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Biomedical subjects

J R Stewart

Publications and source records attributed to J R Stewart.

At least 163 records · Page 9Linked to original sources
PubMed1982

Effect of infarct size limitation by propranolol on ventricular arrhythmias after myocardial infarction.

These experiments show that pretreatment with propranolol was able to achieve significant infarct size reduction in this particular animal model of LAD occlusion followed by reperfusion through a critical stenosis. Despite infarct size reduction, the propranolol pretreatment prolonged the time course of spontaneous ventricular arrhythmias after acute myocardial infarction in the conscious dog. In contrast to this, propranolol pretreatment did not appear to protect against inducible ventricular arrhythmias in the late postinfarction period in the conscious dog. While it is, of course, impossible to extrapolate the results of animal studies to the clinical situation, future clinical studies designed to limit infarct size by pharmacologic intervention should specifically address the question of electrophysiologic instability after myocardial infarction, both in the early and late phases. The possibility exists that pharmacologic limitation of infarct size may preserve viable but potentially jeopardized areas of myocardium, leaving the risk of subsequent malignant arrhythmias and sudden death.

Animals↗
PubMed1982

Hemodynamics and renal function following experimental suprarenal vena caval occlusion.

In this study, the cardiovascular and renal effects of acute suprarenal caval occlusion were investigated in dogs. Marked hemodynamic effects were noted, with an immediate 60 per cent reduction in cardiac output and a 26 per cent drop in mean systemic arterial pressure. In spite of these, there was only a transient disturbance of renal function which had resolved both biochemically and structurally by the end of two weeks. The relevance of these findings to acute occlusion above the renal veins in humans has been reviewed, and we conclude that the Greenfield filter may be inserted in the suprarenal vena cava when indicated with little likelihood of an increase in mortality from recurrent embolism.

Animals↗
PubMed1982

Clinical results of suprarenal placement of the Greenfield vena cava filter.

Twelve patients have had Greenfield vena cava filter placement above the renal veins since 1975. The indication for placement was most commonly contraindication to anticoagulation or recurrent pulmonary embolism during treatment. The follow-up consisted of physical examination, isotope phlebography-lung scan, venous Doppler evaluation, serum specimen evaluation of renal function, and abdominal roentgenograms. The follow-up averaged 16.9 +/- 6.2 months (range 5 weeks to 58 months) in 10 patients. Five patients died after filter insertion, but no death was attributable to filter placement or recurrent embolism. Renal function was unchanged in all patients. Recurrent embolism was documented postoperatively in one patient. Migration of the filter was not observed. The vena cava was demonstrated to be patent in all patients. Two patients had evidence of embolus trapped in the filter.

Adult↗
PubMed1981

Oral flecainide acetate for the treatment of ventricular arrhythmias.

The antiarrhythmic efficacy and safety of oral flecainide acetate were assessed during a controlled, short-term dosage-maintenance study. Thirteen patients with chronic ventricular ectopy entered a placebo control period, and 11 with persistent, frequent (greater than 600 per 12 hours) premature ventricular complexes (PVCs) advanced to drug therapy. Of 10 patients completing a trial of different doses, nine responded completely, with a mean PVC suppression of 98,3 per cent. Repetitive PVCs were eliminated. The mean effective dose was 189 mg per 12 hours, and the effective plasma concentration before administration of a dose averaged 635 ng per milliliter. One patient responded partially (68 per cent of PVCs suppressed). Flecainide continued to be effective and well tolerated at the end of a two-week outpatient trial in the nine complete responders, maintaining an average PVC suppression of 94.6 per cent. The PR and QRS intervals were mildly prolonged. The echocardiographic ejection fraction was unchanged during treatment. The elimination half-life was long - 18.8 +/- 3.8 hours. Flecainide thus appears to be a highly effective and well-tolerated antiarrhythmic agent with favorable pharmacokinetics.

Administration, Oral↗
PubMed1981

Combined modality therapy with conservation of organ function in childhood genitourinary rhabdomyosarcoma.

Recent refinements in the multimodal therapy of childhood genitourinary rhabdomyosarcoma have produced striking improvements in long-term survival rates while still preserving pelvic organ function in the majority of cases. Three illustrative cases of childhood pelvic rhabdomyosarcoma are presented. Chemotherapy and surgical staging are employed in all 3 cases, with 2 of the cases requiring additional local tumor excision and intraurethral radiation for control of residual microscopic tumor. While long-term follow-up has not been achieved, all 3 patients have had their pelvic organs preserved and remain tumor-free in follow-up periods ranging from twelve to twenty-four months after the initial diagnosis.

Child, Preschool↗
PubMed1980

Oral and intravenous bretylium disposition.

