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Biomedical subjects

H Korb

Publications and source records attributed to H Korb.

At least 37 records · Page 2Linked to original sources
PubMed1991

Priming of cardiopulmonary bypass with human albumin or Ringer lactate: effect on colloid osmotic pressure and extravascular lung water.

We have undertaken a randomized study on 20 patients undergoing coronary artery bypass surgery in order to determine the influence of cardiopulmonary pump prime solutions on colloid osmotic pressure and extravascular lung water. Crystalloid priming with Ringer lactate was compared with an albumin solution of nearly physiological colloid osmotic composition (4%). Measurements of extravascular lung water were performed by a modified, highly sensitive thermal dye technique, with additional detection of tracer signals in the pulmonary artery. In the Ringer lactate group, a significantly greater decrease in colloid osmotic pressure occurred immediately after onset of cardiopulmonary bypass. The more pronounced decrease in colloid osmotic pressure and in transcapillary gradient (difference between colloid osmotic pressure and pulmonary capillary wedge pressure) in the Ringer lactate group was associated with a significant increase in extravascular lung water (by 60%) in the postoperative period; the human albumin group, however, showed only a slight tendency to increased lung water. There were no differences in haemodynamic or respiratory states after operation.

Albumins↗
PubMed1991

[The energetics and economics of the cardiac pump function].

In anesthesiology and intensive care medicine it is often necessary to treat disorders involving cardiac failure or low-output syndrome. However, in patients who are endangered by ischemic heart disease, any pharmacologic therapy with positive inotropic agents should improve cardiac output without increasing myocardial oxygen demand significantly: the heart should perform its task as efficiently as possible. In the present study a mathematical model of myocardial efficiency was developed. The implications of this theoretical concept of myocardial efficiency were evaluated in animal experiments. THEORETICAL MODEL. Cardiac efficiency is predominantly dependent on preload, afterload, and inotropic state. Quantitatively, it can be calculated from end-diastolic volume, left ventricular systolic pressure (Psyst), stroke volume (SV), and ejection time. The implications of the theoretical analysis are: (1) the inotropic state, which leads to optimal myocardial efficiency, is specifically determined by preload and afterload: for each preload and afterload one matched inotropic state is necessary to achieve optimal efficiency; (2) an increase in blood pressure leads to a decrease in myocardial efficiency even if the inotropic state is optimally matched to preload and afterload; and (3) an increase in end-diastolic volume improves the efficiency of myocardial pump work. ANIMAL EXPERIMENTS. The validity of the theoretical model was studied in animal experiments with emphasis on the following items: (1) is theoretically optimal efficiency of myocardial pump work achieved by physiologic regulation of myocardial performance? (2) how does sympathetic stimulation influence myocardial efficiency? and (3) how do cardiodepressive agents such as beta-blockers or volatile anesthetics influence myocardial efficiency? METHODS. Experiments were performed on nine mongrel dogs after induction of piritramide--nitrous oxide anesthesia. Standard hemodynamics: heart rate, Psyst, maximum left ventricular pressure rise (dP/dtmax), and SV (thermodilution) as well as coronary blood flow (pressure difference catheter) and myocardial oxygen consumption (Fick principle) were measured. In order to create a broad range of different hemodynamic settings, blood withdrawal and retransfusion of blood and/or colloid osmotic solutions were used to modify intravascular volume. Additionally, the inotropic state was varied by infusion of catecholamines (isoproterenol 0.4-0.8 microgram.kg-1.min-1 or norepinephrine 1-2 micrograms.kg-1.min-1). Experimental myocardial failure was induced by adding halothane (0.8-1.5 MAC) to the basic anesthesia, beta-blockade with propranolol (125-250 micrograms.kg-1), and combination of beta-blockade with a pressure load imposed on the myocardium (propranolol 125-250 micrograms.kg-1 + norepinephrine 1-2 micrograms.kg-1.min-1). RESULTS. During variation of the intravascular blood volume by normo-, hypo-, and hypervolemia, the myocardial efficiency very closely matched the theoretically predicted values of optimal efficiency: the average observed efficiency was 98.8% of predicted optimal efficiency. Increasing afterload with norepinephrine did not alter this close relationship, although absolute values of efficiency decreased as predicted by the theoretical model. Application of isoproterenol resulted in SVs that exceeded optimal values by 41.5%. In contrast, during experimental myocardial failure SVs were too small to achieve the necessary values for optimal pump work; observed myocardial efficiency was therefore significantly lower than optimal efficiency. CONCLUSIONS. For pharmacological interventions, it can be concluded that maximal efficiency of cardiac pump work requires maximal end-diastolic filling in combination with minimal afterload. (ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia, Inhalation↗
PubMed1990

