Evoked Potentials Flashcards
What are evoked potentials?
Electrical potentials that are measured in response to some
type of stimulus. The purpose is to improve or preserve
neurologic structures that are at risk, and to also prevent
damage that is irreversible.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 329.
With regards to evoked potentials, what are three
general rules to help guide a nurse anesthetist?
- Lipophilic agents that interfere with neuronal membrane
conduction also interfere with subcortical conduction. 2. At
equipotent doses to inhalational agents, IV agents will affect
evoked potentials to a lesser degree. 3. Anesthetic agents that
interfere with the ECG will also affect evoked potentials.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
What is the purpose of SSEP’s?
SSEP’s monitor various neural structures along the central and
peripheral somatosensory pathways.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
How is the stimulation for SSEP’s created?
Through electrical stimulation of peripheral nerves
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
Do SSEP’s provide real-time electrical waveforms?
No. They are processed as an average, using electrical filters
in the removal of background noise. The interpretation of the
compound action potential depends on the distance to the
recording electrodes and the site of the stimulus.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
In what types of surgeries are SSEP’s beneficial?
Since changes in SSEP’s are sensitive to cerebral ischemia,
they have many uses in vascular surgery, including carotid
endarterectomy, and cerebral aneurysm surgery. SSEP’s can
also indicate high risk for neurologic injury during crossclamping
of the aorta.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
What anesthetic agents do not produce a change in
latency or amplitude in regards to SSEP’s?
Ketamine, etomidate, and opiates.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330
If SSEP’s are monitored alone, can a paralytic agent
be used?
Yes. If SSEP’s are being monitored, the use of a paralytic is
accepted, and potentials are able to be measured. Motor
responses will not be elicited, however.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
How are the lower extremities monitored during
SSEP’s?
Through the stimulation of the posterior tibial nerve, which is
located between the Achilles tendon and medial malleolus of
the ankle
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
Where is the stimulus placed to monitor SSEP’s in
the upper extremity?
At the location of the median nerve which can be found
between the tendons of the flexor carpi radialis and the palmaris
longus.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
Describe how VEPs are performed
The patient is presented a visual stimulus for a select number of
times, then the cerebral responses are dispayed after being
amplified and averaged on a computer. There are two types of
VEPs: patterned and unpatterned. Patterned tests are used on
awake patients.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 332.
What is the purpose of Visual Evoked Potentials
(VEPs)?
They are used to monitor function of the visual pathway. This is
composed of the retina, extending to the occipital cortex,
including everything that exists in between, including the optic
chiasm and the optic nerve.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 332.
How are VEPs performed on anesthetised patients?
A stroboscopic flash stimulus is used, with recording electrodes
placed on the patient’s scalp. A flash VEP is derived from a
flash that already has a determined strength, of certain light
intensity against a dim background.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 332
What is the purpose of Brainstem Auditory Evoked
Potentials (BAEP’s)?
BAEP’s are used in the monitoring of the entire auditory
pathway, which allows for the monitoring of basic brainstem
function. They are clinically useful because they are extremely
resistant to abberation unless there is actual structural
pathology in the brainstem.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 330.
What is the stimulus used in the monitoring of
BAEPs?
A standard broadband repeating click that is delivered through
an earphone that is placed in the auditory canal.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 916.
