Chapter 24. Cervical Paravertebral Block

The cervical paravertebral approach to the brachial plexus results in a volume-dependent blockade of the roots of the brachial plexus. Cervical paravertebral block is indicated for anesthesia and postoperative analgesia in all major surgery on the upper extremity, including surgery on the shoulder, elbow, and wrist.1 It is also suitable for patients in whom it is difficult to reach the brachial plexus trunks via the interscalene approach.2 Because both the loss-of-resistance technique and nerve stimulation can be used for placement of this block, it is well suited to postoperative placement or for other patients (eg, patients with fractures of the arm) in whom motor activity due to nerve stimulation may be poorly tolerated.1

The technique described in this chapter is a modification of the single-injection block, originally described by Kappis in the 1920s3 and modified by Pippa in 1990.4 The original technique never gained popularity, probably because it was uncomfortable to patients due to penetration of the paraspinal extensor muscles of the neck. A modified technique, which does not penetrate these muscles, was described recently.5,6 The modification is insertion of the needle in the V-shaped space between the levator scapulae and trapezius muscles at the level of the sixth cervical vertebra. By this method, penetration of the posterior paraspinal muscles is avoided, which minimizes the associated pain of this approach. Because all of the structures (eg, vertebral artery and vein, phrenic nerve, carotid and other major arteries, internal jugular vein, etc.) associated with complications from brachial plexus blockade are anterior to the nerve roots in the neck, where they exit the neuroforamina, Kappis' original argument that it is best to approach the roots from the posterior, where there are only muscles, remains valid. Furthermore, at the root level of the brachial plexus, which is the level at which this block is done,5,6 the nerve fibers are arranged with sensory fibers posterior and motor fibers anterior. This probably explains the predominantly sensory block when approached from the posterior aspect of the neck.

Anatomy

The brachial plexus is situated between the anterior and middle scalene muscles (Figure 24–1). The phrenic nerve lies in front of the anterior scalene muscle. The vertebral artery and vein are situated anterior to the pars intervertebralis, or articular column of the vertebrae. The approach described in this section1,2,5,6 avoids penetrating the extensor muscles of the neck by entering the neck through the “window” at the level of apex of the V formed by the trapezius and levator scapulae muscles (Figure 24–2).

Patient Positioning

Proper patient positioning is critical to the successful performance of this block. The patient is placed in the sitting or the lateral decubitus position (the levator scapulae muscle is usually easier to identify if the patient is in the sitting position). Elevating the head of the bed during the procedure facilitates venous drainage, and reduces venous oozing during the procedure. The patient's neck is flexed slightly forward and to the opposite side, and the anesthesiologist stands behind the patient.

Needle Insertion

After preparing the skin with a disinfectant and placement of sterile drapes, local anesthetic is infiltrated into the skin and subcutaneous tissue to the level of the pars intervertebralis (articular column) and tunneling site for the catheter. 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 vertebrae (see Figure 24–2).

The nerve stimulator is set to deliver a current of 1 to 2 mA (frequency of 2 Hz and a pulse width of 100–300 μs) and its negative lead is attached to the needle. The needle is advanced anteromedially and approximately 30-degrees caudad, aiming toward the suprasternal notch or cricoid cartilage until the transverse process of C6 or the pars intervertebralis (articular column) of C6 is encountered. At this point, the stylet of the needle is removed, and a loss-of-resistance syringe is attached to the needle. While continuously testing for loss of resistance, the needle is walked off the bony structure (vertebra) by redirecting the needle laterally and then advancing it anteriorly. A distinct loss of resistance to air usually occurs simultaneously with contraction of the shoulder muscles when the cervical paravertebral space is entered (approximately 0.5–1 cm beyond the transverse process of the vertebra). At this level, the motor (anterior) and sensory (posterior) fibers have joined to form the roots of the brachial plexus, and typically, more current is required to elicit a motor response than with an anterior interscalene technique. If a single-injection technique is used, 20–40 mL of the local anesthetic is incrementally and slowly injected while monitoring the patient for the signs and symptoms of local anesthetic toxicity. The choice of type and concentration of local anesthetic depends on the desired degree of motor blockade and the desired duration of action. A catheter can also be inserted to allow prolongation of analgesia into the postoperative period. The onset of full surgical anesthesia with this technique typically requires 20 to 45 min. This somewhat slower block onset (compared to the interscalene block) is likely caused by thick dural sleeves, which continue along the nerve roots at this level.1,2,5,6

