Block-dependent sedation during epidural anaesthesia is associated with delayed brainstem conduction.

Area of Science:

• Anesthesiology
• Neuroscience
• Auditory Evoked Potentials

Background:

• Neuraxial anesthesia offers sedation and reduces anesthetic requirements.
• Spinal cord anesthesia may alter arousal by diminishing afferent sensory signals.
• Epidural anesthesia's sedative effects might stem from sensory deafferentation impacting brainstem function.

Purpose of the Study:

• To investigate if epidural anesthesia-induced sedation is linked to sensory deafferentation.
• To assess potential impairments in brainstem transmission during epidural anesthesia.
• To evaluate changes in brainstem auditory evoked potentials (BAEP) as a measure of reticular function.

Main Methods:

• Epidural anesthesia induced with 2-chloroprocaine 2%.
• Assessed hemodynamic, respiratory, sensory block, and sedation levels (VRS, OAA/S, BIS).
• Evaluated brainstem auditory evoked potentials (BAEP) and correlated findings with sedation and block levels.

Main Results:

• Sensory block level significantly predicted sedation measures (VRS, OAA/S, BIS).
• Bispectral index (BIS) also predicted VRS and OAA/S scores.
• Latency of BAEP wave III correlated with sedation and sensory block levels, indicating altered brainstem transmission.

Conclusions:

• Sedation during epidural anesthesia is dependent on the sensory block level.
• Epidural anesthesia causes measurable changes in BAEP, suggesting impaired brainstem function.
• Sensory deafferentation may reduce central nervous system alertness via brainstem neural activity alterations.