- Email: [email protected]
Caesarean section in a parturient with a spinal cord stimulator
114
Caesarean section with spinal cord stimulator
tent injection into the subdural space; a space that may be less compliant than the epidural space. In summary, we report the subdural placement of an intended epidural catheter for labor analgesia that presented with back and neck pain on injection of medication and inadequate analgesia. The Tsui test did not detect subdural placement of the catheter; its localization was confirmed only by contrast radiology. Subdural catheters remain poorly understood, and continue to challenge the clinician. We recommend that epidural catheters associated with abnormal local anesthetic spread and/or pain on injection (sometimes far from the insertion point, such as inter-scapular), should be replaced.
References 1. Tsui BCH, Gupta S, Emery D, Finucane B. Detection of subdural placement of epidural catheter using nerve stimulation. Can J Anesth 2000;47:471–3.
2. Collier CB. Accidental subdural injection during attempted lumbar epidural block may present as a failed or inadequate block: radiographic evidence. Reg Anesth Pain Med 2004; 29:45–51. 3. Lubenow T, Keh-Wong E, Kristof K, Ivankovich O, Ivankovich A. Inadvertent subdural injection: a complication of an epidural block. Anesth Analg 1988;67:175–9. 4. Wills JW. Rapid onset of massive subdural anesthesia. Reg Anesth Pain Med 2005;30:299–302. 5. van der Maaten JM, van Kleef JW. Failure of anesthesia after accidental subdural catheter placement. Acta Anaesthesiol Scand 1992;36:707–9. 6. Mocan M, Zdravko G, Klopfenstein CE, Forster A. Accidental catheterization of the subdural space. a complication of continuous spinal anesthesia and continuous peridural anesthesia. Can J Anesth 1989;36:708–12. 7. Tsui BCH, Finucane B. Epidural stimulator catheter. Techniques in Regional Anesthesia and Pain Management 2002;6:150–4. 8. Lena P, Martin R. Subdural placement of an epidural catheter detected by nerve stimulation. Can J Anesth 2005;52:618–21. 9. Ross V, Bogard T, Doty W, Lee S, Pan P. What is pain with epidural injection/infusion (PWEI)? Anesthesiology 2007;107: A1780. 10. Spiegel J. Case series: neck pain associated with PCEA for labor analgesia. Anesth Analg 2008;106:A-220.
0959-289X/$ - see front matter c 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijoa.2009.07.008
Caesarean section in a parturient with a spinal cord stimulator D. Sommerfield, P. Hu, D. O’Keeffe, K. McKeatinga Department of Anaesthesia, National Maternity Hospital and aDepartment of Pain Medicine, St. Vincent’s University Hospital, Dublin, Ireland ABSTRACT A 35-year-old G2P1 parturient at 32 weeks of gestation with an implanted spinal cord stimulator was admitted for urgent caesarean section. Spinal anaesthesia was performed below the spinal cord stimulator leads at the L4-5 level, and a healthy female infant was delivered. A basic description of the technology and resulting implications for the parturient are discussed. c 2009 Elsevier Ltd. All rights reserved.
Keywords: Spinal cord stimulator; Caesarean section; Spinal
Introduction Spinal cord stimulation is increasingly used to manage chronic pain syndromes,1,2 including those associated with chronic back and leg pain,3,4 complex regional pain syndrome, refractory angina pectoris and peripheral vascular disease.1,5 With an annual sales growth rate projected to increase 20% by 2012,6 spinal cord stimulators (SCS) are likely to be used more frequently in parAccepted August 2009 Correspondence to: Dr. D. Sommerfield, c/o Dr. K. McKeating, Dept. of Anaesthesia, National Maternity Hospital, Holles Street, Dublin 2, Ireland. Tel.: 353-1-637 3100. E-mail address: dsommerfi[email protected]
turients. We discuss the management of anaesthesia for urgent caesarean section in an patient with a SCS.