To compare the oral and intravenous disposition of bretylium tosylate in man, 10 normal male subjects were randomly assigned single doses of 5 mg/kg bretylium tosylate either orally or intravenously and crossed over 2 wk later to the opposite route (20 studies). Each experiment included sampling for drug in serum and urine over 48 hr. Bretylium tosylate was assayed by gas chromatography. Kinetic analysis provided the following mean [coefficient of variation] results: 100FPo, 22.6% [40.2%]; ClrIV, 300 ml/min [27.8%]; ClrPo, 1.268 mg/min [54.8%]; ClBIV, 299 ml/min [31.9%]; f, 101% [8.7%]; Vdss, 3.37 l/kg [30.5%]; lambda lIV 0.0510 [12.8%]; lambda lPG, 0.115 [52.7%]hr-1; elimination half-life (t 1/2) after intravenous bretylium tosylate, 13.6 hr, and after oral bretylium tosylate, 6.0 hr (harmonic means). Bretylium tosylate binding to plasma proteins in normal volunteer samples was found to be negligible. The results indicate extensive tissue binding of bretylium tosylate. Oral doses of bretylium tosylate are only partially absorbed. Bretylium tosylate is eliminated entirely by the kidneys as unchanged drug. The greater renal clearance after oral than intravenous bretylium tosylate, and the greater elimination rate constant and shorter oral bretylium tosyulate t 1/2 are of interest but no explanation is available.

Administration, Oral↗
PubMed1978

Congenital aortic stenosis: ten to 22 years after valvulotomy.

Between 1956 and 1967, 34 patients, aged 2 months to 40 years, underwent aortic valvulotomy under hypothermia for congenital aortic stenosis. There were two early and five late deaths. Twenty-seven patients were followed up for a mean of 15 years. Thirteen patients had no subsequent operation: 11 are asymptomatic, seven with mild aortic insufficiency. Ten patients have had aortic valve replacement (AVR), one revalvulotomy, three will require AVR. Three late deaths were sudden. The literature has been reviewed for data on mortality, endocarditis, aortic insufficiency, and reoperation. Operation improves longevity, but does not restore it to normal. Aortic valve replacement in children carries a poor prognosis, possibly reflecting severity of disease. The chances of reoperation after ten years are 20% to 40%. Valvulotomy must, therefore, be regarded as the first in a possibly lifelong series of operations.

Adult↗
PubMed1977

Pulmonary artery banding for ventricular septal defect with pulmonary hypertension.

Sixty children in this series underwent pulmonary artery banding (PAB); isolated ventricular septal defect (VSD) was present in 24, and 20 were corrected seven months to ten years and eight months after PAB. Other anomalies were present in 37, and 15 were eventually totally corrected. Survival after PAB was 90% (95.8% with isolated VSD), and 94.3% (95% with isolated VSD) after total correction. Mean age at banding was 12.9 months, and 52.6 months at debanding. All patients underwent catheterization before PAB; 39 underwent catheterization after PAB, and ten after total correction. Pulmonary artery blood pressure was reduced from 53.5 mm Hg to 25.3 mm Hg by banding. Most patients had only moderately increased pulmonary blood flow. Banding at the altitude of Denver (1,600 m) appears to be an effective means to convert high-risk infants into lower-risk children for total correction. The cumulative mortality for two-stage treatment of VSD was 8.3%.

Altitude↗
PubMed1977

Combined therapy for endometrial carcinoma preoperative intracavitary irradiation followed promptly by hysterectomy.

A group of 99 patients with endometrial cancer clinically confined to the uterus has been treated with preoperative adjunctive intracavitary irradiation followed within 72 hours by total abdominal hysterectomy and bilateral salpingoophorectomy. Those patients with poorly differentiated tumors, deep myometrial invasion, cervical involvement, or pelvic metastasis were then considered for external beam radiotherapy to the whole pelvis because of the increased risk of involvement of pelvic nodes or other pelvic structures. Only one of 16 patients so treated has failed in the pelvis. The overall Berkson-Gage actuarial survival at 3 years, uncorrected for death from intercurrent disease, is 85.8%. No vaginal recurrences have been identified. Although this series has not been randomized, it appears that there has been a reduction in vaginal and pelvic recurrences when compared with patients reported by others who have received no adjuvant radiotherapy. The low recurrent rate and favorable survival in this group of patients was achieved with low morbidity from this treatment technique.

Castration↗
PubMed1976

Patent ductus arteriosus ligation and respiratory distress syndrome in premature infants.

Ligation of a patent ductus arteriosus was carried out in 22 premature infants, 20 with concomitant respiratory distress. The duration of high-volume shunting is critical in determining the prognosis for these infants. Because of the low surgical mortality and morbidity and the high incidence of bronchopulmonary dysplasia in babies managed conservatively, infants with respiratory distress syndrome (RDS) who are respirator dependent should undergo ligation as soon as the presence of large left-to-right shunting is detetmined. Premature infants without RDS or those with mild RDS who are not respirator dependent can be managed medically or with elective ligation. Surgical intervention is strongly indicated in patients with persistent congestive heart failure and respiratory failure. Echocardiography offers an accurate and risk-free approach to the early diagnosis of a large left-to-right shunt through the ductus.

Bronchial Diseases↗