Underestimation of visceral level in spinal and epidural anesthesia and overemphasis on somatic level deserves greater attention. Assessing the visceral level (the blocking of internal organ pain) in spinal anesthesia requires targeting dermatomes higher than the skin incision. T1 to L2: Sympathetic fibers S2 to S4: Parasympathetic fibers The addition of opioids, clonidine, dexmedetomidine, etc., helps achieve more effective visceral blockade.
To reliably block visceral discomfort and nausea, a sensory block of T₄ to T₆ is typically required, compared to a T₁₀ block for somatic (skin) pain. Why skin sensation alone may not be enough Because visceral nerve fibers (unmyelinated C fibers) are deeply distributed and relatively resistant to local anesthetics, assessing skin sensation alone may not accurately reflect the adequacy of visceral blockade. Clinical assessment of visceral block…
