Chapter 43. Thoracic & Lumbar Paravertebral Block

Thoracic paravertebral block (TPVB) is the technique of injecting local anesthetic alongside the thoracic vertebra close to where the spinal nerves emerge from the intervertebral foramen.1,2 This produces unilateral, segmental, somatic, and sympathetic nerve blockade,3 which is effective for anesthesia and in treating acute and chronic pain of unilateral origin from the chest and abdomen.1 Hugo Sellheim of Leipzig (1871–1936) is believed to have pioneered TPVB in 1905.1,2 Kappis, in 1919, developed the technique of paravertebral injection, which is comparable to the one in present-day use. Although paravertebral block was fairly popular in the early 1900s, it seemed to have fallen into disfavor during the mid and later part of the century, the reason for which is not known. In 1979 Eason and Wyatt rekindled interest by describing a technique of paravertebral catheter placement.4 Our understanding of the safety and efficacy of TPVB has improved significantly in the last 25 years, and there has been a gradual renewal of interest in this technique. Currently it is used not only for analgesia but also for surgical anesthesia,5–7 and its application has been extended to children.8–10

Anatomy

The thoracic paravertebral space (TPVS) is a wedge-shaped space located on either side of the vertebral column (Figure 43–1). The parietal pleura forms the anterolateral boundary. The base is formed by the vertebral body, intervertebral disc, and the intervertebral foramen with its contents. The transverse process and the superior costotransverse ligament form the posterior boundary. Lying in between the parietal pleura anteriorly and the superior costotransverse ligament posteriorly is a fibroelastic structure, the endothoracic fascia, which is the deep fascia of the thorax (Figure 43–1, 43–2, and 43–3).1,11–15 Medially the endothoracic fascia is attached to the periosteum of the vertebral body. A layer of loose areolar connective tissue, the subserous fascia, lies between the parietal pleura and the endothoracic fascia. Therefore there are two potential fascial compartments in the TPVS: the anterior extrapleural paravertebral compartment and the posterior subendothoracic paravertebral compartment (see Figures 43–1 and 43–2). The TPVS contains adipose tissue within which lie the intercostal (spinal) nerve, the dorsal ramus, intercostal vessels, rami communicantes, and anteriorly the sympathetic chain. The spinal nerves are segmented into small bundles and lie freely in the adipose tissue of the TPVS, which make them accessible to local anesthetic solutions injected into the TPVS.16

The TPVS communicates with the epidural space medially17,18 and with the intercostal space laterally. The TPVS on either side of the thoracic vertebra also communicate with each other through the epidural and prevertebral space.1,12,15 The cranial extension of the TPVS is challenging to define and may significantly vary; however, we have observed direct paravertebral spread of radiopaque contrast medium from the thoracic to the cervical paravertebral space, indicating a direct anatomic continuity. The TPVS also communicates caudally through the medial and lateral arcuate ligaments with the retroperitoneal space behind the fascia transversalis, where the lumbar spinal nerves are located.13,19–21

Mechanism of Block & Distribution of Anesthesia

TPVB produces ipsilateral somatic and sympathetic nerve blockade (Figure 43–4) due to a direct effect of the local anesthetic on the somatic and sympathetic nerves in the TPVS, extension into the intercostal space laterally, and the epidural space medially. The overall contribution of epidural spread to the dermatomal distribution of anesthesia following a TPVB is not well defined. However, some degree of ipsilateral spread of local anesthetic toward the epidural space probably occurs in the majority of patients, resulting in a greater distribution of anesthesia than occurs with paravertebral spread alone.18 The dermatomal distribution of anesthesia following a single injection of a large volume (eg, injection of 15–25 mL of local anesthetic at one level) varies and is often unpredictable.1,3,22 However, the injected solutions routinely spread both cephalad and caudad to the site of injection to some extent (Figure 43–5). Nevertheless, the multiple-injection technique, where small volumes (3–4 mL) of local anesthetic are injected at several contiguous thoracic levels, is preferable over single, large-volume injection. This is particularly important when reliable anesthesia over several ipsilateral thoracic dermatomes is desired, such as when TPVB is used for anesthesia during breast surgery.

