Chapter 69. Sympathetic Blocks

Introduction

Sympathetic blocks are widely employed for both diagnostic and therapeutic purposes. Kappis originally used paravertebral sympathetic blocks1 as treatment for severe pain and visceral pain syndromes. Mandl2 first introduced percutaneous interruption of the sympathetic chain in the early 20th century, and for many years thereafter it was a mainstay therapy for vascular insufficiency of the lower extremities. Current indications for sympathetic blocks include diagnosis of sympathetically maintained pain, treatment of neuropathic pain states such as acute herpes zoster, post-herpetic neuralgia, or other sympathetically maintained pain syndrome (reflex sympathetic dystrophy or causalgia, also known as complex regional pain syndrome), and management of ischemic pain. Sympathetic blocks are also used to help differentiate somatic from sympathetic pain origins. Pain syndromes responsive to initial sympathetic blocks are then treated with repeated blocks or followed up with surgical, chemical, or radiofrequency sympathectomy.

A good working knowledge of the sympathetic nervous system helps to understand how various neuraxial, plexus, and regional blocks can achieve sympathectomy. Descending autonomic projections from the hypothalamus, the oculomotor (Edinger-Westphal) complex, the locus ceruleus, and the nucleus of the solitary fasciculus terminate in the ipsilateral intermediolateral cell column in thoracic and upper lumbar spinal cord segments. Within this cell column lie the cell bodies of the preganglionic sympathetic neurons. Axons from these preganglionic cells exit the spinal cord by the anterior spinal roots and white rami communicantes to the sympathetic chain ganglia located along the left and right anterolateral margins of the spinal column. Upon reaching these paravertebral ganglia, the preganglionic sympathetic axons may synapse, pass cephalad or caudad for variable distances within the sympathetic chain before synapsing, or continue uninterrupted to a more distant ganglion or plexus, such as the celiac or hypogastic plexus. The nerves that bypass paravertebral sympathetic chain ganglia to more distant ganglia are called splanchnic nerves. Splanchnic nerves are the primary sympathetic fibers that innervate visceral organs. The ganglia in which they synapse are typically located near the respective organs that they innervate. Post-ganglionic sympathetic fibers then course along peripheral nerves or blood vessels to converge on specific organs. Once it is understood that the preganglionic sympathetics have spinal origins, and that the spread of sympathetic nerves occurs along blood vessels and peripheral nerves, it becomes easier to understand how sympathectomies can be performed not only through blockade of specific chain ganglia, but through a various number of neuraxial and regional block techniques.

Knowing the position of the sympathetic chain relative to somatic nerves helps to predict some of the side effects associated with the various sympathetic blocks. The sympathetic chain ganglia extends from the second cervical vertebra to the coccyx. In the cervical and thoracic region, these ganglia lie anterior to the base of the transverse processes or the head of the ribs; therefore they lie in close proximity to the somatic nerves. However, as the sympathetic chain courses caudally toward the lumbar region, it becomes more anterolateral to the vertebral bodies and becomes separated from somatic nerves by the psoas muscle. As a result, sympathetic blocks performed in the lumbar region become less prone to inadvertent somatic nerve blocks.

Another point to recognize is that visceromotor and nociceptive pathways course along with sympathetic fibers. The sympathetic chain receives afferent visceral fibers that conduct pain from the head, neck, abdominal and pelvic viscera, and extremities. The celiac and superior hypogastric plexi have parasympathetic and visceral nociceptive afferents; lumbar and cervicothoracic (including the stellate) ganglia have visceral nociceptive afferents as well. Therefore, sympathetic blocks are not purely sympathetic.

Patient Preparation

The patient should not be overly sedated during the procedure because verbal contact with the patient is extremely valuable. During diagnostic blocks, sedation may confound results because the sedative can affect the complex brain pathways involved with sympathetically maintained pain. Monitoring and intravenous access should be employed on the basis of the type of block performed as well as the health and mental condition of the patient. For sympathetic blocks involving the limbs, skin temperature probes are placed bilaterally on the extremities undergoing sympathetic block. The block is considered adequate if cutaneous temperature of the treated limb approaches core temperature.3 A careful evaluation of placebo effects, systemic uptake of drug, and blockade of somatic nerves must be performed in patients who have obtained relief following a sympathetic block. As with any invasive procedure, resuscitation equipment and drugs should be readily available. Major contraindications to sympathetic blocks include coagulopathy and patient refusal.

Anatomy

The cervical chain is composed of a superior, middle, and inferior cervical ganglion; the inferior ganglion is fused with the first thoracic ganglion, resulting in a “starlike” (stellate) appearance. It receives preganglionic sympathetic fibers via white rami communicantes from the intermediolateral cell column of T1 to T6 in the spinal cord. It is an oval-shaped structure approximately 2-cm long, 1-cm wide, and about 0.5-cm thick. The ganglion lies anterior to the first rib, extends along the C7 to T1 interspace, and may lie over the anterior tubercle of C7. It is bound inferiorly by the dome of the pleura, medially by the longus colli muscle, and laterally by the scalene muscles. It is also bound anteriorly in part by the subclavian artery and the vertebral artery, and posteriorly by the transverse processes of C7 and T1. The prevertebral fascia, which originates posterior to the sympathetic chain in the cervical region, is pierced by the chain around C7 and becomes anterior to the stellate ganglion as the fascia forms a transition from the neck to the chest. Superior to the stellate ganglion is the transverse process of the sixth cervical vertebrae, or Chassaignac’s tubercle, a prominence that is easily palpable along the paratracheal region of the neck.

