Sonographically Guided Ilioinguinal Nerve Block

Transcription

1 Technical Advance Sonographically Guided Ilioinguinal Nerve Block Michael Gofeld, MD, Monique Christakis, MD, FRCPC Objective. The aim of this study was to describe a sonographically guided ilioinguinal nerve block in adults. Methods. We developed a useful step-by-step technique of sonographically guided ilioinguinal nerve block based on visualization of abdominal muscles, fascial planes, and the branch of the deep circumflex iliac artery. Results. We performed 9 sonographic examinations with subsequent blockade of the ilioinguinal nerve. All injections resulted in a clinically successful sensory block. Conclusions. This technique is reliable and reproducible. The block is achievable by a low-volume local anesthetic injection. Visualization of the intestines and blood vessels in the abdominal wall may help prevent an inadvertent injury. Key words: ilioinguinal block; sonography; ultrasound. Abbreviations ASIS, anterior superior iliac spine; IHN, iliohypogastric nerve; IIN, ilioinguinal nerve; IINB, ilioinguinal nerve block Received April 18, 2006, from the Departments of Anesthesia (M.G.) and Diagnostic Imaging (M.C.), Sunnybrook Health Sciences Center, Toronto, Ontario, Canada. Revision requested May 6, Revised manuscript accepted for publication June 29, Address correspondence to Michael Gofeld, MD, Department of Anesthesia, Sunnybrook Health Sciences Center, 2075 Bayview Ave, MG-630, Toronto, ON M4N 3M5, Canada M4N 3M5. michael.gofeld@sunnybrook.ca An ilioinguinal nerve block (IINB) is a simple and useful regional anesthesia technique for intraoperative and postoperative analgesia for inguinal surgery. 1 3 This technique has proved to be superior and cost-effective in comparison with both subarachnoid and general anesthesia. 4 A carefully performed blockade may also be helpful in the differential diagnosis of chronic inguinal and lower abdominal pain. Despite its seemingly easy implementation, a relatively high failure rate of 10% to 25% has been reported. 5 Moreover, blind injection may result in inadvertent injury to the intestine 6,7 or blood vessels. 8 Femoral nerve palsy has also been reported. 9 Direct sonographic visualization of the ilioinguinal nerve (IIN) might improve the quality of the block and reduce the risk of complications. This technique has been described explicitly for pediatric inguinal surgery. 10 Although blind IINB seems more difficult in adults, to our knowledge, no report of the use of ultrasound for these patients has been published. A bulky subcutaneous fat layer and fully developed muscles that cover relatively tiny nerves may lead to ultimate failure of such attempts. The IIN (nervus ilioinguinalis) arises from the first lumbar nerve. It emerges from the lateral border of the psoas major just below the iliohypogastric nerve (IHN), passes 2006 by the American Institute of Ultrasound in Medicine J Ultrasound Med 2006; 25: /06/$3.50

2 Sonographically Guided Ilioinguinal Nerve Block obliquely across the quadratus lumborum and iliacus, perforates the transverse muscle above the iliac crest, and communicates with the IHN between the transverse and internal oblique muscles. The IHN lies somewhat medial to the IIN. The nerve then pierces the internal oblique muscle, distributing filaments to it, and lies between the external and internal oblique muscles (Figure 1) and descends medially and caudally, accompanying the spermatic cord through the subcutaneous inguinal ring. 11 This report describes a technique of sonographically guided IINB in adults. Figure 1. Applied anatomy. The superficial muscular layer contains IINs and IHNs that lie between the internal and external oblique muscles. In the deep fascial layer (inset), IINs and IHNs lie between the internal oblique and transverse muscles at the same plane as the branch of the deep circumflex iliac artery. Materials and Methods A 38-mm broadband (13-6 MHz) linear array transducer is ideal to explore regional anatomy and to perform the block. Before an ultrasound examination is started, the following skin landmarks should be indicated: anterior superior iliac spine (ASIS), ilioinguinal ligament, and the line connecting the ASIS with the umbilicus (Figure 2). The ASIS is the standard starting position from which the transducer should be slowly moved along the ASIS-umbilicus line (Figure 3). The adult IIN can be visualized (but not necessarily as reliably as in children) between the internal oblique and transverse or external oblique muscles and within 1 to 3 cm from the ASIS (Figure 4). The IHN lies immediately adjacent or somewhat medial to it. A needle is inserted laterally through the entry point to the transducer (Figure 3) and advanced along the long axis in line with the ultrasound beam. Although a 25-gauge, 38-mm hypodermic needle can be used for a lean person, a 22-gauge Quincke-type spinal needle is usually required to reach the target. A subsequently injected local anesthetic encircles the nerve, which appears as a distinct hypoechoic structure highlighted by the hyperechoic surrounding fat (Figure 5). Frequently, however, the nerve cannot be visualized as a distinct structure. In that situation, color Doppler imaging can facilitate accurate needle placement. A branch of the deep circum- Figure 2. Surface anatomy and landmarks; 1 indicates ASIS; and 2, line connecting the ASIS and umbilicus J Ultrasound Med 2006; 25:

