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.