A method for evaluation of blood substitutes in the conscious animal

Physiological evaluation of new and potential blood replacement agents has not kept pace with the development of such agents. Current procedures involve partial or total blood replacement in the anesthetized animal. This introduces the variable of anesthesia and eliminates the ability to observe behavior changes during blood replacement. Clinically, many patients receive blood or will receive artificial agents while sedated or under anesthesia, whereas others will be conscious. It is essential that evaluative studies be performed on the awake animal using procedures that are nontraumatic and nonrestrictive. A technique for isovolumic exchange perfusion utilizing an indwelling, heparin-coated, double-lumen catheter in the right atrium of a conscious rat is described. This animal model system permits continuous pre- and postperfusion monitoring. Nearly total blood replacement with perfluorochemical blood substitutes causes no discernable discomfort or adverse reactions in the animal. Such animals thrive and replace missing hematologic components in 1-3 wk. The technique described can, with minimal modification, be used for isovolumic exchange perfusion of larger animals.