Intercostal blocks provide analgesia following tho-racic and upper abdominal surgery, and relief of pain associated with rib fractures, herpes zoster, and cancer. These blocks require individual injections delivered at the various vertebral levels that corre-spond to the area of body wall to be anesthetized.Intercostal blocks result in the highest blood levels of local anesthetic per volume injectedof any block in the body, and care must be taken to avoid toxic levels of local anesthetic. The intercostal block has one of the highest complication rates of any peripheral nerve block due to the close proxim-ity of the intercostal artery and vein (intravascular local anesthetic injection), as well as underlying pleura (pneumothorax). In addition, duration is impressively short due to the high vascular flow, and placement of a perineural catheter is tenuous, at best. With the advent of ultrasound guidance, the paravertebral approach is rapidly replacing the intercostal approach.
The intercostal nerves arise from the dorsal and ventral rami of the thoracic spinal nerves. They exit from the spine at the intervertebral foramen and enter a groove on the underside of the correspond-ing rib, running with the intercostal artery and vein; the nerve is generally the most inferior structure in the neurovascular bundle (Figure 46–61). Branches are given off for sensation in a single dermatome from the midline dorsally all the way to across the midline ventrally.
With the patient in the lateral decubitus or supine position, the level of each rib in the mid and posterior axillary line is palpated and marked.
A small-gauge needle is inserted at the inferior edge of each of the selected ribs, bone is con-tacted, and the needle is then “walked off ” inferi-orly (Figure 46–61). The needle is redirected in a slightly cephalad direction and advanced approxi-mately 0.25 cm. Following aspiration, observing for blood or air, 3–5 mL of local anesthetic is injected at each desired level.
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