title: Comparison of the in vitro myocardial depressant effects of isoflurane and halothane anesthesia.
abstract: The myocardial depressant effects of isoflurane and halothane were compared using feline right ventricular papillary muscles bathed in Krebs-bicarbonate solution. In experiment 1 muscles were stimulated by field electrodes (0.2 Hz) to obtain control measurements of developed tension (dt) and maximal rate of tension development (dF/dt) prior to exposing the papillary muscles to four concentrations of either isoflurane (4.0%, 2.0%, 1.0%, 0.5%) or halothane (2.0%, 1.0%, 0.5%, 0.25%). Repeat measurements of dt and dF/dt were recorded after 20 min at each concentration. Isoflurane and halothane both caused dose-dependent depression of dt and dF/dt, but at 0.5%, 1.0%, and 2.0%, halothane was significantly more depressant than isoflurane (P less than 0.01 for dt and dF/dt). Quadratic equations were fitted to the dose-response data by least squares analysis (R2 greater than .985 for both anesthetics), and the isoflurane and halothane concentrations that decreased dt to 90%, 70%, 50%, and 30% of control were determined to compare the relative myocardial depressant potency of isoflurane and halothane by linear regression analysis. This potency relationship is described by the equation: isoflurane concentration = -0.005 + 1.445 (halothane concentration). In experiment 2 papillary muscle responses at two similar cardiodepressant concentrations of isoflurane (1.25% and 2.0%) or halothane (0.80% and 1.35%) were compared at stimulus frequencies of 0.05, 0.1, 0.2, 0.4, 0.8, 1.0, and 2.0 Hz. The concentrations of isoflurane and halothane were selected from the data obtained in experiment 1 and represent the anesthetic concentrations that diminish muscle function to approximately 70% and 50% of control.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, University of Texas Medical Branch, Galveston 77550.
authors.forename: W J
authors.initials: WJ
authors.lastname: Wolf
authors.forename: M B
authors.initials: MB
authors.lastname: Neal
authors.forename: B P
authors.initials: BP
authors.lastname: Mathew
authors.forename: D E
authors.initials: DE
authors.lastname: Bee
mesh_terms: D000818:Animals; D002415:Cats; D003864:Depression, Chemical; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects*
chemical_list: D007530:Isoflurane; D006221:Halothane