Cardiopulmonary Resuscitation (CPR) requires immediate adaptation when the patient is in the third trimester of pregnancy. Standard CPR guidelines must be modified due to the profound physiological changes that occur in late pregnancy. These adjustments are necessary to ensure effective blood circulation and oxygen delivery, which are compromised by the enlarged uterus. The primary goal of these modified techniques is to improve the chances of survival for both the mother and the fetus.
Understanding Aortocaval Compression
The need for adapted positioning stems from aortocaval compression, which occurs when a pregnant person lies flat on their back. The weight of the enlarged uterus, fetus, and amniotic fluid presses directly against two major blood vessels running along the spine: the inferior vena cava and the aorta.
The inferior vena cava is responsible for returning deoxygenated blood from the lower body to the heart. When the uterus compresses this vein, venous return is significantly reduced, meaning there is less blood available for the heart to pump. This decrease in blood flow renders standard chest compressions largely ineffective. If the heart has little blood to circulate, compressions will fail to provide adequate perfusion to the mother’s vital organs and the placenta.
Achieving the Left Lateral Displacement
The most important modification in CPR for a third-trimester patient is the relief of aortocaval compression, achieved through left lateral uterine displacement (LLUD) or a left lateral tilt. The objective is to physically shift the uterus and its contents off the major vessels and move them toward the patient’s left side.
Left lateral displacement can be accomplished using two primary methods. One method involves placing a firm wedge, rolled blanket, or specialized board under the patient’s right hip, which creates a tilt of approximately 15 to 30 degrees. This angle is sufficient to move the uterus while still allowing the patient to remain mostly supine for effective chest compressions. The chest must remain supported on a firm surface to prevent the tilt from interfering with the force and depth of the compressions.
Alternatively, if a tilting device is unavailable, manual displacement is performed. A rescuer must use one or two hands to continuously push or pull the abdomen and uterus to the patient’s left side throughout the resuscitation attempt. This manual technique is often preferred as it ensures the chest remains flat on a hard surface, allowing for uninterrupted, high-quality chest compressions. The displacement must be maintained without interruption until the patient is stable or advanced medical help takes over.
Adapting Chest Compressions and Airway Management
Once the patient is correctly positioned with left lateral displacement, the technique for chest compressions follows standard adult CPR guidelines. Compressions must be performed at a rate of 100 to 120 per minute, with a depth of at least two inches (five centimeters). High-quality compressions are paramount and should not be compromised by the effort to maintain the tilt or displacement.
Hand placement may need to be adjusted slightly higher on the sternum than usual, but the goal remains to compress the lower half of the breastbone. This adjustment helps avoid putting undue pressure on the elevated diaphragm and the underlying uterus. The rescuer must ensure that full chest recoil is allowed between compressions to maximize blood flow back into the heart.
Airway and breathing management requires specific attention due to the physiological changes of late pregnancy. Pregnant patients have an increased risk of aspiration (inhalation of stomach contents) because of hormonal changes and increased pressure from the uterus. Rescuers should prioritize effective airway protection and ventilation using 100% oxygen. If an advanced airway is not in place, the compression-to-ventilation ratio remains 30:2, though the priority must always be to minimize interruptions to chest compressions.