Curr Pain Headache Rep (2014) 18:394 DOI 10.1007/s11916-013-0394-z
ANESTHETIC TECHNIQUES IN PAIN MANAGEMENT (D WANG, SECTION EDITOR)
Celiac Plexus Block in the Management of Chronic Abdominal Pain Maunak V. Rana & Kenneth D. Candido & Omar Raja & Nebojsa Nick Knezevic
Published online: 11 January 2014 # Springer Science+Business Media New York 2014
Abstract Chronic abdominal pain is a devastating problem for patients and providers, due to the difficulty of effectively treating the entity. Both benign and malignant conditions can lead to chronic abdominal pain. Precision in diagnosis is required before effective treatment can be instituted. Celiac Plexus Block is an interventional technique utilized for diagnostic and therapeutic purposes in the treatment of abdominovisceral pain. The richly innervated plexus provides sensory input about pathologic processes in the liver, pancreas, spleen, omentum, alimentary tract to the mid-transverse colon, adrenal glands, and kidney. Chronic pancreatitis and chronic pain from pancreatic cancer have been treated with celiac plexus block to theoretically decrease the side effects of opioid medications and to enhance analgesia from medications. Historically, the block was performed by palpation and identification of bony and soft tissue anatomy; currently, various imaging modalities are at the disposal of the interventionalist for the treatment of pain. Fluoroscopy, computed tomography (CT) guidance and endoscopic ultrasound assistance may be utilized to aid the practitioner in performing the blockade of the celiac plexus. The choice of radiographic technology depends on the specialty of the interventionalist, with gastroenterologists favoring endoscopic ultrasound and interventional pain physicians and radiologists preferring CT guidance. A review is presented describing the indications, This article is part of the Topical Collection on Anesthetic Techniques in Pain Management M. V. Rana (*) : K. D. Candido : O. Raja : N. N. Knezevic Department of Anesthesiology, Advocate Illinois Masonic Medical Center, 836 W. Wellington Ave. Suite 4815, Chicago, IL 60657, USA e-mail: [email protected] M. V. Rana : K. D. Candido : N. N. Knezevic Department of Anesthesiology, University of Illinois, Chicago, IL 60612, USA
technical aspects, and agents utilized to block the celiac plexus in patients suffering from chronic abdominal pain. Keywords Chronic abdominal pain . Celiac plexus block . Chronic pancreatitis
Introduction Chronic Abdominal pain (CAP) is a significant health problem in society today. It is readily prevalent in up to 75 % of adolescents and 50 % of adults [1, 2]. CAP is the most common reason for outpatient clinic visits [3]. The entity is difficult to treat partly because of the lack of precision in diagnosis. Chronic abdominal pain can arise from both cancer and non-cancerous causes, and medical management alone may not enough to adequately treat it. In fact, because of the prevalence and the effect on health care of CAP, the International Association for the Study of Pain (IASP) has noted 2012–2013 to be the year of “chronic visceral pain”[4•]. Treatment options run the gamut from pharmacologic, interventional, and biopsychosocial treatments. Opioid therapy is typically utilized for the treatment of CAP states. These agents are not innocuous and may have side effects such as sedation, respiratory depression, altered gut motility, sphincter of Oddi spasm, constipation, etc. The difficulty in adequately treating CAP is due to the rich neural innervation of abdominal viscera. Regional nerve blockade is an effective treatment modality with regards to chronic pain control that may decrease the drug related side effects. Celiac plexus blocks (CPB) have successfully been used to treat a variety of these painful processes of the abdomen. Previous discussion [5] has centered on the use of CPB for the treatment of pancreatic cancer pain. In this article, we will expand upon the review on the utility of CPB, highlighting utility against CAP by noting indications and technical
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considerations related to provider choice of imaging modality in performing the procedure, as well as agents utilized in the blockade of pain-carrying fibers. Celiac Plexus Block is a procedure that allows for the diagnosis and treatment of pain secondary to these diverse intra-abdominal conditions, including both benign and malignant causes. The main identified targets of the block are afferent nociceptive fibers. These fibers transmit painful impulses associated with pathology of the pancreas, liver, gallbladder, omentum, mesentery and the alimentary tract from the stomach to the mid-transverse large colon. During the interventional treatment of patients with CAP, separating non-visceral causes from viscerally mediated pain may be performed with positive somatic blocks, such as intercostal nerve blocks (ICNB), prior to performing a CPB. This may help determine somatic versus visceral origin of the pathological process.
Anatomy The retroperitoneally located celiac plexus is actually composed of multiple smaller ganglia: the gastric, hepatic, celiac, splenic, pancreatic and suprarenal plexuses. The celiac plexus sends nerve fibers to other plexuses, including the renal, gonadal (ovarian/testicular), superior and mesenteric plexuses. This plexus complex is located anterolateral to the aorta, epigastrium, and crus of the diaphragm. The paired-celiac ganglion makes up the plexus and is located between 0.6 and 0.9 cm caudal to the celiac artery [6•]. The most common locations of the plexus, as reported in an CT evaluation of 200 consecutive patients, is T11/12 6.5 %; T12 34 %; T12/L1 31 %; L1 28.5 % [7••]. The celiac plexus innervates the abdominal viscera with fibers arising from preganglionic splanchnic nerves, preganglionic parasympathetic vagus nerve fibers, sensory nerve contribution from the phrenic and vagus nerves, and postganglionic sympathetic fibers. Sympathetic innervation is derived from the anterolateral horn of the spinal cord as axons from T5 to T12 leave the spinal cord with ventral nerve roots to join white rami communicans (WRC) en route to the sympathetic chain. These axons do not synapse in the sympathetic chain, but pass through to synapse at distal sites. Postganglionic nerves accompany blood vessels to visceral structures. Preganglionic fibers from T5 to T9 travel caudally from the sympathetic chain along the lateral and anterolateral aspects of the respective vertebral bodies. The greater splanchnic nerve arises from the T9 and T10 levels. Complete sympathetic denervation of the gastrointestinal tract, as may occur following CPB, renders an individual likely to develop increased peristalsis due to unopposed parasympathetic nervous system activity.
