A pregnant woman at 36 weeks gestation is lying supine during a prenatal examination. She suddenly complains of dizziness, nausea, and feeling faint. Her blood pressure drops from 120/80 mmHg to 90/50 mmHg. What is the most appropriate initial nursing assessment?

The scenario describes a classic presentation of supine hypotensive syndrome (also known as aortocaval compression syndrome). At 36 weeks gestation, the gravid uterus is large and heavy. When the patient lies flat on her back, the uterus compresses two major retroperitoneal vessels against the vertebral column: the inferior vena cava (IVC) and the abdominal aorta.

Compression of the IVC is the primary driver of this syndrome. It significantly reduces venous return to the heart (preload), which in turn decreases cardiac output and blood pressure. The sudden drop from 120/80 mmHg to 90/50 mmHg reflects this hemodynamic instability. The resulting cerebral hypoperfusion leads to the patient's symptoms of dizziness, nausea, and a sensation of faintness. While aortic compression can also occur and contribute to increased afterload and reduced uteroplacental perfusion, the rapid hypotension is primarily a consequence of impaired venous return.

The most appropriate initial nursing assessment is to evaluate the patient's position and immediately assist her to a left lateral position. This is a critical, immediate, and non-invasive intervention. The assessment and action are intertwined here: recognizing the positional cause of the hypotension is the key assessment.

The physiological rationale is to mechanically displace the uterus off the great vessels. A left lateral tilt, or full left lateral recumbent position, uses gravity to shift the uterine weight away from the IVC, which runs slightly to the right of the spine. This relieves the compression, restores venous return, and typically resolves the hypotension and symptoms rapidly without the need for pharmacological intervention. The provided research abstract directly supports this concept, stating that the effectiveness of a 15° left-lateral tilt for alleviating IVC compression is a central clinical question, and it explores ultrasound-guided positioning to optimize this relief ^[1]. This confirms that positional management is the cornerstone of addressing IVC compression by the gravid uterus.

Option 1: Assess for signs of preeclampsia. While preeclampsia is a critical condition to monitor for in the third trimester, its typical presentation differs. Preeclampsia is characterized by hypertension (systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg), not acute hypotension. The sudden onset of symptoms upon assuming a supine position is the defining diagnostic clue for supine hypotensive syndrome, making a preeclampsia workup a secondary consideration after the immediate crisis is resolved.

Option 3: Check for vaginal bleeding and signs of placental abruption. Placental abruption can present with acute pain and may be associated with trauma or hypertension. While hypotension can occur with a severe abruption due to concealed hemorrhage, the clear positional trigger (lying supine) and the classic triad of dizziness, nausea, and faintness make aortocaval compression the far more likely and immediate cause. Repositioning the patient is a simple, rapid assessment that can rule out this life-threatening cause.

Option 4: Obtain a complete blood count to assess for anemia. Anemia is a chronic condition that could predispose a patient to feeling faint, but it does not explain the acute, dramatic drop in blood pressure upon a positional change. This would be an appropriate part of routine prenatal screening but is not the immediate priority for an acute hypotensive episode with a clear positional trigger.

This question tests your ability to prioritize nursing actions based on a rapid clinical assessment. The NCLEX-RN frequently presents scenarios where a simple, non-invasive intervention (like repositioning) is the correct first step before more complex assessments or diagnostic tests. Recognizing the direct link between the supine position, the physiological mechanism of aortocaval compression, and the sudden onset of hypotensive symptoms is a high-yield concept. The research on IVC/Ao ratios and left-lateral tilt positioning reinforces that this is not just a historical practice but a core physiological principle actively studied for optimization in obstetric anesthesia ^[1]. The immediate nursing response is always to remove the cause of the compression by repositioning the patient.