Infraclavicular brachial plexus block procedure guide

INTRODUCTION — The infraclavicular block (ICB) is a peripheral nerve block that anesthetizes the brachial plexus at the level of the cords (figure 1). ICBs are used for anesthesia and/or analgesia for surgery of forearm, wrist, hand, and fingers. This topic will discuss the anatomy, ultrasound imaging, and injection techniques for performing ICBs.

General considerations common to all peripheral nerve blocks, including patient preparation and monitoring, use of aseptic technique, localization techniques, drug choices, contraindications, and complications, are discussed separately. (See "Overview of peripheral nerve blocks".)

ANATOMY — The brachial plexus is formed by the ventral rami of the lower cervical and upper thoracic nerve roots (figure 2). The nerves of the brachial plexus (figure 1) travel through the neck, under the clavicle, and into the arm (figure 3). As the brachial plexus travels under the clavicle, the divisions form into posterior, lateral, and medial cords. As the cords pass between the clavicle and the axilla, they run deep to the pectoralis major and pectoralis minor muscles. The axillary artery and the brachial plexus travel just cephalad to the axillary vein (image 1).

●Cords of the brachial plexus – Though there is significant anatomic variability in the brachial plexus, the lateral cord is typically composed of nerve fibers from C5, C6, and C7 via the anterior division of the upper and middle trunks. The medial cord derives from C8 and T1 via the anterior division of the inferior trunk. The posterior cord is composed of the posterior divisions of each of the trunks and contains nerve fibers from each root of the brachial plexus [1].

There is also variability with respect to the positions of the cords of the brachial plexus [2,3]. The cords of the brachial plexus are named based on their typical position relative to the axillary artery (posterior, lateral, and medial). The lateral cord is immediately superolateral (cephalad) to the artery and the medial cord just inferomedial (caudad).

●Innervation – The cords and branches of the brachial plexus provide innervation of the arm below the shoulder, with the exception of the medial upper arm (intercostobrachial nerve, T2). Cutaneous sensory innervation of the upper extremity is shown in a figure (figure 4). Motor innervation of each terminal nerve is shown in a table (table 1).

Sensory and motor innervation are relevant for 1) pre-procedural assessment of existing neurologic deficits, 2) post-procedure assessment of clinical effect of nerve block, and 3) assessment of needle-nerve proximity when using nerve stimulation techniques.

ANATOMIC CLINICAL CORRELATIONS — The ICB provides anesthesia and analgesia to the elbow, forearm, wrist, hand, and fingers (figure 4) [4]. Compared with axillary and supraclavicular blocks that can also be used for these procedures, disadvantages of the ICB include the depth of the block and proximity of the target to the clavicle. The depth of the target from the skin can hinder visualization of the nerves and may require the use of lower frequency (lower resolution) ultrasound, particularly in patients with obesity. In addition, the needle approach is steep, and needle visualization may be challenging. Injecting local anesthetic (LA) adjacent to the posterior cord may push surrounding structures anteriorly and improve visualization.

Options for needle insertion may be limited by the need to place the ultrasound transducer close to the clavicle for block placement.

Various approaches to the ICB have been described [5,6]. We use a lateral approach, close to the coracoid process, in order to minimize the risk of pneumothorax, phrenic nerve block, and Horner's syndrome. (See 'Side effects and complications' below.)

Sources differ as to the reliability of intercostobrachial nerve blockade with infraclavicular or axillary brachial plexus injection [7,8]. Thus, when surgical anesthesia is the goal, we block the intercostobrachial nerve separately for surgery involving the proximal, medial arm.

INFRACLAVICULAR BLOCK TECHNIQUE

Patient positioning — Place the patient supine with the head turned to the opposite side. If possible, abduct the patient's arm to 90 degrees at the shoulder with the elbow flexed, and rotate the arm externally, to elevate the clavicle from the needle path and extend the pectoralis muscles. Alternatively, this block can be performed safely with the arm adducted at the patient's side. The transducer is placed differently for these two positions. If the arm is abducted, the transducer is placed in a parasagittal orientation just medial to the coracoid process and caudal to the clavicle. With this placement and the arm adducted, there is limited space between the transducer and the clavicle, making needle insertion difficult and needle visualization poor due to a steep needle trajectory. With the arm adducted, sliding the transducer caudally, and rocking the beam cephalad to change the field of view provides space for needle insertion and makes the angle of insertion less steep.

