In vitro, prospective with repeated measures.
University research laboratory.
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.
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 IC50 was similar with remifentanil and fentanyl and the Emax 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).
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.