Segmental contralateral anesthesia, adjacent to the site of injection, occurs in approximately 10% of patients after single-injection TPVB and may be due to epidural or prevertebral spread. Bilateral symmetrical anesthesia due to extensive epidural spread or unintentional intrathecal injection into a dural sleeve may occur, particularly when the needle is directed medially or when a larger volume of local anesthetic (>25 mL) is used. For this reason, during placement of TPVB, patients should be monitored using the same vigilance and methods as those employed for injection using the large-volume, single-injection epidural technique. The ipsilateral ilioinguinal and iliohypogastric nerves may also occasionally be involved after lower thoracic paravertebral injections. This is either due to epidural spread or extended subendothoracic fascial spread to the retroperitoneal space where the lumbar spinal nerves are located. The effect of gravity on the dermatomal spread of anesthesia after TPVB is unknown, but there may be a tendency for preferential pooling of injected solution toward the dependent levels.3,23,24

Technique

It is preferable to perform TPVB with the patient in the sitting position because the surface anatomy is better visualized and patients are often more comfortable. However, when this is not possible or practical, TPVB can also be performed with the patient in the sitting, lateral, or prone position. The number and level of injections are selected according to the desired spread of local anesthesia. In this example, description of the TPVB for breast surgery is described. Surface landmarks are identified and marked with a skin marker before block placement (Figure 43–6). Skin markings are also made 2.5 cm lateral to the midline at the thoracic levels that are to be blocked. These markings indicate the needle insertion sites and should lie over the transverse process of the vertebra (Figure 43–7).

A standard regional anesthesia tray is prepared, and strict asepsis should be maintained during block placement. A 22-gauge Tuohy- or Quincke-tip spinal needle is used for a single- or multiple-injection TPVB (Figure 43–8). If the needle does not have depth markings on its shaft, a depth guard (see Figure 43–8) is recommended. An epidural set is used if insertion of a catheter into the TPVS is planned. Multiple injections during TPVB are uncomfortable and require a proper premedication (eg, midazolam 2–3 mg plus fentanyl 50–100 mcg) to ensure patient acceptance and comfort during the block placement.

Loss‐of-Resistance Technique

There are several different techniques of TPVB. The classical technique involves eliciting loss of resistance. The skin and underlying tissue is infiltrated with lidocaine 1%, and the block needle is inserted perpendicular to the skin in all planes to contact the transverse process of the vertebra. Note that due to the acute angulation of the thoracic spines in the midthoracic region, the transverse process that is contacted is the one from the lower vertebra (Figures 43–9 and 43–10). The depth at which the transverse process is contacted varies (3–4 cm) and depends on the build of the individual and the level at which the needle is inserted. The depth is deeper at the cervical and lumbar spine level and shallower at the thoracic levels. During needle insertion it is possible to miss the transverse process and inadvertently puncture the pleura. Therefore it is imperative to search and make contact with the transverse process before advancing the needle too deep and risking pleural puncture. To minimize this complication, the block needle should initially be inserted only to a maximum depth of 4 cm at the thoracic and 5 cm at the cervical and lumbar levels. If bone is not contacted it should be assumed that the needle is in between two adjacent transverse processes. The needle should be withdrawn to the subcutaneous tissue and reinserted with a cephalad or caudad direction to the same depth (4 cm) until bone is contacted. If bone is still not encountered, the needle is advanced a further centimeter and the above procedure repeated until the transverse process is identified. The needle is then walked above (these authors' preference) or below the transverse process and gradually advanced until a loss of resistance is elicited as the needle traverses the superior costotransverse ligament into the TPVS (Figures 43–3 and 43–11). This usually occurs within 1 to 1.5 cm from the superior edge of the transverse process (see Figure 43–3). Although a subtle “pop” or “give” may be appreciated as the needle traverses the superior costotransverse ligament, this should not be entirely relied on. Instead, the depth of the needle placement should be guided by the initial bone contact (skin-transverse process plus 1 to 1.5 cm). Unlike localization of the epidural space, in which the loss of resistance is typically unequivocal, loss of resistance elicited during TPVB is very subtle and takes time to appreciate and master. The use of a glass syringe may facilitate recognition of the loss of resistance when this method is used.

