James W. French

An explanation of asymmetric upper extremity blood pressures in supravalvular aortic stenosis: the Coanda effect.

The Coanda effect, the tendency of a jet stream to adhere to a wall, was investigated as an explanation of the unequal pressures in the upper extremities in patients with supravalvular aortic stenosis (SVAS). Of 56 patients with SVAS reviewed, 48 had unequal blood pressures in the upper extremities. The average difference was 18 mm Hg systolic. Although 11 of the 20 patients in the control group (valvular aortic stenosis) had some blood pressure asymmetry, the average difference was 3.5 mm Hg systolic. In valvular aortic stenosis, the velocity of the jet is quickly dissipated beyond the stenotic orifice, preventing any sustained high-velocity stream. However, the smooth, annular narrowing of SVAS creates a “step” between the orifice and the ascending aortic wall which enhances the natural affinity of a jet for a boundary wall and conserves the kinetic energy of the jet stream. In most patients with SVAS, the high-velocity stream is along the right aortic wall, causing disproportionately high pressure in the right arm.

Hemodynamic effects of amrinone in children after fontan surgery

After Fontan repair in children, we performed a prospective, open-label study to evaluate the effect of amrinone on pulmonary vascular resistance (PVRI). Eight patients who underwent the Fontan repair had baseline arterial pressure, left atrial pressure, central venous pressure, and cardiac output measured postoperatively. Hemodynamic measurements were repeated after amrinone 4.5 mg/kg. The PVRI tended to decrease, but the change was not statistically significant. Although the systemic vascular resistance decreased to 802 +/- 222 from 941 +/- 191 dynes centered dot s centered dot cm-5 centered dot m-2 (P < 0.05), mean arterial blood pressure was unchanged. Cardiac index (3.8 +/- 1.2 to 4.7 +/- 1.6 L centered dot min-1 centered dot m-2) and stroke volume index (23.6 +/- 6.7 to 30.5 +/- 8.1 mL centered dot beat-1 centered dot m-2) increased, and heart rate decreased (160 +/- 21 to 151 +/- 24 bpm) (P < 0.05). Colloid transfusion during amrinone bolus administration was 13.9 mL/kg. The mean serum amrinone concentration was 4.2 micro gram/mL at the end of bolus and clearance was 2.24 mL centered dot kg-1 centered dot min-1. Arrhythmias and thrombocytopenia were not noted. We conclude that amrinone administration is effective in increasing cardiac output in children who have undergone a Fontan repair. (Anesth Analg 1996;82:241-6)

Comparison of high pulse repetition frequency and continuous wave doppler echocardiography for velocity measurement and gradient prediction in children with valvular and congenital heart disease

To compare the ability of high pulse repetition frequency and continuous wave Doppler echocardiography to detect the peak velocity of a jet flow disturbance and to predict pressure gradients accurately, two groups of children with valvular or congenital heart disease were examined using both Doppler techniques. The use study group included 84 children or adolescents (aged 1 day to 19 years) who underwent examination in the echocardiography laboratory with both Doppler techniques in a randomized sequence. The peak velocity recorded with high pulse repetition frequency Doppler echocardiography was compared with the peak velocity recorded with the continuous wave technique. The accuracy study group included 41 children or adolescents (aged 1 day to 16 years) who underwent examination with both Doppler techniques at the time of cardiac catheterization. Doppler pressure gradients were calculated from the peak velocity using the simplified Bernoulli equation and were compared with peak instantaneous gradients and peak to peak gradients measured at catheterization. In the use study, a high correlation was found between peak velocities detected by high pulse repetition frequency and continuous wave Doppler echocardiography (r = 0.94, SEE = 0.28 m/s). In the accuracy study, close correlations were found between measured peak to peak pressure gradients and pressure gradients calculated from continuous wave (r = 0.95, SEE = 7.9 mm Hg) and high pulse repetition frequency Doppler echocardiography (r = 0.94, SEE = 8.7 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Video Viewing as an Alternative to Sedation for Young Subjects Who Have Cardiac Ultrasound Examinations

Sedation is often required for extended or quantitative echocardiographic examination of young patients. To test the hypothesis that patient viewing of entertaining videotapes during echocardiographic examinations would reduce the need for sedation and that Doppler pressure gradients so obtained would correspond satisfactorily with subsequent catheterization pressure gradients, 38 patients (age, 5 to 64 months; mean age, 18.6 months) with a variety of cardiac defects were studied. Because of excessive activity, resistance, fear, or crying, all of these patients would have normally been sedated. Instead, an age-appropriate videotape was used for patient viewing. In 35 of 38 patients, complete examinations were obtained with video viewing with no sedation. Twelve study patients later underwent catheterization while receiving sedation. The Doppler pressure gradients obtained while patients were viewing videotapes corresponded well with catheterization (r = 0.94). However, those pressure gradients were higher than those obtained with catheterization (mean, 8.3 mm Hg), but there was only one significant discrepancy of 22 mm Hg. In this series, complete examinations were obtained without sedation in 92% of subjects who would have normally required sedation (p less than 0.001), with minimal reduction in the accuracy of prediction of subsequent sedated catheterization pressure gradients. This suggests that near baseline conditions existed while patients were viewing television. Video viewing during echocardiographic examinations appears to be advantageous.

