2a. EPs Monitoring Flashcards
What is the purpose of evoked potential monitoring?
detects injury to the spinal cord and measures neuronal function
what 4 things may affect EP monitoring?
hypotension
anesthetic drugs i.e. volatile agents
hypothermia
spinal cord retraction
latency
time of administration of stimulus to peak response (time necessary for the evoked response to be measured in the brain)
amplitude
magnitude of the peak response/intensity of the evoked response
how do VAs and N2O affect latency and amplitude of EPs?
↓ amplitude and ↑ latency
which is more sensitive to depressant effects of anesthetics between motor (MEP) and somatosensory (SSEP) EPs?
MEPs
what MAC may be used without altering signal quality of EPs?
MAC ≤ 0.5
effect of propofol on EP monitoring?
dampening of evoked potential response
effect of opioids and benozos on EP monitoring?
no interference
what type of injury can occur from transcranial stimulation and how is this prevented?
facial muscle activation causes pt to bite down with significant force and cause injury to tongue, lips, cheeks, teeth etc. Therefore a soft bite block should be inserted to avoid injury.
What is the purpose of the Hunt-Hess Scale
determines severity of a patient’s subarachnoid hemorrhage (a high grade corresponds to a higher severity)
what hunt-hess scale score corresponds to an asymptomatic patient?
1
A patient with SAH will require intubation if his Hunt-Hess score is (Select 2)
4 and 5
NIRS
Near Infrared Spectroscopy used to assess cerebral O2 Sat
* Used when cerebral perfusion could be compromised
NIRS goal parameter
maintain the NIRS value at a minimum of 75% of the baseline reading
Normal ICP
5 to 15 mm Hg in adults
intracranial hypertension values
20 to 25 mm H
gold standard for ICP monitoring
intraventricular catheter (it allows for drainage of CSF to lower ICP)
what is the most frequent complication of ICP monitoring
Infection
ICP should be monitored in patients with a normal CT scan with two or more of the following criteria…
- age older than 40
- unilateral or bilateral motor posturing
- systolic blood pressure (SBP) less than 90 mm Hg
Cushing’s triad
- systemic hypertension
- bradycardia
- irregular respiratory pattern
who else should undergo ICP monitoring?
- patients with severe traumatic brain injury (TBI)
- a Glasgow coma scale (GCS) sum score below 9
- an abnormal CT scan
What change in EPs is suggestive of the possibility of cerebral ischemia?
A 50% decrease in amplitude or a 10% increase in latency
effect of ketamine and etomidate on EP monitoring?
increases amplitude
no effect on latency