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Indications The main indication for CPB include non-somatic visceral abdominal pain refractory to analgesic interventions, which emanates from the pancreas, liver, gallbladder, stomach, spleen, omentum, mesentery, small intestine, mid-transverse colon, spleen, kidneys, and the adrenal glands. Implicit in the description of pain, indications also include pathology that has either a cancer or non-cancer etiology [8, 9]. Regarding noncancer type pain, among the leading causes is chronic pancreatitis, and it has been shown that these patients benefit from celiac plexus blocks [10•]. The majority of patients who receive CPB for the treatment of chronic pain suffer from disease of the pancreas. This may be due to chronic pancreatitis (CP) or recurrent pain from pancreatic cancer [11, 12, 13•]. The etiology of abdominal pain in chronic pancreatitis is difficult to pinpoint, as multiple causes may be leading to this dolorous state. Regardless of etiologic origin, the endpoints of intrapancreatic pressure increase, ischemic insult to the pancreas, the development of fibrotic derangement, the presence of pseudocysts, along with neurogenic inflammation, are nonmalignant causes leading to significant pain. Cancer-related causes such as the above mentioned destruction to the pancreas, and perineural invasion by pancreatic cancer cells along with enzymatic destruction of the pancreas, can lead to chronic pain as well [14]. Splanchnic nerve irritation, whether due to inflammation or direct tissue involvement, leads to discomfort in these patients. Peripheral sensitization occurs, likely leading to central sensitization and chronic pain. Direct access to the sympathetic nerves innervating the pancreas and traveling through the celiac plexus is the interventional target for the management of CP and cancer-related pain. Many classification systems exist for classifying patients with CP [15••]. Patients have been stratified by ductal involvement, etiology of disease, and response to treatment for purposes of improving therapy. In one particular classification system, Type-A patients describe short-lasting mild to severe pain episodes, separated by longer pain-free episodes. Patients with this presentation are seen with acute relapsing pancreatitis. Type-B patients experience unremitting and severe pain, often resulting in hospitalization for treatment. Patients demonstrating this presentation are noted to have ductal hypertension, cholestasis, or pseudocysts. CPB have been shown in one study to be beneficial to patients with abdominal pain due to diabetic gastroparesis [16]. Cancer-related pain is usually treated with neurolytic celiac plexus blocks. An early meta-analysis found that pain relief was “good or excellent” in 89 % of 989 patients for the first 2 weeks following the block. Regarding chronic pain due to pancreatic cancer, when neurolytic CPB is performed for pancreatic cancer, it appears that cancers of the head of the pancreas respond more favorably than those associated with
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lesions elsewhere in the pancreas. [17]. Not only is neurolytic CPB favorable as an analgesic adjuvant in pancreatic cancer pain, it may also elevate patient’s mood; reduce pain interference with activity; and possibly increase life expectancy by some unknown mechanism [18].
Block Techniques Historically, CPB was performed with morphologic measurements to access the location of the celiac plexus anterior to the thoracic vertebral body [19]. Customarily, needle entry is 7– 8 cm from the anatomical midline at the inferior border of the twelfth rib, directed in a medial fashion. Given the variability in the location of the celiac plexus [7••], and the potential risk of visceral injury and pneumothorax, visualization with radiographic assistance, CPB with fluoroscopic techniques, computed tomography (CT)-guided approach, ultrasound approach, and endoscopic ultrasound guided approach (EUSCPB) are used. Informed written consent should be obtained, and one should be sure that the patient has no contrast allergies and is not using any anticoagulant medications. Standard American Society of Anesthesiologists (ASA) monitors should be applied, and baseline vital signs assessed and documented. A peripheral intravenous catheter should be placed in order to administer fluids and supportive drugs in case of an inadvertent event, or following the expected orthostatic hypotension that can occur after a successful block. Three basic anatomical techniques to approach the celiac plexus are the posterior para-aortic approach, posterior transaortic approach and the anterior approach.
Posterior Para-Aortic Approach The patient is placed in the prone position with a pillow under the abdomen to reduce the normal lumbar lordotic curve. After sterile prep and drape, a 20-gauge or 22-gauge, 12–18cm spinal type needle is advanced from posterior to anterior towards the ventral surface of the T12-L1 intervertebral space under fluoroscopic guidance. A single needle is typically placed via a left-sided approach to reliably block the celiac plexus [7••], or alternatively, bilateral needles may be placed if there is not a satisfactory spread of contrast using the unilateral approach. The optimal angle for needle insertion varies using a left-sided approach, but has been calculated to be between 18° (at T12) and 19° (at L1) [20•]. In the viewpoint of the present authors, who have performed more than five hundred CPBs, rarely does the bilateral approach need to be performed to successfully attain bilateral contrast spread using the described technique(s). Needle advancement is performed in close proximity to the lateral aspect
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of the vertebral bodies during the entire course of needle penetration towards the target. Fluoroscopically guided CPB does not allow for visualization of visceral structures, so care should be taken to place the needle 6–8 cm from the midline. With CT-guided techniques, of course, many of these same concerns are rendered moot, as the anatomy is more easily reconciled. Penetration or non-penetration of the crus of the ipsilateral diaphragm while performing a posterior approach to CPB determines whether the block is a “true” CPB, or whether in fact it is a splanchnic nerve block (SNB), respectively [21]. Upon bony contact with the vertebral body, the needle is angled laterally off the surface of the bone. An alternate approach that may lead to less patient discomfort involves avoiding bony contact altogether via oblique/caudal-cranial angulation of the fluoroscopy unit [22]. Regardless of the radiographic modality utilized for needle placement, contrast injection is performed after satisfactory needle placement. Utilization of ultrasound for the CPB requires the additional step of identifying vascular structures leading to the location of the celiac plexus, due to inability to reliably visualize the structure using low frequency, curvilinear probes, given the depth and penetration for such a block. The volume of agent injected [6•, 23, 24] should be sufficient to identify spread along the aortic column via fluoroscopy, and via CT, a bilateral para-aortic spread of contrast media.
