title: Low hematocrit levels increase intracranial pressure in an animal model of cryogenic brain injury.
abstract: 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.
authors.affiliation: Laboratory of Medical Investigation (LIM-08/Anestesiologia), Anesthesia Department, University of São Paulo Medical School, São Paulo, Brazil.
authors.forename: Humberto K
authors.initials: HK
authors.lastname: Tango
authors.forename: André P
authors.initials: AP
authors.lastname: Schmidt
authors.forename: Nelson
authors.initials: N
authors.lastname: Mizumoto
authors.forename: Marcelo
authors.initials: M
authors.lastname: Lacava
authors.forename: Ruy J
authors.initials: RJ
authors.lastname: Cruz
authors.forename: J Ruy
authors.initials: JR
authors.lastname: Cruz
authors.forename: José O C
authors.initials: JO
authors.lastname: Auler
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D001921:Brain / Q000098:blood supply; D001930:Brain Injuries / Q000503:physiopathology*; D004195:Disease Models, Animal; D004285:Dogs; D005615:Freezing; D006400:Hematocrit; D006438:Hemodilution / Q000379:methods; D006439:Hemodynamics / Q000502:physiology; D006895:Hydroxyethyl Starch Derivatives; D019586:Intracranial Hypertension / Q000503:physiopathology*; D007427:Intracranial Pressure / Q000502:physiology; D007552:Isotonic Solutions; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011446:Prospective Studies; D012151:Resuscitation; D000077325:Ringer's Lactate
chemical_list: D006895:Hydroxyethyl Starch Derivatives; D007552:Isotonic Solutions; D000077325:Ringer's Lactate; D009638:Norepinephrine