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* From the Department of Anesthesiology, St. Vincent’s Infirmary-Doctor’s Hospital, Little Rock, Arkansas; and the
Department of General Anesthesiology, The Cleveland Clinic Foundation, Cleveland, Ohio, USA.
Address correspondence to: Dr. James A. Dolak, Department of General Anesthesiology, The Cleveland Clinic Foundation, 9500 Euclid Avenue, E-31, Cleveland, Ohio 44195, USA. Phone: 216-444-0224; Fax: 216-444-2294; E-mail: dolakj{at}ccf.org
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Clinical features: A 20-yr-old primigravida with a history of familial cardiomyopathy and AICD placement presented at 39 weeks gestational age for elective labour induction. Ultimately, the patient underwent a Cesarean section for a failed induction. Her AICD was deactivated during the peripartum period, although the pacing function remained active as she had an underlying heart rhythm of less than 34 beat·min–1. The patient had continuous electrocardiogram monitoring via an external defibrillating unit to which she remained connected by external defibrillator pads. Labour analgesia and surgical anesthesia were provided with a lumbar epidural dosed with varying concentrations of bupivacaine. This management resulted in an excellent maternal and fetal outcome.
Conclusions: Automatic implantable cardioverter-defibrillators are being utilized more frequently in the obstetric population, and appear compatible with good fetal outcomes. Experience with the anesthetic management of these patients is markedly limited – primarily involving reports of general anesthesia for Cesarean section. Epidural anesthesia, however, offers distinct advantages in this patient population including easy conversion from labour analgesia to surgical anesthesia, preservation of fetal-maternal hemodynamics, prevention of increases in plasma catecholamines due to labour or operative pain, and, finally, possible direct suppression of arrhythmias by pharmacologically-active plasma levels of local anesthetic.
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Early initiation of epidural anesthesia was recommended to provide excellent labour analgesia and prevent any pain-induced increases in circulating epinephrine4 which might precipitate a tachydysrhythmia. It was also felt that the plasma concentrations of local anesthetic achieved after epidural dosing might have an antiarrhythmic effect (vide infra). External defibrillator pads were applied, and a paced rhythm was noted on continuous electrocardiography. A defibrillator unit was placed at the patient’s bedside throughout the peripartum period. After a 750-mL iv bolus of lactated Ringer’s solution, the patient was turned to the left lateral decubitus position for placement of a lumbar (L3–L4) epidural catheter. A test dose of 3 mL of 0.25% bupivacaine was injected without any signs/symptoms of intrathecal or iv injection. Nine millilitres of bupivacaine 0.25% with fentanyl 50 µg were injected incrementally over 15 min – achieving a sensory level to the T10 dermatome, which was maintained by the continuous epidural infusion of bupivacaine 0.125% with fentanyl 2 µg·mL–1 at 10 mL·hr–1
Early the following morning a Cesarean section was planned secondary to a failed vacuum extraction for failure of descent. The patient, along with the external defibrillator, was brought to the operating room where 25 mL of bupivacaine 0.5% with fentanyl 50 µg were given epidurally in incremental doses to achieve a T5-sensory level. The electrocautery grounding pad was placed on the patient’s right thigh in an effort to minimize possible interference with the pacing function of the AICD. A low-transverse Cesarean section was performed resulting in delivery of a female infant with Apgar scores of 9 and 9 (at one and five minutes, respectively). At no time during surgery did electrocautery result in pacemaker malfunction. Patient-controlled epidural analgesia with 0.1% ropivacaine containing fentanyl 10 µg·mL–1 provided postoperative pain control. Her AICD was reactivated in the postpartum period. No dysrhythmias were observed during her hospital stay.