Block guidance technique — ICB can be performed with ultrasound guidance, nerve stimulator guidance, or ultrasound guidance with nerve stimulator confirmation of the nerves.

Ultrasound guidance versus nerve stimulation guidance — We suggest using ultrasound guidance (with or without nerve stimulator confirmation) rather than nerve stimulator guidance alone to perform ICB. If ultrasound guidance is not available, a different block may be a more reasonable alternative. This suggestion is based on benefits of ultrasound guidance for peripheral nerve block in general, and for ICB, possible evidence of reduced risk of inadequate block and reduced risk of vascular puncture compared with nerve stimulator guidance.

The quality of the evidence comparing ultrasound guidance with nerve stimulator guidance for ICB is overall low and consists of small trials. In a 2021 review of randomized trials, the success rate of ICB was higher with ultrasound guidance compared with nerve stimulator guidance (90.4 [95% CI 86.8-93.2] versus 82.5 [95% CI 78.1-86.2] percent, eight trials) [9]. The incidence of vascular puncture was lower with ultrasound guidance (0.5 [95% CI 0-3.3] versus 14.7 [95% CI 10.2-20.6] percent, five trials, 370 patients). The quality of evidence was low due to small trial size and significant heterogeneity.

Ultrasound guidance versus nerve stimulator guidance in general is discussed in detail separately. (See "Overview of peripheral nerve blocks", section on 'Block guidance techniques'.)

Nerve stimulation along with ultrasound guidance — Some practitioners prefer to use nerve stimulation concurrently with ultrasound guidance. We do not routinely use both guidance techniques, but occasionally use nerve stimulation to confirm needle tip placement when performing an ultrasound-guided ICB if the ultrasound image is unclear or difficult to obtain (eg, in patients with obesity or when positioning is difficult).

Ultrasound-guided block — Here we describe performing the block with the patient's arm abducted 90 degrees.

Ultrasound equipment — The authors use a high frequency (eg, 10-5 MHz) linear ultrasound transducer. Set the ultrasound depth at 4 to 5 cm initially, with a low frequency preset. A low frequency curvilinear probe is a useful alternative, ideally a small curvilinear transducer such as the SonoSite C11 or Phillips C8-5. (See "Ultrasound for peripheral nerve blocks", section on 'Transducers'.)

Ultrasound imaging

●Place the transducer in a parasagittal orientation just medial to the coracoid process and caudal to the clavicle (picture 1 and figure 5).

●Visualize the pectoralis major and minor muscles overlying the axillary artery and vein (image 1).

●Identify the axillary artery (hypoechoic, pulsatile, and noncompressible) and the axillary vein deep and slightly inferior to the artery. Color Doppler can help identify blood vessels (movie 1).

●Identify the lateral, medial, and posterior cords as hyperechoic structures containing hypoechoic nerve fascicles ("honeycomb" appearance) (image 1).

●During an ICB, it is useful to consider the axillary artery as the center of a clock face, with the posterior cord at the 6 o'clock position deep on the image, 12 o'clock position superficial, and the lateral and medial cords at variable locations near 3 and 9 o'clock, respectively, depending on probe and screen orientation (figure 6) [3].

Performing the block

●Infiltrate the skin and soft tissue at the injection site with 1% lidocaine, 1 to 3 mL, using a 25 gauge needle.

●Insert an echogenic B-bevel 20 to 22 gauge 10 cm needle using an in-plane approach (picture 2) in a cephalad to caudad trajectory at a steep angle dorsally and inferiorly (picture 2).

●Advance the needle tip to a position between the axillary artery and the posterior cord on the dorsal or 6 o'clock position relative to the artery, visualizing the length of the needle throughout (movie 2). Depending on the anatomic relationship between the lateral cord and the artery, the needle trajectory may be between the lateral cord and axillary artery or just lateral to the lateral cord along its inferior (dorsal) aspect.

