title: Effects of chronic isovolaemic haemodilution on regional cerebral blood flow in conscious rats.
abstract: OBJECTIVE
  Acute isovolaemic haemodilution increases local and mean cerebral blood flow. It is not known whether a single haemodilution has a short-term effect only or whether it affects cerebral perfusion over a longer time period. In the present study, local and mean cerebral blood flow were determined in conscious rats after a 4, 24 and 48 h period following one-time haemodilution.
  
  
  METHODS
  Thirty-six rats were randomized to three untreated sham groups and three groups of haemodilution (4, 24 or 48 h, n = 6 for each group). Isovolaemic haemodilution with albumin 5% aimed to a target haematocrit of 0.2. Local cerebral blood flow was measured in 38 brain regions by the iodo-[14C]antipyrine method in conscious normothermic rats.
  
  
  RESULTS
  Isovolaemic haemodilution reduced haematocrit from 0.44 to 0.20. During the following 24 and 48 h periods, haematocrit remained low (0.22 and 0.21). Mean cerebral blood flow was similar in untreated sham groups (88 +/- 12 after 4 h, 92 +/- 11 after 24 h, 96 +/- 10 mL 100 g(-1) min(-1) after 48 h). Haemodilution increased mean cerebral blood flow after 4h (184 +/- 11 mL 100 g(-1) min(-1)), after 24h (153 +/- 13 mL 100 g(-1) min(-1)) and 48h (149 +/- 15 mL 100 g(-1) min(-1)) (P < or = 0.05). Local cerebral blood flow increased in all 38 structures after 4h haemodilution but decreased with time in six of 38 brain structures after 24h and in 15 regions after 48 h (P < or = 0.05).
  
  
  CONCLUSIONS
  A single one-time haemodilution increased mean cerebral blood flow for 2 days. However, local adaptation of cerebral blood flow to a chronic low haematocrit occurred but was heterogeneous within the brain.
authors.affiliation: Faculty of Clinical Medicine Mannheim, Department of Anesthesiology and Critical Care Medicine, University of Heidelberg, Germany. thomas.frietsch@urz.uni-heidelberg.de
authors.forename: T
authors.initials: T
authors.lastname: Frietsch
authors.forename: C
authors.initials: C
authors.lastname: Lenz
authors.forename: W
authors.initials: W
authors.lastname: Kuschinsky
authors.forename: K E
authors.initials: KE
authors.lastname: Waschke
mesh_terms: D000818:Animals; D000983:Antipyrine / Q000031:analogs & derivatives*; D001345:Autoradiography; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006400:Hematocrit; D006438:Hemodilution / Q000009:adverse effects*; D006863:Hydrogen-Ion Concentration; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001786:Blood Glucose; D000983:Antipyrine; C008135:iodoantipyrine