A robust and well shielded thermal conductivity device for low temperature measurements.

We present a compact mechanically robust thermal conductivity measurement apparatus for measurements at low temperatures (<1 K) and high magnetic fields on small high-purity single crystal samples. A high-conductivity copper box is used to enclose the sample and all the components. The box provides protection for the thermometers, heater, and most importantly the sample increasing the portability of the mount. In addition to physical protection, the copper box is also effective at shielding radio frequency electromagnetic interference and thermal radiation, which is essential for low temperature measurements. A printed circuit board in conjunction with a braided ribbon cable is used to organize the delicate wiring and provide mechanical robustness.

Thermal conductivity of Ho2Ti2O7 along the [111] direction.

Thermal transport measurements have been made on the spin-ice material Ho(2)Ti(2)O(7) in an applied magnetic field with both the heat current and the field parallel to the [111] direction for temperatures from 50 mK to 1.2 K. A large magnetic field >6 T is applied to suppress the magnetic contribution to the thermal conductivity in order to extract the lattice conductivity. The low field thermal conductivity thus reveals a magnetic field dependent contribution to the conductivity which both transfers heat and scatters phonons. We interpret these magnetic excitations as monopolelike excitations and describe their behavior via existing Debye-Hückel theory.

Thoracoscopic closure of patent ductus arteriosus: a less traumatic and more cost-effective technique.

The authors have developed a technique of thoracoscopic closure of patent ductus arteriosus (PDA) that significantly reduces the surgical morbidity, recovery time, and hospital costs traditionally associated with the standard open procedure. Ten patients have undergone the procedure, with nine completed successfully. One patient required conversion to an open thoracotomy. There were no operative complications, and closure of the ductus was confirmed in all cases with a postoperative echocardiogram. Eight of ten patients were discharged in under 24 hours, and hospital charges were on the average 30% to 40% less.

Selective and sustained pulmonary vasodilation with inhalational nitric oxide therapy in a child with idiopathic pulmonary hypertension.

Low doses of inhaled nitric oxide caused selective and sustained pulmonary vasodilation in an infant with pulmonary hypertension without causing systemic hypotension, despite the failure of treatment with other vasodilators.

Bezold-Jarisch reflex in postoperative pediatric cardiac surgical patients.

The Bezold-Jarisch reflex is an inhibitory reflex that originates from the heart, is mediated by the vagus nerve, and is manifested by hypotension and bradycardia. We present 4 pediatric cardiac surgical patients, aged 1 day to 9 months, who exhibited cardiovascular collapse in their early postoperative course. In each patient, cardiovascular deterioration was marked by an insidious decrease in arterial blood pressure without an associated change in heart rate, central venous pressure, or airway pressure. Bradycardia followed the decrease in blood pressure. The Bezold-Jarisch reflex was suspected and atropine was administered, first as a bolus injection at 0.01 mg/kg, and later, as a continuous infusion at 0.01 mg.kg-1.h-1. Atropine prevented recurrent episodes of hypotension and bradycardia. We believe the Bezold-Jarisch reflex is more prevalent than previously suspected in postoperative pediatric cardiac surgical patients.

Clinical spectrum of Kawasaki disease in infants younger than 6 months of age.

We report an unselected series of eight patients younger than 6 months of age with Kawasaki disease evaluated between January 1982 and May 1984. The incidence of coronary artery aneurysms (six patients) and the mortality (two patients) were unusually high in this small series. Because of the confusing clinical presentation in three patients, diagnosis was delayed until pathologic or echocardiographic evidence of coronary vasculitis or aneurysm was discovered. The currently accepted clinical criteria for Kawasaki disease may not always identify patients with the pathologic findings of the syndrome who are younger than 6 months of age. The diagnosis of Kawasaki disease and echocardiographic evaluation of the coronary arteries should be considered in young infants with prolonged fever of unknown origin.

Association of low systolic and diastolic blood pressure with significant patent ductus arteriosus in the very low birth weight infant.

The systolic, diastolic, and pulse pressures of 34 infants weighing less than 1200 g, who required mechanical ventilation for hyaline membrane disease, were prospectively evaluated in the first week of life and related to the magnitude of ductal shunting. Seventeen infants developed a large patent ductus arteriosus (PDA) corresponding to significant left-to-right ductal shunting and requiring surgical ligation. By the second day of life these patients with large PDAs had significantly lower mean systolic and diastolic BPs than the non-PDA infants. There were no significant differences in pulse pressures between groups. Both systolic and diastolic BPs promptly returned to control values after ligation. A mean diastolic BP less than 28 mm Hg on the third day of life was significantly associated with a PDA in 93% of patients.

Surgical management of absent right pulmonary artery with associated pulmonary hypertension.

A critically ill 21-month-old girl with congenital absence of the right pulmonary artery and severe pulmonary hypertension and congestive heart failure underwent conduit restoration of flow to the right lung. This patient had marked clinical improvement and reduction in pulmonary hypertension and represents the second reported surgically-treated case for absent right pulmonary artery. Reestablishment of pulmonary artery continuity is therefore recommended when cardiac failure and pulmonary hypertension occurs.

Leukotriene C4 and D4 in neonates with hypoxemia and pulmonary hypertension.