Predetermined Distance Technique

TPVB can also be performed by advancing the needle by a fixed predetermined distance (1 cm) once the needle is walked off the transverse process, without eliciting loss of resistance (Figure 43–12).5–7,23 Proponents of this technique have used it very successfully with low risk of pneumothorax. The use of a depth marker is recommended to avoid inadvertent pleural or pulmonary puncture.

Placement of Thoracic Paravertebral Catheter

If a continuous TPVB (CTPVB) is planned, a catheter is inserted through a Tuohy needle into the TPVS.4,22 Unlike epidural catheterization, certain resistance is commonly encountered during insertion of the paravertebral catheter. This can be overcome by manipulating (rotating or angling) the needle or injecting 5–10 mL of saline to create a space before catheter insertion. An unusually seamless passage of catheter should arouse the suspicion of interpleural placement.

Perhaps the safest and simplest method of placing a catheter into the TPVS is to place it under direct vision from within the open chest cavity.8,25 Obviously, this requires an open thorax and is therefore done exclusively in patients undergoing a thoracotomy. This technique involves reflecting the parietal pleura from the posterior wound margin onto the vertebral bodies over several thoracic segments, thereby creating an extrapleural paravertebral pocket (Figure 43–13) into which a percutaneously inserted catheter is placed against the angles of the exposed ribs. The pleura is reapposed to the chest wall, and the thorax is closed. This method can be combined very effectively with a preincisional, single-shot, percutaneous thoracic paravertebral injection to provide perioperative analgesia during thoracic surgery.26

Indications

TPVB is indicated for anesthesia and analgesia for unilateral surgical procedures in the chest and abdomen. Commonly reported indications are listed in Table 43–1. The use of bilateral TPVB has also been reported.

Contraindications

There are very few absolute contraindications for TPVB. These include infection at the site of injection, allergy to local anesthetic drug, empyema, and a neoplastic mass occupying the paravertebral space. Coagulopathy, bleeding disorders, or patients receiving anticoagulant drugs are relative contraindications for TPVB. One must exercise caution in patients with kyphoscoliosis or deformed spines and those who have had previous thoracic surgery. The chest deformity in the former may predispose to inadvertent thecal or pleural puncture, and the altered paravertebral anatomy due to fibrotic obliteration of the paravertebral space or adhesions of the lung to the chest wall in the latter may predispose to pulmonary puncture.

Choice of Local Anesthetic

Since TPVB does not result in motor weakness of the extremities, long-lasting analgesia is nearly always desirable with TPVB. Consequently, long-acting local anesthetic drugs are typically used. These include bupivacaine or levobupivacaine 0.5% and ropivacaine 0.5–0.75%. For single-injection TPVB, 20–25 mL of local anesthetic is injected in aliquots, whereas for multiple-injection TPVB, 4–5 mL of local anesthetic is injected at each level planned. Higher concentrations of local anesthetic (eg, ropivacaine 0.75%) may reduce the onset time and prolong the duration of anesthesia and analgesia. The maximum dose of local anesthetic must be adjusted in the elderly, poorly nourished, and frail patients. The TPVS is well vascularized, leading to relatively rapid absorption of local anesthetic into the systemic circulation. Consequently, peak plasma concentration of the local anesthetic agent is attained quickly. Epinephrine (2.5–5 mcg/mL) containing local anesthetic solutions may be used during the initial injection because it reduces systemic absorption and thereby reduces the potential for toxicity. Epinephrine also helps in increasing the maximum allowable dose of local anesthetic. The duration of anesthesia after TPVB ranges from 3 to 4 h, but analgesia often lasts much longer (8–18 h). If CTPVB is planned, eg, for postoperative analgesia after thoracotomy or continuous pain relief for multiple fractured ribs, then an infusion of bupivacaine or levobupivacaine 0.25% or ropivacaine 0.2% at 0.1 to 0.2 mL/kg/h is started after the initial bolus injection and continued for 3 to 4 days or as indicated. It is our experience that using a higher concentration of local anesthetic (eg, bupivacaine 0.5% instead of 0.25%) for the CTPVB does not result in better quality of analgesia, and it may increase the potential for local anesthetic toxicity.

