Miscellaneous Monitors Flashcards
What Hz and time interval is TOF at?
4 twitches at 2hz and 0.5 second intervals for 2 seconds
When <50% of receptors are blocked, what will be seen on the TOF?
Normal TOF, 4 equal twitches.
When <75% of receptors are blocked, what will be seen on the TOF?
100% T1
75% T4
When are T4 twitches lost?
When 80% of receptors are blocked
When are T1 twitches lost?
> 90% of twitches blocked
When are T2 and T3 twitches lost?
When 20 and 10 % of twitchers are occupied
What is tetanus? How long? How many Hz?
Continuous for 5 seconds at 50Hz
Is tetany more or less sensitive than TOF?
more sensitive at assessing recovery
How does tetany affect TOF?
Wont be accurate for up to 6 minutes
Is it easier to detect fade with DBS or TOF?
DBS
What is DBS? How long? How many Hz?
2 short bursts of 50 Hz, 0.75 seconds apart
**very painful
What is the best method of assessing a deep neuromuscular blockade ?
Post tetanic count
What will be seen after 6-10 post tetanic twitches?
T1 will return shortly
*fewer twitches means return of T1 is further away
Fade occurs when the T4/T1 ratio less than: ?
1.0
What is the advantage of a double-burst stimulation?
Easier to detect fade
What is post-tetanic potentiation? When is it most helpful?
Occurs when the twitch response is stronger after a tetanic stimulus than it was at baseline
When no twitches are seen
What does cerebral oximetry monitor?
Venous oxygen saturation
Does cerebral oximetry monitor global or regional oxygenation?
Regional
What is the ration of cerebral blood volume?
1 part arterial
3 part venous
Can cerebral O2 monitor pulsatile blood flow?
No
What percentage of a change signals a reduction in cerebral O2?
> 25%
What can interfere with cerebral O2?
Scalp hypoxia can interfere and may falsely suggest brain ischemia
How many light sensors in cerebral O2?
2
What is the order from highest frequency to lowest frequency of EEG?
Highest
1. Beta
2. Alpha
3. Theta
4. Delta
Lowest
Which brain waves have high frequency and low voltage? Associated with awake mental stimulation and light anesthesia?
Beta
Which brain waves have the second high frequency? Associated with awake but restful sleep?
Alpha
Which brain waves have the third highest frequency? Associated with general anesthesia and children during normal sleep
Theta
Which brain waves are associated with general anesthesia, deep sleep, and brain injury?
Burst suppression
What happens to beta waves on induction of general anesthesia?
They increase
**also increases with light anesthesia
What two brain waves are associated with general anesthesia ?
Theta and Delta
What MAC provides complete suppression?
1.5-2.0 MAC
How does nitrous affect beta wave activity?
Increases it
How does sevo affect EEG activity?
Can increase epileptiform
How does etomidate affect EEG?
Can cause myoclonus but is not epileptiform
How does ketamine affect EEG?
May increase high frequency cortical activity and the patient may be deeper than suggested
What may hypothermia cause?
Burst suppression - especially during cardiopulmonary bypass
What does unilateral burst suppression suggest ?
Cerebral ischemia
What may new delta waves signal during anesthetic maintenance?
Brain is at risk for ischemia
What may mimic cerebral ischemia?
deep aesthesia, hypothermia, hypocarbia
When is EEG useful?
Carotid’s
Cerebral aneurysm
AV malformation
CPB
Deliberate hypotension
Barbiturate coma
Epilepsy
Coma and death
