- Email: [email protected]
Repeated failure of epidural analgesia: An association with epidural fat?
Repeated Failure of Epidural Analgesia: An Association With Epidural Fat? Scott A. Lang, M.D., F.R.C.P.C., Peter Korzeniewski, M.D., F.R.C.P.C., Donald Buie, M.D., F.R.C.S.C., Stephan du Plessis, M.B., Ch.B., M.Med., Kimiko Paterson, M.D., and Gary Morris, M.D., F.R.C.P.C. Background and Objective: To report the case of a patient who experienced repeated failed epidural analgesia associated with an unusual amount of fat in the epidural space (epidural lipomatosis). Case Report: A 44-year-old female presented for an elective small bowel resection. An L1-2 epidural catheter was placed for postoperative analgesia. The patient gave no indication of having pain at the time of emergence from general anesthesia or in the first 2 hours in the recovery room. Assessment of the level of hypoesthesia to ice while the patient was comfortable in the recovery room suggested a functional epidural catheter (cephalad level of T10). Two hours after admission to the recovery room the patient began to complain of increasing pain. Another 6 mL 0.25% bupivacaine was administered via the catheter. The patient’s pain decreased, but remained substantial, and there was minimal evidence of sensory block above the T10 level. Subsequently, a T10 epidural catheter was placed. Testing confirmed proper placement of the catheter in the epidural space at the T10 level. A test dose of 5 mL 0.25% bupivacaine resulted in prompt and complete relief of the patient’s pain. However, the level of hypoesthesia to ice did not exceed the T10 level. Approximately 1 hour later the patient complained of increasing discomfort again. There was no evidence of any sensory block, and there was no response to a bolus of 8 mL 1% lidocaine. A thorough examination of the patient did not suggest any cause for the pain other than a malfunctioning epidural catheter. A third epidural catheter was placed at the T8-9 level. This catheter was again confirmed to be in the epidural space with a test dose of 10 mL 0.5% bupivacaine. The level of hypoesthesia to ice was restricted to a narrow bilateral band from T7-T9. Analgesia failed 2 hours later. The epidural catheter was removed and the patient’s pain was subsequently managed with intravenous patient-controlled analgesia (PCA) morphine. A magnetic resonance imaging (MRI) scan revealed extensive epidural fat dorsal to the spinal cord from C5-C7 and from T3-T9. An imaging diagnosis of asymptomatic epidural lipomatosis was established. Conclusion: We have described a case of repeated failure of epidural analgesia in a patient with epidural lipomatosis. Reg Anesth Pain Med 2002;27:494-500. Key Words:
Analgesia, Epidural, Laparotomy, Lipomatosis, Tachyphylaxis, Tsui test.
I
nadequate epidural analgesia has been associated with undesirable catheter location in the epidural space1,2 (e.g., anterior or lateral epidural space), compartmentalization of administered drugs by tissue barriers3,4 (e.g., plica mediana dorsalis, mucopolysaccharide), catheter migration5,6 (e.g., in-
From the Departments of Anesthesia (S.A.L., P.K.), Surgery (D.B., S.d.P.), and Radiology (K.P.), Foothills Hospital, University of Calgary, Calgary, Alberta, Canada; and the Department of Anesthesia (G.M.), Royal University Hospital, University of Saskatchewan, Saskatoon, Canada. Accepted for publication March 26, 2002. Supported by Department of Anesthesia funds, Calgary. Reprint requests: Scott A. Lang, M.D., F.R.C.P.C., Department of Anesthesia, Foothills Hospital, 1403-19th St NW, Calgary, Alberta, Canada T2N 2T9. E-mail: [email protected]. © 2002 by the American Society of Regional Anesthesia and Pain Medicine. 1098-7339/02/2705-0010$35.00/0 doi:10.1053/rapm.2002.34323
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travascular, intramuscular), and erroneous catheter placement7,8 (e.g., paravertebral, interpleural). Equipment and technical factors may also influence the adequacy of epidural analgesia9,10 (e.g., catheter kinking, catheter occlusion, catheter-hub disconnect, catheter breakage). Even the mode of drug delivery has been implicated in restricted epidural spread and inadequate analgesia.11,12 We present a case of repeated failure of epidural analgesia in a patient with epidural lipomatosis. Three epidural catheters were placed for postoperative analgesia in succession. Analgesia was established initially with each catheter, but quickly faded. Analgesia could only be temporarily and briefly reestablished with large doses of local anesthetic. Despite large doses of local anesthetic, evidence of conduction block was restricted. The literature is briefly reviewed and a hypothesis presented for consideration.
