Definitions

Chronic hypertension: Blood pressure of 140/90 mm Hg before pregnancy or at less than 20 weeks' gestation. Gestational hypertension: Hypertension without proteinuria at greater than 20 weeks' gestation. Preeclampsia: Hypertension with proteinuria (>300 mg over 24 hr) at a gestational age greater than 20 weeks, caused by vasospasm. Eclampsia: Seizure disorder associated with preeclampsia. Severe preeclampsia: Vasospasm associated with preeclampsia of such extent that maternal end organs are threatened, usually necessitating delivery of the baby regardless of gestational age. Superimposed preeclampsia: Development of preeclampsia in a patient with chronic hypertension.

Clinical Approach

Hypertensive disorders complicate 3% to 4% of pregnancies and can be organized into several categories: gestational hypertension, mild and severe preeclampsia, chronic hypertension, superimposed preeclampsia, and eclampsia. Gestational hypertensive patients have only increased blood pressures without proteinuria. Chronic hypertension includes preexisting hypertension or hypertension that develops prior to 20 weeks' gestation. A patient with chronic hypertension is at risk for developing preeclampsia; if preeclampsia develops, her diagnosis is labeled superimposed preeclampsia. Eclampsia occurs when the patient with preeclampsia develops convulsions or seizures.

Preeclampsia is characterized by hypertension and proteinuria. Although not a criterion, nondependent edema also is usually present. An elevated blood pressure is diagnosed with a systolic blood pressure at or higher than 140 mm Hg or diastolic blood pressure at or higher than 90 mm Hg. Two elevated blood pressures, measured 6 hours apart (measurements taken in the seated position), are needed for diagnosis of preeclampsia. Proteinuria usually is based on a timed urine collection, defined as equal to or greater than 300 nig of protein in 24 hr. Facial and hand edema would be considered non-dependent edema.

Preeclampsia is further categorized into mild and severe. Severe disease is diagnosed with a systolic blood pressure at or higher than 160 mm Hg. diastolic blood pressure 110 mm Hg or higher, or 24-hr urine protein level greater than 5 g. If there is no time for a 24-hr urine protein collection (i.e., while in labor), a urine dipstick helps estimate proteinuria, with 3 to 4+ consistent with severe disease and 1 to 2+ with mild disease. Patients also can be diagnosed with severe disease when symptoms of preeclampsia occur, such as headache, right upper quadrant or epigastric pain, and vision changes.

The underlying pathophysiology of preeclampsia is vasospasm and "leaky vessels," but its origin is unclear. It is cured only by termination of the pregnancy, and the disease process almost always resolves after delivery. Vasospasm and endothelial damage result in leaking between the endothelial cells and cause local hypoxemia of tissue. Hypoxemia leads to hemolysis, necrosis, and other end-organ damage. Patients usually are unaware of the hypertension and proteinuria, and typically the presence of symptoms indicates severe disease. Hence, one of the important roles of prenatal care is to identify patients with hypertension and proteinuria prior to severe disease. Complications of preeclampsia include placenta abruption, eclampsia (with possible intracerebral hemorrhage), coagulopathies, renal failure, hepatic subcapsular hematoma, hepatic rupture, and uteroplacental insufficiency.

Risk factors for preeclampsia include nulliparity, extremes of age, African-American race, personal history of severe preeclampsia, family history of preeclampsia, chronic hypertension, chronic renal disease, antiphospholipid syndrome, diabetes, and multifetal gestation. The history and physical examination

Table 25-1

CRITERIA FOR SEVERE PREECLAMPSIA

END ORGAN

(by system) SIGNS AND SYMPTOMS OF PREECLAMPSIA

Neurologic Headache

Vision changes Seizures Hyperreflexia Blindness

Renal Decreased glomerular nitration rate

Proteinuria Oliguria

Pulmonary Pulmonary edema

Hematologic and vascular Thrombocytopenia

Microangiopathic anemia Coagulopathy

Severe hypertension (160/110 mm Hg) Fetal Intrauterine growth restriction (IUGR)

Oligohydramnios

Decreased uterine perfusion (i.e., late decelerations) Hepatic Increased liver enzymes

Subcapsular hematoma Hepatic rupture are focused on end-organ disease (Table 25-1). It is important to review and evaluate the blood pressures prior to 20 weeks' gestation (to assess for chronic hypertension), evaluate proteinuria, and document any sudden increase in weight (indicating possible edema). On physical examination serial blood pressures should be checked, along with a urinalysis.

