OBJECTIVE: To determine the myocardial and vascular effects of remifentanil and fentanyl in human atria and saphenous veins. DESIGN: In vitro, prospective with repeated measures. SETTING: University research laboratory. INTERVENTIONS: The direct effects of remifentanil and fentanyl on the electrical stimulation-induced contraction of nonfailing human atrium and saphenous veins contracted with 5-hydroxytryptamine were studied. MEASUREMENTS AND MAIN RESULTS: In human atrial trabeculae, cumulative (10(-9)-10(-5) mol/L) added remifentanil had no effect on contractile force, compared with untreated muscles (p > 0.05). The force of contraction was significantly less than control values with concentrations of fentanyl ranging from 10(-8) to 10(-5) mol/L (p < 0.05). At the highest concentration (10(-5) mol/L), the inhibition by fentanyl of the electrical stimulation-induced contraction was 40.6% +/- 6.32%. In human saphenous vein strips preconstricted with 5-hydroxytryptamine, remifentanil (10(-8)-10(-5) mol/L) and fentanyl (10(-8)-10(-5) mol/L) produced "concentration-dependent" relaxation when compared with the control contraction value (p < 0.05). The IC(50) was similar with remifentanil and fentanyl and the E(max) of fentanyl was significantly higher than remifentanil (p < 0.05). The venodilatory effects of remifentanil and fentanyl were similar on veins with or without endothelium (p > 0.05). CONCLUSIONS: Remifentanil has no direct effect on the contraction of myocardium. Fentanyl inhibits the electrical stimulation-induced contraction in human right atrial muscles in vitro. Remifentanil and fentanyl produce "concentration-dependent" relaxation in human saphenous vein strips independent from the endothelium.
OBJECTIVE: To determine the myocardial and vascular effects of remifentanil and fentanyl in human atria and saphenous veins. DESIGN: In vitro, prospective with repeated measures. SETTING: University research laboratory. INTERVENTIONS: The direct effects of remifentanil and fentanyl on the electrical stimulation-induced contraction of nonfailing human atrium and saphenous veins contracted with 5-hydroxytryptamine were studied. MEASUREMENTS AND MAIN RESULTS: In human atrial trabeculae, cumulative (10(-9)-10(-5) mol/L) added remifentanil had no effect on contractile force, compared with untreated muscles (p > 0.05). The force of contraction was significantly less than control values with concentrations of fentanyl ranging from 10(-8) to 10(-5) mol/L (p < 0.05). At the highest concentration (10(-5) mol/L), the inhibition by fentanyl of the electrical stimulation-induced contraction was 40.6% +/- 6.32%. In human saphenous vein strips preconstricted with 5-hydroxytryptamine, remifentanil (10(-8)-10(-5) mol/L) and fentanyl (10(-8)-10(-5) mol/L) produced "concentration-dependent" relaxation when compared with the control contraction value (p < 0.05). The IC(50) was similar with remifentanil and fentanyl and the E(max) of fentanyl was significantly higher than remifentanil (p < 0.05). The venodilatory effects of remifentanil and fentanyl were similar on veins with or without endothelium (p > 0.05). CONCLUSIONS:Remifentanil has no direct effect on the contraction of myocardium. Fentanyl inhibits the electrical stimulation-induced contraction in human right atrial muscles in vitro. Remifentanil and fentanyl produce "concentration-dependent" relaxation in human saphenous vein strips independent from the endothelium.