INTERSCALENE BLOCK -- BLOCK OF THE BRACHIAL PLEXUS AT THE INTERSCALENE GROVE

Any surgery on the upper extremity can be performed under brachial plexus block. However, attention must be paid to the technique and level at which brachial plexus is approached, as the sensory and motor blocks are significantly different among Interscalene, supraclavicular, infraclavicular, axillary or midhumeral brachial plexus blocks. Interscalene block   Common Indications Surgery on the shoulder joint, clavicle (Figure 1) Surgery on the humerus Closed reduction of dislocated shoulder   Contraindications Severe lung disease with decreased Vital Capacity (VC) Coagulopathy Infection at site of injection Personality disorder not consistent with awake sedation   Technique Patient position: Supine or semi-sitting Anatomical landmarks (Figure 2): Clavicle Cricoid ring Sternal (anterior) head of the sternocleidomastoid muscle Clavicular (posterior) head of the sternocleidomastoid muscle Sternal notch External jugular vein (white arrows) Interscalene groove (a groove between anterior and middle interscalene muscles) is identified as a second groove after the posterior border of the clavicular head of the sternocleidomastoid muscle.   Equipment   Figure 2. Interscalene block: Anatomy. Legend: 1. Clavicle 2. Cricoid cartilage 3. Anterior (sternal) head of the sternocleidomastoid muscle 4. Posterior (clavicular) head of the sternocleidomastoid muscle 5. Sternal notch 6. External jugular vein - white arrows Note that the interscalene groove is posterior to the clavicular head of the sternocleidomastoid muscle (4) and just anterior to the external jugular vein. Skin marker Sterile gloves Sterile 4"x 4" gauze Iodine solution 25 GA needle for skin infiltration Insulated, short (e.g.,2 inch, 22 GA) needle for nerve stimulator technique. Short bevel 22 Ga. 1.5 inch needle for paresthesia technique. 3 X 20 mL syringes with local anesthetic, attached to stopcocks and extension tubing. Block-tray Peripheral nerve stimulator *In our practice, we use Tracer II/ Solostim® nerve stimulator with foot pedal for control of the current output (LifeTech®, Inc., Stafford, TX). Controlling the current output by foot pedal eliminates the need for helpers, provides faster control of the current output and allows unassisted performance of the block. (Disclaimer). Technique description   Figure 3. The patient is positioned supine or in semi-sitting position. The head is turned away from the side to be blocked. Further accentuation of the anatomy can be achieved by asking the patient to lift his/her head up against resistance (with the head turned to the side). Additionally, when palpating the interscalene groove, the groove can be better appreciated by asking the patient to sniff. The palpating fingers tend to fall into the groove with every forceful inspiration to contraction of the anterior and middle scalene muscles. Figure 4. We routinely use skin marker to delineate the anatomy before each and every block. This not only helps with the success, but also with teaching of the technique. Legend: 1. Clavicle 2. Cricoid cartilage 3. Anterior (sternal) head of the sternocleidomastoid muscle 4. Posterior (clavicular) head of the sternocleidomastoid muscle 5. External jugular vein - white arrows   Examine the anatomy of the neck with the patient in the supine or semi-sitting position (Figure 3). With the head of the patient rotated slightly toward the opposite side to be blocked, the anatomy is better accentuated. A skin marker should routinely be used to delineate the anatomical structures before performing the block (Figure 4). Prepare the skin with iodine solution. Figure 5. Infiltration of local anesthetic alongside the level of the cricoid cartilage can help reduce the discomfort during block placement. It is important to avoid injection into the external jugular vein which frequently lies in the proximity of the interscalene groove.   Figure 6. The needle is inserted into the interscalene groove at the level of the cricoid cartilage and advanced into the groove perpendicular to the plane defined by the anterior and middle scalene muscles and with a 30° caudad direction. Identify the interscalene groove using the two-finger technique (Figure 6). Local anesthetic can be infiltrated subcutaneously at the level of the cricoid cartilage (Figure 5). The needle is attached to the nerve stimulator and the stimulator is set at 0.6 mA to 0.8 mA/2 Hz. The needle is inserted into the interscalene groove at the level of the cricoid cartilage and advanced into the groove perpendicular to the plane defined by the anterior and middle scalene muscles and with a 30° caudad direction (Figure 6)  Failure to obtain motor response to nerve stimulation should prompt withdrawal of the needle and re-insertion in 5%-10% angle anterior or posterior to the initial insertion plane. The twitches of the shoulder, arm or forearm are typically elicited at a depth of 1-2 cm. When twitches are obtained at a current of 0.4 mA or less, local anesthetic mixture is injected in 3-5 mL boluses, pausing to aspirate between each bolus. Successful block is indicated by a fast onset of change in sensory and temperature perception over the shoulder area, as well as an almost immediate loss of proprioception of the blocked arm.   Local Anesthetic Mepivacaine 1.5% + epinephrine 1/300,000 + sodium bicarbonate 1 meq/30 mL. This can be mixed by adding 0.1 mL of epinephrine [1 mg/mL] (100 mg) and 1 mL sodium bicarbonate [1 meq/mL] (1 meq) to each 30 mL vial of 1.5% mepivacaine. We use 40-55 ml of this mixture for surgical anesthesia. Duration: 3 hours of surgical anesthesia, up to 3 hours of additional analgesia. If a greater duration is required, we commonly use Ropivacaine 0.5% 40 ml. Duration: 8 hours of surgical anesthesia, with up to 24 hours of analgesia.   Complications 100% incidence of ipsilateral hemidiaphragm paralysis leading to a 30% reduction in vital capacity. Intravascular injection Cervical epidural block Local anesthetic toxicity Hematoma/ecchymosis   Side-effects Horner's syndrome Hoarseness of the voice (recurrent laryngeal nerve block) Tips Strip of skin underlying the medial aspect of the arm will not be anesthetized. This is because T2 is not blocked by brachial plexus block. T2 supplies sensory innervation only to the skin innervated by the intercostobrachial nerve. All of the muscles and bones of the upper extremity are innervated by nerves whose roots are in the brachial plexus. Subcutanous infiltration of local anesthetic will suffice. Remember that shoulder surgery takes place right next to the patient's ear and face, thus reassurance and sedation are required. Keep drapes off patient's face. Interscalene block results in 100% incidence of phrenic nerve block, resulting in loss of ipsilateral hemidiaphragm function. Thus, make sure to reassure the patient about dyspnea should they complain of breathing difficulty (rare). NEVER re-direct the needle cephalad and NEVER insert the needle deeper than 1" (2.5cm). Even in the very obese patients, brachial plexus is very superficial. Inserting needle deeper substantially increases the risk of otherwise exceedingly rare, but serious complications. The twitches of the deltoid muscle are sufficient. There does not seem to be any increase in success rate after obtaining more distal twitch response.

Go to top

www.gums.ac.ir