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Biomedical subjects

B T Williams

Publications and source records attributed to B T Williams.

At least 127 records · Page 7Linked to original sources
PubMed1978

Coronary artery surgery: indications and recent experience.

The comprehensive experience of coronary artery surgery in a Cardiothoracic Unit over a 31-month period is reviewed. Hospital mortality for elective bypass grafting was 3.9% overall and 2.5% in those with good pre-operative left ventricular function. Major influences on hospital mortality were pre-operative left ventricular function, extent of coronary artery disease and extent of the surgical procedure undertaken in terms of number of aortocoronary grafts inserted, coronary endarterectomy and particularly concomitant valve surgery or aneurysm resection. Follow-up experience shows 74% of grafted patients to be symptom-free and 85% symptomatically improved one year after surgery with 70% symptom-free and 80% improved at two years. Early post-operative deaths appear related to early graft closure and recurrence of symptoms postoperatively to late graft closure or progression of coronary disease in the native circulation. The study provides a guide to the relative risks of coronary artery surgery for symptomatic coronary artery disease and expected symptomatic results in the early follow-up period.

Adult↗
PubMed1978

Use of electromagnetic flow probes to assess myocardial performance in man.

Aortic blood flow was measured in 14 patients by means of an electromagnetic flow probe placed around the ascending aorta during cardiac surgery. High fidelity left ventricular pressure was monitored directly, 8 different indices of left ventricular function were derived from these measurements, and compared. Peak aortic blood flow correlated with the conventional indices of left ventricular function derived from left ventricular pressure, but better correlations were obtained for the maximum rate of change of power with respect to time. The clinical advantage of the derivation of this index is small and for clinical purposes peak aortic blood flow and the maximum rate of change of flow provide indices of myocardial performance which are directly available from the instrument.

Adolescent↗
PubMed1977

Applications submitted to regional research committees in 1976 and their outcome.

In 1976 regional research committees in England and their equivalent in the Welsh Office judged 608 proposals for funding under the locally organised research scheme. Of these, 521 were new proposals and 87 were resubmissions. Medically and dentally qualified applicants made 451 (87%) of the new proposals; nearly two-thirds came from teaching areas and 21% from staff of academic departments. Two hundred and ninety new proposals were approved, 154 rejected, and 77 were referred back for modification. Approval was commoner for applications from teaching areas, from medical staff, and for the less expensive projects. Some regional committees did not support research into the organisation of health services. Under a quarter of the resubmitted projects were rejected. The scheme is not yet used by a wide range of health-care professions. Medical staff in teaching areas still use it most. In some regions prospective researchers, especially those without previous experience, need a comprehensive and easily identifiable counselling service, so that the fund may be exploited in the way originally intended and the number of unsuccessful proposals reduced.

England↗
PubMed1977

Twelve months of deputising: 100 000 patient contacts with eighteen services.

An analysis of a 1-in-5 sample of nearly 500 000 patients contacts with 18 deputising services showed considerable variation in the way cells were handled. Telephonists, usually work on shifts including at least one operator who was a trained nurse handled, without sending a deputy, between 3% of new calls at one service and 19% at another. In one service, 19% of visits were made by deputies who were general practitioners; in another, 78%. At least 42% of patients visited by one service were apparently seen within one hour; 74% by another service. The proportions referred to hospital varied from 9% to 16%. The use of deputising services continues to grow; there is as yet no substantiated evidence of shortcomings in the care they provide. The possibility of reviewing the activity of the services, with the use of such indices as those described, might enable present limitations on their use to be lifted.

Community Health Services↗
PubMed1977

Effects of PEEP on cardiovascular dynamics after open-heart surgery: a new postoperative monitoring technique.

The circulatory effects of incremental increases in positive end-expiratory pressure ventilation (PEEP) were assessed on 11 occasions in post-operative cardiac surgical patients by phasic aortic blood flow measurements and high-fidelity pressure recordings from which flow and pressure-flow derivatives of cardiac performance were calculated. At 15 cm H2O PEEP, mean arterial blood pressure was decreased by 10%, stroke volume and cardiac output by 15%, and peak left ventricular power by 21%. Although these indices promptly returned to control levels when PEEP was discontinued, levels of PEEP above 10 cm H2O should be used with caution for this group of patients.

