Clinical meaning
Persistent Pulmonary Hypertension of the Newborn occurs when pulmonary vascular resistance (PVR) fails to decrease after birth, maintaining fetal circulation pattern with right-to-left shunting through PDA and foramen ovale. Normally, increased PaO2 and decreased PaCO2 stimulate endothelial nitric oxide synthase (eNOS) to produce NO, which activates guanylate cyclase to produce cGMP, causing smooth muscle relaxation. In PPHN, this pathway is impaired. Phosphodiesterase-5 (PDE5) degrades cGMP.
Diagnosis & workup
Diagnostics & workup: - Order pre-ductal and post-ductal SpO2 simultaneously (>10% difference confirms R-to-L shunt) - Order echocardiogram to confirm elevated PVR and rule out structural heart disease - Order ABG from pre-ductal site for oxygenation assessment - Order CXR (may show clear lungs with severe hypoxemia: hallmark of PPHN) - Order CBC, blood culture to rule out sepsis as underlying cause - Order BNP level (elevated in pulmonary hypertension) - Calculate Oxygenation Index (OI) to guide therapy escalation - Order cranial ultrasound to screen for IVH if asphyxia-related