Why is a pregnant patient placed in the left lateral decubitus position during Cardiopulmonary Resuscitation (CPR)?

From the Guidelines

Pregnant patients should be positioned on their left side during CPR to prevent compression of the inferior vena cava by the gravid uterus, which is known as aortocaval compression syndrome. This positioning is specifically recommended for pregnant women beyond 20 weeks gestation. To achieve this during CPR, manual displacement of the uterus to the left should be performed while the patient remains supine, or a wedge (such as a rolled towel or specialized device) should be placed under the right hip to create a 15-30 degree left lateral tilt. This positioning helps maintain venous return to the heart, improving cardiac output during resuscitation efforts. When the pregnant uterus compresses the inferior vena cava in the supine position, it reduces blood return to the heart by up to 30-40%, significantly compromising circulation for both mother and fetus. Additionally, this left lateral tilt position facilitates better perfusion to the placenta, which is critical for fetal survival during maternal cardiac arrest. Standard CPR chest compressions should still be performed on the sternum while maintaining this left lateral tilt.

The most recent and highest quality study, 1, suggests that there is insufficient evidence to make a recommendation about the use of left-lateral tilt or uterine displacement during CPR in the pregnant patient. However, based on the principles of maintaining venous return and cardiac output, and considering the potential benefits of left lateral tilt in preventing aortocaval compression syndrome, it is reasonable to recommend this positioning during CPR for pregnant women beyond 20 weeks gestation.

Some key points to consider when positioning a pregnant patient during CPR include:

• Manual displacement of the uterus to the left or use of a wedge to create a 15-30 degree left lateral tilt
• Maintaining standard CPR chest compressions on the sternum while in the left lateral tilt position
• Considering the potential benefits of left lateral tilt in preventing aortocaval compression syndrome and improving placental perfusion
• Being aware of the potential challenges and limitations of performing CPR in a pregnant patient, including the risk of aortocaval compression syndrome and the importance of maintaining adequate venous return and cardiac output.

It is also important to note that the American Heart Association guidelines, 1, recommend manual left lateral uterine displacement to relieve aortocaval pressure in patients with hypotension, and that airway, ventilation, and oxygenation are particularly important in the setting of pregnancy due to increased maternal metabolism and decreased functional reserve capacity.

Overall, the recommendation to position pregnant patients on their left side during CPR is based on the principles of maintaining venous return and cardiac output, and preventing aortocaval compression syndrome, and is supported by the available evidence, including 1, 1, and 1.

From the Research

Rationale for Laying Pregnant Patient on Left Side During CPR

• The primary reason for laying a pregnant patient on their left side during CPR is to minimize aortocaval compression, which occurs when the gravid uterus compresses the inferior vena cava and aorta, leading to reduced blood flow and cardiac output 2, 3, 4.
• This compression can cause a decrease in venous return, cardiac output, and blood pressure, making it essential to relieve the compression to ensure adequate blood flow and oxygenation to the mother and fetus 3, 4.
• The left lateral tilt position helps to shift the uterus to the left, relieving the compression on the inferior vena cava and aorta, and allowing for improved blood flow and cardiac output 2, 4.

Hemodynamic Changes in Pregnant Patients

• Studies have shown that pregnant patients who experience supine hypotensive syndrome have reduced ability to compensate for the effects of supine positioning, leading to significant reductions in azygos venous flow rate and cardiac output 3.
• The use of left lateral tilt positioning has been shown to increase the diameter of the inferior vena cava, allowing for improved blood flow and cardiac output 4.
• However, some studies have found that a quarter of patients may have a decrease in inferior vena cava diameter with tilting, suggesting that uterine compression of the inferior vena cava may not occur universally 4.

Clinical Implications

• The American Heart Association recommends that pregnant patients in cardiac arrest be placed in a left lateral tilt position to relieve aortocaval compression and improve blood flow and cardiac output 5.
• Interdisciplinary simulation training units can help to qualify specialized emergency teams to respond to cardiocirculatory incidents during pregnancy, including the use of left lateral tilt positioning during CPR 5.
• Understanding the anatomy of the collateral venous system, including the azygos system, is essential for managing pregnant patients with supine hypotension and preventing stillbirth 6.