Ultrasound-Guided Regional Nerve Blocks in Emergency Medicine

Kay Odashima, MD
Director, Medical Student Education in Emergency Ultrasound
Department of Emergency Medicine
Maimonides Medical Center

Stephen Strasberg, MD
Assistant Professor of Emergency Medicine
Zucker School of Medicine
Northshore University Hospital

Eitan Dickman, MD, FACEP, FAIUM
Executive Vice Chairman and Medical Director
Department of Emergency Medicine
Maimonides Medical Center

QUICK LINKS TO NERVE BLOCK FIGURES
Superficial Cervical Plexus Nerve Block
Interscalene Brachial Plexus Nerve Block
Supraclavicular Brachial Plexus Nerve Block
Infraclavicular Brachial Plexus Nerve Block
Axillary Brachial Plexus Nerve Block
Median Nerve Block
Radial Nerve Block
Ulnar Nerve Block
Femoral Nerve Block
Fascia Iliaca Compartment Block
Popliteal Sciatic Nerve Block Position
Popliteal Sciatic Nerve Block Screen
Posterior Tibial Nerve Block
Intercostal Nerve Block
Serratus Anterior Plane Block

INTRODUCTION

Painful conditions are the most common reason patients seek care in an Emergency Department, and ultrasound guided regional anesthesia is an important analgesic modality available to emergency clinicians. Ultrasound guidance has demonstrated similar success rates compared to traditional peripheral nerve block techniques and provides the advantages of real-time needle visualization, demonstration of anesthetic spread, shorter procedure time, and fewer needle attempts. (Chin 2008) With the addition of color Doppler, ultrasound guidance can also prevent inadvertent intravascular injection. (Hahn 2014) Sonographic guidance of nerve blocks is therefore preferred over landmark based techniques, when feasible. Nerve stimulators are commonly employed by anesthesiologists when performing regional anesthesia; however, ultrasound guidance of these procedures has equivalent or better success rates. (Duncan 2013, Schnabel 2013) Numerous studies demonstrate that ultrasound-guided regional anesthesia performed by emergency clinicians is safe and effective. (Akhtar 2013, Aydin 2016, Beaudoin 2013, Baker 2015, Dickman 2015, Fletcher 2003, Flores 2015a, Flores 2015b, Hahn 2014, Haslam 2013, Heflin 2015, Johnson 2014a, Johnson 2014b)

PREPARATION AND EQUIPMENT

A high-frequency linear ultrasound transducer is recommended for most ultrasound-guided nerve blocks. Additionally, the operator will need a long needle such as a commercially available nerve block needle or, if these are not available, a spinal needle. Some specialized needles consist of an echogenic tip that provides improved visualization. The operator may administer the injection on her own using a syringe and needle; alternatively, IV catheter extension tubing may be attached between the needle and the syringe to allow for better manual control of the needle during the procedure, with an assistant performing the aspiration and injection. (Figure 1) Recommended setup for ultrasound-guided regional nerve blocks is demonstrated in Figure 2. The clinician should position herself in a comfortable seated or standing upright position, with the ultrasound machine placed on the opposite side of the patient in the direct line of sight of the location of planned needle insertion.

IN-PLANE VS. OUT-OF-PLANE TECHNIQUE

Two techniques can be employed when performing real-time ultrasound-guided regional anesthesia: in-plane and out-of-plane. For both approaches, the nerve is visualized in its transverse (short) axis. When utilizing the in-plane technique, the needle is passed under the long axis of the ultrasound probe and remains visualized for the entirety of the procedure. This is generally the preferred technique, (Akhtar 2013, Fingerman 2009) as visualization of the needle throughout its trajectory decreases the likelihood of lacerating critical soft tissue structures or impaling the nerve. In the out-of-plane technique, the needle is inserted perpendicular to the probe and only a cross-section of the needle directly under the ultrasound beam is visualized. It is possible to follow the trajectory of the needle tip by sliding the probe forward as the needle is advanced through the tissues. However, this can be technically challenging especially when performing blocks on nerves located in deep tissues. There are instances where an out-of-plane technique can be successfully utilized, but this is usually only for superficial nerves without surrounding vasculature or other structures that could be inadvertently punctured.

