Lower Extremity
Most lower extremity surgery can be performed with spinal, epidural,
or combined spinal-epidural anesthesia with various degrees of sedation (including
use of a laryngeal mask airway). Alternatively, nerve blocks can be used alone or
in combination with general anesthesia. Knee arthroscopy is usually performed on
an outpatient basis with spinal anesthesia using pencil-point needles,[163]
with combined spinal-epidural anesthesia,[164]
or
with femoral block with an intra-articular local anesthetic. Transient neurologic
symptoms remain an unresolved problem after outpatient knee arthroscopy under spinal
anesthesia.[165]
It has mostly been linked with
the use of lidocaine, lithotomy position, and arthroscopic knee surgery.[166]
Alternative agents include isobaric mepivacaine or low doses of bupivacaine, which
have been reported to have a lower incidence of transient neurologic symptoms.[166]
[167]
Surgery of the forefoot can be performed satisfactorily under
ankle or midtarsal block[168]
or by anesthetizing
the branches of the sciatic and femoral nerves proximally.
The common peroneal nerve can be anesthetized as it courses superficially below the
head of the fibula, or both branches of the sciatic nerve can be blocked in the popliteal
fossa (i.e., popliteal fossa block). The popliteal fossa block performed for foot
and ankle surgery greatly reduces the need for postoperative opioid analgesics and
has a very low incidence of complications.[169]
In any surgery involving the medial aspect of the foot, the saphenous branch of
the femoral nerve must be anesthetized at the level of the ankle or perhaps higher
up (e.g., infero-medial to the knee). These techniques preclude the use of thigh
tourniquets. For ankle blocks, Esmarch bandages or tourniquets applied immediately
above the ankle enable at least 2 hours of surgery to be performed without tourniquet
pain.[168]
[170]
Ankle surgery cannot be reliably performed using an ankle block.
Epidural anesthesia for ankle surgery is satisfactory, but onset of analgesia may
be delayed for up to 30 minutes until complete anesthesia of the L5-S1 nerve roots
develops.[171]
[172]
[173]
The addition of an epidural narcotic, epinephrine,
clonidine, or bicarbonate[172]
[173]
to the local anesthetic may also enhance the quality of the anesthesia. A spinal
or combined spinal-epidural technique provides reliable and rapid onset of anesthesia.
Caudal anesthesia is an option in patients with prior lumbar spinal surgery, as
is spinal anesthesia. Sciatic blocks in combination with femoral or saphenous nerve
blocks are suitable for ankle surgery. The deep structures of the ankle are all
innervated by branches of the sciatic nerve, which explains why sciatic or popliteal
blocks alone are usually sufficient to reduce ankle fractures and provide excellent
postoperative analgesia after ankle surgery.[174]
Femoral or sciatic blocks, or both, may also be used for surgery
of the thigh or the leg.[175]
The blocks required
depend on the site of the surgery and the necessity for a tourniquet. Three-in-one
blocks (i.e., femoral plexus block) may be used for knee arthroscopy provided that
prolonged tourniquet times can be avoided. A number of sciatic block techniques
are perfectly adequate for surgery below the knee if tourniquets are not used.
Femoral nerve blocks can be performed preoperatively or postoperatively
for analgesia. They are particularly effective in providing analgesia for hip or
femur fractures[150]
[151]
and for pain after knee surgery.[118]
[119]
[120]
[121]
[176]
