A primigravid patient at 39 weeks gestation arrives at the labor and delivery unit in acti… — USMLE Step 2 CK

A primigravid patient at $39$ weeks gestation arrives at the labor and delivery unit in active labor. Her prenatal course was uncomplicated. Uterine contractions are occurring every $3$ minutes. Initial examination reveals a blood pressure of $120/75 \text{ mm Hg}$ , a heart rate of $98/\text{min}$ , and a respiratory rate of $20/\text{min}$ . Routine admission laboratory results show a hemoglobin level of $10.8 \text{ g/dL}$ and a hematocrit of $32\%$ . Because the patient reports feeling mildly short of breath during contractions, an arterial blood gas analysis is obtained, which reveals a pH of $7.44$ , $\text{PaCO}_2$ of $28 \text{ mm Hg}$ , and $\text{PaO}_2$ of $104 \text{ mm Hg}$ . The patient subsequently requests neuraxial analgesia, and an epidural block is administered without technical difficulty. Twenty minutes later, she reports feeling dizzy and nauseated. Her blood pressure is now $86/50 \text{ mm Hg}$ . Concurrent electronic fetal monitoring demonstrates a baseline heart rate of $140/\text{min}$ , minimal variability, and symmetric, gradual decreases in the heart rate that reach their nadir after the peak of each uterine contraction. Which of the following is the most appropriate initial step in management?

Maternal repositioning and intravenous crystalloid administrationCevap
B
Immediate transfer for surgical delivery
C
Transcervical placement of an amnioinfusion catheter
D
Intravenous administration of sodium bicarbonate
E
Transfusion of one unit of packed red blood cells

Cevap

Maternal repositioning and intravenous crystalloid administration

The patient is experiencing acute uteroplacental insufficiency secondary to maternal hypotension, a common complication of the sympathetic blockade induced by epidural analgesia. This hypoperfusion manifests on the fetal monitor as late decelerations (a gradual decrease in fetal heart rate that reaches its nadir after the peak of the uterine contraction). The most appropriate initial management is intrauterine resuscitation to restore placental blood flow. This includes repositioning the patient into a lateral decubitus position to displace the uterus off the inferior vena cava and administering an intravenous crystalloid bolus to expand the intravascular volume. If these measures are insufficient, an intravenous vasopressor (such as ephedrine or phenylephrine) should be administered.

Adım Adım Çözüm

Interpret the fetal heart rate tracing in the context of the clinical presentation.

The tracing shows late decelerations (gradual decrease with nadir occurring after the contraction peak), which indicate uteroplacental insufficiency.

Accurate interpretation of the fetal heart rate pattern is required to identify the underlying pathophysiologic mechanism.

Identify the cause of the uteroplacental insufficiency.

The acute drop in maternal blood pressure from 120/75 to 86/50 mm Hg following epidural placement indicates sympathetic blockade-induced vasodilation.

Understanding the etiology dictates the appropriate corrective intervention.

Select the appropriate intrauterine resuscitation measure.

Maternal repositioning (e.g., left lateral decubitus) relieves aortocaval compression, and an intravenous fluid bolus expands the vascular space.

These conservative measures are the definitive first-line treatments to restore blood pressure and placental perfusion before escalating to vasopressors or operative delivery.

Evaluate the laboratory findings to rule out other required interventions.

The mild anemia and compensated respiratory alkalosis are recognized as normal physiologic changes of pregnancy, requiring no treatment.

Prevents the selection of inappropriate interventions targeted at normal physiologic states.

Anahtar Kavram

Intrauterine resuscitation for epidural-induced maternal hypotension causing late fetal heart rate decelerations.

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Cevap

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