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Hypertension in Pregnancy

Hypertensive disease complicates 6-8% of all pregnancies in the United States and is one of the major causes of maternal death. It is also an important cause of perinatal morbidity and mortality.

Terminology

Terminology used to describe hypertension in pregnancy is nonuniform, confusing, and steeped in tradition. Several overlapping terms are commonly applied to varying clinical manifestations of the same disease process. A variety of classifications have been proposed and used in the past. However, in clinical practice two distinct entities are commonly encountered in pregnant women: chronic hypertension and PIH. These two conditions may coexist; in fact, the risk of developing PIH is significantly increased in women with underlying chronic hypertension. Pregnancy-induced hypertension is a multiorgan disease process that may involve much more than elevated blood pressure. Several clinical subsets are recognized, depending on end-organ effects. Some such subsets have traditionally been given distinct labels, for example, preeclarnpsia when renal involvement leads to proteinuria, eclarnpsia when central nervous system involvement leads to seizures, and more recently, HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome when the clinical picture is dominated by hematologic.

Hypertension is defined as a sustained blood pressure increase to levels of 140 mm Hg systolic or 90 mm Hg diastolic. Blood pressure may depend greatly on patient position; ideally, measurements should be taken.

Clinical Manifestations of Severe Disease in Patients with Pregnancy-Induced

Hypertension

• Blood pressure >160-180 mm Hg systolic or

>110 mm Hg diastolic

• Proteinuria >5 g/24 h (normal <300 mg/24 h)

• Elevated serum creatinine

• Grand real seizures (eclampsia)

• Pulmonary edema

Oliguria <500 mL/24 h

• Microangiopathic hemolysis

• Thrombocytopenia

• Hepatocellular dysfunction (elevated alanine aminotransferase, aspartase)

• Intrauterine growth restriction or oligohydramnios

• Symptoms suggesting significant end-organ involvement: headache, visual disturbances, or epigastric or right-upper-quadrant pain

Clinical Treatment

Delivery is always an appropriate option in the term patient with hypertension. However, in the patient with an unfavorable cervix who exhibits only mild blood pressure elevations, minimal proteinuria, and no evidence of either maternal end-organ involvement or fetal compromise, it may be appropriate to delay delivery.

Delivery should be considered in women who have signs and symptoms of severe PIH at 32-34 weeks of gestation. In some cases, the condition of women who initially manifest signs and symptoms of severe PIH will improve.

Management of severe PIH at less than 28 weeks of gestation poses a difficult clinical dilemma because it is often unsuccessful and may be hazardous. Attempts at conservative management in women with severe PIH at 18-27 weeks of gestation have been associated with significant morbidity.

In women who develop PIH before 34 weeks of gestation, consideration should be given to screening for the presence of antiphospholipid antibodies. Such antibodies portend an increased risk of adverse outcome.

For the preterm patient with mild PIH, conservative management is generally indicated. For any patient with PIH who is not undergoing delivery, it is essential to closely monitor blood pressure and proteinuria and evaluate renal and hepatic function and platelet count. Serial sonography for fetal growth and antepartum assessment of fetal well-being.

When delivery is indicated, parenteral magnesium sulfate generally is administered to prevent seizures. This is most commonly given as an intravenous loading bolus followed by a continuous infusion administered via a controlled infusion device. Infusion of magnesium sulfate should be discontinued and a serum magnesium level should be obtained in any patient with loss of deep tendon reflexes, a respiratory rate of less than 12 per minute, and a decrease in urinary output to below 25 mL/h. Magnesium sulfate can also be given intramuscularly.

Several antihypertensive agents have been used to control maternal blood pressure during labor to reduce the risk of cerebral accident. When blood pressure exceeds 110 mm Hg diastolic or 180 mm Hg systolic, consideration should be given to lowering the blood pressure. One widely used agent is hydralazine hydrochloride given intravenously.

Delivery is indicated for any patient with persistent severe oliguria. If treatment is required before or after delivery, a fluid challenge may be given. If severe oliguria is unresponsive to a fluid challenge, additional volume may be withheld.