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Cardiac disease complicates approximately 1% of all pregnancies; however, women with arrhythmias comprise only a small portion of these cases.7 An increased incidence of supraventricular tachycardia, due either to accessory pathway-mediated (50%) or atrioventricular nodal reentrant mechanisms (46%), may be seen in pregnant women who are otherwise healthy.8 These same women may also experience episodes of ventricular tachycardia, which may be triggered by hemodynamic changes and autonomic nervous system alterations.7 Pregnancy in a patient with an AICD presents additional considerations for fetal safety. Recurrence of maternal ventricular tachycardia is the primary fetal risk as it results in maternal hypotension followed by placental hypoperfusion.3 Additionally, with subsequent cardioversion, the energy of the AICD shock could be shunted to the fetal heart with unpredictable effects. However, as the fetal heart has a high-fibrillation threshold, and the current reaching the uterus should be very small (as therapy from internal defibrillation is directed), it is unlikely that AICD discharges could cause life-threatening fetal arrhythmias.7 Fortunately, this prediction appears to be true. Natale et al. 7 discussed the fetal outcome in a series of 44 women with AICDs, 11 of whom experienced discharges while pregnant. In the shocked group, eight patients experienced one shock, two experienced five shocks, and one patient experienced 11 shocks. Birth outcomes included nine healthy infants, one case of neonatal hypoglycemia thought to result from antiarrhythmic therapy, and one stillbirth secondary to a cord accident (in which the fetus was known to be viable post-AICD discharge). However, due both to the unpredictable fetal risk from AICD firing during delivery, along with maternal, fetal, and surgical team risks of repetitive triggering secondary to electrocautery during Cesarean section, the device was inactivated and external defibrillator electrodes were applied for the duration of the peripartum interval.
Lumbar epidural analgesia was chosen to provide labour pain relief, as well as providing an opportune anesthetic technique in the event the patient required urgent Cesarean section. An Arrow Flex-Tip® catheter (Arrow International, Inc.; Reading, PA, USA) was used, as these catheters have been shown to have a reduced risk of intravascular placement.9 Epinephrine-containing solutions were avoided for testing epidural placement secondary to concerns about eliciting malignant tachyarrhythmias. Bupivacaine, perhaps a controversial choice in this patient with cardiomyopathy, was chosen to provide a slow onset block with a stable hemodynamic profile. It was felt that this was more important than the largely theoretical risk of bupivacaine-induced cardiotoxicity with a properly placed, tested, and dosed epidural catheter. Additionally, it is known that the epidural administration of local anesthetics (including bupivacaine) often results in pharmacologically-active levels of these drugs in the circulation.10 The levels of local anesthetic achieved in this patient’s serum, therefore, might be expected to suppress any inherent arrhythmogenicity. More specifically, it has been shown that administration of 0.25% bupivacaine epidurally to parturients in labour results in peak serum concentrations of approximately 2.4 µmol·L–1,11,12 whereas caudal administration of this drug to children results in serum concentrations of approximately 5 µmol·L–1.13 Furthermore, in a study involving 20 parturients randomized to receive either 0.5% bupivacaine or 2% lidocaine for elective Cesarean section (ten in each arm), serum concentrations of bupivacaine were found to range from 1.5 to 3.8 µmol·L–1 (mean 2.7 µmol·L–1),14 concentrations which are below those associated with clinical toxicity (completely absent at levels less than 4.9 µmol·L–1).5 When 2% lidocaine was utilized, potentially toxic serum concentrations of local anesthetic occurred in two subjects (31 µmol·L–1 and 41 µmol·L–1 respectively),14 which were markedly greater than the reputed toxic threshold of 13–21 µmol·L–1.15 While none of the patients receiving lidocaine for Cesarean section developed outward signs of clinical toxicity, this may have been simply a result of interpatient differences in sensitivity. Nevertheless, based upon the peak serum concentrations of bupivacaine and lidocaine achieved in the above study, along with consideration of the reported toxic serum concentrations of these drugs, bupivacaine would appear to have a larger margin of safety than lidocaine when administered through a proven epidural catheter. Finally, the concentrations of bupivacaine utilized in the previously mentioned studies are in the range that has been associated with antiarrhythmogenic effects in both an in vitro model of ischemia/reperfusion injury,16 and an in vivo postinfarction model of arrhythmia.17 As predicted based upon all of the above considerations, this technique provided a stable, controlled fetal-maternal hemodynamic environment throughout labour and during the ensuing Cesarean section.
