If a regional anesthetic is selected, what level of anesthesia is required?

If a regional anesthetic is selected, what level of anes-thesia is required?

The level of anesthesia required is dependent on the anatomy and sensory innervation of the involved structures. The structures that need to be blocked are the blad-der, prostate, penis, and urethra. The dome of the bladder receives its sensory innervation via T₁₁–L₂, while the neck of the bladder is via S₂–S₄. The prostate receives its sensory innervation via T₁₁–L₂ and S₂–S₄. Finally, a sensory block of the penis and scrotum will require blocking S₂–S₄.

Based upon this anatomy, a block to the level of T₁₀ is usually sufficient for a TURP. If a lower level is attained, the stretch of the bladder from the irrigating fluids will not be well tolerated. Since a block at the level of S₄ is also required, a spinal is preferred over an epidural anesthetic, since there is often an incomplete block of the sacral nerve roots.