3 Gofeld and Christakis enough to achieve dense blockade of the nerve. Separation of fasciae can be clearly seen. Results Figure 3. Ultrasound transducer positioned at the short axis to the nerve course. X marks the needle entry point. flex iliac artery lies in the same anatomic plane, between the internal oblique and transverse muscles and nearly parallel to the IIN. 12 This artery can be readily identified by sonography with color Doppler imaging (Figure 6). Injection of 2 to 3 ml of local anesthetic adjacent to the artery will invariably anesthetize the IIN and IHN. In the least plausible case, when neither the nerve nor adjacent artery can be identified, one should rely on visualization of the muscle layers. The block needle is consequently inserted into the interspaces between the internal and external oblique muscles and between the transverse and internal oblique muscles (Figure 7). Usually, deposition of 5 ml of local anesthetic is A total of 9 patients were studied. The indication for the procedure was chronic pain at the inguinal area in 8 patients; hence, the block was performed for diagnostic purposes. One block was done during an operation for ilioinguinal hernia repair. The IIN was found as a distinct fascial split between the external and internal oblique muscles in 5 patients; in the other 3 patients, the block was performed laterally to the branch of the deep circumflex iliac artery between the internal oblique and transverse muscles; in 1 patient, the first attempt to find the nerve failed because of the bulky subcutaneous fat layer, and the anesthetic was injected between the muscle layers on a separate occasion. In 3 examinations, 2 nerves (ie, IIN and IHN) were seen separately. The block was successful in all patients, as determined by the anesthesia of the skin at the inguinal area. In 5 patients, the diagnosis of ilioinguinal neuralgia was established. Others had no pain relief despite anesthesia of the corresponding area. Postoperative pain was adequately controlled in only 1 surgical patient, who required 2 oxycodone/acetaminophen tablets (5/325 mg; Percocet; Endo Pharmaceuticals, Chadds Ford, PA) before discharge. Figure 4. Fascial split containing the IIN; 1 indicates exterior oblique muscle; 2, interior oblique muscle; and 3, transverse muscle. Figure 5. Site of injection of local anesthetic. The anesthetic solution encircles the IIN, which is clearly visualized as a hypoechoic structure. J Ultrasound Med 2006; 25:

