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Biomedical subjects

R D Thomas

Publications and source records attributed to R D Thomas.

At least 109 records · Page 6Linked to original sources
PubMed1982

The relationship between serum potassium and cardiac arrhythmias following cardiac infarction in patients aged over 65 years.

A retrospective analysis was performed of 405 patients, over the age of 65 years, who had been admitted with proven myocardial infarction to a coronary care unit, to investigate the relationship between the serum potassium level on admission and the incidence of cardiac arrhythmias. On admission, 173 (42.7%) patients had a serum potassium of less than 4.0 mmol/l. During the first 24 hours in hospital, 57% of all patients exhibited a disturbance of cardiac rhythm. The incidence of total arrhythmias was independent of the initial serum potassium level, but the mortality rate was 46.2% in those patients with a serum potassium less than 4.0 mmol/l while it was 34.5% in those with a potassium of 4.0 mmol/l or greater. Twelve patients with a serum potassium less than 4.0 mmol/l experienced at least one episode of ventricular fibrillation (6.9%), but only 1 patient with a serum potassium of 4.0 mmol/l or greater had this arrhythmia. The difference in incidence of this arrhythmia was highly significant (p less than 0.001). No patient who experienced ventricular fibrillation was on existing cardiac medication with either a diuretic, beta-adrenoreceptor blocking drug or digoxin. There was no significant difference in the occurrence of other cardiac arrhythmias between low and normal serum potassium groups.

Aged↗
PubMed1981

Influence of sympatholytic drugs on the cardiovascular response to isometric exercise.

1. The effects of single oral doses of various sympatholytic drugs on the heart rate and blood pressure increases during isometric handgrip contraction were studied in six healthy subjects. 2. Bethanidine reduced both the systolic and diastolic increases in pressure. Clonidine reduced the systolic but not the diastolic increase. Oxprenolol alone or in combination with phentolamine or phenyoxybenzamine failed to influence the pressor response. 3. The increase in systemic blood pressure associated with sustained contraction of voluntary muscle appears to be relatively resistant to acute sympathetic adrenoreceptor blockade in man.

Adult↗
PubMed1981

Total body nitrogen and its relation to body potassium and fat-free mass in healthy subjects.

1. The amount of lean tissue in the body can be assessed by measuring total body nitrogen, total body potassium or fat-free mass. To compare these techniques we have measured total body nitrogen, total body potassium and fat-free mass in 91 healthy subjects (62 males, 29 females). 2. Total body nitrogen in the women and civilian men agreed closely with the few values reported previously and was closely related to total body potassium and fat-free mass. 3. The simplest estimate of total body nitrogen in a subject whose body content has not been measured is the mean value for healthy people of the same sex. The standard deviation of individual values about this mean is 253 g. The precision of the estimate can be improved considerably by predicting body nitrogen from fat-free mass (156 g) and somewhat more by predicting it from body potassium (115 g). The error of measuring total body nitrogen directly is approximately 76 g. 4. When an individual's total body potassium is measured in a search for potassium depletion, the observed value must be compared with the value expected if the subject were healthy. The standard deviation of the healthy values about the group means is 408 mmol. The precision of the estimate can be improved by predicting total body potassium from fat-free mass (SD 237 mmol), and rather more by predicting it from total body nitrogen (SD 186 mmol). If gross body composition is normal, measurement of total body nitrogen has little advantage over measurement of fat-free mass by the anthropometric technique. 5. These results suggest that the simpler measure of fat-free mass from body weight and skinfold thickness has a major role in the assessment of total body nitrogen, and thus lean body tissue, in the individual.

Adult↗
PubMed1980

Incidence of coronary artery disease in patients with valvular heart disease.

The case notes, cardiac catheterisation data, and coronary arteriograms of 239 patients investigated for valvular heart disease during a five year period were reviewed. Angina present in 13 of 95 patients with isolated mitral valve disease, 43 of 90 patients with isolated aortic valve disease, and 18 of 54 patients with combined mitral and aortic valve disease. Significant coronary artery disease was present in 85 per cent of patients with mitral valve disease and angina, but in only 33 per cent of patients with aortic valve disease and angina. Patients with no chest pain still had a high incidence of coronary artery disease, significant coronary obstruction being present in 22 per cent with mitral valve disease, 22 per cent with aortic valve disease, and 11 per cent with combine mitral and aortic valve disease. Several possible clinical markers of coronary artery disease were examined but none was found to be of practical help. There was, however, a significant inverse relation between severity of coronary artery disease and severity of valve disease in patients with aortic valve disease. Asymptomatic coronary artery disease is not uncommon in patients with valvular heart disease and if it is policy to perform coronary artery bypass grafting in such patients, routine coronary arteriography must be part of the preoperative investigation.

Adult↗
PubMed1979

Potassium depletion and tissue loss in chronic heart-disease.

Weight-loss, total body-potassium, and total body-nitrogen were measured in 12 men and 15 women with severe chronic heart-disease. Compared with age-matched healthy controls, the men had lost an average of 13 kg in weight, 915 mmol of potassium, and 354 g of nitrogen, whereas the women had lost 5.6 kg of weight, 327 mmol of potassium, and 66 g of nitrogen. Although the potassium/nitrogen ratio in the lost tissue is not precisely known, the loss of nitrogen indicates that most of the potassium loss in men is due to tissue loss and that there is little fall in the intracellular concentration of potassium in either the men or the women.

