Cerebral blood flow velocity during isovolemic hemodilution and subsequent autologous blood retransfusion.
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In 11 volunteers 20 ml x kg(-1) blood was withdrawn over 30 min and simultaneously replaced with HES 10%.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An average of 1570 total blood was withdrawn which resulted in a decrease in Hb from 14.5 mg x dl(-1) to 10.3 mg x dl(-1); Hc (and CaO2) decreased from 41.8% (19.8 ml x dl(-1)) to 29.6% (14.2 ml x dl(-1);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.
Mühling
J
J
Department of Anaesthesiology and Intensive Care Medicine, Justus-Liebig-University, Giessen, Germany.
Dehne
M G
MG
Sablotzki
A
A
Hempelmann
G
G
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
D006454:Hemoglobins; D006895:Hydroxyethyl Starch Derivatives; D010952:Plasma Substitutes; D002245:Carbon Dioxide; D010100:Oxygen