Tuesday, November 28, 2023

Preeclampsia

Practice Essentials

Preeclampsia is a disorder of widespread vascular endothelial malfunction and vasospasm that occurs after 20 weeks’ gestation and can present as late as 4-6 weeks post partum. It is clinically defined by hypertension and proteinuria, with or without pathologic edema.

Definitions

Preeclampsia is defined as the presence of (1) a systolic blood pressure (SBP) greater than or equal to 140 mm Hg or a diastolic blood pressure (DBP) greater than or equal to 90 mm Hg or higher, on two occasions at least 4 hours apart in a previously normotensive patient, OR  (2) an SBP greater than or equal to 160 mm Hg or a DBP greater than or equal to 110 mm Hg or higher (In this case, hypertension can be confirmed within minutes to facilitate timely antihypertensive therapy.).

In addition to the blood pressure criteria, proteinuria of greater than or equal to 0.3 grams in a 24-hour urine specimen, a protein (mg/dL)/creatinine (mg/dL) ratio of 0.3 or higher, or a urine dipstick protein of 1+ (if a quantitative measurement is unavailable) is required to diagnose preeclampsia.

Preeclampsia with severe features is defined as the presence of one of the following symptoms or signs in the presence of preeclampsia
:

SBP of 160 mm Hg or higher or DBP of 110 mm Hg or higher, on two occasions at least 4 hours apart while the patient is on bed rest (unless antihypertensive therapy has previously been initiated)

Impaired hepatic function as indicated by abnormally elevated blood concentrations of liver enzymes (to double the normal concentration), severe persistent upper quadrant or epigastric pain that does not respond to pharmacotherapy and is not accounted for by alternative diagnoses, or both.

Progressive renal insufficiency (serum creatinine concentration >1.1 mg/dL or a doubling of the serum creatinine concentration in the absence of other renal disease)

New onset cerebral or visual disturbances

Pulmonary edema

Thrombocytopenia (platelet count < 100,000/μL)

In a patient with new-onset hypertension without proteinuria, the new onset of any of the following is diagnostic of preeclampsia:

Platelet count below 100,000/μL

Serum creatinine level above 1.1 mg/dL or doubling of serum creatinine in the absence of other renal disease

Liver transaminase levels at least twice the normal concentrations

Pulmonary edema

Cerebral or visual symptoms

Eclampsia is defined as seizures that cannot be attributable to other causes in a woman with preeclampsia. HELLP syndrome (hemolysis, elevated liver enzyme, low platelets) may complicate severe preeclampsia.

Risk factors

Risk factors for preeclampsia and their odds ratios are as follows
:

Nulliparity (3.1)

Age older than 40 years (3:1)

Black race (1.5:1)

Family history (5:1)

Chronic renal disease (20:1)

Chronic hypertension (10:1)

Antiphospholipid syndrome (10:1)

Diabetes mellitus (2:1)

Twin gestation (but unaffected by zygosity) (4:1)

High body mass index (3:1)

Homozygosity for angiotensinogen gene T235 (20:1)

Heterozygosity for angiotensinogen gene T235 (4:1)

Signs and symptoms

Because the clinical manifestations of preeclampsia can be heterogeneous, diagnosing preeclampsia may not be straightforward. Preeclampsia without severe features may be asymptomatic. Many cases are detected through routine prenatal screening.

Patients with preeclampsia with severe features display end-organ effects and may complain of the following:

Headache

Visual disturbances: Blurred, scintillating scotomata

Altered mental status

Blindness: May be cortical
or retinal

Dyspnea

Edema: Sudden increase in edema or facial edema

Epigastric or right upper quadrant abdominal pain

Weakness or malaise: May be evidence of hemolytic anemia

Clonus: May indicate an increased risk of convulsions

Diagnosis

All women who present with new-onset hypertension should have the following tests:

CBC

Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels

Serum creatinine

Uric acid

24-hour urine collection for protein and creatinine (criterion standard) or urine dipstick analysis

Additional studies to perform if HELLP syndrome is suspected are as follows:

Peripheral blood smear

Serum lactate dehydrogenase (LDH) level

Indirect bilirubin

Although a coagulation profile (prothrombin time [PT], activated partial thromboplastin time [aPTT], and fibrinogen) should also be evaluated, its clinical value is unclear when the platelet count is 100,000/mm3 or more with no evidence of bleeding.

