Sun28November0333PM 36

Are the following statements true or false regarding evoked potentials for intraoperative spinal cord monitoring during spinal surgery?

True / False

Propofol should be avoided when somatosensory evoked potentials are monitored Correct

Muscle relaxation prevents interpretation of somatosensory evoked potentials (SSEPs) Incorrect answer selected

Volatile anaesthetic agents significantly degrade motor evoked potentials (MEPs) Correct

Somatosensory evoked potentials can be used to monitor the integrity of the dorsal columns during spinal surgery Correct

Opioids significantly degrade both somatosensory and motor evoked potentials and therefore should be avoided Correct

Explanation

Motor and somatosensory evoked potentials (SSEPs) are frequently used for monitoring of cord function during spinal surgery and are affected by many common anaesthetic agents. Volatile anaesthetic agents will cause a slight reduction in SSEPs (sevoflurane less than isoflurane), but will significantly degrade motor evoked potentials (MEPs) to the point that they may be un-interpretable.

Propofol does also have a minor effect on SSEPs but provided a steady state is maintained, the traces are usually well preserved.

SSEPs monitor ascending sensory pathways, sensing a response to a peripheral stimulus whereas MEPs trigger descending motor pathways, with the measured stimulus being a motor twitch. Therefore muscle relaxation will make MEPs difficult to interpret.

Opioids have a small, but minimal effect on both, and are required as part of a balanced anaesthetic technique.

Reference:

Open Anesthesia. ABA:Evoked potentials - anesthetic effects.

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Average score: 75.31%

Times answered: 243