Supraclavicular Nerve Block: Ultrasound-Guided Technique (Quick Review)

Pre-Procedure

INDICATIONS Anesthesia for surgery of the arm, forearm and hand Analgesia for the arm, forearm and hand Post-surgical Post-traumatic Complex regional pain syndrome Post-amputation pain Vascular disease (ischemic limb pain) Tumor-related pain Vasodilation for some upper extremity procedures Vascular flaps Reimplantation of forearm, hand, digits CONTRAINDICATIONS Absolute contraindications Patient refusal Allergy to local anesthetics Local infection at or near the needle insertion site Relative contraindications Uncooperative patient Severe respiratory compromise The need for bilateral upper extremity anesthesia (and risk of bilateral phrenic nerve blockade or pneumothoraces) Coagulopathy or medical anticoagulation Traumatic nerve injury in the upper extremity or neck Preexisting neurodeficits in the distribution of the block Previous surgery in the neck that may distort brachial plexus anatomy EQUIPMENT Appropriate resuscitation equipment, including oxygen, suction, emergency airway equipment, and resuscitation medications Local anesthetic, typically: 1 to 1.5% lidocaine 1 to 1.5% mepivacaine 0.25 to 0.5% bupivacaine 2% chloroprocaine Sterile gloves and mask Sterile fenestrated drape or sterile towels for draping Sterile prep solution One 30-mL syringe A 5-mL sterile syringe and small gauge (25- or 30-gauge) needle for local anesthetic infiltration of the skin IV extension tubing 3-way stopcock Peripheral nerve stimulator and ECG electrode 1- to 1.5-inch, 25-gauge, short-bevel insulated nerve stimulating needle Ultrasound machine and transducer Sterile ultrasound gel ANATOMY The anterior scalene muscle originates from the anterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebra and insert onto the anterior aspect of the first rib. At its insertion, the anterior scalene muscle separates two important vascular structures, the subclavian artery and vein, respectively, located posterior and anterior to the muscle. The brachial plexus lies cephaloposterior to the subclavian artery resting on the anterior belly of the middle scalene muscle. The subclavian artery emerges to the right from the brachiocephalic trunk and from the left of the aortic arch. The subclavian artery is a basic reference for US-guided brachial plexus anesthesia. It, in turn, gives rise to the vertebral artery, which penetrates the intertransverse foramina (from the sixth cervical vertebra) located anterior to the path of the spinal nerves through the neural foramen, and which is of interest when performing interscalene anesthetic techniques. The supraclavicular techniques focus on the supraclavicular fossa, where the superior, middle, and inferior primary trunks divide into their anterior and posterior branches. The plexus runs superficially at this level, and high-frequency transducers (10 MHz) are thus needed to identify the structures. Technical difficulties are encountered in studying the supraclavicular region due to the presence of the supraclavicular depression, which complicates both manipulation of the probe and needle puncture. Although the primary trunks of the brachial plexus are easily identified between the scalene muscles in the interscalene space, the plexus is more difficult to locate in the supraclavicular zone. Color Doppler pulsing is not required to identify the subclavian artery, but it greatly facilitates identification of the brachial plexus by allowing the differentiation of nerves (hypoechogenic in the absence of Doppler effect) from the arterial and venous branches found in the zone (hypoechogenic with Doppler effect). The US anatomy of the supraclavicular region is shown in Figure 6. The pleura is identified as a hyperechoic fine line outlining the anechoic lung tissue.

Figure 1 : Basic equipment for supraclavicular block. View Larger Image   Figure 2 : Ultrasound machine and transducer. View Larger Image   Figure 3 : Anatomic relationships of the anterior scalene muscle. From Drake RL, Vogl AW, Mitchell AWM, et al. Gray’s Atlas of Anatomy. Philadelphia: Churchill Livingstone Elsevier, 2008, p. 492. View Larger Image   Figure 4 : Relationship of the subclavian artery, vein, and insertion of the anterior scalene muscle. From Drake RL, Vogl AW, Mitchell AWM, et al. Gray’s Atlas of Anatomy. Philadelphia: Churchill Livingstone Elsevier, 2008, p. 493. View Larger Image   Figure 5 : Relationship of the brachial plexus with the anterior scalene muscle, subclavian artery, and subclavian vein. From Drake RL, Vogl AW, Mitchell AWM, et al. Gray’s Atlas of Anatomy. Philadelphia: Churchill Livingstone Elsevier, 2008, p. 361. View Larger Image   Figure 6 : Supraclavicular sagittal cross-section at the level of the first rib, showing the subclavian artery (A), and identifying the hypodense nodular structure in the superoposterior portion of the subclavian artery that represent the divisions of the brachial plexus (arrows). AS, anterior scalene muscle; MS, middle scalene muscle; P, pleura; R, first rib; SCM, sternocleidomastoid muscle. From Harmon D, Frizelle HP, Sandhu NS, et al. Perioperative Diagnostic and Interventional Ultrasound. Philadelphia: Saunders Elsevier, 2008, p. 139. View Larger Image

Post-Procedure

CARE Immediate after placing the block Instruct the patient to avoid moving the arm; poor motor control of the arm can lead to injury. Assess the distribution of nerve block. Areas not covered by the block can be done by supplemental local anesthetic at surgical site (field block). Full development of the block can take 30 minutes. Post-surgery In PACU reassess the pain level and score. Look for any evidence of neck hematoma. Assess the motor and sensory function; let the patient know that brachial plexus block may not recede for 4 to 6 hours. Provide the patient with an arm sling to use until the block recedes. Follow up with patient after complete recovery of the block by assessing the motor and sensory function. Symptoms such as dyspnea, cough or pleuritic chest pain warrant immediate investigation for possible pneumothorax.  COMPLICATIONS Pneumothorax Occurs in 0.5% to 6.0% of cases and is more likely in tall, thin patients. Most occur within 24 hours, are usually small, often asymptomatic, and do not require specific treatment. Therefore, routine chest radiograph after supraclavicular block is not recommended. Treatment may require hospitalization and placement of a chest tube. Paralysis of the phrenic nerve Occurs in 40% to 60% of supraclavicular blocks, but is usually asymptomatic. In patients with underlying pulmonary disease or in morbidly obese patients, unilateral phrenic nerve block can cause severe symptoms of dyspnea and lead to significant pulmonary compromise Horner syndrome (stellate ganglion block) About 70% to 90% of patients will develop a Horner syndrome, which results from local anesthetic blockade of the stellate ganglion in the neck. Signs include ptosis, pupillary constriction, and conjunctival injection on the side of the block. This “non-serious” complication occurs more often with higher volumes of local anesthetic, and resolves with resolution of the local anesthetic block. Complications of Vascular Puncture Neck tenderness Ecchymosis Hematoma Local Anesthetic Toxicity Absorption of local anesthetic Intravascular injection Nerve injury Intraneural injection Direct needle injury Neuritis—possibly due to concentrated local anesthetic solutions or vasoconstrictors in the local anesthetic solution Injury resulting from malpositioning of the anesthetized limb Complications of needle puncture of soft tissue Infection Swelling Bruising OUTCOMES AND EVIDENCE US guidance for supraclavicular block is associated with a 95% success rate. Use of US may decrease time to perform a supraclavicular block, and decrease complications such as pneumothorax. US-guided blocks are associated with decreased rates of requirement for supplementation. Complication rates are low.