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Biomedical subjects

R H Jones

Publications and source records attributed to R H Jones.

At least 289 records · Page 16Linked to original sources
PubMed1980

Rest and exercise hemodynamic effects of oral hydralazine in patients with coronary artery disease and left ventricular dysfunction.

To determine the hemodynamic effects of afterload reduction at rest and during upright exercise in patients with coronary artery disease and left ventricular dysfunction, 12 patients were studied before and after taking 50-75 mg of oral hydralazine every 6 hours for 48 hours. Oxygen consumption and heart rate were unchanged from control both at rest and during two work loads on a bicycle ergometer. Cardiac output was significantly increased at rest and during both workloads. The arteriovenous oxygen difference was significantly reduced at rest and during exercise. Pulmonary capillary wedge pressure was also significantly lower at rest and during exercise. Systemic vascular resistance was reduced at rest, and exercise-induced vasodilation was augmented by the administration of hydralazine. Left ventricular end-diastolic volume and ejection fraction assessed by radionuclide angiocardiography were not significantly changed at rest or during exercise after hydralazine. Seven of the 12 patients have maintained clinical improvement during a follow-up of 6-12 months. Hemodynamic improvement provided by oral hydralazine at rest is maintained during moderate exertion in patients with coronary artery disease and left ventricular dysfunction. In selected patients, chronic afterload reduction with oral hydralazine may result in increased cardiac reserve, decreased pulmonary congestion or decreased myocardial oxygen demands, thereby improving or abolishing resting or exertional dyspnea or angina.

Aged↗
PubMed1980

Detecting abnormalities in left ventricular function during exercise before angina and ST-segment depression.

To determine if abnormalities in left ventricular function precede angina pectoris and electrocardiographic evidence of myocardial ischemia, we used radionuclide angiocardiography to measure left ventricular ejection fraction, volumes, cardiac output and wall motion in 10 normal subjects and 25 patients with coronary artery disease at rest and during two levels of upright bicylce exercise. In the patients with coronary artery disease, the first radionuclide study during exercise was performed before and the second after the onset of ST-segment depression. In all normal subjects, the ejection fraction increased more than 5%, the end-diastolic volume increased less than 25% and the end-systolic volume decreased from rest to both levels of exercise. Wall motion was normal at rest and increased with exercise. No patient with coronary artery disease had chest pain or ST-segment depression during the first level of exercise. The ejection fraction either decreased or increased less than 5% in 18 patients, the end-diastolic volume increased more than 25% in nine, the end-systolic volume increased in 19 and a segmental contraction abnormality developed in 14. Hemodynamic and wall motion abnormalities occurred in all patients during the second level of exercise when ST-segment depression was present. During exercise in patients with coronary artery disease, abnormalities in left ventricular function frequently develop before angina pectoris and electrocardiographic evidence of myocardial ischemia.

Adult↗
PubMed1980

Arterial hypoxemia during hemodialysis for acute renal failure in mechanically ventilated patients: observations and mechanisms.

Changes in arterial oxygen tension (PaO2) during hemodialysis have been measured in eight patients with acute renal failure who were being mechanically ventilated. Falls in PaO2 under these circumstances (mean = 22.44%, P < 0.05) suggest that loss of carbon dioxide into the dialyzate is not an important cause of arterial hypoxemia during dialysis. White blood count, platelet count and complement levels have also been measured; there is a dissociation between these parameters and falls in PaO2, suggesting that other, unidentified factors are involved in hemodialysis hypoxemia.

Acute Kidney Injury↗
PubMed1980

Noninvasive assessment of the effects of aorta-coronary bypass grafting on ventricular function during rest and exercise.