In vitro fertilization and cleavage of bovine oocytes matured in medium supplemented with estrous cow serum.

Bovine follicular oocytes were matured in TCM 199 supplemented with: (1) fetal calf serum (FCS, 20% v/v), Luteinizing Hormone (LH, 10 ug/ml), and Estradiol-17-beta (E(2), 1 ug/ml) in Experiment 1; (2) 20% cow serum recovered at standing estrus (Experiment 2); or (3) 20% FCS (Experiment 3). Maturation, fertilization, and initial cleavage development were evaluated at 16 and 48 h after in vitro insemination. The proportions of oocytes fertilized after maturation in the presence of added hormones (78.5%, Experiment 1) or estrous serum (71.3%, Experiment 2) were significantly higher (p < 0.01) than after use of FCS alone (39.3%, Experiment 3). Cleavage of zygotes within 48 h post-insemination differed significantly (p < 0.01) between maturation treatments, 27.3%, 75.5% and 6.6% for Experiments 1, 2, and 3, respectively. Results demonstrate a beneficial influence of estrous cow serum, characterized by an elevated concentration of LH, on bovine oocyte maturation in vitro.

Journal Article↗
PubMed1990

Heterogeneity of myocardial blood flow under normal conditions and its dependence on arterial PO2.

We studied the heterogeneity of myocardial blood flow in nine anesthetized closed-chest dogs using an indicator-dilution technique that allows the stochastic description of transport characteristics for three inert gases (helium, argon, and xenon) from the coronary inflow to outflow. The results show that under normal conditions the transcoronary transport of the tracers is spatially heterogeneous. Heterogeneity is strongly dependent on the arterial oxygen tension over a range of 40-200 Torr. This could be similarly observed with each tracer gas despite different physicochemical properties and was largely independent from the magnitude of coronary blood flow. The results are interpreted to mean that the arteriolar or intratissue PO2 influences myocardial blood flow over a broad range and possibly acts as an important integrating factor in the local regulation of coronary blood flow and flow reserve.

Animals↗
PubMed1990

Transport of inert gases in mammalian myocardium: comparison with a convection-diffusion model.

Because tracer techniques are gaining an increasing importance for imaging flow (and metabolism) in the heart, experimental evidence is needed on the role of convection and diffusion in the transcoronary transport of solutes. In the present work, the transport of four different inert gases through the coronary system is studied in five closed-chest dog experiments and is compared with a digital multicapillary convection-diffusion model. Transport may be defined as flow dependent, as judged by the gross similarity of shape of the time-normalized dilution curves. However, the results show that the transcoronary transport of helium and xenon is more dispersed than that of argon and krypton, probably because of differences in diffusibility and solubility. A comparison of the animal and model experiments emphasizes the importance of diffusive transport of the gases. It is suggested that there is a diffusion shunt that is mainly located within the capillary network itself rather than between conduit vessels. Only for helium (which has the highest diffusivity) was a small arteriovenous shunt fraction seen that is thought to bypass the capillary exchange region. The conclusion is that although there is evidence of diffusional shunting at a capillary level, the inert gas kinetics in the heart are compatible with a basically flow-limited transport.

Animals↗
PubMed1989

Characteristics of the pulmonary transport functions for heat and dye in pulmonary edema and orthostasis.

