Aortocaval compression syndrome

Condition caused by compression of the abdominal aorta and inferior vena cava

Aortocaval compression syndrome, also known as supine hypotensive syndrome, is a medical condition that occurs when the abdominal aorta and the inferior vena cava are compressed by the weight of the uterus in a pregnant woman when she is in a supine position. This compression can lead to a decrease in venous return to the heart, resulting in reduced cardiac output and hypotension.

Pathophysiology

Supine hypotensive syndrome

The condition primarily affects pregnant women, particularly in the third trimester, when the uterus is significantly enlarged. When a pregnant woman lies on her back, the weight of the uterus can compress the inferior vena cava, which is the large vein that carries deoxygenated blood from the lower body back to the heart. This compression reduces the amount of blood returning to the heart, leading to decreased cardiac output and a drop in blood pressure.

In addition to the inferior vena cava, the abdominal aorta can also be compressed, although it is less susceptible due to its thicker walls and higher pressure. The combination of these compressions can lead to significant circulatory changes, affecting both the mother and the fetus.

Symptoms

Symptoms of aortocaval compression syndrome can include:

• Dizziness or lightheadedness
• Nausea
• Sweating
• Pallor
• Tachycardia
• Hypotension

In severe cases, the condition can lead to syncope (fainting) and may compromise fetal circulation, potentially leading to fetal distress.

Diagnosis

Diagnosis of aortocaval compression syndrome is primarily clinical, based on the presence of symptoms when the patient is in a supine position and their resolution upon repositioning. It is important to differentiate this condition from other causes of hypotension in pregnancy.

Management

The primary management strategy for aortocaval compression syndrome is positional. Pregnant women are advised to avoid lying flat on their backs, especially in the later stages of pregnancy. Instead, they should lie on their left side, which helps to relieve the pressure on the inferior vena cava and improve venous return.

In cases where the patient must be supine, such as during certain medical procedures, a wedge or pillow can be placed under the right hip to tilt the uterus to the left, reducing compression.

Prevention

Preventive measures include educating pregnant women about the importance of avoiding the supine position during the third trimester and encouraging side-lying positions during rest and sleep.

Related pages

• Pregnancy
• Hypotension
• Cardiac output
• Inferior vena cava