Regional Anesthesia and Pain Medicine, Vol 27, No 5 (September–October), 2002: pp 494 –500
Failed Epidural Analgesia and Epidural Lipomatosis
Case Report A 44-year-old Caucasian female (weight, 50.9 kg; height, 175 cm; body mass index [BMI], 16.4) presented for an elective small bowel resection. She had a probable diagnosis of Crohn’s disease and had been suffering from postprandial crampy abdominal pain, nausea, occasional vomiting, abdominal distention, and borborygmi. She had lost 4.4 kg in the 5 months prior to her scheduled surgery. By history she also had Ehlers-Danlos syndrome and Ankylosing Spondylitis. She underwent a right hemicolectomy in 1996 for a cecal bezoar. At the time of admission, she was taking acetaminophen/ oxycodone, fluoxetine, Pentasa (5-aminosalicylic acid), lansoprazole, trimebutine, Buscopan (hyoscine butylbromide), metoclopramide, levothyroxine, cyclobenzaprine, zopiclone, and oral iron. She had been on prednisone intermittently for symptomatic flare-ups from 1987 to 1997. Enteroclysis demonstrated proximal small bowel dilatation with a decompressed terminal ileum suggestive of mechanical small bowel obstruction and she was scheduled for a laparotomy with possible small bowel resection. An L1-2 epidural catheter (Portex; Sims Portex, Keene, NH) was placed for postoperative analgesia via a 17-gauge Tuohy needle. The catheter was placed using a loss of resistance (LOR) with saline technique via a midline approach. The catheter was easily inserted 6 cm. There was no indication of blood or cerebrospinal fluid via either the needle or the catheter. Cefazolin, 1 gm, and metronidazole, 500 mg, were administered intravenously. General anesthesia was induced with a combination of intravenous fentanyl (250 g) and propofol (100 mg). Endotracheal intubation was facilitated with rocuronium (3 mg) followed by succinylcholine (70 mg). Anesthesia was maintained with desflurane, supplemental intravenous fentanyl (150 g), and a bolus of 6 mL 0.5% bupivacaine via the epidural catheter. Muscle relaxation was maintained with rocuronium (total of 30 mg). An upper abdominal incision (approximately T6-T11 dermatomes) was used. Multiple small bowel strictures were found and treated with resection and stricturoplasty and surgery was completed uneventfully. As the anesthetic lasted over 2 hours, the neuromuscular paralysis from the rocuronium was allowed to dissipate spontaneously. The trachea was extubated after resumption of spontaneous respirations, and the patient was transferred to the recovery room. The patient gave no indication of having pain at the time of emergence from general anesthesia or in the first 2 hours in the recovery room (Verbal Pain
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Score 3-4/10; 0 ⫽ no pain, 10 ⫽ worst pain). Assessment of the level of hypoesthesia to ice while the patient was comfortable in the recovery room suggested a functional epidural catheter (cephalad level of T10). The epidural catheter was promptly connected to an Abbott Pain Manager II patientcontrolled analgesia pump (Abbott Laboratories, North Chicago, IL) containing 0.1% bupivacaine and 5 g/mL fentanyl (continuous infusion 7 mL/h, bolus 4 mL, lockout interval 12 minutes). Two hours after admission to the recovery room the patient began to complain of increasing pain. Another 6 mL 0.25% bupivacaine was administered via the catheter. The patient’s pain decreased, but remained substantial (Verbal Pain Rating decreased from 8 to 6), and there was little evidence of sensory block above the T10 level (ice and pin prick assessments). Subsequently, a T10 epidural catheter (Arrow FlexTip Plus Catheter, Product #JH-05500; Arrow International, Reading, PA) was placed with the patient in the left lateral decubitus position via a left paramedian approach with a 17-gauge Tuohy needle and a LOR to air technique. A confirmatory (Tsui) test13 again suggested proper placement of the catheter in the epidural space at the T10 level (bilateral motor response at approximately the T10 level at 5.0 mamp with a Digistim II nerve stimulator (Neurotechnology, Houston, TX, pulse width 200 sec, 1 Hz). A test dose of 5 mL 0.25% bupivacaine resulted in prompt and complete relief of the patient’s pain. However, the level of hypoesthesia to ice did not extend cephalad to the T10 level. The new catheter was attached to the patient-controlled epidural analgesia (PCEA) device. Approximately 1 hour later the patient complained of increasing discomfort again. An acute pain service (APS) physician was called to assess the situation. Again, there was no evidence of any sensory block, and there was no response to a bolus of 8 mL 1% lidocaine. A thorough examination of the patient did not suggest any cause for pain other that a malfunctioning epidural catheter. The patient was told that this was very unusual, but it was likely that both epidural catheters had somehow migrated out of the epidural space. Alternative analgesia was discussed (i.e., intravenous patient-controlled analgesia [IVPCA]), but the patient elected to have another epidural catheter placed. A third epidural catheter (Portex; Sims Portex) was placed in the left lateral decubitus position via a midline approach with a 17-gauge Tuohy needle and a LOR to air technique at the T8-9 level. This catheter was tested with 10 mL 0.5% bupivacaine. Analgesia was re-established. However, the level of
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Fig 1. MRI and illustration of the thoracic spine and epidural space. (Inset) a, Abnormal amount of epidural fat; b, spinal cord; c, subcutaneous fat; d, Cerebrospinal fluid; e, normal epidural space and fat; f, dura; g, lamina of vertebra; h, Ligamentum flavum. (A) T1W1 (400/8/3) (repetition time/echo time/number of excitations). Sagittal T1-weighted imaging of a normal thoracic spine. (B) T1W1 (400/8/3). Sagittal T1-weighted imaging of the thoracic spine of the patient. An excessive amount of epidural fat is noted posteriorly in the central canal extending from T3 to T9. This epidural fat does not compress the thecal sac or spinal cord and has a high intensity signal (white) similar to the subcutaneous fat. The adjacent cerebrospinal fluid (CSF) has a low intensity signal (black), while the spinal cord has an intermediate intensity signal (dark grey).
hypoesthesia to ice was restricted to a narrow bilateral band from T7-T9. Analgesia failed 2 hours later. The epidural catheter was removed and the patient’s pain was subsequently managed with intravenous patient-controlled morphine (bolus dose 1.5 mg, lockout 6 minutes, no maximum) (Lifecare 4100 PCA Plus Infusor; Abbott Laboratories). A more detailed history acquired the next day revealed that several months ago she had been treated with oral prednisone for a presumptive diagnosis of Crohn’s disease. The patient agreed to a magnetic resonance imaging (MRI) scan of her spine. A neurosurgical consultation was acquired to facilitate the acquisition and interpretation of the MRI scan and to provide advice if any abnormality was found. The MRI scan
revealed extensive epidural fat dorsal to the spinal cord from C5-C7 and from T3-T9 (Fig 1A through D). A diagnosis of epidural lipomatosis was established. There was no evidence of spinal cord compression. As the patient was currently asymptomatic, she was discharged home with instructions to see her family physician regularly for reassessment regarding the diagnosis of epidural lipomatosis. A pathologic examination of the tissue removed at the time of surgery revealed diaphragm-like strictures in the resected specimen of small bowel. These were interpreted as likely secondary to nonsteroidal antiinflammatory drug treatment. There was no evidence of Crohn’s disease. The patient was discharged home with instructions to see her surgeon in 3 weeks time.