ANISOTROPY

While performing ultrasound guided nerve blocks, it is important to understand the concept of anisotropy. Anisotropy is a sonographic quality exhibited by musculoskeletal structures such as tendons and nerves, in which the nerve appears maximally hyperechoic when the angle of the insonating beam runs perpendicular to the nerve fibers. At oblique angles, the echogenicity of the nerve bundle will appear significantly reduced. If a nerve is difficult to visualize, instead of moving the probe, try to rock, tilt or “heel toe” the probe to change the angle at which the ultrasound beams reflect off of the nerve. (Suk 2013)

COMPLICATIONS OF REGIONAL ANESTHESIA

Sensitivity to Local Anesthetic

Local anesthetics (LA) are classified as esters or amides by the type of bond that connects the lipophilic aromatic ring to the hydrophilic amine group. Commonly used esters include cocaine, chloroprocaine, procaine, tetracaine and benzocaine while commonly used amides include lidocaine, bupivacaine, levobupivacaine, ropivacaine, prilocaine and etidocaine.

LA’s often contain preservatives such as methylparaben, propylparaben, or sulphites, which likely contribute to some sensitivity reactions. (Boren 2007) However, true allergic reactions to LA’s are rare, and estimated to constitute less that 1% of all reactions to LA. (Schatz 1984)

Nerve Damage

Peripheral nerve damage secondary to regional anesthesia is rare and its effects are usually transient, mild, or subclinical. In a study of 158,083 regional blocks performed without ultrasound guidance, only 12 (0.0024%) peripheral neuropathies were reported, of which 7 had persistent symptoms after 6 months. (Liguori 2004) In a later study of 6,069 patients who received ultrasound-guided regional nerve blocks, only 30 had a block-related nerve injury (0.04%). (Barrington 2009)

Several factors are linked to an increased risk of nerve damage, including high-pressure injections, needle type, and underlying medical conditions. Several animal studies found that while low-pressure (<12 psi) intraneural injections did not result in functional nerve damage, high-pressure injections (>20-38 psi) were more likely to result in the development of functional neurologic injury. It is postulated that the high-pressure injections were indicative of accidental intrafascicular injections, i.e. the tip of the needle was within the nerve itself. (Jeng 2011) Another study demonstrated that an opening injection pressure of ≥15 psi indicated needle contact with the nerve. Disposable manometers that attach in between the syringe and needle to monitor injection pressures are commercially available and may help to prevent inadvertent intraneural injection. Though some experts recommend using an injection pressure monitor while performing nerve blocks, (Gadsen 2010) there is no evidence to suggest that routine monitoring of opening injection pressures reduces the risk of neural injury, (Gadsen 2014) and manometry during PNB is currently not standard care. Feeling resistance against the injection of anesthetic may be an indication of intraneural needle placement; anesthetic ought to be injected slowly and in small aliquots, and the injection should be halted if the patient reports painful paresthesias.

The type of needle used may also play a role in the likelihood of nerve injury. Because the perineural sheath surrounding the fascicle is composed of tough tissue, it is less likely to be penetrated with a blunt, short-bevel needle. (Jeng 2011) A study of rabbit sciatic nerves found that short bevel needles were less likely to pierce the perineurium than long bevel needles. The study also found that a needle that penetrated the fascicle perpendicularly to the nerve fibers was associated with greater nerve injury than when the bevel was oriented parallel to the nerve fibers. (Selander 1997) However, when a short bevel needle does penetrate the fascicle, it is associated with more severe and longer duration nerve injury than with long bevel needles. (Rice 1992) Yet another study compared beveled needles to tapered needles and found that tapered needles transected fewer axons when inserted intrafascicularly. (Maruyama 1997) Echogenic needles have demonstrated improved needle tip visualization over standard needles, (Hebard 2001, Hocking 2012, Fuzier 2015) however, further studies are needed to determine whether echogenic needles improve clinical outcomes of ultrasound-guided regional anesthesia procedures. (Sviggum 2013) There is presently insufficient evidence to favor one needle tip design over another, and current consensus leaves this choice to provider preference. Finally, though the reason is unclear, patients with preexisting nerve pathology (e.g. chemotherapy related neurotoxicity or diabetic neuropathy) are more likely to develop nerve injury after a regional nerve block. (Borgeat 2001, Neal 2002)

It is important to document the following elements in the patient’s chart: the type of block, the anesthetic used and its amount, a complete pre-block neurovascular exam (sensory and motor), and the time that the nerve block was performed. In cases where compartment syndrome is of concern (i.e. crush injuries), this procedure ought to be communicated with the appropriate consulting service. A skin marker should also be used to label the anatomic site of injection as well as write the time of the procedure.