Anterior Para-Aortic Approach An anterior approach is utilized for patients not able to lie in the prone position. A technical advantage to using the anterior CPB approach is the ability to advance a single needle from anterior to posterior towards the abdominal aorta, allowing for proximate placement of agent around the plexus. However, a significant concern with this approach is the risk of visceral injury and possible bacterial translocation, due to the requirement for needle insertion through abdominal organs. With the anterior approach, CT imaging is a preferred approach, as it allows for visualization of targeted and visceral structures directly in the pathway of the advancing needle. After the usual sterile preparation of the patient, the T12 vertebral body is identified as the target needle entry point, and a local anesthetic skin wheal is placed anterior to the T12 vertebral body as seen on imaging. A 20-gauge or 22-gauge block needle is inserted and directed towards the abdominal aorta. Contrast use as described above is then undertaken with CT imaging or fluoroscopy guidance. As opposed to the previously described technique, a bilateral approach may be superior to the single-needle anterior CPB. More effective dye spread is seen with the bilateral approach, possibly leading to more analgesia with this approach [25].
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Posterior Trans-Aortic Approach Abdominal aortic encroachment may occur during the performance of the CPB. Bright red blood will be seen at the hub of the needle during withdrawal of the inner stylet. Upon penetration of the great vessel, needle advancement is performed until hub blood flow ceases. The above technique for the posterior para-aortic CPB is continued with injection of contrast media.
Endoscopic Techniques Endoscopic ultrasound equipment (EUS) has been advocated for CPB—(EUS-CPB). This modality seeks to avoid radiation exposure to the patient and clinician. From a technical standpoint, EUS-CPB is purported to reduce complications, such as pneumothorax and paraplegia from the posterior approaches. The gastroenterological literature suggests that EUS should be considered first-line therapy in patients suffering from pancreatic cancer who require CPB [26]. A linear array ultrasound endoscope and a prototype needle-catheter to inject the plexus are placed via transgastric approach. Bilateral injection of the ganglia was not shown to be superior to single injection using bupivacaine and 98 % dehydrated absolute alcohol in 30 patients [27]. Eightyeight percent of patients had persistent improvement in pain scores and used less opioid analgesics at the 12-week followup evaluation [28]. A prospective study [29] of the technique was performed in 58 patients evaluated over a six-month follow-up period. The authors injected 3 to 6 mL of 0.25 % preservative-free bupivacaine, followed by 10 mL of dehydrated 98 % absolute alcohol injectate. Seventy-eight percent of patients had a reduction in pain scores associated with a reduction in narcotic consumption. Only five episodes of abdominal pain and no major complications were identified. A meta-analysis evaluating six studies comprised of 221 patients was performed, wherein EUS was used for CPB to manage chronic abdominal pain associated with chronic pancreatitis or pancreatic cancer [13•]. In another paper evaluating multiple studies, EUSguided CPB was 59.5 % effective in managing chronic abdominal pain from pancreatitis, but was 80.12 % effective for managing the pain of pancreatic cancer based on pooled data [10•]. However, caution should be used in interpreting the success rates quoted, as pointed out in a recent editorial identifying that in studies such as the one above by Gunaratnam et al. [29], the actual reduction in pain levels was a modest 2 points or less in about half the responders, on an 11-point numeric pain rating scale (0–10) [13•]. Furthermore, the efficacy of CPN was lower if patients did not receive adjuvant therapy, and opioid use was reduced, but clearly was not eliminated [13•].
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While the technique of EUS-guided CPB continues to evolve and mature [30], there is a demand being made for controlled studies that actually compare this approach with alternative imaging techniques, as all the evidence to date has accrued from observational and uncontrolled case series [31]. The actual technique of EUS has been touted as being able to identify the actual celiac ganglia comprising the celiac plexus. Anatomically, this is described as a hypoechoic, small and either multi-lobulated or confluent series of small spheres with hypoechoic bands of tissue [32, 33]. When injection was made following EUS identification of the ganglia themselves, 50 % of 64 patients demonstrated an analgesic response to the block at a one-week evaluation follow-up [34]. Visualization of the ganglia was noted to be the single-most significant predictor of successful block in this retrospective review [34]. Patients with visible ganglia were 15 times more likely to respond favorably than those wherein the ganglia were not visible [34].
