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Difficulty: MediumObstetric Complications

A 2727-year-old gravida 33, para 22 at 3838 weeks and 44 days of gestation is in the labor unit undergoing induction for gestational diabetes. Uterine contractions are being augmented with a continuous infusion of a synthetic nonapeptide hormone. The continuous electronic fetal monitor demonstrates a baseline heart rate of 145145 /min with absent variability. Over the last 3030 minutes, the patient has experienced 1616 contractions. During this same timeframe, the fetal tracing displays recurrent, gradual decreases in heart rate that reach their nadir strictly after the peak of the corresponding contraction. The nursing staff immediately places the patient in the left lateral decubitus position, administers a 500500 mL intravenous bolus of lactated Ringer solution, and halts the uterotonic infusion. Ten minutes later, the patient continues to experience contractions every 9090 to 120120 seconds, and the fetal heart rate pattern remains unchanged. The patient's blood pressure is 118/76118/76 mm Hg and pulse is 8888 /min. Cervical examination reveals 55 cm dilation, 90%90\% effacement, and −1-1 station. Which of the following is the most appropriate next step in the management of this patient?

  1. Administer subcutaneous terbutalineAnswer
  2. B
    Perform immediate surgical delivery
  3. C
    Initiate an intrauterine normal saline infusion
  4. D
    Perform artificial rupture of the amniotic membranes
  5. E
    Resume the uterotonic infusion at half the previous rate

Answer

The most appropriate next step is to administer subcutaneous terbutaline to relax the uterine musculature and improve placental perfusion.
The correct answer is administering subcutaneous terbutaline. This patient is experiencing uterine tachysystole, defined as more than 55 contractions in a 1010-minute window (averaged over 3030 minutes). The excessively frequent contractions are impairing uteroplacental blood flow, leading to a Category III fetal heart rate (FHR) tracing characterized by absent variability and recurrent late decelerations. The initial management for this obstetric complication includes maternal repositioning (left lateral decubitus), an intravenous fluid bolus, and immediate cessation of any uterotonic agents. If the tachysystole and abnormal FHR pattern persist despite these initial maneuvers, the next best step is to administer a rapid-acting tocolytic medication. Subcutaneous terbutaline, a beta-2 adrenergic receptor agonist, relaxes the uterine smooth muscle, decreases contraction frequency, and allows uteroplacental perfusion to recover. If the FHR tracing does not improve following tocolysis, emergency surgical delivery would then be indicated.

Step-by-Step Solution

1
Analyze the fetal heart rate (FHR) tracing and contraction pattern.
The patient has uterine tachysystole (1616 contractions in 3030 minutes, which is >5>5 per 1010 minutes) and a Category III FHR tracing (absent variability with recurrent late decelerations).
Identifying the FHR category and contraction frequency establishes the diagnosis of tachysystole-induced fetal hypoxia.
2
Evaluate the response to initial resuscitative measures.
The patient was appropriately repositioned, given a fluid bolus, and the uterotonic agent was stopped. However, 1010 minutes later, tachysystole and the Category III tracing persist.
Standard initial intrauterine resuscitation must be attempted before advancing to pharmacological or surgical interventions.
3
Determine the next pharmacological or surgical intervention.
Because the tachysystole has not resolved with standard supportive measures and withdrawal of oxytocin, a tocolytic agent (e.g., terbutaline) is indicated to relax the uterus.
Relaxing the uterus reduces the frequency of contractions, thereby restoring uteroplacental blood flow and resolving the fetal hypoxia before resorting to operative delivery.

Key Concept

Management of uterine tachysystole with nonreassuring fetal status involves supportive measures (repositioning, fluids, stopping uterotonics) followed by tocolysis (e.g., terbutaline) if the abnormal pattern persists.
Estimated Time:1m 15s
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Topics

Obstetric Complications

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