From the Guidelines
Supine hypotensive syndrome can be effectively managed by positioning pregnant women on their left side, which prevents mechanical compression of major blood vessels and maintains adequate venous return, cardiac output, and uteroplacental perfusion. This condition occurs when a pregnant woman lies flat on her back, causing the enlarged uterus to compress the inferior vena cava and aorta, reducing blood return to the heart and decreasing cardiac output, which leads to maternal hypotension and potential fetal distress. According to the 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1, manual left lateral uterine displacement effectively relieves aortocaval pressure in patients with hypotension.
To combat this condition, pregnant women should avoid lying flat on their backs, especially after 20 weeks gestation. The most effective intervention is positioning - women should lie on their left side when resting or sleeping, which shifts the uterus away from major blood vessels. If a supine position is necessary (such as during medical procedures), a wedge pillow should be placed under the right hip to create a 15-30 degree tilt, displacing the uterus laterally. For women experiencing symptoms (lightheadedness, nausea, dizziness), immediate repositioning to the left side typically resolves symptoms within minutes. No medications are typically required to treat this condition as it is positional in nature.
Key points to consider in managing supine hypotensive syndrome include:
- Avoiding the supine position, especially after 20 weeks gestation
- Positioning on the left side to prevent mechanical compression of major blood vessels
- Using a wedge pillow to displace the uterus laterally if a supine position is necessary
- Educating pregnant women about the importance of side-sleeping and proper positioning during rest, as emphasized in the European Society of Cardiology guidelines 1. Healthcare providers should prioritize these interventions to prevent maternal hypotension and potential fetal distress, and to maintain adequate uteroplacental perfusion.
From the Research
Description of Supine Hypotensive Syndrome
- Supine hypotensive syndrome is characterized by severe supine hypotension in late pregnancy, resulting from inferior vena cava compression by the gravid uterus 2, 3, 4.
- The syndrome can manifest with a range of symptoms, from minimal cardiovascular alterations to severe shock, and can be life-threatening in extreme cases 3.
- The compression of the inferior vena cava leads to a reduction in blood flow, which can cause a decrease in cardiac output and an increase in heart rate 2.
Hemodynamic Changes
- Studies have shown that women with supine hypotensive syndrome have reduced azygos venous flow rate compared to those without symptoms 2.
- The azygos vein plays a crucial role in providing collateral venous circulation in the event of acute inferior vena caval obstruction 5.
- Hemodynamic changes in response to positioning are similar across groups, including a reduction in inferior vena cava blood flow, reduction in cardiac output, and an increase in azygos blood flow 2.
Combating Supine Hypotensive Syndrome
- Establishing a left lateral tilt during labor and caesarean section is a fundamental principle of obstetric care, which can help to alleviate the symptoms of supine hypotensive syndrome 6.
- Providing vasopressor support during caesarean delivery under neuraxial anesthesia may also help to negate the negative effects of a maternal full supine position 6.
- Avoiding the supine position during late pregnancy, especially during sleep, may also help to reduce the risk of supine hypotensive syndrome and stillbirth 5.