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Anesth Analg 2002;95:441-443 © 2002 International Anesthesia Research Society
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Abstract |
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 Top Abstract IntroductionCase ReportDiscussionReferences |
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IMPLICATIONS:A single shot spinal anesthetic is not practical in a patient with a lumboperitoneal shunt. Neuraxial block and a blood patch (if necessary) may be performed in a patient on enoxaparin therapy if current guidelines for managing patients on anticoagulant therapy are followed.
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Introduction |
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TopAbstractIntroductionCase ReportDiscussionReferences |
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A lumboperitoneal (LP) shunt is inserted to manage pseudotumor cerebri (1). In this report, we describe our experience with an epidural catheter that was accidentally inserted into the intrathecal space in a patient with an LP shunt.
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Case Report |
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TopAbstractIntroductionCase ReportDiscussionReferences |
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A 25-year-old primigravida woman was admitted to the labor and delivery suite at 36 wk gestation, in labor. Her medical history included intracranial transverse sinus thrombosis in 1997 complicated by pseudotumor cerebri with increased intracranial pressure (ICP) and optic nerve dysfunction. This was initially treated with serial lumbar punctures and finally with an indwelling LP shunt (Integra Heyer-Schulte, Plainsboro, NJ). Current medications included enoxaparin 40 mg twice a day. A neurology consultation obtained a month before admission was completely unremarkable, but the neurologist advised against any active bearing-down efforts as a precaution against possible increase of ICP. The obstetricians planned to shorten the second stage by delivering the baby with forceps. Physical findings included: obesity (height 167.5 cm, weight 138 kg, and body mass index 47.5 kg/m2), a Mallampati Class IV airway, a small mouth opening, and a thyro-mental distance <2 cm. Her white blood cell count was 15.7 K/µL, hemoglobin was 14.3 g/dL, and platelets were 192 K/µL. A 4-cm scar was visible in the lumbar area.
Because the LP insertion had been done out of state, we could not obtain the patient’s previous medical records in time. With two paper clips taped at the upper and lower ends of the scar serving as markers, a radiograph of her lumbosacral spine showed the exact location of the shunt at L2-3 (Fig. 1). Enoxaparin had been discontinued 17 h before the placement of the epidural catheter.
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The patient requested analgesia at 6-cm cervical dilation. The epidural space was identified at the L1-2 level with a 17G Hustead needle and a catheter was inserted 4 cm into the epidural space. No cerebrospinal fluid (CSF) or blood was aspirated through the catheter. A test dose (3 mL of 1.5% lidocaine with 1:200,000 epinephrine) was positive for intrathecal placement of the catheter, and resulted in a dense block below T5 dermatomal level. A transient decrease of her blood pressure from 120/70 to 90/50 mm Hg responded to an IV fluid bolus and 20 mg of ephedrine. The patient progressed to complete dilation and the baby was delivered with low forceps within the next 20 min. Neonatal Apgar scores were 9/9. The patient sustained a third degree perineal tear during delivery.
At this time, the patient’s block had worn off completely. The block was reestablished for repair of the tear with 10 mg of lidocaine. The repair took 80 min, and each 10-mg dose of lidocaine produced a profound T5 motor block lasting 12–15 min, with complete resolution within 15 min. A total of 50 mg of lidocaine was needed. Cefazolin 2 g was given IV to prevent any secondary infection of both the surgical site and the LP shunt. At the end of the repair, the neuraxial block had dissipated and the catheter was removed.
The patient remained stable and was restarted on enoxaparin 24 h after delivery. She complained of postural headache the next morning. The headache was similar to her previous postdural puncture headaches (PDPH) after multiple lumbar punctures for the treatment of pseudomotor cerebri. The patient opted for conservative management of her PDPH with fluids and bedrest. She was discharged from the hospital 48 h later. However, she called us for worsening headache 5 days later. She was instructed to stop enoxaparin and an epidural blood patch was performed 24 h later, at the L1-2 level. Within 30 min, her headache had improved and she was discharged without further complications. She was asked to call the anesthesia department if she developed backache, fever, lower-extremity symptoms, or bladder/bowel disturbances.
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Discussion |
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TopAbstractIntroductionCase ReportDiscussionReferences |
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The use of epidural anesthesia for labor in a patient with an LP shunt has been described previously (2,3). Our case is unique in that it demonstrates the evanescent effects of intrathecal drugs, which we believe are caused by rapid removal of the drugs via the shunt. In addition, this is also the first case report of the efficacy and safety of a blood patch in patients receiving enoxaparin therapy. We believed the catheter was intrathecal, based on the response to the test dose and the subsequent development of PDPH.
Previous authors (2–4) have suggested that preblock radiograph studies were unnecessary to establish the position of the shunt. However, we did not have timely access to her medical records and the spine radiographs (with markers) helped us to identify the exact location of the shunt, thus avoiding possible disruption of the shunt with the epidural needle. A prelabor anesthesia consultation would have allowed us to obtain the patient’s previous records and may have obviated the need for radiographic studies during labor.
The epidural block was placed 17 hours after discontinuing her enoxaparin, well after the 10–12 hour wait recommended for such patients (5). When the epidural blood patch was administered, enoxaparin had been discontinued 24 hours prior. This is the first report of a blood patch in a patient receiving enoxaparin.
