Development of a high-precision continuous extracorporeal hemodiafiltration system.

A high-precision hemofiltration system appropriate for use in neonatal, pediatric, or adult patients has been developed. The system incorporates computer-monitored and -regulated pumps for control of blood, dialysate, and drain solutions and weighing scales for measurement of fluid infused into and removed from the patient. The overall accuracy of the fluid infusion and withdrawal is +/- 3.5 grams. The system incorporates four pressure transducers to monitor pressures. It includes alarm limits for pressure, solution volumes versus time, temperature, air leak, and blood detection in the drain effluent. The computer stops all pumps in alarm conditions. The system also can be easily adapted for other extracorporeal procedures such as hemofiltration, ultrafiltration, plasmapheresis, and extracorporeal membrane oxygenation.

Group C streptococcal sinusitis.

The group C streptococci have emerged as important human pathogens. A case of group C streptococcal sinusitis in a 6-year-old girl is reported and four cases of group C streptococcal sinusitis are reviewed. Age less than 18 years, central nervous system complications, and a delay in the institution of adequate therapy were features common to all five cases. Three patients were bacteremic with group C streptococci and two patients died. These cases suggest that when beta-hemolytic streptococci are isolated from sinus culture, serogrouping should be performed. When group C streptococci are identified, appropriate antimicrobial therapy should be instituted and one should be alert for suppurative intracranial complications.

Prolonged myasthenic syndrome after one week of muscle relaxants.

A child developed severe, generalized muscle weakness which persisted for 6 weeks, after receiving muscle relaxants for 1 week while requiring ventilator support. Electrodiagnostic studies indicated a presynaptic disorder of the neuromuscular junction which improved with high-frequency stimulation, similar to findings in Lambert-Eaton syndrome. Muscle specimens exhibited neurogenic targetoid fiber atrophy. Ultrastructure of the neuromuscular junction indicated terminal axon degeneration and atrophy with depletion of the secretory vesicles. Most reported patients with post-ventilator paresis have received steroids and muscle relaxants; muscle weakness commonly has been brief and attributed to steroids. We believe that this reversible myasthenic syndrome probably represents neurotoxicity due to high doses of steroidal nondepolarizing blocking agents; however, available data are insufficient to resolve this controversy.

Epiglottitis in infants less than two years of age.

A retrospective review of 41 children less than two years of age was conducted to characterize the clinical presentation of epiglottitis in this young age group. Up to 25% of all cases of epiglottitis occur in children less than two years of age. The clinical presentation of patients in this young age group is variable. Signs and symptoms not routinely described in children over two years of age with epiglottitis but often observed in infants with epiglottitis include the absence of fever, the presence of only low grade fever, a significant history of antecedent URI, and a prominent "croupy" cough. These same features are often noted in children with the viral croup syndrome. A diagnosis of this life-threatening illness may be made promptly through an awareness of the presenting findings observed in infants. Young infants with epiglottitis can be safely managed with short-term nasotracheal intubation.

Glucose and insulin changes in infants and children undergoing hypothermic open-heart surgery.

Marked hyperglycemia was observed in patients undergoing hypothermic open-heart surgery. To evaluate potential mechanisms responsible for hyperglycemia, paired samples were evaluated for glucose and insulin levels in 3 groups of patients. Group 1 consisted of 8 patients less than 2 years of age undergoing cardiac surgery requiring total circulatory arrest; Group 2 consisted of 9 patients less than 2 years of age undergoing open-heart procedures but not requiring total circulatory arrest; Group 3 consisted of 10 patients greater than 2 years of age, none of whom required total circulatory arrest. All 3 groups had striking hyperglycemia during cardiac surgery and in the first few hours after the operation. Despite elevated glucose levels during surgery, insulin levels failed to increase proportionately in response to hyperglycemic stimulus. Subsequently, in a fourth group of 10 patients less than 2 years of age not undergoing total circulatory arrest, the amount of glucose infused was restricted and they did not have hyperglycemia. In children, osmotic diuresis resulting from hyperglycemia after open-heart surgery may be misinterpreted as an index of satisfactory cardiorenal performance. Accordingly, it is recommended that the diluent added to the pump blood prime solution contain no supplemental glucose; also, intraoperative fluid should consist of a balanced electrolyte solution but no glucose.