●After negative aspiration, inject 20 to 30 mL of LA in 5 mL increments, with gentle aspiration between injections, while visualizing spread of LA from deep to superficial around the axillary artery. The goal is to achieve a "U-shaped," spread of LA both lateral (superior) and medial (inferior) to the axillary artery, which predicts a high likelihood of block success (movie 2) [10]. We stop injection at 20 mL if adequate spread of LA has been visualized, and inject an additional 10 mL with or without adjusting the needle tip if spread is suboptimal (movie 3).

●Block success depends on LA reaching the medial and lateral cords from an injection site at the 6 o'clock position deep to the axillary artery near the posterior cord, so adequacy of LA spread should be assessed continuously throughout injection.

•If spread is inadequate on the medial (inferior) side of the artery, advance the needle under the artery and reinject approximately 5 mL, visualizing spread. If spread to the medial cord is still inadequate, withdraw the needle and readvance superficial to the artery, positioning the tip at the medial (inferior) aspect of the artery. Inject between the medial cord and the artery (image 2).

•If spread is inadequate along the lateral side of the artery, withdraw the needle slightly from the 6 o'clock position (where the initial injection occurred), which should place the needle tip adjacent to the lateral cord. After negative aspiration, inject 5 to 10 mL of LA, while visualizing spread.

The two best-described approaches to ultrasound-guided ICB are the posterior cord injection described above and a triple-injection technique, whereby LA is administered around each cord of the plexus. The triple-injection technique results in a high rate of block success, but is not superior to a single posterior injection approach [11,12].

With a single-injection ultrasound-based technique, 20 to 30 mL of local anesthetic (LA) is administered incrementally deep to the axillary artery, nearest to the posterior cord. In contrast, a triple-injection technique is achieved with this injection of 10 mL around each cord of the brachial plexus, for a similar 30 mL total.

Nerve stimulator confirmation — Nerve stimulation can be used to confirm needle tip placement if ultrasound identification is challenging, as follows (see 'Nerve stimulation along with ultrasound guidance' above):

●For nerve stimulator confirmation, set an initial pulse width of 100 ms at 1 Hz and a current of 0.8 mA. This is a lower frequency and current than for primarily nerve-stimulator-guided procedures. Connect the stimulator to the needle and to an electrode on the patient's skin (picture 3) (see "Overview of peripheral nerve blocks", section on 'Equipment for nerve stimulator guidance'). When nerve stimulation is used to confirm nerve location (as opposed when stimulation is the primary block modality) the nerve stimulator is initially set to a pulse width of 100 ms at 1 Hz and a current of 0.8 mA.

●Use movement of the fifth finger to assess stimulation of the cords of the brachial plexus [13]. Movement of the fifth finger occurs in the direction of the cord of the same name (eg, posterior movement with stimulation of the posterior cord), as shown in a table (table 2).

●Once the desired stimulation occurs, decrease the stimulator current until the motor response disappears. Then turn the current up to the minimal current that results in a motor response. The goal is a stimulation response at 0.5 mA. Motor responses below 0.5 mA are not sought since appropriate stimulation confirms nerve location while simultaneously observing on ultrasound.

●The presence of a motor response at <0.2 mA strongly suggests intraneural needle placement and the needle should be repositioned without injecting.

Alternative ultrasound-guided techniques — There are several alternatives to the distal approach to blocking the cords of the brachial plexus. Here we describe two of those.

Costoclavicular approach — The costoclavicular block (CCB) is relatively recently developed block, best understood as a medial (proximal) approach to the cords of the brachial plexus [6,14]. At this location, the brachial plexus is more superficial than the more distal infraclavicular approach. Proposed advantages of the CCB include the following:

●Close proximity of the cords – The proximity of the cords to one another is the main proposed advantage of the CCB compared with alternative methods for blocking the cords of the brachial plexus. At the level of this block the cords are consistently close to one another and separated from the axillary artery. This is in contrast with the block location for a standard ICB, where the cords are variably arrayed around the artery and separated at some distance from one another. (See 'Anatomy' above.)

