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Paravertebral Nerve Block

Overview

Background

Paravertebral nerve block was a popular technique in the early 20th century. However, for some reason, paravertebral nerve block lost popularity and was almost extinct until the late 1970s, when there was a renewed interest in the technique. Recently, this technique was reviewed and found to be safe and efficacious.

A paravertebral block is essentially a unilateral block of the spinal nerve, including the dorsal and ventral rami, as well as the sympathetic chain ganglion. These blocks can be performed at any vertebral level. However, they are most commonly performed at the thoracic level because of anatomic considerations. Therefore, this topic primarily focuses on thoracic paravertebral blockade.

Indications

Paravertebral nerve blocks are indicated for surgical procedures requiring unilateral analgesia or anesthesia. Common cases benefitting from unilateral paravertebral blocks are breast surgery, thoracotomy, herniorrhaphy, open cholecystectomy, and open nephrectomy. Bilateral paravertebral blocks can be a viable option for midline abdominal surgery.

The clinician may consider thoracic paravertebral blockade over thoracic epidural analgesia in patients for whom bilateral sympathectomy and subsequent hypotension would be especially detrimental.
For example, the use of thoracic paravertebral blockade in a patient with severe aortic stenosis has been reported.
In another study, thoracic paravertebral blockade resulted in more stable hemodynamics and equivalent analgesia when compared to thoracic epidural analgesia in thorocotomy patients.
However, because bilateral spread can occur
, which may cause hemodynamic compromise similar to epidural blockade.

Another unique feature of thoracic paravertebral blockade compared with thoracic epidural analgesia is the relative safety when performing these blocks on patients with a marginal coagulation cascade. This does not mean, however, that thoracic paravertebral blockade can be performed on patients with coagulopathy without caution. According to the American Society of Regional Anesthesia and Pain Medicine’s evidence-based guidelines, in the patient receiving antithrombotic or thrombolytic therapy, the exact same precautions should be taken when placing thoracic paravertebral blockade as when placing an epidural. However, if bleeding occurs in the thoracic paravertebral space, significant blood loss will be the likely complication rather than epidural hematoma and neurologic deficit.

Contraindications

Contraindications to paravertebral nerve blocks include the following:

Patient refusal

Severe coagulopathy

Local infection

Allergy to local anesthetics (rare, usually the allergy is to the preservative)

Severe hypovolemia (especially for bilateral blocks)

Untreated sepsis

Anatomy

The thoracic paravertebral space is a triangular- or wedge-shaped space running the length of the thoracic vertebral column bilaterally (see the image below).

Anatomy of the thoracic paravertebral space (outli

Anatomy of the thoracic paravertebral space (outlined in dashed red line).

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It is bounded posteriorly by the superior costotransverse ligament (a continuation of the internal intercostal muscle); anteriolaterally by the parietal pleura; and medially by the vertebral bodies, intervertebral foramina, and the intervertebral discs.

In contrast to cervical and lumbar regions, the thoracic paravertebral space is in continuity with adjacent vertebral levels, allowing for spread of local anesthetic. This anatomic property explains why the thoracic paravertebral space may have more utility than cervical or lumbar paravertebral blocks.

Complications

Complications of paravertebral nerve blocks may include the following:

Failed block

Hypotension

Vascular puncture

Pleural puncture

Pneumothorax

Failure rate may be lower with ultrasound, but this has not been studied.

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