Emergency Medicine Hub / Procedures & Anesthesia • 3 min read • 3 sections

Emergency Regional Anesthesia, Ultrasound-Guided Nerve Blocks & LAST

Comprehensive guide to bedside regional anesthesia in the ED: facial nerve blocks (infraorbital, mental, inferior alveolar dental block), upper extremity blocks (supraclavicular, axillary, forearm, digital), trunk and hip blocks (PENG, Fascia Iliaca, Serratus Anterior, Erector Spinae), lower extremity blocks, and Local Anesthetic Systemic Toxicity (LAST) 20% lipid emulsion resuscitation.

Resuscitation Quick Actions • First 2 Minutes

High-Acuity

Fascia Iliaca Compartment Block (FICB)

Indicated for hip fractures and femoral shaft fractures. High-frequency linear ultrasound probe positioned in inguinal crease. Inject 30-40 mL of dilute local anesthetic (0.2% ropivacaine or 0.25% bupivacaine) under the fascia iliaca and lateral to the femoral nerve; anesthetic spreads proximally to block femoral, lateral femoral cutaneous, and obturator nerves.

Pericapsular Nerve Group (PENG) Block

Targets articular sensory branches of femoral and accessory obturator nerves on the anterior hip capsule (iliopubic eminence). Provides superior hip analgesia while preserving quadriceps motor strength (no motor blockade).

Serratus Anterior Plane (SAP) Block

Indicated for multiple rib fractures (ribs 2-9) and chest tube placement. Inject 20-30 mL of 0.25% bupivacaine either superficial or deep to the serratus anterior muscle at the 4th-5th intercostal space mid-axillary line.

Inferior Alveolar Nerve Block (Dental)

Landmark block for mandibular tooth fractures, pulpitis, or lower lip lacerations. Palpate pterygomandibular raphe; inject 1.5-2 mL 2% lidocaine with epinephrine into mandibular sulcus near lingula; anesthetizes mandibular teeth, lower lip, and chin.

Maximum Doses of Local Anesthetics

Lidocaine plain 4.5 mg/kg (max 300 mg); Lidocaine with epinephrine 7 mg/kg (max 500 mg); Bupivacaine plain 2.5 mg/kg (max 175 mg); Bupivacaine with epinephrine 3 mg/kg (max 225 mg).

LAST Resuscitation (20% Lipid Emulsion)

Bolus 1.5 mL/kg IV over 1 min (approx 100 mL in 70 kg adult). Follow immediately with continuous infusion 0.25 mL/kg/min (approx 18 mL/min). Repeat bolus up to 2 times for refractory arrest. Avoid vasopressin, high-dose epinephrine (use <1 mcg/kg boluses), and calcium channel/beta-blockers.

Dental/Inferior Alveolar

Landmark block inside mouth for mandibular tooth anesthesia.

Bottom-Line Clinical Pearl

Ultrasound-guided regional anesthesia provides opioid-sparing analgesia for severe orthopedic and thoracic trauma. For hip and femoral neck fractures, the Fascia Iliaca Compartment Block (FICB) and Pericapsular Nerve Group (PENG) block offer profound pain relief. Always have 20% Intralipid immediately accessible whenever administering high-volume regional blocks.

CRITICAL RESUSCITATION: LAST (Local Anesthetic Systemic Toxicity) Protocol

Accidental intravascular injection or rapid systemic absorption of local anesthetics causes CNS excitement (tinnitus, metallic taste, seizures) followed rapidly by refractory cardiovascular collapse (wide QRS, asystole, PEA). Management:

1. Stop local anesthetic injection immediately. Call for help and obtain the LAST rescue kit (20% Lipid Emulsion/Intralipid).

2. Airway & Seizures: 100% O2, hyperventilate (acidosis worsens toxicity), treat seizures with benzodiazepines (midazolam 2-4 mg IV; avoid propofol in shock).

