Anesthesiology APPLIED Exam › Obstetric anesthesia

Fetal heart rate tracings and emergent delivery

Obstetric anesthesia·~5 min read· Physician-reviewed✓ Sourced · 2

Stem

A 29-year-old G1P0 at 39 weeks, 84 kg, is on an oxytocin infusion with a working labor epidural placed two hours ago. Twenty minutes after a 10 mL epidural bolus, her blood pressure is 86/48. The tracing shows a baseline of 150 bpm, absent variability, and recurrent late decelerations, with six contractions per 10 minutes averaged over the last 30 minutes. The obstetrician says she may need to deliver.

Question

How do you interpret this tracing, and what is your role now?

Ideal answer

HeadlineCategory 3: baseline 150, absent variability, recurrent late decelerations, tachysystole. It predicts fetal acidemia: intrauterine resuscitation now, expedited delivery if it does not resolve.

Ask what happened in the last 30 minutes, because an epidural bolus followed by hypotension is a reversible cause.¹
Left uterine displacement, phenylephrine, oxygen, fluid bolus, to relieve aortocaval compression² and restore placental perfusion; my part of the resuscitation is maternal.
Oxytocin stopped; terbutaline 250 mcg subcutaneously for the tachysystole.
Test the epidural level, draw up 3% chloroprocaine to extend it in the operating room if the tracing does not recover.
Tell the obstetrician how long each option takes: spinal if no working catheter and a few minutes exist, general only when there is no time.

Watch for: recovery of the tracing; I do not trade the mother's safety for a minute of fetal time.

Breaking down the answer

Category drives urgency, not one deceleration — in the three-tier NICHD system, category 2 is common and needs surveillance and resuscitation; category 3 triggers delivery if resuscitation fails. Asking about the last 30 minutes shows judgment: tachysystole after rapid intrathecal analgesia is another reversible cause.¹
Variability is the key feature — moderate variability (6–25 bpm) reliably excludes ongoing metabolic acidemia; absent variability is the ominous sign. Stating it first shows organization.
Late versus variable — late decelerations begin after the contraction peak and mean uteroplacental insufficiency with fetal hypoxemia, so maternal pressure and uterine tone come first. Variable decelerations mean cord compression and respond to position change and amnioinfusion.
Extend the epidural — with a tested catheter, 15–20 mL of 3% chloroprocaine gives a surgical block in about 5 minutes, the agent of choice for rapid extension.¹ Changes if: none at hand, lidocaine 2% with epinephrine and bicarbonate.
Spinal versus general — a single-shot spinal takes 5–8 minutes in experienced hands. Changes if: the baby is needed sooner, or a neuraxial contraindication, then general after a quick airway assessment.
The 30-minute standard — a system goal, not a clinical deadline; I ask the obstetrician for the target decision-to-incision time.

Follow-up question

The tracing does not recover and the obstetrician calls for emergent cesarean. You learn that this catheter is her third tonight after two failed, and her airway is Mallampati 4. How do you anesthetize her?

Follow-up answer

HeadlineTwo competing hazards, an unreliable catheter and a difficult airway; I ask the team for 60 seconds for an airway check and a plan.

Because the airway is difficult, I try to avoid general anesthesia: I dose chloroprocaine through the catheter in the operating room while she is prepped and test the level. If it fails, a rapid spinal while the team prepares. If the fetus cannot wait and neuraxial fails, I induce with a video laryngoscope and a second-generation supraglottic airway ready, having agreed in advance that we proceed with surgery on a supraglottic airway if intubation fails. I keep the obstetrician informed of my timeline and reassess the tracing and her airway at each step.

Pitfalls that cost points

Reading the tracing without stating variability.
Going straight to general anesthesia without asking about the epidural.
Stating the 30-minute rule as if it were a hard clinical deadline.
Ignoring maternal hypotension as the cause of decelerations after an epidural bolus.

Rapid-fire

Q: What defines tachysystole? A: More than five contractions in 10 minutes averaged over 30 minutes.

Q: Why does maternal hypotension cause late decelerations? A: Uterine blood flow is pressure-dependent with no autoregulation, so a fall in maternal pressure, including from supine aortocaval compression, reduces placental perfusion and oxygen delivery.²

Q: What is a sinusoidal pattern? A: A smooth undulating wave at 3–5 cycles per minute; it suggests severe fetal anemia and is category 3.

Q: Why chloroprocaine over bupivacaine for extension? A: Faster onset and very low systemic toxicity because of rapid ester hydrolysis.¹

Numbers to know

Item	Value
Normal baseline	110–160 bpm
Moderate variability	6–25 bpm
Tachysystole	>5 contractions/10 min
Chloroprocaine 3% extension	15–20 mL, onset ~5 min
Terbutaline	250 mcg SC
Decision-to-incision goal	≤30 min (system benchmark)

Sources

1.Obstetric Regional Anesthesia · NYSORA · nysora.com
2.Changes in Maternal Physiology During Pregnancy (Update in Anaesthesia 21) · WFSA · resources.wfsahq.org

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.