Case report A 35-year-old G2P1 parturient at 32 weeks of gestation was admitted with intrauterine growth restriction (IUGR) and absent placental end diasystolic flow, for urgent delivery. The IUGR was initially confirmed sonographically at 29 weeks. Her first pregnancy five years earlier resulted in a full term normal vaginal delivery. The patient’s history was significant for poorly controlled hypertension, depression, and longstanding lumbosacral pain, which worsened during her first
D. Sommerfield et al.
115 MN, USA) was inserted. Two years later, because of lead migration, the SCS was replaced with a three-lead device (one OctrodeÒ, 8-electrodes and two QuattrodeÒ, 4-electrodes; Advanced Neuromodulation Systems Inc., Plano, TX, USA). The leads were inserted at L2-3 and located at T8. Lead extensions and strain relieving loops were placed below the device, but above the superior aspect of the L4 vertebra. The lead extensions were tunnelled subcutaneously to an implanted pulse generator (IPG) on the left upper buttock (Fig. 1). During pregnancy the patient received bisoprolol 10 mg, oral morphine 40 mg, diazepam 15 mg and tramadol 400 mg daily. She smoked 20 cigarettes per day and required assistance with household work. On admission, the patient’s blood pressure was 160/90 mmHg. Examination of her airway revealed poor dentition, loose teeth, porcelain crowns and limited head extension. She had a Mallampati score of III and an omentohyoid distance of 6 cm. Neuromuscular and skeletal examination revealed scarring from previous SCS surgery, palpable lead extensions and normal lower limb sensation and motor function. Lumbar radiographs taken during SCS insertion were reviewed. Laboratory investigations were within normal limits. Following a multidisciplinary discussion, a caesarean delivery under spinal anaesthesia was planned. In the operating suite with the patient seated and the SCS off, the L4-5 interspace was confirmed by ultrasound. A 25-gauge Whitacre needle passed without difficulty and hyperbaric bupivacaine 11 mg and fentanyl 25 lg were injected and produced anaesthesia to T3 bilaterally. The obstetrician was aware of the position of the IPG and leads and used only short bursts of bipolar diathermy. A healthy preterm neonate was delivered and co-amoxiclav 1.2 g was given for infection prophylaxis. After recovery from anaesthesia and return of normal motor function, an Advanced Neuromodalation Systems (ANS) technician confirmed that the SCS was intact and reactivated it. Morphine by patientcontrolled analgesia (PCA) and oral medications were resumed at 6 h. Oral morphine requirements were titrated to 60 mg daily, and then adjusted by her pain physician over the following months. The patient had electively decided not to breastfeed.
Fig. 1 Radiograph taken intra-operatively during implantation of the second spinal cord stimulator system. Note the three electrodes in the thoracic level that lead to internal extensions fixed in the lumbar area. The wires overlying the L4-5 interspace belong to the external testing system and would not be present once the system was fully implanted Also present are the previous systems extensions and implantable pulse generator (IPG).