Practical Management of Thoracic Paravertebral Block

Breast Surgery

Thoracic paravertebral injection of local anesthetic at multiple levels (C7 through T6) in conjunction with intravenous sedation is effective for surgical anesthesia during major breast surgery (Figure 43–14).5,6,27 The C7 spinous process is the most prominent cervical spinous process; the inferior border of the scapula corresponds to T7. Compared with patients who receive only general anesthesia (GA), patients who receive a multiple-injection TPVB for major breast surgery have less postoperative pain, require fewer analgesics, and have less nausea and vomiting after surgery. However, to effectively use the multiple-injection TPVB technique for anesthesia during breast surgery, one must understand the complex innervation of the breast. The anterior and lateral chest wall receives sensory innervation from the anterior and lateral cutaneous branches of the intercostal nerves (T2 through T6), the axilla (T1 to T2), the infraclavicular region from the supraclavicular nerves (C4 to C5), and the pectoral muscles from the lateral (C5 to C6) and medial (C7 to C8) pectoral nerves. There also may be overlapping sensory innervation from the contralateral side of the chest. This complex innervation of the breast from the C4 to T6 spinal segments explains why TPVB may not provide complete anesthesia for dissection over the pectoral muscle or the infraclavicular region. However, this can be overcome with proper sedation during surgery as well as by injections of local anesthetic by the surgeon intraoperatively into the sensitive areas. Injection of a local anesthetic subcutaneously along the inferior border of the clavicle or to perform an ipsilateral superficial cervical plexus block, in order to anaesthetize the supraclavicular nerves (C4 to C5) will minimize discomfort and sedative and analgesic requirements during surgery. A combination of midazolam, or propofol infusion, or IV opioid can be used to provide comfort to the patients intraoperatively. Dexmedetomidine, a highly selective α2-adrenoceptor agonist, with its sedative, analgesic, and minimal or no respiratory depression properties is a useful alternative for sedation during breast surgery under TPVB.

When combined with general anesthesia, a single-injection TPVB with ropivacaine (2 mg/kg diluted to 20 mL with 0.9% saline) with 1:200,000 epinephrine, performed prior to the induction of GA can be used. This provides excellent postoperative analgesia, reduces postoperative analgesic requirement, reduces postoperative vomiting, facilitates the earlier resumption of oral fluid intake, reduces the postoperative decline in respiratory function, and augments the recovery of postoperative respiratory mechanics.

Postthoracotomy Pain Relief

CTPVB is an effective method of providing analgesia after thoracotomy (Figure 43–15). Ideally, TPVB should be established before the thoracotomy incision, via a catheter that is inserted percutaneously, and continued for 4 to 5 days after surgery. However, if an extrapleural paravertebral catheter is being placed under direct vision from within the chest during surgery, then a single-injection TPVB can be performed at the level of the thoracotomy incision before the surgical incision, and a continuous infusion of local anesthetic is commenced after the catheter placement. Either method provides effective perioperative analgesia.

It is important to note that CTPVB is inadequate on its own for complete pain relief after a thoracotomy and must be combined with an opioid [best as intravenous patient-controlled analgesia (IVPCA)] and a NSAID to provide optimal analgesia.26 Analgesia achieved by CTPVB is comparable to epidural analgesia but with less hypotension, urinary retention, and the side effects commonly seen with epidural opioid administration.1,26,28,29 The opioid requirement with such an approach is significantly reduced by the CTPVB, and analgesia is superior to IVPCA alone.1,30

Multiple Fractured Ribs

TPVB is an effective method of providing pain relief in patients with unilateral multiple fractured ribs.1,22,23 A single thoracic paravertebral injection of 25 (SD 5) mL of bupivacaine 0.5% produces pain relief for a mean duration of 9.9 (SD 1.2) h and improves respiratory function and arterial blood gases.1,23 To avoid recurrence of pain and deterioration in respiratory function, a thoracic paravertebral catheter can be inserted midway between the highest and the lowest fractured rib, and a CTPVB can be commenced after administration of the initial bolus injection. CTPVB in combination with a NSAID provides continuous pain relief and produces a sustained improvement in respiratory parameters and arterial oxygenation.22 Since TPVB does not cause urinary retention or affect lower limb motor function, it is useful in patients with multiple fractured ribs who also have concomitant lumbar spinal trauma since it also allows continuous neurologic assessment for signs of spinal cord compression.31

