Cardiac arrhythmias: drugs and devices.

This review focuses on the important role played by the various types of remedial therapy in the prevention and treatment of perioperative cardiac arrhythmias. It discusses the new concepts of arrhythmogenesis and pro-arrhythmia; the long QT interval syndrome; newer, more selective class 3 antiarrhythmic drugs; cardiac rhythm management devices; drugs or devices used as prophylaxis for postoperative atrial arrhythmias; intravenous amiodarone for destabilizing ventricular arrhythmias; and preoperative potassium imbalance.

Operational sustainability metrics assessing metric effectiveness in the context of electronics-recycling systems.

In the past 15 years corporations and governments have developed a growing appreciation of the need for sustainability. However, there is still little clarity on how to move toward the goal of sustainability or measure improvements. Not only are there currently few operational metrics by which to practically assess progress toward sustainability, there is also little understanding of how to judge the effectiveness of such metrics.

Comparison of a prototype esophageal oximetry probe with two conventional digital pulse oximetry monitors in aortocoronary bypass patients.

Objective: Pulse oximetry (SpO2) is the non-invasive standard for monitoring arterial oxygen saturation in patients undergoing anesthesia, but is subject to external interference by motion artifact, peripheral vasoconstriction, and low cardiac output. We hypothesized that oximetry signals could be acquired from the esophagus when peripheral pulse oximetry is unobtainable. Therefore, we tested an esophageal stethoscope which incorporates transverse oximetry photodetectors and emitters in patients undergoing coronary bypass surgery.

The use of esmolol, nicardipine, or their combination to blunt hemodynamic changes after laryngoscopy and tracheal intubation.

Unlabelled: Laryngoscopy and tracheal intubation (LTI) often provoke an undesirable increase in blood pressure (BP) and/or heart rate (HR). We tested the premise that nicardipine (NIC) and esmolol (ESM) in combination (COMB) would oppose both. Adult surgical patients received pretreatment (randomized) with IV bolus NIC 30 microg/kg (n = 31), ESM 1.

The effects of the new antiarrhythmic E 047/1 on postoperative ischemia-induced arrhythmias in dogs.

Unlabelled: Perioperative malignant ventricular tachyarrhythmias pose an imminent clinical danger by potentially precipitating myocardial ischemia and severely compromising hemodynamics. Thus, immediate and effective therapy is required, which is not always provided by currently recommended IV drug regimens, indicating a need for more effective drugs. We examined antiarrhythmic effects of the new benzofurane compound E 047/1 on spontaneous ventricular tachyarrhythmia in a conscious dog model.

Perioperative ventricular dysrhythmias in patients with structural heart disease undergoing noncardiac surgery.

Unlabelled: Noncardiac surgical patients with preoperative ventricular dysrhythmias and structural heart disease may be at increased risk of adverse cardiac outcome. We evaluated how anesthesia and surgery affect the course of ventricular dysrhythmias (premature ventricular beats [PVB] and repetitive forms of ventricular beats [RFVB]: couplets and nonsustained ventricular tachycardia) noted preoperatively in patients with structural heart disease and whether the frequency of ventricular dysrhythmias affects cardiac outcome. In a prospective study, 70 patients scheduled for noncardiac surgery with structural heart disease and RFVB on preoperative Holter electrocardiogram were continuously monitored intraoperatively and for 3 days postoperatively.

Anesthetics and automaticity of dominant and latent pacemakers in chronically instrumented dogs. IV. Dysrhythmias after sinoatrial node excision.

Background: Subsidiary atrial pacemakers assume control after sinoatrial (SA) node excision, and anesthetic-catecholamine interactions can produce severe bradycardia during isoflurane anesthesia. We hypothesized that epinephrine enhances atrial, atrioventricular junctional, and ventricular dysrhythmias after SA node excisions in dogs and that inhalation anesthetics would facilitate such dysrhythmias.

Methods: In eight dogs, SA nodes were excised and epicardial electrodes implanted at the atrial appendages, at the His bundle, and along the sulcus terminalis.

Muscarinic and ganglionic blocking properties of atropine compounds in vivo and in vitro: time dependence and heart rate effects.

High doses (3 mg/kg) of methylatropine nitrate have been used in vivo to produce long-lasting muscarinic blockade during physiologic experiments. At these levels, the possibility exists that ganglionic blockade may also be responsible for some heart rate effects. Therefore, the effects of methylatropine nitrate (0.

Anesthetics and automaticity of dominant and latent atrial pacemakers in chronically instrumented dogs. III. Automaticity after sinoatrial node excision.

Background: Management of patients with sinus node dysfunction must consider the stability of subsidiary pacemakers during anesthesia and treatment with antimuscarinic or sympathomimetic drugs. Baroreflex regulation of atrial pacemaker function is known to contribute to the interactions between inhalation anesthetics and catecholamines. Sinoatrial (SA) node excision can be a model for intrinsic SA node dysfunction.

Anesthetics and automaticity of dominant and latent pacemakers in chronically instrumented dogs. II. Effects of enflurane and isoflurane during exposure to epinephrine with and without muscarinic blockade.

Background: Atrial dysrhythmias precede ventricular dysrhythmias during epinephrine-anesthetic sensitization, and may be caused by an altered relationship between automaticity of primary and subsidiary pacemakers. The following hypotheses were tested: (1) epinephrine-induced pacemaker shifts with enflurane or isoflurane require intact vagal reflexes and (2) these anesthetics sensitize the atrial myocardium to epinephrine-induced dysrhythmias.

