regional question

[amyl]

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plank et al:
for some reason it is stuck in my mind that the differential blockade of a peripheral nerve block is sympathetics and cold temp, than sensory and all temp, then proprioception, then motor. is this right? i have looked everywhere for a reference explaining this with no luck..any ideas?

 

[Planktonmd]

plank et al:
for some reason it is stuck in my mind that the differential blockade of a peripheral nerve block is sympathetics and cold temp, than sensory and all temp, then proprioception, then motor. is this right? i have looked everywhere for a reference explaining this with no luck..any ideas?

OK,
Let's think about the different types of sensory nerve fibers and remember that thinner nonmyelinated fibers go first and thicker myelinated fibers go last:
Fibers C get anesthetized first because they are the thinest and they are nonmyelinated, this translates into sympathetic and sensation to warmth anesthesia.
Then A delta fibers go which means Cold , Pain and pressure.
Then A beta Fibers go Which includes all the cutaneous mechano receptors (Deep touch, sustained pressure and texture...).
Then 1B fibers go which means Proprioception.
Then 1A Fibers go (Muscle Stretch)
And last but not least Alpha and Gama fibers go: Motor block.
So the sequence would be:
Sympathetic ----> Warmth ----> Cold ----> pain ----> pressure ----> deep touch and sustained pressure ----> proprioception ----> muscle stretch ----> Motor.
and the reversal happens in a reversed sequence.
All this is theoretic of course and things could happen simultaneously.