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Fig 1. (Cont’d) (C) T2W1 (3000/98.7/4). On sagittal T2-weighted imaging of the same region of thoracic spine, the excessive amount of epidural fat continues to have a high intensity signal (white) similar to the subcutaneous fat. The CSF has a high intensity signal (light grey), and the spinal cord has a low intensity signal (dark grey). (D) T1W1 (256/160/3). On axial T1-weighted imaging at the level of T6, the excessive amount of epidural fat occupies the posterior half of the central canal without spinal cord or thecal sac compression.
Discussion Inadequate epidural analgesia is a problem faced regularly on any acute pain service. The differential diagnosis can be lengthy, and troubleshooting can be labor-intensive (Table 1). Despite this, we believe that all 3 epidural catheters in our patient were placed properly. The Tsui test uses an electric current to stimulate motor nerve rootlets in the epidural space.13,14 The sensitivity and specificity of the Tsui test for identification of the epidural space are 100% and 91.6%, respectively.13 The first 2 catheters produced evidence of extensive bilateral segmental conduction block to ice below T10 that was associated, temporarily, with good to excellent
pain relief (e.g., total, but temporary, pain relief after 5 mL 0.25% bupivacaine injected via the second catheter). The third catheter (T8-9) produced a very restricted segmental area (T7-9) of hypoesthesia to ice after 10 mL 0.5% bupivacaine that only temporarily relieved the patient’s pain (⬍2 hours). Subsequent injections of local anesthetic via all 3 catheters failed to reproduce analgesia. Large volumes of local anesthetic (6 to 10 mL) failed to extend evidence of conduction block higher than T10 with the first 2 catheters and failed to extend evidence of conduction block outside a narrow T7-9 segmental band with the third catheter. These observations led us to perform a MRI scan to look for a space-occupying lesion.
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Regional Anesthesia and Pain Medicine Vol. 27 No. 5 September–October 2002 Table 1. Epidural Analgesia: Trouble-shooting Failed Analgesia Cause
Management Options
Catheter is not in the epidural space Subcutaneous5 Paraspinal muscle/fat5 Paravertebral7,22 Interpleural8 Intravascular23,24 Catheter is in the epidural space, but is not providing adequate analgesia Catheter in anterior epidural space1,27 Catheter in lateral epidural space2 Catheter or solution migrates out intervertebral foramen2,14,28-31 Catheter not placed at appropriate level (i.e., inadequate analgesia and/or excessive side effects precluding continued use)14,31 Other distribution problem (e.g., extensive dermatomal demand [e.g., thoracoabdominal T4-L1 incision], space occupying lesion [tumor,32 mucopolysaccharide,4 fat2], plica mediana dorsalis,3,33,34 fibrous adhesions,35 epidural air,36,37 diffusion barrier4,38 Pharmacokinetic55-57 problem (e.g., enhanced drug absorption/metabolism) Pharmacodynamic39,55-57 problem (e.g., receptor-mediated tolerance, drug interaction) Neural processing problem36,40,54,57 (e.g., conduction block insufficient to “handle” “intensity” of neural traffic) Central neurogenic pain41 Other source of pain remote from surgical site Technical problem with equipment (obstructed catheter9 [kink,10 connector obstruction or disconnection,9 blood clot, inflammation,38 manufacturing defect42]; pump failure43 [electronic, air-in-the-line, mechanical]) Human error44 (programming error, drug error) Leaking epidural site45,46
Prevent migration from epidural space by ensuring catheter is inserted an optimal distance (4-6 cm)25 and is well secured26 Tsui test13 and epidural local anesthetic test dose to confirm placement and to try to reestablish analgesia Replace catheter or choose alternative analgesic regimen
Tsui test13/local anesthetic test dose may help identify where catheter is Reposition* catheter by pulling it back24,47,48 Change programming parameters (e.g., increase bolus11 dose and/or infusion rate58) Change selection of drug/s (e.g., select opioid only [i.e., less dependence of catheter position49,50]) Replace catheter Identify and address other source/s of pain Identify and address technical problems and human error Apply pressure dressing over epidural exit site (personal observation) or consider crazy glue seal45 Consider dual epidural catheter for extensive dermatome requirements51,52 Consider multimodal53 or hybrid† analgesic regimen Consider epidurogram or MRI Consider consultation for management of chronic pain of central origin
*Controversial issue (pro and con). †Hybrid technique ⬅ A combination of two or more major analgesic interventions (e.g., intercostal nerve block and epidural catheter).
