Search PubMed⌕ Search

Biomedical subjects

L George

Publications and source records attributed to L George.

At least 91 records · Page 5Linked to original sources
PubMed1983

Congenital heart disease and pulmonary artery hypertension. I. Pulmonary vasoreactivity to 15% oxygen before and after surgery.

Pulmonary vasoreactivity at sea level was studied in 22 children before and in 15 children after corrective cardiac surgery for congenital heart disease and pulmonary artery hypertension; 8 children were studied both before and after cardiac surgery. During cardiac catheterization in 28 children, pulmonary and systemic hemodynamics were determined in room air and during breathing of 15% oxygen, which corresponds to a maximal hypoxic level commonly encountered during airplane travel. Before surgery, 19 of 22 children tolerated 15% oxygen (O2), which caused the following hemodynamic changes from room air status: the ratio of pulmonary to systemic arterial pressure increased from 0.70 to 0.78 (p less than 0.05), the ratio of pulmonary to systemic flow decreased from 2.2 to 2.0 (p greater than 0.05) and the ratio of pulmonary to systemic vascular resistance increased from 0.33 to 0.40 (p less than 0.02). In two children, severe pulmonary vasoconstriction developed within 5 minutes of 15% oxygen administration, requiring immediate discontinuation of hypoxia; neither patient had lasting deleterious effects. There was no evidence of increased pulmonary vasoreactivity in children with Down's syndrome compared with genetically normal children. After corrective surgery in 15 children (including both of the hyperreactors), no significant pulmonary vascular response to 15% oxygen was found. It is concluded that, in a small number of children with unrepaired congenital heart disease and pulmonary artery hypertension, pulmonary vascular hyperreactivity can be induced by breathing 15% oxygen; this reaction is life-threatening but reversible with the administration of 100% oxygen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Vascular consequences of subclavian artery transection for the treatment of congenital heart disease.

The acute and chronic consequences of subclavian artery transection were analyzed in the noninvasive vascular laboratory. Twenty-eight patients (aged 1 day to 4 2/12 years, median 2 months) underwent subclavian artery transection (23 Blalock-Taussig, four subclavian aortoplasty for coarctation or interrupted arch, and one division of aberrant left subclavian). Bilateral systolic brachial artery pressure (BAP) was measured by Doppler instrumentation to obtain a "BAP index": BAP1 = (operated side BAP/control side BAP). Velocity waveform tracings and bilateral forearm skin temperatures were also obtained during studies before and sequentially after operation (4 hours to 12 years). Five patients underwent exercise testing of the upper extremity. Nine patients were studied for manual preference and limb development. Before operation, mean BAP1 was 0.99. Immediately (4 to 48 hours) after operation, mean BAP1 was 0.39. Three weeks postoperatively, BAP1 was 0.62, and thereafter it remained at 0.70. All differences between preoperative, immediate postoperative and late postoperative BAP1 are significant (p less than 0.001). Exercise resulted in a significant (p less than 0.01) increase in BAP bilaterally. Forearm skin temperature was initially lower (p less than 0.01) on the operated side but approximated the control side by 1 week. Limb girth was less on the operated side (p less than 0.01), without evidence of altered manual preference. In conclusion, subclavian artery transection causes permanent reduction in BAP1. The affected limb appears to respond to increased metabolic demand by increasing limb blood flow.

Arm↗
PubMed1983

Coarctation in the first year of life. Patterns of postoperative effect.

