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B Zwissler

Publications and source records attributed to B Zwissler.

69 records · Page 4Linked to original sources
PubMed1993

PGI2 aerosol versus nitric oxide for selective pulmonary vasodilation in hypoxic pulmonary vasoconstriction.

Intravenous prostacyclin (PGI2) is a potent pulmonary vasodilator in pulmonary hypertension. However, dose-dependent systemic vasodilation, an increase in intrapulmonary shunt and hypoxemia limit its clinical application. Recently, inhaled nitric oxide (NO) has been reported to elicit selective pulmonary vasodilation, but its clinical use is restricted by its potential toxicity; furthermore, the feasibility of NO application in clinical practice seems difficult. Therefore, we investigated the effects of PGI2 aerosol on pulmonary and systemic circulation and compared the hemodynamic effects to those of inhaled NO. In 6 dogs, ventilation with a hypoxic gas mixture (FiO2 0.09-0.11) increased pulmonary vascular resistance (PVR) by 196% (HPV). Aerosolization of a PGI2 solution at a concentration of 430 ng/ml reduced hypoxia-induced increase of pulmonary artery pressure by 48% and PVR by 52% within 6-10 min without systemic vasodilation. The administered dose of PGI2 was 0.87 +/- 0.26 ng/kg/min. In 2 dogs, doubling the PGI2 concentration (860 ng/ml) did not enhance the vasodilatory effect. After termination of PGI2 inhalation, HPV was restored within 10-15 min. Inhaled NO (50 ppm) decreased the HPV-induced increase in PAP by 76% and in PVR by 73% within 5-10 min. Clinically relevant systemic vasodilation was not observed. It is concluded that inhalation of aerosolized PGI2 leads to selective pulmonary vasodilation in hypoxia-induced pulmonary hypertension. Aerosolized PGI2 at a concentration of 430 ng/ml was less potent than NO (50 ppm). However, due to the lack of known toxicity and its uncomplicated mode of application, inhaled PGI2 may be one alternative to inhaled NO in the treatment of acute pulmonary hypertension.

Administration, Inhalation↗
PubMed1993

Heterogeneity of left ventricular perfusion during pulmonary edema and microembolism treated with positive end-expiratory pressure and norepinephrine.

Regional left ventricular myocardial blood flow was studied in an experimental model of pulmonary edema and microembolization (PEM) ventilated with positive end-expiratory pressure (PEEP). The analysis was based on a 3-dimensional extension of the autocorrelation function used to assess the spatial correlation (rspat) of myocardial perfusion. Experiments were performed on 8 premedicated, anesthetized and mechanically ventilated dogs. PEM was induced with oleic acid (0.01 mg/kg) and glass beads. Successive PEEP values of 10, 15 and 20 cm H2O (P20) were applied and norepinephrine (NE, 0.2-1.0 microgram min-1 kg-1) was administered after P20. Regional perfusion was measured with radioactive microspheres. The left ventricle (LV) was dissected into 256 samples. rspat was computed as the correlation of regional perfusions of samples p units apart in the apex-to-base, endo-epicardial and angular directions. Analysis was performed after anesthesia and instrumentation (control, C), P20 and NE. Control values of rspat were around 50% in the apex-to-base and angular directions and the sign was inverted in the endo-epicardial direction. A reduction of rspat to values close to zero was observed in all directions for P20 and NE. This is the typical pattern of independent distribution. Thus, the results indicate that, under the experimental conditions used, there is some degree of neighborhood dependence of regional LV myocardial blood flow. This dependence is not observed under PEM, mechanical ventilation with PEEP and NE.

Animals↗
PubMed1993

[Monitoring the right ventricle: methods and relevance].

