A 40-year-old woman is evaluated on the labor and delivery unit for increasing shortness of breath and muscle weakness. Six hours ago, the patient had a spontaneous vaginal delivery at 38 weeks gestation. Immediately after delivery, she developed a blood pressure of 170/110 mm Hg with a headache and was diagnosed with preeclampsia with severe features. A magnesium sulfate infusion was initiated for seizure prophylaxis, and blood pressure improved with intermittent hypertensive therapy. Now, the patient reports difficulty breathing, flushing, and muscle weakness. She does not have chest pain or palpitations. The patient has no chronic medical conditions and has had no surgeries. Blood pressure is 144/84 mm Hg, pulse is 68/min, and respirations are 10/min. The patient appears drowsy and has difficulty keeping her eyes open. The lungs are clear to auscultation bilaterally. Deep tendon reflexes are absent. There is bilateral pitting edema up to the knees. Urine output is 50 mL over the past 3 hours. Which of the following is the best next step in management of this patient?

Question

A 40-year-old woman is evaluated on the labor and delivery unit for increasing shortness of breath and muscle weakness.  Six hours ago, the patient had a spontaneous vaginal delivery at 38 weeks gestation.  Immediately after delivery, she developed a blood pressure of 170/110 mm Hg with a headache and was diagnosed with preeclampsia with severe features.  A magnesium sulfate infusion was initiated for seizure prophylaxis, and blood pressure improved with intermittent hypertensive therapy.  Now, the patient reports difficulty breathing, flushing, and muscle weakness.  She does not have chest pain or palpitations.  The patient has no chronic medical conditions and has had no surgeries.  Blood pressure is 144/84 mm Hg, pulse is 68/min, and respirations are 10/min.  The patient appears drowsy and has difficulty keeping her eyes open.  The lungs are clear to auscultation bilaterally.  Deep tendon reflexes are absent.  There is bilateral pitting edema up to the knees.  Urine output is 50 mL over the past 3 hours.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

11ec25c8_da72_8da1_bc81_e7383d35ed8b_MD0003_00 Magnesium sulfate is administered to patients with preeclampsia with severe features to prevent and treat eclamptic seizures. Magnesium acts as a calcium channel blocker on the CNS to raise the seizure threshold. However, with increasing serum levels, magnesium sulfate toxicity can develop. Patients may initially present with nausea, flushing, and hyporeflexia due to magnesium inhibition of presynaptic acetylcholine release (ie, neuromuscular inhibition). Further toxicity is uncommon in patients with normal renal function, but those with decreased urine output, such as this patient, are at a higher risk due to decreased urinary excretion of magnesium. Therefore, magnesium toxicity can progress to cause further muscle weakness, loss of deep tendon reflexes (ie, areflexia), and respiratory depression (eg, drowsiness, respirations of 10/min). At severely high serum magnesium levels, patients are at risk for respiratory paralysis and cardiac arrhythmias. Because of these life-threatening risks, patients treated with magnesium sulfate require close monitoring. Patients with signs of toxicity require a serum magnesium level and immediate cessation of magnesium sulfate. In addition, patients are administered calcium gluconate, which reverses neuromuscular paralysis, stabilizes cardiac membranes, and prevents cardiac arrest. (Choice B) Intravenous heparin infusions are used to manage an acute pulmonary embolus, which may present with dyspnea; however, these patients typically also have chest pain and tachypnea rather than respiratory depression. In addition, a pulmonary embolus is not associated with areflexia. (Choice C) Labetalol is administered to patients with preeclampsia and severely elevated blood pressures (eg, systolic ≥160 mm Hg or diastolic ≥110 mm Hg). This patient's blood pressure does not meet the criteria for acute therapy. (Choice D) Naloxone is used to reverse opioid toxicity, which can present with drowsiness and respiratory depression. However, deep tendon reflexes are typically preserved, making this diagnosis less likely in this patient. (Choice E) Normal saline boluses may be used to treat decreased urine output due to hypovolemia (eg, acute blood loss). This patient's decreased urine output is most likely due to renal insufficiency associated with preeclampsia. In addition, fluid boluses increase the risk of pulmonary edema in patients with preeclampsia. Educational objective: Magnesium sulfate toxicity typically presents with signs of progressive neuromuscular inhibition (eg, areflexia, respiratory depression). Treatment is with cessation of magnesium sulfate and initiation of calcium gluconate to reverse neuromuscular paralysis and prevent cardiac arrest. References: ACOG Committee opinion no 652: magnesium sulfate use in obstetrics. (http://www.ncbi.nlm.nih.gov/pubmed/26695587) An integrative review of the side effects related to the use of magnesium sulfate for pre-eclampsia and eclampsia management. (http://www.ncbi.nlm.nih.gov/pubmed/23383864)

A 40-Year-Old Woman Is Evaluated on the Labor and Delivery