Due to the complex interactions between maternal-fetal physiology and the operating room environment in the patient with an AICD, close coordination between the anesthesiologist, cardiologist, and obstetrician regarding peripartum management is of highest importance.
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Footnotes |
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Accepted for publication August 24, 2004. Revision accepted November 25, 2005.
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2 Olufolabi AJ, Charlton GA, Allen SA, Mettam IM, Roberts PR. Use of implantable cardioverter defibrillator and anti-arrhythmic agents in a parturient. Br J Anaesth 2002; 89: 652–5.
3 Isaacs JD, Mulholland DH, Hess LW, Allbert JR, Martin RW. Pregnancy in a woman with an automatic implantable cardioverter-defibrillator. A case report. J Reprod Med 1993; 36: 487–8.
4 Shnider SM, Abboud TK, Artal R, Henriksen EH, Stefani SJ, Levinson G. Maternal catecholamines decrease during labor after lumbar epidural anesthesia. Am J Obstet Gynecol 1983; 147: 13–5.[Medline]
5 Dubin AM, Batsford WP, Lewis RJ, Rosenfeld LE. Quality-of-life in patients receiving implantable cardioverter defibrillators at or before age 40. Pacing Clin Electrophysiol 1996; 19(11 Pt 1): 1555–9.[Medline]
6 Gallagher RD, McKinley S, Mangan B, Pelletier D, Squire J, Mitten-Lewis S. The impact of the implantable cardioverter defibrillator on quality of life. Am J Crit Care 1997; 6: 16–24.[Abstract]
7 Natale A, Davidson T, Geiger MJ, Newby K. Implantable cardioverter-defibrillators and pregnancy. A safe combination? Circulation 1997; 96: 2808–12.
8 Lee SH, Chen SA, Wu TJ, et al. Effects of pregnancy on first onset and symptoms of paroxysmal supraventricular tachycardia. Am J Cardiol 1995; 76: 675–8.[Medline]
9 Banwell BR, Morley-Forster P, Krause R. Decreased incidence of complications in parturients with the Arrow (Flex-Tip PlusTM) epidural catheter. Can J Anaesth 1998; 45: 370–2.
10 Greene NM, Brull SJ. Physiology of Spinal Anesthesia, 4th ed. Baltimore: Williams & Wilkins; 1993.
11 Denson DD, Knapp RM, Turner P, Thompson GA. Serum bupivacaine concentrations in term parturients following continuous epidural analgesia for labor and delivery. Ther Drug Monit 1984; 6: 393–8.[Medline]
12 Flynn RJ, McMurray TJ, Dwyer R, Moore J. Comparison of plasma bupivacaine concentrations during continuous extradural infusion for labour. Br J Anaesth 1988; 61: 382–4.
13 Eyres RL, Bishop W, Oppenheim RC, Brown TC. Plasma bupivacaine concentrations in children during caudal epidural analgesia. Anaesth Intensive Care 1983; 11: 20–2.[Medline]
14 Downing JW, Johnson VH, Gonzalez HF, Arney TL, Herman NL, Johnson RF. The pharmacokinetics of epidural lidocaine and bupivacaine during cesarean section. Anesth Analg 1997; 84: 527–32.[Abstract]
15 Reynolds F. A comparison of the potential toxicity of bupivacaine, lignocaine, and mepivacaine during epidural blockade for surgery. Br J Anaesth 1971; 43: 567–72.
16 Picard S, Rouet R, Flais F, et al. Proarrhythmic and antiarrhythmic effects of bupivacaine in an in vitro model of myocardial ischemia and reperfusion. Anesthesiology 1998; 88: 1318–29.[Medline]
17 Kulier AH, Woehlck HJ, Hogan QH, et al. Epinephrine dysrhythmogenicity is not enhanced by subtoxic bupivacaine in dogs. Anesth Analg 1996; 83: 62–7.[Abstract]
This article has been cited by other articles:
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  R. Preston Challenges in obstetric anesthesia and analgesia Can J Anesth, June 1, 2008; 55(6): 386 - 389. [Full Text] [PDF]
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