Responsiveness to different volume therapies following hemodilution and hemorrhagic shock: a comparative experimental study in rats.

UNLABELLED: Guidelines for volume replacement for acutely hemorrhaged and hemodiluted trauma patients have not been well established. PURPOSE: To evaluate the effects of acute hemodilution on mean arterial pressure (MAP), and responsiveness of acutely hemodiluted and subsequently hemorrhaged rats to different volume therapies. METHODS: 180 rats were hemodiluted to simulate hemorrhaged trauma patients with persistent bleeding after high volume replacement with isotonic solutions. Thirty hemodiluted [Anemia (ANE) group] animals received no further treatment. The remaining 150 animals were subjected to hypovolemic shock and randomized into five groups, according to the treatment option employed: Control (CTL) animals did not receive subsequent treatment after hemorrhagic hypovolemia, SAL4 animals received isotonic saline 4 mL/kg, SAL32 animals received isotonic saline 32 mL/kg, HS animals received hypertonic saline 4 mL/kg and BLD animals received re-infusion of drawn blood. RESULTS: Highest mean arterial pressure (MAP) was achieved by BLD, followed by SAL32 and HS. MAP after treatment of BLD, HS, SAL32 and ANE were higher than CTL (p=0.036). At 85 and 95 minutes of experiment, SAL4, SAL32 and HS presented the lowest hematocrit levels (p<0.01). At day 3, ANE, CTL and HS had the highest hematocrit. SAL4 and CTL groups presented the highest mortality rates. CONCLUSION: Hypertonic saline is an effective and safe initial therapy for hemodiluted rats undergoing hemorrhagic shock, with an overall outcome comparable to blood replacement or high volume isotonic saline administration.