| Abstrakt: |
Cardiovascular measurements were made in groups of anaesthetized dogs at 1 and 3 hours and 2, 3, 4, 6–7 and 8–9 days after the rapid production of severe anaemia by dextran-for-blood exchange. At 1 and 3 hours after exchange the cardiac output was increased, fell to be at or close to control levels at 2 and 3 days, then rose again at 4 to 9 days after exchange. An increased percent extraction of arterial oxygen was present throughout, being greatest at the 2- to 3-day period. These mechanisms were responsible for maintaining the tissue demands for oxygen but these demands as evidenced by oxygen consumption were reduced below control levels at 1 and 3 hours after exchange, rose to control at 2 and 3 days, then increased above control at 4 to 9 days after exchange.Assays were carried out with blood from anaemic dogs at all periods for a cardiotonic agent, previously demonstrated in the blood of anaemic dogs, which induced cardiovascular changes in normal assay dogs comparable to those of the hyperkinetic circulatory state in anaemia. This material is absent from normal blood. The cardiotonic agent was present at 3 hours and at 3 to 9 days in maximal amounts. There was no cardiotonic agent detected at 1 hour and only a moderate amount was present at 2 days after exchange.Delineation of the exact role of the cardiotonic agent in the cardiovascular adjustments in anaemia requires further investigation, in particular of certain discrepancies which exist between the levels of cardiotonic agent and the circulatory changes in the anaemic animal. |