Epidural lipomatosis is a rare disorder.15 However, the experience of some investigators suggests that it may be underdiagnosed.16 It is characterized by an excessive amount of nonencapsulated fat in the epidural space. Excess epidural fat generally occurs in the posterior epidural space and can act as a space-occupying lesion resulting in variable compression of the spinal cord, dural sac, or nerve roots.15 Alternatively, asymmetric deposition of excess epidural fat can cause spinal cord pathology via rotational distortion.17 Patients typically present with back pain or variable symptoms of spinal cord or nerve root compression.15 Men are affected more often than women.15 The pathogenesis of the disorder is unknown.15 It has been reported to occur spontaneously18 or in association with steroid use,
endocrinopathies, or obesity,15,16,18 but may occur in patients without these risk factors.19 MRI is the diagnostic technique of choice.15 Treatment depends on presentation.15 Medical management15 may include strategies to induce weight loss, the elimination of medications thought to have a causal relationship with the development of epidural lipomatosis (e.g., steroids, ritonavir20), and the management of associated endocrinopathies (e.g., Cushing’s syndrome). Surgical management may involve multiple level laminectomies and decompression16,18 or endoscopic suction decompression via small bilateral laminotomies.21 We hypothesize in our patient that the extensive accumulation of epidural fat adversely affected the distribution of the drugs we administered in the
Failed Epidural Analgesia and Epidural Lipomatosis
epidural space (bupivacaine and fentanyl). The fat may have prevented symmetrical distribution of the drugs in the thoracic epidural space. Alternatively, the fat may have acted as a “depot” for the lipid soluble bupivacaine and fentanyl, effectively sequestering the analgesic agents. This could explain the very limited segmental conduction blocks obtained with concentrated solutions of bupivacaine and lidocaine. We hope that this case report stimulates other clinicians to consider such an association and encourages investigators with the appropriate tools to establish an animal model to elucidate the mechanisms by which excess epidural fat may impair epidural analgesia. In conclusion, repeated failure of epidural analgesia together with restricted segmental conduction block after the administration of large volumes of local anesthetic should prompt consideration of epidural lipomatosis. After more common causes of failed epidural analgesia have been ruled out, MRI should be considered.
Acknowledgment We thank Helen Schroeder for her assistance in preparation of this manuscript.
References 1. Asato F, Goto F. Radiographic findings of unilateral epidural block. Anesth Analg 1996;83:519-522. 2. Hogan Q. Epidural catheter tip position and distribution of injectate evaluated by computed tomography. Anesthesiology 1999;90:964-970. 3. Fukushige T, Kano T, Sano T. Radiographic investigation of unilateral epidural block after single injection. Anesthesiology 1997;87:1574-1575. 4. Vas L, Naregal F. Failed epidural analgesia in a patient with Hurler’s disease. Paediatr Anaesth 2000;10:9598. 5. Bishton IM, Martin PH, Vernon JM, Liu WH. Factors influencing epidural catheter migration. Anaesthesia 1992;47:610-612. 6. Bush D, Kramer DP. Intravascular migration of an epidural catheter during postoperative patient-controlled epidural analgesia. Anesth Analg 1993;76: 1150-1151. 7. Tenicela R, Pollan SB. Paravertebral-peridural block technique: A unilateral thoracic block. Clin J Pain 1990;6:227-234. 8. Furuya A, Matsukawa T, Ozaki M, Kumazawa T. Interpleural misplacement of an epidural catheter. J Clin Anesth 1998;10:425-426. 9. Grass JA, Haider N, Group M, Frandsen RN, Mekhail N. Incidence of complications related to epidural catheterization and maintenance for postoperative analgesia. Reg Anesth Pain Med 1998;23:S108. 10. Roddin MJ, Dancey FM. Kinking of epidural catheters. Anaesthesia 2000;55:831.
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11. Kaynar AM, Shankar KB. Epidural infusion: continuous or bolus? Anesth Analg 1999;89:534. 12. Nishimura N, Fujimaki T, Oshibuchi M, Yoshikawa I, Aida M. The distribution of solutions in the epidural space. Masui 1991;40:350-360. 13. Tsui BCH, Gupta S, Finucane B. Confirmation of epidural catheter placement using nerve stimulation. Can J Anaesth 1998;45:640-644. 14. Hayatsu K, Misao T, Hideyoshi F, Baba H, Yamakura T, Taga K, Shimoji K. The placement of the epidural catheter at the predicted site by electrical stimulation test. Anesth Analg 2001;93:1035-1039. 15. Levy-Weil FE, Feldman JL. Epidural lipomatosis. Presse Med 2000;29:469-475. 16. Robertson SC, Traynelis VC, Follett KA, Menezes AH. Idiopathic spinal epidural lipomatosis. Neurosurgery 1997;41:68-75. 17. Tuli SK, Hurlbert RJ, Mikulis D, Fleming JF. Ninetydegree rotation of the thoracic spinal thecal sac. Case report. J Neurosurg 1998;89:133-138. 18. Lisai P, Doria C, Crissantu L, Meloni GB, Conti M, Achene AA. Cauda equina syndrome secondary to idiopathic spinal epidural lipomatosis. Spine 2001;26: 307-309. 19. Huraibi HA, Phillips J, Rose RJ, Pallatroni H, Westbrook H, Fanciullo GJ. Intrathecal baclofen pump implantation complicated by epidural lipomatosis. Anesth Analg 2000;91:429-431. 20. Ebright JR, Stellini MA, Tselis AC. Spinal epidural lipomatosis in a human immunodeficiency viruspositive patient receiving steroids and protease inhibitor therapy. Clin Infect Dis 2001;32:E90-E91. 21. Frank E. Endoscopic suction decompression of idiopathic epidural lipomatosis. Surg Neurol 1998;50:333335. 22. Boezaart AP. Computerized axial tomo-epidurographic and radiographic documentation of unilateral epidural analgesia. Can J Anaesth 1989;36:697700. 