Local Anesthetic Systemic Toxicity (LAST)

Epidemiologic data on LAST is limited to a few studies reporting incidence within a specific patient population, case series, and case reports. One study found that 79 out of 10,000 patients from a single institution that had a brachial plexus block performed developed a seizure, possibly from unintentional intravascular injection. (Brown 1995) Another study found that the frequency of seizures with various regional blocks ranged between 0-25 in 10,000. There were no cardiac arrests secondary to LAST reported in this study. (Auroy 2002)

Symptoms and signs of LAST are classically described as starting with perioral numbness, tinnitus, and a metallic taste in the mouth. This progresses to seizure, altered mental state, and coma, which may shortly thereafter be followed by arrhythmias and cardiovascular collapse. Onset of LAST can be immediate (<60 secs) if inadvertent intravascular injection occurs, or can be more delayed (up to 30 mins) in situations that require tissue absorption such as subcutaneous infiltration. Because the timing of the onset of LAST is variable, it is recommended that a patient be closely monitored for at least 30 minutes after injection. (Neal 2010) Severe lidocaine toxicity generally manifests as seizure progressing to cardiac arrest and lasts 10-20 minutes; therefore patients can often be managed through the duration of toxicity with supportive cardiac arrest care (chest compressions, rescue oxygenation) even if lipid emulsion is not available. In contrast, severe bupivacaine toxicity causes cardiac arrest without antecedent seizure activity, and toxicity may last hours–all efforts should be made to treat these patients with lipid emulsion therapy. (Schwartz 2015)

Techniques recommended to reduce the incidence of LAST include careful attention to maximum recommended doses and using the lowest effective dose of local anesthetic, injecting local anesthetic in small increments (3-5 mL aliquots and pausing 15-30 seconds between each injection), and aspirating before each injection to ensure no vascular entry. Sonographic guidance has the potential to reduce intravascular injections; however, its overall effectiveness in reducing LAST has yet to be determined. (Neal 2010)

Table 1: Recommended doses, onset and duration of action of commonly used local anesthetics for peripheral nerve blocks.

Anesthetic

Weight Based Dose (Wallace 2015)

Maximum Dose (Rosenberg 2004)

Duration

(Tsai 2007)

Chloroprocaine

Without Epi:

With Epi:

11 mg/kg

14 mg/kg

800 mg

1,000 mg

30-60 mins

40-70 mins

Lidocaine

Without Epi:

With Epi:

4.5 mg/kg

7 mg/kg

300 mg

500 mg

60-120 mins

90-180 mins

Ropivacaine

Without Epi:

With Epi:

3 mg/kg

3.5 mg/kg

225 mg

180-360 mins

Bupivacaine

Without Epi:

With Epi:

2.5 mg/kg

3 mg/kg

175 mg

225 mg

180-360 mins

300-480 mins

Calculating LA doses: What do the percentages mean?

1% = 10 mg/mL

0.5% = 5 mg/mL

0.25% = 2.5 mg/mL

Life threatening LAST is generally due to IA or IV injection, whereas milder toxicity is more typical from overdoses administered into the SQ tissue. For cardiac arrest thought to be due to LAST, after initiating basic and advanced life support, 20% lipid emulsion should be administered as a 1.5 mL/kg bolus followed by a 0.25 mL/kg/min infusion. The bolus can be repeated and the infusion rate can be increased to 0.5 mL/kg/min as needed for persistent cardiovascular collapse and should be continued for at least 10 minutes after cardiovascular stability has been achieved, or up to one hour. One key deviation from ACLS guidelines in managing patients with LAST is to use significantly smaller doses of epinephrine (<1 mcg/kg), as some animal studies have demonstrated poorer outcomes with epinephrine compared to lipid therapy in the treatment of bupivacaine induced-asystole. (Neal 2010)

NERVE BLOCK PROCEDURES

There are many locations throughout the body that are amenable to ultrasound-guided regional anesthesia. Below we will highlight some of the more common and high yield nerve blocks relevant to emergency care.

UPPER EXTREMITY NERVE BLOCKS

Superficial Cervical Plexus Nerve Block (Figure 3)

Block Distribution: Skin of anterolateral neck from the inferior ⅓ of ear down to skin overlying clavicle.

Block Volume: 10-15 mL

Uses in the Emergency Department: Lower ear laceration, clavicle fracture, central venous catheter placement

Probe Placement: Transversely over the middle portion of the sternocleidomastoid muscle (SCM).

