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Difficulty: HardObstetric Complications

A patient at 40 weeks gestation (G1P0) is admitted to the labor and delivery unit for labor augmentation with intravenous oxytocin. She is 28 years old, and her prenatal course has been uncomplicated. She is utilizing epidural anesthesia for pain management. Her cervix is currently 5 cm dilated, 90% effaced, and at -1 station. Over the past 30 minutes, the fetal heart rate monitor displays a baseline of 150/min. The amplitude of the peak-to-trough fetal heart rate fluctuations is 3 to 5 beats per minute. There are recurrent, gradual decreases in the fetal heart rate that begin after the peak of each uterine contraction and return to baseline after the contraction ends. Tocodynamometry reveals 7 contractions per 10-minute period, averaged over the last 30 minutes, with each contraction lasting 60 to 80 seconds. In response to these findings, the oxytocin infusion is promptly discontinued, the patient is placed in the left lateral decubitus position, and a 500-mL intravenous bolus of lactated Ringer solution is administered. Fifteen minutes later, the contraction frequency remains unchanged, and the fetal heart rate tracing continues to demonstrate the same pattern of recurrent decelerations with minimal fluctuations. Maternal vital signs are blood pressure 118/76 mmHg, pulse 88/min, and temperature 37.1°C (98.8°F). Which of the following is the most appropriate next step in management?

  1. Administer intravenous terbutalineAnswer
  2. B
    Proceed to emergent cesarean delivery
  3. C
    Perform an amnioinfusion
  4. D
    Administer intravenous ephedrine
  5. E
    Administer intravenous magnesium sulfate

Answer

Administer intravenous terbutaline
The patient is experiencing uterine tachysystole (defined as >5 contractions in 10 minutes), which is compromising uteroplacental blood flow and causing recurrent late decelerations with minimal variability (a Category II fetal heart rate tracing). The standard initial management for tachysystole with FHR abnormalities includes discontinuing uterotonics (oxytocin), repositioning the mother, and administering an IV fluid bolus. Because these initial measures have failed to resolve the tachysystole and the FHR abnormalities after 15 minutes, the next indicated step is acute tocolysis. Terbutaline, a beta-2 adrenergic agonist, acts rapidly to relax the myometrium, space out the contractions, and restore adequate placental perfusion.

Step-by-Step Solution

1
Interpret the fetal heart rate (FHR) tracing characteristics.
The FHR shows a baseline of 150/min, minimal variability (3 to 5 bpm), and recurrent late decelerations (nadirs occurring after contraction peaks), which constitutes a Category II tracing.
Accurate interpretation of the FHR category dictates the urgency and type of intrauterine resuscitation required.
2
Identify the underlying etiology for the abnormal FHR tracing.
The tocodynamometry indicates uterine tachysystole (7 contractions in 10 minutes). Tachysystole limits uterine relaxation time, causing uteroplacental insufficiency and resulting in late decelerations.
Treating the root cause of the uteroplacental insufficiency is necessary to improve fetal oxygenation.
3
Evaluate the clinical response to the initial resuscitative interventions.
First-line interventions (stopping oxytocin, maternal repositioning, and IV fluids) were correctly implemented but failed to resolve the tachysystole or the late decelerations after 15 minutes.
If first-line conservative measures fail, the management algorithm must escalate to pharmacological intervention before considering surgery.
4
Select the appropriate escalated intervention based on the algorithmic management of tachysystole.
The next step is the administration of a fast-acting tocolytic, such as terbutaline, to actively relax the uterus.
Tocolysis decreases uterine contraction frequency and tone, restoring intervillous blood flow and treating the specific cause of the late decelerations without prematurely proceeding to a cesarean delivery.

Key Concept

Algorithmic management of uterine tachysystole causing Category II or III FHR tracings requires sequential escalation: discontinuation of uterotonics, supportive measures (repositioning, fluids), acute tocolysis (e.g., terbutaline), and finally operative delivery if medical therapy fails.
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Topics

Obstetric Complications

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