Search PubMed⌕ Search

Biomedical subjects

R Hotvedt

Publications and source records attributed to R Hotvedt.

24 records · Page 2Linked to original sources
PubMed1983

Electrophysiological effects of thoracic epidural analgesia in the dog heart in situ.

To investigate cardiac electrophysiological effects of thoracic epidural analgesia, a local anaesthetic solution, 0.5% bupivacaine, was administered into the thoracic epidural space in twelve pentobarbital anaesthetised dogs. Intracardiac conduction times were measured by His bundle electrography and refractoriness was determined by programmed electrical stimulation. Monophasic action potentials were recorded from the right ventricle by a suction electrode technique. Thoracic epidural analgesia increased the ventricular effective and functional refractory period, as well as the duration of the monophasic action potential. The intra-atrial and His-Purkinje conduction times and the QRS-width were not significantly influenced. AV nodal conduction time and AV nodal functional refractory period were markedly prolonged by thoracic epidural analgesia. Thoracic epidural analgesia induced AV block of the second degree in most experiments after a second dose of bupivacaine during pacing at higher frequencies. We conclude that thoracic epidural analgesia has significant cardiac electrophysiological effects which may be both antiarrhythmic and arrhythmogenic. Thoracic epidural analgesia should be used with care in patients with atrioventricular conduction disturbances.

Action Potentials↗
PubMed1982

Pentobarbital plasma concentrations and cardiac electrophysiology during prolonged pentobarbital infusion anaesthesia in the dog.

There is need for a prolonged stable level of anaesthesia, and we therefore investigated the cardiac electrophysiological effects of continuous pentobarbital infusion after initial pentobarbital injection to induce anaesthesia in dogs. Plasma concentrations of pentobarbital were measured by gas-liquid chromatography. Heart rate, atrial, atrioventricular (AV) nodal and His-Purkinje conduction times were measured by His bundle electrography, and atrial, AV nodal and ventricular refractoriness by programmed electrical stimulation. Over a 5-h observation period, continuous infusion of pentobarbital 3.5 mg X kg-1 X h-1 after an initial pentobarbital injection of 25 mg X kg-1 intravenously gave stable mean plasma concentrations of 140-135 mumol X 1(-1). The cardiac electrophysiological variables studied did not change significantly during this period. We conclude that a stable experimental model for cardiac electrophysiological studies can be obtained for several hours by continuous pentobarbital infusion.

Anesthesia, Intravenous↗
PubMed1982

Electrophysiological and mechanical effects of sulphinpyrazone on isolated rat atria.

Clinical trials suggest that sulphinpyrazone reduces the incidence of sudden death in patients having suffered a myocardial infarction. To investigate possible direct antiarrhythmic properties of sulphinpyrazone, we carried out experiments on spontaneously beating and electrically stimulated isolated rat atrial preparations. Dose-response curves for electrophysiological and mechanical effects of sulphinpyrazone were obtained. Increasing doses of sulphinpyrazone decreased the spontaneous atrial frequency, prolonged the sinus node recovery time after overdrive pacing, slightly increased the electrical threshold for excitation and decreased the contractile force. Although the mechanism by which sulphinpyrazone may reduce the incidence of sudden cardiac death is still not settled, the present study demonstrates direct electrophysiological and mechanical effects of the drug at high concentrations.

Animals↗
PubMed1980

Electrophysiological and mechanical effects of contrast media on isolated rat atria.

Cardiac complications caused by contrast media may occur during angiocardiography. The present study on spontaneously beating and electrically stimulated isolated rat atrial preparations investigated the direct effects on the myocardium of four different contrast media. A low-osmolar non-ionic compound, metrizamide, was compared with three ionic contrast media having different cation compositions: meglumine-Na-Ca metrizoate, meglumine-Na diatrizoate and meglumine iothalamate. The ionic contrast media at an organ bath concentration of 30 mg I.cm-3 produced a striking shortening of the effective refractory period. In addition, they reduced the spontaneous rate of contractions, prolonged sinus node recovery time and decreased excitability. Meglumine-Na diatrizoate and meglumine iothalamate induced great reductions in contractile force and "force-rate" product. Metrizamide influenced both the electrical and mechanical activities of the isolated rat atrial preparations to a smaller extent than the three ionic contrast media. The present study demonstrated direct arrhythmogenic and cardiodepressive effects of commonly used ionic contrast media. The low-osmolar non-ionic medium, metrizamide, appears to have lower cardiotoxicity than the ionic contrast media.

Animals↗
PubMedDate not supplied

Class III antiarrhythmic action linked with positive inotropy: antiarrhythmic, electrophysiological, and hemodynamic effects of the sea-anemone polypeptide ATX II in the dog heart in situ.

Most antiarrhythmic drugs are more or less negatively inotropic. Positively inotropic properties, however, have been demonstrated for some class III antiarrhythmic drugs. To test the hypothesis that class III antiarrhythmic effect and positive inotropy may be linked, we used the sea-anemone polypeptide ATX II, which in isolated heart muscle preparations has been shown to specifically inhibit the inactivation of the sodium channel and thereby increase action potential duration and inotropy. We used 12 pentobarbital-anesthetized dogs. Atrial arrhythmias were induced by high-rate stimulation of the right atrium in 5 dogs. Cardiac electrophysiological effects were studied by His-bundle electrography, programmed electrical stimulation, and monophasic action potential (MAP) recordings in 7 autonomically blocked dogs. ATX II (1.0-5.0 micrograms/kg i.v.) converted the arrhythmias, and in the autonomically blocked dogs markedly increased atrial and ventricular refractoriness and ventricular MAP duration without influencing atrial or ventricular conduction velocities, heart rate, or AV-nodal refractoriness. ATX II induced a marked increase in left ventricular dP/dt max. The study indicates that ATX II has class III antiarrhythmic effect, and that the electrophysiological and positive inotropic effects of ATX II have a common mechanism.

Action Potentials↗