During the active phase of labor at 39 weeks of gestation, a primigravid patient requests … — USMLE Step 2 CK

During the active phase of labor at $39$ weeks of gestation, a primigravid patient requests pain relief. An epidural catheter is placed and a standard dose of local anesthetic is administered. Ten minutes later, the patient reports feeling lightheaded and nauseated. Her blood pressure has decreased from a baseline of $120/75\text{ mmHg}$ to $85/50\text{ mmHg}$ , and her heart rate is $112/\text{min}$ . Continuous electronic fetal monitoring, which previously demonstrated a baseline of $140/\text{min}$ with moderate variability and no decelerations, now reveals a sudden decrease in the fetal heart rate to $85/\text{min}$ that has persisted for $3$ minutes. Uterine contractions are occurring every $4$ minutes and are of normal intensity. Which of the following is the most appropriate next step in the management of this patient?

Intravenous administration of ephedrineAnswer
B
Perform an emergency cesarean delivery
C
Inject terbutaline subcutaneously
D
Begin an amnioinfusion with isotonic saline
E
Reassure the patient and continue routine monitoring

Answer

The correct intervention is the intravenous administration of a vasopressor such as ephedrine or phenylephrine to correct the maternal hypotension.

The correct response addresses the root cause of the fetal distress. Epidural anesthesia causes a sympathetic blockade that can result in profound peripheral vasodilation and maternal hypotension. This acute drop in maternal blood pressure reduces blood flow to the intervillous space, leading to decreased fetal oxygenation and a prolonged deceleration on the fetal monitor. The most direct and appropriate management is to restore maternal blood pressure using an intravenous vasopressor such as ephedrine or phenylephrine, typically accompanied by an IV fluid bolus and displacing the uterus off the major vessels by placing the patient in a left lateral decubitus position.

Step-by-Step Solution

Identify the primary complication occurring after the epidural placement.

The patient has developed symptomatic maternal hypotension (

85/50\text{ mmHg}

), a common side effect of neuraxial anesthesia due to sympathetic blockade and vasodilation.

Recognizing the iatrogenic cause of the vital sign changes is necessary to guide specific therapy.

Evaluate the fetal heart rate tracing in the context of the maternal status.

The fetal monitor shows a prolonged deceleration (a decrease of

\geq 15\text{ bpm}

lasting

\geq 2

minutes but

< 10

minutes).

Maternal hypotension leads to decreased uteroplacental blood flow, resulting in acute fetal hypoxia and a reflex bradycardia/deceleration.

Select the most appropriate intervention to address both the maternal and fetal status.

Administration of intravenous ephedrine (or phenylephrine) along with a fluid bolus and left lateral positioning.

Vasopressors directly counteract the sympathectomy-induced vasodilation, restoring maternal blood pressure, placental perfusion, and resolving the fetal deceleration.

Key Concept

Epidural anesthesia can cause sympathetic blockade leading to maternal hypotension, which decreases placental perfusion and manifests as a prolonged fetal heart rate deceleration. The initial management includes maternal repositioning, IV fluids, and vasopressors (e.g., ephedrine).

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