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Biomedical subjects

F L Hanley

Publications and source records attributed to F L Hanley.

156 records · Page 9Linked to original sources
PubMed1989

A randomized clinical trial of 10% pentastarch (low molecular weight hydroxyethyl starch) versus 5% albumin for plasma volume expansion after cardiac operations.

Pentastarch is a hydroxyethyl starch similar to hetastarch, but with a lower average molecular weight (264,000 versus 450,000) and fewer hydroxyethyl groups (molar substitution ratio = 0.45 versus 0.70). These characteristics result in enhanced enzymatic hydrolysis, faster renal elimination (initial intravascular half-life = 2.5 versus 25.5 hours), and less effect on coagulation. We report on a randomized clinical trial comparing the clinical efficacy and safety of 10% pentastarch (group P) for plasma volume expansion after cardiac operations with that of 5% serum albumin (group A). During the first 24 hours after arrival of the patient in the intensive care unit, colloid was infused to maintain a cardiac index of 2.0 L/m2 or more and a mean arterial pressure within 10% of the preinduction value. Group P (n = 50) received 1706 +/- 393 ml of colloid (mean +/- standard deviation) during this period, and group A (n = 44), 1794 +/- 341 ml (p = no significant difference). Hemodynamic responses to infusion were similar for both groups, although in group P a greater increase in both cardiac index (0.5 +/- 0.5 versus 0.3 +/- 0.5 L/min/m2 in group A, p less than 0.01) and left ventricular stroke work index (10.8 +/- 8.0 versus 5.8 +/- 6.0 gm-m/m2, p less than 0.01) was observed during infusion of the first 500 ml. There were no significant differences in any of the measured respiratory parameters (alveolar-arterial oxygen gradient, estimated shunt fraction, and effective pulmonary compliance). Hemodilution with colloid significantly reduced serum protein levels in group P by 24 hours postoperatively (4.0 +/- 0.6 versus 5.0 +/- 0.7 gm/dl in group A, p less than 0.05), although mean serum colloid osmotic pressure was similar (15.4 +/- 2.6 [P] versus 15.5 +/- 2.7 mmHg [A], p = no significant difference). There were no significant between-group differences in prothrombin time, activated partial thromboplastin time, platelet count, bleeding time, or coagulation factors (fibrinogen, V, VII, VIII, or IX) on postoperative days 1 and 7. Perioperative fluid balance, weight change, chest tube output, red blood, platelet, or fresh frozen plasma usage, reexploration for bleeding, and clinical outcome were also similar. These findings indicate that pentastarch is as safe and effective s 5% albumin for plasma volume expansion after cardiac operations with no apparent adverse effects on coagulation. If commercially available at a lower cost than albumin, it would appear to be a reasonable first choice for colloid therapy in this setting.

Aged↗
PubMed1988

The Mustard procedure in infants (less than 100 days of age). Ten-year follow-up.

Surgical treatment of transposition of the great arteries and intact ventricular septum has changed markedly in the past 10 years. However, long-term follow-up on new approaches is not available. In a unique group of patients, operated on in the first 100 days of life with the Mustard procedure, such follow-up is available, and the results of these true infant repairs represent a benchmark against which subsequent techniques applied to infants should be compared. During the period of 1975 to 1980, 36 infants, less than 100 days of age, who had transposition of the great arteries and intact ventricular septum, underwent Mustard repair at the University of California, San Francisco. Ages ranged from 4 to 98 days (mean 46 days) and weights from 2.3 to 6.6 kg (mean 3.5 kg). There were no early deaths, and late follow-up was available from 8 to 13 years (mean 10 years). The late survival rate was 97% (mean 10 years). There was a 62% rhythm disturbance-free survival rate, 89% reoperation-free survival rate, and 91% pacemaker-free survival rate. Echocardiographic evaluation revealed obstruction of the superior vena cava in eight patients, tricuspid insufficiency in four, right ventricular dysfunction in two, and left ventricular outflow tract obstruction in three. The Mustard procedure, performed in the first 100 days of life, results in a high rate of survival (early 100% and late 97%, at a mean of 10 years) and a low incidence of late complications against which other techniques of infant repair should be compared.

Echocardiography↗
PubMed1986

Transmural coronary flow reserve patterns in dogs.

To investigate transmural variations in coronary flow reserve, we studied 20 anesthetized dogs with a Gregg cannula in the left main coronary artery. In 11 dogs, radionuclide-labeled microspheres were injected over a range of perfusion pressures in the control state and during maximal coronary vasodilation produced with chromonar or adenosine. In another nine dogs, control, reactive hyperemic, and adenosine-vasodilated flows were compared at the same perfusion pressures. Adenosine dilated vessels more than did reactive hyperemia, which in turn vasodilated more than did hypoperfusion. Adenosine or chromonar vasodilated more than did hypoperfusion alone in all layers of the heart at perfusion pressures as low as 30 mmHg (P less than 0.05). This effect was greatest in the subepicardium and least in the subendocardium and varied with perfusion pressure (P less than 0.05). Subendocardial-to-subepicardial flow ratios declined with diminishing perfusion pressure despite the fact that flow reserve was present in all layers. We conclude that exhaustion of flow reserve is not the mechanism by which subendocardial ischemia occurs.

