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Thoracic paravertebral blockade.

, medical expert
Last reviewed: 04.07.2025
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Thoracic paravertebral block is a technique that involves the injection of local anesthetic into the areas of the thoracic spinal nerves emerging from the intervertebral foramen with ipsilateral somatic and sympathetic nerves. The resulting anesthesia or analgesia is similar to a "unilateral" epidural anesthesia. The level of block is chosen to achieve a unilateral, strip-like, segmental block at the desired extent without significant hemodynamic changes. Paravertebral blocks are among the simplest and most time-effective of all block techniques, but are also the most difficult to learn because they require complex spatial maneuvers during needle advancement. They require some "mechanical" or metric thinking. Paravertebral blocks are most often used in breast (mastectomy, cosmetic surgery) and thoracic surgeries.

Indications

Paravertebral block is indicated for breast surgery, pain relief after thoracic surgery or rib fractures.

Landmarks

  • Spinous process at the level of the corresponding thoracic dermatomes
  • Needle insertion: 2.5 cm lateral to the midline.
  • The final goal is to insert the needle 1 cm deeper than the transverse process.
  • Local anesthetic: 3-5 ml per level.

Anatomy

The thoracic paravertebral space is a wedge-shaped area that is located on both sides of the spinal column. Its walls are formed by the parietal pleura anterolaterally, the vertebral body, intervertebral disc, and intervertebral foramen medially, and the superior costotransverse process posteriorly. In the paravertebral space, the spinal nerves are organized into small bundles embedded in fatty tissue. At this level, they do not have a thick fascial sheath, so they are relatively easily blocked by the administration of local anesthetic.

The thoracic paravertebral space communicates with the intercostal space laterally, with the epidural space medially, and with the paravertebral space on the opposite side via the prevertebral fascia. The mechanism of action of the paravertebral block is the direct penetration of the local anesthetic into the spinal nerve, its distribution laterally along the intercostal nerve, and medially through the intervertebral foramen.

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Anesthesia zone

Thoracic paravertebral block is accompanied by ipsilateral anesthesia of the corresponding dermatome. The final picture of dermatomal distribution of anesthesia is a function of the level of the block and the volume of local anesthetic administered.

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Position of the patient

The paravertebral block is performed with the patient in a specific position. The patient is positioned in a sitting or lateral recumbent position, supported by the anesthesiologist's assistant. The back is arched forward (kyphosis), similar to the position required for neuraxial anesthesia. The patient's feet are placed on a stool to create a more comfortable position and a greater degree of kyphosis. This increases the distance between adjacent transverse processes and facilitates needle advancement without contact with bony structures.

Equipment for paravertebral blockade includes:

  • a set of sterile diapers and gauze napkins;
  • 20 ml syringes with local anesthetic;
  • sterile gloves, marker and surface electrode,
  • a disposable needle with a diameter of 25 gauge for skin infiltration, a spinal needle - 10 cm long and 22 gauge in diameter, Quincke or Tuohy type.

Paramedian line located 2.5 cm lateral to the midline.

It should be noted that marking the position of each transverse process at the level to be blocked is at best a rough approximation. From a practical standpoint, it is best to mark the midline and draw a line 2.5 cm lateral to it. All needle insertion points are located on this line. Once the first two transverse processes are identified, the others will follow at the same distance.

How is paravertebral block performed?

Infiltration of the skin and subcutaneous tissue. After treating the skin with an antiseptic solution, 6-8 ml of a diluted local anesthetic solution is injected subcutaneously along the designated paramedian line. The solution is injected slowly to avoid pain during injection. The needle should be reinserted into the already anesthetized skin area. Additional administration of a vasopressor helps prevent leakage of ichor at the injection site. When performing a paravertebral block of more than 5-6 levels (for example, with a bilateral block), it is preferable to use chloroprocaine or lidocaine for skin infiltration to reduce the total dose of long-acting local anesthetic.

Insertion of the needle. The needle is inserted perpendicular to the skin. Attention must be paid to depth and medial-lateral orientation at all times. Particular care must be taken to avoid a medial direction (risk of epidural or intrathecal injection). After contact with the transverse process, it is pulled toward the skin and redirected upward or downward to avoid it.

