Biomedical subjects

H J Döring

Publications and source records attributed to H J Döring.

At least 19 recordsLinked to original sources

PubMed1998

Therapeutic suggestions given during neurolept-anaesthesia decrease post-operative nausea and vomiting.

A double-blind randomized study was performed in 100 patients undergoing thyroidectomy to evaluate the effect of positive therapeutic suggestions made during neurolept-anaesthesia. The classic droperidol-fentanyl-N2O technique was used as these drugs preserve the neurophysiological functions required to process the information in the therapeutic suggestions given during general anaesthesia. Patients in the suggestion group heard positive non-affirmative suggestions during the whole operation. An autoreverse tape player was used. The control group listened to an empty tape. Both groups were comparable with respect to demographic variables, anaesthetic technique, drug dosage, duration of anaesthesia and surgery. Patients in the suggestion group suffered significantly less from post-operative nausea or vomiting (suggestion: 47.2% vs. control: 85.7%) and required less anti-emetic treatment (suggestion: 30.6% vs. control: 68.6%). We conclude that therapeutic suggestions heard during neurolept-anaesthesia are processed and decrease post-operative nausea and vomiting in patients after thyroidectomy.

Anesthesia, General↗

PubMed1990

The isolated perfused heart according to Langendorff technique--function--application.

1. Definition. The isolated perfused heart according to Langendorff is a preparation which is easily obtained from all warm-blooded animals. The heart is usually perfused at constant pressure, but frequently at constant flow, mostly with oxygenated saline solutions. The ventricles do not fill with the perfusate and therefore do not perform pressure-volume work. If, however, an intraventricular balloon is inserted, the ventricle can contract isovolumetrically. 2. Measuring parameters. Mechanical parameters of the working myocardium (contractile force, volume, ventricular diameter), mean coronary flow, bioelectrical parameters (EKG, monophasic injury potentials), and cardiac rhythm can be measured and recorded. 3. Function tests. The intact function of the working myocardium and the coronary vessels should be examined using various simple tests regarding the myocardium, the smooth musculature, and the endothelium of coronary vessels. 4. Possible applications. In the Langendorff-heart of normal or pretreated animals, inotropic, chronotropic, antiarrhythmic or vasoactive substances can be investigated in the steady state or by means of specific stress tests. In addition, the preparation is particularly suitable for biochemical studies of myocardial metabolism. 6. Advantages. Due to the technical ease with which a variety of parameters can be measured, a single heart can provide maximum information about the condition of the myocardium and the coronary vessels. Thus, it is not surprising to find that 90 years after its first description, the isolated perfused heart according to Langendorff continues to be utilized.

Animals↗

PubMed1989

Differentiation of various cardiovascular drugs by means of specific myocardial and vascular load tests. Experiments at the isolated perfused heart.

A new method is described for examining the contractile function of myocardium and coronary vasculature in the isolated perfused, electrically stimulated guinea-pig and rat heart which is suitable for investigation of cardiovascular drugs. The criterion used for functional efficiency of myocardium and coronary vasculature is--in addition to the usual evaluation of cardiac force and coronary flow in steady-state--the reaction of the heart to perfusion pressure changes: abrupt increase of the perfusion pressure (PP) leads to an increase in cardiac force (= heterometric autoregulation, HA) and simultaneously to triggering of the myogenic autoregulation (MA). Using this PP loading two different functional tests can be performed: 1. By successive PP increases in 10-20 mmHg steps it is possible to determine a) an equivalent of Frank-Starling cardiac function curves, and b) pressure-flow (p-F) curves of the coronary vasculature, e.g. before and after drug application. 2. By a single PP step of e.g. 40 mmHg HA and MA are triggered before and after drug application, calculated as percentages of the initial value and plotted as concentration-response curves. Both methods produce a physiologically based description of cardiac and coronary mechanics. In particular, the behaviour of the coronary vasculature in this procedure represents a more sensitive criterion than total coronary flow in steady-state. Since HA and MA depend partly (HA) or completely (MA) on the slow transmembrane Ca++ inward current the method is particularly suitable for a basic differentiation of Ca++ and Na+ antagonistic drugs.

Animals↗

PubMed1987

Mechanically induced ventricular extrasystoles in the isolated perfused guinea-pig heart. A model to study cardiac arrhythmia and to differentiate antiarrhythmic drugs.