Continuous Cervical Paravertebral Block

With continuous technique, when the tip of the needle approaches the roots of the brachial plexus, as indicated by a motor response, or the patient reporting sensory pulsation at a nerve stimulation output of approximately 0.5 mA, or loss of resistance to air is detected, the needle is held steady while the loss-of-resistance syringe is removed. If a nonstimulating technique is used for catheter placement, a bolus injection is given through the needle, and a standard epidural catheter is inserted. If a stimulating catheter technique is used, the nerve stimulator lead is attached to the proximal end of the 19- or 20-gauge stimulating catheter, and its distal end is inserted into the needle shaft. The nerve stimulator output is kept constant at a current that provides brisk muscle twitches of the shoulder or upper extremity muscles, and the catheter tip is advanced 5 cm beyond the tip of the needle. When the catheter is correctly placed, it is secured at a convenient position and covered with transparent dressing.

An initial bolus of 20 to 40 mL of 0.5% bupivacaine, 0.5 to 0.75% ropivacaine, or 0.5% levobupivacaine may be used.1,2,5,6 When used for postoperative analgesia, the bolus is followed by a continuous infusion of a lower concentration of the same drug; that is, 0.25% bupivacaine, 0.2% ropivacaine, or 0.2% levobupivacaine, at an infusion rate of 3 to 10 mL/h and patient-controlled boluses of 5 to 10 mL every 30 to 240 min.

Horner syndrome can be expected in approximately 40% of patients.1 However, this does not cause problems when patients are warned beforehand of this side effect. Due to phrenic nerve blockade, up to 8% of patients may complain of dyspnea in the recovery room. Dyspnea is usually experienced when both the phrenic and recurrent laryngeal nerves are blocked with oxygen supplementation, placing the patient in the Fowler's position and providing reassurance, this should not pose significant problems. Only 2% of patients continue to experience dyspnea after 6 h; no patients complained of dyspnea after 12 h.1

Infection at the catheter site is a potentially serious complication, especially after a major joint replacement (eg, shoulder, elbow, or wrist arthroplasty). In our study,5 5% (13 of 256 cases) of the catheter entry sites showed signs of localized infection. This was limited to redness of the skin at the catheter entry site (n = 10 of 13) and purulent discharge (n = 3 of 13). Staphylococcus aureus and S. epidermidis were cultured in 7 of the 13 cases. If infection is suspected, the catheter should be removed and antibiotic therapy considered.

Posterior neck pain is a common complication seen with this block. In one report, 22% of the patients had some pain at the catheter insertion site.1 Most of these patients were successfully treated with nonsteroidal antiinflammatory drugs, and it was not necessary to remove the catheters in the majority. This complication can largely be prevented by making sure that the catheter is inserted between the extensor muscles of the neck and not through them.

The subclavian artery, situated anterior to the brachial plexus, can be punctured by a posterior approach only if the plexus is penetrated. Puncture should not occur when the nerve stimulator is functioning properly.

Eleven of the 256 patients in this series (4%) experienced numbness in the fingers of the contralateral hand due to MRI-confirmed epidural spread of the local anesthetic agent. The numbness resolved in all the patients within 6 h without any respiratory or other sequelae.

The choice of local anesthetic agent is not critical, except in situations when motor block is not desirable, such as “frozen shoulder.” This author uses 0.5% ropivacaine as default agent; using bupivacaine or levobupivacaine in equipotent concentrations is equally suitable. Similar to other block procedure, a shorter acting local anesthetics can be used when desired.

