BACKGROUND: Hemodilution is known to increase cerebral blood flow, but it is not known why it is. We tried to investigate about these question like above.

METHODS: Blood flow were checked on carotid artery after hemodilution by using electromagnetic blood flow-meter in 10 rabbits. Hemodilution was induced as 15 ml of lactated Ringers solution (LR) was infused after removing 5 ml of blood. Hemodilution was done 5 times in each rabbit. At 15 minutes after each hemodilution procedure, blood flow was checked and arterial blood gas analysis, and they compared with control data. The Sigma STAT and one way repeated measured ANOVA in Bonfferoni correction and regression analysis with DBSTAT PC application were used for statical analysis.

RESULTS: Hemoglobin concentration and hematocrit in blood according to each hemodilution step decreased. At the same time, carotid blood flow increased following hemodilution. Though PaO₂ level was not changed, CaO₂ and pH, bicarbonate, and base excess in accordance with hemodilution were decreased. Also carotid blood flow calculated as increase 2.5 ml/min whenever hematocrit decreased 1%.

CONCLUSIONS: We concluded as follow. Carotid blood flow increased to 2.5 ml/min (4.7%) whenever hematocrit decreased 1% by hemodilution. Whenever 15 ml of L/R solution was infused for acute hemodilution, carotid blood flow increased, on the contrary, hematocrit and arterial oxygen content decreased. Metabolic acidosis was induced by the large amount of L/R solution and it may be affected to carotid blood flows.