pregnancy. Two years after her initial pregnancy, a twolead, eight-electrode SCS (Medtronic Inc., Minneapolis,
Discussion Management of patients with chronic pain syndromes during pregnancy can be challenging, particularly in the presence of an SCS. A good outcome requires a multidisciplinary team approach, including obstetrics, neonatology, pain medicine and anaesthesia, as was used from an early stage in our patient. SCS modifies the perception of neuropathic and ischaemic pain by electrically stimulating the dorsal
116 columns of the spinal cord. The aim is to elicit paraesthesiae in the region to replace the reported pain. Postulated mechanisms of action include activating descending inhibitory pain pathways and modulating the autonomic nervous system. Neurotransmitters and neuropeptides are modified at both segmental and supraspinal levels.7–10 SCS systems consist of electrode leads and extensions, an IPG and an external programmer.11 Percutaneous and paddle leads are presently in use with cylindrical and flexible percutaneous leads, similar to an epidural catheter. They are inserted into the epidural space via a 14-gauge Tuohy needle with the aid of fluoroscopy, typically with the patient in the prone position under light sedation to allow patient feedback on location of paraesthesiae. By contrast, paddle leads are flat and wide, and are surgically implanted during laminectomy under general anaesthesia. Extensions from the percutaneous or paddle leads are tunnelled subcutaneously to an IPG, which delivers frequency-optimised electrical pulses with amplitude adjusted by a physician programmer and controlled by the patient. Two parturients with upper limb complex regional pain syndrome with implanted cervical SCS have been described.12,13 In the first case, percutaneous electrodes placed at C2-3 allowed pain medication to be discontinued before conception; the patient conceived and delivered a full term infant by normal vaginal delivery with the stimulator remaining on throughout labour. In the second case, paddle-type stimulator electrodes had been placed at the C7-T1 interspace. Subcutaneous extension wires were placed paraspinally from the cervical region to a buttock IPG. Epidural analgesia at the L2-3 interspace proved satisfactory for labour. The SCS was left on throughout labour, with no interference or unwanted effects. There is little guidance available relating to the perioperative anaesthetic management of patients with spinal cord stimulators, but experience with deep brain stimulators, which use a similar technology, may be relevant.14–17 Artefacts on electrocardiography (ECG) have been noted during SCS, deep brain stimulation and transcutaneous nerve simulation.18–20 Deactivating the IPG before ECG monitoring will avoid this interference. In addition, as with implantable cardiac pacemakers, the use of bipolar diathermy, in short bursts, is advised.21,22 Surgical diathermy or electrocautery can damage the lead insulation, cause temporary suppression of neurostimulator output and reprogramming of the neurostimulator.14,23 Energy from diathermy can be conducted through the implanted system and heat implanted electrodes or extensions, or alter the stimulation thresholds. These problems can arise whether the system is on or off. Monopolar diathermy, where current travels from the instrument tip through the body to the ground plate, should be avoided when possible in the presence of SCS, because painful electrical shocks have been reported;
Caesarean section with spinal cord stimulator
Box 1 Summary of management of an obstetric patient with a spinal cord stimulator
1. Early referral to obstetric anaesthesia service a. Document pain history and medication b. Document back anatomy and lower limb neurology c. Discuss small risk of migration of lead or IPG during pregnancy and labour and potential damage or infection of system with any intervention 2. Consultation with patient’s pain team a. Obtain advice on pain medication through pregnancy b. Establish indication for SCS, lead type, and manufacturer c. Locate lead placement, extensions and implanted pulse generator d. Obtain previous radiographs to assess anatomy and hardware 3. Multidisciplinary meeting to plan labour and delivery management a. Detail labour pain management strategy, especially opioids b. Discuss advisability of neuraxial techniques c. Inform paediatricians if there is risk of neonatal withdrawal 4. If caesarean section is required a. Turn SCS amplitude to zero and turn off stimulator before surgery b. Use bipolar electrocautery c. If unipolar diathermy, position the ground plate to avoid passing current near the system d. Use short, intermittent, and irregular bursts of electrocautery at the lowest feasible energy levels e. Provide standard surgical prophylactic antibiotics 5. Postpartum care a. Check programming of SCS, preferably with manufacturer’s representative (Modified from ref 13,14,17,23.)
such shocks have not been described with the IPG unit turned off or when bipolar diathermy is used.15 If monopolar diathermy use is unavoidable, the ground plate should be positioned so that the stimulator components are outside the electrical pathway. Bipolar diathermy, where current flows only through the area of direct contact, appears to be safe if all components are distant from implanted equipment.17 Short bursts of diathermy
