Parascalene Approach
The parascalene approach[221]
aims at penetrating the interscalene space at a distance from the apical pleura,
[222]
the great vessels or the neck, the vagus and
phrenic nerves, the stellate ganglion, and the spinal canal. The patient is placed
supine, with the arm extended along the body and the head turned to the contralateral
side. A pillow is slipped under the shoulders to extend the neck, stretching and
bringing the components of the brachial plexus to a more superficial position. The
landmarks are the clavicle, the posterior edge of the sternocleidomastoid
*Supraclavicular
and coracoid approaches to the brachial plexus, femoral nerve, and fascia iliaca
compartment block; proximal approaches to the sciatic nerve.
muscle, and Chassaignac's tubercle (on the transverse process of C6). The site of
puncture is at the junction of the upper two thirds with the lower third of the line
joining Chassaignac's tubercle and the midpoint of the clavicle ( Fig.
45-7
). The needle is inserted posteriorly at right angles to the skin
until twitches are elicited in the upper limb. The depth at which the plexus is
correlated with the patient's age and weight ranges from 7 mm (±3 mm) in neonates
to 25 mm (±6 mm) in adolescents weighing more than 80 kg ( Fig.
45-8
). Usual volumes of local anesthetics for single-shot procedures are
provided in Table 45-11
.
When mandatory for prolonged pain relief, a catheter
Figure 45-6
Coracoid approaches to the brachial plexus: paracoracoid
approach (A) and midclavicular approach (B), indicating the coracoid process of the
scapula (1) and the midpoint of the clavicle (2).
Figure 45-7
Parascalene approach to the brachial plexus, showing
the skin projection of Chassaignac's tubercle (1) and the midpoint of the clavicle
(2).
can be left in place, and repeat injections, continuous infusions, and on-demand
top-up doses can be made (see Table
45-12
). The success rate of this block is high.[221]
[223]
The anesthetized area is supplied by the
brachial
plexus and, in more than 50% of cases, supplied by the lower branches of the cervical
plexus. Proximal branches of the brachial plexus (i.e., those supplying the shoulder
and the arm) are blocked earlier and sometimes more profoundly than the distal branches.
Complications, including Horner's syndrome, are unlikely with this procedure, and
only a very faulty technique ("... as suggested by the
Figure 45-8
The distance from the skin to the plexus or nerve for
the most commonly used techniques of peripheral nerve blocks correlates with the
patient's age.
marked resistance to injection, by the agonizing pain experienced by the patient")
can result in adverse effects.[224]
