Intercostal Nerve Block: Ultrasound-Guided Technique

• Surgical anesthesia (as an adjunct to general anesthesia)
• Thoracic procedures, including chest tube placement
• Abdominal procedures, particularly in the upper abdomen, such as cholecystectomy
• Post-surgical analgesia, including post-sternotomy pain
• Trauma pain
• Rib fractures
• Flail chest
• Chest tube pain

• Absolute contraindications
• Patient refusal
• Allergy to local anesthetics
• Infection at the injection site
• Relative contraindications
• Coagulopathy or anticoagulation
• Severe pulmonary dysfunction
• Sepsis
• Uncooperative patient

• Note: Technique described is for ultrasound-assisted (US) intercostal nerve block.
• Sterile gloves and mask
• Sterile surgical prep solution, such as Betadine
• Sterile fenestrated drape or sterile towels
• Local anesthetic (e.g., 2% lidocaine, 0.5% bupivacaine)
• 20-mL sterile syringe, sterile extension tubing, and 21-gauge x 50 mm needle for intercostal local anesthetic injection
• 5-mL sterile syringe with 25-gauge or 30-gauge short needle for local anesthetic subcutaneous infiltration
• Ultrasound machine and 6-13 MHz linear transducer
• Sterile US gel

The sensory innervation of the trunk from the posterior axillary line to the midline is derived from the ventral rami of the first thoracic nerve to the first lumbar nerve.^2,3 With the exception of T12 (the subcostal nerve) and L1, the intercostal nerves (T1-T11) arise from the ventral rami of their respective nerve roots and then travel anteriorly in a groove beneath their respective ribs to lie between the internal intercostal muscle and the innermost intercostal muscle. In this groove, the intercostal vein lies uppermost, with the intercostal artery and nerve lying inferiorly. The intercostal nerve gives off a sensory branch in the midaxillary line that provides variable innervation from the posterior axillary line anteriorly. The nerve then continues forward as the anterior cutaneous branch. The anterior cutaneous branches of T6-11 enter the transversus abdominis plane of anterior abdominal wall and supply the skin, muscles, and parietal peritoneum in the abdomen.

The subcostal nerve (T12) is also derived from the ventral ramus of its respective nerve root. It enters the plane between the internal oblique muscle and the transversus abdominis muscle and gives off a lateral cutaneous branch in the midaxillary line. The lateral cutaneous branch of the subcostal nerve crosses the iliac crest between 2 and 5 cm posterior to the anterior superior iliac spine and is readily injured during a variety of surgeries.^4,5 The subcostal nerve joins the L1 nerve in the transversus abdominis plane to form the ilioinguinal and iliohypogastric nerves. Many variations in the origin and location of these nerves have been described in both cadaveric and in vivo studies, and providing a generic anatomic description of these structures would be erroneous.^6,7 This variation in anatomy explains a failure rate of up to 25% reported with traditional approaches to ilioinguinal/iliohypogastric nerve blocks.⁸

The important surface anatomic landmarks are¹:

Ultrasound Anatomy

The chest wall is best imaged in a coronal (vertical) plane. The relevant intercostal space is visualized by using a 6-13 MHz linear transducer. The ribs appear as dense dark oval structures with a bright surface (periosteum). A dark shadow is cast deep to the rib on ultrasound, illustrating the phenomenon of echo shadowing. Echo shadowing is an echo-free zone immediately behind a structure of high absorbance or reflectivity such as bone, calculi, or metal prosthesis. The pleura and lungs are visualized deep to the intercostal space between the echo shadows.

• Patients should be monitored for at least 20-30 minutes following intercostal nerve blocks for symptoms or signs of local anesthetic toxicity
• Observe for development of hematoma or infection at the insertion site.
• Development of cough, shortness of breath, low oxygen saturation. or wheezing may indicate the presence of pneumothorax.

• Pneumothorax
• Hematoma
• Nerve injury
• Local anesthetic toxicity