Sonographic landmarks: The cervical plexus lies immediately posterior to the lateral border of the sternocleidomastoid (SCM) muscle and below the prevertebral fascia. Identify the lateral border of the SCM and inject just below the prevertebral fascia which appears as a hyperechoic line immediately below the SCM. (Photo)

Approach and Needle Trajectory: In-plane, from lateral to medial until the needle tip is located just deep to the lateral edge of the SCM and prevertebral fascia.

Special Considerations: There is considerable variability in the distribution of analgesia at the level of the ear.

Lit Bit: Use of the superficial cervical plexus block for analgesia in an acute clavicle fracture:. The patient’s pain score went from a 9/10 to a 1-2/10 immediately post-procedure with a return to moderate pain controlled with oral analgesics at hour 20. (Herring 2012)

Interscalene Brachial Plexus Nerve Block (Figure 4)

Block Distribution: Clavicle, shoulder, lateral arm above elbow.

Block Volume: 10-20 mL

Uses in the Emergency Department: Clavicle fracture, proximal and mid-humerus fracture, reduction of shoulder dislocation, drainage of deltoid abscess, laceration repair at the lateral arm.

Probe Placement: Transversely over the lateral neck at the level of the thyroid

Sonographic landmarks: Start at the clavicle and scan cephalad. First, identify the subclavian artery and the supraclavicular brachial plexus and then trace the brachial plexus to the interscalene groove located between the anterior and middle scalene muscles, which are located deep to the lateral edge of the sternocleidomastoid. The nerve roots appear as stacked hypoechoic circles surrounded by hyperechoic tissue and have been described as having a “traffic light” appearance.

Approach and Needle Trajectory: In-plane, from lateral to medial until the needle tip is in the interscalene groove between the C5 and C6 nerve roots.

Special Considerations: This block will likely cause transient ipsilateral diaphragmatic paralysis due to the close proximity of the phrenic nerve to the interscalene groove. Be cautious if patient has underlying pulmonary disease or known contralateral diaphragmatic paralysis; patients receiving this nerve block should have cardiopulmonary monitoring including pulse oximetry during and after the procedure.

High volumes of local anesthetic may also cause an ipsilateral Horner’s syndrome due to the proximity of the sympathetic chain; this will resolve as the local anesthetic wears off.

Lit Bit: Randomized study demonstrating successful use of an interscalene brachial plexus block for acute shoulder dislocation as an alternative to procedural sedation with reduced ED length of stay and less one-on-one provider time with similar pain scores. (Blaivas 2011)

Supraclavicular Brachial Plexus Nerve Block (Figure 5)

Block Distribution: Arm below the level of the shoulder excluding the medial proximal arm

Block Volume: 20-25 mL

Uses in the Emergency Department: reduction of distal humerus fractures and elbow dislocations, complex laceration repair, drainage of large abscess, and other procedures/analgesia distal to the shoulder.

Probe Placement: Transversely just superior to the clavicle.

Sonographic landmarks: Identify the subclavian artery and the supraclavicular brachial plexus which appears as a cluster of anechoic circular structures surrounded by hyperechoic tissue often described as a cluster of grapes or honeycomb. This cluster rests on the first rib and lies above the apex of the lung.

Approach and Needle Trajectory: In-plane, from lateral to medial until the needle tip is located near the brachial plexus. The area is hydrodissected until local anesthetic is seen surrounding all the nerve roots.

Special Considerations: Ipsilateral diaphragmatic paralysis and Horner’s syndrome are potential complications of this block (see Interscalene Brachial Plexus Nerve Block). Pneumothorax is another potential complication given the close proximity of the pleura to the needle insertion site, making visualization of the needle tip throughout the procedure critical to performing a safe block. There is sometimes an arterial branch overlying the nerve plexus, preventing use of this block.

Lit Bit: A case series of 5 patients demonstrating the use of ultrasound-guided supraclavicular brachial plexus block for the treatment of various acute painful conditions (I&D of forearm abscess, closed reduction of metacarpal fracture, analgesia for midshaft humerus fracture, reduction of posterior elbow dislocation). The blocks were performed successfully without complications, and excellent analgesia was achieved in all cases, obviating the need for procedural sedation. (Stone 2007)

Infraclavicular Brachial Plexus Nerve Block (Figure 6)

Block Distribution: Arm distal to the the shoulder excluding the medial proximal arm.

