CIRCULATORY RESPONSES OF THE DOG TO ACUTE ISOVOLUMIC ANEMIA IN THE PRESENCE OF HIGH-GRADE ADRENERGIC BETA-RECEPTOR BLOCKADE

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 52  (3) , 337-341
Abstract
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[partial pressure]O2 by 1.2 kPa [kilopascal]. 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.