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Biomedical subjects

H Swan

Publications and source records attributed to H Swan.

At least 37 records · Page 2Linked to original sources
PubMed1995

Linkage of the long QT syndrome to the short arm of chromosome 11: use of five highly polymorphic markers towards more detailed localization of the mutant gene.

The long QT syndrome is an autosomally dominantly inherited cardiac disorder characterized by abnormalities of myocardial repolarization, exercise- or stress-related syncopal attacks and risk of sudden death due to cardiac arrhythmias. Genetic linkage studies have defined three LQT loci on chromosomes 11p15.5, 3q21-24 and 7p35-36. We performed linkage analyses in three Finnish LQT families using five amplifiable markers assigned to chromosome 11p15. By multipoint linkage analyses we obtained a maximal lod score of 5.503, suggesting that the LQT1 locus maps between D11S922 and D11S1338 on chromosome 11. Our data provide a step towards closer definition of the exact borderlines of the LQT1 locus in chromosome 11 and demonstrate markers with high utility in identification of gene carriers in the affected families.

Adolescent↗
PubMed1994

Aminosulfonic acid buffer preserves myocardium during prolonged ischemia.

Prevention of myocardial acidosis during global ischemia in operative cardiopreservation was explored in two series of dogs where acid-base control was the only variable. A specifically designed aminosulfonic acid buffer composition, 3:1 molar equivalents NaMOPS to HEPES, 0.2 mol/L, was compared with NaHCO3 (pH 8). Dissolved in standard cardioplegic solution it was given every 30 minutes by coronary infusion at 20 degrees C during 3 hours of global ischemia. Glass electrode intramyocardial pH, adenosine triphosphate (ATP) level, left ventricular contractility (Dp/Dt) and compliance (-Dp/Dt), and other cardiovascular parameters were measured frequently throughout ischemia and for 75 minutes thereafter. In the buffer group (n = 6) myocardial pH remained above entry levels throughout the study period, adenosine triphosphate level remained normal during ischemia, and Dp/Dt and -Dp/Dt at 75 minutes of reperfusion were above entry levels. In the NaHCO3 group (n = 6) pH declined and remained depressed throughout ischemia, adenosine triphosphate level fell steadily and significantly throughout the experiment, and Dp/Dt and -Dp/Dt never regained entry levels. The difference in each parameter between the two groups was statistically significant (p < 0.05). We conclude that control of myocardial acid-base equilibrium alone during global ischemia will preserve myocardial function and minimize reperfusion injury.

Acidosis↗
PubMed1991

Ultrasonic beam-plotting with very small spheres.

A method of pulse-echo ultrasonic beam plotting is described. It differs from traditional pulse-echo beam plotting in that the ultrasonic pulses are scattered off a totally isolated sphere rather than a sphere suspended on a wire. The method also allows extremely small spheres to be used thus providing greater resolution. It is demonstrated that pulse-echo beam plotting using spheres of different size produces different iso-echo amplitude curves.

Transducers↗
PubMed1990

Quality control of perfusion: monitoring venous blood oxygen tension to prevent hypoxic acidosis.

The long-held belief that venous oxygen tension mirrored tissue oxygen tension became suspect in the 1960s when new instrumentation consistently showed that tissue oxygen tension was 10 to 30 torr less than venous oxygen tension. Moreover, a countercurrent of oxygen exchange between terminal arteries and veins was shown to exist. Despite this conflict in scientific theory, however, monitoring venous oxygen tension as a means to control hypothermic cardiopulmonary bypass has been repeatedly urged, since myocardial acidosis is clearly extremely detrimental. This study of the relationship between venous oxygen tension during hypothermic bypass and a concurrent increment in lactacidemia yields strong objective evidence to support the use of on-line venous oxygen tension monitoring to guide perfusion. In a random series of 36 patients, venous blood samples were drawn at five preselected intervals during operation and were analyzed for pH, carbon dioxide tension, oxygen tension, lactic acid, hematocrit, and base excess. Analysis of the data revealed that venous pH and base excess showed no correlation to venous oxygen tension. However, lactic acid showed a strong correlation with venous oxygen tension, with a correlation coefficient of 0.4338 at a confidence level of p less than 0.0001. If the patients were divided into three clinically pertinent groups based on the lowest venous oxygen tension recorded, a strong relationship between venous oxygen tension and lactic acid emerged. If the lowest measurement of venous oxygen tension was greater than 35 mm Hg (group A), the mean rise in lactic acid was only 0.12 microns/ml. If the lowest measurement was between 30 and 34 mm Hg (group B), the mean rise was 0.64 microns/ml. Whereas, if any venous oxygen tension value fell below 30 mm Hg (group C), the mean rise in lactic acid was 2.56 microns/ml. Analysis of variance showed that group C values were significantly different from groups A and B values (p less than 0.0002). A scientific hypothesis relating venous oxygen tension to adequate tissue oxygenation is proposed. Use of venous oxygen tension monitoring with the goal to maintain the level above 35 mm Hg is strongly supported by this study.