23. Bush DJ, Kramer DP. Intravascular migration of an epidural catheter during postoperative patient-controlled epidural analgesia. Anesth Analg 1993;76: 1150-1151. 24. Mulroy MF, Norris MC, Liu SS. Safety steps for epidural injection of local anesthetics: Review of the literature and recommendations. Anesth Analg 1997; 85:1346-1356. 25. D’Angelo R, Berkebile BL, Gerancher JC. Prospective examination of epidural catheter insertion. Anesthesiology 1996;84:88-93. 26. Clark MX, O’Hare K, Gorringe J, Oh T. The effect of the Lockit epidural catheter clamp on epidural migration: A controlled trial. Anaesthesia 2001;56:865870. 27. Sala-Blanch X, Izquierdo E, Fita G, De Jose M, Nalda MA. Maintained unilateral analgesia. Acta Anaesthesiol Scand 1995;39:132-135. 28. Saitoh K, Kawakami N, Hotta K, Hirabayashi Y, Mitsuhata H, Shimizu R. Failures of lumbar epidural analgesia caused by transforaminal passage of an epi-
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Regional Anesthesia and Pain Medicine Vol. 27 No. 5 September–October 2002 dural catheter in two cases. Masui 1994;43:10411043. Elizabet UM, Nystrom MD, Buffington CW. Is there an anatomic explanation for tachyphylaxis in epidural anesthesia? Reg Anesth Pain Med 1999;24:S16. Usubiaga JE, Wikinski JA, Usubiaga LE. Epidural pressure and its relation to spread of anesthetic solutions in epidural space. Anesth Analg 1967;46:440446. Liu SS, Allen HW, Olsson GL. Patient-controlled epidural analgesia with bupivacaine and fentanyl on hospital wards. Anesthesiology 1998;88:688-695. Rathmell JP, Roland T, DuPen SL. Management of pain associated with metastatic epidural spinal cord compression: Use of imaging studies in planning epidural therapy. Reg Anesth Pain Med 2000;25:113-116. Gallart L, Blanco D, Samso E, Vidal F. Clinical and radiologic evidence of the epidural plica mediana dorsalis. Anesth Analg 1990;71:698-701. Husemeyer RP, White DC. Topography of the lumbar epidural space. Anaesthesia 1980;35:7-11. Crul BJP, Delhaas EM. Technical complications during long-term subarachnoid or epidural administration of morphine in terminally ill cancer patients: A review of 140 cases. Reg Anesth Pain Med 1991;16: 209-213. Dalens B, Bazin J-E, Haberer J-P. Epidural bubbles as a cause of incomplete analgesia during epidural anesthesia. Anesth Analg 1987;66:679-683. Boezaart AP, Levendig BJ. Epidural air-filled bubbles and unblocked segments. Can J Anaesth 1989;36:603604. Mercadante S. Neuraxial techniques for cancer pain: An opinion about unresolved therapeutic dilemmas. Reg Anesth Pain Med 1999;24:74-83. Mogensen T, Simonsen L, Scott NB, Henriksen JH, Kehlet H. Tachyphylaxis associated with repeated epidural injections of lidocaine is not related to changes in distribution or the rate of elimination from the epidural space. Anesth Analg 1989;69:180184. Bigler D, Lund C, Mogensen T, Hjortso N-C, Kehlet H. Letter to the Editor: Tachyphylaxis during postoperative epidural analgesia—new insights. Acta Anaesthesiol Scand 1987;31:664-665. Hassenbusch SJ, Stanton-Hicks M, Covington EC, Walsh JG, Guthrey DS. Long-term intraspinal infusions of opioids in the treatment of neuropathic pain. J Pain Symptom Manage 1995;10:527-543. Wee LH. Another cause for failed epidural. Anaesthesia 1994;49:270-271. Burton A. Epidural pump failure. Anesth Analg 1995; 80:1066. Brown SL, Bogner MS, Parmentier CM, Taylor JB.
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Human error and patient-controlled analgesia pumps. J Intraven Nurs 1997;20:311-316. Plummer JL, Cmielewski PL, Gourlay GK, Cherry DA, Cousins MJ, Szep PF, Davies RP. Leakage of fluid administered epidurally to rats into subcutaneous tissue. Pain 1990;42:121-124. Driessen JJ, De Mulder PHM, Claessen JJL, Van Diejen D, Wobbes Th. Epidural administration of morphine for control of cancer pain: Long-term efficacy and complications. Clin J Pain 1989;5:217-222. Beilin Y, Zahn J, Bernstein HH, Zucker-Pinchoff B, Zenzen WJ, Andres LA. Treatment of incomplete analgesia after placement of an epidural catheter and administration of local anesthetic for women in labor. Anesthesiology 1998;88:1502-1506. Yeh C-C, Ho S-T, Wong C-S, Liaw W-J, Wang J-J, Tang JJ-S. Manipulation of epidural catheter that has migrated restores adequate postoperative analgesia—A case report. Acta Anaesthesiol Sin 1998;36:5962. Angst MS, Ramaswamy B, Riley ET, Stanski DR. Lumbar epidural morphine in humans and supraspinal analgesia to experimental heat pain. Anesthesiology 2000;92:312-324. Bernards CM. Rostral spread of epidural morphine: The expected and the unexpected. Anesthesiology 2000;92:299-301. Ekatodramis G, Min K, Cathrein P, Borgeat A. Use of a double epidural catheter provides effective postoperative analgesia after spine deformity surgery. Can J Anesth 2002;49:173-177. Schachner SM, Abram SE. Use of two epidural catheters to provide analgesia of unblocked segments in a patient with lumbar disc disease. Anesthesiology 1982; 56:150-151. Jin F, Chung F. Multimodal analgesia for postoperative pain control. J Clin Anesth 2001;13:524-539. Ueda W, Yuushuke S, Hirakawa M. Role of afferent neural input in regression of sensory paralysis during epidural analgesia. Anesth Analg 1992;74:358-361. Lipfert P. Tachyphylaxis to local anesthetics. Reg Anaesth 1989;12:13-20. Kottenberg-Assenmacher E, Peters J. Mechanisms of tachyphylaxis in regional anesthesia of long duration. Anasthesiol Intensivmed Notfallmed Schmerzther 1999;34:733-742. Reid D. Differential nerve block. Can J Anaesth 1998; 45:1039-1043. Johnson RA, Lopez MJ, Hendrickson DA, DruseElliott KT. Cephalad distribution of three differing volumes of new methylene blue injected into the epidural space in adult goats. Vet Surg 1996;25:448451.