Adenosine↗
PubMed1986

Role of adenosine in coronary autoregulation.

The role of cardiac interstitial adenosine as an important metabolite in coronary autoregulation has not been established. We therefore measured steady-state cardiac interstitial adenosine concentration at a high and a low coronary inflow pressure using an epicardial diffusion well in anesthetized dogs. Although coronary resistance for the high and low pressure points showed highly significant differences (P less than 0.001), adenosine averaged 302 +/- 98 and 286 +/- 91 (SD) pmol/ml for the high and low pressure points, respectively (P greater than 0.20). Cardiac interstitial adenosine concentration was then measured with and without an intracoronary infusion of adenosine deaminase catalytic subunit. Adenosine averaged 28 +/- 21 (SD) pmol/ml during the infusion compared with 281 +/- 68 during control conditions (P less than 0.001). Finally, pressure-flow relations were obtained with and without the adenosine deaminase infusion, and there was no loss of autoregulation in the pressure of adenosine deaminase. These findings indicate that intracoronary adenosine deaminase markedly reduces interstitial adenosine concentration, that cardiac interstitial adenosine concentration remains constant during autoregulation, and that the coronary bed autoregulates normally when interstitial adenosine is reduced to levels close to zero. We conclude that cardiac interstitial adenosine concentration is not an important component in coronary autoregulation.

Adenosine↗
PubMed1985

Regulation of transmural myocardial blood flow.

A major problem in understanding how myocardial blood flow is regulated is the common occurrence of subendocardial ischemia in many diseases, with or without coronary arterial disease. Two commonly held explanatory hypotheses were that high systolic intramyocardial pressures prevented flow to deep but not superficial muscle, or that in diastole tissue pressures were highest subendocardially. Neither hypothesis is tenable today, and the likeliest hypothesis is that retrograde systolic flow from the deeper muscle produces a longer time constant for diastolic flow in deep than in superficial muscle.

Biomechanical Phenomena↗
PubMed1985

Effects of pressure gradients between branches of the left coronary artery on the pressure axis intercept and the shape of steady state circumflex pressure-flow relations in dogs.

When steady state pressure-flow relations are studied in the circumflex coronary artery, pressure gradients develop between it and other branches of the left coronary artery. To assess the effects of these pressure gradients, we compared the pressure axis intercept and shape of steady state circumflex pressure-flow relations in the presence and absence of gradients after autoregulation was abolished, both in the beating heart and during long diastoles in dogs. We used peripheral coronary pressures and radionuclide-labeled microspheres to assess arterial collateral flow. In the beating heart, interarterial pressure gradients reduced the curvature at low circumflex pressures, and overestimated the mean pressure axis intercept by 7.8 mm Hg (P less than 0.05). The results were similar for the pressure-flow relations derived during long diastoles. This overestimation exaggerates the difference between the pressure axis intercept and coronary sinus pressure. The peripheral coronary pressure and microsphere results indicate that these effects are mediated largely by arterial collateral flow.

Animals↗
PubMed1984

The effect of coronary inflow pressure on coronary vascular resistance in the isolated dog heart.

The shape of the coronary arterial pressure-flow relationship results from the interaction of a number of poorly understood physiological factors. Experiments in which coronary inflow and outflow pressures were coupled so that driving pressure was held constant showed that changes in inflow or outflow pressures altered coronary blood flow: coronary vascular resistance varied inversely with changes inflow pressure below 50 mm Hg and with changes in outflow pressure below 80 mm Hg. The magnitude of the influence of inflow pressure on resistance also depended on the fixed level of outflow pressure, the influence being large when the outflow pressure was low, and small when it was high. Inflow and outflow pressures, then, are two physiological factors which are determinants of the shape of the pressure-flow relationship, and their interaction contributes to the degree of curvature found in a particular relationship. These findings suggest that the use of linear regression in the interpretation of pressure-flow relationships results in poor estimation of resistance and zero-flow pressure. Other experiments measuring regional coronary blood flow using radionuclide-labeled microspheres resulted in the same inverse relationship between inflow pressure and resistance, regardless of mural depth, indicating that inflow pressure may influence resistance by distending vessels, rather than by causing sequential cessation of perfusion in successive transmural layers.

Animals↗
PubMed1984

Arterial and venous coronary pressure-flow relations in anesthetized dogs. Evidence for a vascular waterfall in epicardial coronary veins.

