Question

A 26-year-old woman, G1P0, at 38 weeks gestation presents to the labor and delivery triage unit with painful uterine contractions. Her prenatal course has been uncomplicated. Vital signs on admission are temperature $37.0^{\circ}\text{C}$ ($98.6^{\circ}\text{F}$), blood pressure 125/80 mmHg, heart rate 92/min, and respiratory rate 18/min. Cervical examination shows 5 cm dilation, 90% effacement, and -1 station. She is admitted and receives epidural analgesia. Thirty minutes later, she complains of sudden dizziness, nausea, and dyspnea, stating "I feel like I cannot breathe." Her blood pressure is now 82/45 mmHg and heart rate is 118/min. The continuous fetal heart rate tracing reveals a baseline of 120/min with minimal variability and recurrent, visually apparent, gradual decreases in the fetal heart rate (onset to nadir $\geq$ 30 seconds) that consistently begin after the peak of each contraction and return to baseline after the contraction ends.

Laboratory studies obtained on admission:
Hemoglobin: 11.2 g/dL
Platelets: $180,000/\text{mm}^3$

Arterial blood gas (room air):
pH: 7.44
$\text{PaO}_2$: 104 mmHg
$\text{PaCO}_2$: 29 mmHg
$\text{HCO}_3^-$: 20 mEq/L

Despite the physician's explanation of the fetal tracing, the patient states, "I am terrified of surgery and absolutely refuse any operative deliveries." Which of the following is the most appropriate initial step in management?