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Difficulty: MediumObstetric Complications

A 24-year-old nulliparous woman at 40 weeks gestation is evaluated in the labor and delivery unit due to painful uterine contractions. She has no significant past medical history, and her prenatal care has been routine. On admission, her blood pressure is 118/76 mm Hg and her pulse is 78/min. Cervical examination shows 5 cm dilation and 90% effacement. The fetal head is engaged. A lumbar epidural is placed for pain control. Twenty minutes later, the patient complains of dizziness and nausea. Repeat maternal vital signs show a blood pressure of 82/45 mm Hg and a pulse of 105/min. The continuous fetal monitor displays a baseline heart rate of 125/min, minimal variability, and symmetric decreases in the fetal heart rate that nadir after the peak of the uterine contractions. Uterine contractions are occurring every 3 to 4 minutes and lasting 60 seconds.

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

  1. A
    Initiation of transcervical amnioinfusion
  2. B
    Intravenous administration of a beta-2 adrenergic agonist
  3. Maternal left lateral decubitus positioning and rapid intravenous hydrationAnswer
  4. D
    Transfer to the operating room for cesarean delivery
  5. E
    Continued expectant management with reassurance

Answer

Maternal left lateral decubitus positioning and rapid intravenous hydration
The correct answer is maternal left lateral decubitus positioning and rapid intravenous hydration. This patient is experiencing late fetal heart rate (FHR) decelerations secondary to maternal hypotension, a common complication of epidural anesthesia. Epidural blocks the sympathetic nervous system, leading to peripheral vasodilation and decreased venous return to the heart. This reduces cardiac output and blood pressure, which in turn decreases uteroplacental perfusion, causing fetal hypoxia and late decelerations. The initial step in management (intrauterine resuscitation) aims to restore maternal blood pressure and placental blood flow. Left lateral decubitus positioning displaces the gravid uterus off the inferior vena cava, enhancing venous return. A rapid intravenous fluid bolus expands intravascular volume. If these initial measures fail, intravenous vasopressors (such as ephedrine or phenylephrine) are indicated.

Step-by-Step Solution

1
Identify the primary maternal complication.
The patient has developed acute hypotension (82/45 mm Hg) shortly after receiving a lumbar epidural.
Epidural anesthesia frequently causes sympathetic blockade, leading to vasodilation, venous pooling, and subsequent maternal hypotension.
2
Interpret the fetal heart rate (FHR) tracing.
The tracing shows minimal variability and late decelerations (decreases in FHR that nadir after the peak of the contraction).
Maternal hypotension decreases uteroplacental perfusion, leading to transient fetal hypoxia, which classically presents as late decelerations on the FHR monitor.
3
Determine the most appropriate initial step in management.
The correct intervention is intrauterine resuscitation to restore uteroplacental perfusion.
Maternal left lateral decubitus positioning relieves aortocaval compression, increasing venous return. Rapid intravenous hydration expands the intravascular volume, thereby correcting the epidural-induced hypotension and improving placental blood flow.

Key Concept

Epidural anesthesia can cause maternal hypotension through sympathetic blockade, resulting in decreased uteroplacental perfusion and fetal late decelerations. Initial management includes left lateral positioning and intravenous fluid boluses.
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Topics

Obstetric Complications

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