Block Volume: 20-30 mL

Probe Placement: Parasagittally along lateral clavicle.

Sonographic landmarks: Identify the axillary artery. The lateral, posterior, and medial cords of the plexus are located in a “U” shape around the axillary artery.

Approach and Needle Trajectory: In-plane, with the needle inserted below the clavicle, from cephalad to caudad, until the needle is posterior to the axillary artery and the local anesthetic spreads in a “U” shape around the artery.

Special Considerations: The pleura should be visualized and avoided in order to decrease the incidence of pneumothorax.

Lit Bit: Case report describing the successful use of an ultrasound-guided infraclavicular block instead of procedural sedation for the reduction of an acute posterior elbow dislocation (Heflin 2015)

Axillary Brachial Plexus Nerve Block (Figure 7)

Block Distribution: Mid arm down to and including hand, excluding skin overlying the deltoid and lateral arm.

Block Volume: 20-25 mL

Uses in the Emergency Department: reduction of distal radius fractures/dislocations, complex laceration repairs and abscess drainage of the hand, forearm and medial arm.

Probe Placement: With the shoulder abducted and elbow flexed, perpendicular to the humerus in the axillary crease.

Sonographic landmarks: Identify the axillary artery. The radial, median, and ulnar nerves are located around the axillary artery. The musculocutaneous nerve is located between the biceps and coracobrachialis muscle.

Approach and Needle Trajectory: In-plane, from superior to inferior, aiming posterior to the axillary artery and injecting to surround all the nerves (radial, median, ulnar and musculocutaneous nerves). Often a single approach is inadequate, and this technique may require multiple redirections toward each nerve.

Special Considerations: To perform multiple injections, first withdraw the needle until it is just below the skin, before redirecting it toward the new target. Avoid compressing the axillary vein which is usually superficial to the artery.

Lit Bit: Case reports demonstrate that upper extremity fractures can be safely and effectively reduced in the emergency department using landmark technique axillary nerve block, (Alimohammadi 2014) as well as successful ultrasound-guided axillary nerve block for the reduction of a first metacarpal fracture and a mid-shaft ulnar and radial fracture. (Bhoi 2010)

Median Nerve Block (Figure 8)

Block Distribution: Distribution of median nerve in the hand and wrist.

Block Volume: 5-10 mL

Uses in the Emergency Department: Complex laceration repairs, abscess drainage, burns, foreign body removal

Probe Placement: Transversely over the volar aspect of the mid forearm.

Sonographic landmarks: Identify the median nerve, which runs between the flexor digitorum profundus and the flexor digitorum superficialis, scanning both proximally and distally to ensure the nerve is correctly identified.

Approach and Needle Trajectory: In-plane or out-of-plane technique may be used depending on how superficial the nerve is and the presence of vasculature. Either a medial or lateral approach may be utilized. It is unnecessary to completely surround the nerve with anesthetic.

Special Considerations: Unlike the radial and ulnar nerves which run alongside their corresponding arteries within the forearm, the median nerve has no corresponding artery. As the median nerve approaches the wrist or elbow, the surrounding tendons can make identifying the nerve more challenging. To reduce patient discomfort, use a small (25 or 27 gauge) needle for this block.

Lit Bit: Ultrasound-guided forearm nerve blocks are more effective than landmark based wrist blocks in the emergency department in a prospective, randomized study. (Sohoni 2016)

Radial Nerve Block (Figure 9)

Block Distribution: Distribution of the radial nerve in the hand and wrist.

Block Volume: 5-10 mL

Uses in the Emergency Department: Complex laceration repairs, abscess drainage, burns, foreign body removal

Probe Placement: Transversely over the lateral aspect of the distal arm with the elbow flexed and placed across the patient’s chest.

Sonographic landmarks: Identify the hyperechoic triangular or oval-shaped radial nerve in the fascial plane between the brachialis and brachioradialis muscles. Scan both proximally and distally to ensure the nerve is correctly identified.

Special Considerations: If the radial nerve is not readily identified, locate the radial nerve in the forearm using the radial artery as a landmark and trace the nerve proximally to the distal lateral arm. To reduce patient discomfort, use a small (25 or 27 gauge) needle for this block.

Ulnar Nerve Block (Figure 10)

Block Distribution: Distribution of ulnar nerve in the hand and wrist.