For long, the right ventricle (RV) has been looked upon as a passive conduit of blood, which does not contribute to overall myocardial performance. While this is true under physiological conditions, it has been recognized only recently that an intact RV may be of crucial importance for the maintenance of cardiocirculatory stability under pathophysiological circumstances, e.g. in patients with increased pulmonary vascular resistance (PVR). Hence, several techniques have been developed to monitor RV function in these patients. With respect to the monitoring of RV preload, the validity of parameters based on pressure measurement (e.g. central venous pressure, RV end-diastolic pressure) is limited by the nonlinearity of the RV pressure-volume relationship, changes of RV compliance (e.g. ischemia, drugs), and changes of intrathoracic pressure. The measurement of RV end-diastolic volume (RVEDV) or size provides a more accurate estimation of true RV fiber preload and is currently performed using the fast-response thermodilution technique. The exact quantitation of RV afterload requires the continuous assessment of RV pressure, geometry and wall thickness, which is not possible in the clinical setting. Mean pulmonary artery pressure (PAP and PVR may roughly reflect actual RV afterload under physiological conditions. However, neither PAP nor PVR take into account changes of afterload due to changes of RV size. With respect to RV contractility, none of the techniques presently available for its measurement is both valid and suitable as a tool for clinical monitoring.

Hemodynamics↗
PubMed1991

Methodological error and spatial variability of organ blood flow measurements using radiolabeled microspheres.

The quantitative analysis of the spatial variability of organ blood flow by means of radiolabeled microspheres (MS) requires that the methodological variability ("error") of the technique (RDmeth.) is known in each individual organ. Therefore, RDmeth. was quantified (eight to nine nuclides) in 6941 tissue samples from 13 organs of three anesthetized dogs, and the relative importance of errors originating from both the stochastic nature of MS distribution (RDtheo.) and the process of quantitation of MS radioactivity (RDcounting) was assessed under varying conditions (high/low specific MS activity (SAMS); inaccurate separation of gamma spectra; large sample size). At "minimized" methodological error (experiment 2), RDmeth. of samples trapping approximately 375 MS/nuclide was 5.8% and only slightly exceeded RDtheo. (5%). RDmeth. varied in the range 2.7-7.8% in individual organs and contributed little (3.5%) to the organs' observed spatial variability of flow. In contrast, RDmeth.--due to increased RDcounting--considerably exceeded RDtheo. when SAMS was low (experiment 3), overlap of two nuclides' main photopeaks was critical (experiment 1), or counting geometry was inappropriate (pulmonary tissue samples). At the same time, the contribution of RDmeth. to spatial flow variability rose to 7.9% (experiment 3), 26.9% (experiment 1), and 15-23% (lungs). Completely artifactual measurements, as indicated by an extremely high RDmeth. of sample flow, were rarely observed (less than 0.1%). In general, our data suggest that blood flow can be measured reproducibly and with low methodological error using up to 8 nuclides, RDmeth. does not essentially contribute to the observed spatial variability of organ blood flow, and, hence, organ flow variability may be accurately quantified using the MS technique. However, if sources of error as indicated above are present, the practice of using RDtheo. as a measure of RDmeth. (thereby neglecting RDcounting) may notably underestimate true MS error and result in an overestimation of spatial heterogeneity of organ blood flow. RDmeth., therefore, should be quantified separately in each region of interest prior to the onset of a new study.

Animals↗
PubMed1991

Perfusion of the interventricular septum during ventilation with positive end-expiratory pressure.

OBJECTIVE: To determine whether regional hypoperfusion of the interventricular septum occurs during ventilation with positive end-expiratory pressure. DESIGN: Animal study. ANIMALS: Anesthetized, closed chest dogs (n = 8). INTERVENTIONS: Induction of experimental adult respiratory distress syndrome (ARDS) and then ventilation with 10, 15, and 20 cm H2O of positive end-expiratory pressure. MEASUREMENTS AND MAIN RESULTS: Cardiac output and regional interventricular septum blood flow were assessed at control, at induction of experimental ARDS, and at each level of positive end-expiratory pressure. Ventilation with 20 cm H2O of positive end-expiratory pressure decreased cardiac output (-32% vs. control, p less than .05), and did not change absolute, but increased relative (to cardiac output) interventricular septum blood flow. During experimental ARDS and ventilation at 20 cm H2O end-expiratory pressure, there was a redistribution of flow toward the right ventricular free wall (+93%, p less than .001) and the right ventricular part of the interventricular septum (+68%, p less than .01), while flow to the left ventricular interventricular septum and to the left ventricular free wall remained unchanged. Locally hypoperfused interventricular septum areas or findings indicative of interventricular septum ischemia were not observed during positive end-expiratory pressure. CONCLUSIONS: The decrease in cardiac output during positive end-expiratory pressure is not caused by impaired interventricular septum blood supply. The preferential perfusion of the right ventricular interventricular septum indicates increased local right ventricular interventricular septum oxygen-demand and suggests that during positive end-expiratory pressure, this part of the interventricular septum functionally dissociates from the left ventricular interventricular septum and the left ventricular free wall to support the stressed right ventricle.

Animals↗
PubMed1990

Acute pulmonary microembolism induces different regional changes in preload and contraction pattern in canine right ventricle.

STUDY OBJECTIVE: The aim of the study was to investigate the influence of acute pulmonary embolism on local myocardial preload and contraction pattern in right ventricle. DESIGN: Measurements of preload and contraction pattern were made in inflow and outflow tracts of canine right ventricular free wall by sonomicrometry. Local right ventricular preload was assessed from end diastolic segment length. Contraction pattern was assessed from pressure-length loops and quantified by calculating maximal, systolic, and postsystolic shortening, and protosystolic segment elongation. Data were obtained before and after microembolization with 100 microns glass beads in combination with oleic acid. SUBJECTS: 13 foxhounds of either sex were used, weight 20.4 +/- 4.0 kg. MEASUREMENTS AND MAIN RESULTS: Pulmonary microembolization resulted in a rise in systolic, mean, and end diastolic right ventricular pressure and pulmonary vascular resistance. At the same time, the pressure-length loops, originally triangular or oval, became rectangular in both inflow and outflow tract. Normalised end diastolic segment length increased in the inflow tract from 10.0 to 10.3 mm (p less than 0.01), but simultaneously decreased in the outflow tract, from 10.0 to 9.6 mm (p less than 0.05). Segment shortening in the inflow tract was not affected but deteriorated in the outflow tract from 11.6 to 2.7% (p less than 0.01). CONCLUSIONS: Increase in afterload due to pulmonary microembolization caused regionally different changes in local preload and segment shortening in right ventricular free wall. Clinically available measures of global right ventricular preload do not assess these local differences in preload and therefore may fail to reflect the functional state of the right ventricle accurately.

Animals↗
PubMed1990

Local and global function of the right ventricle in a canine model of pulmonary microembolism and oleic acid edema: influence of ventilation with PEEP.

Right ventricular (RV) dysfunction may occur due to increased RV afterload and, hence, might also contribute to the decrease in cardiac output following institution of PEEP in patients with adult respiratory distress syndrome (ARDS). To test this hypothesis, the authors examined the influence of PEEP on local and global RV function in 12 anesthetized dogs with experimental ARDS (eARDS) induced by pulmonary microembolization with glass beads and oleic acid. Local RV function was analyzed in the RV inflow tract (RVIT) and RV outflow tract (RVOT) by assessing both diastolic segment length, systolic segment shortening, and segment work (sonomicrometry). Global RV contractility was quantified by measuring maximum rate of pressure rise (dRVP/dtmax) and maximum velocity of contractile element shortening (Vmax). In eARDS, despite a fivefold increase in pulmonary vascular resistance, there was no change in cardiac index (CI), global RV contractility, RVIT and RVOT work, and RVIT shortening, whereas RVOT shortening decreased from 12.4 to 7.4% (P less than 0.01). Diastolic segment length increased in RVIT (P less than 0.05) but not in RVOT. PEEP of 10 cmH2O did not alter global RV contractility, RVIT and RVOT shortening, and RVIT work but reduced RVOT work (-35%; P less than 0.01) and CI (-11%; P less than 0.001). Cardiac index further decreased during PEEP of 20 cmH2O (-38%; P less than 0.001), while global RV contractility remained intact despite decreased RVIT and RVOT shortening (-32% and -69%; P less than 0.05) and work (-26% and -59%; P less than 0.01) in the presence of reduced fiber preload in both regions. From these findings, it was concluded that 1) the decreased CI during mechanical ventilation with PEEP at constant right ventricular end-diastolic pressure (RVEDP) is not caused by depressed global RV contractility in dogs with eARDS and a normal myocardium prior to insult. Decreased diastolic segment length and segment shortening during PEEP suggest that 2) PEEP reduces stroke volume by the Starling mechanism rather than by ischemia of the RV free wall. Finally, regionally incongruent changes of fiber preload indicate that 3) local differences in RV wall compliance are likely to occur subsequent to eARDS and PEEP.

