Andersons pediatric cardiology 1090

detect Often the clinical findings are quite labile If the shunt increases, the murmur becomes more obvious Like the first group, it may eventually spill into diastole Other signs of a large shunt may be present, including bounding pulses, a hyperdynamic precordium, and tachycardia This group of patients tends to be more immature and to develop left ventricular failure with relatively smaller shunts Ventilatory status may deteriorate so that higher concentrations of oxygen and increased pressure or rate settings are required to counter a deteriorating status of the blood gases Apneic episodes and bradycardia are common Infants With Lung Disease This group tends to include the most immature infants with birth weights less than 1000 g Usually ventilator dependent, the development of a left-to-right ductal shunt in these patients is associated with increasing requirement for ventilator support and deterioration of the status of the blood gases Murmurs may be difficult to hear, and occasionally a very large duct may be silent Signs of a large left-to-right shunt may occur, but left ventricular failure is often difficult to differentiate from signs due to pulmonary disease or sepsis Investigations Neither the electrocardiogram nor the chest radiograph is particularly helpful in making the diagnosis of a significant duct in premature infants The electrocardiogram may show left ventricular hypertrophy in the group without lung disease, especially if the shunt is substantial and has been present for some time In the other two groups, right ventricular predominance is more usual As mentioned, ischemic changes may also be present The chest radiograph may show cardiomegaly with increased pulmonary blood flow Often the heart is not obviously enlarged, and pulmonary changes due to flow or failure are difficult to differentiate from those due to primary pulmonary problems Echocardiography Persistent patency of the duct after the neonatal period is readily diagnosed by its characteristic clinical features However, in premature infants, especially those with respiratory distress syndrome, the recognition of significant shunting across a patent duct can be difficult Cross-sectional echocardiography and Doppler flow studies are invaluable in determining the presence of a duct, its shunting pattern, size, and response to therapy In addition, it is essential in ruling out other structural malformations prior to intervention Indeed, patients with severe ventilator-dependent respiratory distress syndrome may have a large ductal shunt, which may be entirely silent due to lack of turbulent flow within the vessel Cardiomegaly may also be absent, especially in infants who are fluid restricted Management Because many ducts will eventually close in premature infants, there has been an understandable reluctance to advise aggressive intervention as soon as a significant left-to-right shunt is recognized However, the presence of a ductal shunt has been implicated in the pathogenesis of bronchopulmonary dysplasia and as a factor in the duration of ventilator support This increased risk of chronic lung disease has led many to advocate early and effective treatment Early experience with surgical ligation demonstrated that congestive heart failure could quickly be controlled, although mortality and morbidity from the respiratory distress syndrome remained high With further surgical experience, mortality directly due to the operation has been reduced to less than 1% Some centers have advocated, and successfully performed, surgery in the nursery, thereby avoiding the hazards of transport to and from the operating room After the role of E-type prostaglandins in maintaining ductal patency during fetal life was established, pharmacologically induced closure using indomethacin was soon reported in the premature infant.169,170 Transient renal insufficiency and mild gastrointestinal bleeding were the main side effects Despite its widespread usage, questions remain concerning proper dosage, duration of treatment, and optimal timing of administration The major determinants of success are gestational and postnatal age In general, initial management includes maintenance of an appropriate level of hemoglobin, ventilatory support, diuretic therapy, and restriction of fluids At the time of the last edition of this textbook, the trend was to earlier closure, either by medical or surgical means In ventilated infants weighing less than 1000 g, administration of indomethacin had been associated with improved outcomes,171–173 even in the absence of large left-to-right shunts In contrast, in infants weighing more than 1000 g, outcomes are unaltered, and treatment with indomethacin should be restricted to those with signs of a significant shunt.149 Once the problem is recognized, intake of fluid should be restricted and furosemide given in a dose of 1 mg/kg Digoxin is of dubious benefit in this situation If the shunt remains large after 24 hours, indomethacin should be given, preferably intravenously, although nasogastric administration can be successful Extreme prematurity, very low birth weight, and advanced conceptional or postnatal age are all factors that reduce the chances of successful closure using indomethacin Renal and/or hepatic insufficiency, serious hyperbilirubinemia, or problems with coagulation are contraindications to its use If the duct persists or recurs, a second course of indomethacin should be administered Dosages are largely selected on an empiric basis The initial dose is 0.2 mg/kg, and subsequent dosages depend on age at time of initial treatment If less than 48 hours of age, the subsequent two doses are 0.1 mg/kg, if aged from 2 to 7 days of age, 0.2 mg/kg, and if greater than 7 days, 0.25 mg/kg The rate of reopening is highest in the very premature, occurring in one-third of those weighing less than 1000 g and in less than 10% of those weighing 1500 g If there is no response to indomethacin, surgical ligation or catheter-based device closure should be undertaken.174,175 Indomethacin-induced closure of the duct is followed by immediate and progressive clinical improvement, with a decrease in requirements for oxygen and in mean airway inflation pressure during mechanical ventilation Lung compliance has been shown to improve after both surgical ligation and medical closure with duration of ventilation, length of hospitalization, and the costs of medical care, reduced by early treatment.176–178 The use of prophylactic indomethacin in infants with a duct is controversial.179,180 It is unsettled if such therapy reduces length of stay, oxygen need, or mechanical ventilatory duration or if the incidence of bronchopulmonary dysplasia may be decreased.172,180–183 Reversal of indomethacin-induced ductal closure by administration of prostaglandin, in the presence of ductal-dependent cardiac malformations, has been possible.184 Surgical ligation of the persistent duct in premature infants was first reported in 1963.185 As with indomethacin, surgery has been associated with a decreased need for ventilatory support and reduced hospital stay,186–189 particularly in infants weighing less than 1500 g.187,190 Surgery can be safely carried out in the neonatal intensive care unit to avoid the stress of transportation to the operating theater Although ligation has been the traditional approach, recently videoassisted thorascopic techniques have been proven successful.191,192