Preeclampsia

A pregnant patient's blood pressure reads 148/96 at 34 weeks — but the patient feels fine. The absence of symptoms doesn't mean the absence of danger. Knowing what to look for next could save two lives.

Preeclampsia is a hypertensive disorder diagnosed after 20 weeks' gestation. The diagnostic threshold is a sustained systolic BP ≥140 mmHg or diastolic ≥90 mmHg on two readings at least 4 hours apart, plus proteinuria (≥300 mg in 24-hour urine or protein/creatinine ratio ≥0.3 mg/mg). Preeclampsia can exist without proteinuria if other end-organ damage is present: thrombocytopenia (platelets <100,000), elevated liver enzymes (AST/ALT twice normal), renal insufficiency (creatinine >1.1 mg/dL), pulmonary edema, or new-onset cerebral or visual disturbances. Severe features include BP ≥160/110, persistent headache unresponsive to medication, right upper quadrant or epigastric pain (hepatic capsule stretch), visual changes (scotomata, blurred vision), and thrombocytopenia. HELLP syndrome — Hemolysis, Elevated Liver enzymes, Low Platelets — is a severe variant often missed because BP may not be dramatically elevated. Assess deep tendon reflexes: hyperreflexia (3+ to 4+) and clonus signal CNS irritability and impending seizure (eclampsia). Edema alone is not diagnostic — many healthy pregnancies include edema — but sudden facial or periorbital swelling with rapid weight gain (>2 lb/week) warrants immediate investigation.

Key Distinctions

Don't confuse gestational hypertension (elevated BP without proteinuria or end-organ damage) with preeclampsia — proteinuria or organ involvement is the dividing line. Students often think edema equals preeclampsia; it doesn't. Dependent edema is normal in pregnancy. The red flag is sudden generalized or facial edema plus hypertension. RUQ pain in preeclampsia signals liver involvement (HELLP), not gallbladder disease — context of gestational age and BP matters.

Clinical Pearl

HEAD to toe: Headache, Epigastric pain, Altered vision, DTR hyperreflexia — when a pregnant patient after 20 weeks reports any of these, think preeclampsia with severe features until proven otherwise.

Management & Delivery

Once preeclampsia is identified, the definitive cure is delivery, but management bridges the gap. Magnesium sulfate is the first-line drug for seizure prophylaxis — not to lower blood pressure. The loading dose is typically 4–6 g IV over 15–30 minutes, followed by a maintenance infusion of 1–2 g/hr. Therapeutic serum magnesium is 4–7 mEq/L (approximately 5–9 mg/dL). Toxicity follows a predictable ladder: loss of deep tendon reflexes (DTRs) at 7–10 mEq/L, respiratory depression at 10–13 mEq/L, and cardiac arrest above 15 mEq/L. Before every assessment you check three things: DTRs present, respiratory rate ≥12, and urine output ≥30 mL/hr. If any fails, hold the infusion and notify the provider. Calcium gluconate 1 g IV is the antidote — keep it at the bedside. For blood pressure control, IV labetalol or hydralazine is used when systolic ≥160 or diastolic ≥110 mmHg. The goal is not normotension — it is preventing stroke by reducing severe-range pressures. The environment should be low-stimulation: dim lights, minimal noise, side rails padded, suction at bedside. Seizure precautions remain in place during labor and typically 24–48 hours postpartum, because eclampsia can occur after delivery.

Key Distinctions

Magnesium sulfate prevents seizures; it does not treat hypertension — students commonly confuse these roles. Don't mix up calcium gluconate (magnesium antidote) with calcium chloride (more caustic, not the standard bedside rescue drug for mag toxicity). Loss of DTRs is the earliest toxicity sign and comes before respiratory depression — if reflexes are absent, the mag is already too high.

Clinical Pearl

Patellar reflex gone = magnesium too far gone. Check DTRs before you check anything else — no reflexes means stop the drip and grab the calcium gluconate.