Serratus Anterior Nerve Block

1. See Also
   1. Regional Anesthesia
   2. Erector Spinae Plane Block
2. Indications
   1. Rib Fracture related pain
   2. Regional Anesthesia for Chest Tube Placement
   3. Axillary abscess drainage
   4. Intractable regional pain (e.g. Herpes Zoster)
3. Contraindications
   1. See Regional Anesthesia
4. Preparation: Anesthetic
   1. Bupivacaine
      1. Limit Bupivacaine max dose to 2.5 mg/kg or 175 mg for a 70 kg person (risk of LAST Reaction)
         1. Bupivacaine 0.5% concentration is 5 mg/ml (for a 70 kg person, max of 35 ml Bupivacaine 0.5%)
         2. Bupivacaine 0.25% concentration is 2.5 mg/ml (for a 70 kg person, max of 70 ml Bupivacaine 0.25%)
   2. Dilute in Saline
      1. Combine Bupivacaine and Normal Saline for a total volume of 30 ml
5. Preparation: Other Materials
   1. Linear, high frequency Ultrasound probe
      1. Sterile Ultrasound cover (gel inside of cover) and sterile gel over surface
      2. Position Ultrasound machine on opposite side of patient
   2. Needles (choose one)
      1. Specific Nerve Block needle (magnetized, more easily seen on Ultrasound)
      2. Blunt tipped spinal needle with IV Line extension tubing
   3. Syringe (30 ml)
   4. Second operator to inject Anesthetic
      1. First operator will hold needle in position
   5. Skin Preparation
      1. Chlorhexidine (Hibiclens)
      2. Povidone Iodine (Betadine)
   6. Sterile Gloves
6. Technique: Ultrasound Guided Serratus Anterior Nerve Block
   1. Images
      1. 
   2. Landmarks: Serratus Anterior insertion site
      1. Identify rib spaces 4-5 at mid-axillary line (Nipple line in men)
      2. Ultrasound appearance (from superficial to deep)
         1. Skin
         2. Latissimus Dorsi Muscle
         3. Serratus Anterior Muscle
         4. Ribs (shadowing) interspersed with intercostal Muscles
   3. Patient positioning: Lateral decubitus with unaffected side down (preferred)
      1. Arm on affected side positioned out of the way
      2. Ultrasound probe placed in horizontal, transverse position over landmark
      3. Needle directed inline toward table and medial chest
   4. Patient positioning: Supine
      1. Arm on affected side raised overhead
      2. Ultrasound probe placed in horizontal, transverse position over landmark
      3. Needle directed inline toward lateral chest
   5. Needle Insertion
      1. Direct needle toward a rib (acts as a stop in case of patient movement)
      2. Injection while inserting needle (hydrodissection) identifies the needle tip location on Ultrasound
   6. Injection Depth
      1. Injection depth is typically taught to be between Latissimus Dorsi Muscle and Serratus Anterior Muscle
      2. However injection may be placed either superficial or deep to the serratus anterior
         1. Superficial surface is preferred to avoid Pneumothorax
      3. Latissimus dorsi junction is used only as an Ultrasound landmark to identify serratus anterior
         1. However, serratus anterior is easily identified overlying the ribs in the axilla
         2. Injection may be anywhere along the serratus anterior surface to provide effective plane block
   7. Anesthetic Injection
      1. Slowly inject between Latissimus Dorsi Muscle and Serratus Anterior Muscle
      2. Creates a hypoechoic collection of fluid along the planar surface of the Serratus Anterior Muscle
7. Complications
   1. See Regional Anesthesia
   2. Pneumothorax
8. Resources
   1. Ultrasound Guided Serratus Anterior Blocks (Stat Pearls)
      1. https://www.ncbi.nlm.nih.gov/books/NBK538476/
   2. Serratus Plane Block for Rib Fractures (Highland Ultrasound)
      1. http://highlandultrasound.com/rib-fractures
9. References
   1. (2022) HQMedED Regional Anesthesia for Acute Care Providers, Minneapolis, MN, attended 6/3/2022
   2. Avila in Herbert (2020) EM:Rap 20(8); 1
   3. Karsh (2021) CRit Dec Emerg Med 35(3):9