D. Sommerfield et al.
117
should be used and implanted devices turned off, to avoid reprogramming or damage to implanted devices, such as cardiac defibrillators.22,24 The IPG for SCS systems should therefore be programmed to zero (in case it is inadvertently turned on) and then turned off for the duration of a case.25 Postoperatively, a patient can easily check their SCS for clinical efficacy, but a more formal interrogation of the stimulator by a trained technician is better, as any device or programming issues can be identified. The steps are summarised in the Box 1. The critical decision for anaesthetic management of patients with SCS is the feasibility of providing neuraxial anaesthesia. Potential risks include damage to electrodes with the spinal or epidural needle, introducer, or catheter. Ultrasound examination may be useful. The British Pain Society does not recommend additional antibiotic prophylaxis for incidental procedures that may cause bacteraemia in SCS patients.17 Postoperative pain control in patients with complex regional pain syndrome should be discussed with the multidisciplinary team and the chronic pain physician, if possible. Maternal and neonatal withdrawal or abstinence symptoms should be monitored. In our case, fortunately, insertion of a spinal anaesthetic did not present any problems, but epidural catheter insertion could have dislodged or damaged the in-situ leads or extensions. Our patient had been stable on her pain regimen throughout pregnancy, and postoperatively her opioid requirements were met with PCA, then oral medication. Management of complex regional pain syndrome patients who are pregnant requires early multidisciplinary input. Implantable spinal cord stimulators are increasingly common, and anaesthetists should be familiar with their perioperative management to minimise adverse events.
References 1. Lee AW, Pilitsis JG. Spinal cord stimulation: indications and outcomes. Neurosurg Focus 2006;21:E3. 2. Falowski S, Celii A, Sharan A. Spinal cord stimulation: an update. Neurotherapeutics 2008;5:86–99. 3. Bernstein CA, Paicius RM, Barolat GB, Lempert-Cohen C. Spinal cord stimulation in conjunction with peripheral nerve field stimulation for the treatment of low back and leg pain. Neuromodulation 2008;11:116–23. 4. Taylor RS, Van Buyten JP, Buchser E. Spinal cord stimulation for chronic back and leg pain and failed back surgery syndrome: a systematic review and analysis of prognostic factors. Spine 2005;30:152–60. 5. Foletti A, Durrer A, Buchser E. Neurostimulation technology for the treatment of chronic pain: a focus on spinal cord stimulation. Expert Rev Med Devices 2007;4:201–14.
0959-289X/$ - see front matter c 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijoa.2009.08.006
6. McWilliams A. Microelectronic medical implants: products, technologies and opportunities. BCC Research 2007 Report HLC016C, 1-158. www.bccresearch.com/report/HLC016B.html Assessed 27-4-2009. 7. Meyerson BA, Cui JG, Yakhnitsa V et al. Modulation of spinal pain mechanisms by spinal cord stimulation and the potential role of adjuvant pharmacotherapy. Stereotact Funct Neurosurg 1997;68:129–40. 8. Meyerson BA, Linderoth B. Mechanisms of spinal cord stimulation in neuropathic pain. Neurol Res 2000;22:285–92. 9. Buchser E, Durrer A, Albrecht E. Spinal cord stimulation for the management of refractory angina pectoris. J Pain Symptom Manage 2006;31:S36–42. 10. Harke H, Gretenkort P, Ladleif HU, Rahman S. Spinal cord stimulation in sympathetically maintained complex regional pain syndrome type I with severe disability. A prospective clinical study. Eur J Pain 2005;9:363–73. 11. Bradley K. The technology: the anatomy of a spinal cord and nerve root stimulator: the lead and the power source. Pain Med 2006;7:S1:27–S34. 12. Segal R. Spinal cord stimulation, conception, pregnancy and labor: case report. Neuromodulation 1999;2:41–5. 13. Hanson JL, Goodman EJ. Labor epidural placement in a woman with a cervical spinal cord stimulator. Int J Obstet Anesth 2006;15:246–9. 