EFFECT OF ISOFLURANE AND HALOTHANE ON REGIONAL CARDIAC STIFFNESS

To investigate the possibility of regional differences in cardiac stif fness which may relate to the known regional differences in systolic l eft ventricular function, seven mongrel dogs were acutely instrumented and regional cardiac stiffness was measured at both apical and basal region under two different concentrations of isoflurane, (1.08% and 1. 9%) as well as equipotent concentrations of halothane (0.9% and 1.58%) . Cardiac stiffness was determined in terms of distensibility, chamber stiffness (derived from pressure-length relationships), and an elasti c stiffness constant (derived from stress-strain relationships). Regio nal differences in cardiac stiffness were observed for all three indic es and for each anaesthetic setting except for the elastic stiffness c onstant under 1.9% of isoflurane. The data indicate that regional diff erences in cardiac stiffness exist between the apex and the base of th e heart. These regional differences do not depend on the anaesthetic a gent or its concentration and may contribute to the differences in sys tolic function.