Intercostal nerve blockade

Intercostal nerve block is quite simple and has wide clinical application as an additional measure of pain relief in the postoperative period and in case of rib fractures. It significantly facilitates respiratory care, promotes expectoration and reduces the frequency of postoperative complications.

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Indications for intercostal nerve block

Pain relief in the postoperative period during operations on the upper abdominal cavity, such as cholecystectomy using a Kocher incision, pain relief in the postoperative period during thoracic operations, pain relief for rib fractures, pain relief and muscle relaxation during thoracic operations in combination with general anesthesia.

Volume of local anesthetic - as a rule, anesthesia of several intercostal nerves is used, 2-3 ml of solution is administered to each segment in a total dose of up to 20-25 ml.

Anatomy

The intercostal nerves are formed from the ventral roots of the spinal nerves of the corresponding segment. They leave the paravertebral space and are directed to the lower border of the overlying rib. At first they are located between the pleura in front and the intercostal fascia behind, then penetrate into the space between m. intercos talis internus and m. intercostalis intimus. Here they divide into two or more branches that go in the intercostal space and supply the muscles and skin of the chest and abdominal wall. At the level of the midaxillary line, each intercostal nerve gives off a lateral cutaneous branch that supplies the skin of the posterolateral surface of the trunk. The upper six pairs end at the edge of the sternum, their branches innervate the skin of the anterior surface of the chest. The lower six pairs go beyond the border of the rib and supply the muscles and skin of the anterior chest wall. The lateral cutaneous branches penetrate the external intercostal muscles and divide into anterior and posterior branches, respectively innervating the lateral surface of the abdomen far beyond the rectus muscles and back. The cutaneous branches anastomose freely with each other, creating a wide zone of crossed innervation. However, most of the muscles and skin surface of the abdominal wall can be anesthetized by blocking the 6th to 12th intercostal nerves. Recently, the question of whether adjacent intercostal spaces are connected has been debated. At their origin, they are located between the pleura and the posterior intercostal fascia, there is nothing there to prevent the spread of the local anesthetic solution extrapleurally, capturing several adjacent nerves. Even with lateral injection at the level of the costal angle, the solution can reach the extrapleural space. Spread of the solution is facilitated by rib fractures, when it can even enter the pleural cavity. These considerations provide a rationale for injecting a large volume of local anesthetic from a single site in the hope that this will allow several adjacent intercostal nerves to be captured. However, the spread of the solution is unpredictable and to achieve a guaranteed result it is better to inject small volumes from several sites.

Position of the patient during intercostal nerve block

1. On the back, if the intercostal nerve block is planned at the midaxillary line. This is the most comfortable position. The arm is raised so that its hand is under the patient's head. The head is turned in the opposite direction.
2. On the side, if a unilateral block at the level of the angle of the ribs is planned.
3. On the stomach, with bilateral blockade of the intercostal nerves at the level of the angle of the ribs.

Landmarks:

• The ribs are counted from bottom to top, starting from the 12th;
• The corners of the ribs are located 7-10 cm lateral to the midline at the back;
• Midaxillary line.

Intercostal nerve block depends on the clinical situation. In case of rib fracture, the anesthetic is administered proximally near the fracture site. In case of intercostal nerve block in large quantities for postoperative analgesia or in addition to general anesthesia, it is performed at the level of the costal angle. This assumes the patient is in the lateral or prone position, although the anesthetic solution easily spreads over the intercostal space for several centimeters in both directions. Therefore, the intercostal nerves, including their lateral branches, can be easily blocked at the level of the midaxillary line when the patient is supine.

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How is an intercostal nerve block performed?

The intercostal nerve block does not depend on the level at which it is performed, at the midaxillary line or at the level of the costal angle. To prevent puncture of the pleural cavity, the tip of the needle should be as close to the surface of the rib as possible. The rib is held between the 2nd and 3rd fingers of the free hand. The needle, connected to a syringe with a local anesthetic solution, is inserted between the fingers and advanced until contact is made with the rib. The needle is directed towards the rib, deviating in the cephalic direction at an angle to the skin surface of approximately 20°. After contact is made with the rib, the tip of the needle goes down the surface of the rib, bypassing its lower edge so that the needle maintains the same angle of inclination. After this, the needle is inserted approximately 3 mm towards the inner surface of the rib. At the moment of puncture of the external intercostal fascia, a depression or "click" is felt. After this, the space between m. intercostalis interims and m. intercostalis intimus is injected with 3 ml of local anesthetic solution. Alternative blockade of intercostal nerves is aimed at preventing puncture of the pleural cavity, consists of inserting a needle almost parallel to the surface of the chest

The choice of local anesthetic depends on the specific conditions. Blockade of intercostal nerves in large quantities causes a high concentration of anesthetic in the blood, which can lead to a systemic toxic reaction, requires careful consideration of the administered dose. Most often used; lidocaine solution with the addition of adrenaline 1:200 000 or 0.5% bupivacaine also with the addition of adrenaline to reduce peaks; concentrations in blood plasma. The maximum dose should not exceed 25-30 ml.

Complications and measures to prevent them

A systemic toxic reaction is possible when performing intercostal nerve blockade in large quantities. Its prevention consists of taking into account the total dose administered, using anesthetics containing adrenaline, as well as general measures, including aspiration tests before each administration of the solution.

Pneumothorax may occur with accidental puncture of the inner pleural leaflet, and against the background of a rib fracture, it may be a consequence of trauma. The possibility of such a complication should always be kept in mind when blocking the intercostal nerves. In doubtful cases, diagnosis is based on chest X-ray data. Treatment depends on the volume and speed of air intake.

Intercostal nerve block is rarely complicated by infection provided that aseptic precautions are followed.

Hematoma: Avoid multiple needle insertions and use small diameter needles (25 gauge or less).

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