Figure 24-1. Anatomic considerations for cervical paravertebral block. 1 = Anterior scalene muscle; 2 = Middle scalene muscle; 3 = Brachial plexus; 4 = Phrenic nerve; 5 = Stellate ganglion; 6 = vertebral artery; 7 = Articular column of C6; 8 = Extensor muscles of the neck; 9 = Trapezius muscle; 10 = Levator scapulae muscle.

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).

Figure 24-2.Cervical paravertebral block: needle insertion technique. The needle is inserted in the V-shaped region between the anterior border of the trapezius and levator scapulae muscles. LORA = loss of resistance to air.

        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 durai sleeves, which continue along the nerve roots at this level.^1,2,5,6

Clinical Pearls

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.

Clinical Pearls

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Newer Amide Anesthetics & Sustained-Release Local Anesthetics1. Diagnosis & Management of Intraspinal, Epidural, & Peripheral Nerve Hematoma. Histology of Peripheral Nerves. Supraclavicular Brachial Plexus Block.