Pregnancy Induced Hypertension

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"pregnancy induced hypertension" OR "preeclampsia" management

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Pregnancy-Induced Hypertension (PIH)

Definition & Classification

Hypertension complicates up to 8-10% of pregnancies and is divided into distinct categories:

Category	Definition
Gestational Hypertension	New BP ≥140/90 mm Hg after 20 weeks, resolves postpartum, no proteinuria or end-organ damage
Preeclampsia	Gestational hypertension + proteinuria (>300 mg/24 h) OR end-organ damage (after 20 weeks)
Eclampsia	Onset of seizures in a preeclamptic patient
Superimposed Preeclampsia	Chronic hypertension with new-onset proteinuria or sudden worsening
Chronic/Coincidental Hypertension	Present before pregnancy or persists >6 weeks postpartum

Rosen's Emergency Medicine, p. 3356; Brenner and Rector's The Kidney, p. 2145

ACOG 2013 Diagnostic Criteria for Preeclampsia

Hypertension: SBP ≥140 mm Hg OR DBP ≥90 mm Hg on two occasions at least 4 hours apart in a previously normotensive woman (after 20 weeks). If BP ≥160/105, hypertension may be confirmed within minutes to facilitate urgent treatment.

PLUS one of the following:

Feature	Threshold
Proteinuria	≥300 mg/24 h, OR protein:creatinine ratio ≥0.3, OR dipstick 2+
Thrombocytopenia	Platelets ≤100,000/mL
Renal insufficiency	Creatinine >1.1 mg/dL or doubling without other renal disease
Impaired liver function	Transaminases >2x normal
Pulmonary edema	New onset
Cerebral/visual symptoms	Headache, visual disturbances

Key update from 2013: Proteinuria is no longer required if severe features are present.

Brenner and Rector's The Kidney, p. 2145 (Table 48.3)

Epidemiology & Risk Factors

Approximately 2-7% of pregnancies are complicated by PIH. Risk is highest in:

Women <20 years old
Primigravidas
Twin or molar pregnancies
Hypercholesterolemia, pregestational diabetes, obesity
Family history of PIH
Chronic hypertension (established risk factor for preeclampsia)
Rosen's Emergency Medicine, p. 3356

Pathophysiology

The exact cause remains unknown. The current model centers on a two-stage hypothesis:

Stage 1 - Abnormal placentation: Inadequate trophoblast invasion of spiral arteries. Normally, these become low-resistance, high-capacitance vessels. In preeclampsia, they remain high-resistance, leading to placental ischemia.

Stage 2 - Maternal syndrome: Placental ischemia triggers release of factors that cause widespread maternal endothelial dysfunction via:

Imbalance between proangiogenic factors (VEGF, PlGF) and antiangiogenic factors (sFlt-1, soluble endoglin)
Excess sFlt-1 acts as a VEGF decoy receptor - in the kidney, this causes endotheliosis and proteinuria
Intravascular inflammation, oxidative stress, syncytiotrophoblast stress

Hemodynamic changes: Normal pregnancy is a high-output, low-resistance state. Preeclampsia is characterized by initially elevated cardiac output, followed by a rise in peripheral vascular resistance as disease develops, ultimately causing reduced cardiac output.

Barash Clinical Anesthesia, p. 3509; Brenner and Rector's The Kidney, p. 2086-2094; NKF Primer, p. 2856

Systemic End-Organ Effects

System	Manifestation
Neurologic	Headache, cortical blindness, hyperreflexia, seizures; cerebral hemorrhage is a leading cause of death
Renal	Proteinuria, oliguria, creatinine rise ("glomerular endotheliosis")
Hepatic	Transaminitis, RUQ/epigastric pain, subcapsular hematoma
Hematologic	Thrombocytopenia, microangiopathic hemolytic anemia
Placental	Infarction, abruption, fetal growth restriction, hypoxia

HELLP Syndrome

A particularly severe variant seen in up to 12% of severe preeclampsia (0.2-0.8% of all pregnancies):

H - Hemolysis
EL - Elevated Liver enzymes (ALT/AST >70 U/L)
LP - Low Platelets (<100,000/mL)
Rosen's Emergency Medicine, p. 3357; Sleisenger & Fordtran's GI and Liver Disease

Management

Antihypertensive Therapy

When to start: BP >160 mm Hg systolic OR >105 mm Hg diastolic (threshold for acute treatment; chronic treatment threshold is DBP >105 or SBP >160 per consensus panels).