One must remember that while Chassaignac’s tubercle is the major landmark for performing the anterior paratracheal block of the stellate ganglion, the location of the ganglion itself is inferior to the tubercle. Undoubtedly, it is the presence of Chassaignac’s tubercle that has made the anterior paratracheal approach to this ganglion a popular one (compared to the lateral and posterior approaches) among pain specialists. It serves as bony protection for the vertebral artery, thus protecting the artery from unintended injection of local anesthetic and resultant seizure. It is also easily palpable, especially in the sitting position, and with adequate deep palpation, the tubercle becomes almost subcutaneous and minimizes the distance from the skin to the tubercle through which the needle must pass. Interestingly enough, ultrasonography and magnetic resonance imaging (MRI) studies suggest that local anesthetic spread to the ganglion does not occur; rather, the spread occurs anterior to the ganglion.4,5 Other radiographic and injection studies have supported this finding as well.6–9 This anterior spread likely relates to prevertebral fascia being in the same plane as Chassaignac’s tubercle at the C6 vertebra but then becomes more anterior at the stellate ganglion, thus preventing the spread of injectate onto the ganglion. The presence of this fascia also promotes mediastinal and even contralateral spread of injectate.5 Therefore, sympathetic neural blockade during stellate ganglion block may take place at sites other than the stellate ganglion.

Indications

The stellate ganglion block is one of the most commonly used procedures in pain management of the face and upper extremity. Painful syndromes that may benefit from stellate ganglion blocks include sympathetically maintained complex regional pain syndrome (formerly RSD or causalgia), phantom limb pain or amputation stump pain, herpes zoster and postherpetic neuralgia, frostbite, or tumor invasion of neurovascular or boney structures. Other indications include circulatory insufficiency of the arm in which thromboembolic or vasospastic events have occurred (Table 69-1).

Technique

The anterior paratracheal approach is described. It is the easiest to perform (compared to the posterior technique10) and involves a minimal amount of risk when performed correctly. It is also the least painful for the patient. The patient is placed in the supine position with the mouth slightly opened to relax the anterior muscles of the neck. The operator stands on the side of the neck to be blocked, palpates the cricoid cartilage, then slides his or her index and middle fingers laterally to palpate deep into the groove in the neck created by the trachea and the sternocleidomastoid muscle and major vessels of the neck. With deep, gentle palpation and slight lateral retraction, the sternocleidomastoid muscle and major vessels are drawn to the side; the tubercle of the sixth cervical transverse process (Chassaignac’s tubercle) can then be easily felt (Fig. 69-1). In patients with short or muscular necks, it becomes more difficult to palpate the tubercle. Placing a slight lift under the patient’s back or sitting the patient up and supporting the back of the neck with the operator’s other hand may help to locate the tubercle. The tubercle is then straddled by the index and middle finger.

A 2.5-cm, 22-gauge, short-beveled needle attached to an intravenous pediatric T-piece or other suitable extension tubing is connected to a syringe containing the local anesthetic injectate. The use of extension tubing allows for better control of the needle during placement, aspiration, and injection. The operator uses his or her nondominant hand to straddle Chassaignac’s tubercle and manipulates the needle with the dominant hand (Fig. 69-2). The needle is advanced though the skin until the tubercle is contacted. Often the distance advanced is not more than 1.5 to 2.0 cm. An assistant aspirates for blood, then injects 1.0 mL of local anesthetic; the patient is then evaluated for inadvertent arterial or intraneural injection. Arterial injection is suggested by seizure activity immediately following injection, while intraneural injection is suspected if radiating dysethesia occurs on injection. If these observations are negative, 10 to 20 mL of local anesthetic are incrementally injected. If sympathetic block of the arm is desired, moving the patient to a sitting position as soon as the block is placed may facilitate caudal spread of the agent.

Other means to assist in appropriate needle placement include ultrasound,4 fluoroscopy or CT guidance (Fig. 69-3). If a sympathectomy is not achieved when the stellate ganglion block is performed at Chassaignac’s tubercle, a repeat block at the C7 or T1 transverse process should be considered in an attempt to inject local anesthetic on the same side of the prevertebral fascia as the ganglion. Note that a block at this level increases the risk of brachial plexus block; since the C7 tubercle is rather vestigial, the injectate is closer to the same plane as the brachial plexus. Occasionally, the C7 tubercle can be palpated and the needle is entered directly over this tubercle; otherwise, the needle is entered one finger breadth (1.5 to 2.0 cm) below the C6 tubercle. The risk of pneumothorax is also increased because the injection site is near the pleural dome. Larger volumes (20 mL) can improve the likelihood of a complete sympathectomy of the arm and hand (C5-T1 dermatormes)7 but is associated with a significant incidence of hoarseness (80%), dysphagia (60%), and brachial plexus block (10%) due to spread of local anesthetic onto adjacent laryngeal nerves and cervical nerve roots.

Some means to evaluate the presence of sympathectomy must be performed. While a Horner’s sign (ipsilateral ptosis, miosis, anhydrosis, and conjunctival engorgement) is indicative of a sympathectomy of the head and face, it in no way suggests a sympathectomy of the arm and hand. Skin surface temperature probes placed bilaterally at the palmar thenar regions are simple yet effective. A 1.0° to 1.5° C increase in the blocked side or, perhaps more specifically, an increase in temperature toward core temperature that exceeds that of the contralateral side11,12 is strongly suggestive of a successful sympathetic block of the arm. Somatic block of the arm must also be ruled out.

Complications

Minor complications are common. Because the proximity of laryngeal nerves to the stellate ganglion, dysphagia and hoarseness are common with the anterior paratracheal approach. Following stellate ganglion block, incidental recurrent laryngeal nerve block or superior laryngeal nerve block is identified by the patient’s inability to say “ee” or swallow a small amount of water or other clear liquid. The incidence of brachial plexus block is as high as 10%,7,13 so the presence of motor or sensory block should be assessed before discharging the patient from the clinic facility.

Even without the use of imaging techniques, serious complications to stellate ganglion block are rare. Transient central nervous system (CNS) events such as seizures, aphasia, blindness, loss of consciousness, and hemiparesis can occur following injected doses as low as 15 mg of lidocaine or 2.5 mg of bupivacaine.14–17 Because of these risks some physicians advocate placement of intravenous lines in all patients undergoing stellate ganglion blocks. Nonetheless, appropriate noninvasive monitoring and resuscitation equipment should be readily available and used as the clinical scenario dictates.