Early medical and surgical intervention for tetralogy of Fallot with absence of pulmonic valve.

Tetralogy of Fallot with absent pulmonic valve is a rare but life-threatening syndrome. Children with this complex may have aneurysmally dilated pulmonary arteries which compress the tracheobronchial tree and cause airway compromise and death. This paper reviews the course of 10 children with this syndrome who were seen at our institution from 1962 until the present. Two infants with respiratory distress secondary to tetralogy plus absent pulmonary valve were treated with early aggressive medical intervention followed by operation. After closure of the ventricular septal defect and reconstruction of the right ventricular outflow tract, the pulmonary artery aneurysms were resected. Both children are growing and are well more than 1 year after the operations. Our experience with these two patients suggests that such infants may benefit from this form of therapy.

Late results of reconstruction of the right ventricular outflow tract with porcine xenografts in children.

Thirty-three children, aged 2.5 to 17.5 years (mean, 8.3 years), having xenograft external conduits placed between the right ventricle and pulmonary artery were followed for 1 to 6 years postoperatively (mean, 3.5 years). There were no late deaths in the study group, and no infection of a valved conduit has been demonstrated. Twenty of these children were catheterized during the follow-up period. The gradients from the right ventricle to pulmonary artery ranged from 8 to 90 mm Hg (average, 31 mm Hg). A total of 8 patients were classified as having hemodynamically documented conduit failure, and an additional 2 patients are clinically expected to have conduit failure. This represents a total incidence of 30% xenograft conduit failure in a 6-year follow-up. Although the etiology of this dysfunction is probably multifactorial, factors such as valve size, conduit angulation, and immunological competence bear special consideration. We conclude that although valved external conduits continue to play an important role in the treatment of complex congenital heart disease, a valved conduit with greater longevity is needed for use in children.

Vasodilator therapy for congestive heart failure.

Six patients with severe congestive heart failure were treated with nitroprusside intravenously. Four of the six patients showed salutary responses and were successfully weaned from the NP with marked resolution of symptoms. No adverse side effects were observed. These four patients and one additional child (who did not receive NP) were treated with prazosin by mouth in addition to digoxin and diuretics daily. Two of these patients are entirely symptom free, and additional child is moderately improved, and the fourth patient has shown minimal symptomatic improvement. Despite the severity of their pretherapy symptoms, only one patient has died while receiving oral vasodilator therapy. This preliminary study suggests that afterload reduction may be life-saving in children who are virtually moribund because of congestive heart failure. This improvement can be maintained with oral vasodilator therapy and continuation of classic anticongestive therapy. However, afterload reduction has no effect on the underlying disease. Confirmatory studies are essential before this experimental mode of therapy is accepted for routine use in infants and children.

Measurement of the ohmic electrode-tissue contact resistance and the voltage applied to myocardium.

The electrical impedance of a pulse generator-electrode-heart system is a complex one. By analysis of an equivalent circuit developed for the above, a model was derived to describe the output voltage applied to an implanted electrode. On the basis of the dynamic behavior of the equivalent circuit when a pacing pulse was applied, a method for measuring true ohmic electrode-tissue contact resistance was developed, and a device was constructed to provide an instant digital readout of its value. The value of that risestance varied from 179 to 521 omega in 13 patients. When a variable resistance R, was connected in series with an implanted electrode, and a threshold voltage for every value of R was determined the actual voltage applied to the myocardium was computed for 16 patients.

Nitroprusside and epinephrine for treatment of low output in children after open-heart surgery.

