Chapter 24

• Indications: thoracic or upper abdominal surgery, rib fractures, breast surgery
• Landmarks: angle of the rib (6–8 cm lateral to the spinous process)
• Needle insertion: Under the rib with approximately 20-30 cephalad angulation
• Target: needle insertion 0.5 cm past the inferior border of the rib
• Local anesthetic: 3–5 mL per intercostal level
• Complexity level: advanced

###### Figure 24-1.

Intercostal nerve block: Patient position and needle insertion.

Intercostal block produces discrete bandlike segmental anesthesia in the chosen levels. Intercostal block is an excellent analgesic option for a variety of acute and chronic pain conditions. The beneficial effect of intercostal blockade on respiratory function following thoracic or upper abdominal surgery, or following chest wall trauma, is well documented. Although similar in many ways to the paravertebral block, intercostal blocks are generally simpler to perform because the osseous landmarks are more readily palpable. However, the risks of pneumothorax and local anesthetic systemic toxicity are present, and care must be taken to prevent these potentially serious complications. Intercostal blocks can be more challenging to perform above the level of T7 because the scapula prevents access to the ribs. Although an intercostal block is an excellent choice for analgesic purposes, it is often inadequate as a complete surgical anesthesia. For this application, supplementation with another anesthesia technique usually is required.

After emerging from their respective intervertebral foramina, the thoracic nerve roots divide into dorsal and ventral rami (Figure 24-2). The dorsal ramus provides innervation to the skin and muscle of the paravertebral region; the ventral ramus continues laterally as the intercostal nerve. This nerve then pierces the posterior intercostal membrane approximately 3 cm lateral to the intervertebral foramen and enters the subcostal groove of the rib, where it travels inferiorly to the intercostal artery and vein. Initially, the nerve lies between the parietal pleura and the inner most intercostal muscle. Immediately proximal to the angle of the rib, it passes into the space between the innermost and internal intercostal muscles, where it remains for much of the remainder of its course. At the midaxillary line, the intercostal nerve gives rise to the lateral cutaneous branch, which pierces the internal and external intercostal muscles and supplies the muscles and skin of the lateral trunk. The continuation of the intercostal nerve terminates as the anterior cutaneous branch, which supplies the skin and muscles of the anterior trunk, including the skin overlying the sternum and rectus abdominis.

###### Figure 24-2.

Anatomy of the thoracic spinal and intercostal nerves.

Intercostal blockade results in the spread of local anesthetic along the intercostals sulcus underneath the parietal pleura, leading to ipsilateral anesthesia of the blocked intercostals levels (Figure 24-3). A larger volume of local anesthetic or more medial injection may result in backtracking of local anesthetic ...

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