Anatomy

The celiac plexus is a dense matrix of diffuse nerve fibers and ganglia located around the abdominal aorta and periaortic space at the level of the T12 and L1 vertebrae. The most distinct feature of the celiac plexus are the paired semilunar (“celiac”) ganglia that lie immediately superior to the pancreas in the midline and are flanked in close approximation by the adrenals. These “paired” ganglia can actually vary in number and size.18 The aorta is surrounded by the plexus, which makes this large vascular structure an important landmark in performing the block. In fact, transgression of the aorta has been used in identifying needle placement.19 In addition to the celiac ganglia, the components of the celiac plexus include the greater, lesser, and least (also called lowest) splanchnic nerves; there are also contributions from the aorticorenal ganglia and aortic and superior hypogastic plexus. It is important to realize that the celiac plexus is not a distinct entity but a diffuse network that varies in size, network, and position. The most consistent landmark is the celiac artery because these elements intertwine around the base of this artery.

There are sympathetic, parasympathetic, and visceral afferent contributions to the celiac plexus. The sympathetic fibers originate from the thoracic sympathetic chain via the greater and lesser splanchnic nerves, and the visceral afferents have cell bodies that originate from the dorsal root ganglion of the spinal cord and travel with the sympathetic nerves. The parasympathetics originate from the vagus nerve and sacral nerve roots. The nerves of the celiac plexus innervate most of the abdominal viscera to include the pancreas, liver, kidneys, biliary tract, spleen, adrenals, intestines, and omentum.

Indications

The celiac plexus block is indicated for patients in pain from upper abdominal tumors such as pancreatic cancer. Pain relief rates vary from 70% to 100%, with an average of 85% of patients that experience at least temporary pain relief.20,21 Pain from these tumors can be severe, and opioid therapy is often limited by the sedation and constipation that accompany the high doses required to manage the patient’s discomfort. Neurolytic celiac plexus blocks in these patients can provide superior pain relief for up to 3 to 4 months. In most patients relief will be immediate and effective. Furthermore, they can lessen the severity of opioid-induced side effects by decreasing requirements of these drugs. Gastointestinal motility is also improved by the sympathectomy caused by the block. The predictive value of a neurolytic celiac plexus block can be determined by the degree of tumor invasion. Akhan et al22 found that the grade of tumor as measured by invasion of periaortic and paracaval fat planes was a good predictor for successful neurolytic celiac plexus block. Greater than 50% invasion of the fat planes correlated with little pain relief. Age, history of laparotomy, chemotherapy, or radiation therapy have not been shown to decrease the efficacy of neurolytic celiac plexus blocks.

Benign conditions such as acute and chronic pancreatitis may also respond to celiac plexus blocks. As with pancreatic cancer patients, acute pancreatitis is often resistant to opioid therapy; furthermore, the disease process may be improved by decreasing the ductal and sphincter spasm thought to be associated with acute pancreatitis. Addition of steroids to the local anesthetic injectate has been shown to decrease the severity of the attack.23 Continuous catheter techniques can be effective in chronic alcoholic patients diagnosed with acute pancreatitis who were previously unresponsive to epidural analgesia. Rykowski et al24 used 0.5% bupivacaine, 20 mL every 6 to12 hours as intermittent injection, or 0.5% bupivacaine at 6 mL per hour with good results. Using celiac plexus blocks, especially neurolytic celiac plexus blocks in chronic pancreatitis, is controversial. While 4 to 6 months of relief can be obtained from neurolytic celiac plexus blocks, a subset of alcoholic patients may view their pain-free state as an opportunity to resume their consumption of alcoholic beverages. Furthermore, because this block also interrupts the visceral afferents from abdominal organs, it may mask pain related to intraabdominal emergencies. Benefits to performing celiac plexus blocks in chronic pancreatitis patients include pain control that is superior to narcotics and an improved appetite. Often these patients are malnourished, and analgesia using celiac plexus blocks can improve their nutritional state by allowing them to eat meals without pain. The addition of steroids to the injectate has been shown to improve analgesia without the use of neurolytic agents25 in the patient with chronic pancreatitis. Regardless of controversy, celiac plexus blocks have shown to be an effective adjunct in managing chronic pancreatitis pain.26 Indications for celiac plexus blocks are summarized in Table 69-2.

Technique

There are a variety of techniques for approaching the splanchnic nerves or celiac plexus. In general, they can be summarized as posterior or anterior approaches. The posterolateral approach has become the most practiced and proven technique by anesthesiologists, whereas the anterior techniques using computed tomography (CT) or ultrasound guidance are preferred by invasive radiologists. In all cases, noninvasive monitoring should be used and an intravenous line should be established. Intravenous vasoactive agents, volume expanders (crystalloid or colloids), and sedative and analgesics should be made available for use as needed.

Posterolateral Approaches

Posterolateral techniques allow access to both the splanchnic nerves and the celiac plexus. The posterolateral approach is one originally defined by Kappis and refined by Moore.27 Frequently used variations of the posterolateral approach include the transcrural approach, the transaortic approach, and the retrocrural or deep splanchnic approach.

The patient is placed in a prone position with a pillow placed at the midsection of the abdomen. This minimizes the lumbar lordosis and aids in patient comfort. Occasionally, the abdominal pain can be so severe that the prone position is not tolerated, and analgesics must be used or the patient must be positioned in the lateral decubitus position. The arms are underneath behind the head or allowed to hang off the table. An intravenous line is placed to provide light sedation if necessary, and a 200 to 500 mL crystalloid bolus is administered to offset the sympathectomy-induced hypotension caused by the block. Anatomic landmarks are identified and marked in ink. Agents typically used for the celiac plexus block include 0.25% to 0.5% bupivacaine (with or without 80-mg methylprednisolone or equivalent), 6% to 10% phenol, or 50% to 100% alcohol. Volumes are described for each technique (see following sections).

