日本小児循環器学会雑誌 Pediatric Cardiology and Cardiac Surgery

The placental circulation is lost and pulmonary vascular resistance is reduced by the establishment of respiration at birth. Consequently, the afterload decreases in the right ventricle and increases in the left ventricle. Both left and right ventricular output increase after birth and the right to left ventricular output ratio decreases. Most normal full-term infants easily handle this major change from fetal to neonatal circulation. However, premature infants have difficulty adapting to the change in loading conditions due to their immaturity, causing maladaptation (circulatory failure) in some cases. Circulatory failure, combined with blood vessel fragility and immature hemostatic capacity, can cause significant complications that have a major prognostic impact, such as intracranial hemorrhage. Therefore, the prognoses of preterm infants and sick newborns can be improved with accurate identification of the causes of circulatory failure and appropriate intervention. Neonatologists in Japan frequently perform echocardiography for preterm infants during the early postnatal period, and neonatal management is based on the findings from this evaluation. This meticulous circulation management is rare globally and is thought to contribute to the excellent outcomes of neonatal care in Japan. This article reviews the current methods for neonatal circulatory assessment and treatment in Japan and describes the typical pathophysiology of circulatory failure.