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Difficulty: HardObstetric Complications

During an ongoing labor induction for post-term pregnancy, a 3131-year-old nulliparous woman at 4141 weeks gestation is evaluated for abnormal fetal monitoring. She is receiving a continuous intravenous oxytocin infusion. Her most recent laboratory results demonstrate a hemoglobin concentration of 10.4 g/dL10.4\text{ g/dL} and a normal basic metabolic panel. On continuous electronic fetal monitoring, the baseline heart rate is 145/min145\text{/min} with moderate variability. The tracing reveals symmetric, gradual decreases in the fetal heart rate that nadir after the peak of uterine contractions and return to baseline after the contractions end. Simultaneously, the tocodynamometer records 77 contractions every 1010 minutes. In response, the clinical team stops the oxytocin infusion, alters her position to the left lateral decubitus, and provides an intravenous fluid bolus. Reassessment 1515 minutes later reveals ongoing uterine activity with 66 contractions per 1010-minute period and persistence of the fetal heart rate decelerations. Her cervix is 4 cm4\text{ cm} dilated.

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

  1. Subcutaneous injection of terbutalineAnswer
  2. B
    Preparation for emergency cesarean delivery
  3. C
    Initiation of prophylactic amnioinfusion
  4. D
    Transfusion of packed red blood cells
  5. E
    Continued observation with continuous fetal monitoring

Answer

Subcutaneous injection of terbutaline
The correct answer is subcutaneous injection of terbutaline. This patient is experiencing uterine tachysystole (defined as more than 55 contractions in a 1010-minute window), which is causing uteroplacental insufficiency and manifesting as recurrent late decelerations on the electronic fetal monitor. The initial management of tachysystole with abnormal fetal heart rate changes involves maternal repositioning, intravenous fluid boluses, and the immediate discontinuation of uterotonic agents like oxytocin. When these conservative measures fail to resolve the tachysystole and the fetal heart rate abnormalities persist after an appropriate observation period (e.g., 1010 to 1515 minutes), the next most appropriate step is the administration of a fast-acting tocolytic agent, such as terbutaline. Terbutaline relaxes the uterine musculature, increases blood flow to the intervillous space, and frequently resolves the fetal hypoxia. If the late decelerations persist even after tocolytic administration, then expedited delivery (e.g., cesarean delivery) would be indicated.

Step-by-Step Solution

1
Interpret the fetal heart rate tracing.
Identified recurrent late decelerations.
Gradual decreases in heart rate that nadir after the contraction peak indicate uteroplacental insufficiency.
2
Analyze the uterine contraction pattern.
Identified uterine tachysystole.
The tocodynamometer shows more than 5 contractions in a 10-minute window, which restricts blood flow to the placenta.
3
Evaluate the response to primary intrauterine resuscitation.
Tachysystole and late decelerations persisted despite stopping oxytocin, repositioning, and administering fluids.
Determines whether conservative measures were sufficient or if secondary interventions are required.
4
Select the appropriate secondary intervention.
Administer a tocolytic agent (terbutaline).
A tocolytic will rapidly relax the uterine musculature, spacing out contractions and restoring uteroplacental perfusion before resorting to a surgical delivery.

Key Concept

Management of uterine tachysystole and resulting late decelerations involves stepwise intrauterine resuscitation, ending with tocolytics if primary measures fail.
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Topics

Obstetric Complications

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