From 1975 to 1982, 31 infants were operated upon in the first year of life for aortic coarctation and congestive heart failure. Operations performed were resection and end-to-end anastomosis (RETE) in 14, subclavian flap aortoplasty (SFA) in six, patch aortoplasty (PA) in five, and other procedures in six. Thirty of the thirty-one (97%) survived the operation. To assess the effect of operation, 26 infants were studied noninvasively with Doppler arm-to-leg pressure measurements at rest and with stress. Preoperatively, the median arm-to-leg gradient at rest was 77 mm Hg. Serial postoperative Doppler studies demonstrated progressive changes in arm-to-leg pressure gradients: 69% had residual arm-to-leg gradients that spontaneously resolved, 13% had residual gradients that persisted, 13% had progressive increase in gradient, and one child had neither early nor late gradient. Stress testing often unmasked gradients not present in the resting state. No differences were noted among the three surgical groups: RETE, SFA, and PA. From our experience, we have made four conclusions with regard to repair of coarctation of the aorta in infants. First, surgical survival is expected. Second, the effect of the operation is dynamic, with four patterns defined: (1) complete relief of coarctation, (2) transient residual coarctation, (3) persistent residual coarctation, and (4) recurrent coarctation. Third, optimal surgical therapy seems to be an eclectic approach. Fourth, physiological evaluation of coarctation in infants can be obtained by Doppler techniques in conjunction with stress testing.

Aortic Coarctation↗
PubMed1982

Umbilical vascular catheters: localization by two-dimensional echocardio/aortography.

Umbilical vascular catheters are often necessary in the care of critically ill neonates. Position of the catheter tip is usually determined by roentgenography. Location of the umbilical arterial or venous catheter was determined by 2-dimensional echocardio/aortography in 55 consecutive infants and was compared to localization by thoraco-abdominal roentgenography. Most of the infants (76%) had respiratory distress syndrome or congenital heart disease. Echocaortographic localization of the umbilical arterial catheter correlated very closely (N = 50, sr = .90) with roentgenographic determination. For localization of the tip of the umbilical venous catheters, echocardiography was more accurate than roentgenography (employing contrast echocardiography for confirmation of cardiac chamber position). Two-dimensional echocardio/aortographic localization of the tip of indwelling umbilical vascular catheters is as accurate as roentgenography in the arterial system and more accurate than x-ray for umbilical venous catheters. Echocardio/aortography is superior to roentgenography (in localizing the catheter tip) because it 1) avoids ionizing radiation, 2) makes positioning of the patient unnecessary, 3) allows visualization of the catheter in relation to cardiovascular structures, and 4) may allow demonstration of intraarterial thrombo-emboli.

Aortography↗
PubMed1982

Two-dimensional echocardiographic visualization of the aortic arch by right parasternal scanning in neonates and infants.

Echocardiography has previously been of limited use in visualizing the aorta in neonates and infants. Using a new technique--right parasternal scanning--the aortic arch and brachiocephalic vessels were studied in 50 children under 18 months of age. Complete visualization was accomplished in 47 patients including those 1) under 1,000 grams, 2) with indwelling endotracheal tubes, 3) who had D- or L-transposition, or 4) with right or double aortic arch. Inadequate studies were related to bilateral pneumothorax (2 neonates) and lack of cooperation (1 infant). Close correlation was obtained between images of the aorta by echocardiography and by angiography. Two-dimensional echocardiography can now visualize the aortic arch in small infants and children. In conjunction with another new technique--simultaneous Doppler flow-detection--coarctation of the aorta can be completely evaluated noninvasively in children of all ages including neonates.

Aorta, Thoracic↗
PubMed1982

Interaction between antidepressants and perphenazine in psychiatric inpatients.

In a study of 99 patients receiving amitriptyline or nortriptyline alone and 60 patients receiving one of these antidepressants in combination with perphenazine, the patients receiving the combination medication had up to 70% higher antidepressant plasma levels than patients receiving the antidepressant alone. The groups did not differ significantly in sex, age, smoking behavior, or antidepressant dose level. Due to the possibility of side effects from such combination medication, the authors recommend that depressed patients not responding to the tertiary amine tricyclic antidepressants receive a trial of high doses of the drugs before antidepressant-neuroleptic combinations are administered.

Adult↗
PubMed1979

Assessment of patent ductus arteriosus shunting using diastolic pressure analysis.

