VERAPAMIL AND NITROUS-OXIDE EXERT ONLY MINOR EFFECTS ON THE NORMAL MYOCARDIUM IN THE PRESENCE OF FENTANYL

While the association of inhalational anaesthetics and verapamil has been shown to cause myocardial dysfunction, the interactions between fentanyl, verapamil and nitrous oxide on regional function in normal hearts have not been investigated. Seven mongrel dogs were instrumented to measure aortic and left-ventricular pressure, aortic blood flow and apical and basal regional left-ventricular function (sonomicrometry). Haemodynamic values were recorded during anaesthesia with 1% halothane, fentanyl 100-mu-g kg-1 (followed by 1.5-mu-g kg-1 min-1) and then after the addition of verapamil 250-mu-g kg-1 over 30 min (followed by 60-mu-g kg-1 min-1). At each stage 67% nitrous oxide was added and recordings obtained before and during its administration. The addition of verapamil during fentanyl anaesthesia caused a moderate depression of global haemodynamics. Only little dysfunction of the apical region (9.5 +/- 2.4% post-systolic shortening) was noted. The addition of nitrous oxide caused a small amount of additional depression without significant regional dysfunction.