How are thoracic paravertebral somatic nerve blocks administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Thoracic paravertebral somatic nerve blocks can be performed with the patient prone using C-arm fluoroscopic guidance. This technique is also described by Waldman. [19] The spinous of process of the vertebra just above the nerve to be blocked is palpated. Bonica and Waldman advocate the insertion of a 3.5-inch or 8-cm, 22-gauge, short-beveled needle through a skin wheal located approximately 4-5 cm (or 1.5 in) lateral and perpendicular to a location that originates just below the spinous process.

A skin wheal is raised using lidocaine, and then the area is prepped with an antiseptic agent. The needle is then directed anteriorly and medially at an angle of 45° to the midsagittal plane. Waldman suggests attaching a 12-cc syringe. The needle is then carefully advanced until it strikes the appropriate transverse process.

The needle should impinge on bone after being advanced approximately 1.5 inches. After bony contact is made, the needle is withdrawn into the subcutaneous tissues, redirected inferiorly, and walked off the inferior margin of the transverse process. As soon as bony contact is lost, the needle is slowly advanced approximately three quarters of an inch deeper until a paresthesia in the distribution of the thoracic paravertebral nerve to be blocked is elicited.

Furthermore, if paresthesia cannot be elicited, then electrical nerve stimulation and lateral fluoroscopy can be used for confirmation of safe and appropriate anatomic placement. If careful aspiration reveals no blood or CSF, then 5 mL of 1%, preservative-free lidocaine can be safely injected. If an inflammatory component to the pain is noted, the local anesthetic is combined with 80 mg of methylprednisolone and is injected in incremental doses.

Subsequent daily nerve blocks can be carried out in a similar manner, substituting 40 mg of methylprednisolone for the initial 80-mg dose. Because of overlapping innervation of the posterior elements from the medial branch of the posterior division from adjacent vertebrae, the paravertebral nerves above and below the nerve suspected of subserving the painful condition must be blocked. [19, 20]


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