Circulatory responses of the dog to acute isovolumic anaemia in the presence of high-grade adrenergic beta-receptor blockade
Clarke, T.N.; Foëx, P.; Roberts, J.G.; Saner, C.A.; Bennett, M.J.
British Journal of Anaesthesia 52(3): 337-341
1980
ISSN/ISBN: 0007-0912 PMID: 7370150 Document Number: 155340
The hemodynamic responses to isovolumic anemia (dextran-for-blood exchange) were studied in 7 dogs pretreated with propranolol 20 mg/kg body weight for 3 wk. Adrenergic .beta.-receptor blockade did not prevent significant increases in heart rate (up to 19%). Cardiac output increased by .apprx. 20% while systemic vascular resistance decreased by the same proportion. O2 extraction increased from 24 to 35% and this was reflected by a decrease in mixed venous P. The modest hyperdynamic response of the circulation to hemodilution in the presence of high-grade adrenergic .beta.-receptor blockade is in sharp contrast with the large hyperdynamic response that was reported in its absence and indicates that normal compensatory mechanisms are considerably impaired.