Paravertebral Block

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Chapter 12 Paravertebral Block

Sang-Sik Choi, MD, Mi-Guem Lee, MD, Mi-Kyung Lee, MD, PhD

The paravertebral space does not naturally exist. It is a potential space that can be created by fluid distention. If fluid (e.g., local anesthetics) is injected, it will distend and open a wedge-shaped space [1]. The boundaries of the paravertebral space are described in Table 12.1. Lumbar paravertebral block (PVB) is also known as lumbar plexus block and psoas compartment block.

Table 12.1 Boundaries of the Paravertebral Space

Posterior	Superior costotransverse ligament Laterally to the posterior intercostal membrane
Anterior	Parietal pleura
Medial	Posterolateral aspect of the vertebra, intervertebral disc, intervertebral foramen
Superior	Occiput
Inferior	Alar of the sacrum
Lateral	No limit; contiguous with the intercostal space

From Richardson J. Paravertebral anesthesia and analgesia. Can J Anaesth 2004;51:R1-R6.

Local anesthetics injected in this area will bathe the following neurologic structures: the anterior and posterior rami of the spinal nerve, and the white and gray rami communicantes. In the thoracic region, the sympathetic chain is exposed to injectate because it is located laterally to the vertebral body, not anterolaterally as in the lumbar region. In the lumbar region, the sympathetic chain may not be involved because it is separated from more posterior structures arising from the intervertebral foramen by the iliopsoas muscle, which originates from the lateral vertebral bodies (Table 12.2; Figs. 10-10 and 10-11)[1–4]. The sacral spine cannot be subjected to PVB owing to the fusion of the transverse processes to form the lateral mass.

Table 12.2 Potential Tracking of Injectate from Deposition within the Paravertebral Space

Superior and inferior	Within the paravertebral gutter In the thorax across the heads and necks of the ribs
Medial	Through the intervertebral foramen (epidural anesthesia)
Lateral	Contribution to cervical, stellate ganglion, brachial plexus, intercostal and lumbar plexus blockade
Anterior	Not possible unless pleura is breached

From Richardson J. Paravertebral anesthesia and analgesia. Can J Anaesth 2004;51:R1-R6.

In a study of patients with chronic pain undergoing PVB with 15 mL of 0.5% bupivacaine, a mean somatic block of five dermatomes was accompanied by a mean sympathetic block of eight dermatomes, as evidenced by thermographic detection of ipsilateral skin warming [5]. Combinations of local anesthetics with adjuncts such as opiates and clonidine may also be very helpful in improving the quality and duration of the nerve block.

The dose of local anesthetics required involves a consideration of the number of dermatomes to block. Continuous infusion provides better analgesia than intermittent bolus doses [1,6].

Lumbar paravertebral block

Lumbar PVB is a favorable choice for selective anesthesia or analgesia of one leg. Lumbar PVB anesthetizes the plexus at its origin, achieving blockade of all branches of the lumbar plexus (femoral, lateral femoral cutaneous, obturator, and genitofemoral). Lumbar PVB allows early ambulation, enabling effective physiotherapy and early discharge. In addition, lumbar PVB is not associated with hemodynamic changes or urinary retention, which would require labor-intensive postoperative care.

Many different methods have been developed for performing posterior lumbar PVB. A loss-of-resistance (LOR) technique using air or saline or an approach using a peripheral nerve stimulator is usually employed to confirm correct placement of the needle within the paravertebral space or psoas compartment. However, these blind blocks are time-consuming and inconvenient to both the patient and the physician. In addition, lumbar PVB cannot be reliably confirmed through the use of only the LOR technique with air or saline; this deficiency can be overcome, however, with the use of C-arm (fluoroscopy) guidance during lumbar PVB in addition to LOR with air or saline.

Thoracic paravertebral block

Thoracic PVB is the technique of injecting local anesthetic adjacent to the thoracic vertebra close to where the spinal nerves emerge from the intervertebral foramina. This maneuver results in ipsilateral somatic and sympathetic nerve blockade in multiple contiguous thoracic dermatomes above and below the site of injection. It is effective in treating acute and chronic pain of unilateral origin from the chest and abdomen. Bilateral use of thoracic PVB has also been described.

Treatment objectives

The treatment objectives of paravertebral blocks are to relieve pain and to improve quality of life. The goals are to provide an early return to physical functioning and work, to restore the ability to perform daily activities, and to allow for recreation.

Indications

The indications for paravertebral block vary with the location of the block [1–3,6–16].

