Ovid: Peripheral Nerve Blocks: A Color Atlas

Intercostal Block

Barry F. Bass

Patient Position: Prone, with a pillow under the mid-abdomen and the arms hanging over the sides of the table to rotate the scapula laterally.

Indications: Analgesia for thoracic and upper abdominal surgery, analgesia for rib fracture and to facilitate ventilation in flail chest, and treatment of neuropathic pain such as postherpetic neuralgia and cancer-related pain syndromes. Can also be used as a diagnostic procedure to differentiate neuropathic pain from visceral pain.

Needle Size: 22-gauge, 35-mm needle.

Volume: 0.2% ropivacaine or 0.25% bupivacaine with 1/200,000 epinephrine, 3 to 5 mL per rib.

Anatomic Landmarks: Construct a vertical line joining the spinous processes of the thoracic vertebra corresponding to the nerves to be blocked. Palpate the edge of the sacrospinalis muscle and mark the lateral edge. The muscle will become broader as it extends caudad. A line is drawn along the edge of the muscle. The inferior border of the rib is marked and extended to bisect the line marking the lateral border of the muscle. The distance from the inferior border of the rib to the pleura is about 5 mm (Fig. 20-1).

Approach and Technique: Skin wheals are raised over the area to be blocked with 1% lidocaine. For a right-handed operator, the left index finger is placed over the skin wheal and the skin is retracted cephalad (Fig. 20-2A). The needle is advanced perpendicularly onto the rib. The needle is grasped between the index finger and thumb of the operator's left hand. Resting the hypothenar eminence against the patient's paraspinal muscle steadies the left hand. The needle is now slowly and methodically walked off the rib in a caudal direction (Fig. 20-2B). Once off the inferior border of the rib, the needle is slowly advanced into the neurovascular sheath, which should lie no more than 8 mm below the upper border of the rib. A slight “pop” may be felt as the needle enters the sheath. After aspiration, 3 to 5 mL of local anesthetic solution is injected at each level. The procedure is repeated at each level to be blocked.

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Figure 20-1. Anatomic landmarks.

Tips

If the patient is unable to lie in the prone position, the lateral position, with the arm on the side to be blocked rotated over the head, is acceptable.
Use fluoroscopy whenever available to ascertain accuracy of needle placement and thus avoid pneumothorax.
This approach ensures block of the lateral cutaneous branch of the intercostal nerve.
The use of light sedation is encouraged to provide a quiet operating field, especially in patients who are being ventilated.

Figure 20-2. A: The index finger is placed over the skin wheal and the skin is retracted. B: The needle is slowly and methodically walked off the rib.

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Figure 20-3. Procedure done under fluoroscopy.
Use an extension tube on the syringe to provide better control and thus steady the injecting hand.
Keep notes of volumes injected to prevent systemic toxicity and epinephrine overdose.
Following multiple-level blocks, postblock chest x-ray is recommended. Pneumothorax is a complication in 1% to 2% of cases.
If more than three levels are to be blocked or if analgesia for periods over 8 to 12 hours is requested, the continuous paravertebral approach is suggested.
A short rigid-walled catheter connecting the needle and syringe takes weight off the needle and can allow the injection to be done by an assistant, allowing the operator more control of the needle.
If the procedure is done under fluoroscopy, injection of 1 mL of contrast will confirm placement of the needle within the neurovascular space (Fig. 20-3).