NCLEX Review Guide: Supine Hypotension (Vena Cava Syndrome)

Understanding Supine Hypotension

• Supine hypotension (vena cava syndrome) occurs when the gravid uterus compresses the inferior vena cava when the pregnant woman lies flat on her back, typically after 20 weeks gestation. This compression reduces venous return to the heart, decreasing cardiac output by up to 25-30%.
• The condition is most pronounced in the third trimester when the uterus is largest and heaviest, though it can occur as early as the second trimester in some women.

Maternal Manifestations

• Immediate symptoms include dizziness, lightheadedness, nausea, and feeling faint when lying supine. The mother may experience pallor, diaphoresis, and a rapid, weak pulse as compensatory mechanisms activate.
• Blood pressure drops significantly (systolic BP may decrease by 30+ mmHg), and the mother may experience shortness of breath and anxiety due to decreased cardiac output.

Fetal Effects

• Fetal hypoxia can occur rapidly due to decreased placental perfusion from reduced maternal cardiac output. This manifests as late decelerations, decreased variability, or bradycardia on fetal heart rate monitoring.
• Prolonged supine positioning can lead to uteroplacental insufficiency and potential fetal compromise if not corrected promptly.

Immediate Actions

1. Position change is priority - Turn patient to left lateral position immediately to relieve vena cava compression
2. Elevate legs if possible to promote venous return
3. Assess vital signs and fetal heart rate continuously
4. Administer oxygen if indicated to improve maternal and fetal oxygenation
5. Establish IV access if not already present for potential fluid resuscitation

Prevention Strategies

• Educate all pregnant women after 20 weeks to avoid prolonged supine positioning and encourage left lateral positioning for rest and sleep.
• During procedures requiring supine positioning, place a wedge or pillow under the right hip to tilt the uterus off the vena cava (15-30 degree left lateral tilt).