|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Indications for supraclavicular block are operations on the elbow, forearm, and hand. Blockade occurs at the distal trunk-proximal division level. At this point, the brachial plexus is compact and a small volume of solution produces rapid onset of reliable blockade of the brachial plexus. An additional advantage is that the block can also be performed with the patient's arm in any position.
Reliable supraclavicular blockade requires elicitation of a paresthesia or motor response. The classic block may be somewhat difficult to describe and to teach. Observation of an experienced anesthesiologist is perhaps the best way to learn the technique. A proposed modification of the technique, the so-called plumb-bob approach, may decrease complications and may simplify the concept of this block. [17]
Several anatomic points are important in the performance of the supraclavicular approach. The three trunks are clustered vertically over the first rib cephaloposterior to the subclavian artery, which can often be palpated in a slender, relaxed patient. The neurovascular bundle lies inferior to the clavicle at about its midpoint. The first rib acts as a medial barrier to the needle's reaching the pleural
Figure 44-4
A, Supraclavicular block.
The needle is systematically walked anteriorly and posteriorly along the rib until
the plexus is located. B, The three trunks are compactly
arranged at the level of the first rib (see Plate
3
in the color atlas of this volume).
The patient is placed in a supine position, with the head turned away from the side to be blocked. The arm to be anesthetized should be adducted, and the hand should be extended along the side toward the ipsilateral knee as far as possible. In the classic technique, the midpoint of the clavicle should be identified and marked. The posterior border of the sternocleidomastoid can be easily palpated when the patient raises the head slightly. The palpating fingers can then roll over the belly of the anterior scalene muscle into the interscalene groove, where a mark should be made approximately 1.5 to 2.0 cm posterior to the midpoint of the clavicle. Palpation of the subclavian artery at this site confirms the landmark.
After appropriate preparation and injection of a skin wheal, the anesthesiologist stands at the side of the patient facing the patient's head. A 22-gauge, 4-cm needle is directed in a caudad, slightly medial, and posterior direction until a paresthesia or motor response is elicited or the first rib is encountered. If a syringe is attached, this orientation causes the needle shaft and syringe to lie almost parallel to a line joining the skin entry and the patient's ear. If the first rib is encountered without elicitation of a paresthesia, the needle can be systematically walked anteriorly and posteriorly along the rib until the plexus or the subclavian artery is located ( Fig. 44-4 ; see Plate 3 in the color atlas of this volume). Location of the artery provides a useful landmark; the needle can be withdrawn and reinserted in a more posterolateral direction that usually results in a paresthesia or motor response. On localization of the brachial plexus,
The rib usually is contacted at a needle depth of 3 to 4 cm; however, in an obese patient or in the presence of tissue distortion resulting from hematoma or injection of solution, the depth may exceed the needle length. Nonetheless, before the needle is advanced farther, gentle probing in the anterior and posterior directions should be done at the 2- to 3-cm depth if paresthesias are not obtained. Multiple injections may improve the quality or may shorten the onset of blockade.
The modified, plumb-bob approach uses similar patient positioning, although the needle entry site is at the point at which the lateral border of the sternocleidomastoid muscle inserts into the clavicle. After preparation and injection of a skin wheal, a 22-gauge, 4-cm needle is inserted
Figure 44-5
Supraclavicular block. The needle is inserted while
mimicking a plumb-bob suspended over the needle entry site.
The prevalence of pneumothorax after supraclavicular block is 0.5% to 6% and diminishes with experience. The onset of symptoms is usually delayed and may take up to 24 hours. Routine chest radiography after the block is not justified. The supraclavicular approach is best avoided when the patient is uncooperative or cannot tolerate any degree of respiratory compromise because of underlying disease. Other complications include frequent phrenic nerve block (40% to 60%), Horner's syndrome, and neuropathy. The presence of phrenic or cervical sympathetic nerve block usually requires only reassurance. Although nerve damage can occur, it is uncommon and usually is self-limited.
|
|
|
|
|
|
|
|
|
|
|
|
|