Analgesia, Epidural, Laparotomy, Lipomatosis, Tachyphylaxis, Tsui test.
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nadequate epidural analgesia has been associated with undesirable catheter location in the epidural space1,2 (e.g., anterior or lateral epidural space), compartmentalization of administered drugs by tissue barriers3,4 (e.g., plica mediana dorsalis, mucopolysaccharide), catheter migration5,6 (e.g., in-
From the Departments of Anesthesia (S.A.L., P.K.), Surgery (D.B., S.d.P.), and Radiology (K.P.), Foothills Hospital, University of Calgary, Calgary, Alberta, Canada; and the Department of Anesthesia (G.M.), Royal University Hospital, University of Saskatchewan, Saskatoon, Canada. Accepted for publication March 26, 2002. Supported by Department of Anesthesia funds, Calgary. Reprint requests: Scott A. Lang, M.D., F.R.C.P.C., Department of Anesthesia, Foothills Hospital, 1403-19th St NW, Calgary, Alberta, Canada T2N 2T9. E-mail: [email protected]. © 2002 by the American Society of Regional Anesthesia and Pain Medicine. 1098-7339/02/2705-0010$35.00/0 doi:10.1053/rapm.2002.34323
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travascular, intramuscular), and erroneous catheter placement7,8 (e.g., paravertebral, interpleural). Equipment and technical factors may also influence the adequacy of epidural analgesia9,10 (e.g., catheter kinking, catheter occlusion, catheter-hub disconnect, catheter breakage). Even the mode of drug delivery has been implicated in restricted epidural spread and inadequate analgesia.11,12 We present a case of repeated failure of epidural analgesia in a patient with epidural lipomatosis. Three epidural catheters were placed for postoperative analgesia in succession. Analgesia was established initially with each catheter, but quickly faded. Analgesia could only be temporarily and briefly reestablished with large doses of local anesthetic. Despite large doses of local anesthetic, evidence of conduction block was restricted. The literature is briefly reviewed and a hypothesis presented for consideration.
Regional Anesthesia and Pain Medicine, Vol 27, No 5 (September–October), 2002: pp 494 –500
Failed Epidural Analgesia and Epidural Lipomatosis
Case Report A 44-year-old Caucasian female (weight, 50.9 kg; height, 175 cm; body mass index [BMI], 16.4) presented for an elective small bowel resection. She had a probable diagnosis of Crohn’s disease and had been suffering from postprandial crampy abdominal pain, nausea, occasional vomiting, abdominal distention, and borborygmi. She had lost 4.4 kg in the 5 months prior to her scheduled surgery. By history she also had Ehlers-Danlos syndrome and Ankylosing Spondylitis. She underwent a right hemicolectomy in 1996 for a cecal bezoar. At the time of admission, she was taking acetaminophen/ oxycodone, fluoxetine, Pentasa (5-aminosalicylic acid), lansoprazole, trimebutine, Buscopan (hyoscine butylbromide), metoclopramide, levothyroxine, cyclobenzaprine, zopiclone, and oral iron. She had been on prednisone intermittently for symptomatic flare-ups from 1987 to 1997. Enteroclysis demonstrated proximal small bowel dilatation with a decompressed terminal ileum suggestive of mechanical small bowel obstruction and she was scheduled for a laparotomy with possible small bowel resection. An L1-2 epidural catheter (Portex; Sims Portex, Keene, NH) was placed for postoperative analgesia via a 17-gauge Tuohy needle. The catheter was placed using a loss of resistance (LOR) with saline technique via a midline approach. The catheter was easily inserted 6 cm. There was no indication of blood or cerebrospinal fluid via either the needle or the catheter. Cefazolin, 1 gm, and metronidazole, 500 mg, were administered intravenously. General anesthesia was induced with a combination of intravenous fentanyl (250 g) and propofol (100 mg). Endotracheal intubation was facilitated with rocuronium (3 mg) followed by succinylcholine (70 mg). Anesthesia was maintained with desflurane, supplemental intravenous fentanyl (150 g), and a bolus of 6 mL 0.5% bupivacaine via the epidural catheter. Muscle relaxation was maintained with rocuronium (total of 30 mg). An upper abdominal incision (approximately T6-T11 dermatomes) was used. Multiple small bowel strictures were found and treated with resection and stricturoplasty and surgery was completed uneventfully. As the anesthetic lasted over 2 hours, the neuromuscular paralysis from the rocuronium was allowed to dissipate spontaneously. The trachea was extubated after resumption of spontaneous respirations, and the patient was transferred to the recovery room. The patient gave no indication of having pain at the time of emergence from general anesthesia or in the first 2 hours in the recovery room (Verbal Pain
