REGIONAL ANESTHESIA OF THE EXTREMITIES
Upper Extremity
Orthopedic procedures in the arm may be performed under a variety
of brachial plexus blocks, with intravenous regional anesthesia, or by using combinations
of individual nerve blocks in the arm (see Chapter
44
). The selection of a particular technique depends on the need for a
tourniquet and on the site of anticipated surgery.
The deep structures of the shoulder are largely innervated by
the C5 and C6 dermatomes. This explains why shoulder surgery can be performed under
an interscalene block alone.[151]
[152]
Skin infiltration may be necessary to anesthetize the contribution of the intercostobrachial
nerve for the posterior portal for shoulder arthroscopy or if the skin incision extends
toward the axilla.
Open shoulder surgery or arthroscopy performed in the sitting
position under interscalene block may be complicated by episodes of bradycardia or
hypotension, or both, in up to 20% of cases.[153]
These are believed to be vasovagal reactions that are best prevented by fluid loading
and pretreatment with intravenous atropine or β-blockers.[154]
Prophylactic use of β-blockers has been compared with prophylactic glycopyrrolate
administration. Prophylactic β-blockade, but not prophylactic glycopyrrolate,
reduced the frequency of hypotensive bradycardic events.[155]
[156]
Regardless of the choice to use hydration
or pharmacologic prophylaxis, the anesthesiologist must be extremely vigilant and
intervene early to prevent progression to asystole. Treatment may include use of
ephedrine, atropine, and glycopyrrolate and positioning the patient supine until
stable. Excessive absorption of fluid may also occur especially in long cases.[157]
Elbow surgery can be performed by interscalene or axillary blocks
[158]
or by a combination of both.[159]
Alkalinization of local anesthetics has been shown to more effectively anesthetize
the C8-T1 dermatomes during interscalene blocks.[160]
Intercostobrachial blocks (T1-2) in the axilla may be necessary as a supplement
to axillary blocks if medial incisions are performed in the upper arm.
Hand and forearm surgery can be performed with the use of any
of the previous techniques. Axillary blocks may be preferable for surgery of the
medial aspect of the hand and forearm (C7-8, T1) because this area is sometimes incompletely
blocked by the interscalene approach. The coracoid block is also effective for surgery
of the elbow, forearm, or hand. This infraclavicular block has prominent bony landmarks,
making it easier to perform with less likelihood of pneumothorax compared with other
infraclavicular approaches to the brachial plexus. The site is also ideal for securing
a catheter to the anterior chest wall.[161]
[162]
Continuous axillary blocks may also be used for prolonged cases. Intravenous regional
anesthesia is most applicable for shorter cases.
Peripheral nerve blocks at the wrist or hand can be performed
with a long-acting anesthetic such as bupivacaine or ropivacaine to provide postoperative
pain relief and facilitate discharge after ambulatory surgery.