Animals↗
PubMed1989

A new experimental model of ARDS and pulmonary hypertension in the dog.

The aim of this study was to establish a stable and reproducible model of pulmonary artery hypertension with concomitant ARDS-like changes of lung function and lung morphology. In eight anesthetized and ventilated dogs, 0.01 ml/kg oleic acid (OA) was given i.v. followed by repetitive injections of 100 microns glass beads (GB) into the right atrium until a mean pulmonary artery pressure of 35-40 mmHg was reached. Mean right ventricular (RVP) and pulmonary artery (PAP) pressures, pulmonary vascular resistance (PVR), lung compliance and resistance, PaO2, intrapulmonary shunt and colloidosmotic pressure (COP) were closely monitored for 150 min. PAP, RVP, and PVR considerably increased subsequent to OA/GB injection, and stabilized at a high level within 70 min, showing only a minimal decrease (PAP, RVP) or no change (PVR) during the following 80 min. A significant decrease of PaO2 and pulmonary compliance as well as an increase of resistance and intrapulmonary shunt were found as early as 30 min after the last embolization and they remained unchanged for 120 min. Reduction of COP suggested transcapillary leakage of macromolecules. Histology revealed an interstitial and intraalveolar edema. We conclude that the combined injection of oleic acid and glass beads provokes microvascular lung injury and results in stable pulmonary artery hypertension with concomitant ARDS-like changes of lung function. Thus, an acute model is provided in the dog allowing for the study of cardiac function in ARDS complicated by pulmonary artery hypertension.

Animals↗
PubMed1984

Cardiac glycoside receptors in cultured heart cells--II. Characterization of a high affinity and a low affinity binding site in heart muscle cells from neonatal rats.

The binding of [3H]ouabain has been studied in (Na+ + K+)-ATPase enriched cardiac cell membranes, as well as in cardiac muscle and non-muscle cells in culture--all obtained from hearts of neonatal rats. The binding has been correlated with ouabain-induced inhibition of (Na+ + K+)-ATPase (cardiac cell membranes) and the inhibition of active (86Rb+ + K+)-influx (cardiac muscle and non-muscle cells in culture). Furthermore, the effect of ouabain on the amplitude of cell-wall motion and contraction velocity has been studied in electrically driven cardiac muscle cells. In muscle and non-muscle cells, two classes of ouabain binding sites have been identified. In rat heart muscle cells, the high affinity binding site has a dissociation constant (KD) of 3.2 X 10(-8) M and a binding capacity (B) of 0.2 pmole/mg protein (80,000 sites/cell); the values for the low affinity binding site are: KD = 7.1 X 10(-6) M; B = 2.6 pmole/mg protein (10(6) sites/cell). The binding to both types of binding sites is depressed by K+ and abolished after heat denaturation of the cells. The kinetics of [3H]ouabain binding to rat heart muscle cells (association and dissociation rate constants, K+- and temperature-dependence of association and dissociation processes) have been characterized. In rat heart muscle and non-muscle cells, the binding of [3H]ouabain to the low affinity site results in inhibition of the (86Rb+ + K+)-influx (EC50 = 1.3 and 1.5 X 10(-5) M ouabain), a decrease in cell-K+ (EC50 = 1.9 and 1.4 X 10(-5) M) and an increase in cell-Na+ (10(-5)-10(-4) M). The ouabain-induced positive inotropic effect (increase in amplitude of cell-wall motion, increase in contraction velocity) in cardiac muscle cells is observed only at ouabain concentrations greater than or equal to 5 X 10(-6) M, and it is therefore probably attributed to occupation of the low affinity binding site. Coupling of occupation of the low affinity site by ouabain with drug-induced inhibition of the sodium pump and with drug-induced positive inotropic action is further substantiated by kinetic measurements. In contrast, occupation of the high affinity binding site does not produce any measurable inhibition of the sodium pump activity or positive inotropy.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Cardiac glycoside receptors in cultured heart cells--I. Characterization of one single class of high affinity receptors in heart muscle cells from chick embryos.

