A 28-year-old G2P1 at 34 weeks gestation with chronic hypertension presents with vaginal bleeding and severe right upper quadrant pain. Ultrasound confirms placental abruption with 30% separation and fetal heart rate of 135 bpm. Maternal blood pressure is 160/110 mmHg. Coagulation profile is normal. What is the drug of choice for acute blood pressure control in this setting?

## Acute Hypertension Management in Placental Abruption **Key Point:** IV labetalol is the first-line agent for acute hypertensive emergency in pregnancy, including placental abruption, because it is safe for both mother and fetus with rapid onset and no risk of fetal hypoxia. **High-Yield:** Labetalol combines α- and β-adrenergic blockade, reducing maternal BP without causing reflex tachycardia or fetal compromise. It is preferred over hydralazine and sodium nitroprusside in obstetric emergencies. ### Mechanism & Pharmacology - **α-blockade:** Peripheral vasodilation - **β-blockade:** Reduced cardiac output and heart rate - **Net effect:** Smooth, controlled BP reduction without maternal or fetal tachycardia - **Onset:** 5–10 minutes IV; duration 3–6 hours ### Dosing in Hypertensive Emergency - **IV bolus:** 10–20 mg IV push, repeat every 10 minutes (max 220 mg) - **IV infusion:** 1–2 mg/minute, titrate to effect - **Target:** Reduce MAP by 15–25% in first hour (avoid sudden drops) **Clinical Pearl:** In abruption with severe hypertension, labetalol is preferred because it maintains uteroplacental perfusion while controlling maternal BP, reducing risk of further placental separation. ### Comparison of Antihypertensives in Obstetric Emergency | Agent | Onset | Safety Profile | Fetal Effect | Use in Abruption | |-------|-------|-----------------|--------------|------------------| | **Labetalol IV** | 5–10 min | Excellent | No adverse effect | **First-line** | | Hydralazine IV | 10–20 min | Good | Reflex tachycardia → fetal distress | Second-line | | Sodium nitroprusside | 1–2 min | Caution | Risk of cyanide toxicity (prolonged use) | Avoid (short-term only) | | Nifedipine PO/SL | 15–30 min | Good | Safe but slower onset | Not for acute emergency | **Warning:** Hydralazine causes maternal and fetal tachycardia, which can worsen fetal distress in abruption. Sodium nitroprusside is reserved for refractory cases due to cyanide/thiocyanate toxicity risk with prolonged use. **Mnemonic:** **LAB** = **L**abetalol is **A**lpha + **B**eta blocker — remember it as the obstetric **A**ntihypertensive **B**est choice. [cite:ACOG Committee Opinion on Hypertension in Pregnancy 2013; Obstetric Anaesthetists' Association Guidelines on Severe Hypertension in Pregnancy]