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Score 3-4/10; 0 ⫽ no pain, 10 ⫽ worst pain). Assessment of the level of hypoesthesia to ice while the patient was comfortable in the recovery room suggested a functional epidural catheter (cephalad level of T10). The epidural catheter was promptly connected to an Abbott Pain Manager II patientcontrolled analgesia pump (Abbott Laboratories, North Chicago, IL) containing 0.1% bupivacaine and 5 g/mL fentanyl (continuous infusion 7 mL/h, bolus 4 mL, lockout interval 12 minutes). Two hours after admission to the recovery room the patient began to complain of increasing pain. Another 6 mL 0.25% bupivacaine was administered via the catheter. The patient’s pain decreased, but remained substantial (Verbal Pain Rating decreased from 8 to 6), and there was little evidence of sensory block above the T10 level (ice and pin prick assessments). Subsequently, a T10 epidural catheter (Arrow FlexTip Plus Catheter, Product #JH-05500; Arrow International, Reading, PA) was placed with the patient in the left lateral decubitus position via a left paramedian approach with a 17-gauge Tuohy needle and a LOR to air technique. A confirmatory (Tsui) test13 again suggested proper placement of the catheter in the epidural space at the T10 level (bilateral motor response at approximately the T10 level at 5.0 mamp with a Digistim II nerve stimulator (Neurotechnology, Houston, TX, pulse width 200 sec, 1 Hz). A test dose of 5 mL 0.25% bupivacaine resulted in prompt and complete relief of the patient’s pain. However, the level of hypoesthesia to ice did not extend cephalad to the T10 level. The new catheter was attached to the patient-controlled epidural analgesia (PCEA) device. Approximately 1 hour later the patient complained of increasing discomfort again. An acute pain service (APS) physician was called to assess the situation. Again, there was no evidence of any sensory block, and there was no response to a bolus of 8 mL 1% lidocaine. A thorough examination of the patient did not suggest any cause for pain other that a malfunctioning epidural catheter. The patient was told that this was very unusual, but it was likely that both epidural catheters had somehow migrated out of the epidural space. Alternative analgesia was discussed (i.e., intravenous patient-controlled analgesia [IVPCA]), but the patient elected to have another epidural catheter placed. A third epidural catheter (Portex; Sims Portex) was placed in the left lateral decubitus position via a midline approach with a 17-gauge Tuohy needle and a LOR to air technique at the T8-9 level. This catheter was tested with 10 mL 0.5% bupivacaine. Analgesia was re-established. However, the level of
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Fig 1. MRI and illustration of the thoracic spine and epidural space. (Inset) a, Abnormal amount of epidural fat; b, spinal cord; c, subcutaneous fat; d, Cerebrospinal fluid; e, normal epidural space and fat; f, dura; g, lamina of vertebra; h, Ligamentum flavum. (A) T1W1 (400/8/3) (repetition time/echo time/number of excitations). Sagittal T1-weighted imaging of a normal thoracic spine. (B) T1W1 (400/8/3). Sagittal T1-weighted imaging of the thoracic spine of the patient. An excessive amount of epidural fat is noted posteriorly in the central canal extending from T3 to T9. This epidural fat does not compress the thecal sac or spinal cord and has a high intensity signal (white) similar to the subcutaneous fat. The adjacent cerebrospinal fluid (CSF) has a low intensity signal (black), while the spinal cord has an intermediate intensity signal (dark grey).
hypoesthesia to ice was restricted to a narrow bilateral band from T7-T9. Analgesia failed 2 hours later. The epidural catheter was removed and the patient’s pain was subsequently managed with intravenous patient-controlled morphine (bolus dose 1.5 mg, lockout 6 minutes, no maximum) (Lifecare 4100 PCA Plus Infusor; Abbott Laboratories). A more detailed history acquired the next day revealed that several months ago she had been treated with oral prednisone for a presumptive diagnosis of Crohn’s disease. The patient agreed to a magnetic resonance imaging (MRI) scan of her spine. A neurosurgical consultation was acquired to facilitate the acquisition and interpretation of the MRI scan and to provide advice if any abnormality was found. The MRI scan
revealed extensive epidural fat dorsal to the spinal cord from C5-C7 and from T3-T9 (Fig 1A through D). A diagnosis of epidural lipomatosis was established. There was no evidence of spinal cord compression. As the patient was currently asymptomatic, she was discharged home with instructions to see her family physician regularly for reassessment regarding the diagnosis of epidural lipomatosis. A pathologic examination of the tissue removed at the time of surgery revealed diaphragm-like strictures in the resected specimen of small bowel. These were interpreted as likely secondary to nonsteroidal antiinflammatory drug treatment. There was no evidence of Crohn’s disease. The patient was discharged home with instructions to see her surgeon in 3 weeks time.
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Fig 1. (Cont’d) (C) T2W1 (3000/98.7/4). On sagittal T2-weighted imaging of the same region of thoracic spine, the excessive amount of epidural fat continues to have a high intensity signal (white) similar to the subcutaneous fat. The CSF has a high intensity signal (light grey), and the spinal cord has a low intensity signal (dark grey). (D) T1W1 (256/160/3). On axial T1-weighted imaging at the level of T6, the excessive amount of epidural fat occupies the posterior half of the central canal without spinal cord or thecal sac compression.