The aim of this study was to investigate whether changes in the distribution of pulmonary blood flow and disturbances of the pulmonary microcirculation can be detected by use of inflow-outflow indicator-dilution measurements. In 18 anesthetized (N2O-piritramide) mongrel dogs 221 thermal-indocyanine green dye indicator dilution kinetics were recorded in the pulmonary artery and aorta after central venous indicator injection. The lagged normal density function was used as a model for the pulmonary transport functions for heat and dye. The parameters of the lagged normal density function were computed by a non-linear least squares procedure by iterative convolution. After baseline measurements, in nine dogs, pulmonary edema was induced by central venous application of oleic acid. In nine other dogs, measurements were performed before and after postural changes. Our data show that both the microvascular injury caused by oleic acid edema and the perfusion heterogeneity caused by orthostasis can be detected by the indicator dilution technique since the both relative dispersion and skewness of the transport functions for heat and dye were significantly increased after these interventions.

Animals↗
PubMed1989

[Use of the autoperfusion catheter in acute coronary occlusion within the scope of percutaneous transluminal coronary angioplasty (PTCA)].

The procedure of an autoperfusion catheterization after acute coronary occlusion by dissection during percutaneous transluminal coronary angioplasty (PTCA) is described. Multiple side holes proximal and distal to the dissection allow passive myocardial perfusion only by systemic blood pressure. In the case presented, the catheter immediately reestablished coronary blood flow and thereby produced resolution of symptoms and myocardial ischemia. This easy procedure made it possible to perform the subsequent coronary bypass operation as a controlled revascularization and it prevented myocardial necrosis.

Angioplasty, Balloon↗
PubMed1988

Interference with the prostaglandin system as a therapeutical concept to protect the myocardium during ischemic stress: experimental studies with inhibition of thromboxane synthesis.

The characterization of thromboxane A2 as vasoconstrictor and potent stimulus of platelet aggregation has led to attempts to overcome these effects obviously unfavourable in ischemia. As an attractive approach, we examined potentially protective results of thromboxane synthetase inhibition on canine myocardium stressed by transient ischemia, using as inhibitor the imidazole derivative UK 38.485. On anaesthetized open-chest mongrel-dogs (n = 5) repeated ischemia (3 min) was produced by proximal, intermittent occlusion of the LAD artery. In each experiment 3-4 control occlusions were compared to 3-4 occlusions under therapy. The efficiency of the drug (5 mg/kg body weight, i.v., 30 min before therapy occlusion) was examined (a) by quantification of the energy deficit occurring as the difference between oxygen demand and uptake during occlusion, (b) by the amounts of potassium, inorganic phosphate, and lactate released in the postischemic reperfusion and (c) by changes of the regional myocardial wall function in the central- and peripheral ischemic zone. Compared to control, premedication with UK 38.485 led to a reduced energy deficit (-39.1%; p less than 0.01) combined with a significant decrease in the release of potassium (-15.7%; p less than 0.001), inorganic phosphate (-20.2%; p less than 0.002), and lactate (-20.7%; p less than 0.01). Regional myocardial wall function was improved in the central and peripheral ischemic region as demonstrated by a significantly reduced systolic bulging. The protective effects seem to be mainly due to enhanced flow to ischemic areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Asymptomatic myocardial abscess.

This report describes a rare case of an asymptomatic myocardial abscess which was not associated with infective endocarditis but was diagnosed to be a tumor and treated by open-heart surgery. A 69-year-old patient without a history of endocarditis or myocardial infarction was submitted to invasive cardiac diagnostics after an embolic event in the brachial artery. Investigation revealed an "intracardiac tumor" and the patient subsequently underwent open-heart surgery. After cardiotomy the suggested tumor was found in the posterior wall of the left atrium adjacent to the mitral ring, appearing as a circumscribed, indurated, and plane area. After incision for biopsy, a cheesy pus emptied from a cavity. The tissue sections showed an intramural myocardial abscess. Because of the extent, location and the character of the abscess, the cavity was closed after rinsing using mattress sutures. The postoperative course was uncomplicated. This report demonstrates that in suspected cardiac tumors a myocardial abscess should be considered in any differential diagnosis despite the rarity of the event, since the diagnosis of the myocardial abscess is not an absolute indication for surgical intervention.