Choice of Interventional Technique The clinician treating the patient suffering from CAP is faced with a therapeutic dilemma: which of the above interventional approaches would provide the best degree of analgesia? The ideal procedure would allow for detailed visualization that would lead to precise placement of injected agent, resulting in profound and extended analgesia. Santosh et al. [35•] evaluated efficacy between a fluoroscopic-guided approach and an EUS approach to the CP. A total of 56 Patients with CP-related abdominal pain were identified and EUSG-CPB was performed in 27 and fluoroscopic CPB in 29 patients. Bilateral needle with paraaortic injectate was placed, consisting of 10 mL of Bupivacaine (0.25 %) and 40 mg of Triamcinolone in both groups. The results of the study demonstrated a statistically significant improvement in pain scores in 70 % of subjects undergoing EUS-CPB and in 30 % in the fluoroscopic group (p=0.044), leading to a suggestion of the superiority of EUSCPB versus fluoroscopic-guided CPB for pain due to CP. Assuming that the results of the above study are valid and reproducible concerning the efficacy of EUS-CPB over fluoroscopic guided procedures, a comparison of EUS and CT guided approaches should be entertained to compare these two modalities [36]. In a prospective randomized evaluation, EUS CPB was more effective than the CT-guided approach at providing analgesia in patients with pain due to chronic pancreatitis. Patients in both groups received a 0.75 % bupivacaine/40 mg triamcinolone injectate. Patients were followed from post-block day 1 and then assessed weekly for 24 weeks. Ten patients randomized to the EUS arm of the study achieved longer analgesic relief with decreased postprocedural discomfort compared to the eight patients receiving CT guided block. Patients noted that EUS-CPB was the
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preferred interventional technique. Gress et al. evaluated EUS-CPB in patients, and the results indicated that 55 % of patients responded with a reduction in pain scores, with mean pain score reduction from 8 to 2 (on a scale of 10) post-EUS CPB at both 4-week and 8-week follow-up. Twenty-six percent of patients were noted to have relief beyond 12 weeks [36]. The study also identified patients who were less likely to have benefit with this approach to the CP. Patients with prior history of pancreatic surgery and those patients younger than 45 years of age were less likely to respond to CPB via the EUS approach. The authors of this study also suggest that in addition to being more effective than CT-guided approaches, EUSCPB is more cost effective. A significant limitation to these studies is the lack of a validated pain questionnaire during the evaluation of pain responses of patients [37]. At best, EUSCPB provides relatively short-term relief of CP symptoms [38]. To rank the procedures, then, EUS-CPB would be superior among the three, followed by CT-guided approach, and finally, fluoroscopic guidance. From a practical standpoint, however, CT-guided CPB would be the preferred approach in the hands of an interventional physician performing this procedure. EUS-CPB requires specialized equipment with expertise in endoscopic ultrasound, typically limited to gastroenterologists. CT-guidance is more readily available, and direct visualization and identification of nervous and visceral structures is obtained along with tracking images of contrast dye spread. Scar tissue formation and altered anatomical relationships after pancreatic surgery possibly accounting for the decreased efficacy of the EUS-CPB in those patients would be directly visualized with assistance of CT, and may be more effective than EUS.
Block Injectate CPB for CAP typically is performed with local anesthetic. The use of steroids has been advocated along with local anesthetics in CPB [39]. The purported benefit of adding steroids is to decrease edema and inflammation due to the release of pancreatic enzymes in patients with CP. Busch et al. evaluated 16 patients with depot steroid combined with local anesthetic; four patients without narcotic dependence and prior surgery were noted to have benefit with steroid therapy during block. Based on the results of this study, a mixture of local anesthetic, typically bupivacaine along with triamcinolone, has been customarily utilized [40]. In a single center, blinded, randomized, controlled trial of 40 adult patients referred for EUSCPB for treatment of painful CP, Stevens et al. [37] showed no significant differences in primary outcomes between groups (14.3 % for patients who received triamcinolone vs. 15.8 % for controls); there were no significant differences in the change in VAS or McGill pain scores, change in narcotic requirements, or quality of life found in patients.
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Complications (Table 1) Deleterious consequences due to CPB may occur despite technical expertise and with image-guided modalities. Described risks include hypotension, diarrhea, vascular injection, spinal cord and nerve damage, retroperitoneal and visceral hematoma, abscess and discitis. Hypotension and diarrhea are among the more common effects due to the sympathectomy that occurs after a successful block. The loss of sympathetic tone of the splanchnic vessels can lead to hypotension, as well as a relative increase in parasympathetic activity of the abdominal viscera leading to diarrhea. There have also been recent case reports of anterior spinal cord infarction causing paraplegia, as well as a fatality following endoscopic ultrasound guided celiac plexus neurolysis [41, 42].
Conclusions Celiac plexus block is a valuable adjunctive therapy for managing abdominal pain associated with a visceral pathology. Pain reduction is consistently demonstrated following successful block, and there is the potential for reducing opioid consumption and opioid-related side effects and complications. Whether or not the implementation of neurolysis using this technique enhances or prolongs life expectancy in terminal cancer, however, remains to be seen. A variety of imaging Table 1 Complications of celiac plexus blocks • Hypotension • Diarrhea • Paresthesias of lumbar somatic nerves • Intravascular injection (arterial or venous) • Lumbar somatic nerve root injury • Subarachnoid or epidural injection • Renal injury • Paraplegia • Pneumothorax • Chylothorax • Vascular thrombosis or embolism • Vascular trauma • Perforation of cysts and tumors • Intradiscal injections and discitis • Injection into the psoas muscle • Abscess • Peritonitis • Retroperitoneal hematoma • Ureteral injury • Ejaculation failure • Pain both during, or after the procedure • Failure to derive an analgesic response
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techniques and approaches to the plexus are available, each of which boasts some advantage over the others. The clinician undertaking CPB should be well-versed in not only abdominal and retroperitoneal anatomy, but also in the anatomy and physiology of spinal nerves and the spinal cord, and should be prepared to deal with the many expected and occasionally unexpected sequelae following CPB. Compliance with Ethics Guidelines Conflict of Interest Dr. Maunak V. Rana, Dr. Kenneth D. Candido, Dr. Omar Raja, and Dr. Nebojsa Nick Knezevic each declare no potential conflicts of interest relevant to this article. Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by any of the authors. Disclaimers None. Financial Support None.
