Hypertensive Disorders of Pregnancy and Nursing Considerations

Preeclampsia is a multisystem disorder that occurs during pregnancy after 20 weeks of gestation or during the postpartum period. It’s characterized by new-onset hypertension, proteinuria, and end-organ dysfunction, or damage to major organs like the kidneys, liver, brain, and placenta. Eclampsia occurs when a patient with preeclampsia develops generalized seizures.

When it comes to blood pressure regulation during pregnancy, there are three key factors to keep in mind: cardiac output, which is the amount of blood the heart pumps out to the systemic circulation in one minute; intravascular volume, which is the amount of blood in the circulation; and peripheral vascular resistance, which is the resistance of blood flow in peripheral arteries.

During pregnancy, the cardiac output and intravascular volume increase but the peripheral vascular resistance decreases. That’s because there’s a relative decrease in the response to vasoconstrictor molecules, like angiotensin II, and there are also higher levels of vasodilator molecules, like prostacyclin PGI2. As a result, blood vessels dilate to accommodate the increased blood volume, and this keeps blood pressure in a normal range.

Now, the exact cause of preeclampsia is not well understood, but it seems to begin with abnormal implantation and vascularization of the placenta, as early as the first trimester. During this time, the spiral arteries, which are usually highly dilated vessels that supply the placenta and fetus with a rich supply of blood, become constricted. This results in placental hypoxia, which is followed by a release of chemical mediators that cause systemic vascular endothelial dysfunction and vasospasm, thereby decreasing perfusion to target organs such as the kidneys, liver, and brain.

In the placenta, decreased perfusion means low blood flow to the developing fetus, which can cause intrauterine growth restriction, low birth weight, preterm birth, or even fetal death. Additionally, preeclampsia increases the risk of placental abruption, meaning the placenta prematurely detaches from the uterine wall.

In the kidneys, decreased perfusion can damage the glomeruli that normally work to keep blood proteins from making their way into the urine, resulting in proteinuria. With less protein in the blood, generalized or localized edema may occur, like pulmonary edema. Over time, low renal blood flow can also lead to renal insufficiency.

In the liver, decreased perfusion can cause liver damage and dysfunction. And because the liver is in charge of conjugating bilirubin, hyperbilirubinemia may develop. In addition, the liver is full of enzymes used for various metabolic processes that can be released into the blood when the liver is damaged.

And let’s not forget about the brain! Vasoconstriction of cerebral blood vessels can lead to loss of circulatory autoregulation, disruption to the blood-brain barrier, and cerebral edema. This could play a role in the development of seizures and the progression of preeclampsia to eclampsia, as well as increasing the risk of cerebral ischemia, hemorrhage, and stroke.