Adolescent↗
PubMed1977

A monitor for the continuous assessment of left ventricular performance after open-heart operations.

A cardiac monitoring system has been developed that incorporated phasic aortic blood flow measurement by an extractable electromagnetic flow probe and high-fidelity arterial blood pressure recordings. Cardiac output, stroke volume, and peak aortic blood flow are measured continuously; using logarithmic amplifiers, the pressure-flow derivatives of left ventricular function, such as cardiac power and stroke work, are obtained beat by beat. This monitor is used to follow the postoperative course of patients undergoing cardiac operations and to evaluate the hemodynamic effect of therapeutic agents.

Cardiac Surgical Procedures↗
PubMed1977

Urinary excretion of free noradrenaline and adrenaline in trained and untrained men.

Measurements of free noradrenaline and adrenaline were made in the urine of 28 men sampled after rest and exercise prior to, and following six and twelve weeks of an excercise programme. The training consisted of thirty minutes of running and walking four times per week at an intensity estimated at 75% of the age-predicted maximum heart rate. A fifteen minute standardized cycle ergometer work test was conducted on all subjects prior to the training and following six and twelve weeks of training. Noradrenaline and adrenaline excretions in the urine were measured before and after the work test.

Adult↗
PubMed1977

Haemodynamic effects of salbutamol and nitroprusside after cardiac surgery.

The haemodynamic effects of a continuous intravenous infusion of salbutamol (15 to 30 microgram/min) and nitroprusside (50 to 100 microgram/min) were compared in 9 patients after cardiac surgical operations. The mean falls in left atrial pressure and systemic vascular resistance were similar with the two drugs but salbutamol caused a greater increase in heart rate, maximum acceleration of aortic blood flow, and maximum rate of change of left ventricular power. Because these differences would cause greater myocardial oxygen consumption with salbutamol and because the infusion of salbutamol is less easily controlled, nitroprusside is the preferred drug after cardiac operations.

Adult↗
PubMed1977

Myocardial preservation during aortic valve surgery. Assessment of five techniques by cellular chemical and biophysical methods.

Five different types of myocardial protection were employed in this series of 168 patients undergoing aortic valve replacement. Two methods of assessing myocardial preservation were used: cellular biological estimations and quantitative polarization measurements. Both parameters showed that either of two methods, continuous perfusion at 32 degrees C. with a beating heart or cardioplegic hypothermic arrest, protected the myocardum best. Intermittent perfusion at 30 degrees C. with a fibrillating heart was the worst means of preservation. Our investigations (both clinical and experimental) have also shown that changes in birefringence, indicative of deteriorating myocardial function, are often detectable before parallel cytochemical changes are apparent.

Adenosine Triphosphatases↗
PubMed1976

Effect of isoprenaline and nitroglycerine on pressure time indices and coronary graft blood flow in man.

In five patients studied 1 to 3 d after coronary artery surgery isoprenaline and nitroglycerine have been used to alter the systolic (TTI) and diastolic (DPTI) pressure time indices. A close correlation with the predicted relationship between diastolic coronary graft flow and the DPTI/TTI ratio has been demonstrated during isoprenaline-induced tachycardia. Nitroglycerine reduced diastolic coronary graft resistance and increased the DPTI/TTI ratio, effects which are desirable for the relief of angina.

Adult↗
PubMed1975

A cardiac monitor combining flow and pressure measurement.

Continuous measurements on patients after cardiac surgery are usually limited to blood pressure and ECG. This article describes a new monitor which combines instantaneous arotic flow and arterial pressure measurements to derive stroke volume, ventricular power, stroke work, and an indication of left ventricular afterload. The methods used to obtain the new derivatives are discussed and clinical applications described.

Aorta↗