title: Effects of augmenting cardiac contractility, preload, and heart rate on cardiac output during enflurane anesthesia.
abstract: Changes in cardiac output in response to augmenting cardiac contractility, preload, and heart rate during enflurane anesthesia were examined in 12 open-chested dogs. Cardiac contractility was assessed by the slope of the end-systolic pressure-volume relation (Emax). Dobutamine (3, 6, and 9 micrograms.kg-1.min-1) was administered to augment cardiac contractility. Autologous blood (5.0 and 10 mL/kg) was infused to increase preload. Atrial pacing was used to increase the heart rate by about 30%. Cardiac output decreased from 96 +/- 4 (0% enflurane) (mean +/- SE) to 73 +/- 5 (1.7% enflurane) and to 46 +/- 7 mL.kg-1.min-1 (3.4% enflurane), concomitantly with decreases in Emax from 6.0 +/- 1.2 (0% enflurane) to 4.5 +/- 1.2 (1.7% enflurane) and to 2.5 +/- 0.5 mm Hg/mL (3.4% enflurane). Dobutamine (3, 6, and 9 micrograms.kg-1.min-1) increased Emax from 69% +/- 7% (compared to 0% enflurane with no dobutamine) to 139% +/- 15%, 167% +/- 25%, and 183% +/- 35% at 1.7% enflurane, and from 43% +/- 8% to 78% +/- 7%, 137% +/- 20%, and 157% +/- 22% at 3.4% enflurane, respectively. The decreases in cardiac output by 1.7% and 3.4% enflurane were reversed by the intravenous administration of 3 micrograms.kg-1.min-1 of dobutamine. Cardiac output was significantly increased by administration of 10 mL/kg of autologous blood at 1.7% enflurane, but did not significantly increase at 3.4% enflurane. Increasing the heart rate did not significantly increase cardiac output at 1.7% and 3.4% enflurane. The results of this study suggest that increasing cardiac contractility is the most effective therapeutic means of reversing circulatory depression during enflurane anesthesia.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Sato
authors.forename: S
authors.initials: S
authors.lastname: Hoka
authors.forename: H
authors.initials: H
authors.lastname: Arimura
authors.forename: K
authors.initials: K
authors.lastname: Ono
authors.forename: J
authors.initials: J
authors.lastname: Yoshitake
mesh_terms: D000758:Anesthesia; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002302:Cardiac Output / Q000187:drug effects*; D004280:Dobutamine / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004737:Enflurane / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects*
chemical_list: D004280:Dobutamine; D004737:Enflurane; D002118:Calcium