Biomedical subjects

Kenneth M Taylor

Publications and source records attributed to Kenneth M Taylor.

24 records · Page 2Linked to original sources

PubMed2002

Translational and rotational forces on heart valve prostheses subjected ex vivo to a 4.7-T MR system.

PURPOSE: To assess the magnetic field interactions on 60 heart valve prostheses subjected to a 4.7 T MR system. It addresses the question of whether heart valves deemed safe at 1.5 T may pose safety hazards as patients are exposed to increased static magnetic fields. MATERIALS AND METHODS: Ex vivo testing was performed to evaluate translational and rotational forces on 60 heart valves using previously described techniques. RESULTS: Translational forces were detected on 58 heart valves ranging from 0.5 degrees to 7.5 degrees. Seven valves exhibited paramagnetic/weakly ferromagnetic behavior, and 51 valves exhibited diamagnetic behavior. Rotational forces were observed for 46 valves. CONCLUSIONS: Criteria previously used for safety assessment of heart valve prostheses and expressed in terms of magnetic forces suggest the forces observed in this study are compatible with the safe use of these valves in magnetic resonance (MR) systems with static fields up to 4.7 T.

Heart Valve Prosthesis↗

PubMed2002

Heparin-induced hyperkalemia after cardiac surgery.

Surgeons are increasingly faced with patients suffering from complicated pathology in multiple organ systems, to which multiple therapeutic agents with complex adverse effects are often prescribed. We face a daily challenge in maintaining an up-to-date knowledge of these complications. Heparin is widely used in surgical practice, yet our awareness of its adverse effects, other than bleeding and thrombocytopenia, remains poor. We will present an example of heparin-induced hyperkalemia following administration for cardiopulmonary bypass and intraaortic balloon pump prophylaxis. This is a rare but serious complication of heparin therapy, not usually reported in the context of a cardiac surgical patient. We will also discuss the renal physiology leading to hyperkalemia and the options available for its management.

Angina, Unstable↗

PubMed2002

Excess coronary artery bypass graft mortality among women with hypothyroidism.

BACKGROUND: The impact of thyroid disease on patients undergoing coronary artery bypass grafting has been reported in only small series of selected patients. METHODS: We investigated 30-day mortality of patients on thyroxine replacement therapy undergoing isolated coronary artery bypass grafting from 1993 to 2000 and identified variables of importance for outcome. RESULTS: A total of 3,631 patients (606 women) had isolated coronary artery bypass grafting of whom 58 patients (30 women) were treated for hypothyroidism. The mortality rate was higher among women with thyroxine replacement (16.7%, 95% confidence interval [CI] 5.6 to 34.7) than those without thyroxine replacement (5.9%, 95% CI 4.1 to 8.2; p = 0.02) and no difference between men with (3.6%, 95% CI 0.1 to 17.8) and without (2.6%, 95% CI 2.0 to 3.2) thyroxine treatment (p = 0.8). Intake of diuretics (p < 0.001) was directly associated with mortality whereas intake of aspirin (p = 0.01), levothyroxine dose (p = 0.03), and serum thyroxine level (p = 0.01) were inversely associated with mortality among women on thyroxine replacement. CONCLUSIONS: Women on thyroxine replacement therapy undergoing coronary artery bypass grafting had an increased mortality rate. We speculate that insufficient thyroid hormone replacement could partly play a role in this outcome.

Aged↗

PubMed2002

The effect of methanol washing of plasticized polyvinyl chloride on biomaterial-contact-mediated CD11b (mac-1) expression in a rat recirculation model.

