thiopental and Tachycardia--Supraventricular

Desflurane has several properties making it a desirable agent for use in electrophysiological studies (EPS) for diagnosis and treatment of cardiac dysrhythmias. We studied 47 children, mean age 12.8+/-4.6 years, mean weight 52.9+/-24.0 kg, with clinical history of supra- ventricular tachycardia (SVT) during EPS using desflurane in a crossover comparison with fentanyl. The patients served as their own controls. All received oral premedication with lorazepam, and intravenous induction with thiopentone, rocuronium, and oxygen. Group 1 (n=24) were administered fentanyl 10 microg.kg-1 bolus i.v. with an infusion of 3 microg.kg-1.h-1 during initial EPS. Fentanyl was discontinued and desflurane, 6% endtidal, was administered and the EPS repeated. Group 2 (n=23) were initially administered 6% desflurane after induction, and following EPS the desflurane was discontinued and the patients administered fentanyl 3 microg.kg-1 bolus and EPS repeated (explanations of EPS abbreviations are provided). Desflurane reduced the mean arterial pressure (MAP) in all patients. In Group 1, desflurane shortened the sinus cycle length (SCL), i.e. increasing the heart rate, and atrial effective refractory period (AERP) while Group 2 demonstrated no such effect on AERP. There were no other significant differences between fentanyl or desflurane techniques in terms of EPS measurements. SVT was inducible with both agents in both groups. Desflurane seems an acceptable agent for use during EPS procedures.

Topics: Administration, Oral; Androstanols; Anesthetics, Inhalation; Anesthetics, Intravenous; Atrial Function; Blood Pressure; Catheter Ablation; Child; Cross-Over Studies; Desflurane; Electrocardiography; Fentanyl; Heart Rate; Humans; Hypnotics and Sedatives; Isoflurane; Lorazepam; Neuromuscular Nondepolarizing Agents; Preanesthetic Medication; Refractory Period, Electrophysiological; Rocuronium; Statistics as Topic; Tachycardia, Supraventricular; Thiopental

Supraventricular tachydysrhythmias such as atrial fibrillation frequently complicate the perioperative period. Two electrophysiologic factors critical to the pathogenesis of supraventricular tachydysrhythmias are: 1) atrial wavelength, the product of atrial conduction velocity (CV) and effective refractory period (ERP), and 2) atrioventricular nodal conduction. Modulation of these factors by drugs has important clinical ramifications. The authors studied the effects of propofol, thiopental, and ketamine on atrial wavelength and atrioventricular nodal function in guinea pig isolated atrial trabeculae and hearts, respectively.. Electrocardiogram recordings in superfused atrial tissue were obtained using hanging microelectrodes. A stimulating and two recording electrodes were placed on a single atrial trabecula, and the interelectrode distance was measured. Atrial ERP determinations were made using a premature stimulus protocol. The time (t) required for a propagated impulse to traverse the interelectrode distance (d) was measured. Conduction velocity was calculated as d/t. Langendorff-perfused guinea pig hearts were instrumented for low atrial pacing (cycle length = 300 ms) and for measurements of stimulusto-His bundle interval, an index of atrioventricular nodal conduction. To investigate the frequency-dependent behavior of the atrioventricular node, computer-based measurements were made of Wenckebach cycle length (WCL) and atrioventricular nodal ERP.. Thiopental significantly prolonged atrial ERP in a concentration-dependent manner, whereas propofol and ketamine had no significant effect on atrial refractoriness. In contrast, ketamine caused a dose-dependent decrease in atrial CV, but propofol and thiopental had no significant effect on CV. Therefore, thiopental, ketamine, and propofol caused an increase, a decrease, and no change, respectively, in atrial wavelength. All anesthetics caused a concentration-dependent prolongation of the stimulus-to-His bundle interval, atrioventricular nodal ERP, and WCL. However, on an equimolar basis, significant differences in potencies were found. The concentrations of drug that caused a 20% increase in ERP (ERP20) and WCL (WCL20) for propofol, thiopental, and ketamine were 14 +/- 2 microM, 26 +/- 3 microM, and 62 +/- 11 microM, and 17 +/- 2 microM, 50 +/- 1 microM, and 123 +/- 19 microM (mean +/- SEM), respectively. Therefore, the rank order of potency for frequency-dependent atrioventricular nodal effects is propofol > thiopental > ketamine.. The authors' results indicate that propofol would be most effective at filtering atrial impulses during supraventricular tachydysrhythmias, whereas thiopental would be most effective at preventing atrial reentrant dysrhythmias. In contrast, ketamine may be most likely to promote atrial reentry while having minimal effect on atrioventricular nodal conduction.

Topics: Anesthetics, Intravenous; Animals; Anti-Arrhythmia Agents; Atrial Function; Atrioventricular Node; Electrocardiography; Female; Guinea Pigs; In Vitro Techniques; Ketamine; Kinetics; Male; Propofol; Refractory Period, Electrophysiological; Synaptic Transmission; Tachycardia, Supraventricular; Thiopental

Topics: Anesthesia, General; Anesthetics, Inhalation; Anesthetics, Intravenous; Catheter Ablation; Child; Diazepam; Halothane; Humans; Hypnotics and Sedatives; Intubation, Intratracheal; Laryngoscopy; Neuromuscular Nondepolarizing Agents; Preanesthetic Medication; Tachycardia, Supraventricular; Thiopental; Vecuronium Bromide