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.