1. Large-volume hemodilution was experimentally performed with a standardized reservoir arteriovenous fistula preparation in which intra- and extracorporeal volumes were kept constant. Vasopressors, buffers, hypothermia, and overinfusion were not employed.
2. Control studies with 10 ml/kg of various diluents revealed hemodynamic, volumetric, and biochemical stability of the experimental preparation.
3. Homologous blood exchange (100 ml/kg) with heart worm-free donors and recipients caused arterial hypotension, hepatic and pulmonary congestion, and depressed renal function.
4. All diluents tested produced hypotension and metabolic acidosis under the conditions of the experiment when used in amounts approximately equivalent to canine blood volumes. Ten per cent of the diluted animals expired from shock.
5. Blood pressure was initially better sustained with low molecular weight dextran, dextrose-Ringer's-albumin, and dextrose-Ringer's solutions, but the effect was short lived.
6. Cardiac outputs and total blood volumes did not change appreciably during the exchange infusions. Hematocrit changes reflected maintenance of intravascular volume. Peripheral resistance fell significantly, shortly after the onset of constant volume exchange.
7. Osmolality and oncotic activity of the diluents showed no clear-cut relationship to over-all stability of the infused animals.
8. The clinical advantages of hemodilution have been well established. Hemodynamic, volumetric, and biochemical differences between clinical perfusions and the experiments outlined herein attest to the roles of over-infusion, buffering, and hypothermia in ameliorating the experimentally observed sequelae.
9. The data suggest that the search should be continued for a more ideal blood substitute, as well as for low-prime, high-flow extra-corporeal systems.
- © 1965 American Heart Association, Inc.