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Difficulty: HardLabor, Delivery, and Puerperium

A 29-year-old primigravida at 40 weeks gestation is evaluated in the labor and delivery unit during the active phase of labor. Her pregnancy has been uncomplicated. Her cervix is 6 cm dilated, 90% effaced, and the fetal head is at -1 station. Uterine contractions are occurring every 3 to 4 minutes and are of moderate intensity. Thirty minutes after admission, the patient requests and receives continuous epidural anesthesia for pain relief.

Fifteen minutes later, the patient reports feeling lightheaded and nauseated. Her blood pressure is 82/45 mm Hg, and her heart rate is 105/min. The continuous fetal heart rate monitoring previously showed a baseline of 145/min with moderate variability and positive accelerations. The tracing now reveals minimal variability and gradual, symmetric decreases in the fetal heart rate from the baseline to a nadir of 125/min. The onset, nadir, and recovery of the decelerations occur after the beginning, peak, and end of the uterine contractions, respectively. These decelerations occur with more than 50% of contractions.

The nurse immediately turns the patient onto her left side and administers a bolus of intravenous lactated Ringer solution. Ten minutes later, the patient's blood pressure remains 86/48 mm Hg, and the fetal heart rate tracing is unchanged.

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

  1. Administer ephedrine intravenouslyAnswer
  2. B
    Administer terbutaline subcutaneously
  3. C
    Initiate an amnioinfusion
  4. D
    Proceed with a cesarean delivery
  5. E
    Attempt a vacuum-assisted vaginal delivery

Answer

The correct step is to administer ephedrine intravenously to correct the maternal hypotension and restore uteroplacental perfusion.
The correct answer addresses the root cause of the fetal distress. Epidural anesthesia causes a sympathetic blockade that can result in significant vasodilation and maternal hypotension. The resulting drop in blood pressure decreases perfusion to the uterus and placenta, presenting on the fetal monitor as late decelerations and decreased variability. Standard stepwise intrauterine resuscitation for maternal hypotension involves repositioning the patient to a left lateral decubitus position (relieving aortocaval compression) and giving an IV fluid bolus. Because these initial measures were insufficient in this patient, the immediate next step is to administer an intravenous vasopressor, such as ephedrine or phenylephrine, to mechanically constrict the vessels, correct the hypotension, and restore placental perfusion.

Step-by-Step Solution

1
Interpret the fetal heart rate tracing.
The gradual decreases with nadirs occurring after the peak of the contraction describe late decelerations, which indicate uteroplacental insufficiency.
Accurate interpretation of the fetal monitor is required to identify the underlying physiological stressor.
2
Identify the cause of the uteroplacental insufficiency.
The late decelerations coincide with a significant drop in maternal blood pressure shortly after epidural placement, indicating epidural-induced sympathetic blockade.
Identifying the etiology of late decelerations guides targeted intrauterine resuscitation.
3
Evaluate the response to initial interventions.
Left lateral decubitus positioning (to relieve aortocaval compression) and intravenous fluid boluses were attempted but failed to restore blood pressure.
Treatment must follow a stepwise escalation protocol.
4
Select the appropriate next pharmacological intervention.
Administration of an intravenous vasopressor (ephedrine or phenylephrine) is selected.
Vasopressors are required to reverse the persistent sympathetic blockade and restore blood flow to the placenta before considering invasive surgical delivery.

Key Concept

Epidural anesthesia can cause sympathetic blockade leading to maternal hypotension and secondary uteroplacental insufficiency (late decelerations). First-line treatment is left lateral repositioning and IV fluids; if these fail, an intravenous vasopressor (e.g., ephedrine or phenylephrine) is the next best step.
Estimated Time:2m 0s
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Topics

Labor, Delivery, and Puerperium

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