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ANESTHETIC TECHNIQUES IN PAIN MANAGEMENT (D WANG, SECTION EDITOR)
Celiac Plexus Block in the Management of Chronic Abdominal Pain Maunak V. Rana & Kenneth D. Candido & Omar Raja & Nebojsa Nick Knezevic
Published online: 11 January 2014 # Springer Science+Business Media New York 2014
Abstract Chronic abdominal pain is a devastating problem for patients and providers, due to the difficulty of effectively treating the entity. Both benign and malignant conditions can lead to chronic abdominal pain. Precision in diagnosis is required before effective treatment can be instituted. Celiac Plexus Block is an interventional technique utilized for diagnostic and therapeutic purposes in the treatment of abdominovisceral pain. The richly innervated plexus provides sensory input about pathologic processes in the liver, pancreas, spleen, omentum, alimentary tract to the mid-transverse colon, adrenal glands, and kidney. Chronic pancreatitis and chronic pain from pancreatic cancer have been treated with celiac plexus block to theoretically decrease the side effects of opioid medications and to enhance analgesia from medications. Historically, the block was performed by palpation and identification of bony and soft tissue anatomy; currently, various imaging modalities are at the disposal of the interventionalist for the treatment of pain. Fluoroscopy, computed tomography (CT) guidance and endoscopic ultrasound assistance may be utilized to aid the practitioner in performing the blockade of the celiac plexus. The choice of radiographic technology depends on the specialty of the interventionalist, with gastroenterologists favoring endoscopic ultrasound and interventional pain physicians and radiologists preferring CT guidance. A review is presented describing the indications, This article is part of the Topical Collection on Anesthetic Techniques in Pain Management M. V. Rana (*) : K. D. Candido : O. Raja : N. N. Knezevic Department of Anesthesiology, Advocate Illinois Masonic Medical Center, 836 W. Wellington Ave. Suite 4815, Chicago, IL 60657, USA e-mail: [email protected] M. V. Rana : K. D. Candido : N. N. Knezevic Department of Anesthesiology, University of Illinois, Chicago, IL 60612, USA
technical aspects, and agents utilized to block the celiac plexus in patients suffering from chronic abdominal pain. Keywords Chronic abdominal pain . Celiac plexus block . Chronic pancreatitis
Introduction Chronic Abdominal pain (CAP) is a significant health problem in society today. It is readily prevalent in up to 75 % of adolescents and 50 % of adults [1, 2]. CAP is the most common reason for outpatient clinic visits [3]. The entity is difficult to treat partly because of the lack of precision in diagnosis. Chronic abdominal pain can arise from both cancer and non-cancerous causes, and medical management alone may not enough to adequately treat it. In fact, because of the prevalence and the effect on health care of CAP, the International Association for the Study of Pain (IASP) has noted 2012–2013 to be the year of “chronic visceral pain”[4•]. Treatment options run the gamut from pharmacologic, interventional, and biopsychosocial treatments. Opioid therapy is typically utilized for the treatment of CAP states. These agents are not innocuous and may have side effects such as sedation, respiratory depression, altered gut motility, sphincter of Oddi spasm, constipation, etc. The difficulty in adequately treating CAP is due to the rich neural innervation of abdominal viscera. Regional nerve blockade is an effective treatment modality with regards to chronic pain control that may decrease the drug related side effects. Celiac plexus blocks (CPB) have successfully been used to treat a variety of these painful processes of the abdomen. Previous discussion [5] has centered on the use of CPB for the treatment of pancreatic cancer pain. In this article, we will expand upon the review on the utility of CPB, highlighting utility against CAP by noting indications and technical
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considerations related to provider choice of imaging modality in performing the procedure, as well as agents utilized in the blockade of pain-carrying fibers. Celiac Plexus Block is a procedure that allows for the diagnosis and treatment of pain secondary to these diverse intra-abdominal conditions, including both benign and malignant causes. The main identified targets of the block are afferent nociceptive fibers. These fibers transmit painful impulses associated with pathology of the pancreas, liver, gallbladder, omentum, mesentery and the alimentary tract from the stomach to the mid-transverse large colon. During the interventional treatment of patients with CAP, separating non-visceral causes from viscerally mediated pain may be performed with positive somatic blocks, such as intercostal nerve blocks (ICNB), prior to performing a CPB. This may help determine somatic versus visceral origin of the pathological process.
Anatomy The retroperitoneally located celiac plexus is actually composed of multiple smaller ganglia: the gastric, hepatic, celiac, splenic, pancreatic and suprarenal plexuses. The celiac plexus sends nerve fibers to other plexuses, including the renal, gonadal (ovarian/testicular), superior and mesenteric plexuses. This plexus complex is located anterolateral to the aorta, epigastrium, and crus of the diaphragm. The paired-celiac ganglion makes up the plexus and is located between 0.6 and 0.9 cm caudal to the celiac artery [6•]. The most common locations of the plexus, as reported in an CT evaluation of 200 consecutive patients, is T11/12 6.5 %; T12 34 %; T12/L1 31 %; L1 28.5 % [7••]. The celiac plexus innervates the abdominal viscera with fibers arising from preganglionic splanchnic nerves, preganglionic parasympathetic vagus nerve fibers, sensory nerve contribution from the phrenic and vagus nerves, and postganglionic sympathetic fibers. Sympathetic innervation is derived from the anterolateral horn of the spinal cord as axons from T5 to T12 leave the spinal cord with ventral nerve roots to join white rami communicans (WRC) en route to the sympathetic chain. These axons do not synapse in the sympathetic chain, but pass through to synapse at distal sites. Postganglionic nerves accompany blood vessels to visceral structures. Preganglionic fibers from T5 to T9 travel caudally from the sympathetic chain along the lateral and anterolateral aspects of the respective vertebral bodies. The greater splanchnic nerve arises from the T9 and T10 levels. Complete sympathetic denervation of the gastrointestinal tract, as may occur following CPB, renders an individual likely to develop increased peristalsis due to unopposed parasympathetic nervous system activity.