Lumbar Paravertebral Block

Indications for lumbar PVB are as follows:

Anesthesia and the management of pain associated with unilateral lower limb surgery

Peripheral vascular disease, such as atherosclerosis obliterans or thromboangiitis obliterans

Postherpetic neuralgia

It may also be used in patients undergoing anticoagulation therapy in whom neuraxial block is contraindicated.

Thoracic Paravertebral Block

Thoracic PVB is performed for the following indications (Box 12.1):

Unilateral surgical procedures, such as thoracotomy, breast surgery, cholecystectomy, cardiac surgery, and renal or ureteric surgery

Analgesia for rib trauma and herniorrhaphy

Bilaterally in thoracic surgery and major abdominal vascular surgery

For management of herpes zoster pain, post-mastectomy pain, post-thoracotomy pain, chronic abdominal pain, chronic inguinal pain, benign or malignant neuralgia, complex regional pain syndromes with a sympathetic component, vascular insufficiency, and differential nerve blockade

Hyperhidrosis

As an adjunct to interscalene block for major shoulder procedures

For bone harvesting from the iliac crest

Obstetric analgesia

Complications

The overall incidence of side effects or complications of thoracic or lumbar PVB is less than 5%; complications are as follows [1–3,17]:

Hypotension, which is unusual and has multifactorial causes; it usually involves the unmasking of relative hypovolemia by unilateral vasodilatation

Acute cardiac or neurologic toxicity caused by accidental intravascular injection

Pleural puncture

Pneumothorax

Neurologic or hemodynamic events due to accidental epidural or intrathecal injection (Figs. 12-1 and 12-2)

Infection (epidural abscess, meningitis, etc.)

Renal subcapsular hematoma

Vasovagal response

Horner’s syndrome

Dyspnea

Superficial skin infection

Posterior neck pain

Subclavian artery puncture

Epidural spread of anesthetic

Figure 12–1 An anteroposterior image of lumbar paravertebral block. Note that contrast agent spreads into the epidural space (1) as well as to the psoas compartment (2).

(From De Biasi P, Lupescu R, Burgun G, et al. Continuous lumbar plexus block: Use of radiography to determine catheter tip location. Reg Anesth Pain Med 2003;28:135-139.)

Figure 12–2 A computed tomography scan of the epidural spread of contrast agent. Note the spread of the contrast in the epidural space (1) and through the intervertebral foramen of L4 (2) as well as the opacification of the psoas compartment (3) and catheter (4).

(From De Biasi P, Lupescu R, Burgun G, et al. Continuous lumbar plexus block: Use of radiography to determine catheter tip location. Reg Anesth Pain Med 2003;28:135-139.)

Anesthesia

Very little or no sedation is typically required for this block. Local skin infiltration with 1% to 2% lidocaine at the insertion site is enough for blocks as well as for the intended tunneling path of the catheter. For very anxious patients, conscious sedation can be achieved with a combination of fentanyl, ketorolac, and midazolam.

PVB may be performed with anesthesia in some patients, such as a child or a patient suffering from a very painful condition.

Instruments

The following equipment and supplies are required for thoracic or lumbar PVB:

An 18- or 20-gauge Tuohy needle and a catheter

Appropriate injection syringes and needles

Water-soluble contrast agent

1% lidocaine without epinephrine for infiltration

0.2% to 0.375% ropivacaine or 0.25% bupivacaine

Procedures

Lumbar Paravertebral Block

Anatomy [16–25]

The lumbar plexus emanates from lumbar roots of L1 through L4 with a variable contribution from T12. It lies between the quadratus lumborum and psoas major muscles and descends vertically in the mass of the psoas muscle. At the level of L5 and S1, the nerve roots of L3 through L5 and even L2 run downward in a compact bundle before branching into the femoral and obturator nerves (Fig. 12-3).

Figure 12–3 Anatomy of the lumbar plexus. The pink branches are derived from the anterior divisions and the green branches from the posterior divisions of the anterior primary rami of the lumbar nerves. T12, 12th thoracic vertebra; L1 through L5, first through fifth lumbar vertebrae.

(Modified from Craven J. Lumbar and sacral plexuses. Anaesth Intensive Care 2004;5:108.)

The important nerves emanating from the lumbar plexus are the femoral nerve (posterior divisions of anterior primary rami of L2-L4), the obturator nerve (anterior divisions of the anterior primary rami of L2-L4), and the lateral femoral cutaneous nerve (posterior divisions of the anterior rami of L2-L3). Other important nerves emanating from the lumbar plexus are the iliohypogastric, ilioinguinal, and genitofemoral nerves, which emanate primarily from L1 (Fig. 12-3).