The ultimate goal is to pass the needle 1 cm below the level of the transverse process. Some "drop" may be felt as the costotransverse ligament is passed, but this can be taken into account as an anatomical landmark. The procedure essentially consists of three maneuvers:

  1. Make contact with the transverse process of the given vertebra and note the depth at which this contact is obtained (usually 2-4 cm).
  2. Pull the needle to skin level and to the right 10 degrees caudally or cephalad. 3). Bypass the transverse process, insert the needle 1 cm deeper and inject 4-5 ml of local anesthetic.

The needle should be directed to "go around" the transverse process either superiorly or inferiorly. At the level of Th7 and below, it is recommended to "go along the transverse process" to reduce the risk of intrapleural needle insertion. Correct paravertebral block and needle insertion are important for both accuracy and safety. Once contact is made with the transverse process, the needle is gripped so that the fingers holding it allow the insertion to be limited to 1 cm from the current position of the needle.

The midline connecting the spinous processes, the paravertebral line located 2.5 cm lateral to the midline, the lower angle of the scapula - corresponds to level Th7.

Some authors suggest using a technique based on loss of resistance to identify the paravertebral space, but such a change in resistance is very subtle and uncertain at best. For this reason, it is better not to stop paying attention to the loss of resistance, but to carefully measure the distance from the skin to the transverse process and simply advance the needle 1 cm deeper.

Never direct the needle medially because of the risk of inserting it into the intervertebral foramen and injuring the spinal cord. Use common sense when advancing the needle. The depth at which contact with the transverse processes is determined depends on the patient's body type and the level of the paravertebral block. The deepest contact with the transverse process is at the high thoracic (T1-T2) and low lumbar (L1-L5) levels, where it is 6 cm deep in a patient of average build. The closest contact to the skin is at the mid-thoracic (T5-T10) level, about 2-4 cm. Never disconnect the needle from the tubing of the local anesthetic syringe during the entire procedure. Instead, use the three-position stopcock to switch from one syringe to the other.

Choosing a Local Anesthetic

Paravertebral blockade uses drugs with a long action.

If anesthesia of the lower lumbar segments is not planned, paravertebral block is not accompanied by a motor block of the limb and does not affect the patient's ability to walk and care for himself.

In addition, relatively small volumes injected at multiple levels do not pose a threat to the general resorptive action of the local anesthetic. In patients undergoing extensive paravertebral block at multiple levels, alkalized chloroprocaine may be preferred for skin infiltration to reduce the total dose of the more toxic, long-acting local anesthetic.

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Dynamics of paravertebral block

Paravertebral block is associated with moderate discomfort for the patient. Adequate sedation (midazolam 2-4 mg) is always necessary to facilitate the block. For analgesia of the procedure - fentanyl 50-150 mcg. Excessive sedation should be avoided, since paravertebral block becomes difficult if the patient cannot maintain balance in a sitting position. The spread of paravertebral block depends on the distribution of the anesthetic within the space and reaching the nerve roots at the level of injection. The higher the concentration and volume of local anesthetic used, the faster the expected onset of anesthesia.

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Complications and measures to prevent them

Infection. Strict adherence to aseptic rules is necessary.

Hematoma - Avoid multiple needle insertions in patients receiving anticoagulants.

General resorptive action - relatively rare in procedures such as paravertebral block. Caution should be exercised when administering large volumes of long-acting anesthetics to elderly patients; for skin infiltration, use chloroprocaine solution to reduce the total dose of long-acting anesthetic.

Nerve damage - never inject an anesthetic solution if the patient complains of severe pain or shows a defensive reaction at the time of injection.

Total spinal anesthesia - avoid medial direction of the needle to prevent epidural or intrathecal insertion through the intervertebral foramen, always aspirate for blood or cerebrospinal fluid before insertion.

Weakness of the quadriceps muscle of the thigh - may occur if the level of paravertebral block is not determined or the block was performed below L1 (femoral nerve L2-L4).

Muscle pain similar in nature to muscle spasm is sometimes observed (more often in young men with well-developed muscles) when using thick Tuohy-type needles. Preventive measures include the introduction of local anesthetic into the muscles before the procedure, and the use of smaller-diameter needles (22 gauge) or Quincke-type needles.

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