9-4 Pain Localization and Control Wagih W. Gobrial The female pelvis contains diverse, multiple, and intricately thetically mediated pain.Patients with malignancy,who get innervated structures that are potential sources of pain. As good relief although short-lived, might benefit from neu- an example, when the etiologic process is gynecologic rolytic blocks. cancer, which tends to spread locally either by direct inva- Neurolytic blocks are done using the same technique. sion or by spread of metastases to regional lymph notes, However, instead of using a local anesthetic, a neurolytic pain can be present at multiple sites simultaneously. agent is used, such as alcohol (because it is hypobaric and Pelvic pain is particularly difficult to manage because it the patient is in a prone position) or 6% phenol (occa- is often vague, poorly localized, and tends to be bilateral or sionally used, if a hyperbaric solution is needed). The to cross the midline. Thus, a systematic approach to pelvic patient must be made aware of the risks and side effects of pain is the best approach. A careful review of history and the neurolytic block before proceeding. physical examination may give a clue about the source and type of pain. Cooperation with a specialist in gynecology, urology, or colorectal surgery is helpful in identifying the Differential Spinal Block most likely location of the painful stimulus during a directed pelvic examination. There are two ways to accomplish this block: Two types of diagnostic blocks are typically performed to try to ascertain the source of the pain and hence devise 1. Standard differential block. This is done by intrathecally a treatment plan: injecting several solutions. Injections are spaced 5 to 10 minutes apart and the patient is evaluated after each 1. Differential spinal block – to differentiate between injection. psychological, central, sympathetically medicated, or A. The first solution is 5mL of preservative-free normal somatic pain saline. If the patient gets pain relief from the saline 2. Sympathetic block – to impact nerves directly supply- injection, this might be attributed to: ing the pelvic structures 1. Placebo effect (reported in up to 30% of patients), A. Superior hypogastric plexus block: Specifically which is usually short-lived and the pain usually useful for pelvic pain arising from the uterus and comes back in a few minutes. upper vagina, bladder, prostate, urethra, seminal 2. Psychological pain, in which case the patient gets vesicles, testes, and ovaries; pelvic pain secondary an extended pain relief, which may last for days to radiation; sympathetically maintained pain (e.g., or even permanently. after rectal anastomosis, abdominoperineal resec- B. If no relief is achieved, the second solution will be 4 tion, etc.); and chronic pelvic inflammatory to 5mL of 0.5% procaine,with 5mL of normal saline. processes.1 This will block the sympathetic fibers without B. Inferior hypogastric block: Primarily useful for sensory or motor effects. If the patient gets pain perineal pain either malignant or sympathetically relief with this injection, the pain is probably sym- mediated, and superficial hyperesthesia including pathetically mediated and the patient will benefit sensation of severe burning and urgency. from a sympathetic block. C. The third solution is 1mL of 5% procaine added to Both blocks are done initially with a local anesthetic, as 9mL of normal saline – somatic blockade. If the diagnostic/therapeutic blocks. Local anesthetic blocks are patient gets pain relief, the pain is somatic in origin therapeutic if done multiple times in patients with sympa- and treatment should be focused on this direction. 259 260 Pain and Irritative Syndromes Therapy D. The fourth solution is 2mL of 5% procaine added to 2mL of saline. This would cause a complete motor block. If the patient continues to have the pain after complete motor and sensory spinal block, the patient’s pain is considered central. This might be caused by a true organic lesion above the level of the spinal block (that is why spinal differential block is done above the suspected pain level), encephaliza- tion of the pain because of the intensity and direc- tion, psychologically mediated pain, or the patient may be malingering. 2. Retrograde differential spinal block (more frequently used). This is done by using two solutions. A. The first solution is 2mL of normal saline, same interpretations as in the standard differential spinal block. B. The second solution is 1mL of 10% procaine and 1mL of cerebral spinal fluid. This will give complete motor and sensory spinal blockade. If the patient’s pain continues, it is central. If the patient’s pain resolves,pain assessment should be performed every 10 minutes until there is a return of motor and then sensory function. If the pain returns with the return of the sensory function,the pain is somatic in origin. If the pain returns a few hours after the return of the sensory function, it is sympathetically mediated pain. Sympathetic Blocks Anatomic Considerations Figure 9-4.1. Anatomy of superior and inferior hypogastric plexuses.