Modification of cardio-vascular responses to hemorrhage by induced hyperosmolality in the rat.

Starved rats sedated with a neurolept analgesic were subjected to hemorrhagic hypotension while receiving infusions of iso-osmolar and hyperosmolar solutions. The hemorrhage model used resulted in similar residual blood volumes and hematocrits in all groups. The non-metabolizable pentose, xylose, and glucose were used to induce a state of hyperosmolality, which was absent in those animals which received iso-osmolar infusions (0.29 M xylose). After 45 mins hemorrhagic hypotension and a blood loss equal to 40% of the initial blood volume, the animals receiving the hyperosmolar infusions had a better cardiovascular status compared to those which received the iso-osmolar infusions. The cardiac outputs and stroke volumes were higher and heart rate lower in the hyperosmolar groups. Evidence of better tissue perfusion was obtained in those animals with the induced state of hyperosmolality.