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Biomedical subjects

T Treasure

Publications and source records attributed to T Treasure.

At least 73 records · Page 4Linked to original sources
PubMed1996

Ischaemic preconditioning and cardiac surgery.

OBJECTIVE: This review discusses the phenomenon of ischaemic preconditioning and its potential application to cardiac surgery. The biology of ischaemic preconditioning is explained and the more limited evidence suggesting that the human heart can be preconditioned is discussed. METHODS AND RESULTS: It is now accepted that the heart is capable of short-term rapid adaptation in response to brief ischaemia so that during a subsequent, more severe ischaemic insult myocardial necrosis is delayed-ischaemic preconditioning. The infarct-delaying properties of ischaemic preconditioning have been observed in all species studied. Five minutes of ischaemia is enough to initiate preconditioning and the protective period lasts for 1-2 h. Laboratory experiments have demonstrated that the stimulation of adenosine receptors initiates preconditioning and the intracellular signal transduction mechanisms involve protein kinase C and ATP-dependent potassium channels, although there may be some differences between species. An analysis of studies on myocardial infarction in humans has revealed that some patients reporting angina in the days before infarction have a better outcome and this may be due to the ischaemia causing preconditioning. More direct evidence has come from an investigation of patients undergoing percutaneous transluminal angioplasty in whom the ST-segment changes induced by balloon inflation were more marked during the first inflation than the second. In patients undergoing coronary artery bypass grafting the decline in ATP content during the first 10 min of ischaemia was reduced in patients subjected to a brief preconditioning protocol. CONCLUSIONS: Preconditioning is a powerful and reproducible method of protecting the myocardium from irreversible ischaemic injury. There is now evidence indicating that the human heart can be preconditioned. However, more trials are necessary in patients undergoing cardiac surgery before the role of preconditioning as a means of myocardial protection can be assessed.

Adenosine Triphosphate↗
PubMed1996

Incorporating psychometric measures in selecting and developing surgeons.

Provides a review of the recent literature on the selection and development of surgical trainees and surgeons, and discusses findings on the validity of psychometric measures of ability and personality in such processes. Drawing on this body of research, outlines the pilot project recently completed by the authors at St George's Hospital in London, which sought to test the appropriateness of incorporating psychometrics in supporting the career development of junior doctors applying for surgical training. The results of this pilot study tend to confirm those provided by similar research on surgeons, as well as other clinical groups--that psychometric measures have a significant role to play in aiding the assessment and career development of doctors.

Attitude of Health Personnel↗
PubMed1996

Reciprocal inhibition of nitric oxide and prostacyclin synthesis in human saphenous vein.

1. Angiotensin II (AII) causes contraction of isolated rings of human saphenous vein, responses that are attenuated by the presence of functional endothelium. In this study, we have investigated the mechanisms controlling the release by AII of two endothelial-derived vasorelaxants, prostacyclin (PGI2) and nitric oxide (NO). 2. Myotropic and biochemical changes were measured in response to AII. The biochemical responses measured were the output of PGI2 (as 6-oxo-PGF1 alpha) and of NO (as cyclic GMP). Inhibitors of cyclo-oxygenase (COX; piroxicam) or NO synthase (NOS; L-NAME), were added to the system to determine the influence of endogenous prostaglandins and NO on both myotropic and biochemical responses. Furthermore, to mimic the effects of endogenous, PGI2 or NO, exogenous forms of these relaxants were added, during inhibition of their endogenous release. 3. Contractions of the rings of saphenous vein in response to AII (1-100 nM) were unaffected by treatment with either piroxicam (5 microM) or L-NAME (200 microM) individually. However, when these two inhibitors were used together, there was an increase in the contractions in response to AII. 4. Biochemical analyses revealed that during stimulation by AII, levels of PGI2 and NO were enhanced when synthesis of the other vasodilator was inhibited, suggesting that endogenous NO inhibits PGI2 synthesis and endogenous, PGI2 or another vasorelaxant PG can inhibit NO synthesis. 5. Exogenous PGI2 (as iloprost) or NO (from glyceryl trinitrate) inhibited the increased output of endogenous NO or PGI2 respectively. 6. These results demonstrate the presence, in human saphenous vein, of a mechanism which ensures that levels of vasodilatation are maintained through a compensatory increase in one relaxant agonist when output of the other is decreased. If present in vivo such a mechanism would be important in maintaining saphenous vein graft patency as both PGI2 and NO are not only vasodilators, but inhibit platelet aggregation and myoinitimal hyperplasia, processes implicated in degeneration of graft function.