Ventricular function was measured by radionuclide angiocardiography during rest and exercise in patients before and approximately 4 months after aorta-coronary bypass grafting. The first group of seven patients continued to have symptomatic chest pain after operation. The second group of 13 patients were asymptomatic after operation but, since they had been studied before operation, consented to postoperative study. Before operation, both patient groups demonstrated similar degrees of myocardial ischemia during exercise as documented by a decrease in ejection fraction, by large increases in end-diastolic and end-systolic volumes, and by exercise-induced wall motion abnormalities. After aorta-coronary bypass grafting, ventricular function in the symptomatic patients was unchanged during rest and exercise. In contrast, ventricular function during rest and exercise in the asymptomatic patients was markedly improved. With exercise, the ejection fraction increased and the exercise-induced wall motion abnormalities seen before operation were abolished. Therefore, aorta-coronary bypass grafting can effectively reverse exercise-induced left ventricular dysfunction in patients with coronary disease. Moreover, the change in left ventricular function demonstrated by radionuclide angiocardiography correlated with the clinical status of the patient groups.

Cardiac Output↗
PubMed1980

Effects of isometric handgrip and dynamic exercise on left-ventricular function.

Radionuclide angiocardiography was used to assess cardiac function during isometric handgrip and bicycle exercise in ten normal volunteers and in 20 patients with documented coronary artery disease. Handgrip stress evoked a small increase in cardiac output that resulted from a concomitant increase in heart rate and no change in left-ventricular function. The most reliable criterion for diagnosis of coronary artery disease by handgrip was development of a new well-motion abnormality. However, abnormal wall motion was observed in only 45% of patients with coronary artery disease and in one of the ten normal subjects. In normal subjects, left ventricular function during bicycle exercise was characterized by an increase in left-ventricular ejection fraction with little change in cardiac volumes. The failure to increase left-ventricular ejection fraction by at least 0.05 identified 19 to 20 patients with coronary artery disease with no false positives. Therefore, bicycle exercise evokes a more dramatic cardiovascular response than handgrip stress and is the preferable stress modality for inducing abnormalities of left-ventricular function for detection of coronary artery disease.

Adult↗
PubMed1980

Autoregressive analysis: a method for detecting electroencephalic changes in newborns to tones.

This report presents an autoregressive technique for detectiong statistically significant changes in brain activity to tones. The change detectin model is applied to stationary time series electroencephalogram samples from sleeping newborn infants. The electroencephalic responses of neonates to tones are quantified and analyzed in terms of t-statistics. Confidence limits applied to averaged t-statistics objectively and reliably defined statistically significant late components in newborns.

Acoustic Stimulation↗
PubMed1979

Progression of diabetic nephropathy.

Although deterioration of renal function in diabetic nephropathy varies considerably from one diabetic to another, its rate is constant in individuals. For each patient there is a linear relation between period (months) which elapses from the time serum creatinine becomes greater than 200 mumol/l and the inverse the inverse of the serum-creatinine. The observation is of practical importance in predicting the time at which end-stage renal failure will develop, so that treatment can be planned in advance.

Adult↗
PubMed1979

Every-other-day acetylmethadol disturbs circadian cycles of human motility.

1-Alpha-acetylmethadol (LAAM) maintenance treatment has been proposed as a favorable alternative to methadone maintenance. With an unobtrusive actometer we recorded two successive 24-h cycles of spontaneous motor activity from 12 patients receiving LAAM every other day, and from five receiving methadone every day. LAAM patients were about 50% more active on days of drug administration than on no-dose days (P less than 0.001). There were no significant day-to-day differences in motility of methadone patients. LAAM administered every other day may significantly modify the human circadian rhythm of spontaneous motility; further research is thus needed before this treatment is widely adopted.

Adult↗
PubMed1979

Therapeutic effect of cimetidine in patients undergoing haemodialysis.

Blood concentrations of cimetidine were measured and the therapeutic effect of the drug assessed patients undergoing maintenance haemodialysis. Thirteen patients were given a single oral 200-mg dose of cimetidine a mean of 2.7 hours before the start of dialysis. Dialysing for 6--12-6 m2 hours led to a mean fall of 71% in blood cimetidine concentration during haemodialysis. Nine patients with various upper gastrointestinal lesions diagnosed endoscopically were treated for up to six weeks with a reduced cimetidine dose of 200 mg 12-hourly; two patients received two courses of treatment. Repeat endoscopy after treatment disclosed satisfactory healing, and the drug did not accumulate. This lower dose regimen is recommended for patients receiving dialysis who develop upper gastrointestinal lesions for which a histamine H2-receptor antagonist is indicated.

Adult↗