Our objective was to assess whether using a methanol wash to reduce the level of plasticizer present on the surface of medical-grade polyvinyl chloride (PVC) has a moderating effect on the expression of CD11b (mac-1) on neutrophils in rats undergoing recirculation. The study was carried out on 3 groups of 10 adult male Sprague-Dawley rats weighing between 350 and 450 g. In the 2 test groups, the animals were exposed to 48 cm(2) of di-(2-ethyl-hexyl)-phthalate (DEHP)-plasticized PVC in a parallel plate recirculating test cell through which blood was recirculated at 1.5 ml/min. In the first test group, the PVC was untreated; in the second test group, the PVC was washed in methanol to reduce the level of plasticizer on the surface. The test cell was connected to the right femoral circulation, and recirculation was established for a period of 60 min. Blood samples were taken at 0, 30, and 60 min for assessment of CD11b expression on neutrophils using flow cytometric analysis. In a third group of 10 control experiments, rats underwent the entire surgical procedure, but without recirculation through the test cell. There was statistically significant (p < 0.001) lower Cd11b expression on neutrophils in the blood of rats perfused through the cell containing methanol-washed PVC after 30 min and at 60 min. CD11b expression was significantly (p < 0.001) lower in the control group than in both test groups at both the 30 and 60 min time points and at the 60 min time point on comparison with the group where blood was perfused through methanol-washed PVC. These results demonstrate that the biomaterial-contact-mediated upregulation of CD11b may be significantly reduced by employing a methanol-washing technique on the plasticized PVC. Although this technique does not entirely eliminate the expression of CD11b on neutrophils, the difference is significant and suggests the role of the plasticizer in the development of this inappropriate inflammatory response.

Animals↗

PubMed2002

Early experience with a new technique and technology designed for the study of pulsatile cardiopulmonary bypass in the rat.

The benefits of pulsatile flow during the period of cardiopulmonary bypass (CPB) applied during open-heart surgery remains controversial. We have developed a rodent (rat) model of CBP that has been designed to functionally mimic the clinical setting, principally, but not solely, for the study of pulsatile CPB. The successful development of this model centres on the design of the bypass circuitry and the surgical approach employed. The entire circuit is similar to clinical equipment in terms of its construction, configuration, performance, material surface area to blood volume ratio, and priming volume to blood volume ratio. The overall priming volume of the perfusion circuitry is less than 12 ml. Early studies confirm that the pumping technology functions well, gas exchange was adequate at all times, and blood pressure exhibited a normal CPB profile and haemodynanmic response to pulsatile blood flow. We conclude that this is an effective tool for investigating the pathophysiology of pulsatile blood flow during CPB.

Animals↗

PubMed2002

Using the STS and multinational cardiac surgical databases to establish risk-adjusted benchmarks for clinical outcomes.

One of the purposes of collecting data on cardiac surgical procedures, at a national level is to enable individual surgeons to improve quality and benchmark their own practice by making more accurate prospective prediction of outcome of each individual patient by using risk stratification based on previous local and national experiences. The past decade has seen a dramatic increase in the development of national cardiac surgical initiatives in many countries around the world. The size and extent of these databases has successfully allowed their use for patient risk stratification and preoperative risk modeling in four main aspects: patient selection and informed consent, coherent analysis of the determinants of patient outcomes, rationalizing unit management, and negotiations with external agencies. Approximately 610 cardiac surgical units presently contribute their patient data, containing pre-operative risk factors, to centralized national registries. There are currently nine different datasets used throughout the world to collect patient information. To harmonize the considerable diversity among these source materials, an International Dataset has been developed by a collaborative process among more than 50 cardiac surgeons around the world. Constructed around the Society of Thoracic Surgeons (STS) data format, the International Dataset brings in key elements from all the other datasets, allowing the sharing of data and cross-analysis, thus greatly expanding the pool of patients, and national sources, from which risk-stratifed outcomes can now be analyzed and unified. Unlike the STS dataset, the International Dataset incorporates EuroSCORE, a simple-to-use, validated patient risk stratification system, which has been rapidly adopted by large numbers of centers around the world for patient risk stratification, outcomes assessment, and improving patient informed consent. There are several benefits to collecting and centralizing national and international data: (1) understanding and defining basic demographics of patients undergoing cardiac surgery; (2) patient risk stratification and risk prediction at both a national and center-by-center level; (3) unit benchmarking, and development of effective nationally oriented and center-oriented quality improvement programs; (4) understanding and rationalizing resource utilization; and (5) use of data to leverage governments and other healthcare providers to affect policy. Cardiac surgical registries will soon attempt to track patients for longer follow-up periods after discharge in order to identify surgery-related deaths for more extended periods of time following surgery, thereby improving the monitoring and prediction of patient outcomes.

Benchmarking↗