[Technics, value and limitations of hemodilution in extracorporeal circulation]

Hemodilution during E.C.C. is into use for more than 15 years. Its interest is obvious (blood economy, beneficient action on viscosity, prevention of "sludging"), but opinions are different concerning the best level of hemodiultion. The authors defend the notion of a moderate dilution (hematocrit larger than or equal to 25 p. 100) required to maintain a high perfusion pressure. For atherosclerotic patients, they describe the hemodilution technics tried on more than 4,000 cases since 1964. The advantages of hemodilution concern on one hand the diminution or the disparition of drawbacks and complications due to the obtainment and to the administration of homologous blood and on the other hand the beneficient intrinsical effects of the blood dilution on the tissular perfusion. In convenients are those due to changes in the concentration of sodium, chlore and specially potassium which may be responsible of serious cardiac arrythmias. Because of increasing difficulties concerning the use of homologous blood (obtaining difficulties and complications relative to its use), the authors consider the utilization of autologous blood taken off before the operation on the patient and freezed.