During pregnancy, there is a notable rise in cardiac output (CO) and blood volume to accommodate the metabolic needs of both the mother and the developing fetus. Cardiac output typically increases by 30-50%, driven by elevated heart rate and stroke volume. This increase peaks in the third trimester, ensuring that critical organs such as the uterus, kidneys, and skin receive sufficient blood flow. However, while this rise in blood volume helps buffer against blood loss during delivery, it can make anesthesia management more challenging. Anesthesia providers must be vigilant, as symptoms of hypovolemia, such as low blood pressure or increased heart rate, may not become evident until significant blood loss has occurred. Monitoring these hemodynamic changes is particularly important during cesarean sections or procedures with the potential for substantial blood loss.
The increased blood volume, combined with the physical displacement of the heart by the growing uterus, can also lead to cardiovascular instability, especially when the patient is lying on her back. In the supine position, the uterus can compress the inferior vena cava, reducing venous return and lowering cardiac output, which can result in supine hypotensive syndrome. To prevent this, anesthesia providers should position the patient on her left side or place a wedge under her right hip for at least 15 degrees of left uterine displacement, tilting the uterus away from the vena cava. Additionally, anesthesia, particularly neuraxial anesthesia, can reduce systemic vascular resistance, which may further lower blood pressure. In such cases, vasopressors like phenylephrine may be needed to maintain adequate circulation and perfusion.
