Skin conductance responses during spinal analgesia

Area of Science:

• Anesthesiology
• Neuroscience
• Physiology

Background:

• Skin conductance responses (SCR), also known as the sympatho-galvanic reflex, reflect sympathetic nervous system activity.
• Spinal analgesia is commonly used for surgical procedures, but its effects on sympathetic function require further investigation.

Purpose of the Study:

• To investigate the impact of spinal analgesia on skin conductance responses (SCR) in patients undergoing transurethral surgery.
• To compare the blockade of preganglionic sympathetic B-fibers versus A-fibers during spinal analgesia.

Main Methods:

• Measured SCR before and during spinal analgesia in 17 patients using electrical stimulation and other stimuli.
• Recorded SCR from various body sites including the hand, T5, T9, T12-L1, and foot.
• Assessed spinal analgesia levels and compared SCR changes with blood pressure variations.

Main Results:

• SCR was markedly depressed in the foot and lower thoracic regions, with less effect on the hand.
• Sympathetic activity reappeared earlier than the regression of analgesia or motor blockade.
• No consistent correlation was observed between blood pressure changes and SCR changes.

Conclusions:

• Preganglionic sympathetic B-fibers are more resistant to blockade by spinal analgesia than A-fibers.
• The duration of sympathetic blockade is significantly shorter than that of analgesia and motor blockade.
• Sympathetic blockade during spinal analgesia may be less extensive than previously reported.