14. Davies RG. Deep brain stimulators and anaesthesia. Br J Anaesth 2005;95:424. 15. Weaver J, Kim SJ, Lee MH, Torres A. Cutaneous electrosurgery in a patient with a deep brain stimulator. Dermatol Surg 1999;25:415–7. 16. Martinelli PT, Schulze KE, Nelson BR. Mohs micrographic surgery in a patient with a deep brain stimulator: a review of the literature on implantable electrical devices. Dermatol Surg 2004;30:1021–30. 17. Simpson K, Stannard C. Spinal cord stimulation for the management of pain: recommendations for best clinical practice, 2005. British Pain Society www.britishpainsociety.org/pub_professional.htm#spinalcord. Accessed 26-7-2008. 18. Constantoyannis C, Heilbron B, Honey CR. Electrocardiogram artifacts caused by deep brain stimulation. Can J Neurol Sci 2004;31:343–6. 19. Kimberley AP, Soni N, Williams TR. Transcutaneous nerve stimulation and the electrocardiograph. Anaesth Intensive Care 1987;15:358–9. 20. Siddiqui MA, Khan IA. Differential electrocardiographic artifact from implanted spinal cord stimulator. Int J Cardiol 2003;87:307–9. 21. Fleisher LA, Beckman JA, Brown KA et al. ACC/AHA 2007 Guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery. Circulation 2007;116:1971–96. 22. Madigan JD, Choudhri AF, Chen J et al. Surgical management of the patient with an implanted cardiac device: implications of electromagnetic interference. Ann Surg 1999;230:639–47. 23. Medtronic safety information for SCS. http://professional.medtronic.com/downloads/spinal-cord-stimulation/neurostimulationfor-chronic-pain-information-for-prescribers-m221351a_b_019.pdf. Accessed 7-7-2008. 24. Allen M. Pacemakers and implantable cardioverter defibrillators. Anaesthesia 2006;61:883–90. 25. Blomstedt P, Bejjani B-P, Jabre M, Koskinen L. Electromagnetic environmental influences on implanted deep brain stimulators. Neuromodulation 2006;9:262–9.
Caesarean section with spinal cord stimulator
tent injection into the subdural space; a space that may be less compliant than the epidural space. In summary, we report the subdural placement of an intended epidural catheter for labor analgesia that presented with back and neck pain on injection of medication and inadequate analgesia. The Tsui test did not detect subdural placement of the catheter; its localization was confirmed only by contrast radiology. Subdural catheters remain poorly understood, and continue to challenge the clinician. We recommend that epidural catheters associated with abnormal local anesthetic spread and/or pain on injection (sometimes far from the insertion point, such as inter-scapular), should be replaced.
References 1. Tsui BCH, Gupta S, Emery D, Finucane B. Detection of subdural placement of epidural catheter using nerve stimulation. Can J Anesth 2000;47:471–3.
2. Collier CB. Accidental subdural injection during attempted lumbar epidural block may present as a failed or inadequate block: radiographic evidence. Reg Anesth Pain Med 2004; 29:45–51. 3. Lubenow T, Keh-Wong E, Kristof K, Ivankovich O, Ivankovich A. Inadvertent subdural injection: a complication of an epidural block. Anesth Analg 1988;67:175–9. 4. Wills JW. Rapid onset of massive subdural anesthesia. Reg Anesth Pain Med 2005;30:299–302. 5. van der Maaten JM, van Kleef JW. Failure of anesthesia after accidental subdural catheter placement. Acta Anaesthesiol Scand 1992;36:707–9. 6. Mocan M, Zdravko G, Klopfenstein CE, Forster A. Accidental catheterization of the subdural space. a complication of continuous spinal anesthesia and continuous peridural anesthesia. Can J Anesth 1989;36:708–12. 7. Tsui BCH, Finucane B. Epidural stimulator catheter. Techniques in Regional Anesthesia and Pain Management 2002;6:150–4. 8. Lena P, Martin R. Subdural placement of an epidural catheter detected by nerve stimulation. Can J Anesth 2005;52:618–21. 9. Ross V, Bogard T, Doty W, Lee S, Pan P. What is pain with epidural injection/infusion (PWEI)? Anesthesiology 2007;107: A1780. 10. Spiegel J. Case series: neck pain associated with PCEA for labor analgesia. Anesth Analg 2008;106:A-220.
