Abstract
The effect of normovolemic hemodilution (HD) on cerebral ischemia after the middle cerebral artery (MCA) occlusion was studied.
Thirteen adult cats (HD group; 5, control group; 8) were used. Systemic artrial pressure (SAP) and PeCO2 were continuously monitored and subsequently the MCA occlusion was made by transorbital approach. CBF was measured by hydrogen clearance method. Electroencephalogram (EEG) was monitored at the center of ischemic lesion. Pial artery pressure (PAP) at the same part was continuously recorded non-occlusively by a micropressure recording device (Model 900, W-P Instruments, Inc. U.S.A.). In HD group, low molecular dextran was given normovolemically from 10 minutes after ischemia, to lower hematocrit to 24%. The spectral power of the EEG was calculated by summing the Fourier coefficients covering the frequency ranging from 2 to 12 Hz.
No significant difference in SAP and PAP was observed between two groups throughout experiments. On the other hand, the CBF in HD group was significantly higher than in control group after 90 minutes. Upstream resistance ((SAP-PAP) /CBF) showed significantly lower in HD group than in control group. Furthermore, downstream resistance (PAP/CBF) showed significantly lower in HD group than in control group at the point of 180 minutes. There was no significant difference in the spectral power of EEG between two groups after ischemia.
These results suggest that hemodilution can improve CBF and decrease the vascular resistance of collateral circulation, but it might have insufficient effect on improvement of cerebral function.
