The technique of modified ultrafiltration is a more efficient application of the concept of ultrafiltration during cardiopulmonary bypass. It has been shown to be superior to the conventional method of ultrafiltration.

The method can save considerable quantities of donor blood by returning not only the red cells, but also the white cells, platelets, and clotting factors back to the patient, components which otherwise would be discarded. The elevation of the hematocrit made possible by this method after bypass will permit an “acceptable” hematocrit to be achieved when temperatures become normal after ultrafiltration. The return of platelets and clotting factors along with a high hematocrit will contribute towards significantly minimizing the postoperative loss of blood, and, consequently, the amount of blood requiring to be transfused. The possibility of elevation of the hematocrit allows for a lower hematocrit during bypass. This can achieve a considerable saving of donor blood, particularly in small children who invariably need blood added to the prime, making bloodless pediatric surgery a real possibility. The technique also minimizes the rise in total water in the body after cardiopulmonary bypass in children and promises favorably to alter the course of leaking capillaries as seen frequently in neonates and infants. It has been shown to improve hemodynamics at a crucial time when the patient has been weaned from cardiopulmonary bypass and needs optimum conditions for recovery. From the point of view of research, ultrafiltration offers a window to look at the inflammatory process induced by cardiopulmonary bypass.

It promises to be a valuable technique to investigate the elimination and possibly quantification of toxic metabolites produced during bypass. It also allows evaluation and assessment of different protocols for bypass, involving varying rates of flow and temperature, for their response to the production of these toxic metabolites, thus offering the potential to achieve a model of cardiopulmonary bypass which is as physiological as possible. With advances in the systems of perfusion, aided by computers, it should be possible to control the rate of ultrafiltration and precisely regulate the transfusion of the venous reservoir fluid with the aid of feedback loops from the venous and arterial pressures in the heart. This could make ultrafiltration an integral part of routine cardiopulmonary bypass.

Cardiopulmonary bypass in neonates is markedly different from the procedure used in children above 10 kg and in adults. There are two major reasons for this—first, the mismatch between the volume of the heart-lung machine circuit and that of the blood in the patient and second, the immaturity of tissues in the first three months of life.

The advent of cardiopulmonary bypass in 1953, and its subsequent continuous refinements, have securely established the specialty of cardiovascular surgery. In conjunction with the improved methods of myocardial preservation, this has allowed the safe repair of acquired and complex congenital cardiac defects. During the years, the many variables of the systems used for cardiopulmonary bypass have been altered to the point that most operations are now reproducible with, relatively, low morbidity and mortality. Although in its present form the system is quite reasonable for most routine surgery, it is far from perfect. There remains, therefore, a quest for alterations to improve the system as an ongoing process. Certain complications of open-heart surgery persist and many new and unique approaches to the concept of organ protection and the treatment of these complications must be developed and refined.

One of the most challenging applications of cardiopulmonary bypass is corrective cardiac surgery in the neonate. The small size and high metabolic demand of these patients require miniaturized but efficient equipment. Even with the most advanced components, the volume required to prime the perfusion circuit is typically more than twice the blood volume of a neonate. Neonates have limited cardiac and pulmonary reserves and, therefore, great care is required to preserve those organs that have often already been subjected to hypoxemia, congestive heart failure, or low cardiac output prior to surgery. There is a tendency toward extravascular movement of fluids in newborns subjected to bypass that can adversely affect outcome. Careful monitoring and precise management of perfusion are essential to a successful procedure and optimal recovery of these patients.

For forty years, heparin has been used to temporarily inhibit normal coagulation so as to permit the use of extracorporeal circulation. It has proved effective in preventing gross thrombosis and has not been compromised by changes in adjunctive practices (such as profound hypothermia; circulatory arrest), new pharmacological therapies (such as anesthetics or antibiotics), devices (such as membrane oxygenators), or during use in patients at the extremes of age. Unfortunately, heparin has been and continues to be inefficient in preserving hemostatic function during cardiopulmonary bypass resulting in undesirable bleeding after surgery.

The debate concerning no flow versus low flow continues. Thus, it has not yet been possible to conclude whether limited period of total circulatory arrest, as opposed to maintained but reduced systemic flow, offers superior protection of the brain during cardiac surgery in children. While most previous work has focused on the hypothermic period of no versus low flow, less is known about the conditions during and after rewarming with full systemic flow. Some previous data, which related the ischemic marker creatine kinase BB during profound hypothermic procedures, suggested that neural dysfunction was aggravated by posthypothermic factors such as hyperglycemia, acidosis and anemia.

In our first two experiments, we examined brain tissue pH and tensions of oxygen and carbon dioxide in dogs core cooled to 20°C. So as to evaluate the effects of 60 minutes of circulatory arrest, 120 minutes of low-flow perfusion (25 mI/kg/mm), and 120 minutes of moderate-flow perfusion (50 mi/kg/mm), all conducted with and without pulsatile assistance. We further determined the effects of blood gas strategy on the same variables with 60 minutes of circulatory arrest. In a third experiment, we directly observed microcirculation at the surface of the brain during profoundly hypothermic perfusion. In the fourth experiment, we measured cerebral blood flow, oxygen consumption, and excessive production of lactate. Profound anoxia occurred within 20 minutes of circulatory arrest, causing severe and progressive acidosis in the brain tissues along with hypercapnia. The inhalation of 5% or 7% carbon dioxide during core cooling made the brain unacceptably acidotic. The brain acidosis was mild with low flow perfusion, and slight with moderate-flow perfusion. Pulsatile assistance improved acidosis in the brain tissues at all rates of flow. It also improved the microcirculation, the patent number of arterioles and stabilized flow in bridging veins. Cerebral metabolism became aerobic without alterations in cerebral consumption of oxygen during low-flow perfusion. We recommend flow rates above 25% of normal, alpha-stat strategy, and pulsatile assistance for better protection of the brain during profound hypothermia.

