Low Hematocrit Levels Increase Intracranial Pressure in an Animal Model of Cryogenic Brain Injury

Background: Brain injury is responsible for significant morbidity and mortality in trauma patients, but controversy still exists over optimal fluid management for these patients. This study aimed to investigate the effects of acute hemodilution with hydroxyethyl starch (HES) or lactated Ringer's solution (LR) in intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in dogs submitted to a cryogenic brain injury model.

Methods: Design--Prospective laboratory animal study. Setting--Research laboratory in a teaching hospital. Subjects--Thirty-five male mongrel dogs. Interventions--Animals were enrolled to five groups: control, hemodilution with LR or HES 6% to an hematocrit target of 27% or 35%.

Results: ICP and CPP levels were measured after cryogenic brain injury. Hemodilution promotes an increment of ICP levels, which decreases CPP when hematocrit target was estimated in 27% after hemodilution. However, no differences were observed regarding crystalloid or colloid solution used for hemodilution in ICP and CPP levels.

Conclusions: Hemodilution to a low hematocrit level increases ICP and decreases CPP scores in dogs submitted to a cryogenic brain injury. These results suggest that excessive hemodilution to a hematocrit below 30% should be avoided in traumatic brain injury patients.