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Difficulty: Very hardObstetric Complications

A 31-year-old G1P0 woman at 34 weeks gestation is admitted to the labor and delivery unit for management of preeclampsia with severe features. Upon admission, her blood pressure is 175/115 mmHg, and laboratory evaluation reveals a platelet count of 90,000/mm 3^3, aspartate aminotransferase of 110 U/L, and alanine aminotransferase of 125 U/L. A continuous intravenous infusion of magnesium sulfate is initiated for seizure prophylaxis, along with intravenous hydralazine.

Over the subsequent 12 hours, the patient receives 3 liters of intravenous lactated Ringer solution because her urine output has been consistently 15 mL/hour. She now complains of new-onset, severe shortness of breath, a persistent cough, and the inability to lie flat.

Current vital signs are:
Temperature: 37.0°C (98.6°F)
Blood pressure: 160/100 mmHg
Pulse: 115/min
Respiratory rate: 28/min
Oxygen saturation: 86% on room air

Physical examination reveals 3+ pitting edema of the lower extremities extending to the knees and bilateral basilar crackles on lung auscultation. Deep tendon reflexes are 2+ and symmetric globally.

Arterial blood gas analysis on room air shows:
pH: 7.46
PaO 2_2: 55 mmHg
PaCO 2_2: 28 mmHg
HCO 3−_3^-: 19 mEq/L

The fetal heart rate tracing demonstrates a baseline of 145/min, minimal variability, and recurrent late decelerations.

Which of the following is the most appropriate next step in the management of this patient?

  1. Intravenous administration of furosemideAnswer
  2. B
    Administration of intravenous calcium gluconate
  3. C
    Proceed directly to emergent cesarean delivery
  4. D
    Intravenous administration of broad-spectrum antibiotics
  5. E
    Intravenous administration of sodium bicarbonate

Answer

Intravenous administration of furosemide is the correct next step in management.
Intravenous administration of furosemide is the most appropriate next step because it directly addresses the acute pulmonary edema, a life-threatening complication of severe preeclampsia. Preeclampsia induces a state of increased capillary permeability and high afterload. Aggressive fluid resuscitation for oliguria—which is usually caused by renal vasospasm rather than true intravascular depletion—readily precipitates fluid extravasation into the lungs. Loop diuretics rapidly decrease preload, relieving pulmonary congestion and improving oxygenation, which must be achieved before emergent delivery is considered.

Step-by-Step Solution

1
Analyze the patient's acute respiratory distress in the context of her underlying condition.
The patient has severe preeclampsia and received large volumes of intravenous fluids for oliguria. She now presents with tachypnea, hypoxia, and bilateral basilar crackles, indicating acute pulmonary edema.
Preeclampsia causes generalized endothelial dysfunction, leading to increased capillary permeability. When aggressive fluid boluses are given (often mistakenly to treat intense renal vasospasm), the fluid leaks into the alveolar spaces, causing pulmonary edema.
2
Differentiate pulmonary edema from potential medication toxicities.
Magnesium toxicity is ruled out because the patient's deep tendon reflexes are preserved (2+) and she is tachypneic (RR 28/min). Magnesium toxicity would cause absent reflexes and respiratory depression.
Oliguria increases the risk of magnesium accumulation, making toxicity a plausible distractor. However, the physical examination explicitly contradicts this diagnosis.
3
Interpret the arterial blood gas (ABG) findings.
The ABG shows severe hypoxemia (PaO 2_2 55 mmHg) but a normal pregnancy-associated compensated respiratory alkalosis (pH 7.46, low PaCO 2_2, low HCO 3−_3^-).
It is critical not to misinterpret the low bicarbonate as a pathological metabolic acidosis; it is a physiologic compensation for pregnancy-induced hyperventilation.
4
Evaluate the fetal heart rate (FHR) tracing and determine the immediate priority.
The late decelerations indicate fetal hypoxia, which is secondary to the profound maternal hypoxemia. Maternal stabilization with oxygen, afterload reduction, and diuresis (furosemide) must precede any emergent surgical delivery.
Proceeding to the operating room with a severely hypoxic, unstable mother drastically increases the risk of maternal mortality. Resuscitating the mother will inherently improve fetal oxygenation.

Key Concept

Diagnosis and management of acute pulmonary edema as a complication of severe preeclampsia.
Estimated Time:2m 0s
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Topics

Obstetric Complications

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