Body Weight↗
PubMed1979

Echocardiographic pattern of posterior mitral valve leaflet movement after mitral valve repair.

The pattern of movement of the posterior leaflet at the time of opening of the stenosed mitral valve has been described as either anterior or posterior in direction. In 32 patients who underwent mitral annuloplasty, the anatomical features of the mitral apparatus were correlated with the postoperative echocardiographic pattern of movements of the posterior leaflet. Anterior movement of the posterior leaflet was associated with extensive disease of this leaflet, and posterior movement with minimal disease. No relation was found between valve orifice or anterior leaflet mobility and the pattern of movement of the posterior leaflet.

Adult↗
PubMed1979

The cause of the raised plasma urea of acute heart failure.

The concentrations of urea, urate, phosphate and creatinine were measured in the plasma of 30 consecutive patients admitted acutely with heart failure. On admission, 20 had a raised plasma urea, 21 had a raised plasma urate, but only 6 had a raised plasma phosphate and only 6 had a raised plasma creatinine. A further 9 of the patients developed a raised plasma urea after admission. The increase in plasma urea present on admission was greater than expected for the fall in GFR (as indicated by the increase in plasma creatinine). The results for plasma and urine taken together suggest that a major cause of the raised plasma urea was an increased urea production rather than a reduced glomerular filtration rate. There was no obvious relationship between plasma urea and clinical features, or diuretic therapy.

Acute Disease↗
PubMed1979

Compression of superior vena cava associated with aneurysmal dilatation of left atrium.

A patient with rheumatic mitral valve disease and persistently elevated jugular venous pressure (JVP) is described. Angiography revealed a valve-like structure in the superior vena cava (SVC) at the site where a pressure gradient was recorded. At operation, this previously unreported anomaly proved to have been caused by aneurysmal dilatation of the left atrium which exerted traction on the pericardial insertion to the SVC. Disinsertion of the pericardial attachment to the vena cava at the time of mitral valve replacement released the compression. Postoperatively, the JVP became normal.

Bioprosthesis↗
PubMed1977

Failure of saralasin to predict a response to surgery in renovascular hypertension.

Arteriography in two patients with renovascular hypertension suggested fibromuscular hyperplasia, mainly affecting the right renal artery. When saralasin was infused intravenously there was no fall in blood-pressure in either patient. However, both had a raised renal-vein plasma-renin activity on the affected side, relative to the unaffected kidney. Auto-transplantation resulted in a sustained reduction in arterial pressure in both patients. A negative saralasin test should not necessarily exclude further investigation of young patients with severe hypertension.

Adult↗
PubMed1977

Reductive dechlorination of DDT by haem proteins.

DDT1 is converted to DDD by reduced myoglobin (rapidly), cytochrome c oxidase, and a haem-containing undecapeptide derived from cytochrome c. Cytochrome c itself is inactive. This demonstrates that an accessible haem site is necessary for the reaction. Spectrophotometric evidence is presented for an interaction between DDT and the undecapeptide. These results cast light on one of the biological pathways for the breakdown of DDT.

Animals↗
PubMed1976

Fibrinolytic activator in the endothelium of the veins of the lower limb.

The local fibrinolytic acitivity of the femoral, popliteal and soleal veins has been studied using a histochemical technique. The results suggest that the fibrinolytic activity in the soleal veins may be low when compared with that in the femoral and popliteal veins. This may be an aetiological factor responsible for the high incidence of thrombi occurring in the soleal veins.

Aged↗
PubMed1975

Abnormal leucocyte composition and sodium transport in essential hypertension.

Cation transport and electrolyte composition were studied in leucocytes from 17 patients with uncomplicated essential hypertension. Significant increases in cell sodium and water contents, associated with a depression of the rate-constant for active sodium efflux, were found in the hypertensive patients. These abnormalities in cell sodium transport may possibly be related to mechanisms of hypertension.

Adolescent↗
PubMed1975

Abnormal sodium transport in leucocytes from patients with essential hypertension and the effect of treatment.

1. In seventeen patients with untreated essential hypertension the sodium and water contents of leucocytes were significantly increased, whereas the rate constant for ouabain-sensitive sodium efflux was significantly reduced. 2. These abnormalities were not found in fourteen other patients with well-controlled hypertension. 3. Preliminary observations in accelerated hypertension suggest a different pattern of abnormality in leucocyte sodium metabolism.

Adrenergic beta-Antagonists↗
PubMed1975

Leucocyte sodium transport in uraemia.

1. In sixteen patients with severe chronic renal failure the rate constant for total sodium efflux from leucocytes was significantly reduced compared with that in thirty control subjects. This difference lay chiefly in the glycoside-sensitive ('active') moiety of sodium efflux. 2. In sixteen patients receiving regular haemodialysis, the rate constant for total sodium efflux from the leucocyte was significantly greater than in the undialysed uraemic patients though still subnormal. 3. In individual patients, an increase in sodium efflux could be detected as early as 1 week after regular haemodialysis was started. 4. These results are compatible with the existence of a dialysable molecule in uraemic plasma affecting leucocyte sodium transport.

Adult↗