Persistent fetal circulation

Persistent fetal circulation 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.

In a fetus, there is high pulmonary vascular resistance and low pulmonary blood flow as the fetus does not use the lungs for oxygen transfer. When the baby is born, the lungs are needed for oxygen transfer and need high blood flow which is encouraged by low pulmonary vascular resistance.

It can be associated with pulmonary hypertension.^[1] Because of this, the condition is also known as "persistent pulmonary hypertension of the newborn".^[2]

Epidemiology

It occurs in 1-2 infants per 1000 live births^[3]

Types

Normal vascular anatomy with functional vasoconstriction

This has a good prognosis, as it is reversible. Causes include hypoxia, meconium aspiration, and respiratory distress syndrome.

Decreased diameter of pulmonary vessels with hypertrophy of vessel walls

This has a poor prognosis, as it is a fixed abnormality. Causes include post-term pregnancy, placental insufficiency, and NSAID use by the mother.

Decreased size of pulmonary vascular bed

This has a poor prognosis, as it is a fixed abnormality. It is caused by space occupying lesions such as pleural effusions and diaphragmatic hernias.

Functional obstruction of pulmonary blood flow

This has a good prognosis if it is reversible. Causes include polycythemia and hyperfibrinogenemia. ^[4]

Treatment

Treatment aims to increase the amount of oxygen in the blood and reverse any causes of hypoxia.

• oxygen therapy
• mechanical ventilation
• NO Inhalation
• Prostaglandins (intravenous)

The therapies available to manage PPHN include the high frequency ventilation, surfactant instillation, inhaled nitric oxide, and extracorporeal membrane oxygenation. These expensive and/or invasive modalities are unavailable in the developing countries where the frequency and mortality of PPHN is likely to be much higher due to higher incidence of asphyxia and sepsis. In developing countries, the medical facilities are usually supplied with outdated equipment that was initially donated. "For people in developing countries, basic medical supplies are luxuries that are simply not available or not affordable. Doctors and nurses must constantly make do - washing and reusing "disposable" gloves and syringes, or substituting inappropriate materials such as fishing line or sewing thread for suture- or patients must go without needed care. In many countries patients must bring their own supplies, even acquire their own medicines, before treatment can be given." The limitations made it necessary to search for cheaper therapies, assuring quick effectiveness and stabilization of the patient going through a very high-risk situation. The treatments are chosen on the basis of low cost, low-tech, wide availability, and safety in the hands of non-professionals. Therefore, oral sildenafil citrate, has been the alternative way of therapy. The cost comparison shows that sildenafil is lower in cost than iNO and more readily available. There is improvement in oxygenation when oral sildenifal is administered according to the studies found in the Official Journal of the American Academy of Pediatric. The positive research results for varies studies indicates that oral sildenifal is a feasible source to improve oxygenation and survival in critical ill infants with PPHN secondary to parenchymal lung disease in centers without access to high-frequency ventilation, iNO, or ECMO.

References

External links

• http://www.kumc.edu/instruction/medicine/pedcard/cardiology/pedcardio/pfcdiagram.gif
• Dunn PM (March 1994). "Professor Charles D Meigs (1792-1869) of Philadelphia and persistent fetal circulation". Archives of Disease in Childhood: Fetal and Neonatal Edition. 70 (2): F155–6. doi:10.1136/fn.70.2.f155. PMC 1061019. PMID 8154909.