Block Volume: 5-10 mL

Uses in the Emergency Department: Complex laceration repairs, abscess drainage, burns, foreign body removal, Boxer’s fracture reduction

Probe Placement: Transversely over the mid forearm.

Sonographic landmarks: Identify the ulnar nerve immediately medial to the ulnar artery. Scan both proximally and distally to ensure the nerve is correctly identified.

Special Considerations: Color doppler can be helpful in identifying the ulnar artery. To reduce patient discomfort, use a small (25 or 27 gauge) needle for this block.

LOWER EXTREMITY NERVE BLOCKS

Femoral Nerve Block (Figure 11)

Block Distribution: Anterior and medial thigh down to the knee, component of the hip joint, and a variable portion of the medial leg and foot.

Block Volume: 10-20 mL

Uses in the Emergency Department: Hip fracture, femur fracture, knee injury including patellar fracture, incision and drainage of abscess or laceration repair over anterior or medial thigh.

Probe Placement: Transversely over the inguinal crease.

Sonographic landmarks: At the level of the inguinal crease, find the femoral artery medially. The femoral nerve lies immediately lateral to the femoral artery and often appears as a hyperechoic triangular structure shaped like a “pennant.” The nerve sits superficial to the iliacus muscle and is covered by the fascia iliaca.

Approach and Needle Trajectory: In-plane, from lateral to medial through both the fascia lata and fascia iliaca until the needle tip is immediately above, lateral or below the nerve. It is beneficial to first inject anesthesia deep to the nerve, so that the anesthesia will lift the nerve superficially and make any subsequent injection above the nerve easier.

Special Considerations: In order to achieve an adequate block, the needle must penetrate both the fascia lata and fascia iliaca. Correct needle placement will be demonstrated by the local anesthetic spreading below the femoral nerve, lifting it off the iliacus muscle.

Lit Bit: Ultrasound-guided femoral nerve block is equally effective in reducing pain for both patients with intracapsular and extracapsular hip fractures in the emergency department has been demonstrated in a multicenter, randomized clinical trial. (Dickman 2015)

Fascia Iliaca Compartment Block (Figure 12)

Block Distribution: Lateral thigh (lateral femoral cutaneous nerve), anterior and medial thigh down to the knee, and a variable portion of the medial leg and foot (femoral and obturator nerves).

Block Volume: 30-40 mL

Uses in the Emergency Department: Hip fracture, femur fracture, knee injury, incision and drainage of abscess or laceration repair over lateral, anterior or medial thigh.

Probe Placement: Transversely over the inguinal crease.

Sonographic landmarks: The relevant landmarks for the fascia iliaca compartment block are the same as for the femoral nerve block. At the level of the inguinal crease, find the femoral artery medially. The femoral nerve lies immediately lateral to the femoral artery and often appears as a hyperechoic triangular structure shaped like a “pennant.” The nerve sits superficial to the iliacus muscle and is covered by the fascia iliaca.

Approach and Needle Trajectory: In-plane, from lateral to medial. The needle tip should be 1-2 cm lateral to the femoral nerve and just deep to the fascia iliaca. The local anesthetic will hydrodissect the fascia away from the iliacus muscle, spreading both medially toward the femoral nerve and laterally toward the lateral femoral cutaneous nerve.

Special Considerations: The fascia iliaca compartment block differs from the femoral nerve block in that instead of injecting directly adjacent to the nerve, the local anesthetic is deposited in the potential space between the fascia iliaca and iliacus muscle 1-2 cm lateral to the femoral nerve itself. Because the injection is performed away from the femoral nerve and artery, there is less risk of intraneural or intravascular local anesthetic injection. Because the fascia iliaca compartment block is a high-volume block, it is especially important to be aware of the maximum recommended dosage in order to prevent local anesthetic systemic toxicity (LAST).

Lit Bit: Ultrasound-guided fascia iliaca compartment block has been demonstrated to provide safe and effective pain control in patients with hip fractures in the emergency department. (Haines 2012)

Popliteal Sciatic Nerve Block (Figure 13 and Figure 14)

Block Distribution: The entire lower leg below the knee except for a variable portion of the medial leg and foot which is innervated by the saphenous nerve.

Block Volume: 20-30 mL

Uses in the Emergency Department: Fractures, lacerations and abscesses involving the lower leg, ankle and foot.