The femoral nerve is the largest terminal branch of the lumbar plexus. It provides the sensory innervation of the anterior aspect of the thigh and medial lower leg and the motor innervation of the quadriceps muscle (Figs. 12-4 and 12-5).

Figure 12–4 Somatic neurotomal distribution of the lower extremity. br., branch; n., nerve.

(Modified from Brown DL: Psoas compartment block. In: Atlas of Regional Anesthesia, 3rd ed. Philadelphia, Elsevier/Saunders, 2006, pp 95-96.)

Figure 12–5 Somatic neurotomal distribution of the lower extremity. br., branch; n., nerve.

(Modified from Brown DL: Psoas compartment block. In: Atlas of Regional Anesthesia, 3rd ed. Philadelphia, Elsevier/Saunders, 2006, pp 95-96.)

The obturator nerve supplies the obturator externus and the adductor muscles of the thigh and sends sensory fibers to the hip and knee joints. Sensory innervation of the obturator nerve to the skin is quite variable. Isolated block of the obturator nerve results in no cutaneous distribution in 57% of patients, an area of hypoesthesia in the superior part of popliteal fossa in 23%, and sensory deficit in the inferomedial aspect of the thigh in 20% [22]. However, adductor muscle weakness is a more reliable sign to evaluate obturator nerve block because all patients experience it (Figs. 12-4 and 12-5).

The lateral femoral cutaneous nerve provides sensory innervation of the lateral aspect of the thigh. The nerve divides into anterior and posterior branches. The anterior branch supplies cutaneous sensation to the lateral thigh, including just proximal to the patella. The posterior branch supplies the skin from the greater trochanter to the mid-thigh (Figs. 12-4 and 12-5).

Procedure

Single-injection technique

The procedure for the single-injection technique of lumbar PVB is as follows:

1. The patient’s written informed consent is obtained.

2. The patient is placed in the prone position.

3. The overlying skin is sterilized, and the site is draped with sterile dressing.

4. The C-arm is aligned with the vertebral end plates parallel in an anteroposterior (AP) projection and the spinous process in the midline.

5. The skin entry point is about 1 cm caudal to the mid-third of the L3, L4, or L5 transverse process.

6. A 22-gauge spinal needle is advanced perpendicular to the skin and directed to the lower border of the transverse process of the target level until the target transverse process is encountered (Fig. 12-6).

7. The needle is then redirected slightly caudad, sliding past the inferior border of the transverse process and advancing until the loss of resistance is noted. 1-4 mL of contrast agent is then injected via the needle (Fig. 12-7A to C).

8. A total of 20 mL of the local anesthetic is injected in divided doses (Fig. 12-7D).

Figure 12–6 Anatomy for and technique of lumbar paravertebral block. The injected local anesthetics (sky-blue area around the needle tip) will distend and open a wedge-shaped potential space.

Figure 12–7 C-arm (fluoroscopy)–guided paravertebral block at L5. A and B, Lateral radiographs show the final position of the tip of the needle and spread of contrast agent in the paravertebral space. C, An anteroposterior radiograph shows needle placement below the border of the L5 transverse process. D, Extension of the spread of contrast agent during the drug injection via indwelling catheter is shown.

It should be noted that the area surrounding the lumbar plexus is richly vascularized. Thus, the syringe should be frequently aspirated during injection to avoid accidental intravascular spread of local anesthetics.

Continuous technique

The continuous technique of lumbar PBV is the same as the single-injection technique from step 1 to step 7. It then proceeds as follows:

8. A catheter is advanced through the needle, 3 to 5 cm past the needle tip, into the paravertebral compartment.

9. The catheter is then subcutaneously tunneled in a lateral direction to exit the skin 5 to 10 cm laterally after subcutaneous infiltration of local anesthetics (Fig. 12-8A); the inner stylet of the needle is placed next to the catheter and advanced subcutaneously through the catheter entry wound to exit the skin approximately 5 to 10 cm away (Fig. 12-8B).

10. The needle is passed retrogradely over the stylet (Fig. 12-8C). The stylet is removed and the proximal end of the catheter is inserted into the needle.

11. The catheter is pulled through the needle, and the needle is removed (Fig. 12-8D). The loop of the catheter should disappear under the skin. The catheter is fixed firmly by suture.

