What is the role of somatosensory evoked potentials (SEPs) in the workup of epidural sensory block?

Updated: Oct 25, 2019
  • Author: Andrew B Evans, MD; Chief Editor: Selim R Benbadis, MD  more...
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The existence of differential sensory block during epidural analgesia has been confirmed by some authors and disputed by others. Zaric et al evaluated epidural sensory block by thermal stimulation, laser stimulation, and recording of the SEP and found that recording of SEP did not demonstrate significant difference between responses from the sites with the most superficial sensory block and those from the sites with the most intense sensory block.

In this study, the zone of anesthesia was smaller than the zone of any other investigated variable. [79] The cranial spread of analgesia and motor block was lower than that of laser-assessed block. Partial block of laser perception and thermal perception lasted longer than analgesia and motor block. No consistent segmental or temporal differences were found between the thermal test and laser methods.

During epidural block, prolongation of latencies and reduction in amplitudes of SEP produced at the most cranial analgesic dermatome did not differ significantly from those produced at the anesthetic dermatome. [79] No differential block of small nerve fibers was found during epidural analgesia by thermal test and argon laser stimulation.

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