title: Effect of general anesthesia on cardiac vagal tone.
abstract: Although it is accepted that general anesthetics alter cardiac vagal tone, the magnitude of this effect was difficult to quantify by noninvasive methods until recently. Twenty-eight mongrel dogs were anesthetized using one of four representative anesthetics: pentobarbital sodium (25 mg/kg iv), morphine (1 mg/kg sc) with alpha-chloralose (50 mg/kg iv), urethan (500 mg/kg iv), thiopental sodium (25 mg/kg iv), and halothane (2% inhalation). Heart period (R-R interval) was recorded, from which the amplitude of the respiratory sinus arrhythmias (RSAs; frequency 0.24-1.04 Hz) was determined by time-series analysis. Morphine with alpha-chloralose-urethan significantly (P less than 0.01) increased RSA (control 8.3 +/- 0.6 ln ms2, anesthesia 9.4 +/- 0.3 ln ms2), whereas thiopental and halothane both significantly (P less than 0.01) decreased RSA (control 8.7 +/- 0.4 ln ms2, thiopental 1.3 +/- 0.4 ln ms2; and control 8.5 +/- 0.6 ln ms2, halothane 3.6 +/- 0.8 ln ms2). Pentobarbital failed to elicit a consistent change in RSA. These data suggest that vagal tone was maintained during morphine with alpha-chloralose-urethan anesthesia but was reduced during thiopental and halothane anesthesia.
authors.affiliation: Department of Physiology, Ohio State University, Columbus 43210.
authors.forename: J R
authors.initials: JR
authors.lastname: Halliwill
authors.forename: G E
authors.initials: GE
authors.lastname: Billman
mesh_terms: D000704:Analysis of Variance; D000768:Anesthesia, General; D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D004285:Dogs; D006329:Heart Conduction System / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D000777:Anesthetics