(Reprinted from Raj Sometimes referred to as presacral nerve, the superior PP,Lou L,Erdine S,et al.Radiographic Imaging for Regional Anesthesia and Pain Management,p 231, hypogastric plexus is formed by the confluence of the Copyright 2003, with permission from Elsevier.) lumbar sympathetic chains and branches of the aortic plexus, which contain fibers that traverse the celiac and inferior mesenteric plexuses (Figure 9-4.1). In addition, it usually contains parasympathetic fibers that originate in Technique of Superior Hypogastric Plexus Block the ventral roots of S2-S4 and travel along pelvic splanch- nic nerves through the inferior hypogastric plexus. The The patient is positioned on the fluoroscopy table in prone plexus is located in the retroperitoneum, anterior to the position. Using fluoroscopic guidance, the L4-5 spinal body of the lower part of L5, and upper part of S1. It is pos- process is identified. Going laterally, a 7-cm skin marker is terior to the bifurcation of the aorta and both common iliac made and this will be the point of needle entry. The arteries, and left common iliac vein. The superior hypogas- lumbarsacral area is prepped and draped in a sterile tric plexus divides into right and left hypogastric nerves, manner. Multiple approaches have been described, includ- which descend lateral to the sigmoid colon and rectosig- ing a lateral approach, medial approach, and the intradiskal moid to reach the two inferior hypogastric plexuses. The approach – the approach that is most often used is the superior hypogastric plexus gives off branches to the lateral approach (Figure 9-4.2). At 7-cm lateral to the L4-5 ureteric and testicular (or ovarian) plexus, the sigmoid interspace, the skin and deeper tissue and muscles are colon, and the internal iliac artery. In addition to the path- infiltrated with lidocaine 0.5% using a 20-gauge 6-in ways that traverse the superior hypogastric plexus, sympa- needle. The needle is directed 45 degrees medially and cau- thetic fibers also reach the plexus through perivascular dally to miss the transverse process of L5 and the sacral ala pathways that include the inferior mesenteric plexus on anteroposterior (AP) fluoroscopy view (Figure 9-4.3). (sigmoid, colon, and rectum) and renal plexus (ureteric The needle must be more than 1cm from the bony outline. and ovarian or testicular plexuses). On the lateral view, the needle tip should be at the anterior Pain Localization and Control 261 monitored in the postanesthesia care unit for the duration of pain relief, which should be for several hours. If it is short-lived (15–30 minutes), it is usually a placebo effect. CT guidance can be used for this block.2 Inferior Hypogastric Plexus The inferior hypogastric plexus is a bilateral abdominal structure situated on each side of the rectum, lower part of the bladder and (in men) prostate and seminal vesicles or (in women) cervix, uterus, and vaginal fornices (Figure 9- 4.4). The inferior hypogastric plexus supplies branches to the pelvic viscera directly, as well as from subsidiary plexuses (e.g., the superior, middle rectal, vesical, prostate, and uterovaginal plexuses). The sacral sympathetic trunk lies in the parietal pelvic fascia behind the parietal peri- toneum and on the ventral surface of the rectum, just medial to its anterior foramina and the existing sacral nerves. Below they converge and unite to form a solitary small “ganglion impar” which is located anterior to the sacrococcygeal junction. Technique of Inferior Hypogastric Block Multiple approaches, such as lateral, prone, and lithotomy have been described (Figure 9-4.5).3 The most frequently used approach is the prone position. The sacrococcygeal area is prepped and draped in a sterile manner. The entry site, just under the tip of the coccyx, is anesthetized with lidocaine 0.5% using a 25-gauge needle. A 22-gauge, 3.5-in spinal needle is bent into a C shape (commercial C shape 22-gauge, 3.5-in spinal needles are also available). At the site of entry, just under the coccyx, the needle is advanced in a semicircular manner under fluoroscopy (lateral view) until the top of the needle is just anterior to the sacrococ- Figure 9-4.2. Lateral view of superior hypogastric block. surface of the junction of L5-S1. It is further advanced, and loss of resistance usually occurs at this point. Confirmation of the location of the needle is done with injection of radio- opaque dye and the spread is followed both in AP and lateral views. After confirmation of the position of the needle and negative blood aspiration, a test dose of bupi- vacaine 0.375% (2–3mL) is injected. Patient evaluation is done a few minutes after the injection, to confirm there is no sensory or motor blockade.