title: Effect of lidocaine and bretylium on energy requirements for transthoracic defibrillation: experimental studies.
abstract: The purpose of this study was to determine the effect of the antiarrhythmic drugs lidocaine and bretylium on the minimal energy requirement for transthoracic defibrillation--the defibrillation threshold. Closed chest dogs were anesthetized with chloralose or pentobarbital; lidocaine was administered at varying rates for 2 hours and defibrillation threshold periodically redetermined. Similar protocols were followed for bretylium. Serum lidocaine levels from therapeutic to toxic ranges were obtained, and up to a 60% (p less than 0.05) increase in defibrillation threshold in the pentobarbital-anesthetized dogs was demonstrated. In chloralose-anesthetized dogs the lidocaine effect was modest, with only a 10 to 20% rise in defibrillation threshold (p = NS) despite similar increases in serum lidocaine levels. Thus, lidocaine increases the minimal energy requirements for transthoracic defibrillation, but this effect is in part anesthesia-related, indicating a lidocaine-pentobarbital interaction. When phentolamine was administered to chloralose-anesthetized dogs receiving lidocaine, defibrillation threshold rose 13% (p less than 0.05); this suggests that alpha-adrenergic receptor blockade is at least in part the mechanism of the pentobarbital-lidocaine interaction on defibrillation threshold. Bretylium with either anesthetic had no significant effect on defibrillation threshold.
mesh_terms: D000818:Animals; D001949:Bretylium Compounds / Q000494:pharmacology*; D001950:Bretylium Tosylate / Q000494:pharmacology*; D002698:Chloralose; D004285:Dogs; D004347:Drug Interactions; D004554:Electric Countershock; D008012:Lidocaine / Q000097:blood / Q000494:pharmacology*; D010276:Parasympatholytics / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology; D010424:Pentobarbital / Q000494:pharmacology; D013565:Sympatholytics / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*
chemical_list: D001949:Bretylium Compounds; D010276:Parasympatholytics; D010277:Parasympathomimetics; D013565:Sympatholytics; D013566:Sympathomimetics; D002698:Chloralose; D001950:Bretylium Tosylate; D008012:Lidocaine; D010424:Pentobarbital