Cardiopulmonary bypass has been extended to the very young patient undergoing operative correction of congenital heart defects. Growth and development of the central nervous, cardiovascular, pulmonary, and renal systems place significant metabolic and nutritional demands on cellular growth and repair. Immature homeostatic regulation and cellular function require modification of the approaches to preservation of organs and cardiovascular support used in older children and adults undergoing open-heart surgery. Aspects of newborn and infant physiology relevant to cardiopulmonary bypass and postoperative care are reviewed. Current approaches and future strategies designed to address the needs of the developing patient who requires cardiopulmonary bypass are discussed.

We examined the number of elastic lamellae in the wall of the proximal aortic arch, aortic isthmus and descending aorta in patients with coarctation of the aorta. In the proximal aortic arch, the number of elastic lamellae was significantly lower in patients with coarctation compared to those with normal hearts without aortic anomalies and those with intracardiac defects but without aortic anomalies. The isthmus also showed a significantly lower number of elastic lamellae in the presence of preductal coarctation. In the descending aorta, the number of elastic lamellae was not significantly different between the different groups. There is doubt about the etiology of coarctation. Recent investigations showed that cells from the cardiac neural crest contribute to the formation of the arch arteries and the media of the arch. A developmental error of the neural crest might be responsible for the abnormal mural structures found in patients with aortic coarctation.

We reviewed the echocardiographic features of 16 children with prominent Eustachian valves, six of whom had associated pathology of the right heart, while eight had other anomalies, primarily atrial and ventricular septal defects. The hearts of two patients were structurally normal. Prolapse of the membrane through the orifice of the tricuspid valve or through the atrial septum was present in seven patients, two of whom were symptomatic. One presented with severe cyanosis which resolved after surgical removal on the basis of the echocardiographic findings. The other presented with atrial arrhythmias which did not improve with removal. The size or behavior of the membrane, including prolapse, did not correlate with either age or presence of pathology of the right heart. The echocardiographic appearance of prominent Eustachian valves is variable. Rarely, when prominent, the valves can cause symptoms associated with obstruction to the right heart, particularly cyanosis or an arrhythmia.

Systemic vascular malformations are a rare cause of congestive heart failure in the infant and newborn infant. Clinical diagnosis is often problematic. Accordingly, this study presents the clinical, radiographic, ultrasound imaging, pulsed and color Doppler features of systemic vascular malformations in six infants. In all cases, color Doppler provided vital information regarding size, location, source of feeding arteries and venous drainage essential for appropriate management of these patients. Color flow Doppler ultrasonography is an accurate and sensitive modality for detecting and evaluating vascular malformations.

Pulmonary atresia with abnormal ventriculoarterial connections in the presence of an intact ventricular septum is rare even in postnatal life. Two cases are described in which this combination of lesions was diagnosed in previable fetuses at autopsy. Both pregnancies were terminated for gross structural abnormalities discovered on antenatal ultrasound scans. In the first case, the pulmonary atresia was associated with intact ventricular septum, a double outlet left ventricle and hypoplasia of the tricuspid valve, right ventricle and arterial duct, a combination of lesions that would appear to be unique. In the second case, there was complete transposition and a hypoplastic left ventricle. The severity of the cardiac lesions in both fetuses was such that it is unlikely that either would have survived to term. In the first case no other malformation was present, but in the second there was also a large encephalocoele secondary to early amnion rupture, and a single umbilical artery. The association of the cardiac lesion with early amnion rupture in this second fetus would appear to be a chance event.

Twins of like sex and concordant for William's syndrome are presented. The first twin presented late with aortic arch atresia and has subsequently developed hypertension associated with renal arterial stenosis. The second twin died with myocardial ischemia late after surgery for supravalvar aortic and pulmonary stenosis.

We describe a male infant with the combination ofan aortic interruption proximal to the brachiocephalic artery and a persistent fifth aortic arch providing a pulmonary-to-systemic shunt. As far as we know, interruption of the aorta at this site has not previously been reported. Documented cases of a persistent fifth aortic arch itself are few, although failure of recognition may account for its apparent rarity.

A syndrome with characteristic facial and skeletal features resulting from a specific deletion of material on the short arm of chromosome 17 was first described by Smith et al in 1982.1 The common findings are brachycephaly, hypoplasia of the middle face, and short broad hands associated with mental retardation. More than 50 cases have been reported, and about one third have congenital heart disease. We report here a patient with atrial and ventricular septal defects together with pulmonary valvar stenosis.

A right-sided modified Blalock-Taussig anastomosis was created using a 5 mm Gore-Tex tube in a 4½ month old infant with unilateral “absence” of the right pulmonary artery. Wide patency of the shunt was confirmed shortly after by angiography, but rarefaction of the peripheral right pulmonary arteries was seen at the age of 2½ years, when corrective surgery was performed. Postoperative hypoperfusion of the right lung, along with severe pulmonary vascular abnormalities seen in a lung biopsy, indicated failure of the two-stage correction in spite of appropriate surgery.