Probe Placement: With the patient in a prone,lateral decubitus, or supine (bending the knee, with pillows/blankets placed underneath the elevated foot) position, place the transducer transversely over the popliteal crease and scan proximally until the appropriate sonographic landmarks are identified, usually between 5-10 cm proximal to the popliteal crease.

Sonographic Landmarks: Identify the popliteal artery and vein at the level of the popliteal crease. By applying gentle pressure with the ultrasound transducer, the popliteal vein will compress and the tibial nerve will be visible as a hyperechoic circular or ovoid structure immediately superficial and lateral to the popliteal artery. The common peroneal nerve may also be visualized lateral to the tibial nerve. Slide the transducer proximally until the tibial and common peroneal nerves fuse to form the sciatic nerve.

Approach and Needle Trajectory: The needle is inserted in-plane from lateral to medial until the needle tip is adjacent to the sciatic nerve. Inject a small volume of local anesthetic to confirm needle position within the epineural sheath that surrounds the sciatic nerve. With the needle in correct position, the local anesthetic will be seen surrounding the sciatic nerve and tracking proximally and distally along the nerve sheath, and may cause a separation of the tibial and common peroneal nerves.

Special Considerations: Though controversial, it is thought that regional anesthesia can potentially delay the diagnosis of compartment syndrome by masking pain especially in high-risk injuries such as tibial plateau fractures or crush injuries. (Mutty 2008) Femoral neck fractures and ankle fractures are less frequently associated with this complication of orthopedic injuries. (Wu 2011)

Lit Bit: Emergency physician-performed ultrasound-guided popliteal nerve blocks were successfully used for pain control without need for procedural sedation for wound irrigation and reduction of bilateral open calcaneal fractures, plantar foot foreign body removal and laceration repair, calf abscess incision and drainage, and closed reduction and splinting of a tri-malleolar and posterior ankle dislocation. (Herring 2011)

Posterior Tibial Nerve Block (Figure 15)

Block Distribution: Heel and plantar surface of foot.

Block Volume: 3-5 mL

Uses in the Emergency Department: laceration repair, foreign body removal.

Probe Placement: Transversely, immediately posterior or just proximal to the medial malleolus.

Sonographic Landmarks: Find the tibial artery and vein just posterior to the medial malleolus. By applying gentle pressure with the transducer, the vein will collapse. The tibial nerve appears as a hyperechoic oval or circle immediately adjacent and posterior to the tibial artery.

Approach and Needle Trajectory: Position the patient’s leg in eversion. Either in-plane or out-of-plane technique can be used and the approach will be dependent on patient positioning and ergonomics.

Special Considerations: Color Doppler can be helpful in identifying the tibial artery. Tendons in the medial ankle (tibialis anterior, flexor digitorum longus, and flexor hallucis longus) can be mistaken for the tibial nerve, but noting that the tibial nerve is directly posterior and adjacent to the tibial artery will help to minimize misidentification. To reduce patient discomfort, use a small (25 or 27 gauge) needle for this block.

Lit Bit: A 49 year-old man with bilateral comminuted calcaneal fractures received bilateral ultrasound-guided posterior tibial nerve blocks with almost complete resolution of pain and tolerated splint placement without pain. (Clattenburg 2016)

TRUNCAL BLOCKS

Intercostal Nerve Block (Figure 16)

Block Distribution: Sensory blockade of the targeted anterolateral dermatome and the underlying parietal pleura. This block can be performed at the T1-T12 levels.

Block Volume: 3-5 mL per intercostal level

Uses in the Emergency Department: Pain control for rib fractures, analgesia prior to chest tube placement.

Probe Placement: Parallel to the posterior-axillary line at the level of the target intercostal nerve. Probe placement medial to the scapula with the patient in prone position has also been described. The advantage of this is that the intercostal nerve can be blocked prior to its division into the deep and lateral cutaneous branches (Stone 2011)

Sonographic landmarks: Identify the external, internal and innermost intercostal nerves between two ribs. The intercostal nerve, artery and vein are located at the caudal border of the rib between the internal and innermost intercostal muscle planes.

Approach and Needle Trajectory: In-plane, from caudal to cephalic, with the needle tip caudal to the inferior margin of the rib between the internal and innermost intercostal muscles.

Special Considerations: The parietal pleura lies immediately below the innermost intercostal muscle. To avoid causing a pneumothorax, extra care must be taken to avoid advancing the needle without clear needle tip visualization.