●Clear separation of the cords – Despite close proximity, there is clear separation of the cords with ultrasound imaging. This is in contrast with visualization of the cords at the level of a supraclavicular block.

The authors feel that these two factors suggest a good target for single-injection block and a potentially ideal location for placing a catheter among the cords for continuous block. Further study is required to determine the advantages and disadvantages of CCB relative to supraclavicular or distal ICB.

Posterior approach — The posterior approach to the ICB is a distal ultrasound-guided approach that attempts to overcome the steep needle angle of the standard ICB, and the difficulty placing the needle between the probe and clavicle [15]. This technique is sometimes referred to as the Retroclavicular Approach to The Infraclavicular Region (RAPTIR). The patient is positioned with the arm adducted. The ultrasound transducer is placed as it would be for a distal ICB (ie, parasagittal orientation, just medial to the coracoid process, caudal to the clavicle). After obtaining the usual ICB view on ultrasound, the needle is inserted superior (not inferior) to the clavicle and directed toward the plexus. This placement involves passing the needle through a "blind zone," when the needle tip is advanced behind the clavicle, though a benefit is that the needle trajectory is almost perpendicular to the ultrasound beam and the needle is easily visualized.

Injection is the same as for the standard ultrasound-guided distal ICB, aiming for U-shaped spread of 25 to 30 mL of LA. Reported success rates are high with the posterior (RAPTIR) technique (>90 percent) [15-17] and similar to success rates for standard ICB. In a trial including 110 patients who had surgery of the arm and forearm and were randomly assigned to either posterior or standard ICB, block performance time (primary outcome), block success and dynamics, number of needle passes, and complications were similar between groups [18]. Needle visibility was improved with the posterior block.

DRUG CHOICE AND DOSING

●Local anesthetics – Local anesthetics (LAs) are chosen according to the goal of the block (surgical anesthesia or analgesia) and the desired duration of the effect of the block (table 3). LAs for peripheral nerve blocks and the use of adjuvant drugs are discussed in more detail separately. (See "Overview of peripheral nerve blocks", section on 'Drugs'.)

Choices of LA for ICB are as follows:

•Surgical anesthesia only – 2% lidocaine or 1.5% mepivacaine.

•Postoperative analgesia – 0.25 to 0.5% bupivacaine or 0.5% ropivacaine.

•Surgical anesthesia and postoperative analgesia, either:

-For rapid onset – Equal volumes of a short-acting LA (2% lidocaine or 1.5% mepivacaine) plus a long-acting LA (0.5% bupivacaine or 1% ropivacaine). Note that mixing LAs results in onset and duration that are both intermediate between the two agents [19].

-When rapid onset is not required (ie, 30 minutes for onset is acceptable) – 0.25 to 0.5% bupivacaine or 0.5% ropivacaine.

•When ultrasound guidance is not used, epinephrine 2.5 to 3.3 mcg/mL should be included in the injectate as a marker of intravascular injection.

●Volume of local anesthetic – Various studies have looked at the minimum effective volume of LA required for successful ultrasound-guided infraclavicular blockade, with widely varying results [20-22]. Reliable surgical anesthesia was reported using 14 mL of 2% lidocaine in one study. Another study calculated the minimum effective volume in 90 percent of patients (MEV90) as 35 mL when using 1.5% lidocaine. Nerve stimulation techniques typically employ higher volumes of LA, with 30 to 50 mL described and 40 mL most common [23].

We use 20 to 30 mL for ultrasound-guided ICB and 30 to 40 mL for a nerve stimulation technique [10,24]. A higher volume of LA may be required with a stimulation-only technique, possibly due to the imprecise and indirectly verified location of the needle tip with a stimulation guided technique.

CONTINUOUS INFRACLAVICULAR BLOCK — Continuous brachial plexus catheters may be used to provide prolonged postoperative analgesia, beyond the duration provided by a single injection block.