Acidosis, Lactic↗
PubMed1988

Maxillary fibrosarcoma with extracellular immuno-characterization.

Maxillary fibrosarcoma of a 31-year-old female is described with special reference to immunofluorescent characterization of the extracellular matrix. Following extractions, endodontic treatment and occlusal adjustment the tumour was operated on. The spindle-shaped tumour cells displayed a herring-bone pattern. The tumour was diagnosed as a fibrosarcoma and graded as poorly differentiated. Immunostaining for the specific type I collagen was positive throughout the tumour matrix, whereas staining for type III collagen was faint and occasional, and did not definitely codistribute with reticulin. Staining for type IV collagen and fibronectin in the tumour matrix was negative.

Adult↗
PubMed1984

The importance of acid-base management for cardiac and cerebral preservation during open heart operations.

The basic physiologic characteristics of acid-base equilibria during hypothermia were briefly reviewed. By graphic analysis, four possible clinical strategies for managing the acid-base status of the patient undergoing H-CPB were documented. The effect of hemodilution on buffer capacity was charted in a manner applicable to common current operative procedures. During hypothermia for cardiac operations as presently conducted, the perfusionist is in control of the temperature of the body and the perfusion preservation of the body and brain; the surgeon must assume responsibility for preservation of the heart. The literature pertinent to the relationship of the acid-base state to the functions and structural preservation of the heart and brain during the conditions of cooling to and rewarming from deep hypothermia associated with cardiopulmonary bypass, aortic cross clamping, cardioplegia and total circulatory arrest have been reviewed. The evidence is overwhelming that myocardial anoxia caused by aortic occlusion or total circulatory arrest at any temperature to 15 degrees C. result in progressive acidosis which, of itself, is myotoxic. In contrast, alkalinity is ionotropic. Myocardial ischemia, in both adults and infants, should be prevented and treated by alkaline perfusion cooling and by frequent coronary perfusion of a cardiopreservative solution which is extremely cold (4 to 8 degrees C.), oxygenated, has a pH of 7.8, slightly hyperosmolar and which has a hematocrit of 20 per cent (imidazole, erythrocytes and plasma protein colloid), a cardioplegic ionic pattern and energy substrates. Reperfusion of the heart should begin at a 37 pH of 7.8. Evidence is strong that the use of CO2 added to any gas mixture is harmful. It increases myocardial acidosis; it does not increase cerebral blood flow during hypothermia. Protection of the unperfused brain of an infant should emphasize prevention of circulatory arrest prolonged to more than 40 minutes. Temporary reperfusion at that time limit should be used. Probably the best general management of the body for H-CPB is alpha-stat, which preserves biologic neutrality. The uncorrected analyzer reads pH 7.4 and Pco2 at any temperature. However, the need for preservation of the hypoxic heart is overwhelming and, thus, the best acid-base management for cardiac hypothermic operations is significant respiratory alkalosis. The most appropriate sites for the collection of blood samples for gas analysis and measuring temperatures were discussed; "body temperature" is the most unreliable parameter measured. The major characteristics of an "ideal" cardiopreservative solution were described.(ABSTRACT TRUNCATED AT 400 WORDS)

Acid-Base Equilibrium↗