Angiotensin II↗
PubMed1996

Demographic characteristics of patients undergoing aortic valve replacement for stenosis: relation to valve morphology.

OBJECTIVE: To determine the relative importance of the different causes of isolated aortic valve stenosis in a surgical series, and to relate these to patient characteristics including the rate of insertion of bypass grafts for coronary artery disease. DESIGN: Survey of the clinical and pathological data on patients undergoing aortic valve replacement for isolated stenosis. SETTING: Tertiary care cardiothoracic surgical unit. PATIENTS AND METHODS: 465 adult patients undergoing aortic valve replacement representing a consecutive series in one surgical unit. Retrospective review of patients records and classification of cause of aortic stenosis based on pathological examination of excised valve cusps. RESULTS: 63.7% patients had calcific bicuspid valves, 26.9% tricuspid calcific valves, and 5.4% rheumatic, 2.6% mixed pathology and 1.5% unicommissural valves. The ratio of males to females for bicuspid valves was 1.85:1 and for tricuspid calcific valves 0.76:1. The mean age of patients with bicuspid valves was 64.9 years compared with 73.4 years for those with tricuspid valves. Some 22.3% of patients with bicuspid valves and 44.8% of those with tricuspid valves had sufficient coronary artery disease to necessitate insertion of coronary bypass grafts. The differential rate of insertion of coronary bypass grafts was independent of age. CONCLUSIONS: Bicuspid calcified aortic valves are the predominant cause of isolated aortic valve stenosis followed by tricuspid calcified aortic valves. The sex and age distribution of bicuspid and tricuspid calcific aortic valve stenosis is different. The higher rate of insertion of vascular grafts in tricuspid calcific aortic valves may indicate that risk factors for atherosclerosis enhance cusp calcification in these patients.

Adult↗
PubMed1996

Training surgeons and safeguarding patients.

Surgical trainees need exposure to a wide variety of operations and a chance to operate under supervision. At the same time there is the over-riding responsibility to do the best for our patients. Cardiac surgery is dominated by coronary bypass surgery and the tendency has been to delegate easy coronary cases to trainees and to neglect their experience in other areas. This paper is an audit of trainee exposure and supervision in a training centre. During a 20-month period, 35.2 per cent of cases were delegated; 20.6 per cent to the senior registrar and 14.6 per cent to the registrars. Senior registrars were assisted by the consultant in 19.1 per cent of their cases and registrars were assisted by more senior colleagues in 28.5 per cent of theirs. Most cases delegated to trainees were of low perioperative risk and operations were performed with commensurate low morbidity and mortality. The delegation of valve surgery was disproportionately low in comparison to overall case mix. On the basis of this study, the delegation of cases is being reviewed in the knowledge that with appropriate selection, trainees can gain valuable operative experience without compromising patient-safety.

Aged↗
PubMed1996

The role of echocardiography in the diagnosis of aortic dissection.

Echocardiography is now an integral part of the assessment of patients before, during and after cardiac surgery. For example, mitral valve repair or myectomy would rarely now be contemplated without echocardiography. Echocardiography is essential for the correct diagnosis of valve disease and to plan the appropriate timing of valve surgery, for the assessment of left ventricular function, for the detection of many postoperative complications, and for the follow up after valve surgery or repair of aortic dissection. Although surgeons are increasingly well trained in echocardiography, a specialist in the technique is still required in order to keep abreast of the dramatic advances in technology and interpretation which have occurred over the past five years and which continue unabated.

Aortic Dissection↗
PubMed1995

Resternotomy for bleeding after cardiac operation: a marker for increased morbidity and mortality.