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Indications The main indication for CPB include non-somatic visceral abdominal pain refractory to analgesic interventions, which emanates from the pancreas, liver, gallbladder, stomach, spleen, omentum, mesentery, small intestine, mid-transverse colon, spleen, kidneys, and the adrenal glands. Implicit in the description of pain, indications also include pathology that has either a cancer or non-cancer etiology [8, 9]. Regarding noncancer type pain, among the leading causes is chronic pancreatitis, and it has been shown that these patients benefit from celiac plexus blocks [10•]. The majority of patients who receive CPB for the treatment of chronic pain suffer from disease of the pancreas. This may be due to chronic pancreatitis (CP) or recurrent pain from pancreatic cancer [11, 12, 13•]. The etiology of abdominal pain in chronic pancreatitis is difficult to pinpoint, as multiple causes may be leading to this dolorous state. Regardless of etiologic origin, the endpoints of intrapancreatic pressure increase, ischemic insult to the pancreas, the development of fibrotic derangement, the presence of pseudocysts, along with neurogenic inflammation, are nonmalignant causes leading to significant pain. Cancer-related causes such as the above mentioned destruction to the pancreas, and perineural invasion by pancreatic cancer cells along with enzymatic destruction of the pancreas, can lead to chronic pain as well [14]. Splanchnic nerve irritation, whether due to inflammation or direct tissue involvement, leads to discomfort in these patients. Peripheral sensitization occurs, likely leading to central sensitization and chronic pain. Direct access to the sympathetic nerves innervating the pancreas and traveling through the celiac plexus is the interventional target for the management of CP and cancer-related pain. Many classification systems exist for classifying patients with CP [15••]. Patients have been stratified by ductal involvement, etiology of disease, and response to treatment for purposes of improving therapy. In one particular classification system, Type-A patients describe short-lasting mild to severe pain episodes, separated by longer pain-free episodes. Patients with this presentation are seen with acute relapsing pancreatitis. Type-B patients experience unremitting and severe pain, often resulting in hospitalization for treatment. Patients demonstrating this presentation are noted to have ductal hypertension, cholestasis, or pseudocysts. CPB have been shown in one study to be beneficial to patients with abdominal pain due to diabetic gastroparesis [16]. Cancer-related pain is usually treated with neurolytic celiac plexus blocks. An early meta-analysis found that pain relief was “good or excellent” in 89 % of 989 patients for the first 2 weeks following the block. Regarding chronic pain due to pancreatic cancer, when neurolytic CPB is performed for pancreatic cancer, it appears that cancers of the head of the pancreas respond more favorably than those associated with
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lesions elsewhere in the pancreas. [17]. Not only is neurolytic CPB favorable as an analgesic adjuvant in pancreatic cancer pain, it may also elevate patient’s mood; reduce pain interference with activity; and possibly increase life expectancy by some unknown mechanism [18].
Block Techniques Historically, CPB was performed with morphologic measurements to access the location of the celiac plexus anterior to the thoracic vertebral body [19]. Customarily, needle entry is 7– 8 cm from the anatomical midline at the inferior border of the twelfth rib, directed in a medial fashion. Given the variability in the location of the celiac plexus [7••], and the potential risk of visceral injury and pneumothorax, visualization with radiographic assistance, CPB with fluoroscopic techniques, computed tomography (CT)-guided approach, ultrasound approach, and endoscopic ultrasound guided approach (EUSCPB) are used. Informed written consent should be obtained, and one should be sure that the patient has no contrast allergies and is not using any anticoagulant medications. Standard American Society of Anesthesiologists (ASA) monitors should be applied, and baseline vital signs assessed and documented. A peripheral intravenous catheter should be placed in order to administer fluids and supportive drugs in case of an inadvertent event, or following the expected orthostatic hypotension that can occur after a successful block. Three basic anatomical techniques to approach the celiac plexus are the posterior para-aortic approach, posterior transaortic approach and the anterior approach.
Posterior Para-Aortic Approach The patient is placed in the prone position with a pillow under the abdomen to reduce the normal lumbar lordotic curve. After sterile prep and drape, a 20-gauge or 22-gauge, 12–18cm spinal type needle is advanced from posterior to anterior towards the ventral surface of the T12-L1 intervertebral space under fluoroscopic guidance. A single needle is typically placed via a left-sided approach to reliably block the celiac plexus [7••], or alternatively, bilateral needles may be placed if there is not a satisfactory spread of contrast using the unilateral approach. The optimal angle for needle insertion varies using a left-sided approach, but has been calculated to be between 18° (at T12) and 19° (at L1) [20•]. In the viewpoint of the present authors, who have performed more than five hundred CPBs, rarely does the bilateral approach need to be performed to successfully attain bilateral contrast spread using the described technique(s). Needle advancement is performed in close proximity to the lateral aspect
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of the vertebral bodies during the entire course of needle penetration towards the target. Fluoroscopically guided CPB does not allow for visualization of visceral structures, so care should be taken to place the needle 6–8 cm from the midline. With CT-guided techniques, of course, many of these same concerns are rendered moot, as the anatomy is more easily reconciled. Penetration or non-penetration of the crus of the ipsilateral diaphragm while performing a posterior approach to CPB determines whether the block is a “true” CPB, or whether in fact it is a splanchnic nerve block (SNB), respectively [21]. Upon bony contact with the vertebral body, the needle is angled laterally off the surface of the bone. An alternate approach that may lead to less patient discomfort involves avoiding bony contact altogether via oblique/caudal-cranial angulation of the fluoroscopy unit [22]. Regardless of the radiographic modality utilized for needle placement, contrast injection is performed after satisfactory needle placement. Utilization of ultrasound for the CPB requires the additional step of identifying vascular structures leading to the location of the celiac plexus, due to inability to reliably visualize the structure using low frequency, curvilinear probes, given the depth and penetration for such a block. The volume of agent injected [6•, 23, 24] should be sufficient to identify spread along the aortic column via fluoroscopy, and via CT, a bilateral para-aortic spread of contrast media.