4 Sonographically Guided Ilioinguinal Nerve Block Figure 6. The branch of the deep circumflex iliac artery lies at the same fascial plane as the IIN, which is highlighted with color Doppler imaging; 1 indicates external oblique muscle; 2, internal oblique muscle; 3, transverse muscle; red spot, branch of the deep circumflex iliac artery; and arrow, IIN. Discussion An IINB seems to be a simple and straightforward technique based on surface anatomy and visible skin landmarks. The anatomic pathway of the nerve has been illustrated previously, 11 and several descriptions of the conventional technique have been published, all of which are based on the subjective feeling of a fascial click when the needle pierces the deep fascia of the external oblique muscle. There is no agreement, however, about where the needle should be placed. One expert recommends starting 2 cm medial and 2 cm cephalad to the ASIS 13 ; another recommends that the needle be inserted 2 in medial and 2 in inferior to the ASIS. 14 In fact, the site where the nerve perforates the internal oblique muscle is subject to great anatomic variability. 15 This inconclusiveness of recommendations about the block technique, somewhere medial from the ASIS, merely confirms the ambiguity in the nerve pathway. Conversely, the nerve passes consistently between the internal oblique and transverse muscles above the ASIS. Such a deep needle insertion seems dangerous for a routine peripheral nerve block because of proximity to the abdominal cavity and intestines. In reality, the courses of both the IIN and the IHN are consistent with those described in anatomy texts in only 41.8% of patients. The absence of one or both is estimated as high as 12.5%, whereas the rate of occurrence of an accessory IIN or IHN is approximately 5%. 16 Although anatomic deviation could potentially be overcome by a large-volume local anesthetic injection and a fanlike deposition of the injectant, visualization of applied anatomy seems to be more feasible, predictable, and safe. Sonography is the only routinely available tool for real-time soft tissue imaging. In conclusion, this simple anatomic technique may greatly improve the success of the INB, reduce the volume of local anesthetic, and prevent potential injury of adjacent structures. References Figure 7. Sonographic appearance of muscular layers. Arrows indicate hyperechoic fascia separating external and internal oblique muscles; and arrowheads, hyperechoic fascia separating internal oblique and transverse muscles. 1. Shandling B, Steward DJ. Regional analgesia for postoperative pain in pediatric outpatient surgery. J Pediatr Surg 1980;15: McLoughlin J, Kelley CJ. Study of the effectiveness of bupivicaine infiltration of the ilioinguinal nerve at the time of hernia repair for post-operative pain relief. Br J Clin Pract 1989; 43: Bunting P, McConachie I. Ilioinguinal nerve blockade for analgesia after caesarean section. Br J Anaesth 1988; 61: Song D, Greilich NB, White PF, Watcha MF, Tongier WK. Recovery profiles and costs of anesthesia for outpatient unilateral inguinal herniorrhaphy. Anesth Analg 2000; 91: van Schoor AN, Boon JM, Bosenberg AT, Abrahams PH, Meiring JH. Anatomical considerations of the pediatric ilioinguinal/iliohypogastric nerve block. Paediatr Anaesth 2005; 15: J Ultrasound Med 2006; 25:

5 Gofeld and Christakis 6. Johr M, Sossai R. Colonic puncture during ilioinguinal nerve block in a child. Anesth Analg 1999; 88: Amory C, Mariscal A, Guyot E, Chauvet P, Leon A, Poli- Merol ML. Is ilioinguinal/iliohypogastric nerve block always totally safe in children? Paediatr Anaesth 2003; 13: Vaisman J. Pelvic hematoma after an ilioinguinal nerve block for orchialgia. Anesth Analg 2001; 92: Lipp AK, Woodcock J, Hensman B, et al. Leg weakness is a complication of ilio-inguinal nerve block in children. Br J Anaesth 2004; 92: Willschke H, Marhofer P, Bosenberg A, et al. Ultrasonography for ilioinguinal/iliohypogastric nerve blocks in children. Br J Anaesth 2005; 95: Gray H. Anatomy of the Human Body. New York, NY: Bartleby.com; 2000; Available at: com/107/. 12. Clemente CD. Anatomy: a regional atlas of the human body. 1st ed. Baltimore, MD: Williams & Wilkins; Reynolds L, Kedlaya D. Ilioinguinal-iliohypogastric and genitofemoral nerve blocks. In: Waldman SD (ed). Interventional Pain Management. 2nd ed. Philadelphia, PA: WB Saunders Co; 2001: Waldman SD. Atlas of Pain Management Injection Techniques. Philadelphia, PA: WB Saunders Co; Jamieson RW, Swigart LL, Anson BJ. Points of parietal perforation of the ilioinguinal and iliohypogastric nerves in relation to optimal sites for local anaesthesia. Q Bull Northwest Univ Med Sch 1952; 26: al-dabbagh AK. Anatomical variations of the inguinal nerves and risks of injury in 110 hernia repairs. Surg Radiol Anat 2002; 24: J Ultrasound Med 2006; 25: