Anesthetics, Inhalation/pharmacology; Drug-Related Side Effects and Adverse Reactions; Halothane/pharmacology; Heart Conduction System/drug effects; Heart Ventricles/drug effects; Heart/drug effects; Long QT Syndrome/chemically induced; Action Potentials/drug effects; Adrenergic beta-Antagonists/administration & dosage; Adrenergic beta-Antagonists/adverse effects; Algorithms; Anesthetics, Inhalation/administration & dosage; Animals; Chromans/administration & dosage; Chromans/pharmacology; Delayed Rectifier Potassium Channels/drug effects; Drug Evaluation, Preclinical/methods; Electrocardiography/drug effects; Guinea Pigs; Halothane/administration & dosage; Histamine H1 Antagonists/administration & dosage; Histamine H1 Antagonists/adverse effects; Linear Models; Male; Models, Animal; Pharmaceutical Preparations/administration & dosage; Potassium Channel Blockers/administration & dosage; Potassium Channel Blockers/pharmacology; Reproducibility of Results; Sotalol/administration & dosage; Sotalol/adverse effects; Sulfonamides/administration & dosage; Sulfonamides/pharmacology; Terfenadine/administration & dosage; Terfenadine/adverse effects; Time Factors