A child with valproic acid-associated carnitine deficiency and carnitine-responsive cardiac dysfunction.

Valproic acid enhances renal losses of carnitine esters and leads to decreased plasma free carnitine concentrations in many patients receiving valproic acid therapy. However, decreased serum carnitine levels are of unclear pathologic significance, and most children manifest no symptoms of carnitine deficiency. We report a child with valproic acid-associated carnitine deficiency who had severe cardiac dysfunction develop that resolved with carnitine replacement therapy. (J Child Neurol 1992;7:413-416).

Doppler Pressure Gradient Estimation in Children Accuracy, Effect of Activity and Exercise, and the Need for Sedation during Examination

ABSTRACT. Noninvasive estimation of pressure drop has been shown to be an accurate and useful application of Doppler echocardiography. Most accuracy series have used patient‐sedated catherization gradient measurements as the standard of reference. Doppler gradient estimates, however, are commonly made without sedation of the patient when hemodynamics may differ from those present at catheterization. We questioned whether (1) “unsedated” Doppler gradient estimates would correlate in a useful way with “sedated” catheter measurements, (2) Doppler gradient estimates would vary with patient activity, exercise or crying, and (3) Doppler gradient estimates made using chloral hydrate sedation would prove useful in predicting sedated catheter measurements. Twenty‐five infants and children were examined under conditions 1 and 2 above, and 20 under condition 3. Sedated Doppler estimates, performed at the time of catheterization corresponded closely with catheter measurements (r=0.97, SEE=4.8), confirming the accuracy of the Doppler method. Gradients estimated by Doppler without sedation, or with activity, correlated poorly with sedated catheter measurements (SEE=16.2, SEE=34.9, respectively). Use of chloral hydrate sedation for Doppler estimates resulted in good correlation with subsequent sedated catheter measurements. The results demonstrate marked increases in noninvasive Doppler pressure gradient estimates under conditions other than sedation. Clinicians tend to think in terms of sedated catheter‐gradients as the standard of reference for evaluation of severity and need for surgery. Ultrasonic data can only be used if Doppler estimates are performed under similar physiologic conditions; in children this requires sedation.

Lack of postmortem radiographic evidence of nasopharyngeal obstruction in the sudden infant death syndrome

Summary Obstruction of the nasopharynx was determined from postmortem radiographs of 78 infants who were victims of the sudden infant death syndrome and compared to observations in a control group of 22 infants with unexpected but explained death. There was no significant difference in the mean dimensions of the nasopharynx in the two groups. Although obligate nasal breathing is undoubtedly involved in certain instances of infant death, we have failed to find radiographic evidence of obstruction of the nasopharynx as a substantial cause of the sudden infant death syndrome.

The Effect of Hypoxia and Epinephrine Infusion on Arginine Induced Insulin Release

Summary The rapid phase insulin release induced by arginine in the puppy, was inhibited significantly by hypoxia, but not by epinephrine infusion. Based on these data we conclude that elevated epinephrine levels were not a major factor in the inhibition of the arginine effect caused by hypoxia. On the other hand, in the puppy, epinephrine may not produce sufficient alpha adrenergic stimulation to inhibit insulin release.

Multiphasic insulin response to arginine.

Summary Although arginine is known to release insulin, the mechanism is poorly understood. Recently, it has been suggested that glucose-stimulated insulin release involves multiple mechanisms or pools. To determine if similar mechanisms are involved in arginine-induced insulin release, the immediate and more prolonged effects of arginine infusion were investigated in puppies. With intravenous arginine pulses, plasma immunoreactive insulin (IRI) rose dramatically (693% ± 121 of mean control), returning to base line levels within 30 min. With arginine infusions, an initial transient surge of IRI was again noted, but in contrast to the pulse, levels remained elevated throughout the infusion period. The two phases of insulin release observed during prolonged arginine infusion suggest that arginine, like glucose, stimulates insulin release by more than one mechanism.