Abscess↗
PubMed1988

No pulmonary edema or congestion after central venous injection of conventional and newer contrast media in dogs.

Our aim was to determine whether large central venous doses of ionic diatrizoate, nonionic iopromide, or nonionic iotrolane produce pulmonary edema or pulmonary congestion in dogs. Eighteen dogs (six per group) anesthetized with piritramide and N2O received three sequential doses (1.5 mL/kg body weight) of one contrast medium in less than 20 seconds. Before the first injection, and again 1, 5, 10, 20, and 30 minutes after each contrast injection, extravascular lung water, pulmonary blood volume, and cardiac output were determined by thermal-dye dilution. Neither extravascular lung water nor pulmonary blood volume increased after any contrast medium. Pulmonary blood volume and cardiac output decreased slightly but not significantly after all contrast media during the course of the study. We conclude that diatrizoate, iopromide, or iotrolane do not produce pulmonary edema or congestion in dogs.

Animals↗
PubMed1988

Thermal recovery after passage of the pulmonary circulation assessed by deconvolution.

For indicator-dilution studies, complete thermal recovery after passage of heat through the pulmonary circulation would be desirable. However, the results in the literature obtained by extrapolation techniques are inconsistent. To overcome problems of the extrapolation approach, transport functions of the pulmonary circulation (including the left heart) were computed by deconvolution of pulmonary arterial and aortic pairs of thermodilution curves after central venous indicator injection (10 ml of an ice-cold blood indocyanine green dye mixture). Thermal recovery was determined as the finite integral of the transport function. Thirteen mongrel dogs under piritramid-N2O anesthesia were examined under base-line conditions, in orthostasis to alter the distribution of pulmonary blood flow (9 dogs), and in oleic acid edema (8 dogs). Using the deconvolution approach, thermal recovery was 0.97 +/- 0.04 under base-line conditions, 0.96 +/- 0.03 in orthostasis, and 0.96 +/- 0.05 in pulmonary edema. Thermal recovery determined from extrapolated dilution curves was greater than 100% in all groups, a physically impossible finding. It is concluded that thermal recovery is incomplete but insensitive with respect to the distribution of blood flow and to the size of the extravascular compartment. Monoexponential extrapolation is unsuited for the determination of thermal recovery.

Animals↗
PubMed1988

Evaluation of monoexponential extrapolation of transpulmonary thermal-dye kinetics by use of a new model-free deconvolution algorithm.

This study evaluates the routine mathematic approach (monoexponential extrapolation) for analysis of transpulmonary thermal-dye dilution curves and estimates the effects of systemic-indicator recirculation by use of a deconvolution technique. Fifteen dogs anesthetized with N2O-piritramid were studied before and after induction of pulmonary edema by oleic acid. After introduction of central venous indicator (10 ml of a mixture of cold blood and indocyanine green dye), dilution data were recorded from the pulmonary artery and the ascending aorta. The conclusions were: (1) monoexponential extrapolation yields reasonably good estimates of the mean transit times of dye; (2) mean transit times of heat are usually overestimated by monoexponential extrapolation; (3) extravascular lung thermal volume assessed by monoexponential extrapolation is overestimated by 2.03 ml/kg of body mass under baseline conditions; and (4) the prepulmonary volume of distribution of heat exceeds that of dye by 1.4 ml/kg of body mass, thus increasing the overestimation of pulmonary extravascular heat-accessible space by the conventional technique.

Algorithms↗
PubMed1987

Determination of central blood volume and extravascular lung water.