3. 20% Lipid Emulsion: Bolus 1.5 mL/kg IV over 1 minute (~100 mL). Start infusion at 0.25 mL/kg/min. If no ROSC, re-bolus 1-2 times and double infusion to 0.5 mL/kg/min (maximum total dose 12 mL/kg over first hour).

High-Yield ED Ultrasound-Guided Nerve Blocks

Block Name	Anatomical Target & Needle Approach	Nerves Anesthetized	Clinical Indications
Fascia Iliaca Compartment Block (FICB)	High-frequency linear probe in transverse orientation below inguinal ligament; needle in-plane from lateral to medial, penetrating fascia iliaca	Femoral, Lateral Femoral Cutaneous, and Obturator nerves	Femoral neck and intertrochanteric fractures, femoral shaft fractures, hip dislocations
PENG (Pericapsular Nerve Group) Block	Curvilinear/linear probe over anterior inferior iliac spine (AIIS) and iliopubic eminence; needle in-plane deep to psoas tendon on bony cortex	Articular branches of femoral, obturator, and accessory obturator nerves	Hip fractures; provides profound analgesia WITHOUT motor weakness, enabling early physical therapy
Serratus Anterior Plane (SAP) Block	Linear probe at 4th-5th rib mid-axillary line; needle in-plane injecting between latissimus dorsi and serratus anterior or deep to serratus anterior	Lateral cutaneous branches of thoracic intercostal nerves T2-T9	Multiple rib fractures, flail chest, tube thoracostomy placement, thoracic wall contusions
Erector Spinae Plane (ESP) Block	Linear/curvilinear probe sagittal over thoracic transverse process (T4-T5); needle deep to erector spinae muscle on bony acoustic shadow	Dorsal and ventral rami of thoracic spinal nerves	Posterior rib fractures, thoracic trauma, herpes zoster, pancreatitis/abdominal wall pain
Superficial Cervical Plexus Block	Linear probe at midpoint of posterior border of sternocleidomastoid muscle (SCM); inject 5-10 mL under investing fascia	Lesser occipital, great auricular, transverse cervical, supraclavicular nerves (C2-C4)	Clavicle fractures, ear lacerations, anterior neck laceration repairs
Posterior Tibial Nerve Block	Linear probe transverse behind medial malleolus; inject 3-5 mL adjacent to posterior tibial artery	Posterior tibial nerve	Plantar foot lacerations, sole foreign bodies, calcaneal fractures (anesthetizes entire sole of foot)

Head & Face Landmark Regional Anesthesia

Infraorbital Nerve Block (V2): Palpate infraorbital foramen (in line with pupil, 1 cm below inferior orbital rim). Approach intraorally by piercing labial mucosa above canine/first premolar and advancing 1-1.5 cm; inject 2-3 mL 1-2% lidocaine. Anesthetizes lower eyelid, lateral nose, cheek, and upper lip without distorting wound margins.
Mental Nerve Block (V3): Palpate mental foramen (between first and second lower premolars). Approach intraorally piercing mucosa in labial sulcus; inject 2-3 mL. Anesthetizes lower lip and chin.
Inferior Alveolar Nerve Block: Place thumb in coronoid notch of anterior mandibular ramus. With syringe originating from contralateral premolars, enter mucosa 1 cm above occlusal plane into pterygomandibular space; aspirate (avoid inferior alveolar artery!) and inject 1.5-2 mL. Anesthetizes all ipsilateral mandibular teeth, anterior two-thirds of tongue, and floor of mouth.

Regional Anesthesia Pitfalls

Injecting against high resistance: Intraneural injection causes severe neurological injury; never inject if high opening resistance (>15 psi) is felt or if the patient reports electric lancinating paresthesias.
Failing to aspirate before injecting: Always perform intermittent gentle aspiration every 3-5 mL of local anesthetic to prevent accidental intravascular injection into major arteries/veins.

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