Goal of BP lowering: Reduce by 15-20%, targeting systolic 140-150 mm Hg. Avoid rapid lowering (risk of uterine hypoperfusion).

Drugs contraindicated in pregnancy: ACE inhibitors, ARBs - unequivocal evidence of fetal harm.

Setting	Drug	Dose
Outpatient/chronic	α-methyldopa	250 mg twice daily (former FDA category B)
Outpatient/chronic	Labetalol	100 mg twice daily
Outpatient/chronic	Nifedipine	30 mg once daily (extended-release)
Acute/inpatient	Hydralazine	5-10 mg IV/IM, repeat q20 min
Acute/inpatient	Labetalol	20 mg IV, escalate to 40 mg at 10 min

Goodman & Gilman's Pharmacological Basis of Therapeutics; Rosen's Emergency Medicine, p. 3358

Seizure Prophylaxis and Treatment: Magnesium Sulfate

Magnesium sulfate is first-line for both seizure prevention and treatment. It has little antihypertensive effect but is the most effective anticonvulsant, maintaining uterine and fetal blood flow.

Indications: Severe preeclampsia, CNS manifestations (headache, visual disturbance, altered mental status), active eclampsia. Also consider postpartum - ~20% of eclampsia occurs >48 hours after delivery.

Dosing:

Loading dose: 4-6 g IV over 15-20 minutes
Maintenance: 2 g/hr IV infusion

Toxicity monitoring:

Magnesium Level	Effect
~10 mg/dL	Loss of deep tendon reflexes
~12 mg/dL	Respiratory depression
>15 mg/dL	Cardiac arrest

Antidote: Calcium gluconate 1 g IV (slow push) reverses hypermagnesemia.

If seizures persist despite MgSO4:

Lorazepam 2-4 mg IV (may repeat x1 after 10-15 min)
Phenytoin/Fosphenytoin 15-20 mg/kg IV
Levetiracetam 20-60 mg/kg IV
Rosen's Emergency Medicine, p. 3358; Goodman & Gilman's

Definitive Treatment

Delivery is the only cure. In severe preeclampsia with end-organ damage, delivery is the treatment of choice when the fetus is sufficiently mature. If very preterm, hospitalization + pharmacotherapy may allow further fetal maturation. Baseline labs (CBC, LFTs, creatinine, uric acid) are essential for monitoring end-organ status.

Postpartum Considerations

PIH and eclampsia can present or worsen up to 48+ hours postpartum
Women should remain on magnesium postpartum if they had CNS manifestations
Chronic hypertension is a major risk factor for recurrence in subsequent pregnancies (recurrence rate ~70% in women with hypertension in a prior pregnancy)
Goodman & Gilman's; Creasy & Resnik's Maternal-Fetal Medicine

Summary Diagram

Normal Pregnancy:          PIH Pathway:
Low-resistance spiral   →  Inadequate trophoblast invasion
arteries (remodeled)       ↓
                           Placental ischemia
                           ↓
                           sFlt-1 ↑, VEGF/PlGF ↓
                           ↓
                           Endothelial dysfunction (systemic)
                           ↓
            ┌──────────────┼────────────────┐
            ↓              ↓                ↓
         Kidney          Brain           Liver
      (proteinuria,   (seizures,       (transaminitis,
       oliguria)       headache)        HELLP)

Sources: Goodman & Gilman's Pharmacological Basis of Therapeutics | Rosen's Emergency Medicine | Brenner & Rector's The Kidney (ACOG 2013 criteria, Table 48.3) | Barash Clinical Anesthesia | NKF Primer on Kidney Diseases | Creasy & Resnik's Maternal-Fetal Medicine | Sleisenger & Fordtran's GI and Liver Disease

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Pregnancy Induced Hypertension

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The PDF includes all sections from the previous response, neatly formatted with:

9 sections with color-coded headers
All diagnostic tables (ACOG 2013 criteria, HELLP, antihypertensive drugs, MgSO₄ dosing, toxicity levels)
Quick Reference Summary table at the end
Full source citations (Goodman & Gilman's, Rosen's, Brenner & Rector's, Creasy & Resnik's, and others)

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