## Pulmonary Hypertension in Down Syndrome Children with Down syndrome have a significantly higher incidence of congenital heart defects, particularly atrioventricular septal defects (AVSD), which frequently lead to pulmonary hypertension if left unrepaired. ### First-Line Agent for Acute PH in Pediatrics **Key Point:** Inhaled nitric oxide (iNO) is the gold standard for acute pulmonary hypertension management in children, particularly in the perioperative setting or acute decompensation. **High-Yield:** iNO works by: - Selective pulmonary vasodilation (does not affect systemic circulation) - Activating guanylate cyclase → ↑ cGMP in vascular smooth muscle - Rapid onset (minutes) and offset (minutes after discontinuation) - Improves ventilation-perfusion matching in acute hypoxia ### Comparative Agents for Chronic PH | Agent | Onset | Route | Use Case | Limitation | |-------|-------|-------|----------|------------| | **Inhaled NO** | Minutes | Inhaled | Acute PH, perioperative | Rebound if abrupt withdrawal | | **Sildenafil** | Hours | Oral/IV | Chronic PH maintenance | Slower onset, not for acute crisis | | **Bosentan** | Days | Oral | Chronic PH (endothelin antagonist) | Hepatotoxicity, teratogenic | | **Milrinone** | Minutes | IV | Inotropic support + vasodilation | Non-selective; ↓ BP systemically | **Clinical Pearl:** In acute right heart failure from PH, iNO is preferred because it selectively reduces pulmonary vascular resistance without systemic hypotension, whereas milrinone causes systemic vasodilation and may worsen perfusion pressure. **Tip:** Remember the sequence: acute crisis → iNO; chronic maintenance → sildenafil or bosentan; inotropic need → milrinone (but not first-line for PH alone). [cite:Nelson Textbook of Pediatrics 21e Ch 434]
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