Persistent fetal circulation (also called persistent pulmonary hypertension of the newborn, PPHN) is a condition caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the “normal” pattern.
Persistent fetal circulation (also called persistent pulmonary hypertension of the newborn, PPHN) is a condition caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the “normal” pattern.
Aetiology
Normal vascular anatomy with functional vasoconstriction:
Good prognosis | Reversible
Hypoxia
Meconium aspiration
Respiratory distress syndrome (RDS)
Decreased diameter of pulmonary vessels with hypertrophy of vessel walls:
Poor prognosis | Fixed abnormality
Post-term pregnancy
Placental insufficiency
NSAID use by the mother
Decreased size of pulmonary vascular bed:
Poor prognosis | Fixed abnormality
Space-occupying lesions:
Pleural effusions
Diaphragmatic hernias
Functional obstruction of pulmonary blood flow:
Good prognosis | Reversible
Polycythemia
Hyperfibrinogenemia
Pathophysiology
Persistent elevation in pulmonary vascular resistance resulting in right-to-left shunt across the foramen ovale and/or ductus
Echocardiographic features of persistent pulmonary hypertension of the newborn (PPHN): high right ventricular pressure results in tricuspid regurgitation (TR) and deviation of the interventricular septum to the left. Assessment of tricuspid regurgitation velocity by continuous wave Doppler is used to calculate systolic pulmonary arterial pressure. The presence of right-to-left shunt at patent foramen ovale (PFO) and patent ductus arteriosus (PDA) is commonly observed in infants with severe PPHN. Impaired right and left ventricular function is associated with poor outcome in PPHN. | Copyright Satyan Lakshminrusimha
Differential diagnosis:
Cyanotic congenital heart disease
Echocardiographic evaluation of neonatal hypoxemia based on ductal (black bar) and atrial (blue bar) shunts. Left-to-right shunt at the ductal and atrial level is considered normal but can also be seen in the presence of parenchymal lung disease, resulting in hypoxemia in the absence of persistent pulmonary hypertension of the newborn (PPHN) (lower left quadrant). The presence of right-to-left shunt at the atrial and ductal levels is associated with PPHN (upper right quadrant). Right-to-left shunt at the ductal level but a left-to-right shunt at the atrial level is associated with left ventricular dysfunction, pulmonary venous hypertension, and ductal-dependent systemic circulation (lower right quadrant) and is a contraindication for inhaled pulmonary vasodilators, such as inhaled nitric oxide. In patients with right-sided obstruction (such as critical pulmonary stenosis [PS]), right atrial blood flows to the left atrium through the PFO. Pulmonary circulation is dependent on a left-to-right shunt at the patent ductus arteriosus (PDA) (upper left quadrant) | Ao=aorta; LA=left atrium; LV=left ventricle; PA=pulmonary artery; PGE1=prostaglandin E1; RA=right atrium; RV=right ventricle; Rx=treatment; TR=tricuspid regurgitation. | Modified from Nair and Lakshminrusimha. Copyright Satyan Lakshminrusimha.
Management
Ventilatory support
Nitric oxide (NO) inhalation
Selective pulmonary vasodilator
Management of acute persistent pulmonary hypertension of the newborn (PPHN): (1)minimal stimulation with the use of eye covers and ear muffs; (2)sedation and analgesia with a narcotic agent and a benzodiazepine (avoid muscle paralysis if possible); (3) maintain preductal oxygen saturation in the low to mid-90s and postductal saturations above 70% as long as metabolic acidosis, lactic acidosis, and/or oliguria are not present; (4)lung recruitment with adequate positive end-expiratory pressure (PEEP) or mean airway pressure and/or surfactant to maintain 8- to 9-rib expansion during inspiration; and (5)maintain adequate blood pressure and avoid supraphysiological systemic pressure. | HFOV=high frequency oscillatory ventilation; MAS=meconium aspiration syndrome; OI=oxygenation index; PIP=peak inspiratory pressure. Modified from Nair and Lakshminrusimha. | Copyright Satyan Lakshminrusimha
