What is the management of fetal bradycardia in a patient receiving Terbutaline (beta-2 adrenergic agonist)?

Management of Fetal Bradycardia in a Patient Receiving Terbutaline

In cases of fetal bradycardia occurring in a patient receiving terbutaline, the medication should be discontinued immediately due to potential adverse effects on the fetus, and alternative management strategies should be implemented based on the severity and cause of the bradycardia.

Understanding the Relationship Between Terbutaline and Fetal Bradycardia

Terbutaline is a beta-2 adrenergic agonist that has been used in obstetrics primarily for tocolysis. However, it carries significant risks:

• The FDA has issued a warning against prolonged use of terbutaline (beyond 48-72 hours) for tocolysis 1
• Maternal administration of terbutaline can lead to increased fetal heart rate, but paradoxically may also cause fetal bradycardia in some cases 1
• Terbutaline crosses the placenta and can affect fetal cardiac function directly

Initial Assessment and Management

1. Discontinue terbutaline immediately

   • Terbutaline should be stopped as the first step in management
   • Prepare for possible emergency delivery while awaiting recovery 2

2. Implement basic resuscitative measures:

   • Position the mother in left lateral decubitus position to improve uteroplacental perfusion 3
   • Administer supplemental oxygen to the mother
   • Establish IV access if not already present
   • Correct any maternal hypotension with IV fluids

3. Continuous fetal monitoring:

   • Assess fetal heart rate pattern, including baseline rate, variability, and presence of accelerations/decelerations
   • Monitor for signs of fetal distress or acidosis

Specific Management Based on Bradycardia Severity

For Mild to Moderate Bradycardia (HR 80-100 bpm):

• Continue maternal position changes and oxygen administration
• Monitor closely for improvement after terbutaline discontinuation
• Consider obtaining fetal scalp pH if available and bradycardia persists beyond 5 minutes

For Severe Bradycardia (HR <80 bpm):

• If bradycardia persists for ≥2 minutes despite basic measures, prepare for emergency delivery 2
• Fetal acidosis becomes common if bradycardia lasts ≥10 minutes, particularly if the rate is <80 bpm with a flat baseline for ≥4 minutes 2
• Consider emergency cesarean delivery if no improvement is seen within 10 minutes

Special Considerations

1. Underlying causes: Evaluate for potential causes of bradycardia beyond terbutaline:

   • Congenital heart block (consider maternal autoimmune disease with anti-Ro/SSA antibodies) 3
   • Structural cardiac abnormalities
   • Cord compression or prolapse
   • Placental abruption

2. Timing of intervention:

   • In cases with ominous fetal heart rate pattern preceding the bradycardia or in abruptio placentae, immediate operative intervention without delay is recommended 2

3. Pacemaker consideration:

   • For persistent bradycardia due to congenital heart block, a temporary pacemaker may be necessary 3
   • A pacemaker for symptomatic bradycardia can be implanted at any stage of pregnancy using echo guidance 3

Monitoring After Resolution

If bradycardia resolves after terbutaline discontinuation:

• Continue close fetal monitoring for at least 24 hours
• Assess for any signs of recurrent bradycardia or other arrhythmias
• Consider fetal echocardiography to evaluate for structural heart disease or conduction abnormalities

Pitfalls and Caveats

1. Do not restart terbutaline - Even if it was being used for tocolysis, alternative tocolytics should be considered if still indicated

2. Avoid other medications that may worsen bradycardia:

   • Beta-blockers (especially non-selective ones)
   • Calcium channel blockers when combined with magnesium sulfate 4

3. Be aware that terbutaline's effects on fetal heart rate can vary:

   • In some cases, terbutaline has been used to treat fetal bradycardia in complete heart block, with variable success 5, 6
   • However, this is not standard practice and should only be considered in specialized settings

4. Monitor maternal status closely:

   • Terbutaline can cause maternal tachycardia, hypotension, and metabolic acidosis 7
   • These maternal effects can further compromise fetal status

By following this management approach, clinicians can appropriately address fetal bradycardia in the setting of terbutaline administration, prioritizing both maternal and fetal well-being.