Renin response to hemorrhage in awake and anesthetized rats

Anesthetic agents have been shown to alter survival in animals subjected to hemorrhage. Since survival after hemorrhage is increased by inhibitors of the renin-angiotensin system, we asked whether anesthetic agents altered renin release during hemorrhage. We studied 33 rats which were subjected to one hour of hemorrhagic hypotension at a mean arterial pressure of 40 mm Hg. Animals were either awake or anesthetized with halothane or ketamine. Anesthesia alone did not alter plasma renin activity (PRA), whereas hemorrhage resulted in approximately a ten-fold increase in PRA in both awake and anesthetized animals. After the shed blood was returned to the animal, intravenous saralasin, an angiotensin II competitive inhibitor, produced a 21-24 mm Hg decrease in blood pressure in all animals, regardless of the severe hemorrhage is unaltered by halothane or ketamine anesthesia, that the renin-angiotensin system provides a similar amount of blood pressure support in both awake and anesthetized animals, and that the anesthetic influence on survival following severe hemorrhage does not result from anesthetic-induced alterations of the renin-angiotensin system.