Irreversible hemorrhagic shock in rats: method and critical bleeding volume

¹ Department of Surgery and Cardiovascular Research Laboratories, University of Wisconsin Medical School, Madison, Wisconsin

A procedure consisting of a combination of tail bleeding and heart puncture has allowed the controlled withdrawal of predetermined amounts of blood from rats. Within a narrow bleeding range of 3.9–4.0 vol. % body weight the mortality rate has been found to rise sharply from 20–70%. Survival or death do not seem to be associated with any significant changes in the fluid contents of the small intestine despite the marked hemorrhagic discoloration seen at autopsy. The removal of 4.1 (or more) vol. % body weight of blood results in a mortality rate of 80–85% with no deaths occurring beyond 4 hours. Observations made before and after death suggest that the rats die from irreversible hemorrhagic shock. The method is applicable to experiments involving 10–20 animals at a time.