Pharmacokinetic Considerations

Relatively large doses of local anesthetics are commonly used during CTPVB. Therefore there is the potential for local anesthetic toxicity, and patients should be closely monitored during CTPVB and the infusion stopped if signs develop. During a prolonged thoracic paravertebral infusion there is progressive accumulation of local anesthetic in the plasma, and the plasma concentration of the drug may exceed the threshold for central nervous system toxicity (eg, 2–4.5 mcg/mL for bupivacaine). Despite the systemic accumulation, local anesthetic toxicity is rare. This may be the case because, although the total plasma concentration of the local anesthetic increases postoperatively, the free fraction of the drug remains unchanged32 and may be due to the postoperative increase in α1-acid glycoprotein concentration,32 the protein that binds to local anesthetic drugs. There is also a greater increase in the S-bupivacaine enantiomer,33,34 which is associated with lower toxicity, than the R-enantiomer. Due to concerns of systemic accumulation and local anesthetic toxicity with prolonged paravertebral infusion, it is preferable to use a local anesthetic with lower potential for toxicity, such as ropivacaine. One must also exercise caution in the elderly and frail patients as well as in patients with impaired hepatic and renal function.

Complications & How to Avoid Them

Based on published data the incidence of complications after TPVB is relatively low and varies from 2.6 to 5%.1,5,35,36 These include vascular puncture (3.8%), hypotension (4.6%), pleural puncture (1.1%), and pneumothorax (0.5%).35 Unlike with thoracic epidural anesthesia, hypotension is rare in normovolemic patients after TPVB because the sympathetic blockade is unilateral. However TPVB may unmask hypovolemia and result in hypotension. Therefore TPVB should be used with caution in patients who are hypovolemic or hemodynamically labile. Nevertheless, hypotension is rare even after bilateral TPVB, probably owing to the segmental nature of the bilateral sympathetic blockade.

Pleural puncture and pneumothorax are two complications that often dissuade anesthesiologists from performing a TPVB. Inadvertent pleural puncture is uncommon after TPVB and may or may not result in a pneumothorax, which is usually minor and can be managed conservatively. Clues that suggest pleural puncture during a TPVB are a gritty pleural pop sensation, irritating cough, onset of sharp chest or shoulder pain, or sudden hyperventilation. Contrary to common belief, air cannot be aspirated through the needle unless the lung is also inadvertently punctured or air that may have entered the pleural cavity during removal of the stylet is aspirated. Such patients should be closely monitored for the possible development of a pneumothorax. It should be kept in mind that pneumothorax may be delayed in onset and a chest radiograph taken too early to exclude a pneumothorax may not be conclusive. Even a radiologic contrast study using a chest radiograph may be difficult to interpret because the intrapleural contrast disperses rapidly, does not define any specific anatomic plane, and tends to spread to the diaphragmatic angles or horizontal fissure.

Systemic local anesthetic toxicity can occur due to inadvertent intravascular injection or from using an excessive dose of local anesthetic. The local anesthetic solution must be injected in aliquots, and the dosage must be adjusted in the elderly and frail patient. An epinephrine-containing local anesthetic solution is suggested to enable the recognition of intravascular injection and reduce the systemic absorption of the local anesthetic.