Head CT scanning is used to detect intracranial hemorrhage in selected patients with any of the following:

Sudden severe headaches

Focal neurologic deficits

Seizures with a prolonged postictal state

Atypical presentation for eclampsia

Other procedures

Ultrasonography: Transabdominal, to assess the status of the fetus and evaluate for growth restriction; umbilical artery Doppler ultrasonography, to assess blood flow

Cardiotocography: The standard fetal nonstress test and the mainstay of fetal monitoring

Management

Delivery is the only cure for preeclampsia. Patients with preeclampsia without severe features are often induced after 37 weeks’ gestation. Before this, the patient is usually hospitalized and monitored carefully for the development of worsening preeclampsia or complications of preeclampsia, and the immature fetus is treated with expectant management with corticosteroids to accelerate lung maturity in preparation for early delivery.

In patients with preeclampsia with severe features, induction of delivery should be considered after 34 weeks’ gestation. In these cases, the severity of disease must be weighed against the risks of infant prematurity. In the emergency setting, control of BP and seizures should be priorities.

Criteria for delivery

Women with preeclampsia with severe features who are managed expectantly must be delivered under the following circumstances:

Nonreassuring fetal testing including (nonreassuring nonstress test, biophysical profile score, and/or persistent absent or reversed diastolic flow on umbilical artery Doppler velocimetry)

Ruptured membranes

Uncontrollable BP (unresponsive to medical therapy)

Oligohydramnios, with amniotic fluid index (AFI) of less than 5 cm

Severe intrauterine growth restriction in which the estimated fetal weight is less than 5%

Oliguria (< 500 mL/24 hr)

Serum creatinine level of at least 1.5 mg/dL

Pulmonary edema

Shortness of breath or chest pain with pulse oximetry of < 94% on room air

Headache that is persistent and severe

Right upper quadrant tenderness

Development of HELLP syndrome

Eclampsia

Platelet count less tha 100,000 cells/microL

Placental abruption

Unexplained coagulopathy

Seizure treatment and prophylaxis

The basic principles of airway, breathing, and circulation (ABC) should always be followed

Magnesium sulfate is the first-line treatment for primary and recurrent eclamptic seizures

Treat active seizures with IV magnesium sulfate
: A loading dose of 4 g is given by infusion pump over 5-10 minutes, followed by an infusion of 1 g/hr maintained for 24 hours after the last seizure

Treat recurrent seizures with an additional bolus of 2 g or an increase in the infusion rate to 1.5 or 2 g per hour

Prophylactic treatment with magnesium sulfate is indicated for all patients with preeclampsia with severe features

Lorazepam and phenytoin may be used as second-line agents for refractory seizures

Acute treatment of severe hypertension in pregnancy

Antihypertensive treatment is recommended for severe hypertension (SBP >160 mm Hg; DBP >110 mm Hg). The goal of hypertension treatment is to maintain BP around 140/90 mm Hg.

Medications used for BP control include the following:

Hydralazine

Labetalol

Nifedipine

Sodium nitroprusside (in severe hypertensive emergency refractory to other medications)

Fluid management

Diuretics should be avoided

Aggressive volume resuscitation may lead to pulmonary edema

Patients should be fluid restricted when possible, at least until the period of postpartum diuresis

Central venous pressure (CVP) or pulmonary artery pressure monitoring may be indicated in critical cases

A CVP of 5 mm Hg in women with no heart disease indicates sufficient intravascular volume, and maintenance fluids alone are sufficient

Total fluids should generally be limited to 80 mL/hr or 1 mL/kg/hr

Postpartum management

Many patients will have a brief (up to 6 hours) period of oliguria following delivery

Magnesium sulfate seizure prophylaxis is continued for 24 hours postpartum

Liver function tests and platelet counts must document decreasing values prior to hospital discharge

Elevated BP may be controlled with nifedipine or labetalol postpartum

If a patient is discharged with BP medication, reassessment and a BP check should be performed, at the latest, 1 week after discharge

Unless a woman has undiagnosed chronic hypertension, in most cases of preeclampsia, the BP returns to baseline by 12 weeks’ postpartum

Patients should be carefully monitored for recurrent preeclampsia, which may develop up to 4 weeks postpartum, and for eclampsia that has occurred up to 6 weeks after delivery

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