The classic posterior approach is a two-needle technique; needle placement is similar for both sides. Landmarks include the 12th ribs and the T12 and L1 spinous processes; fluoroscopic or CT guidance helps with landmark identification and minimizes complications during needle placement and injection. A shallow isosceles triangle is formed by these three points. The lateral points should lie 6 to 9 cm from the midline and usually correspond to the junction of the paraspinal muscles and the 12h rib. After administering local anesthetic to create a skin wheal at this point, a 12- to 15-cm, 20- to 22-gauge subarachnoid needle is inserted percutaneously and angled at 45 degrees to the coronal plane and about 15 degrees cephalad. The needle is advanced until contact with the lateral body of L1 is made. This typically occurs at the depth of 8 to 10 cm; if bony contact is made at a more shallow depth than this, it is likely that the transverse process has been encountered. The needle is then withdrawn (almost subcutaneously) and the needle tip is redirected laterally an additional 10 degrees and readvanced; this next attempt should contact bone about 2 to 3 cm deeper than the previous attempt. This maneuver is repeated until the needle is “walked off” the lumbar body (Fig. 69-4). The final placement of the needle tip is 1.0 to 1.5 cm anterior to the vertebral margin. If the first needle was placed on left side, correct needle placement is confirmed by observing the needle pulsate on visual inspection and tactile analysis. Needle pulsation occurs because the final position of the needle tip is often close to the aorta. The second needle is placed on the right side using the same technique as the first; depth is guided by the final needle depth used on the left side. Fluoroscopy can be used to confirm tip placement; spread of contrast agent seen on fluoroscopy will indicate retrocrural, transcrural, transaortic, or intradiaphragmatic injection of agent (Figs. 69-5 and 69-6). If CT imaging is used, needle paths are traced from the skin to the celiac plexus to avoid injury to renal or vascular structures.

For the transcrural approach, advancing the needle tips an additional 1 to 2 cm will pierce the diaphragmatic crus and place the needle tip anterior to the diaphragm. A loss of resistance is usually felt as the crus is pierced. The anteroposterior (AP) and lateral radiographs with contrast will show a linear spread in the left lateral preaortic area. If contrast spread is predominately cephalad and appears to collect around the L1 vertebral body, the needle tip is likely to be retrocrural. Lateral radiographs can confirm that the contrast is posterior and superior to the diaphragm, also suggesting retrocrural spread. The procedure can then be performed as a deep splanchnic nerve block (see later section), or the needle is advanced to pierce the diaphragmatic crus (thus transcrural). If muscle striations are seen following contrast injection, the needle tip is likely contained within diaphragmatic muscle, and should be advanced about 1 cm. On lateral fluoroscopy, contrast agent is typically seen to spread in a cranio-caudal direction anterior to the vertebral body, but agent spread is limited to below the diaphragm (see Fig. 69-5B, contrast patttern, and Fig. 69-6B). Following negative aspiration of each needle, 15 to 25 mL of local anesthetic or neurolytic agent is injected through each needle in divided doses.

The transaortic approach is a single needle, left-sided technique that is also transcrural.19 The intent of this approach is to pierce the aorta with the needle to ensure that the needle tip is anterior to the aorta. Placement of the injectate anterior to the aorta can minimize the risk of neurologic complications caused by unintended spread of neurolytic agents to the lumbar plexus. Needle placement is the same as for the transcrural approach, but the needle is advanced until aortic wall penetration occurs and free-flowing blood is aspirated. The needle is then advanced further through the anterior wall of the aorta until no blood is aspirated.

A 5-mL loss of resistance syringe filled with saline can be used to identify anterior aortic wall penetration. Once blood is aspirated through the block needle, the loss of resistance syringe is attached to the needle and constant pressure is applied to the syringe plunger. A resistance to injection will be felt once the anterior aortic wall has been contacted, followed by loss of resistance once the needle tip has entered the anterior periaortic space. Following negative aspiration, contrast agent is injected and will appear anterior to the vertebral bodies (see Fig. 69-5C and Fig. 69-6A). Local anesthetic, steroid, or neurolytic agent is then injected. A smaller total volume of agent (20 to 25 mL) is used for this technique.

Anterior Approach

With the anterior approach, a 12- to 15-cm, 22-gauge needle is passed through the midline epigastrium until the body of L1 is contacted. The needle is then withdrawn 1.0 to 1.5 cm and placement is confirmed using fluoroscopy, ultrasound, or CT imaging.28,29 Patient comfort is a major advantage to this approach, especially when the patient is unable to lie prone. Only one needle is used with this technique, so there is less pain from posterior two-needle approaches. Furthermore, the risk of needle-related injury to motor nerves is significantly reduced compared to posterior approaches.

Splanchnic Nerve Blocks

An alternative technique to achieve abdominal sympathectomy and visceral nerve block is the splanchnic nerve block. The splanchnic nerve block specifically interrupts the sympathetic imput to the celiac plexus without blocking the abdominal parasympathetics. The final position of the needle tip is superior to the diaphragm; the intention is to block the greater, lesser, and least splanchnic nerves before they traverse the diaphragm into the abdomen. The advantages of performing sympathectomy and visceral nerve block are multifold. Gastrointestinal motility is improved compared with the celiac plexus block because the parasympathetics (which join the splanchnics at the level of the celiac ganglia) are left unopposed. Also, because the lumbar sympathetics are not blocked by this technique, hypotension is decreased. Lastly, with the classic splanchnic nerve block, a smaller volume of local anesthetic or neurolytic agent can be used (3 to 4 mL per side).

For the deep splanchnic approach30,31 (also known as the retrocrural celiac plexus block), landmarks and needle approach are similar to the transcrural celiac plexus block. The needle is walked off the vertebral body and advanced until the needle pulsates (due to the proximity of the needle tip to the aorta) on visual inspection and tactile analysis. When the block is performed correctly, 3- to 5-mL injection of contrast will remain within the retrocrural space and migrate primarily cephalad (see Fig. 69-5A). On fluoroscopic AP view, the contrast will be confined along the lateral border to the L1 vertebral body (see Fig. 69-6A). On lateral view, layering of the contrast in a narrow line along the anterior vertebral column should be seen. The procedure is then repeated on the right side. Fifteen milliliters of local anesthetic or neurolytic agent are injected through each needle. Parasympathetics and the lumbar sympathetic chain are not blocked with this technique.