Persistent pulmonary hypertension of the newborn is a syndrome consisting of severe hypoxemia and pulmonary hypertension that appears within hours of birth. Since certain leukotrienes (C4, D4, and E4) are known to produce some of the features of persistent pulmonary hypertension of the newborn, including pulmonary vasoconstriction, bronchoconstriction, decreased lung compliance, and pulmonary edema, we studied five newborns with the syndrome to determine whether these leukotrienes were present in their airways. We found leukotriene C4 and leukotriene D4 in the lung lavage fluids of all five newborns who had the clinical diagnosis of persistent pulmonary hypertension and who required ventilatory assistance. In contrast, leukotrienes were not demonstrated in a control group of 14 infants requiring ventilatory assistance who did not have the clinical diagnosis of persistent pulmonary hypertension. We conclude that leukotrienes may have a role in persistent pulmonary hypertension of the newborn.

Surgical and medical experience with 734 premature infants with patient ductus arteriosus.

During the past 5 years, patent ductus arteriosus (PDA) presented in 734 preterm infants (less than 2.5 kg and 37 weeks gestation) of 2,532 admissions (29%). The ductus presented with murmur, bounding pulses, and often congestive heart failure. Medical treatment consisted of the following: fluid restriction, furosemide, respiratory support, and rarely digoxin. The patients who were unresponsive to medical treatment had surgical ligation (306 of 734 or 42%). The patients who had ductal ligation were smaller, i .e., 82% of the surgical patients weighed less than 1.5 kg as compared to 38% of the medical patients. Of those patients weighing less than 1.5 kg, the surgical and medical groups were compared and the following observations made: The incidence of respiratory distress syndrome was greater in the surgical group (86% or 216 of 252 patients versus 69% or 111 of 161 medical patients, p less than 0.001) and the long-term survival was better (89% or 224 of 252 surgical patients versus 77% or 124 of 161 medical patients, p less than 0.005). In addition, the average duration of intubation was shorter in this surgical subgroup (8.9 versus 13.6 days). Significant left atrial enlargement and echocardiographic left atrial/aortic (LA/Ao) ratios of greater than 1.5:1 occurred in 58% or 171 of 290 surgical patients versus 32% or 59 of 190 medical patients (p less than 0.001). During the first 3 years of this study (medical treatment averaged 5 days), the duration of intubation in the surgical patients averaged 15.2 days; by comparison, in the last 2 years of this study (medical treatment averaged 1 to 2 days), the duration of intubation was 6.5 days (p less than 0.001). Necrotizing enterocolitis (NEC) occurred in 11% or 46 of 428 medical patients versus 0.3% (one of 305 patients) in the ligated group postoperatively (p less than 0.001). Late deaths were related to lung disease, central nervous system problems, NEC, and so on. From this study, it was determined that ligation of a significant PDA is associated with (1) zero surgical risk, (2) a reduced incidence of NEC, (3) reduced duration of intubation, especially with early ligation, and (4) improvement in late survival. Thus the surgical approach is our treatment of choice for a refractory PDA.

Surgical repair of coarctation of the aorta in infants less than six months of age: including the question of pulmonary artery banding.

High mortality rates (20% to 60%) have been reported in the repair of coarctation of the aorta in infancy. During a 4 year period, 34 infants less than 6 months of age had coarctation repair (two prior to 1976). Eleven were less than 2 weeks of age, nine were 2 weeks to 1 month, eight were 1 to 2 months, and six were 2 to 6 months. Associated lesions were patent ductus arteriosus (PDA) (82%), ventricular septal defect (VSD) (53%), and other intracardiac lesions (35%). Twenty-three patients (67%) had emergency operations; the other procedures were semielective. The indications for operation included congestive cardiac failure (91%), acidosis (32%), hypertension (29%), cardiogenic shock (26%), and cardiac arrest (18%). There was one operative death (2.9%) in a patient with severe pulmonary valve insufficiency and multiple VSDs. There was one late death a 4 months (Taussig-Bing complex). Primary repair was used in 15, patch-graft angioplasty in 19 (left subclavian artery in nine, left common carotid in one, and Dacron or pericardial patch in nine). Two (6%) required reoperation for recurrent coarctation (follow-up 3 to 36 months with a mean of 25.8). Of 15 patients with a large VSD, six had pulmonary artery banding with two deaths (one operative and one late), two had debanding plus VSD repair, and two are awaiting operation. The remaining nine patients did not have banding (no operative or late deaths), four patients required late VSD closure, two VSDs closed spontaneously, two VSDs became smaller, and one patient is awaiting VSD closure. The infrequent need for pulmonary artery banding may be partly due to "physiological banding" seen at Denver's high altitude. The VSD spontaneously closed or became smaller in 44% of nonbanded patients. The low operative mortality can be ascribed to (1) aggressive medical therapy, (2) emergency catheterization and repair, (3) avoidance of hypothermia, and (4) adequate relief of the coarctation.

Presentation of atrial septal defect in infancy.

Four patients with atrial septal defects and congestive heart failure in the first year of life had none of the classic auscultatory findings of atrial septal defect. Three of four had murmurs suggestive of innocent pulmonary-artery branch stenosis.

Double outlet right ventricle with absent aortic valve.

A case of double outlet right ventricle with multiple associated cardiovascular anomalies, including total absence of the aortic valve, is reported.