Pre-eclampsia & Eclampsia for USMLE Step 2
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Pre-eclampsia & Eclampsia for the USMLE Step 2 Exam
Overview of Pre-eclampsia and Eclampsia
- Definitions:
- Pre-eclampsia: Hypertension (≥140/90 mmHg) after 20 weeks’ gestation with proteinuria (≥300 mg/24 hours or protein/creatinine ratio ≥0.3) or signs of systemic organ dysfunction.
- Eclampsia: New-onset seizures in a patient with pre-eclampsia, without other causes for the seizures.
- Classification of Pre-eclampsia:
- Mild: Blood pressure <160/110 mmHg, no severe symptoms.
- Severe: Blood pressure ≥160/110 mmHg or signs of end-organ damage such as severe headache, visual changes, or pulmonary edema.
Pathophysiology
- Abnormal Placental Development:
- Impaired trophoblastic invasion and remodeling of spiral arteries lead to reduced placental perfusion and ischemia.
- Release of antiangiogenic factors like soluble fms-like tyrosine kinase-1 (sFlt-1) interferes with VEGF and contributes to endothelial dysfunction.
- Systemic Endothelial Dysfunction:
- Increased vascular permeability leads to proteinuria and edema.
- Vasoconstriction due to endothelial injury raises blood pressure.
- Coagulopathy from vascular injury can increase risk of thrombosis.
- Inflammation and Oxidative Stress:
- Excessive inflammatory response and oxidative stress exacerbate vascular dysfunction, affecting multiple organs.
Clinical Presentation
- Symptoms:
- Mild Pre-eclampsia: Often asymptomatic or mild edema and headache.
- Severe Pre-eclampsia: Severe headache, blurred vision, right upper quadrant or epigastric pain, nausea, vomiting, and dyspnea (from pulmonary edema).
- Signs of Eclampsia:
- Tonic-clonic seizures following symptoms of severe pre-eclampsia.
- Often preceded by hyperreflexia, visual changes, or altered mental status.
- Differential Diagnosis:
- Consider alternative causes of hypertension and seizures in pregnancy, such as chronic hypertension, epilepsy, or central nervous system pathologies.
Diagnostic Evaluation
- Laboratory Testing:
- Urine Protein: ≥300 mg/24-hour urine or protein-to-creatinine ratio ≥0.3 indicates proteinuria.
- CBC: Thrombocytopenia (platelet count <100,000/mcL) is an indicator of severity.
- Liver Enzymes: Elevated AST/ALT levels suggest hepatic involvement.
- Renal Function: Elevated creatinine (>1.1 mg/dL) or a doubling from baseline suggests renal impairment.
- Uric Acid: May be elevated, especially in severe cases.
- Imaging:
- Obstetric Ultrasound: Assesses fetal growth and amniotic fluid volume.
- Doppler Ultrasound: May show abnormal uterine artery flow, indicating poor placental perfusion.
Management and Treatment
- Blood Pressure Control:
- Target BP: Aim for <160/110 mmHg to prevent complications.
- Medications: Labetalol, nifedipine, or hydralazine are commonly used due to their safety in pregnancy.
- Seizure Prophylaxis and Management:
- Magnesium Sulfate: Given for severe pre-eclampsia as prophylaxis and for eclamptic seizure control.
- Dosage: 4–6 g IV loading dose, followed by 1–2 g/hr infusion.
- Monitoring for toxicity includes deep tendon reflexes, respiratory rate, and serum magnesium levels.
- Fetal Monitoring and Delivery:
- Steroids: Administered if gestational age is between 24–34 weeks to promote fetal lung maturity.
- Delivery: Recommended for all cases of severe pre-eclampsia at 34 weeks or earlier if maternal or fetal status worsens.
Complications
- Maternal:
- Cerebral Complications: Increased risk of stroke, cerebral edema, and seizures (eclampsia).
- HELLP Syndrome: Hemolysis, elevated liver enzymes, and low platelets, with risks of hepatic rupture and renal failure.
- Pulmonary Edema: Due to increased vascular permeability.
- Fetal:
- Growth Restriction: Due to impaired placental blood flow.
- Preterm Birth: Often required due to maternal or fetal indications.
- Stillbirth: Increased risk in severe pre-eclampsia or eclampsia.
Key Points
- Pre-eclampsia involves new-onset hypertension and proteinuria or organ dysfunction after 20 weeks; eclampsia is marked by seizures.
- Severe pre-eclampsia is indicated by symptoms such as severe headache, visual changes, and BP ≥160/110 mmHg.
- Magnesium sulfate is the drug of choice for seizure prevention in severe pre-eclampsia and for treating eclamptic seizures.
- Management focuses on BP control, magnesium sulfate administration, and timely delivery based on maternal and fetal status.
- Key complications include HELLP syndrome, pulmonary edema, and fetal growth restriction.