Changes in Cerebral Blood Flow and Brain Tissue Oxygen Tension during Normovolemic Hemodilution in Cryogenic Brain Injury of Rabbits

Fluid replacement after hemorrhage usually results in hemodilution. Hemodilution leads to increased cerebral blood flow, which is known to be beneficial to the outcome of ischemic brain damage. However, the effect of hemodilution may be different in patients with head injuries and increased intracranial pressure (ICP). The aim of this study is to evaluate the effects of normovolemic hemodilution on cerebral blood flow (CBF), brain tissue oxygen tension (PbtO2), and severity of cryogenic brain injury, and to determine the acceptable limit of hemodilution during cryogenic brain injury. Thirty New Zealand white rabbits were anesthetized with O2-N2O-isoflurane. Cryogenic brain injury (1 cm in diameter) was produced by applying liquid nitrogen on the surface of the right parietal bone for 90 seconds. Sixty minutes after cryogenic brain injury, acute normovolemic hemodilution was induced with 10% pentastarch for 30 minutes. In group I (n=7), hemodilution was not induced. In groups II (n=7), III (n=8), and IV (n=8), the hemoglobin concentrations were adjusted to 9-10, 6-7 and 3-4 g/dL, respectively. Mean arterial