The coronary circulation of anesthetized dogs was tested for the presence of vascular waterfalls by manipulating coronary arterial and coronary venous pressures. The left main coronary artery and the coronary sinus were cannulated, and relationships between coronary artery pressure, coronary sinus pressure, and coronary flow were studied. Experiments were conducted during diastolic arrests, under steady state conditions, in the absence of autoregulation. Relations of coronary flow to coronary sinus pressure at constant coronary artery pressure were consistent with the presence of a vascular waterfall in the coronary sinus. When the great cardiac vein was cannulated, relations of great vein flow to great vein pressure at constant coronary artery pressure were consistent with the presence of a vascular waterfall in the great vein, indicating that waterfall behavior can occur in epicardial veins other than the coronary sinus. In dogs on right heart bypass, with the coronary sinus and great vein uncannulated, the relationship between right atrial pressure and coronary sinus pressure showed a waterfall pattern, indicating that the waterfall is not an artifact of venous cannulation. In the right heart bypass experiments, venous waterfall behavior was seen in beating hearts as well as during diastolic arrests. We conclude that a vascular waterfall is present in epicardial coronary veins which can significantly influence coronary blood flow.

Animals↗
PubMed1984

The effects of cardiopulmonary bypass on coronary blood flow in the dog.

The effects of cardiopulmonary bypass on autoregulation, maximum coronary flow, and regional blood flow in the heart were investigated in 25 dogs. A Gregg cannula was inserted into the left main coronary artery, and pressure-flow relations were then measured in the autoregulating state or with vasodilation produced by intracoronary adenosine infusion before, during, and after cardiopulmonary bypass. Seventeen of the dogs had radioactive microspheres injected to investigate regional blood flow changes at the same times. (1) Autoregulation was not present after bypass for at least 3 hours. (2) Blood flow was shifted toward the subendocardium on bypass (increased subendocardial/subepicardial ratio) and tended to return to prebypass distribution following bypass. (3) Blood flow after bypass was not significantly different to the subendocardium and subepicardium. (4) Response to a coronary vasodilator (maximum coronary flow) was significantly affected by cardiopulmonary bypass: blood flow to all layers of the heart could be increased with adenosine after bypass. (5) Global lactate and oxygen metabolism were not adversely affected by bypass. We conclude that cardiopulmonary bypass abolished the normal autoregulation of coronary flow; this may predispose the incompletely revascularized patient to a "coronary steal" syndrome. However, the heart with normal coronary arteries is not underperfused in any layer after bypass. Thus, the bypass technique is not the cause of the subendocardial ischemia that sometimes complicates cardiac operations.

Adenosine↗
PubMedDate not supplied

Measurement of collateral blood flow in a porcine model of aortic coarctation by velocity-encoded cine MRI.

The purpose of this study was to investigate the time course of development of collateral blood flow in an animal model of aortic coarctation. A juxtaductal aortic stenosis (model coarctation) was surgically created in five juvenile pigs. MRI was performed preoperatively, 1 to 2 days postoperatively, and 2 to 10 weeks postoperatively. Aortic blood flow was measured by velocity-encoded cine MR (VENC-MR). The percent change in aortic blood flow (delta BF) from proximal to distal descending thoracic aorta was calculated, and a multiple-comparison paired t test used to assess changes in delta BF over time. Invasive flow measurements were obtained in one animal before sacrifice using an ultrasonic probe. delta BF preoperatively was -2 +/- 8% (mean +/- SE). delta BF increased to 32 +/- 7% (mean +/- SE, P = .022) 2 days postoperatively and 55 +/- 19% (P = .032) 2 to 8 weeks postoperatively. Invasive measurements were in qualitative agreement with the VENC-MR data. VENC-MR is an accurate noninvasive method of measuring collateral blood flow in aortic coarctation. Recruitment and development of collateral flow pathways occur rapidly in an animal model.

Animals↗
PubMedDate not supplied

Tetralogy of Fallot with major aortopulmonary collaterals: early total repair.

Tetralogy of Fallot with pulmonary atresia and major aortopulmonary collaterals is a complex lesion distinguished by marked heterogeneity of pulmonary blood supply. Over the past two decades, investigators have developed various approaches to the management of this anomaly generally based on the concept of staged unifocalization of pulmonary blood supply. Although such approaches may represent an improvement on the natural history of this lesion, they remain inadequate for a substantial portion of patients born with tetralogy of Fallot and major aortopulmonary collaterals. Since 1992, our approach has been to perform one-stage complete unifocalization through a midline approach in all but a few extremely complicated patients. We aim to repair these patients early in infancy, with an emphasis on native tissue-tissue reconstruction, in order to optimize prospects for survival with a good functional outcome in as many patients as possible. In this review, we present our philosophy and our experience with unifocalization and repair in 72 patients.

Adolescent↗