Intercostal blockade is used to treat pain from herpes zoster, rib fractures, and intercostal neuropathies. It is also used to diagnose unusual abdominal or chest wall pain.
After informed consent is obtained, the patient is placed in either the prone or lateral position. In the lateral position, the injection site is along the midaxillary line, which may result in incomplete blockade of the lateral cutaneous branch of the intercostal nerve. In the prone position, the injection site is along the angle of the rib posteriorly. The ribs to be injected are marked at the angle of the rib or along the midaxillary line. If the ribs are not easily palpated, an alternative injection technique such as an epidural or root block may be considered. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and strict sterile technique is used throughout the procedure. The index finger of the nondominant hand is used to palpate the rib and identify the intercostal space. The tip of the finger is placed in the intercostal space and the skin slid over the superior rib. A 5 8-in. (1.5-cm), 25-gauge needle is inserted directly over the rib until contact is made with the rib. The long axis of the needle and syringe should have a slight cephalad tilt and be perpendicular to the long axis of the rib. The needle is then moved to the inferior edge of the rib by walking (i.e., repeatedly slightly withdrawing) the needle in the subcutaneous tissue and allowing the skin to move back slowly to its original position. The needle should retain its slight cephalad tilt. As the needle slips off the inferior ridge of the rib, the tip is advanced about 3 mm and then aspirated. If aspiration is positive for blood or air, the needle should be repositioned; otherwise, 2 to 5 mL of local anesthetic is injected to block the intercostal nerve (Fig. 67-6).
FIGURE 67-6. Intercostal nerve block. Approach for intercostal nerve injection and neural blockade with injection sites marked at the angle of the rib. A: The tip of the finger is placed in the intercostal space and the slid (arrow) slid over the superior rib. B: The needle is inserted directly over the rib until contact is made. C: The needle is walked (arrow) to the inferior edge of the rib while maintaining a slight cephalad tilt. D: As the needle slips off the inferior edge of the rib, advance the needle approximately 3 mm (arrow), where it is adjacent to the intercostal nerve.
A new needle should be used for each nerve blocked. Intercostal blocks are a simple and effective method of providing analgesia for painful disorders of the chest and abdominal walls. Because of the wide distribution of intercostal nerve innervation, the intercostal nerves above and below the level of pain must be blocked to gain optimal pain relief.
Intercostal blockade is often underused because of an exaggerated fear of pneumothorax. In actuality, less than 1% of all patients having an intercostal block develop a pneumothorax. Most can be easily treated with administration of supplemental oxygen and close observation and, when necessary, needle aspiration of air. Only those pneumothoraces that result in significant dyspnea or those under tension require chest tube thoracotomy and vacuum drainage. Local anesthetic toxicity can occur because of the rapid absorption after intercostal injection. Toxicity can easily be avoided by limiting the total amount injected to a known, safe level (see Table 67-4).