●Catheter placement technique – The technique for placing the catheter is similar to the technique used for single-injection block. Similar to single-injection ICB, we suggest using ultrasound guidance to place continuous ICB catheters.

The needle tip is placed and the catheter is deployed deep (dorsal) to the axillary artery, between the artery and the posterior cord [25]. Appropriate catheter location posterior to the artery should be confirmed after the needle is withdrawn and before securing the catheter.

Equipment and technique for continuous peripheral nerve blocks are discussed separately. (See "Overview of peripheral nerve blocks", section on 'Continuous catheter techniques'.)

●Positioning, draping, and securing the catheter – Important technical aspects to consider when placing a catheter for continuous ICB are as follows:

•Placement of a perineural catheter takes longer than a single-injection block and sufficient time must be allocated prior to surgery.

•A large sterile field should be created to avoid contamination of the catheter. Either sterile towels or a clear plastic drape can be used. A clear plastic drape may facilitate communication with the patient.

•In addition to sterile gloves, mask, and cap, we wear a sterile gown to avoid contamination of the catheter during placement. A sterile ultrasound sheath must be used to avoid contamination of the sterile field.

•Compared with single-injection block, more liberal LA is usually required at the needle insertion site, since a larger needle is used. Slightly heavier sedation may also be necessary, though the patient needs to be conscious enough to report paresthesias.

•The catheter must be secured well to avoid catheter migration and/or inadvertent removal. We use a surgical glue at the catheter insertion site and loop the catheter under clear plastic sterile dressings to allow for slack if the catheter is inadvertently pulled.

●Infusion drug dose – After injecting a bolus of LA as described above for single-injection block, an infusion of LA at 5 to 10 mL/hour is initiated postoperatively by a continuous or programmed intermittent bolus technique. Ambulatory catheters, which can be managed and removed at home by the patient, are well-described and have an excellent safety record [26]. Our practice is as follows:

•We use a continuous infusion of 0.2% ropivacaine or 0.125% bupivacaine.

•A patient-controlled bolus may be available for inpatient and/or outpatient devices, depending on the equipment selected. We allow a 4 to 5 mL patient-controlled bolus with a 60 minute lockout.

•Ambulatory patients receive a comprehensive instruction sheet that includes the signs and symptoms of LA toxicity, pump maintenance information, and the acute pain service phone number prior to discharge.

SIDE EFFECTS AND COMPLICATIONS — ICBs are generally very safe, with few reported complications [27]. Complications common to all peripheral nerve blocks (eg, nerve injury, bleeding, local anesthetic [LA] systemic toxicity, infection) are discussed separately. (See "Overview of peripheral nerve blocks", section on 'Complications'.)

Pneumothorax is possible with the ICB, but should be rare with appropriate technique, needle orientation, and needle guidance. The self-limited side effects that occur with supraclavicular block (eg, hoarseness, Horner syndrome, phrenic nerve paresis) can occur with ICB, but less frequently [7,28]. In one randomized trial that compared the incidence of phrenic nerve block after ultrasound-guided infraclavicular versus supraclavicular brachial plexus block with 30 mL of 0.5% ropivacaine, complete phrenic nerve block diagnosed by ultrasound occurred in 3 percent of patients after ICB (1 of 32 patients) versus 34 percent of patients who had supraclavicular block (11 of 32 patients) [29]. Complete or partial block occurred in 13 percent of patients after ICB, compared with 44 percent after supraclavicular block.

Some (but by no means all) providers consider the ICB to be a deep plexus block, owing to the deep location of the axillary artery in the chest at the point the plexus is blocked. Deep blocks in non-compressible locations may increase the risk of hematoma. As a result, some providers follow the same guidelines for anticoagulation for ICB that would be used for neuraxial anesthesia [30]. These guidelines are discussed in detail separately. (See "Neuraxial anesthesia/analgesia techniques in the patient receiving anticoagulant or antiplatelet medication".)

We perform ICB in selected anticoagulated patients after considering risks and benefits and other alternative blocks (eg, axillary, supraclavicular).

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Local and regional anesthesia".)