Inadvertent epidural, subdural, or intrathecal injection and spinal anesthesia can also occur. Published data suggest that these complications are more frequent when the needle is directed medially but may also occur with a normally positioned needle due to the close proximity of the needle to the dural cuff and intervertebral foramen. Therefore the needle must never be directed medially, and care must be taken to exclude intrathecal injection by routinely performing an aspiration test before injection. Transient ipsilateral Horner syndrome can occasionally develop after TPVB. This is due to cephalad spread of the local anesthetic to the stellate ganglion or to the preganglionic fibers of the first few segments of the thoracic spinal cord. Bilateral Horner syndrome has also been reported and may be due to epidural spread or prevertebral spread to the contralateral stellate ganglion. Sensory changes in the arm and lower extremity may also occur after a TPVB. The former is due to spread of local anesthetic to the lower components of the ipsilateral brachial plexus (C8 and T1), and the latter is due to extended subendothoracic fascial spread to the ipsilateral retroperitoneal space where the lumbar spinal nerves are located (discussed earlier), but epidural spread as a cause cannot be excluded. Motor blockade or bilateral symmetrical anesthesia involving the lower extremity is rare. It generally suggests significant epidural spread and may be more common if large volumes of local anesthetic (>25–30 mL) are injected at a single level. Therefore if a wide segmental spread of anesthesia is desired, it is preferable to perform the multiple-injection technique or inject a smaller volume of local anesthetic at several levels a few dermatomes apart.

Lumbar paravertebral block (LPVB) is technically similar to a TPVB but due to differences in anatomy between the thoracic and lumbar paravertebral spaces the two paravertebral techniques are described separately. LPVB is technically simple to perform and used most commonly in combination with a TPVB, as a thoracolumbar paravertebral block, for surgical anesthesia during inguinal herniorrhaphy.

Anatomy

The lumbar paravertebral space (LPVS) is limited anterolaterally by the psoas major muscle; medially by the vertebral bodies, the intervertebral disks, and the intervertebral foramen with its contents; and posteriorly by the transverse process and the ligaments that are interposed between the adjoining transverse processes. Unlike the TPVS, which contains adipose tissue, the LPVS is occupied primarily by the psoas major muscle. The psoas major muscle is made up of a fleshy anterior part that forms the main bulk of the muscle, and a thin accessory posterior part.37 The main bulk originates from the anterolateral surface of the vertebral bodies and the accessory part originates from the anterior surface of the transverse process.37 The two parts fuse to form the psoas major muscle except near the vertebral bodies where the two parts are separated by a thin fascia within which lie the lumbar spinal nerve roots and the ascending lumbar veins.37 The ventral rami of the lumbar spinal nerve roots extend laterally in this intramuscular plane formed by the two parts of the psoas major muscle and form the lumbar plexus within the substance of the psoas major muscle.37 The psoas muscle is enveloped by a fibrous sheath, “the psoas sheath,” which continues laterally as the fascia covering the quadratus lumborum muscle. During a LPVB the local anesthetic is injected anterior to the transverse process into a triangular space between the two parts of the psoas major muscle containing the lumbar spinal nerve root.

The LPVS communicates medially with the epidural space. A series of tendinous arches extends across the constricted parts of the lumbar vertebral bodies, which are traversed by the lumbar arteries and veins and sympathetic fibers. These tendinous arches may provide a pathway for the spread of local anesthetic from the LPVS to the anterolateral surface of the vertebral body, the prevertebral space, and the contralateral side and may be the pathway through which the ipsilateral lumbar sympathetic chain may occasionally be involved.

Mechanism of Block & Distribution of Anesthesia

A lumbar paravertebral injection produces ipsilateral dermatomal anesthesia (Figure 43–16) by a direct effect of the local anesthetic on the lumbar spinal nerves and by medial extension into the epidural space via the intervertebral foramen. The contribution of epidural spread to the overall distribution of anesthesia after a LPVB is unknown but probably occurs in the majority of patients and depends on the volume of local anesthetic injected at a given level. Ipsilateral sympathetic blockade may also occur due to epidural spread or spread of local anesthetic anteriorly via the tendinous arches to the rami communicantes or the lumbar sympathetic chain.