Anterior Para-Aortic Approach An anterior approach is utilized for patients not able to lie in the prone position. A technical advantage to using the anterior CPB approach is the ability to advance a single needle from anterior to posterior towards the abdominal aorta, allowing for proximate placement of agent around the plexus. However, a significant concern with this approach is the risk of visceral injury and possible bacterial translocation, due to the requirement for needle insertion through abdominal organs. With the anterior approach, CT imaging is a preferred approach, as it allows for visualization of targeted and visceral structures directly in the pathway of the advancing needle. After the usual sterile preparation of the patient, the T12 vertebral body is identified as the target needle entry point, and a local anesthetic skin wheal is placed anterior to the T12 vertebral body as seen on imaging. A 20-gauge or 22-gauge block needle is inserted and directed towards the abdominal aorta. Contrast use as described above is then undertaken with CT imaging or fluoroscopy guidance. As opposed to the previously described technique, a bilateral approach may be superior to the single-needle anterior CPB. More effective dye spread is seen with the bilateral approach, possibly leading to more analgesia with this approach [25].
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Posterior Trans-Aortic Approach Abdominal aortic encroachment may occur during the performance of the CPB. Bright red blood will be seen at the hub of the needle during withdrawal of the inner stylet. Upon penetration of the great vessel, needle advancement is performed until hub blood flow ceases. The above technique for the posterior para-aortic CPB is continued with injection of contrast media.
Endoscopic Techniques Endoscopic ultrasound equipment (EUS) has been advocated for CPB—(EUS-CPB). This modality seeks to avoid radiation exposure to the patient and clinician. From a technical standpoint, EUS-CPB is purported to reduce complications, such as pneumothorax and paraplegia from the posterior approaches. The gastroenterological literature suggests that EUS should be considered first-line therapy in patients suffering from pancreatic cancer who require CPB [26]. A linear array ultrasound endoscope and a prototype needle-catheter to inject the plexus are placed via transgastric approach. Bilateral injection of the ganglia was not shown to be superior to single injection using bupivacaine and 98 % dehydrated absolute alcohol in 30 patients [27]. Eightyeight percent of patients had persistent improvement in pain scores and used less opioid analgesics at the 12-week followup evaluation [28]. A prospective study [29] of the technique was performed in 58 patients evaluated over a six-month follow-up period. The authors injected 3 to 6 mL of 0.25 % preservative-free bupivacaine, followed by 10 mL of dehydrated 98 % absolute alcohol injectate. Seventy-eight percent of patients had a reduction in pain scores associated with a reduction in narcotic consumption. Only five episodes of abdominal pain and no major complications were identified. A meta-analysis evaluating six studies comprised of 221 patients was performed, wherein EUS was used for CPB to manage chronic abdominal pain associated with chronic pancreatitis or pancreatic cancer [13•]. In another paper evaluating multiple studies, EUSguided CPB was 59.5 % effective in managing chronic abdominal pain from pancreatitis, but was 80.12 % effective for managing the pain of pancreatic cancer based on pooled data [10•]. However, caution should be used in interpreting the success rates quoted, as pointed out in a recent editorial identifying that in studies such as the one above by Gunaratnam et al. [29], the actual reduction in pain levels was a modest 2 points or less in about half the responders, on an 11-point numeric pain rating scale (0–10) [13•]. Furthermore, the efficacy of CPN was lower if patients did not receive adjuvant therapy, and opioid use was reduced, but clearly was not eliminated [13•].
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While the technique of EUS-guided CPB continues to evolve and mature [30], there is a demand being made for controlled studies that actually compare this approach with alternative imaging techniques, as all the evidence to date has accrued from observational and uncontrolled case series [31]. The actual technique of EUS has been touted as being able to identify the actual celiac ganglia comprising the celiac plexus. Anatomically, this is described as a hypoechoic, small and either multi-lobulated or confluent series of small spheres with hypoechoic bands of tissue [32, 33]. When injection was made following EUS identification of the ganglia themselves, 50 % of 64 patients demonstrated an analgesic response to the block at a one-week evaluation follow-up [34]. Visualization of the ganglia was noted to be the single-most significant predictor of successful block in this retrospective review [34]. Patients with visible ganglia were 15 times more likely to respond favorably than those wherein the ganglia were not visible [34].
