Preeclampsia and Eclampsia

Definition

Preeclampsia and eclampsia are hypertensive disorders of pregnancy that occur in 5-10% of pregnancies. In developing countries, hypertensive disorders of pregnancy are the single most common cause of death in childbirth. Preeclampsia is defined by the presence of three elements: hypertension, proteinuria (protein in the urine), and edema (fluid retention). If seizures develop following the appearance of the first three factors, the condition is called eclampsia.

Description

The cause of preeclampsia is unknown, but is thought to be an immunologic disorder of some kind. Preeclampsia is more likely to develop in primigravidas (women in their first pregnancy); in women who have used barrier methods of contraception; in women who have new sexual partners; and in women whose birth parents have similar HLA antigens. Other risk factors include a family history of preeclampsia; age extremes in the mother (younger than 20 years or older than 40); preexisting kidney disease or vascular disorder; diabetes; multiple pregnancy; five or more previous pregnancies; African American descent; and genetic abnormalities in the fetus. Since the 1980s, preeclampsia has been associated with poor blood supply to the placenta or placental dysfunction, but the stages in the development of the disorder between damage to the placenta and the appearance of hypertension are not yet fully understood.

Hypertensive disorders of pregnancy affect six major systems or sites in the body: the central nervous system (CNS); kidneys; liver; the blood; the blood vessels; and the fetus and placenta. In severe cases, the mother may suffer liver failure, rupture of the liver, or pulmonary edema (fluid in the lungs ); the fetus may die.

Classification of hypertensive disorders of pregnancy

The most common classification used to define hypertensive disorders of pregnancy is the one recommended by the American College of Obstetricians and Gynecologists (ACOG) and endorsed by the NIH Working Group on High Blood Pressure:

• Chronic hypertension, defined as blood pressure greater than or equal to 140 mm Hg systolic or 90 mm Hg diastolic present prior to pregnancy or before the 20th week of pregnancy. During pregnancy the hypertension remains, but proteinuria does not occur. Women who develop hypertension during pregnancy, without proteinuria or seizures, and whose blood pressure remains elevated after pregnancy are also diagnosed with chronic hypertension.
• Gestational hypertension, defined as elevated blood pressure greater than or equal to 140 mm Hg systolic or 90 mm Hg diastolic that arises after midpregnancy with no proteinuria. Blood pressure returns to normal by 12 weeks postpartum. Final diagnosis of this condition is delayed until the postpartum period. If the patient does not develop preeclampsia, and her blood pressure returns to normal, the final diagnosis is transient hypertension of pregnancy. If her blood pressure remains elevated, a diagnosis of chronic hypertension is given.
• Preeclampsia and eclampsia. Preeclampsia is characterized by blood pressure greater than or equal to 140 mm Hg systolic or 90 mm Hg diastolic occurring after midpregnancy (20 weeks gestation), and accompanied by proteinuria. Preeclampsia may be further categorized as mild or severe. A woman is considered to have severe preeclampsia when her blood pressure reading is 160+ mm Hg systolic or 110+ mm Hg diastolic; her proteinuria is equal to or greater than 5 mg of protein in the urine per 24 hours; or other organ systems are involved. She may have headache, visual disturbances, or other CNS symptoms; pulmonary edema, cyanosis, or other cardiovascular symptoms; and abdominal pain.
• Preeclampsia superimposed on chronic hypertension. Pregnant women with preexisting chronic hypertension may develop preeclampsia. Superimposed preeclampsia is suspected when proteinuria develops or increases suddenly; when previously controlled hypertension exhibits a sudden increase; or when the patient develops thrombocytopenia or elevated liver enzyme levels. Women with preeclampsia superimposed on chronic hypertension have a poorer prognosis than women with either condition alone.

Measurement of blood pressure

For purposes of accuracy and standardization, health professionals should take blood pressure measurements in pregnant women with the patient seated rather than lying on her side, because substantial differences exist between the blood pressures in the upper and lower arms when the patient is lying on her side. In addition, the National Institutes of Health (NIH) recommends that the diastolic pressure reading should be taken at Korotkoff 5, with the disappearance of sound—not at Korotkoff 4, when sound becomes muffled. To meet strict criteria for hypertension, the patient's readings must be elevated on at least two separate occasions at least six hours apart.