Technique

Lumbar paravertebral block can be performed with the patient in the sitting, lateral, or prone position. Surface landmarks must be identified and marked with a skin marker before block placement. The spinous process of the vertebra at the levels to be blocked represents the midline, the iliac crest corresponds to the L3-4 interspace, and the tip of the scapula corresponds to the T7 spinous process. Skin markings are also made 2.5 cm lateral to the midline at the levels that are to be blocked (Figure 43–17) or one can draw a line 2.5 cm lateral to the midline and perform the injections along this line. A standard regional anesthesia tray is prepared; strict asepsis should be maintained during block placement. An 8-cm, 22-gauge, Tuohy or Quincke tip spinal needle (see Figure 43–8) is used for LPVB. Similarly to the recommendations for TPVB, the use of needles with depth markings on the shaft of the needle or a guard indicating the depth (see Figure 43–8) is recommended.

Advancing the needle by a fixed predetermined distance (1 cm) beyond the transverse process, without eliciting paresthesia, is the method most commonly used to perform LPVB. The block needle is inserted perpendicular to the skin until the transverse process is contacted. The depth at which the transverse process is contacted is variable (4–6 cm) and depends on the build of the patient. Once the transverse process is identified, the marking on the needle is noted or the depth marker is adjusted so that it is 1 cm beyond the skin–transverse process depth. The needle is then withdrawn to the subcutaneous tissue and reinserted at a 10- to 15-degree superior or inferior angle so that it slides off the superior or inferior edge of the transverse process, similarly to the technique in thoracic paravertebral block (see Figure 43–11). The needle is advanced by a further 1 cm beyond the point at which it made contact with the transverse process or until the depth marker is reached. After negative aspiration for blood or CSF, the local anesthetic is injected. Since spread of local anesthetic after a single large-volume lumbar paravertebral injection is unpredictable, the multiple-injection technique in which 4–5 mL of local anesthetic is injected at each level is more commonly used.

Choice of Local Anesthetic

As for TPVB, long-acting local anesthetic agents such as bupivacaine 0.5%, ropivacaine 0.5–0.75%, or levobupivacaine 0.5% are commonly used for LPVB. During a multiple-injection LPVB, 4–5 mL of the local anesthetic is injected at each level. Anesthesia develops in about 15–30 min and lasts for 3 to 6 h. Analgesia is also long-lasting (12–18 h) and generally outlasts the duration of anesthesia. There are no data on the pharmacokinetics of local anesthetic after LPVB. Nevertheless, the addition of epinephrine (2.5–5 mcg/mL) to the local anesthetic may reduce systemic absorption and reduce the potential for toxicity.

Indications & Contraindications

The indications for LPVB are limited. Published data suggest that it is most commonly used in combination with TPVB (T10 through L2) for surgical anesthesia during inguinal herniorrhaphy. It can also be used for diagnostic purpose during evaluation of groin or genital pain, such as that following nerve entrapment syndrome after inguinal herniorrhaphy. Contraindications for LPVB are similar to TPVB, but one must exercise caution in patients who are anticoagulated or are receiving prophylactic anticoagulants since psoas hematoma with lumbar plexopathy has been reported.

Complications & How to Avoid Them

Published data suggest that complication is rare after LPVB.38,39 Nevertheless, it is possible to inadvertently inject local anesthetic into the intravascular, epidural, or intrathecal spaces during LPVB and may be more common if the needle is directed medially. Therefore the direction of the block needle should be maintained perpendicular to the skin during insertion, and medial angulation should be avoided. Intraperitoneal injection or visceral injury (renal) may also occur, although this can occur only as a result of gross technical error. Motor weakness involving the ipsilateral quadriceps muscle may result if the L2 spinal nerve is blocked (femoral nerve L2 to L4).

Paravertebral block is conceptually a simple technique with few contraindications. Proper training is necessary to acquire stereotactic skills required to ensure a high success rate. Thoracic paravertebral block produces unilateral somatic and sympathetic nerve blockade that is adequate for surgical anesthesia during breast surgery and for analgesia when pain is of unilateral origin from the chest or abdomen. Lumbar paravertebral block is less commonly used in clinical practice. As a thoracolumbar paravertebral block it is effective for surgical anesthesia during inguinal herniorrhaphy. Hemodynamic stability is usually maintained after a paravertebral block due to the unilateral nature of sympathetic blockade. Bladder and lower limb motor function is also preserved, and no additional nursing vigilance is required during the postoperative period. Bilateral paravertebral block has also been reported, but its role in clinical practice is still to be defined.