A 28-year-old primigravida at 39 weeks gestation is admitted to the labor and delivery uni… — USMLE Step 2 CK

A $28$ -year-old primigravida at $39$ weeks gestation is admitted to the labor and delivery unit in active labor. Her pregnancy has been uncomplicated. Her vital signs on admission are temperature $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure $118/76$ mm Hg, and pulse $82$ /min. Cervical examination shows $5$ cm dilation, $90\%$ effacement, and $0$ station. Fetal heart rate monitoring demonstrates a baseline of $145$ /min with moderate variability, spontaneous accelerations, and no decelerations. Uterine contractions occur every $3$ to $4$ minutes. The patient requests pain management, and a continuous epidural infusion of bupivacaine and fentanyl is initiated. Twenty minutes later, the patient reports feeling lightheaded and nauseated. Her blood pressure is now $84/48$ mm Hg and pulse is $112$ /min. Simultaneously, the fetal heart rate baseline drops to $90$ /min with minimal variability and has remained at this rate for the past $4$ minutes. Which of the following is the most appropriate next step in the management of this patient?

Intravenous vasopressor administrationAnswer
B
Urgent surgical delivery
C
Subcutaneous terbutaline injection
D
Transvaginal amnioinfusion
E
Continued observation with maternal reassurance

Answer

Intravenous vasopressor administration

The correct response is intravenous vasopressor administration. This patient is experiencing epidural-induced maternal hypotension. Epidural analgesia blocks the sympathetic nerve fibers, leading to peripheral vasodilation, venous pooling, and a drop in cardiac output. This sudden hypotension reduces uteroplacental blood flow, causing acute fetal hypoxia that manifests as a prolonged fetal heart rate deceleration (a drop in baseline of

\geq 15

/min lasting

\geq 2

minutes but

< 10

minutes). The most appropriate initial step in management is intrauterine resuscitation directed at the underlying cause. This involves left lateral maternal positioning (to relieve aortocaval compression), administration of an intravenous fluid bolus, and intravenous vasopressors such as ephedrine or phenylephrine to rapidly restore maternal blood pressure and placental perfusion.

Step-by-Step Solution

Identify the primary complication occurring after the epidural placement.

The patient developed symptomatic hypotension (

84/48

mm Hg) shortly after epidural initiation.

Epidural analgesia frequently causes sympathetic blockade, leading to vasodilation and decreased venous return.

Correlate the maternal vital signs with the fetal heart rate tracing.

The sudden maternal hypotension caused decreased uteroplacental perfusion, resulting in fetal hypoxia and a prolonged fetal heart rate deceleration (

90

/min for

4

minutes).

Fetal oxygenation is directly dependent on maternal blood pressure and adequate placental blood flow.

Determine the most appropriate intervention for this specific etiology.

Intrauterine resuscitation via left lateral maternal positioning, intravenous fluid bolus, and intravenous vasopressor administration is indicated.

Correcting the underlying maternal hypotension will restore placental perfusion and resolve the fetal deceleration.

Key Concept

Epidural anesthesia can cause sympathetic blockade resulting in maternal hypotension and decreased uteroplacental perfusion, often manifesting as a prolonged fetal heart rate deceleration. Initial management includes intravenous fluids and vasopressors (e.g., ephedrine or phenylephrine).

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