The classic splanchnic nerve block is performed in a manner similar to the deep splanchnic approach, but the needle is directed toward the anterolateral margin of T12 vertebral body. A paramedian approach is used, inserting two 7- to 10-cm needles 3 to 4 cm lateral to the midline just below the 12th ribs, then directing the needle tips toward the T12 body. Radiographic contrast patterns are similar to the deep splanchnic nerve block. The disadvantages of this block relate to final position of the needle tips; compared with the transcrural and transaortic blocks, the needle tips lie posterior and cephalad to the diaphragm, which increases the risk of chylothorax and pneumothorax.

Complications

The incidence of major complications with neurolytic celiac plexus blocks is 0.15 to 1.0%.32,33 These complications typically occur from transgression of structures during needle placement or unintentional spread of neurolytic or local anesthetic solutions. Inadvertent injury to structures can result in pneumothorax, chylothorax (secondary to thoracic duct injury), genitourinary injury, somatic nerve injury, and retroperitoneal hematoma; complications secondary to inadvertent spread of agent include sexual dysfunction, groin neuralgia, paraplegia, retroperitoneal fibrosis following repeated neurolytic blocks,34 and pleural effusion.35 Complications are often self-limited. In a study of 136 cases following celiac plexus block, Brown et al describes two cases of pneumothorax, neither requiring thoracostomy as therapy.21 Renal perforation can occur, albeit typically without sequelae, especially if the block needles are placed more than 7.5 cm from midline. When inserted lateral to this point, renal impalement can occur in 10% of cases.36 Paraplegia has been described secondary to injury to the artery of Adamkiewicz during block placement37 and from arterial vasospasm causing anterior spinal artery syndrome.38 Paraplegia can also occur from incorrect needle placement and subsequent injection in the subarachnoid or epidural space, or from intrapsoas muscle injection with blockade or neurolysis of the lumbar plexus. Radiographic imaging (biplanar fluoroscopy or CT) can minimize these risks.

Minor sequelae inherent to the celiac plexus block are relatively common. The most common side effects of the block include local pain (96%), hypotension (38%), and diarrhea (44%).32 Systolic blood pressure decreases of 30 to 40 mm Hg are not uncommon and are usually seen when the patient assumes an upright or sitting position following celiac plexus block. The hypotension is caused by blood pooling in the splanchnic vessels following sympathectomy; this can be minimized by an intravenous fluid bolus at the time of block placement. Compensatory reflexes usually appear by 48 hours. Diarrhea is thought to be caused by unopposed parasympathetic activity: impairment of α-adrenergic stimulation to enterocytes that increase intestinal secretory activity as well as decrease absorptive processes may also play a role. Intractable diarrhea may respond to clonidine patches or to octreotide 0.1 mg subcutaneously twice a day.39,40 The increase in gastrointestinal activity can be used in a therapeutic manner. Weinstabl et al used bupivacaine celiac plexus blocks to reduce the intestinal dysfunction (as measured by decreased gastric volumes) in several patients in a neurosurgical intensive care unit.41 Nausea and vomiting can occur from the hypotension caused by the block, or from alcohol intoxication when excessive amounts of neurolytic alcohol are absorbed at the block site. Chest pain can also occur after celiac alcohol block. It usually resolves within an hour.42

Anatomy

The superior hypogastric plexus is a retroperitoneal structure located bilaterally between the level of the lower third of the fifth lumbar vertebral body and the upper third of the sacral promontory; it is inferior to the bifurcation of the abdominal aorta and in proximity to the bifurcation of the common iliac vessels. The superior hypogastric plexus along with the left and right inferior hypogastric plexus and the pelvic plexus comprise the hypogastric plexus; this network provides innervation to the pelvic viscera. The superior hypogastric plexus receives post-ganglionic sympathetic contributions from the inferior mesenteric ganglion and from the hypogastric nerves (lumbar splanchnics) that course along with the abdominal aorta.43 Parasympathetic innervation arises from the second, third, and fourth sacral segments, and contribute to the plexus via the pelvic nerve. Finally, visceral afferents from the pelvic organs course through the hypogastric plexus and enter the spinal cord via the L1 or L2 spinal nerve roots or via the sacral segments S2, S3, or S4. Pelvic organs innervated by the hypogastric plexus include the rectum, bladder, perineum, prostate, and uterus. Pain associated with these ganglia will often cause patients to complain of pain in the lower abdominal wall around the pubic region.

Indications

Pelvic pain secondary to neoplasm can be successfully managed by superior hypogastric plexus blocks. Lee et al reported that surgical interruption of the hypogastric plexus (presacral neurectomy) can provide pain relief in various malignant and nonmalignant painful conditions.44,45 Plancarte et al then devised a reliable means to percutaneously block nerves in this region.46 They showed that in patients with advanced pelvic neoplasms (to include cervical, prostate, and testicular cancers) pain scores are reduced up to 90% using superior hypogastic plexus blocks and non-opioid analgesics. As with other block techniques, the superior hypogastric plexus block is performed using local anesthetic to determine efficacy, then repeated as needed using a neurolytic agent.

Superior hypogastric plexus blocks can provide pain relief in nonmalignant conditions refractory to conservative therapy. We have had considerable success using non-neurolytic superior hypogastric plexus blocks to control ilioinguinal, testicular, and scrotal pain following inguinal herniorhaphies and vasectomies. Other benign pain states that may respond to superior hypogastric plexus blocks include endometriosis, pelvic inflammatory disease, and proctalgia.