Over a 2-year period from January 1, 1992, to December 31, 1993, of 2,221 patients undergoing cardiac operations in our unit, 85 (3.8%) were reopened for the control of bleeding (9 patients more than once). The incidence of resternotomy in coronary cases was 2.3%, but resternotomy was more than three times as likely in valve cases (odds ratio, 3.4; 95% confidence interval, 2.1 to 5.4). Previous cardiac operation was more common among resternotomy patients than among the remainder (18% versus 9%, respectively; p = 0.018). An identifiable source of bleeding was found in 57 of the 85 patients (67%), but a concurrent coagulopathy was common (45 patients). Resternotomy patients, as a group, had higher preoperative risk scores (Parsonnet) than did the other patients (p < 0.0001), stayed longer in the intensive care unit (p < 0.0001), and had greater requirements for intraaortic balloon counterpulsation (14% versus 3%) and hemofiltration (9% versus 3%) (p < 0.0001 and p < 0.01, respectively). Nineteen resternotomy patients (22%) died in the hospital, a proportion significantly greater than the risk assigned to this group of patients preoperatively (12.8%) (p = 0.008). In contrast, the observed mortality for the other 2,136 patients (5.5%) was significantly less (8.3%) (p < 0.00006). Multiple forward stepwise logistic-regression analysis confirmed resternotomy for excessive bleeding after cardiac operation to be a significant independent predictor of a prolonged stay in the intensive care unit (p < 0.0001), the need for intraaortic balloon counterpulsation (p < 0.0001), and death (p < 0.0001).

Aged↗
PubMed1995

Survival and quality of life in patients with protracted recovery from cardiac surgery. Can we predict poor outcome?

Of all the 2256 adult cardiac surgical patients operated upon during a 12-month period from 1st February 1992 in three units, only 162 (7.2%) spent more than 48 h in the intensive care unit (ICU) (median 6 days, range 3-90). There were 47 deaths in ICU, 7 more before hospital discharge, and a further 10 before the study end-point of one year after surgery. All 98 1-year survivors were at home with 86 of them reporting their quality of life, on formal evaluation, to be within the reference range which we have established for a less complicated cohort of cardiac surgical patients. Prospectively collected physiological measurements were used in a mathematical model to test how well we could predict which patients will die and which of the survivors have a poor quality of life. The algorithm performs well for cardiac surgery patients with a specificity of 98%. If treatment had been withdrawn when death or poor quality of life became predictable, the maximum number of ICU bed days that could be freed was of the order of 2%. The plight of these patients is distressing, but most survive and do well and they are infrequent compared with the large majority who survive to leave hospital after a short ICU stay.

Adult↗
PubMed1995

Which prosthetic valve should we choose?

In this review I concentrate on issues related to prosthetic valves themselves: their development, performance, and durability. For example, mechanical failure or tissue deterioration appear to be intrinsic properties of the valve and are therefore central to my topic, whereas the development, diagnosis, and management of endocarditis are largely independent of the type of prosthesis and are thus not dealt with here. Other outcomes such as stroke are also determined by factors other than the choice of valve, as was cogently argued in papers published during the past year. The papers on tissue valves have a common theme: they document the inevitability of tissue failure, too early for acceptable use other than in old age. The mechanical valves that have stood the test of time have done so because they do not fail.

Animals↗
PubMed1995

Displaying the long-term progression of patients with coronary artery disease.

Cardiac clinicians are often faced with the problem of trying to assimilate details of a patient's long-term history. Case notes are often lengthy, making this process difficult if not impossible in the time available during an outpatient examination. A computer system has been developed to assist with this task. This generates a graphical summary of the principal features of a patient's long-term progression. It gives an overview of how the patient's anginal status has changed, his or her drug treatment and any surgical interventions. The system also allows the clinican to display summaries of diagnostic tests carried out. The system can be used to assist clinical management and speed up outpatient examination. It can also be used to facilitate case conference sessions and has potential for being used in medical education.

Coronary Disease↗
PubMed1995

Shock and dropsy.

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Diagnosis↗