Causes and symptoms

As previously mentioned, the initial cause of preeclampsia/eclampsia is not known but is thought to be immunologic. The relationship among the three factors that define preeclampsia appears to be as follows. First, the normal increase in blood plasma volume and decrease in peripheral vascular resistance that occur during an uncomplicated pregnancy are absent. The patient's blood vessels allow fluid to leak from the vessels into the surrounding tissue, which results in edema. The seizures that characterize eclampsia result from edema of the brain. The patient's kidneys are under stress because of diminished blood flow through the kidneys and decreased filtration. This process allows protein molecules to spill over into the urine. Damage to the kidneys lowers urine output and increases the levels of sodium in body tissues. Higher concentrations of sodium result in increased fluid retention. Protein lost through the urine also affects the movement of fluid into the tissues, further increasing fluid retention.

The HELLP syndrome

A liver condition related to hypertension in pregnancy is called the HELLP syndrome, which occurs in about 1:150 births. HELLP stands for hemolysis, elevated liver enzymes, and low platelet count. Normal liver functioning is altered in the HELLP syndrome as a result of vascular damage related to preeclampsia. Researchers believe that the fetus and mother share a defect in processing fatty acids that leads to destruction of red blood cells, inflammation of the liver, and decreased platelet count. HELLP syndrome is associated with disseminated intravascular coagulation (DIC); placental abruption (sudden tearing); acute renal failure; and pulmonary edema. About 30% of pregnancy-related cases of HELLP develop in the postpartum period.

Disseminated intravascular coagulation

Preeclampsia and eclampsia may also be associated with the serious condition known as disseminated intravascular coagulation, or DIC. DIC is a disorder characterized by both bleeding and thrombosis (the formation of intravascular clots). Maternal hemorrhage is a risk in patients with preeclampsia who develop DIC. About 15% of hypertension-related deaths in pregnancy are associated with DIC.

Diagnosis

The diagnosis of preeclampsia is complicated by the fact that the signs of hypertension in pregnancy can be easily confused with the symptoms of chronic hypertension, gallbladder and pancreatic diseases, and other disorders. Since prevention of maternal and fetal morbidity and mortality is of the utmost priority, however, the NIH recommends overdiagnosis of preeclampsia rather than underdiagnosis to ensure careful management. Pregnant women should have their weight, blood pressure, and urine checked at every prenatal visit. Regular prenatal visits are extremely important, as the early symptoms of preeclampsia cause no discomfort. The NIH guidelines suggest that women who develop an increase of 30 mmHg systolic or 15 mmHg diastolic over their prenatal baseline measurements should be closely monitored, especially if their protein or uric acid levels are elevated. Early detection of preeclampsia allows for proper management of the condition.

Treatment

Pre-delivery management

Delivery is the definitive treatment of preeclampsia. Even mild preeclampsia that develops at 36 weeks of gestation or later is managed by delivery. Prior to 36 weeks, severe preeclampsia requires delivery of the fetus. Mild to moderate preeclampsia between 20 and 36 weeks is treated with bed rest. Rest increases central blood flow to the patient's heart, kidneys, placenta, and other organs. Bed rest at home is an option for some patients with mild preeclampsia and stable home situations. Patients with severe eclampsia or unstable family situations require hospitalization. Monitoring of fetal heart rate and lung maturity is an important part of the management of preeclampsia.

Medications

Medication for preeclampsia is usually directed toward preventing convulsions rather than controlling blood pressure. Magnesium sulfate is the drug of choice for controlling seizures during pregnancy. Prophylactic magnesium sulfate administration may continue into the postpartum period.

Emergency care

The primary concern in emergency treatment of convulsions is to assure the patient's safety. The patient is placed on her side to allow any secretions in the mouth to drain, thus decreasing the risk of aspiration. In addition, this position improves blood flow to the placenta and fetus. Delivery of the fetus usually follows as soon as possible after the convulsion to minimize the risk of placental abruption.

Vaginal delivery is preferred to caesarean delivery in order to avoid the additional stress of surgery on the patient's organ systems. The NIH recommends a trial of labor induction, regardless of the condition of the patient's cervix. Magnesium sulfate may be given as an anticonvulsant. Antihypertensive medication is restricted to use for sudden elevations of blood pressure, or if the patient's diastolic pressure reaches 105 to 110 mm Hg.