Technique

The patient is placed in the prone position with a pillow beneath the lower abdomen and hip to reduce the lumbosacral lordosis. This region is then prepared and draped in sterile fashion, and fluoroscopy is used to identify the L4-5 interspace. Skin wheals are then raised bilaterally 5 to 7 cm from the midline of the back at this level, and a 15- to 20-cm, 22-gauge subarachnoid needle is inserted through one of these skin wheals.

From a position perpendicular in all planes to the skin, the needle is oriented approximately 30 degrees caudad and 45 degrees mesiad so that the tip is directed toward the anterolateral aspect of the L5 vertebral body. The needle trajectory is in a significantly more caudal direction compared to the celiac plexus or lumbar sympathetic block (Fig. 69-7). Potential obstacles to successful needle placement include the iliac crest, the L5 transverse process, or the L5 vertebral body. Needle contact with the ilium is avoided by a more medial or superior entry site. If the L5 transverse process is encountered, redirect the needle in a more caudal direction. If the needle then contacts the L5-S1 facet, reenter the needle through a skin wheal that is 1 to 2 cm superior to the previous entry site. Once the L5 vertebral body is contacted, the needle is redirected in a less mesiad plane in an attempt to “walk off” the vertebral body. Advancing the tip 1 cm past the vertebral body may result in a loss or resistance or “pop,” suggesting that the needle tip has traversed the anterior fascia of the psoas muscle (Fig. 69-8). The will typically occur at a depth of 8 to12 cm. A second block needle is inserted on the opposite side to the first, and the angles of entry and the depth of the first needle are then used as a guide. Needle tip place is confirmed by using 3 to 5 mL of water-soluble contrast dye and fluoroscopy. On lateral view, the dye is seen to spread in a smooth contour anterior to the L5 vertebral body and sacral promontory; on AP view, the contrast medium should be confined to midline. Eight to ten milliliters of 0.25% bupivacaine or 1% lidocaine is injected through each needle. Six to eight milliliters of aqueous 10% phenol should be injected through each needle if neurolysis is desired.

Variations to the above technique include a single-needle approach, a transdiscal approach, and a transarterial approach. A single-needle approach follows the same technique as thatdescribed earlier; however, only one needle is placed and a larger volume (20 to 30 mL) of local anesthetic is used. A transdiscal approach is another single-needle approach. Occasionally, the needle trajectory results in needle passage through part of the L5-S1 disk; when this occurs, the final position of the needle tip is very close to the anterior border of the disk. Confirmation of needle placement with contrast agent is performed. A discogram is seen if the needle tip remains in the intervertebral disk. When the appropriate contrast pattern is achieved, a smaller volume of local anesthetic or neurolytic solution (10 to 15 mL) is then used. The transarterial approach is employed when arterial blood is aspirated from the block needle. Aspirated blood suggests that the needle has inadvertently entered the iliac artery. The needle is then advanced until blood can no longer be aspirated. Because the iliac arteries are retroperitoneal and are in the same tissue plane as the superior hypogastic plexus, a loss of resistance technique (similar to the transaortic celiac plexus block) can then be used to confirm that the needle tip has traversed the anterior wall of the artery. Contrast dye followed by local anesthetic or neurolytic agent is then injected.

Complications

Complications are rarely serious and include hematoma from puncture of the iliac vessels, back pain and spasm from needle trauma, and intramuscular or intraperitoneal injection of local anesthetic or neurolytic solution. Other complications include inadvertent somatic block from subarachnoid or epidural injection, somatic nerve injury, and ureteral or renal puncture. According to Racz, if neurolytics are used, phenol at concentrations <6% should be used to minimize ureteral injury. He also notes that his experience in men is limited to unilateral blocks, and recommends that bilateral neurolytic blocks in men should not be performed because of the possibility of sexual dysfunction.47 Proper technique with the use of fluoroscopy should negate these risks.

Anatomy

The lumbar sympathetic chain is easily blocked with few complications compared to other levels of the sympathetic chain. This is primarily because of the consistent position of the chain next to the lumbar vertebrae as well as its relative separation from somatic nerves. Once the sympathetic trunk extends into the abdomen, it assumes a prevertebral position as compared with the paravertebral position occupied in the thorax. On the right side, it lies posterior to the inferior vena cava, and on the left side, it lies lateral and slightly behind the abdominal aorta. The lumbar sympathetic chain consists of several ganglia (average three per side) between the L1 and L5 vertebral bodies.48 The ganglia are most frequently found at the level of the lower third of the second lumbar vertebra to the middle third of the third vertebrae on both the right and left sides.48,49 Most importantly, the psoas muscle always lays posterior to the sympathetic chain, thus separating the chain from the lumbar somatic roots. This separation of the sympathetic chain from the somatic lumbar plexus minimizes the spread of local anesthetic or neurolytic agent to these nerves during percutaneous lumbar sympathetic blocks. As a result, the untoward side effects are minimal and infrequent, making this procedure the prime means for lumbar sympathetic neurolysis.

Indications

The common indications for lumbar sympathetic blocks include compromised circulatory insufficiency, claudication, renal colic, herpes zoster, postherpetic neuralgia, phantom limb pain, amputation or stump pain, and carcinomatous invasion of nerves and plexus. A more complete list can be found in the Table 69-3. These blocks are also used to diagnose and treat complex regional pain syndrome (CRPS) of the lower extremity. They can help determine if the CRPS is responsive to sympathectomy, that is, determine whether the CRPS is sympathetically maintained or sympathetically independent. While lumbar sympathetic blocks can be used to treat pelvic and urogenital pain, bilateral blocks are often necessary to achieve satisfactory results; in these cases, superior hypogastic plexus blocks (see earlier description) are more appropriate because they do not cause temperature changes in the lower extremity as do the lumbar sympathetic blocks.

Once responsiveness to sympathetic blocks is recognized, aggressive therapy should be instituted as soon as possible. A reasonable approach to treatment involves the daily or every other day application of sympathetic blocks for 1 to 2 weeks. An alternative to administering daily injections involves the use of commercially prepared continuous infusion lumbar sympathetic block catheters. Another option is to institute continuous lumbar epidural analgesia. Initial infusion rates of approximately 6 mL/hour of 0.125% bupivacaine should suffice. Means to achieve prolonged sympathetic blockade include the use of neurolytic agents50 and radiofrequency lesioning.51 It is important to ensure that sympathectomy therapy of the lower (and upper) extremity is complemented by aggressive physical therapy to optimize treatment success.

