title: Cerebral blood flow velocity during isovolemic hemodilution and subsequent autologous blood retransfusion.
abstract: OBJECTIVE
  To quantify the influence of hematocrit on cerebral blood flow velocity (CBFV) in healthy volunteers undergoing acute isovolemic hemodilution (HD) with hydroxyethyl starch 10% (HES) and subsequent autologous whole blood retransfusion (RT).
  
  
  METHODS
  In 11 volunteers 20 ml x kg(-1) blood was withdrawn over 30 min and simultaneously replaced with HES 10%. Thirty min later, RT was started at a constant rate over 30 min. Recorded parameters included: CBFV pulsatility-index (PI) and resistance-index (RI) of the middle cerebral artery (MCA). Blood pressure (BP), heart rate (HR), hemoglobin (Hb), hematocrit (Hc) peripheral O2-saturation (SpO2), P(ET)CO2, arterial oxygen content (CaO2) and cerebral arterial O2-transport (C(E)-DO2= CaO2 x Vm-MCA) were monitored.
  
  
  RESULTS
  An average of 1570 total blood was withdrawn which resulted in a decrease in Hb from 14.5 mg x dl(-1) to 10.3 mg x dl(-1); Hc (and CaO2) decreased from 41.8% (19.8 ml x dl(-1)) to 29.6% (14.2 ml x dl(-1); P < 0.01). Vm-MCA increased from 61.2 cm x sec(-1) to 77.3 cm x sec(-1) (P < 0.01). Following RT, Vm-MCA decreased again, but remained higher than baseline (P < 0.01). PI decreased by 13% following RT (P < 0.05). There were no changes in RI, HR, BP SpO2 and P(ET)CO2. Regression lines could be fitted between Hc and Vm-MCA, Vm-MCA and CaO2, and between Hc and C(E)DO2.
  
  
  CONCLUSIONS
  Transcranial Doppler changes in blood flow velocities correlated with the simultaneously recorded systemic Hc and CaO2 values. We found a 2% increase in CBFV for each 1% decrease in Hc and CaO2.
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, Justus-Liebig-University, Giessen, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Mühling
authors.forename: M G
authors.initials: MG
authors.lastname: Dehne
authors.forename: A
authors.initials: A
authors.lastname: Sablotzki
authors.forename: G
authors.initials: G
authors.lastname: Hempelmann
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001804:Blood Transfusion, Autologous; D001810:Blood Volume / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006400:Hematocrit; D006438:Hemodilution; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D006895:Hydroxyethyl Starch Derivatives / Q000627:therapeutic use; D010100:Oxygen / Q000097:blood; D010952:Plasma Substitutes / Q000627:therapeutic use; D011673:Pulsatile Flow / Q000502:physiology; D012044:Regression Analysis; D013990:Tidal Volume / Q000502:physiology; D017585:Ultrasonography, Doppler, Transcranial; D014655:Vascular Resistance / Q000502:physiology
chemical_list: D006454:Hemoglobins; D006895:Hydroxyethyl Starch Derivatives; D010952:Plasma Substitutes; D002245:Carbon Dioxide; D010100:Oxygen