Total Spinal Block
A total spinal block is a rare and very serious complication that
occurs after excessive cephalad spread of the local anesthetic. It can occur during
single-shot spinal anesthesia or as a result of inadvertent intrathecal spread of
epidural medication after unintentional dural puncture or catheter migration.[217]
Subdural spread of the local anesthetic can also cause a high block[218]
characterized by a high sensory level, sacral sparing, and incomplete or absent motor
block. Single-shot spinal anesthesia after a failed spinal or patchy epidural may
also precipitate a total spinal.[219]
There are
several possible mechanisms for high spinal blocks when a spinal is attempted after
failed epidurals. Expansion of the epidural space may compress the spinal canal
and encourage cephalad spread of intrathecal drugs. Rapid transfer of local anesthetic
from the epidural space across the dural hole may also occur. In addition, sufficient
local anesthetic may be present in the nerve roots to decrease the dose requirements
of subsequent spinal anesthesia.[220]
In the case
of a nonemergency cesarean section when a patchy block is present, several options
are possible without resorting to a single-shot spinal. An epidural catheter can
be relocated and the drug titrated through the catheter. Alternatively, a CSE can
be placed in which a fraction of the usual spinal dose can be administered; again,
the catheter can be used to
titrate to a desired level. Other options include repeating a spinal after waiting
for the original block to resolve or converting to a general anesthetic.
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