Choice of Interventional Technique The clinician treating the patient suffering from CAP is faced with a therapeutic dilemma: which of the above interventional approaches would provide the best degree of analgesia? The ideal procedure would allow for detailed visualization that would lead to precise placement of injected agent, resulting in profound and extended analgesia. Santosh et al. [35•] evaluated efficacy between a fluoroscopic-guided approach and an EUS approach to the CP. A total of 56 Patients with CP-related abdominal pain were identified and EUSG-CPB was performed in 27 and fluoroscopic CPB in 29 patients. Bilateral needle with paraaortic injectate was placed, consisting of 10 mL of Bupivacaine (0.25 %) and 40 mg of Triamcinolone in both groups. The results of the study demonstrated a statistically significant improvement in pain scores in 70 % of subjects undergoing EUS-CPB and in 30 % in the fluoroscopic group (p=0.044), leading to a suggestion of the superiority of EUSCPB versus fluoroscopic-guided CPB for pain due to CP. Assuming that the results of the above study are valid and reproducible concerning the efficacy of EUS-CPB over fluoroscopic guided procedures, a comparison of EUS and CT guided approaches should be entertained to compare these two modalities [36]. In a prospective randomized evaluation, EUS CPB was more effective than the CT-guided approach at providing analgesia in patients with pain due to chronic pancreatitis. Patients in both groups received a 0.75 % bupivacaine/40 mg triamcinolone injectate. Patients were followed from post-block day 1 and then assessed weekly for 24 weeks. Ten patients randomized to the EUS arm of the study achieved longer analgesic relief with decreased postprocedural discomfort compared to the eight patients receiving CT guided block. Patients noted that EUS-CPB was the
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preferred interventional technique. Gress et al. evaluated EUS-CPB in patients, and the results indicated that 55 % of patients responded with a reduction in pain scores, with mean pain score reduction from 8 to 2 (on a scale of 10) post-EUS CPB at both 4-week and 8-week follow-up. Twenty-six percent of patients were noted to have relief beyond 12 weeks [36]. The study also identified patients who were less likely to have benefit with this approach to the CP. Patients with prior history of pancreatic surgery and those patients younger than 45 years of age were less likely to respond to CPB via the EUS approach. The authors of this study also suggest that in addition to being more effective than CT-guided approaches, EUSCPB is more cost effective. A significant limitation to these studies is the lack of a validated pain questionnaire during the evaluation of pain responses of patients [37]. At best, EUSCPB provides relatively short-term relief of CP symptoms [38]. To rank the procedures, then, EUS-CPB would be superior among the three, followed by CT-guided approach, and finally, fluoroscopic guidance. From a practical standpoint, however, CT-guided CPB would be the preferred approach in the hands of an interventional physician performing this procedure. EUS-CPB requires specialized equipment with expertise in endoscopic ultrasound, typically limited to gastroenterologists. CT-guidance is more readily available, and direct visualization and identification of nervous and visceral structures is obtained along with tracking images of contrast dye spread. Scar tissue formation and altered anatomical relationships after pancreatic surgery possibly accounting for the decreased efficacy of the EUS-CPB in those patients would be directly visualized with assistance of CT, and may be more effective than EUS.
Block Injectate CPB for CAP typically is performed with local anesthetic. The use of steroids has been advocated along with local anesthetics in CPB [39]. The purported benefit of adding steroids is to decrease edema and inflammation due to the release of pancreatic enzymes in patients with CP. Busch et al. evaluated 16 patients with depot steroid combined with local anesthetic; four patients without narcotic dependence and prior surgery were noted to have benefit with steroid therapy during block. Based on the results of this study, a mixture of local anesthetic, typically bupivacaine along with triamcinolone, has been customarily utilized [40]. In a single center, blinded, randomized, controlled trial of 40 adult patients referred for EUSCPB for treatment of painful CP, Stevens et al. [37] showed no significant differences in primary outcomes between groups (14.3 % for patients who received triamcinolone vs. 15.8 % for controls); there were no significant differences in the change in VAS or McGill pain scores, change in narcotic requirements, or quality of life found in patients.
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Complications (Table 1) Deleterious consequences due to CPB may occur despite technical expertise and with image-guided modalities. Described risks include hypotension, diarrhea, vascular injection, spinal cord and nerve damage, retroperitoneal and visceral hematoma, abscess and discitis. Hypotension and diarrhea are among the more common effects due to the sympathectomy that occurs after a successful block. The loss of sympathetic tone of the splanchnic vessels can lead to hypotension, as well as a relative increase in parasympathetic activity of the abdominal viscera leading to diarrhea. There have also been recent case reports of anterior spinal cord infarction causing paraplegia, as well as a fatality following endoscopic ultrasound guided celiac plexus neurolysis [41, 42].
Conclusions Celiac plexus block is a valuable adjunctive therapy for managing abdominal pain associated with a visceral pathology. Pain reduction is consistently demonstrated following successful block, and there is the potential for reducing opioid consumption and opioid-related side effects and complications. Whether or not the implementation of neurolysis using this technique enhances or prolongs life expectancy in terminal cancer, however, remains to be seen. A variety of imaging Table 1 Complications of celiac plexus blocks • Hypotension • Diarrhea • Paresthesias of lumbar somatic nerves • Intravascular injection (arterial or venous) • Lumbar somatic nerve root injury • Subarachnoid or epidural injection • Renal injury • Paraplegia • Pneumothorax • Chylothorax • Vascular thrombosis or embolism • Vascular trauma • Perforation of cysts and tumors • Intradiscal injections and discitis • Injection into the psoas muscle • Abscess • Peritonitis • Retroperitoneal hematoma • Ureteral injury • Ejaculation failure • Pain both during, or after the procedure • Failure to derive an analgesic response
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techniques and approaches to the plexus are available, each of which boasts some advantage over the others. The clinician undertaking CPB should be well-versed in not only abdominal and retroperitoneal anatomy, but also in the anatomy and physiology of spinal nerves and the spinal cord, and should be prepared to deal with the many expected and occasionally unexpected sequelae following CPB. Compliance with Ethics Guidelines Conflict of Interest Dr. Maunak V. Rana, Dr. Kenneth D. Candido, Dr. Omar Raja, and Dr. Nebojsa Nick Knezevic each declare no potential conflicts of interest relevant to this article. Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by any of the authors. Disclaimers None. Financial Support None.
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