What is the management approach for severe Pregnancy-Induced Hypertension (PIH)?

Management of Severe Pregnancy-Induced Hypertension

For severe PIH (BP ≥160/110 mmHg), immediate antihypertensive treatment is mandatory, with intravenous labetalol as the first-line agent, targeting BP reduction to 140-150/90-100 mmHg within 15-60 minutes. 1

Immediate Blood Pressure Management

Definition and Treatment Threshold

• Severe PIH is defined as BP ≥160/110 mmHg 1, 2
• BP >160/110 mmHg lasting >15 minutes warrants immediate drug treatment 1
• The immediate goal is to decrease mean BP by 15-25%, targeting SBP 140-150 mmHg and DBP 90-100 mmHg 1

First-Line Antihypertensive Agents

Intravenous Labetalol (Preferred):

• Labetalol IV is considered safe and effective for severe pre-eclampsia 1
• Dosing: Start with bolus administration, can be given repeatedly until BP controlled 3
• Oral labetalol: 100 mg twice daily, up to 2400 mg/day for ongoing management 3
• Does not adversely affect fetoplacental circulation 4

Oral Nifedipine (Alternative):

• Immediate-release oral nifedipine is efficacious but carries risk of uncontrolled hypotension, especially when combined with magnesium sulfate 1
• Should be avoided except in low-resource settings when IV access unavailable 1
• If no IV access: 200 mg labetalol orally OR 1.0-1.5 g methyldopa orally as bridge therapy 1

Intravenous Hydralazine (Use with Caution):

• Still widely used in North America but associated with more adverse effects than labetalol 1
• Increased risk of maternal hypotension, cesarean section, placental abruption, maternal oliguria, and fetal tachycardia 1
• Requires close monitoring of maternal BP and fetal wellbeing 1
• FDA-indicated for severe essential hypertension when urgent BP lowering needed 5

Alternative IV Agents:

• IV urapidil or nicardipine can be used 1
• Sodium nitroprusside: drug of last resort only for extreme emergencies due to risk of fetal cyanide poisoning and increased maternal intracranial pressure 1

Seizure Prophylaxis

Magnesium Sulfate Administration:

• Recommended for prevention of eclampsia and treatment of seizures in severe PIH 1, 3
• Should NOT be given concomitantly with calcium channel blockers due to risk of severe hypotension from synergistic effects 1
• Indicated for patients with severe hypertension and neurological signs (irritability, hyperreflexia, clonus) 3

Special Circumstance: Pulmonary Edema

When pre-eclampsia is complicated by pulmonary edema:

• Nitroglycerin (glycerol trinitrate) IV infusion is the drug of choice 1
• Start at 5 mcg/min, increase every 3-5 minutes to maximum 100 mcg/min 1
• Diuretics are inappropriate as plasma volume is already reduced 1

Critical Monitoring Requirements

Maternal Early Warning Criteria requiring immediate action: 1

• SBP <90 or >160 mmHg
• DBP >100 mmHg
• Heart rate <50 or >130 bpm
• Oxygen saturation <95% on room air
• Oliguria (<35 mL/h for ≥2 hours)
• Altered mental status (agitation, confusion, unresponsiveness)
• Non-remitting headache
• Shortness of breath

Before Delivery Monitoring: 3

• BP every 15-30 minutes until controlled
• Laboratory tests immediately: CBC with platelets, liver transaminases, creatinine, uric acid
• Clinical assessment for clonus, visual symptoms, severe headache
• Continuous cardiotocography
• Ultrasound for amniotic fluid volume assessment

Timing of Delivery

Delivery is the definitive treatment for severe PIH: 1, 3

• Induction of labor recommended at 37 weeks gestation for gestational hypertension or mild pre-eclampsia 1, 3
• Immediate delivery indicated for severe heart failure and/or fetal distress 1
• Optimal timing depends on fetal wellbeing, gestational age, and severity of hypertensive disorder 1

Medications to AVOID

Strictly Contraindicated: 1, 3

• ACE inhibitors
• Angiotensin receptor blockers (ARBs)
• Direct renin inhibitors
• These cause severe fetotoxicity, particularly in second and third trimesters

Not for Urgent BP Reduction:

• Methyldopa should NOT be used primarily for urgent BP reduction 1
• Methyldopa is appropriate for chronic management but too slow-acting for hypertensive emergencies

Postpartum Considerations

• Ten percent of maternal deaths from hypertensive disorders occur postpartum 1
• Complications include stroke and eclampsia 1
• Hypertension should resolve within 6-12 weeks postpartum; persistence suggests pre-existing hypertension 1
• Labetalol, nifedipine, enalapril, and metoprolol are safe for breastfeeding 1

Common Pitfalls to Avoid

• Do not delay treatment waiting for "confirmation" - BP ≥160/110 mmHg for >15 minutes is sufficient 1
• Avoid combining nifedipine with magnesium sulfate due to synergistic hypotensive effects 1
• Do not use short-acting oral nifedipine as first-line when IV access available 1
• Do not restrict salt intake - normal diet recommended as salt restriction may induce low intravascular volume 1
• Do not use diuretics for pulmonary edema in pre-eclampsia - plasma volume already reduced 1