Binding of (3H)-ouabain and ouabain-induced inhibition of the sodium pump and of the (Na+ + K+)-ATPase have been characterized in cultured cardiac muscle and non muscle cells, as well as in cardiac cell membranes--all obtained from chick embryos. In both cell types, ouabain binds to a single type of binding sites in a temperature-dependent manner. The association rate but not the dissociation rate, is lowered by K+; specific binding is lost after heat-denaturation of the cells. Binding parameters (association and dissociation rate constants, activation energies for association and dissociation) are similar in muscle and non muscle cells. The dissociation constant of specific ouabain binding is 1.5 X 10(-7)M in cardiac muscle cells, and 1.9 X 10(-7)M in cardiac non muscle cells, the binding capacity being 2.6 and 2.1 pmoles/mg protein respectively. Specific binding of ouabain to the cells is coupled to inhibition of the sodium pump, as can be seen from ouabain-induced inhibition of active (86Rb+ + K+)-uptake, decrease in cellular K+, and increase in cellular Na+ (EC50 = 10(-7)-10(-6)M). The data obtained with cardiac cells are in good agreement with results found for ouabain binding (dissociation constant 4.3 X 10(-7)M) and (Na+ + K+)-ATPase inhibition (EC50 = 1.4 X 10(-6)M) in cardiac cell membranes prepared from the same tissue. Due to the experimental evidence it is concluded that the binding site for ouabain is identical with the cardiac glycoside receptor of these cells. In cardiac non muscle cells, binding of ouabain to its receptor is strictly coupled to inhibition of active K+-transport in a stoichiometric manner. In cardiac muscle cells, however, active K+-transport is inhibited by less than 10% when up to 40% of cardiac glycoside receptors have bound ouabain. It is assumed that this non-stoichiometric coupling of receptor occupancy and sodium pump inhibition in cardiac muscle cells may prevent substantial changes of Na+- and K+-contents in the heart in the presence of therapeutic levels of cardiac glycosides.

Animals↗
PubMed1984

Cardiac glycoside binding sites in cultured heart muscle cells.

Binding of (3H)-ouabain to cultured cardiac muscle and non muscle cells from chicken embryos and neonatal rats has been characterized and correlated with ouabain-induced inhibition of the sodium pump, as well as with the positive inotropic action of the drug. Cardiac muscle and non muscle cells from 10-12 day-old chicken embryos are characterized by a single class of ouabain binding sites (muscle cells: dissociation constant KD = 1.5 X 10(-7) M; binding capacity B = 2.6 pmoles/mg cell protein). Two classes of ouabain binding sites, however, have been found in cardiac muscle and non muscle cells from 1-3 day-old, neonatal rats (muscle cells: high affinity, low capacity sites: KD = 3.2 X 10(-8) M, B = 0.2 pmoles/mg protein; low affinity, high capacity sites: KD = 1.7 X 10(-6) M, B = 2.6 pmoles/mg protein). Half maximal inhibition of active (86Rb+ + K+)-influx occurs at 5.8 X 10(-7)M ouabain in chicken heart muscle cells and at 1.3 X 10(-5)M in rat heart muscle cells [( K+] = 0,75 mM). Decreases in cell-K+ (EC50 = 6.7 X 10(-7)M and 1.9 X 10(-5)M) and increases in cell-Na+ (7.4 X 10(-7) and 10(-5) - 10(-4)M) parallel ouabain-induced inhibition of the sodium pump. Up to 10(-6)M, ouabain does not affect velocity of cell wall motion in cultured rat heart muscle cells. A concentration-dependent increase in cell wall motion is observed at concentrations between 5 X 10(-6) and 5 X 10(-5)M, being indicative of a positive inotropic effect. At 10(-4)M ouabain, arrhythmias are present. Our data demonstrate the existence of one single class of cardiac glycoside receptors in cultured cardiac muscle cells from chicken embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Hyperoxia in extreme hemodilution.

