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The purpose of the study was to compare the actions of propofol and thiopental on myocardial contractility and cellular electrophysiologic behavior. Isometric tension of isolated guinea pig right ventricular papillary muscle was studied in normal and 26 mM potassium Tyrode's solutions at various stimulation rates (after rest up to 3 Hz). Normal and slow action potentials were also recorded by conventional microelectrodes. Propofol (30, 100, and 300 microM) applied in the commercial 10% Intralipid emulsion caused dose-dependent depression of contractions at all stimulation rates, whereas Intralipid alone had no effect. Thiopental (10, 30, and 100 microM) caused depression similar to the threefold greater concentrations of propofol. Although neither drug altered the normal action potential (AP) amplitude or dV/dt max, thiopental (30 microM) increased AP duration. In the partially depolarized (26 mM potassium) beta-adrenergically stimulated myocardium, propofol and thiopental caused dose-dependent contractile depression similar to that in normal Tyrode's solution. Whereas propofol did not alter slow AP characteristics, 30-100 microM thiopental increased slow AP duration (consistent with decreased potassium conductance), and 100 microM thiopental depressed dV/dt max (consistent with decreased calcium channel ionic influx). Comparing the clinical plasma concentration ranges required for an equivalent anesthetic effect, propofol depresses myocardial contractility less than thiopental.

PurposeTarget-controlled infusion (TCI) of remifentanil can suppress coughing during emergence from general anesthesia; nevertheless, previous studies under different clinical conditions recommend significantly different effective effect-site concentrations (effective Ce) of remifentanil for 50% of patients (EC50). The differences among these studies include type of surgery and patient sex. In recent years, study of sex differences in regards to anesthetic pharmacology has drawn greater interest. Accordingly, we attempted to determine the effective Ce of remifentanil for preventing cough for each sex under the same clinical conditions.Materials and MethodsTwenty female and 25 male ASA physical status I-II grade patients between the ages of 20 and 46 years who were undergoing thyroidectomy were enrolled in this study. The effective Ce of remifentanil for preventing cough was determined for each sex using the isotonic regression method with a bootstrapping approach, following Dixon's up-and-down method.ResultsIsotonic regression with a bootstrapping approach revealed that the estimated EC50 of remifentanil for preventing coughing during emergence was significantly lower in females {1.30 ng/mL [83% confidence interval (CI), 1.20-1.47 ng/mL]} than in males [2.57 ng/mL (83% CI, 2.45-2.70 ng/mL)]. Mean EC50 in females was also significantly lower than in males (1.23±0.21 ng/mL vs. 2.43±0.21 ng/mL, p<0.001). Mean arterial pressure, heart rate, and respiratory rate over time were not significantly different between the sexes.ConclusionWhen using remifentanil TCI for cough prevention during anesthetic emergence, patient sex should be a considered for appropriate dosing.