what MAC does GA cause complete suppresion or isoelectricity?
1.5-2.0 MAC
Nitrous and EEG
When administered alone, Increases beta wave activity
Can increase EPILEPTIFORM EEG activity
Sevoflurane
Can cause myoclonus
Etomidate
Can cause myoclonus but this is not associated with epeleptiform EEG activity
Etomidate
Ketamine on EEG
Increase high frequency cortical activity and may confuse EEG interpretation - the patient may be deeper than the EEG SUGGESTS>
When does burst suppresion occur with temp
hypothermia, especially with CPB
This kind of burst suppresion suggest cerebral ischemia
Unilateral burst suppression .
EEG usefulness for infarction?
EEG provides a sensitive measure of brain tissue at risk of infarction
The brain requires an
Adequate perfusion pressure to provide a steady supply of oxygen and glucose.
In the absence of these substrates the brain is unable to maintain its electrical function
Oxygen
Glucose.
You are seeing the development of new delta waves during anesthetic maintenance may signify
that brain is at risk for ISCHEMIA
Circumstance that mimic cerebral ischemia:
Deep anesthesia
Hypothermia
Hypocarbia
EEG monitoring useful during the following neck procedure:
Carotid endarterctomy
EEG monitoring useful during these brain surgeries
AV malformations
Cerebral aneurysm
Epilepsy dx and tx