Paravertebral Block

Published on 06/02/2015 by admin

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Last modified 06/02/2015

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37 Paravertebral Block

André P. Boezaart, Richard W. Rosenquist

Continuous Cervical Paravertebral Block

Perspective

The cervical paravertebral brachial plexus block is a brachial root block with the same indications as continuous interscalene block; however, the classic interscalene block popularized by Winnie describes a trunk-level block. This difference has significant clinical implications. After interscalene block, patients frequently complain of an uncomfortable “dead” feeling of the arm because of dense sensory, motor, and proprioceptive block. This is generally not the case with cervical paravertebral block (PVB) because the catheter ends on the posterior root, which consists of sensory fibers. The desire to provide a pure sensory block with motor sparing, enabling patients to participate in physical therapy (especially patients with “frozen shoulder”), was the primary concern in designing the continuous cervical paravertebral block (CCPVB). In the paravertebral space, the posterior sensory and anterior motor fibers join to become the individual nerve roots. This may be the reason that more electrical current is often required to elicit a motor response when performing a cervical PVB through the posterior approach (sensory part) than with the anterior interscalene approach, and why the cervical PVB is more sensory.

The first true cervical PVB was originally described by Kappis in the 1920s. The modification later described by Pippa in 1990 was actually a posterior approach to the interscalene block because it does not “walk off the posterior tubercle of the transverse process of the vertebra” and therefore places the local anesthetic not in the paravertebral space but more laterally, in the interscalene space with the aid of nerve stimulation. Although this differentiation can become a matter of semantics, clinical experience has demonstrated the clinical relevance of this difference over the past decade.

As originally described, this block was painful because it required multiple injections and penetrated the often-tender paraspinal extensor muscles of the neck. Recently, a modification was described that avoids penetration of the extensor cervical muscles. This technique minimizes the pain associated with this approach to the brachial plexus by inserting the needle in the window between the levator scapulae and trapezius muscles at the level of the sixth cervical vertebra (Fig. 37-1).

Figure 37-1. Cervical paravertebral block: landmarks for needle puncture in right oblique view. Note needle insertion in “V” of junction of anterior border of trapezius and posterior border of levator scapulae muscles. LORA, loss of resistance to air.

Patient Selection

CCPVB is indicated for anesthesia and postoperative analgesia after upper extremity surgery or for prolonged continuous catheter analgesia in other clinical settings involving the upper limb. It has recently proved to be valuable in the management of pain due to conditions such as lung tumors infiltrating the brachial plexus (Pancoast tumors) and complex regional pain syndromes. CCPVB is especially suitable for patients scheduled for major shoulder surgery when preservation of motor function is desirable. Because ultrasonography, nerve stimulation, and loss-of-resistance techniques may be used for placement of this block, it is well suited for postoperative placement or for placement in patients with painful upper extremity conditions, in whom motor activation by nerve stimulator may be poorly tolerated.

Pharmacologic Choice

An initial bolus of 20 to 30 mL of 0.5% bupivacaine, 0.5% to 0.75% ropivacaine, or 0.5% to 0.75% levobupivacaine is usually used. When used for postoperative analgesia, this is usually followed by a continuous infusion of a lower concentration of the same drug (i.e., 0.25% bupivacaine, 0.2% ropivacaine, or 0.25% levobupivacaine) at an infusion rate of 3 to 15 mL/hr with or without the addition of patient-controlled boluses. Local anesthetic systemic toxic blood levels should be avoided when selecting an infusion rate and method.

Placement

Anatomy

The brachial plexus is situated between the anterior and middle scalene muscles (Fig. 37-2). The phrenic nerve is anterior to the anterior scalene muscle and lateral to the superior cervical plexus. The vertebral artery and vein are situated anterior to the pars intervertebralis (articular column of the vertebrae) and typically travel through the transverse foramen in the center of the transverse processes of the first to sixth cervical vertebrae. The vertebral artery lies anterior to the interarticular parts of the vertebrae, so there is minimal risk of arterial injury with a posterior needle approach.

Figure 37-2. Cervical paravertebral block: cross-sectional view.

Position

The patient is positioned in either the sitting or the lateral decubitus position (the levator scapulae muscle is usually easier to identify if the patient is sitting, but effective sedation is easier when the patient is in the lateral decubitus position). The patient’s neck is slightly flexed forward. The anesthesiologist stands behind the patient.

Needle Puncture

After preparation of the skin with an appropriate disinfectant and placement of sterile drapes, local anesthetic infiltration of the skin and subcutaneous tissue is performed to the level of the pars intervertebralis (which is easily seen with ultrasonography) and along the intended catheter tunneling site. The transverse process of C6 is distinctly different from that of other cervical vertebrae on ultrasonography because of the larger anterior tubercle of Chassaignac.

Next, an insulated 17- or 18-gauge Tuohy needle is inserted at the apex of the “V” formed by the trapezius and levator scapulae muscles at the level of the sixth cervical vertebra (see Fig. 37-1). The negative lead of the nerve stimulator, set to a current of 1.5 to 3 mA, a frequency of 2 Hz, and a pulse width of 100 to 300 µsec, is attached to the needle. If the block is intended for the management of pain associated with shoulder surgery, the needle is advanced anteromedially and is angled approximately 30 degrees caudad, aiming toward the suprasternal notch or cricoid cartilage until the transverse process of C6 or the pars intervertebralis of C6 is encountered. If the block is intended for wrist or elbow surgery, the needle is directed toward C7. This block is readily performed with ultrasonographic guidance, which avoids bony contact. However, close proximity to the bone is necessary if a true root-level block is intended. If the needle is directed too far laterally, the procedure will become no different from a traditional interscalene block except that the needle approach is posterior and not lateral.

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