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Intercostal nerves supply major parts of the skin and musculature of the chest and abdominal wall.
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Intercostal nerve block is now commonly performed for treatment of acute and chronic pain conditions affecting the thorax and upper abdomen.
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Intercostal nerve block provides excellent analgesia for chest trauma such as rib fractures and after chest and upper abdominal surgeries.
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Ultrasound provides the safest and most successful way for intercostal nerve blocks.
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The online technique is the preferred way for performing the block.
Sonoanatomy
There are three layers of intercostal muscles: external, internal, and innermost intercostal muscles, which are all incomplete, thin layers of muscle and tendinous fibers. The neurovascular bundle lies between the internal and innermost intercostal muscles in the costal groove. Of note, the neurovascular bundle lies midway between the ribs in the majority of cases. The use of ultrasound allows the visualization of the pleura and the different layers of the intercostals. The pleura will be easily identified as a hyperechoic line that glides with respiration (sliding sign).
Technique
A linear probe with high resolution (6–13 Hz) is used for the technique. The patient can be placed in prone position, sitting position, or lateral position with the side to be blocked facing upward. The angle of the rib, which is 6–7.5 cm from the spinous process or on the lateral edge of the paraspinal muscle, is the common site of injection as the rib is the thickest at this site and the intercostal nerve has not yet branched. The probe is usually placed in the short axis to the ribs, so the two consecutive ribs are in view. The probe can also be placed in the long axis of the consecutive ribs, the author’s preferred technique. Both in-plane and out-of-plane techniques could be used for intercostal nerve block. The author prefers the in-plane technique as the complete needle path can be visualized. The needle is advanced under real time ultrasound guidance until the tip is positioned between intercostal and innermost intercostal muscles. After proper positioning of the needle 4–5 mL of local anesthetic is usually injected for each intercostal space ( Figs. 32.1A,B–32.3 ).