0959-289X/$ - see front matter c 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijoa.2009.07.008
Caesarean section in a parturient with a spinal cord stimulator D. Sommerfield, P. Hu, D. O’Keeffe, K. McKeatinga Department of Anaesthesia, National Maternity Hospital and aDepartment of Pain Medicine, St. Vincent’s University Hospital, Dublin, Ireland ABSTRACT A 35-year-old G2P1 parturient at 32 weeks of gestation with an implanted spinal cord stimulator was admitted for urgent caesarean section. Spinal anaesthesia was performed below the spinal cord stimulator leads at the L4-5 level, and a healthy female infant was delivered. A basic description of the technology and resulting implications for the parturient are discussed. c 2009 Elsevier Ltd. All rights reserved.
Keywords: Spinal cord stimulator; Caesarean section; Spinal
Introduction Spinal cord stimulation is increasingly used to manage chronic pain syndromes,1,2 including those associated with chronic back and leg pain,3,4 complex regional pain syndrome, refractory angina pectoris and peripheral vascular disease.1,5 With an annual sales growth rate projected to increase 20% by 2012,6 spinal cord stimulators (SCS) are likely to be used more frequently in parAccepted August 2009 Correspondence to: Dr. D. Sommerfield, c/o Dr. K. McKeating, Dept. of Anaesthesia, National Maternity Hospital, Holles Street, Dublin 2, Ireland. Tel.: 353-1-637 3100. E-mail address: dsommerfi[email protected]
turients. We discuss the management of anaesthesia for urgent caesarean section in an patient with a SCS.
Case report A 35-year-old G2P1 parturient at 32 weeks of gestation was admitted with intrauterine growth restriction (IUGR) and absent placental end diasystolic flow, for urgent delivery. The IUGR was initially confirmed sonographically at 29 weeks. Her first pregnancy five years earlier resulted in a full term normal vaginal delivery. The patient’s history was significant for poorly controlled hypertension, depression, and longstanding lumbosacral pain, which worsened during her first
D. Sommerfield et al.
115 MN, USA) was inserted. Two years later, because of lead migration, the SCS was replaced with a three-lead device (one OctrodeÒ, 8-electrodes and two QuattrodeÒ, 4-electrodes; Advanced Neuromodulation Systems Inc., Plano, TX, USA). The leads were inserted at L2-3 and located at T8. Lead extensions and strain relieving loops were placed below the device, but above the superior aspect of the L4 vertebra. The lead extensions were tunnelled subcutaneously to an implanted pulse generator (IPG) on the left upper buttock (Fig. 1). During pregnancy the patient received bisoprolol 10 mg, oral morphine 40 mg, diazepam 15 mg and tramadol 400 mg daily. She smoked 20 cigarettes per day and required assistance with household work. On admission, the patient’s blood pressure was 160/90 mmHg. Examination of her airway revealed poor dentition, loose teeth, porcelain crowns and limited head extension. She had a Mallampati score of III and an omentohyoid distance of 6 cm. Neuromuscular and skeletal examination revealed scarring from previous SCS surgery, palpable lead extensions and normal lower limb sensation and motor function. Lumbar radiographs taken during SCS insertion were reviewed. Laboratory investigations were within normal limits. Following a multidisciplinary discussion, a caesarean delivery under spinal anaesthesia was planned. In the operating suite with the patient seated and the SCS off, the L4-5 interspace was confirmed by ultrasound. A 25-gauge Whitacre needle passed without difficulty and hyperbaric bupivacaine 11 mg and fentanyl 25 lg were injected and produced anaesthesia to T3 bilaterally. The obstetrician was aware of the position of the IPG and leads and used only short bursts of bipolar diathermy. A healthy preterm neonate was delivered and co-amoxiclav 1.2 g was given for infection prophylaxis. After recovery from anaesthesia and return of normal motor function, an Advanced Neuromodalation Systems (ANS) technician confirmed that the SCS was intact and reactivated it. Morphine by patientcontrolled analgesia (PCA) and oral medications were resumed at 6 h. Oral morphine requirements were titrated to 60 mg daily, and then adjusted by her pain physician over the following months. The patient had electively decided not to breastfeed.