Methods: Eight dogs were instrumented for chronic electrophysiologic investigation, including electrodes at the SA node, atrial appendages, right ventricle, and His bundle, and along the sulcus terminalis.

Anesthetics and automaticity of dominant and latent pacemakers in chronically instrumented dogs. I. Methodology, conscious state, and halothane anesthesia: comparison with and without muscarinic blockade during exposure to epinephrine.

Background: Supraventricular dysrhythmias are common during anesthesia, but have been incompletely investigated. Mechanisms may involve altered automaticity of subsidiary pacemakers and participation of vagal reflexes. The following hypotheses were tested: (1) shifts from the sinoatrial (SA) node to subsidiary pacemakers require intact vagal reflexes and (2) halothane sensitizes the heart to epinephrine-induced atrial pacemaker shifts.

Anesthetics and automaticity in latent pacemaker fibers. IV. Effects of isoflurane and epinephrine or norepinephrine on automaticity of dominant and subsidiary atrial pacemakers in the canine heart.

Background: Anesthesia and surgery may be associated with atrioventricular junctional or ventricular rhythm disturbances. These may be caused by alteration of automaticity of primary and subsidiary pacemakers.

Methods: The direct effects of isoflurane, alone or in combination with epinephrine (E) and norepinephrine (NE), as well as single effects of E and NE, were examined on automaticity of primary and subsidiary atrial pacemakers (SAP) using a perfused canine right atrial preparation (n = 29).

Transesophageal atrial pacing for intraoperative sinus bradycardia or AV junctional rhythm: feasibility as prophylaxis in 200 anesthetized adults and hemodynamic effects of treatment.

Sinus bradycardia (SB) or atrioventricular junctional rhythm (AVJR) may produce circulatory insufficiency in anesthetized surgical patients, especially those with cardiovascular disease. Chronotropic drugs have been the preferred initial treatment, except when epicardial pacing is available. Alternative methods include transvenous or transcutaneous pacing.

Evaluation of transesophageal atrial pacing stethoscope in adult surgical patients under general anesthesia.

Sinus bradycardia (SB) and atrioventricular junctional rhythm (AVJR) commonly cause circulatory insufficiency in anesthetized surgical patients. Treatment is usually with drugs, which can be ineffective or have adverse effects. Cardiac pacing might be preferred, but the transvenous or epicardial routes are too invasive for routine use, and transcutaneous pacing fails to preserve atrial transport function.

Comparison of logdose and bracket protocols for determination of epinephrine arrhythmia thresholds in dogs anesthetized with thiopental-halothane.

Previous studies in dogs of anesthetic-epinephrine arrhythmias have used logdose or bracketed epinephrine infusion protocols to determine the arrhythmic dose of epinephrine (ADE) or plasma level of epinephrine at arrhythmias (PCE). Reported logdose ADE values for halothane preceded by thiopental induction (thiopental-halothane) are twice those with the bracket protocol. There are no reported PCE data for the bracket protocol, and neither protocol has been directly compared in the same dogs.

Halothane, enflurane and isoflurane on abnormal automaticity and triggered rhythmic activity of Purkinje fibers from 24-hour-old infarcted canine hearts.

The effects of inhalation anesthetics halothane, enflurane, and isoflurane on spontaneous impulse initiation (automaticity) and triggered sustained rhythmic activity were examined in Purkinje fibers derived from normal (n = 38) and 24-h-old infarcted canine hearts (n = 27) to further understanding of their influence on the cellular mechanisms underlying generation of cardiac arrhythmias. Purkinje fibers from normal or infarcted hearts were superfused with modified Krebs' solution (37 degrees C) with or without epinephrine (2 or 15 microM) and equilibrated with a 97% O2-3% CO2 gas mixture (control). Transmembrane action potentials were recorded using conventional microelectrode techniques, and Purkinje fibers were exposed to anesthetic concentrations equivalent to 2.

Anesthetics and automaticity in latent pacemaker fibers. III. Effects of halothane and ouabain on automaticity of the SA node and subsidiary atrial pacemakers in the canine heart.

Atrial tachyarrhythmias are a common manifestation of digitalis toxicity. Such arrhythmias could be due to enhanced automaticity of subsidiary atrial pacemakers (SAP) compared to the sinoatrial (SA) node. Halothane is known to oppose digitalis-induced ventricular arrhythmias.

Anesthetics and automaticity in latent pacemaker fibers. II. Effects of halothane and epinephrine or norepinephrine on automaticity of dominant and subsidiary atrial pacemakers in the canine heart.

Knowledge of anesthetic effects on the automaticity of dominant and subsidiary cardiac pacemakers is fundamental to an understanding of mechanisms of arrhythmia during anesthesia, as well as to the management of patients with sinus node dysfunction or atrioventricular (AV) conduction block. Among potential pacemakers of the heart are subsidiary atrial pacemakers (SAP), which are located outside the classic sinoatrial (SA) node region but still within the right atrium. SAP have a higher inherent rate of automaticity than AV junctional pacemakers, may contribute to a multicentric atrial pacemaker complex, and can control the rhythm of the heart when the SA node is absent or inhibited.