Case report

A 29-year-old, 92 kg primagrivida presented with a dichorionic-diamniotic twin pregnancy at 35 4/7 weeks gestation with increased systolic blood pressure, headaches, and visual changes. She had a history of migraine headaches, chronic back pain, and poorly controlled type 1 CRPS following a foot injury 10 years prior. She had undergone multiple extensive and comprehensive assessments by pain management consultants, as well as numerous intervention trials, including various analgesic medications, ketamine and magnesium infusions, plasmapheresis, and implantation of a spinal cord stimulator (SCS) (figure 1), all with limited success. Of note, her prior magnesium therapy was in a different state, and information as to specific dosing regimen was unavailable. When she became pregnant, she learnt from her obstetric provider that the only reported safe interventions for CRPS in pregnancy include ascorbic acid, physical therapy, and transcutaneous electrical nerve stimulation therapy. Despite case reports of safe use of SCS in pregnant women, the patient chose to have her SCS turned off, and she discontinued all other therapies.

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Figure 1

CT images demonstrating SCS electrodes at T11/12, with wires traversing caudad and continuing toward L hip. SCS, spinal cord stimulator.

Her blood pressure on admission was 160/94, and she endorsed a headache that felt different from her baseline migraines, and new onset blurred vision. In addition to the diagnosis of preeclampsia, the obstetric team was also concerned about the fetal size discordance (twin A—64th percentile, twin B—20th percentile), and delivery was recommended. Her platelet count was 94 000 (with a prior count of 186 000). Her headache and blood pressure improved following acetaminophen and initiation of magnesium therapy (6 g intravenous load, 2 g/hour infusion). After discussion with the obstetric team she opted for induction of labor rather than cesarean delivery.

CT scan images were available and confirmed SCS paddles at the T12-L1 level and lead wires traversing caudad to her left buttock. Risks (including abnormal or ineffective analgesia) and benefits were discussed, and the patient requested epidural analgesia at 4 cm cervical dilation. An epidural catheter was uneventfully placed at the L3-L4 interspace via a right paramedian approach, using an 18-gauge Tuohy needle with loss of resistance to saline. Complete labor analgesia and adequate sensory block (left T9-S1, right T10-L5) were achieved following administration of 2 mL 1.5% lidocaine with 5 µg/mL epinephrine (test dose) and 10 mL 0.125% bupivacaine with 5 µg/mL fentanyl. Analgesia was maintained with programmed intermittent epidural boluses (5 mL every 30 min) and patient-controlled demand doses (5 mL, lock out 10 min) using a solution of 0.1% bupivacaine with 2 µg/mL fentanyl.

Her systolic blood pressure remained well controlled between 120 and 134 mm Hg throughout labor. She progressed to complete cervical dilation 13 hours after epidural placement and was taken to the operating room for an uncomplicated vaginal twin delivery 30 min later, after which the epidural catheter was removed. Magnesium infusion was continued for 24 hours postpartum for seizure prophylaxis. Although she experienced some weakness and fatigue from hypermagnesemic therapy, she reported complete pain relief of her CRPS symptoms long after her epidural analgesic block had resolved, throughout the time she received magnesium. This was notable for being the only time in 10 years that she recalled being pain-free. Soon after discontinuation of magnesium, her CRPS symptoms returned.

In a follow-up conversation 14 months later, the patient reported that, beginning 4 months postpartum, she has undergone intravenous magnesium treatments once or twice per week, with a dose of 1 g over 2 hours. In her words, “Those are the best 2 hours of my week.” During the infusion, she experiences some fatigue, but reports that her pain is reduced from her typical 7 to 9 out of 10 severity to 5 out of 10, which she describes as tolerable. The analgesia is short-lived, though, and the 1 hour drive each way to the clinic for this treatment is not easy for this mother of 2. She states that, despite her request, her pain management specialist is reluctant to infuse larger doses of magnesium. Serum magnesium levels were never measured perioperatively, but she reports that her levels have been assessed in the past and have never demonstrated deficiency. The patient remains hopeful for better and more long-lasting pain relief in the future as she continues to pursue pain management consultation regarding other potential CRPS pain therapies.