Cardiovascular stabilization after hemorrhage depends upon restitution of blood volume.

The role of late restitution of blood volume after hemorrhage in cardiovascular stabilization was examined in awake, splenectomized dogs. Cardiovascular variables were measured: at 2 hours after hemorrhage, changes were noted in cardiac output, mean arterial pressure, heart rate, stroke volume, arterial pressure, and CVP in three hemorrhage groups (p less than 0.05), and in total peripheral resistance for 15 ml/kg and 22.5 ml/kg hemorrhage groups (p less than 0.05). At 24 hours after hemorrhage, the degree of restitution of blood volume was correlated with cardiac output (p less than 0.01), stroke volume (p less than 0.02), and total peripheral resistance (p less than 0.01). No correlation was noted with heart rate, CVP, or mean arterial pressure. Blood volume restitution was correlated with degree of hemorrhage throughout the 24-hour period of investigation. Plasma protein content restitution and blood volume restitution were correlated with changes in osmolality. The results suggest thatcardiovascular stabilization after hemorrhage is a function of the degree of restitution of blood volume mediated through a shift of fluids to the interstitutium, mediated in turn by extracellular hyperosmolality.