UNLABELLED: In patients undergoing thoracic surgery central blood volume is subject to large variations and extravascular lung water may change critically due to fluid shifts. Therefore, an accurate monitoring of these parameters, in particular under perioperative conditions, seems to be desirable. This study describes an improved method for the measurement of intrathoracic volumes. Experiments were carried our in 9 mongrel dogs under piritramide-N2O anesthesia. In order to produce low cardiac output in combination with uneven distribution of perfusion, measurements were performed under base line conditions and after postural changes. Indicators (cold and indocyanine green dye) were injected into the v. cava and indicator kinetics were recorded from the pulmonary artery and aorta using thermistor-fiberoptic catheters. The transport functions of cold and dye were computed from the corresponding pairs of dilution curves. From the transport functions, the mean transit times of the intravascular (dye) and diffusible (cold) indicator were determined. Central blood volume and extravascular lung thermal volume were calculated from the mean transit times and a thermodilution cardiac output. RESULTS: Under base line conditions, central blood volume was 15.3 +/- 2.5 ml/kg body weight. In orthostasis, a significant and reversible reduction to 11.6 +/- 2.4 ml/kg body weight was found. Cardiac output fell significantly from 3.3 +/- 0.5 to 2.4 +/- 1.1. l/min. In contrast, the slight decrease of extravascular lung thermal volume was not statistically significant. It is concluded that the method presented is sensitive enough to detect even small changes of central blood volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

[Measuring coronary circulation using an inert gas method--a comparison of common indicator gases].

Validation studies of inert gas techniques are limited in number and usually have not included circumstances with marked heterogeneity of flow. This study was intended to investigate the validity of the method in experimental animals under various hemodynamic conditions by parallel application of helium, argon, krypton and xenon as indicators and by comparison with direct flow measurements. Gases were applied by single breath inhalation. In order to avoid the limitations of conventional methods arising from the systemic recirculation of tracer and from shortened measuring periods we used continuous mass spectrometric recording and numeric deconvolution of the dilution curves in arterial and coronary venous blood. When the transit times are evaluated by "stochastic" analysis and commonly used tissue/blood partition-coefficients (lambda He = 0.95, lambda Ar = 1.1) the helium and argon values are found in reasonable agreement with reference flows. The effects of a shortening of measurements that are based on single integrated samples (Argon method) are shown under control conditions, adenosin infusion and elevated ventricular filling pressure. With xenon (lambda Xe = 0.7) coronary blood flow above 100 ml/min X 100 g is underestimated by the "stochastic" and by the "initial slope technique"; parallel measurements with argon suggest that in the initial slope technique a lambda Xe between 0.8 and 0.9 might be more adequate.

Animals↗
PubMed1986

Preservation of myocardium in transient ischemia by the thromboxane synthetase inhibitor UK 38.485.

This study was performed to examine potential protective effects of UK 38.485, an inhibitor of thromboxane synthetase, in canine myocardium stressed by transient ischemia. On anesthetized open-chest mongrel-dogs (n = 9) repeated ischemia (3 min) was produced by proximal, intermittent occlusion of the left anterior descending artery. A total of 18 occlusions after 3 mg UK 38.485/kg body wt. and 12 occlusions after 5 mg UK 38.485/kg body wt. were compared to a total of 24 occlusions under control conditions. In each experiment, 2-3 control occlusions and 3-4 therapy occlusions were performed. The drug was applied i.v. in a dose of 3 or 5 mg/body wt. 30 min before the first therapy occlusion. In both groups, hemodynamics and energetics did not significantly change as compared to control. The efficiency of the drug in protecting ischemically stressed myocardium was examined by (a) quantification of oxygen debt and oxygen repayment in the occlusion and reperfusion periods and (b) the amounts of inorganic phosphate, lactate, and potassium released in the first minute of reperfusion. Compared to control occlusions, premedication with either 3 or 5 mg UK 38.485 led to a significantly reduced oxygen debt combined with a significant decrease of the release of inorganic phosphate, lactate, and potassium. The protective effect is suggested to be mainly due to enhanced flow to ischemic areas. Data obtained in this study suggest protective effects of the compound in the preservation of myocardium in transient ischemia and attest to the concept that thromboxane A2 may aggravate the metabolic and energetic situation of myocardium in circumstances with reduced oxygen supply.

Animals↗