Arthroscopic Subacromial Decompression

Arthroscopic subacromial decompression (ASAD) surgery typically does not result in significant postoperative pain, and a continuous block is usually not indicated. A single-injection block provides analgesia for a few hours postoperatively. Brachial plexitis may well be the underlying cause of the shoulder pain in more patients than is commonly realized; therefore, blocks for this indication should be used with caution and carefully documented. If, however, a rotator cuff tear was found and repaired, a continuous cervical paravertebral block can be placed. Placement can be done in the operating room using resistance to air and before waking the patient or in the recovery room after the patient emerges from general anesthesia. The choice depends on the institutional protocol and the anesthesiologist's preference.

Shoulder, Elbow, & Wrist Arthroplasty; Shoulder Stabilization; & Rotator Cuff Repair

The continuous cervical paravertebral block is well suited for total or hemi- shoulder, elbow, and wrist arthroplasty. A relatively large volume of local anesthetic (20–40 mL) is injected as a bolus. These volumes usually block all the brachial plexus roots, which is ideal for the surgery since the innervation of the major joints of the upper limb is from the complete brachial plexus. Keep in mind that the onset of action is slower than in interscalene block, probably because of the dural sheath surrounding the roots. In placing the block, the needle tip is aimed more toward the lower roots (C7 through T1) for wrist arthroplasty and more toward the upper trunks (C5 and C6) for shoulder arthroplasty.

A continuous infusion of 5 mL/h of a lower concentration of the drug (eg, ropivacaine 0.2%) with patient-controlled regional analgesia (PCRA) boluses of 10 mL of the same drug at a lockout time of 1 h is used. Some investigators suggest that PCRA without continuous infusion is satisfactory.7

The motor block is denser in the proximal parts of the upper limb than in the distal parts, with a bolus injection of 30 mL of 0.5% ropivacaine and a continuous infusion of 0.2% ropivacaine at 0.1 mL/kg/h.5 The distal motor block can also be expected to subside earlier than the proximal, and the sensory block outlasts the motor block. This feature makes the block suitable for shoulder surgery because it provides a dense sensory–motor block in the early postoperative period, while the motor function returns to the hand after approximately 36 h, and after 60 h in the shoulder area. The sensory block and analgesia are present for the duration of the surgery. The block virtually “tapers” itself as the need for motor block subsides over time.

Frozen Shoulder

Patients with primary adhesive capsulitis, or primary “frozen shoulder,” require special considerations with regard to the use of the brachial plexus block. Frozen shoulder is a chronic fibrosing condition of the shoulder joint capsule.8,9 Its histologic pathology is similar to Dupuytren's disease, and it shares a common biochemical pathway that leads to the contracture seen in Dupuytren's disease. The latter is, however, a progressive condition, whereas primary frozen shoulder is a self-limiting disorder that resolves with time. Primary frozen shoulder can have components of sympathetic dystrophy, having the characteristics of an algoneurodystrophic process similar to complex regional pain syndrome.10 To rehabilitate primary frozen shoulder, it is essential that the patient be free from pain in the postoperative period. Motor blockade should be avoided so that the patient can participate in physical therapy. For these reasons, low concentrations (0.1%) of ropivacaine should be used. This author uses low infusion rates varying from 0 to 3 mL/h of 0.1% ropivacaine, and allows 5- to 10-mL PCRA boluses at a 60-min lockout time.

The block is probably not indicated for surgery of the clavicle because the clavicle receives its nerve supply from the entire brachial and cervical plexi. Similarly, this technique is not ideal for surgery on the acromioclavicular joint.

The cervical paravertebral block is a newer technique for brachial plexus blockade. It presents an excellent alternative to continuous interscalene block for shoulder surgery and the continuous supra- and infraclavicular blocks for major elbow and wrist surgery. Experience with other approaches to brachial plexus block and strict adherence to the outlined precautions are necessary to ensure success and avoid complications.