Fig. 1 Radiograph taken intra-operatively during implantation of the second spinal cord stimulator system. Note the three electrodes in the thoracic level that lead to internal extensions fixed in the lumbar area. The wires overlying the L4-5 interspace belong to the external testing system and would not be present once the system was fully implanted Also present are the previous systems extensions and implantable pulse generator (IPG).
pregnancy. Two years after her initial pregnancy, a twolead, eight-electrode SCS (Medtronic Inc., Minneapolis,
Discussion Management of patients with chronic pain syndromes during pregnancy can be challenging, particularly in the presence of an SCS. A good outcome requires a multidisciplinary team approach, including obstetrics, neonatology, pain medicine and anaesthesia, as was used from an early stage in our patient. SCS modifies the perception of neuropathic and ischaemic pain by electrically stimulating the dorsal
116 columns of the spinal cord. The aim is to elicit paraesthesiae in the region to replace the reported pain. Postulated mechanisms of action include activating descending inhibitory pain pathways and modulating the autonomic nervous system. Neurotransmitters and neuropeptides are modified at both segmental and supraspinal levels.7–10 SCS systems consist of electrode leads and extensions, an IPG and an external programmer.11 Percutaneous and paddle leads are presently in use with cylindrical and flexible percutaneous leads, similar to an epidural catheter. They are inserted into the epidural space via a 14-gauge Tuohy needle with the aid of fluoroscopy, typically with the patient in the prone position under light sedation to allow patient feedback on location of paraesthesiae. By contrast, paddle leads are flat and wide, and are surgically implanted during laminectomy under general anaesthesia. Extensions from the percutaneous or paddle leads are tunnelled subcutaneously to an IPG, which delivers frequency-optimised electrical pulses with amplitude adjusted by a physician programmer and controlled by the patient. Two parturients with upper limb complex regional pain syndrome with implanted cervical SCS have been described.12,13 In the first case, percutaneous electrodes placed at C2-3 allowed pain medication to be discontinued before conception; the patient conceived and delivered a full term infant by normal vaginal delivery with the stimulator remaining on throughout labour. In the second case, paddle-type stimulator electrodes had been placed at the C7-T1 interspace. Subcutaneous extension wires were placed paraspinally from the cervical region to a buttock IPG. Epidural analgesia at the L2-3 interspace proved satisfactory for labour. The SCS was left on throughout labour, with no interference or unwanted effects. There is little guidance available relating to the perioperative anaesthetic management of patients with spinal cord stimulators, but experience with deep brain stimulators, which use a similar technology, may be relevant.14–17 Artefacts on electrocardiography (ECG) have been noted during SCS, deep brain stimulation and transcutaneous nerve simulation.18–20 Deactivating the IPG before ECG monitoring will avoid this interference. In addition, as with implantable cardiac pacemakers, the use of bipolar diathermy, in short bursts, is advised.21,22 Surgical diathermy or electrocautery can damage the lead insulation, cause temporary suppression of neurostimulator output and reprogramming of the neurostimulator.14,23 Energy from diathermy can be conducted through the implanted system and heat implanted electrodes or extensions, or alter the stimulation thresholds. These problems can arise whether the system is on or off. Monopolar diathermy, where current travels from the instrument tip through the body to the ground plate, should be avoided when possible in the presence of SCS, because painful electrical shocks have been reported;
Caesarean section with spinal cord stimulator
Box 1 Summary of management of an obstetric patient with a spinal cord stimulator
1. Early referral to obstetric anaesthesia service a. Document pain history and medication b. Document back anatomy and lower limb neurology c. Discuss small risk of migration of lead or IPG during pregnancy and labour and potential damage or infection of system with any intervention 2. Consultation with patient’s pain team a. Obtain advice on pain medication through pregnancy b. Establish indication for SCS, lead type, and manufacturer c. Locate lead placement, extensions and implanted pulse generator d. Obtain previous radiographs to assess anatomy and hardware 3. Multidisciplinary meeting to plan labour and delivery management a. Detail labour pain management strategy, especially opioids b. Discuss advisability of neuraxial techniques c. Inform paediatricians if there is risk of neonatal withdrawal 4. If caesarean section is required a. Turn SCS amplitude to zero and turn off stimulator before surgery b. Use bipolar electrocautery c. If unipolar diathermy, position the ground plate to avoid passing current near the system d. Use short, intermittent, and irregular bursts of electrocautery at the lowest feasible energy levels e. Provide standard surgical prophylactic antibiotics 5. Postpartum care a. Check programming of SCS, preferably with manufacturer’s representative (Modified from ref 13,14,17,23.)
