Good Morning and Welcome Applicants! January 27, 2011

Pulmonary HTN Pulmonary Artery Pressure = L atrial pressure + (pulm flow x pulm vascular resis) Any increase can lead to pulm HTN

Pulmonary HTN Progressive Pulmonary artery pressure Untreated >25 mm Hg Untreated RV unable to support circulation Prognosis determined by reversibility of underlying process

PPHN Most common cause of PHTN in the newborn 0.2% of newborns Usually associated with respiratory conditions Elevated pulm vasc resistance Right to left shunting Foramen ovale Ductus arteriosis Significant hypoxemia Idiopathic

Highly vascular placenta serves as the organ for gas exchange and contributes to a lowered fetal systemic arterial pressure Therefore, since the lungs are not needed for gas exchange, the pulmonary vessels are constricted, making pulmonary and systemic pressures nearly equal. 90-95% of the cardiac output is going to bypass the lungs At birth, the PAP decreases to 50% of systemic artery pressure and pulmonary blood flow increases almost tenfold. Changes in pressure are due to increased arterial pH, oxygen tension, the physical pulling open on capillaries accompanied by lung inflation, local endogenous vasoregulatory mediators including NO, and removal of the low-resistance placenta. Should have the greatest decline over the first 24 hours and falls over first 2 postnatal weeks.

Many processes interrupt the normal transition and result in PPHN Maladaption – normal pulmonary arterial number and muscularization but have a disruption in the decrease in the PVR normally seen -perinatal asphyxia, sepsis, PNA, MAS, acidosis - imbalance of local vasodilatory and vasoconstrictor metabolites Other – chronic in utero hypoxia – increase and extension of medial muscle thickness, obstruction accompanying polycythemia or TAPVR decrease in the number of pulmonary arteries (pulmonary hypoplasia, CDH, oligohydramnios)

PPHN Presentation Profound and labile hypoxemia Out of proportion to parenchymal disease Birth or gradual changes Cyanosis Grunting Flaring Retractions Tachypnea Tachycardia Shock

PPHN Wide variety of severity Hypoxemia and acidosis Normal perfusion to shock Hypoxemia and acidosis Further constricts the pulmonary vessels increasing the PH and creating a cycle

PPHN Shunting PDA Pre and post ductal PaO2 gradient of >20 mmHg O2 saturation gradient of >5%

PPHN X-rays Underlying illness Clear Diminished vascular markings Slightly dilated heart Idiopathic

PPHN Echo Must exclude cyanotic heart disease R to L shunting across foramen ovale or ductus arteriosis Deviation of the atrial septum Ventricular septum Right atrial enlargement Tricuspid regurgitation

PPHN Treatment Underlying disturbances Minimal Stimulation Hypoglycemia Hypocalcemia Polycythemia Hypothermia Minimal Stimulation Calcium

PPHN Treatment Increase systemic resistance Volume Inotropic Decrease R to L shunt Decrease pulmonary vascular resistance Oxygen iNO iNO is reduced by hemoglobin so there is almost no systemic vasodilatory effects

PPHN Treatment Mechanical ventilation High-frequency ventilation Sedation Surfactant ECMO Adequate oxygenation using the lowest possible mean airway pressures and PEEPs, 100% O2 with slow wean

PPHN Outcomes 95% Meconium aspiration 50% Congenital diaphragmatic hernia Neurodevelopmental impairment Neurosensory hearing loss Behavioral problems Respiratory difficulties Most likely due to the underlying condition and severity Parenchymal disease has the best prognosis, maldevelopment has the worst, overall 70-75% 80% of infants will be normal