Figure 12–8 An example of the subcutaneous tunneling technique performed at the caudal area for continuous caudal infusion. A, Subcutaneous infiltration of local anesthetics. B, The inner stylet of the needle is placed next to the catheter and advanced subcutaneously to the skin approximately 5 to 10 cm away from the skin entry site. C, The needle is passed retrogradely over the stylet. D, The stylet is removed, and the proximal end of the catheter is inserted into the needle. The needle is then removed.

Lumbar PVB can be performed through the upper border of the transverse process of the target level with the same technique.

Continuous Infusion

Continuous infusion is performed with disposable elastometric infusion pumps, delivering 0.2% to 0.375% ropivacaine or 0.25% bupivacaine at a rate of 0.1 mL/kg/hr in children and 4 to 8 mL/hr in adults. Patient-controlled analgesia may be used with satisfactory results. The infusion rates are adjusted over the first 24 hours to obtain optimal analgesia and minimal motor block.

If pain relief is not satisfactory and “breakthrough” pain occurs, an additional bolus of 0.2% to 0.375% ropivacaine 10 mL can be injected through the catheter; this may be repeated every 30 minutes up to a maximum of 3 bolus injections per 6-hour period.

Thoracic Paravertebral Block

Anatomy

The paravertebral space is a wedge-shaped anatomical compartment adjacent to the vertebral bodies [1,2,4,12,14]. The space is defined anterolaterally by the parietal pleura, posteriorly by the costotransverse ligament, medially by the vertebra, vertebral disc, and intervertebral foramina, and superiorly and inferiorly by the head of the ribs (Fig. 12-9; Tables 12.1 and 12.2).

Figure 12–9 Thoracic paravertebral space (yellow area) in a transverse section diagram (A) and a sagittal section diagram (B).

Within the space, the spinal root emerges from the intervertebral foramen and divides into dorsal and ventral rami. In addition, sympathetic fibers of the ventral rami enter the sympathetic trunk via the preganglionic white rami communicantes and the postganglionic gray rami communicantes in the space (Fig. 12-9).

Because of the multiple neurologic structures confined within this compact space, the injection of local anesthetic can produce unilateral motor, sensory and sympathetic blockades.

Procedures

Single-injection technique

The procedure for the single-injection technique of thoracic PVB is as follows:

1. The patient’s written informed consent is obtained.

2. The patient is placed in the prone position with neck flexion. The back is arched posteriorly, and the shoulders relaxed forward.

3. The overlying skin is sterilized and the site is draped with sterile dressing.

4. The C-arm (fluoroscope) is adjusted to obtain an adequate anteroposterior view: The transverse process of the target vertebra should be viewed clearly, and the spinous process of the target vertebra should be positioned in the midline.

5. The needle entry point is 1 cm cephalad to the mid-third of the upper margin of the transverse process.

6. After subcutaneous infiltration of local anesthetics at the skin entry point, a 22-gauge spinal needle is advanced perpendicular to the skin and directed slightly toward the upper border of the transverse process of the target level until the target transverse process is encountered.

7. The needle is then redirected to slide past the transverse process and advanced either until loss of resistance to air or saline is noted or until the needle is 1 to 1.5 cm from the superior margin of the transverse process (Fig. 12-10). We prefer the latter technique because the loss-of- resistance technique is often unreliable.

8. 2 to 5 mL of contrast agent is injected via the spinal needle.

9. After the paravertebral compartment has been identified (Figs. 12-11 and 12-12), a total of 10 to 15 mL of the local anesthetic solution is injected in divided doses. For unilateral block, 5 mL per level is injected.

Figure 12–10 Anatomy for and technique of thoracic paravertebral block. Diagrams show the path of the needle in transverse section (A) and in sagittal section (B). An 18- or 20-gauge Tuohy needle is advanced perpendicular to the skin and directed slightly toward the upper or lower border of the transverse process of the target level until the target transverse process is encountered. The needle is then redirected slightly to slide past the transverse process and advanced until the loss of resistance is elicited. Needle position shown is the final needle position for thoracic PVB. The injectate may spread in the yellow area.

Figure 12–11 A computed tomography scan shows ipsilateral paravertebral and prevertebral spread of contrast agent with no epidural spread.

(Adapted from Karmakar MK, Chui PT, Joynt GM, et al. Thoracic paravertebral block for management of pain associated with multiple fractured ribs in patients with concomitant lumbar spinal trauma. Reg Anesth Pain Med 2001;26:169-173.)