such shocks have not been described with the IPG unit turned off or when bipolar diathermy is used.15 If monopolar diathermy use is unavoidable, the ground plate should be positioned so that the stimulator components are outside the electrical pathway. Bipolar diathermy, where current flows only through the area of direct contact, appears to be safe if all components are distant from implanted equipment.17 Short bursts of diathermy
D. Sommerfield et al.
117
should be used and implanted devices turned off, to avoid reprogramming or damage to implanted devices, such as cardiac defibrillators.22,24 The IPG for SCS systems should therefore be programmed to zero (in case it is inadvertently turned on) and then turned off for the duration of a case.25 Postoperatively, a patient can easily check their SCS for clinical efficacy, but a more formal interrogation of the stimulator by a trained technician is better, as any device or programming issues can be identified. The steps are summarised in the Box 1. The critical decision for anaesthetic management of patients with SCS is the feasibility of providing neuraxial anaesthesia. Potential risks include damage to electrodes with the spinal or epidural needle, introducer, or catheter. Ultrasound examination may be useful. The British Pain Society does not recommend additional antibiotic prophylaxis for incidental procedures that may cause bacteraemia in SCS patients.17 Postoperative pain control in patients with complex regional pain syndrome should be discussed with the multidisciplinary team and the chronic pain physician, if possible. Maternal and neonatal withdrawal or abstinence symptoms should be monitored. In our case, fortunately, insertion of a spinal anaesthetic did not present any problems, but epidural catheter insertion could have dislodged or damaged the in-situ leads or extensions. Our patient had been stable on her pain regimen throughout pregnancy, and postoperatively her opioid requirements were met with PCA, then oral medication. Management of complex regional pain syndrome patients who are pregnant requires early multidisciplinary input. Implantable spinal cord stimulators are increasingly common, and anaesthetists should be familiar with their perioperative management to minimise adverse events.
References 1. Lee AW, Pilitsis JG. Spinal cord stimulation: indications and outcomes. Neurosurg Focus 2006;21:E3. 2. Falowski S, Celii A, Sharan A. Spinal cord stimulation: an update. Neurotherapeutics 2008;5:86–99. 3. Bernstein CA, Paicius RM, Barolat GB, Lempert-Cohen C. Spinal cord stimulation in conjunction with peripheral nerve field stimulation for the treatment of low back and leg pain. Neuromodulation 2008;11:116–23. 4. Taylor RS, Van Buyten JP, Buchser E. Spinal cord stimulation for chronic back and leg pain and failed back surgery syndrome: a systematic review and analysis of prognostic factors. Spine 2005;30:152–60. 5. Foletti A, Durrer A, Buchser E. Neurostimulation technology for the treatment of chronic pain: a focus on spinal cord stimulation. Expert Rev Med Devices 2007;4:201–14.
0959-289X/$ - see front matter c 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijoa.2009.08.006
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