Ductal shunting significantly affected the time necessary for aortic diastolic pressure to fall to one-half an initially selected value (t1/2). Fourteen premature infants with clinical evidence of left-to-right ductal shunting had a mean t1/2 of 277 msec (range 133 to 383 msec) compared with a mean t1/2 of 455 msec (range 332 to 567 msec) in 14 neonates with no clinical evidence of ductal shunting (P less than 0.01). Seven older infants with ductal shunting confirmed at cardiac catheterization had a mean t1/2 of 360 msec (range 240 to 392 msec). Infant catheterization data and animal studies are suggestive of an inverse relationship between the magnitude of shunt and the t1/2. The t1/2 determined by diastolic pressure analysis is a useful method for serial evaluation of ductus arteriosus shunting.

Child, Preschool↗
PubMed1978

Use of high-pressure liquid chromatography to determine plasma levels of metronidazole and metabolites after intravenous administration.

A rapid and sensitive high-pressure liquid chromatography assay for metronidazole and its two principle metabolites, 1-(2-hydroxyethyl-2-hydroxymethyl)-5-nitro-imidazole [hydroxy metabolite] and 1-acetic acid-2-methyl-5-metronidazole [acid metabolite], was developed. The retention times observed were 5.7, 3.3, and 4.5 min, respectively. A reverse-phase muC(18) Bondapak column using a solvent system of methanol, acetonitrile, and 0.005 M pH 4 potassium dihydrogen phosphate (4:3:93, vol/vol) was used to achieve separation of the three compounds. Patients receiving metronidazole therapy were given a loading dose of 13.6 mg of drug per kg intravenously over 1 h, followed by a maintenance dose of 1.43 mg/kg per h. The range of metronidazole concentrations observed was 6.8 to 47.5 mug/ml. These levels are well above the minimal inhibitory concentrations of most clinically significant anaerobic bacteria including Bacteroides fragilis. Little of the acid metabolite was observed in the plasma. The concentration of hydroxy metabolite ranged from 1.6 to 16 mug/ml. The latter may represent an additional source of antimicrobial activity since the hydroxy metabolite has approximately 30% the biological activity of metronidazole.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Surgical closure of the tricuspid valve for pulmonary atresia, intact ventricular septum, and right ventricle to coronary artery communications.

A surgical approach is reported for a patient with pulmonary atresia, intact ventricular septum, and right ventricle to coronary artery communications through sinusoids. A shunt procedure was performed at two days of age; the right ventricular outflow tract was not opened. At subsequent catheterization, the tricuspid valve was temporarily closed with a balloon catheter and no change was seen in the ECG. At five months of age, the right ventricle was plicated and a patch was sewn over the tricuspid valve. One year after surgery, neither the right ventricular cavity nor the sinusoids could be demonstrated at angiocardiography; ECG changes of left ventricular ischemia have resolved, and the child is growing normally.

Cardiac Catheterization↗
PubMedDate not supplied

Direct and continuous measurement of relational learning in human Pavlovian conditioning.

Three experiments were conducted employing a continuous measure of conditional stimulus/unconditional stimulus (CS/US) contingencies as perceived by the subject (i.e., subjective contingency or SC). It is argues that direct measurement of relational learning, as indexed by SC, can lead to a better understanding of Pavlovian conditioning processes. The first two experiments applied this approach to a methodologic controversy, raising the debate from a procedure-based argument to testing what the subject actually learns about CS/US relationships. While the issue was not resolved, testable hypotheses for future research were generated from the data. The third experiment contrasted the contingency stimulus-stimulus (S-S) account of Pavlovian conditioning with an earlier stimulus-response (S-R) contiguity-reinforcement account. In this experiment, both SC and skin resistance were measured. Evidence for the existence of both cognitive-propositional and response-learning processes in conditioning was obtained.

Adult↗
PubMedDate not supplied

Partial anomalous left pulmonary artery: new evidence on the development of the pulmonary artery sling.

Clinical and angiographic data of a child with a unique form of partial anomalous left pulmonary artery are reported. Because the anomalous pulmonary artery does not run posterior to the trachea, this malformation is not associated with airway obstruction, as are all other forms of anomalous left pulmonary artery described to date. This case strengthens our understanding of the development of the pulmonary artery sling.

Heart Septal Defects, Ventricular↗