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Few surgical procedures can be performed with an intercostal block alone, and the application of these blocks in combination with other techniques has largely been supplanted by epidural blockade. However, in patients with contraindications to neuraxial blockade, these techniques can be used alone or combined with celiac plexus blocks and light general anesthesia to provide excellent surgical conditions for intra-abdominal procedures. In a similar fashion, intrathoracic surgery can be accomplished using intercostal and stellate ganglion blocks with endotracheal sedation.
Figure 44-27
A, Patient positioning
for an intercostal nerve block. B, The index finger
displaces the skin up over the rib. The needle is inserted at the tip of the finger
and rests on the rib. The needle is walked off the lower rib edge and inserted 3
to 5 mm. C, An intercostal nerve and its branches.
Interpleural catheter placement for management of postoperative pain was first described by Reiestad and Stromskag in 1986.[62] Enthusiasm for this technique has waxed and waned. The mechanism of action is poorly understood, and reports of efficacy vary. Overall, the results with cholecystectomy have been most favorable.[63] [64] The advantages of interpleural analgesia are more difficult to prove in patients undergoing thoracotomy, perhaps because of technical problems relating to blood in the pleural space, chest tube drainage, and pleural disease.[65] [66] [67]
The intercostal nerves are the primary rami of T1 through T11. T12 is technically a subcostal nerve and supplies branches to the ilioinguinal and iliohypogastric nerves. Fibers from T1 contribute to the brachial plexus; T2 and T3 provide a few fibers to the formation of the intercostobrachial nerve, which supplies the skin of the medial aspect of the upper arm. Each intercostal nerve has four branches: the gray ramus communicans, which passes anteriorly to the sympathetic ganglion; the posterior cutaneous branch, supplying skin and muscle in the para-vertebral area; the lateral cutaneous branch, arising just anterior to the midaxillary line and sending subcutaneous branches anteriorly and posteriorly; and the anterior cutaneous branch, which is the termination of the nerve ( Fig. 44-27C ).
Medial to the posterior angles of the ribs, the intercostal nerves lie between the pleura and the internal intercostal fascia. At the posterior angle of the rib, the nerve lies in the costal groove accompanied by the intercostal vein and artery.
The intercostal nerve can be readily blocked at the angle of the rib just lateral to the sacrospinalis muscle group. The patient is placed in the prone position with a pillow placed under the abdomen to reduce the lumbar curve (see Fig. 44-27A ). A line is drawn along the posterior vertebral spines. Nearly parallel lines are drawn along the posterior angles of the rib, which can be palpated 6 to 8 cm from the midline. These lines angle medially at the upper levels to prevent overlying of the scapula. The inferior edge of each rib is palpated and is marked on the line intersecting the posterior angle of the rib. After appropriate skin preparation, skin wheals are injected at each of these points. A 22-gauge, short-bevel, 4-cm needle is attached to a 10-mL syringe. Beginning at the lowest rib, the index finger of the left hand displaces the skin up over the patient's rib. The needle is inserted at the tip of the finger until it rests on the rib. The fingers of the left hand are shifted to grasp the needle hub firmly. The left hand then walks the needle 3 to 5 mm off the lower rib edge, where 3 to 5 mL of local anesthetic is injected (see Fig. 44-27B ). This process is repeated at each rib. Appropriate intravenous sedation providing analgesia and some degree of amnesia is desirable for the patient's comfort.
Alternatively, intercostal block can be performed in the supine patient at the midaxillary line. Theoretically, the lateral cutaneous branch of the nerve can be missed, but CT studies show that injected solutions spread several centimeters along the costal groove.[68] Further injection of 1 to 2 mL of solution as the needle is withdrawn blocks the subcutaneous branches.
The technique for interpleural catheter placement is quite simple and can be performed with the patient in a lateral (and slightly oblique) or sitting position. The sixth or seventh intercostal space is identified. Needle insertion is performed about 10 cm lateral from the posterior midline, and an epidural needle tip is advanced until it rests on the cephalad edge of the rib below the intercostal space to be entered. A glass syringe filled with saline or air is then attached to the needle, and the unit is advanced slowly over the superior edge of the rib. When the tip of the needle enters the parietal pleura, the solution in the syringe is drawn into the chest cavity because of the negative intrathoracic pressure. This effect can be observed in mechanically and in spontaneously ventilating patients, but it is accentuated in the latter group.
The catheter is then inserted approximately 5 to 8 cm into the interpleural space and is secured on the chest wall. During needle positioning and catheter placement, care must be taken to minimize entrainment of air through the needle. Lung parenchymal damage can occur with loss-of-resistance techniques or insertion of excessive lengths of catheter.
The major complication feared with intercostal blockade is pneumothorax. The actual incidence, however, was as low as 0.07% in a large series performed by anesthesiologists at all levels of training. Routine postoperative chest radiographs showed an incidence of nonsymptomatic pneumothorax of 0.42%.[69] If this unusual complication occurs, treatment is usually limited to observation, administration of oxygen, or needle aspiration. Rarely, chest tube drainage is required when these treatments are unsuccessful.
The risk of systemic local anesthetic toxicity is present with multiple intercostal blocks because of the large volumes and rapid absorption of the solutions. Use of epinephrine has been shown to decrease blood levels. Patients should be monitored and observed carefully during the block and for at least 20 to 30 minutes afterward. Interpleural block should not be performed in patients with pleural fibrosis or inflammation, pleural effusion, lung parenchymal disease associated with pleural disease, or bleeding diathesis. Pleural disease can result in poor spread of local anesthetic solutions or rapid uptake in the case of inflammation. Patients with severe pulmonary disease who rely on their intercostal muscles may evidence respiratory decompensation after bilateral intercostal blockade.[70]
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