SUMMARY AND RECOMMENDATIONS

●Anatomy – The brachial plexus is derived from the lower cervical and upper thoracic nerve roots (figure 2). The nerves of the brachial plexus (figure 1) travel through the neck, under the clavicle, and into the arm (figure 3).

•The infraclavicular block (ICB) targets the brachial plexus at the level of the cords.

•ICB is used for surgery of the arm at or below the elbow. (See 'Anatomy' above.)

●Block guidance technique – We suggest using ultrasound guidance (with or without nerve stimulator confirmation) rather than nerve stimulator guidance alone to perform ICB (Grade 2C), based on general benefits of ultrasound for peripheral nerve blocks, and for ICB, possibly reduced risks of inadequate block and vascular puncture. (See 'Ultrasound guidance versus nerve stimulation guidance' above.)

●Positioning – Position the patient supine with the arm abducted to 90 degrees and the arm externally rotated. If necessary, the arm can be adducted, though needle placement may be more difficult in this position. (See 'Patient positioning' above.)

●Performing the block – We perform ultrasound guided ICB as follows, with further explanation above (movie 2) (see 'Ultrasound-guided block' above):

•Use a high frequency (eg, 10-5 MHz) linear ultrasound transducer, with the depth set to 4 to 5 cm.

•Place the transducer just medial to the coracoid process and caudal to the clavicle, in a parasagittal orientation (picture 2).

•Identify the lateral, medial, and posterior cords of the brachial plexus around the axillary artery (image 1).

•Insert a 20 to 22 gauge block needle using an in-plane approach, placing the needle tip between the axillary artery and the posterior cord.

•After negative aspiration, inject 20 to 30 mL of local anesthetic (LA) in 5 mL increments with gentle aspiration between injections, while visualizing spread of LA in a U-shape from deep to superficial around the axillary artery. Adequate U-shaped spread is important for a successful block. If adequate U-shaped spread is not visualized, block each individual cord separately (image 1 and movie 3).

Alternative approaches (costoclavicular and posterior) are possible and are discussed above. (See 'Alternative ultrasound-guided techniques' above.)

●Nerve stimulator confirmation – Nerve stimulation can be used to confirm the nerve(s) during ultrasound guided block. (See 'Nerve stimulation along with ultrasound guidance' above.)

Obtain stimulation of the desired cord, denoted by motion of the fifth finger in the direction of the name of the cord. Confirm minimal response between 0.2 and 0.5 mA before injecting local anesthetic (LA) (table 2).

●Continuous ICB – We suggest using ultrasound guidance for performing continuous ICB (Grade 2C). In addition to the benefits of ultrasound guidance for placing the needle tip, ultrasound allows confirmation of the correct position of the catheter after it is deployed.

Continuous ICB is performed as described for single-injection block using a Touhy needle with a 19 or 20 gauge catheter inserted through it. The needle tip is placed and the catheter is deployed deep (dorsal) to the axillary artery, between the artery and the posterior cord, 4 to 6 cm beyond the tip of the needle. (See 'Continuous infraclavicular block' above.)

●Drug choice – LA choices are as follows (see 'Drug choice and dosing' above):

•Surgical anesthesia only – 2% lidocaine or 1.5% mepivacaine.

•Postoperative analgesia – 0.25 to 0.5% bupivacaine or 0.5% ropivacaine; for continuous block, infusion of 0.2% ropivacaine or 0.125% bupivacaine.

•Surgical anesthesia and postoperative analgesia, either:

-For rapid onset – Equal volumes of a short-acting LA (2% lidocaine or 1.5% mepivacaine) plus a long-acting LA (0.5% bupivacaine or 0.5% ropivacaine).

-When rapid onset is not required (ie, 30 minutes for onset is acceptable) – 0.25 to 0.5% bupivacaine or 0.5% ropivacaine.

●Side effects and complications – There are few reported complications specific to ICB. The self-limited side effects that occur with supraclavicular block (eg, hoarseness, Horner syndrome, phrenic nerve paresis) can occur with ICB, but less frequently. (See 'Side effects and complications' above.)