Laboratory tests should include a complete blood count (check platelet count and hemoconcentration), urinalysis, 24-hr urine protein collection if possible (check for proteinuria), liver function tests, lactate dehydrogenase (elevated with hemolysis), and uric acid (usually increased with preeclampsia). A non-stress test also can be performed to rule out uteroplacental insufficiency, along with an ultrasound to evaluate amniotic fluid volume.

After the diagnosis is made, management depends on the gestational age of the fetus and the severity of disease (see Figure 25-1 for one management scheme). Delivery is the definitive treatment, and the risks of preeclampsia must be weighed against the risk of prematurity. When the pregnancy is at term, delivery is indicated. When the fetus is premature, the severity of the disease must be assessed. When severe preeclampsia is diagnosed, delivery usually is indicated

Figure 25-1. Algorithm for management of preeclampsia.

regardless of gestational age. In preterm patients, mild preeclampsia can be monitored closely for worsening disease until the risk of prematurity has decreased.

Eclampsia is one of the most feared complications of preeclampsia, and the greatest risk for occurrence is just prior to delivery, during labor (intrapartum), and within the first 24 hr postpartum. During labor, the patient should be started on the anticonvulsant magnesium sulfate. Because magnesium is excreted by the kidneys, monitoring urine output, respiratory depression, dyspnea (side effect of magnesium sulfate is pulmonary edema), and abolition of the deep tendon reflexes (first sign of toxic effects is hyporeflexia) is important. Hypertension is not affected by magnesium, which is used to prevent seizures. Severe hypertension must be controlled with antihypertensive medications, such as hydralazine or labetalol. After delivery. MgS04 is discontinued approximately 24 hr postpartum. The hypertension and proteinuria frequently will resolve. Occasionally, the patient's blood pressure remains high, and an antihypertensive medication is needed after delivery. After discharge. the patient usually returns for follows-up in I to 2 weeks to check blood pressures and proteinuria.

Comprehension Questions

[25.1] Which of the following is a criterion for severe preeclampsia?

A. Elevated uric acid levels

B. 5 g of proteinuria excreted in a 24-hr period

C. 4+ pedal edema

D. Platelet count of 105,000/mm3

[25.2] Which of the following is the best management of a 18-year-old G1 PO woman at 28 weeks' gestation with a blood pressure of 160/110 mm Hg, elevated liver function tests, and platelet count of 60,000/mm3?

A. Oral antihypertensive therapy

B. Platelet transfusion

C. Magnesium sulfate therapy and induction of labor

D. Intravenous immunoglobulin therapy

[25.3] Which of the following is the most common mechanism whereby eclampsia leads to maternal mortality?

A. Intracerebral hemorrhage

B. Myocardial infarction

C. Electrolyte abnormalities

D. Aspiration

[25.4] A 33-year-old woman at 29 weeks' gestation is noted to have blood pressures of 150/90 and 2+ proteinuria. Platelet count and liver function tests were normal. Which of the following is the best management for this patient?

A. Induction of labor

B. Cesarean section

C. Antihypertensive therapy

D. Expectant management

Answers

[25.11 B. Pedal edema is not pathologic; nondependent edema, such as of the face and hands, is of more concern.

[25.2| C. Although the pregnancy is only 28 weeks, in light of the severe preeclampsia, the best treatment is delivery.

[25.3] A. The most common cause of maternal death due to eclampsia is intracerebral hemorrhage.

[25.4] I). In the preterm patient with mild preeclampsia, expectant management is used.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

Get My Free Ebook


Post a comment