Mechanisms regulating the ductus arteriosus

A patent ductus arteriosus (PDA) results in increased pulmonary blood flow and redistribution of flow to other organs. Several co-morbidities (i.e., necrotizing enterocolitis, intracranial hemorrhage, pulmonary edema/hemorrhage, bronchopulmonary dysplasia, and retinopathy) are associated with the presence of a PDA, but whether or not a PDA is responsible for their development is still unclear. In this review, comparative physiology between the full term and preterm newborn and the barriers preventing the necessary cascade of events leading to permanent constriction of the PDA are reviewed.     

CD1小鼠动脉导管Kca mRNA表达情况研究

目的 研究高电导钙离子激活的钾通道（Kca)mRNA在妊娠晚期胎鼠和新生CD1小鼠动脉导管（DA）上的表达情况。以期阐明Kca在小鼠DA关闭调控方面的作用。方法 采用逆转录聚合酶链反应（RT-PCR）和Southern杂交方法。检测了经剖宫产分娩的妊娠d17,d18和d19CD1胎鼠，以及自然产d1新生小鼠DAKcamRNA的表达情况。结果 KcamRNA表达于胎鼠DA，以d19表达水平最高，但新生小鼠DA无KcamR-NA表达。结论 KcamRNA在胎鼠DA有表达，但出生后无表达，提示在宫内低氧环境中Kca可能是维持DA开放状态的一个重要因素。而生后无表达则可能与DA的关闭有关。     

Surfactant and patent ductus arteriosus

Objective  

To investigate the relationship between surfactant replacement therapy and the development of a haemodynamically significant ductus arteriosus.     

Indomethacin and renal function in premature infants with persistent patent ductus arteriosus.

Renal function during indomethacin treatment was studied in 12 premature infants with patent ductus arteriosus. Decreases in urinary flow rate, GFR, and CH2O by 56, 27, and 66%, respectively, occurred during Indo therapy. Urinary excretion rates of ions were also reduced: Na by 70%, Cl by 79%, K by 40%. These changes were accompanied by slight decreases in plasma sodium concentration and osmolality. Except for GFR and urinary Na and osmolality, all these functions returned to pretreatment values one to two weeks after stopping the drug.     

Diagnosis of patent ductus arteriosus

This review shows that clinical signs cannot be relied on to reveal left-to-right ductal shunting in the preterm. Echocardiography can define many of the haemodynamic features, including occult ventricular dysfunction, and categorize shunts into small, moderate or large, without defining ‘significance’ which is multifactorial. Large shunts have an elevated left atrial:aortic root ratio (>1.3:1 or >1.5:1, depending on fluid and diuretic policy) a ductal diameter >1.4 mm and retrograde diastolic flow in the descending aorta exceeding 30% of the antegrade flow. The neonatal clinician and echocardiographer is reminded to remain wary of occult congenital heart disease, particularly before closing the ductus.