Intraoperative surgical blood loss is initially replaced by infusion of red cell-free, cristalloidal or colloidal solutions. When normovolemia is maintained the ensuing dilutional anemia is compensated by an increase of cardiac output and of arterial oxygen extraction. In the ideal case, a surgical blood loss can entirely be 'bridged' without transfusion by intraoperative normovolemic hemodilution. However major blood loss results in extreme hemodilution and the transfusion of red blood cells may finally become necessary to increase arterial oxygen content and to preserve tissue oxygenation. When transfusion has to be started before surgical control of bleeding has been achieved, parts of the red blood cells transfused will get lost, thereby increasing intraoperative transfusion needs. Beside red blood cell transfusion, arterial oxygen content can be rapidly increased by ventilating the patient with 100% oxygen (hyperoxic ventilation), thus enhancing the amount of physically dissolved oxygen in plasma (hyperoxia). In experimental and clinical studies hyperoxic ventilation has emerged as a simple, safe and effective intervention to enlarge the margin of safety for hemodynamic compensation and tissue oxygenation in hemodiluted subjects experiencing major bleeding. The hyperoxia-associated microcirculatory dysregulation and impaired tissue oxygenation known to take place in the presence of a physiologic hemoglobin concentration are not encountered in hemodiluted subjects. Hyperoxic hemodilution i.e. the combination of intraoperative extreme hemodilution and hyperoxic ventilation may therefore be considered a cost-effective, safe and efficient supplement to reduce allogeneic transfusion during surgical interventions associated with high blood losses. The vast majority of the experimental and clinical investigations this new concept is based on was initiated and performed under the guidance of Prof. Konrad Messmer.

Blood Loss, Surgical↗
PubMedDate not supplied

Searching the ideal inhaled vasodilator: from nitric oxide to prostacyclin.

Today, the technique to directly administer vasodilators via the airway to treat pulmonary hypertension and to improve pulmonary gas exchange is widely accepted among clinicians. The flood of scientific work focussing on this new therapeutic concept had been initiated by a fundamental new observation by Pepke-Zaba [1]and Frostell in 1991 [2]: Both scientists reported, that inhalation of exogenous nitric oxide (NO) gas selectively dilates pulmonary vessels without a concomittant systemic vasodilation. No more than another decade ago NO was identified as an important endogenous vasodilator [3]while having merely been regarded an environmental pollutant before that time. Although inhaled NO proved to be efficacious, alternatives were sought-after due to NO's potential side-effects. In search for the ideal inhaled vasodilator another group of endogenous mediators -- the prostanoids -- came into the focus of interest. The evidence for safety and efficacy of inhaled prostanoids is -- among a lot of other valuable work -- based on a series of experimental and clinical investigations that have been performed or designed at the Institute for Surgical Research under the guidance and mentorship of Prof. Dr. med. Dr. h.c. mult. K. Messmer [4-19]. In the following, the current and newly emerging clinical applications of inhaled prostanoids and the experimental data which they are based on, will be reviewed.

Administration, Inhalation↗
PubMedDate not supplied

Improved ventricular function during inhalation of PGI(2) aerosol partly relies on enhanced myocardial contractility.

Inhaled prostacyclin (PGI(2)) aerosol induces selective pulmonary vasodilation. Further, it improves right ventricular (RV) function, which may largely rely on pulmonary vasodilation, but also on enhanced myocardial contractility. We investigated the effects of the inhaled PGI(2) analogs epoprostenol (EPO) and iloprost (ILO) on RV function and myocardial contractility in 9 anesthetized pigs receiving aerosolized EPO (25 and 50 ng.kg(-1).min(-1)) and, consecutively, ILO (60 ng.kg(-1).min(-1)) for 20 min each. We measured pulmonary artery pressure (PAP), RV ejection fraction (RVEF) and RV end-diastolic-volume (RV-EDV), and left ventricular end-systolic pressure-volume-relation (end-systolic elastance, E(es)). EPO and ILO reduced PAP, increased RVEF and reduced RVEDV. E(es) was enhanced during all doses tested, which reached statistical significance during EPO(25 ng) and ILO, but not during EPO(50 ng). PGI(2) aerosol enhances myocardial contractility in healthy pigs, contributing to improve RV function.

Administration, Inhalation↗