Technique

The classic lumbar sympathetic block is performed by placing a needle at the anterolateral border of the L2, L3, and L4 vertebral bodies. Patient positioning is similar to that used in the posterolateral approach to the celiac plexus block. The patient is placed prone with a pillow beneath the lower abdomen and hip to reduce the lordosis of this region and improve identification of the L2 through L4 spinous processes. The L2 spinous process is found by identifying the tips of the 12th ribs and drawing a line between them; the midpoint typically corresponds to the L2-3 interspace. Similarly, identification of the L4-5 interspace involves locating the superior edge of the iliac crests and drawing a line between them; the midpoint of this line marks this interspace. Radiographic facilities are not required to successfully perform this block. However, fluoroscopy or CT can be used when landmarks are difficult to identify (such as in morbidly obese patients); these imaging devices can help to ensure the appropriate location of the needle tip.

A local anesthetic skin wheal is raised approximately 6 to 10 cm lateral to the spine of the second lumbar vertebrae. Needle entry can be performed medial 6 cm, but makes final placement of the needle tip at the anterolateral surface of the vertebral body more difficult. Reid et al52 noted that needle penetration at 7 cm from midline provides easy identification of the vertebral body, yet avoids puncture of the kidney. An advantage to a more lateral approach is that the needle avoids passing through the erector spinae muscles and avoids inflicting pain and spasm in these muscles.

Ten centimeter, 22-gauge subarachnoid needles are inserted at a 45 to 60 degree angle toward midline. The transverse process may be contacted; this typically occurs at about 5 cm. The needle is then marked at 3 to 5 cm from the skin, and then repositioned inferiorly and medially to contact the vertebral body. This typically occurs at about 6 to 8 cm and is then walked off the vertebral body until it is advanced to the depth identified by the needle marker. If using fluoroscopy or CT, it is not necessary to identify the transverse process; the needle tip is advanced directly toward the anterolateral aspect of the vertebral body. As long as the needle is in the psoas muscle, there will be some resistance to injection. Using a loss of resistance technique or fluoroscopy with contrast to observe psoas tenting,53 one can determine when the needle has advanced through the anterior surface of the psoas muscle.

Once the needle tip is positioned along the anterolateral aspect of the selected vertebral body, the needle is aspirated for cerebrospinal fluid (CSF) or blood. Contrast agent (1 to 3 mL) is then injected and a characteristic longitudinal spread of contrast dye can be seen (Fig. 69-9). Injected contrast will appear striated and spread in a diagonal pattern if the needle tip is in the psoas muscle; a “psoas stripe” can be seen (see Fig. 69-9A). This is easily corrected by advancing the needle tip an additional 0.5 to 1.0 cm; injection of contrast is then repeated. The appropriate spread is in a cranio-caudal direction and appears rather thin when seen in a lateral view with fluoroscopy (see Fig. 69-9B). A 2-mL test dose of 1% lidocaine or 0.25% bupivacaine is injected and the patient is evaluated for untoward side effects. About 5 mL of local anesthetic is then injected through the needle; the procedure is then repeated at the other two (L3 and L4) lumbar sites.

Alternatively, a single-injection technique can be performed using the same approach except that once the appropriate depth is obtained, a larger volume (10 to 20 mL) of local anesthetic is injected.54 As the ganglia are most often found at the lower portion of the second lumbar vertebral body to the middle of the third vertebral body, this area becomes the most favorable when using a single-needle technique.48,49 The advantage of a single-needle technique is decreased post-procedure pain and muscle spasm as a result of less needle trauma through the paraspinal and psoas muscles.

Complications

Serious complications are rare and are minimized with the use of radiographic imaging. The most common sequelae is backache, typically related to needle trauma, that usually responds to conservative therapy such as short-term oral opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), or ice and heat therapy. Somatic nerve block can occur from inadvertent injection of local anesthetic into the psoas muscle (psoas compartment block); it can also occur following posterior spread of local anesthetic along tendinous arches that bridge the concave sides of the lumbar vertebrae, thus blocking somatic nerves roots.55 Hematuria occasionally occurs from needle puncture of the kidney or uterer. Although this finding usually resolves spontaneously after 2 to 3 days, the hematuria can be very distressing to the patient. Kidney puncture is avoided by limiting injections to below the L2 vertebral body.56 Performing the block in the lateral position may also minimize the chance of puncture by theoretically allowing the kidney to fall anteriorly and out of the path of the block needle.

Genitofemoral neuralgia occurs with an incidence of approximately 20% following fluoroscopically guided neurolytic lumbar sympathetic block.50 This incidence is decreased by using smaller volumes of neurolytic agent (thus minimizing the spread of agent to the genitofemoral nerve) and injecting cranial to the L4 vertebral body.57 The symptoms consist of a burning dysethesia in the anteromedial area of the upper thigh; the pain is frequently severe and can last 6 to 8 weeks, but is usually controlled with transcutaneous electrical nerve stimulation (TENS) or antiepileptic medications, such as diphenylhydantoin or carbamazepine.58

Because incidental genitofemoral nerve block is common, it is important to consider whether the pain syndrome in question unsuspectingly involves the genitofemoral nerve or the L1 nerve root. A “diagnostic” lumbar sympathetic block that unintentionally blocks the genitofemoral nerve may yield the false diagnosis that the pain syndrome was sympathetically maintained. Such a situation may exist when a somatic pain syndrome exists in the genitofemoral or anterior thigh area and the following sequence occurs: a lumbar sympathetic block is performed to diagnose sympathetically maintained pain, an unintentional genitofemoral nerve block occurs that then alleviates the somatic pain, and the syndrome is incorrectly identified as involving sympathetic elements. Performing a sympathetic block at L2 may avoid this scenario by preferentially sparing the genitofemoral nerve.57

Other complications occur from inadvertent needle placement. Needle entry into the dural cuff of a somatic nerve can result in an epidural or subarachnoid block.59 A case report of retroperitoneal hemorrhage has also been described with paravertebral blocks.60

Certain conditions preclude the pain specialist from using regional sympathetic blocks. These include coagulopathy, systemic infection, and postsurgical changes in the region of interest (such as radical neck surgery or aortic graft placement). Alternatives to regional sympathetic blocks include peripheral nerve or plexus blocks and epidural administration of local anesthetic. Options to nerve blocks include regional or systemic intravenous techniques, oral therapy, and surgical sympathectomy.