Pressure pulses applied to an isolated perfused guinea-pig heart via underwater hydrodynamic pressure waves during early diastole induce ventricular extrasystoles (VES). Intensity of pulse pressure and number of VES in relation to number of stimuli show a narrow and reproducible relation following a sigmoid function. Thus we were able to establish a pressure dose-response function between hydrodynamic peak pressure and percentage of VES-responses to mechanical stimulation. In overriding the natural heart rate a ventricular rhythm can be maintained for several hours. In the hypoxic or anoxic heart repetitive automatism can be induced by pulse pressure stimulus. In severe ischemia ventricular fibrillation may occur. In this model differentiation between various classes of antiarrhythmic drugs seems possible in setting up pressure dose-response curves for different concentrations of these drugs. The inhibition of VES is limited to class I antiarrhythmic drugs (quinidine, lidocaine) while specific Ca-antagonists (class IV) are ineffective, thus showing that induction of VES is mediated by a Na channel-dependent process. Preliminary data show that these results can be extended to in situ experiments using an external mechanical stimulator.

Animals↗

PubMed1975

[Key-role of intracellular calcium overload in acute necrosis of the myocardium. Cardioprotection with verapamil].

Ca ions are highly cardiotoxic if their influx into the myocardial fibres becomes abundant. The intracellular Ca overload initiates a deleterious high-energy phosphate deficiency by excessive activation of Ca-dependent intracellular ATPases and by impairing the phosphorylating capacity of mitochondria. This Ca-induced high-energy phosphate exhaustion is a crucial point in the etiology of the myocardial fibre necroses produced in rats by large doses of beta-adrenergic catecholamines, particularly isoproterenol, or by a number of other cardiotoxic agents. Accordinly, the myocardium is sensitized to necrotization by factors which favour Ca overload (dihydrotachysterol, 9alpha-flourocortisol acetate, NaH2PO4). Conversely, the structural integrity of the hearts can be protected by any substance or procedure which prevents an excessive intracellular Ca accumulation, particularly by inhibitors of the transmembrane Ca influx, such as verapamil, D 600 or prenylamine.

Adenosine Triphosphate↗

PubMed1975

Key role of Ca in the production of noncoronarogenic myocardial necroses.

Skeletal and heart muscle fibers undergo severe functional and structural alterations, resulting in necrotization as soon as extracellular Ca ions penetrate excessively into the sarcoplasm, so that the capacities of the Ca binding or extrusion processes become insufficient. In mechanically injured skeletal muscle fibers, this necrotization process begins in the neighborhood of the membrane lesion where a large Ca inward transport takes place. Accordingly, elimination of Ca from the Ringer solution or an outward electric current which blocks the influx of extracellular Ca prevents the onset of necrotization, whereas additional Ca or an inward electric current which augments the influx of Ca potentiates the course of degradation. The crucial reaction in the production of necroses in skeletal and heart muscle fibers is a high energy phosphate deficiency which results (a) from excessive activation of Ca-dependent intracellular ATPases, and (b) from Ca-induced mitochondrial destruction. This applies especially to myocardial fiber damage caused by large doses of beta-adrenergic catecholamines such as isoproterenol. The number and size of the isoproterenol-induced cardiac lesions are obviously determined by the extent and, particularly, by the duration of the Ca-mediated high energy phosphate penury. Substances which sensitize the myocardium to catecholamine-induced necrotization (9-alpha-fluorocortisol, dihydrotachysterol, NaH2PO4) act by potentiating intracellular Ca overload and high energy phosphate breakdown. Conversely, verapamil D 600, and other Ca-antagonistic compounds protect the structural integrity of the heart muscle fibers by restricting transmembrane Ca influx and, consequently, ATP and creatine phosphate exhaustion.

Adenosine Triphosphate↗

PubMed1975

Attenuation of beta-adrenergic cardiac responses in chronically hypoxic rats with right ventricular hypertrophy.

Rats were kept for 30 days in an O2-N2-mixture of gradually reduced O2 (18 leads to 6 Vol%) and constant CO2 (0.5 Vol percent). This induces a selective hypertrophy of the right ventricle and the ratio ventricular/body weight (g/kg) increased from 0.6 to 1.4 while it remained constant in the left heart. In the right and left ventricles of control animals the contents of myocardial ATP (4.0 muM/g) and of phosphocreatine (CP) (5.8 muM/g) were the same. These values were not significantly changed by hypertrophy. In the control animals, a single test-dose of isoproterenol (30 mg/kg), subcutaneously administered 2 hr before the heart was removed, caused a diminution of the ATP-content by 15 percent in the right ventricle and by 40 percent in the left. The CP-content was reduced by 40 percent on the right and by 50 percent on the left side. In the hypertrophied right ventricle, however, there was no major decrease in ATP and CP following the isoproterenol injection. In the nonhypertrophied left heart the response to isoproterenol was still detectable but much less than normal. As the chronotropic and hypotensive effects of isoproterenol were also lessened in the hypoxic animals it is concluded that a general reduction in the responsiveness to beta-adrenergic stimulation has occurred.

Animals↗

PubMed1975