We evaluated the acute hemodynamic effects of treatment of the low output state with sodium nitroprusside and epinephrine in 13 children after intracardiac operation. The 13 patients were selected from a consecutive series of 106 children undergoing cardiopulmonary bypass. They had a cardiac index less than 2.0 L/min/m2, even after an increase in left ventricular filling pressure and during infusion of nitroprusside. Although the nitroprusside brought about a significant increase in cardiac output and decrease in systemic vascular resistance, the cardiac index remained critically low (less than 2 L/min/m2). Epinephrine resulted in a further significant increase in the cardiac index, without a significant change in systemic resistance. This study suggests that in selected patients the simultaneous use of both a vasodilator drug (sodium nitroprusside) and a positive inotropic agent (epinephrine) is advantageous in the short-term treatment of the low cardiac output state after intracardiac operation.

Low-cost daily pacemaker monitoring system.

To reduce the cost of pacemaker monitoring, we developed an inexpensive cardiac pacemaker interval monitor that detects electromagnetic radiation of the electrical pulse generated by an implanted pacemaker. The pulse interval is timed by logic systems and a piezoelectric crystal. Pulse interval is computed to the nearest 0.1 msec. The device is battery powered and can be used at home by the patient to monitor pulse interval daily with little cost after the initial expenditure. The unit may also be used by the physician to detect the stability or constancy of random variation of the pulse interval. From a daily record of measurements of the pulse interval, limits are set by the physician to predict impending battery exhaustion. Eight patients have been monitored for up to 24 months.

Left ventricular performance in the critically ill premature infant with patent ductus arteriosus and pulmonary disease.

Left cardiac dimensions and an index of left ventricular performance, the percent shortening of the internal diameter (%SID) of the left ventricle, were evaluated in premature infants who were asymptomatic, others with pulmonary disease and others with patent ductus arteriosus (PDA). In contrast to controls, left atrial and/or left ventricular end-diastolic dimensions were increased in all infants with clinical criteria of significant PDA. Postoperative dimensions decreased significantly. Percent SID values for normal premature infants (m=33.5%; SD=3.5%) and those with pulmonary disease alone did not differ significantly. In those with clinical criteria of PDA, who were subsequently found to have echocardiographic evidence of left cardiac enlargement, values for %SID were increased. As expected %SID values for individual patients represented a wider range of left ventricular function and/or afterload than for controls. Upon spontaneous or surgical closure of the PDA, %SID returned to normal. A PDA which is associated with left cardiac enlargement exhibits increased %SID, whereas decreasing %SID in the presence of increased dimensions suggests deteriorating myocardial performance. Echocardiography provides valuable insight into the cardiac status of these infants and may contribute to their medical and/or surgical management.

Nitroprusside after open-heart surgery.

The effects of intravenous infusion of sodium nitroprusside were studied in 11 children immediately after open-heart surgery for congenital heart disease. The patients were selected because, following bypass, their cardiac index was below 2,0 L/min/m2 and their systemic vascular resistance exceeded 30 units. In order to eliminate the effects of preload, mean left atrial pressure was maintained at a constant level by blood transfusion. During infusion of nitroprusside the mean decrease of mean arterial pressure was 18.6%, of systemic vascular resistance was 53.7%, and the increase in cardiac index was 76.9%. All children recovered.

Cardiac performance and oxygen consumption during intracardiac operations in children.

Cardiac performance and oxygen consumption in 30 patients undergoing surgical treatment for congenital cardiac disease were determined from intraoperative measurements. Arterial pressure, cardiac index, mean left ventricular hydraulic output power, pulmonary artery oxygen saturation were obtained at average mean left atrial pressures of 8.1 and 15.2 cm H2O after cardiopulmonary bypass in 20 patients. These same variables were measured at an average pulmonary artery saturation of 65 and 75% in 30 patients. A composite of measurements of cardiac performance was desirable to guide precise patient care intraoperatively, especially if myocardial function was compromised. It is suggested that left atrial pressure be maintained at a level that results in a pulmonary artery saturation greater than 65%.