Once it has been determined that the pain syndrome is sympathetically maintained, continuous catheter techniques can be effective. Brachial plexus catheters placed in the axillae or infraclavicular region can provide continuous low-dose analgesia (e.g., bupivacaine 0.125% at 10 mL/hour) for several days. Cervical, thoracic, or lumbar epidural catheters at similar or lower infusion rates and concentrations can provide reasonable analgesia as well, although ambulation and activities of daily living may become significantly impaired. These techniques are more familiar to the practicing anesthesiologist than continuous stellate ganglion and lumbar sympathetic catheters, and are less likely to become dislodged after several days of physical therapy.

Intravenous regional sympathetic blocks have been performed using guanethidine, bretylium, and reserpine. Guanethidine inhibits the presynaptic release of norepinephrine by displacing it from storage sites in the peripheral nerve endings and preventing its reuptake. The resultant depletion of norepinephine results in a pharmacologic sympathetic block. Bretylium produces sympathectomy by being taken up in adrenergic terminals; then it acts as a false transmitter and releases much less norepinephrine than guanethidine. Reserpine acts on the peripheral nervous system by depleting norepinephrine stores and inhibiting norepinephine synthesis. The most widely studied agent has been guanethidine; it is no longer available in the United States. Twenty milliliters of guanethidine in 0.5% lidocaine (25 mL for the upper extremity, 50 mL for the lower extremity) is injected intravenously following tourniquet inflation; the tourniquet is kept inflated for 20 to 30 minutes to prevent the release of guanethidine into the systemic circulation. Lidocaine is added for patient comfort because the initial norepinephine release can be painful for the patient with CRPS; however, this practice may actually be unnecessary.61 The procedure is repeated every 2 to 4 days for a maximum of four blocks. Reserpine 1.0 to 1.5 mg62 and bretylium 1.5mg/kg63 have been also used in volumes of 0.5% lidocaine as previously noted. Because the sympathectomy produced is shorter lived than with guanethidine, the regional blocks should be performed on a daily basis when these agents are used. Complications of intravenous regional sympathectomy include transient syncopal episodes with apnea,64 orthostatic hypotension, pain with administration, nausea, and vomiting.

Varying success rates have been reported with these agents, and as a result, the use of intravenous regional sympathectomy is somewhat controversial.61–63,65–70 In 1983, Bonnelli et al reported that in patients with reflex sympathetic dystrophy, intravenous regional guanethidine blocks provided comparable pain relief with longer duration to stellate ganglion block therapy.68 In a 10-year follow-up study of neuralgia in the hand, Wahren noted that guanethidine therapy can provide 2 weeks to 6 months of prolonged pain relief.69 Hord also showed in a double-blind randomized trial that intravenous regional bretylium also provided effective analgesia of reflex sympathetic dystrophy; however, a review of his data reveal that only a 30% improvement of pain relief was considered significant.63 In contrast, randomized, double-blind studies evaluating the use of guanethidine61,70 and reserpine61 did not show any improvement in pain scores compared with intravenous regional therapy with placebo. A mechanism of tourniquet-induced analgesia may play a role.61

Phentolamine infusion has gained some popularity as an alternative to diagnosing sympathetically maintained CRPS.71,72 Incremental dosing of intravenous phentolamine to supine patients under a monitored setting can be safely performed73; the total dose given over 30 to 60 minutes is 0.5 to 1.0 mg/kg. Intravenous phentolamine can help determine a responsiveness to the oral α-adrenergic blocking agents such as phenoxybenzamine. Pain relief of at least 50% or untoward effects such as hypotension, dizziness, or headache are the usual endpoints to this diagnostic test. Complications are rare, typically self-limited, and include sinus tachycardia, premature ventricular beats, or wheezing.

Neurolytic agents are used to provide long-term pain relief (See also Chapter 63). Prior to injecting a neurolytic agent, a local anesthetic test block is useful to test the feasibility of a “permanent” test block. A successful test block does not always predict the outcome of a neurolytic celiac plexus block, however.

Alcohol and phenol are the two neurolytic agents most commonly used. Alcohol is used in concentrations from 50% to 100%. The mechanism of neurolysis is via extraction of cholesterol and phospholipid from neural membranes. There is also precipitation of lipoproteins and mucoproteins. Alcohol probably provides more intense nerve destruction than phenol. Alcohol diffuses more rapidly through biological tissue, thereby increasing the degree of somatic nerve damage. Of note, while no controlled studies comparing the two agents exist, there may be an increased incidence of L1 neuralgia during lumbar sympathetic block when alcohol is used versus phenol.50 Sedation, dysphoria, and nausea and vomiting can occur from excessive systemic absorption of injected alcohol. A plasma alcohol level can be measured, but levels are highly variable and depend on concentration, volume, and metabolic rate of the patient. Phenol is usually used in concentrations of 6% to 10%. Phenol causes protein coagulation and necrosis of nerves. The higher concentrations of phenol must be made soluble in a glycerin base; as a result, the heavier viscosity makes it difficult to inject. The primary advantage of phenol is its inherent local anesthetic effect, which precludes pain on injection; in contrast, alcohol typically causes a severe, transient pain on injection. Phenol has a slower onset of action, is less efficacious, and is of shorter duration than alcohol.