Discussion Inadequate epidural analgesia is a problem faced regularly on any acute pain service. The differential diagnosis can be lengthy, and troubleshooting can be labor-intensive (Table 1). Despite this, we believe that all 3 epidural catheters in our patient were placed properly. The Tsui test uses an electric current to stimulate motor nerve rootlets in the epidural space.13,14 The sensitivity and specificity of the Tsui test for identification of the epidural space are 100% and 91.6%, respectively.13 The first 2 catheters produced evidence of extensive bilateral segmental conduction block to ice below T10 that was associated, temporarily, with good to excellent
pain relief (e.g., total, but temporary, pain relief after 5 mL 0.25% bupivacaine injected via the second catheter). The third catheter (T8-9) produced a very restricted segmental area (T7-9) of hypoesthesia to ice after 10 mL 0.5% bupivacaine that only temporarily relieved the patient’s pain (⬍2 hours). Subsequent injections of local anesthetic via all 3 catheters failed to reproduce analgesia. Large volumes of local anesthetic (6 to 10 mL) failed to extend evidence of conduction block higher than T10 with the first 2 catheters and failed to extend evidence of conduction block outside a narrow T7-9 segmental band with the third catheter. These observations led us to perform a MRI scan to look for a space-occupying lesion.
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Regional Anesthesia and Pain Medicine Vol. 27 No. 5 September–October 2002 Table 1. Epidural Analgesia: Trouble-shooting Failed Analgesia Cause
Management Options
Catheter is not in the epidural space Subcutaneous5 Paraspinal muscle/fat5 Paravertebral7,22 Interpleural8 Intravascular23,24 Catheter is in the epidural space, but is not providing adequate analgesia Catheter in anterior epidural space1,27 Catheter in lateral epidural space2 Catheter or solution migrates out intervertebral foramen2,14,28-31 Catheter not placed at appropriate level (i.e., inadequate analgesia and/or excessive side effects precluding continued use)14,31 Other distribution problem (e.g., extensive dermatomal demand [e.g., thoracoabdominal T4-L1 incision], space occupying lesion [tumor,32 mucopolysaccharide,4 fat2], plica mediana dorsalis,3,33,34 fibrous adhesions,35 epidural air,36,37 diffusion barrier4,38 Pharmacokinetic55-57 problem (e.g., enhanced drug absorption/metabolism) Pharmacodynamic39,55-57 problem (e.g., receptor-mediated tolerance, drug interaction) Neural processing problem36,40,54,57 (e.g., conduction block insufficient to “handle” “intensity” of neural traffic) Central neurogenic pain41 Other source of pain remote from surgical site Technical problem with equipment (obstructed catheter9 [kink,10 connector obstruction or disconnection,9 blood clot, inflammation,38 manufacturing defect42]; pump failure43 [electronic, air-in-the-line, mechanical]) Human error44 (programming error, drug error) Leaking epidural site45,46
Prevent migration from epidural space by ensuring catheter is inserted an optimal distance (4-6 cm)25 and is well secured26 Tsui test13 and epidural local anesthetic test dose to confirm placement and to try to reestablish analgesia Replace catheter or choose alternative analgesic regimen
Tsui test13/local anesthetic test dose may help identify where catheter is Reposition* catheter by pulling it back24,47,48 Change programming parameters (e.g., increase bolus11 dose and/or infusion rate58) Change selection of drug/s (e.g., select opioid only [i.e., less dependence of catheter position49,50]) Replace catheter Identify and address other source/s of pain Identify and address technical problems and human error Apply pressure dressing over epidural exit site (personal observation) or consider crazy glue seal45 Consider dual epidural catheter for extensive dermatome requirements51,52 Consider multimodal53 or hybrid† analgesic regimen Consider epidurogram or MRI Consider consultation for management of chronic pain of central origin
*Controversial issue (pro and con). †Hybrid technique ⬅ A combination of two or more major analgesic interventions (e.g., intercostal nerve block and epidural catheter).
Epidural lipomatosis is a rare disorder.15 However, the experience of some investigators suggests that it may be underdiagnosed.16 It is characterized by an excessive amount of nonencapsulated fat in the epidural space. Excess epidural fat generally occurs in the posterior epidural space and can act as a space-occupying lesion resulting in variable compression of the spinal cord, dural sac, or nerve roots.15 Alternatively, asymmetric deposition of excess epidural fat can cause spinal cord pathology via rotational distortion.17 Patients typically present with back pain or variable symptoms of spinal cord or nerve root compression.15 Men are affected more often than women.15 The pathogenesis of the disorder is unknown.15 It has been reported to occur spontaneously18 or in association with steroid use,
endocrinopathies, or obesity,15,16,18 but may occur in patients without these risk factors.19 MRI is the diagnostic technique of choice.15 Treatment depends on presentation.15 Medical management15 may include strategies to induce weight loss, the elimination of medications thought to have a causal relationship with the development of epidural lipomatosis (e.g., steroids, ritonavir20), and the management of associated endocrinopathies (e.g., Cushing’s syndrome). Surgical management may involve multiple level laminectomies and decompression16,18 or endoscopic suction decompression via small bilateral laminotomies.21 We hypothesize in our patient that the extensive accumulation of epidural fat adversely affected the distribution of the drugs we administered in the
Failed Epidural Analgesia and Epidural Lipomatosis
epidural space (bupivacaine and fentanyl). The fat may have prevented symmetrical distribution of the drugs in the thoracic epidural space. Alternatively, the fat may have acted as a “depot” for the lipid soluble bupivacaine and fentanyl, effectively sequestering the analgesic agents. This could explain the very limited segmental conduction blocks obtained with concentrated solutions of bupivacaine and lidocaine. We hope that this case report stimulates other clinicians to consider such an association and encourages investigators with the appropriate tools to establish an animal model to elucidate the mechanisms by which excess epidural fat may impair epidural analgesia. In conclusion, repeated failure of epidural analgesia together with restricted segmental conduction block after the administration of large volumes of local anesthetic should prompt consideration of epidural lipomatosis. After more common causes of failed epidural analgesia have been ruled out, MRI should be considered.
Acknowledgment We thank Helen Schroeder for her assistance in preparation of this manuscript.
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