Lit Bit: A case report describes the case of a 39 year-old female with a traumatic right pneumothorax who received ultrasound-guided intercostal nerve blocks performed by an emergency physician for analgesia prior to placement of a tube thoracostomy. (Stone 2011)

Serratus Anterior Plane Block (Figure 17)

Block Distribution: This block targets the lateral cutaneous branches of the T3-T9 thoracic intercostal nerves.

Block Volume: 30-40 mL

Uses in the Emergency Department: Pain control for rib fractures, analgesia prior to chest tube placement.

Probe Placement: Transversely over the mid-axillary line at the level of the nipple (approximate location of the 5th rib) with the probe marker facing the nipple with the patient lying supine or in the lateral decubitus position with the injured side up. The probe may be rotated slightly in a clockwise fashion so that a better view of the ribs and pleura in cross-section can be obtained.

Sonographic landmarks: The serratus anterior is located between the pectoralis muscle anteriorly and the latissimus dorsi muscle posteriorly. The distal branches of the thoracic intercostal nerves are located in the fascial plane immediately superficial to the serratus anterior.

Approach and Needle Trajectory: In-plane, from anterior to posterior in the supine patient and from posterior to anterior in the lateral decubitus patient with the needle tip ending immediately superficial to the serratus anterior muscle.

Special Considerations: Because the long thoracic nerve and the thoracodorsal nerve are located in the fascial plane between the latissiumus dorsi and the serratus anterior, winging of the ipsilateral scapula is an expected effect of the block. Because the serratus anterior plane block is a high-volume block, it is especially important to be aware of the maximum recommended dosage in order to prevent local anesthetic systemic toxicity (LAST).

Lit Bit: Durant et al. describe the cases of a 82 year-old male and a 65 year-old female with multiple rib fractures in whom ultrasound-guided serratus plane blocks were successfully performed in the ED for pain control. Both patients had significant pain despite receiving IV opioids. After the block, the first patient’s pain score decreased from 8/10 to 0/10 and she did not request additional analgesics for >12 hours post-block. The second patient had 9/10 and reported “minimal pain” post-block and did not require additional analgesia for 10 hours. (Durant 2017)

Table 2: Summary of upper extremity, truncal, and lower extremity nerve blocks

Block Type	Volume of LA	Block Distribution	Indications
Cervical Plexus	10-15 mL	Skin of anterolateral neck, ear lobe, skin over clavicle	Ear lobe laceration, central venous catheter placement, clavicle fracture
Interscalene Brachial Plexus	10-20 mL	Clavicle, shoulder, upper lateral arm	Clavicle fracture, shoulder dislocation, humerus fracture
Supraclavicular Brachial Plexus	20-25 mL	Clavicle, shoulder, upper lateral arm	Shoulder dislocation, humerus fracture
Infraclavicular Brachial Plexus	20-30 mL	Arm below shoulder including hand. Excludes medial arm and proximal forearm	Elbow, wrist, and hand injuries. Complex laceration repair, incision and drainage of large abscess
Axillary Nerve	20-25 mL	Below mid arm including hand. Excludes skin over deltoid and lateral forearm and wrist.	Complex laceration repair, incision and drainage of large abscess
Median/Radial/Ulnar Nerve	5-10 mL	Each individual nerve below level of blockade	Complex laceration repair, incision and drainage of large abscess
Intercostal Nerve Block	3-5ml per intercostal level	Dermatome of the targeted thoracic level (T1-T12)	Rib fractures, chest tube placement
Serratus Plane Block	30-40ml	T3-T9 dermatomal distribution of the ipsilateral chest wall	Rib fractures, chest tube placement
Femoral Nerve	10-20 mL	Anterior and medial thigh to the knee and a variable component of the medial leg and foot	Hip fracture, femur fracture, knee injury, complex laceration repair, incision and drainage of large abscess
Fascia Iliaca Compartment	30-40 mL	Lateral, anterior and medial thigh to the knee and a variable component of the medial leg and foot	Hip fracture, femur fracture, knee injury, complex laceration repair, incision and drainage of large abscess
Popliteal Sciatic Nerve	20-30 mL	Leg below the knee except for a variable component of the medial leg and foot	Knee, leg, ankle and foot injury, complex laceration repair, incision and drainage of large abscess
Tibial Nerve	3-5 mL	Heel and plantar surface of foot	Foreign body removal, laceration repair

The editors thank Stephen Alerhand, MD, for his thoughtful review of the manuscript.

The authors report no relevant conflicts of interest.

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