We believe this is the first case of spinal analgesia, albeit unintentional, in a patient with a functioning LP shunt. The pattern of quick offset of the block recurred repeatedly with each aliquot of lidocaine. Because lidocaine when used for spinal anesthesia has a duration of action of 30–90 minutes (6), it is likely that the rapid offset of local anesthetic action was caused by the washout of the medication into the peritoneal cavity via the LP shunt.
Accidental dural tap is one of the risks of epidural analgesia but does not carry a risk of cerebellar herniation in these patients: they routinely undergo serial lumbar punctures for decompression (7). Although epidural injection of local anesthetic may also increase ICP (8), this risk was minimized in this patient because of the presence of a functioning shunt. In our opinion, the advantages of an epidural anesthetic far outweighed the disadvantages in view of the potential risks associated with general anesthesia in this case. These included failed intubation, aspiration, and increased ICP. Abouleish et al. (7) have suggested the use of general anesthesia for patients with LP shunts. We believe this may not be the safest anesthetic technique in all such patients. Pseudotumor cerebri has been closely linked to morbid obesity (9). Both morbid obesity as well as general anesthesia have been implicated more often than regional anesthesia in causing maternal deaths (10,11).
An additional risk of epidural placement is the possible infection of the shunt. We observed our usual sterile precautions both during the placement of the catheter as well as during the blood patch, which includes wearing masks during the procedure (12). A single dose of a broad-spectrum antibiotic is the standard antibiotic prophylaxis used for obstetrical surgical procedures at our institution. Others (4) have used single doses of vancomycin plus gentamicin with similar success in preventing infection.
Most shunts have a diameter of approximately 1 mm and the clearance flow rates through the shunts exceed CSF production (13). The reason why patients with an LP shunt do not develop a PDPH could be the presence of an antisiphon valve in the shunt that prevents excessive drainage of CSF, especially in the vertical position (14). The CSF production and drainage may then reach a dynamic equilibrium, preventing PDPH. A wet tap with an epidural needle upsets this equilibrium resulting in a PDPH. The epidural blood patch effectively stops the PDPH in these patients, perhaps by stopping the CSF leak from the dural hole.
In summary, based on our experience in a pregnant patient with an LP shunt, we recommend that these patients should be seen in a prelabor consultation by a team that includes anesthesiologists. In absence of such a consultation, we recommend that an epidural technique be used after radiologic location of the shunt. Patients with an LP shunt can develop a PDPH that responds to an epidural blood patch. A single shot spinal anesthetic may not be suitable because of the unpredictable duration of action.
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References |
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TopAbstractIntroductionCase ReportDiscussionReferences |
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- Vander-Ark GD, Kempe LG, Smith DR. Pseudotumor cerebri treated with lumbar-peritoneal shunt. JAMA 1971; 217: 1832–4.
[Abstract/Free Full Text] - Bedard JM, Richardson MG, Wissler RN. Epidural anesthesia in a parturient with a lumboperitoneal shunt. Anesthesiology 1999; 90: 621–3. [Web of Science][Medline]
- Kim K, Orbegozo M. Epidural anesthesia for cesarean section in a parturient with pseudotumor cerebri and lumboperitoneal shunt. J Clin Anesth 2000; 12: 213–5. [Web of Science][Medline]
- Tarshis J, Zuckerman JE, Katz NP, et al. Labour pain management in a parturient with an implanted intrathecal pump. Can J Anaesth 1997; 44: 1278–81. [Web of Science][Medline]
- Horlocker TT, Wedel DJ. Neuraxial block and low molecular weight heparin: balancing perioperative analgesia and thromboprophylaxis. Reg Anesth Pain Med 1998; 23: 166–77.
- Covino BG, Vassalo HG. Local anesthetics: mechanisms of action and clinical use. New York: Grune & Statton, 1976.
- Abouleish E, Ali V, Tang RA. Benign intracranial hypertension and anesthesia for cesarean section. Anesthesiology 1985; 63: 705–7. [Web of Science][Medline]
- Hilt H, Gramm HJ, Link J. Changes in intracranial pressure associated with extradural anaesthesia. Br J Anaesth 1986; 58: 676–80.
[Abstract/Free Full Text] - Burgett RA, Purvin VA, Kawasaki A. Lumboperitoneal shunting for pseudotumor cerebri. Neurology 1997; 49: 734–9.
[Abstract/Free Full Text] - Endler GC. The risk of anesthesia in obese parturients. J Perinatol 1990; 10: 175–9. [Medline]
- Endler GC, Mariona FG, Sokol RJ, Stevenson LB. Anesthesia-related maternal mortality in Michigan, 1972 to 1984. Am J Obstet Gynecol 1988; 159: 187–93. [Web of Science][Medline]
- Tsen LC. The mask avenger? [letter] Anesth Analg 2001; 92: 279.
[Free Full Text] - Fox JL, McCullough DC, Green RC. Cerebrospinal fluid shunts: an experimental comparison of flow rates and pressure values in various commercial systems. J Neurosurg 1972; 37: 700–5. [Web of Science][Medline]
- Post EM. Shunt systems. In: Wilkins RH, Rengachary SS, eds. Neurosurgery. New York: McGraw-Hill, 1996: 3645–53.
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