Prognosis

Risks to the fetus from preeclampsia include intrauterine growth retardation and low birth weight, placental abruption, and stillbirth. The fetus may be delivered prematurely if the condition of the mother deteriorates. Risks to the mother include vascular organ damage; the additional risks of eclampsia include convulsions and accompanying oxygen deprivation, hemorrhage in the brain, temporary blindness, permanent neurological damage, liver or kidney damage, cerebrovascular and cardiovascular complications, and even death. The prognoses for both the fetus and mother are excellent in mild preeclampsia. If blood pressure readings are within normal limits after several weeks postpartum, the mother may still be at increased risk of hypertension later in life, and should have her blood pressure checked yearly.

The long-term prognosis for children born to preeclamptic mothers is not yet known. These individuals do, however, appear to be at increased risk of chronic disease in adult life.

Health care team roles

The responsibilities of nursing staff in the management of preeclampsia and eclampsia include patient education and monitoring of patient compliance with the physician's instructions as well as assisting with emergency care. Patients resting at home should be visited and assessed periodically by a home health nurse. These functions are essential to good management of high-risk patients. Providing emotional support to patients with complications during pregnancy is also a critical function. If the patient requires hospitalization, a calm and quiet environment can help decrease the risk of seizure.

Prevention

Since the cause of preeclampsia is unclear, prevention focuses on early detection and management to avoid progression. Bed rest improves blood flow to the placenta and to maternal organs. Lying on the side increases sodium excretion and decreases fluid retention through increased diuresis. Magnesium sulfate may be given to lessen the risk of convulsions.

Recent clinical trials appear to indicate that some preventive strategies do not benefit most patients at risk for preeclampsia. These strategies include the prophylactic administration of heparin, calcium, or aspirin; and supplemental doses of fatty acids.

KEY TERMS

Cyanosis— A bluish color to the skin that indicates poor circulation and poor oxygenation of the blood and tissues.

Disseminated intravascular coagulation (DIC)— A disorder of blood coagulation characterized by both bleeding and thrombosis (intravascular clotting).

Edema— Abnormal accumulation of fluid in the tissues, cavities, or joint capsules of the body. It is one of three important indications of preeclampsia.

HELLP— A syndrome related to liver dysfunction that develops in some patients with preeclampsia. The letters stand for Hemolysis, Elevated Liver enzyme levels, and Low Platelet count.

Oliguria— Minimal urine output, usually defined as 500 ml or less over a 24-hour period.

Placental abruption— Sudden rupture or tearing of the placenta. The convulsions that characterize eclampsia increase the risk of placental abruption.

Proteinuria— A significant amount of protein in the urine. It is also sometimes called albuminuria.

Thrombocytopenia— A blood platelet count below 100,000 cells/mm³.

Resources

BOOKS

Burrow, Gerard N., and Thomas P. Duffy. Medical Complications During Pregnancy, 5th ed. Philadelphia: W. B. Saunders Company, 1999.

Creasy, Robert K., and Robert Resnik. Maternal-Fetal Medicine, 4th ed. Philadelphia: W. B. Saunders Company, 1999.

Crombleholme, William J., MD. "Obstetrics." In Lawrence M. Tierney, MD, et al., eds., Current Medical Diagnosis & Treatment 2001. New York: Lange Medical Books, 2001.

Fausett, M. Bardett, MD, and Michael A. Belfort, MD. "Hypertensive Disorders of Pregnancy." In Conn's Current Therapy 2001, edited by Robert E. Rakel, MD and Edward T. Bope, MD. Philadelphia: W. B. Saunders Company, 2000.

Feinbloom, Richard I. Pregnancy, Birth, and the Early Months: The Thinking Woman's Guide, 3rd ed. Cambridge, MA: Perseus Publishing, 2000.

Pillitteri, Adele. Maternal & Child Health Nursing: Care of the Childbearing & Childrearing Family, 3rd ed. Philadelphia: Lippincott, 1999.

ORGANIZATIONS

American College of Obstetricians and Gynecologists. 409 12th St., S.W., PO Box 96920, Washington, D.C. 20090-6920. 〈http://www.acog.com〉.