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Effect of haemodilution on experimental cerebral ischaemia
K Yamashita1, S Kobayashi, S Yamaguchi
1Third Division of Internal Medicine, Shimane Medical University, Japan.
Insights
Normovolaemic haemodilution (HD) improved regional cerebral blood flow (rCBF) in cats with middle cerebral artery occlusion (MCA). This blood flow enhancement was linked to reduced haematocrit (Ht) and improved microcirculation.
Area of Science:
- Neuroscience
- Cerebrovascular Research
- Experimental Surgery
Background:
- Cerebral ischemia following middle cerebral artery occlusion (MCA) poses significant challenges in understanding and treating brain injury.
- Normovolaemic haemodilution (HD) is a potential therapeutic strategy, but its precise effects on cerebral hemodynamics and microcirculation require further elucidation.
Purpose of the Study:
- To investigate the impact of normovolaemic haemodilution (HD) on regional cerebral blood flow (rCBF) and microvascular resistance in a feline model of middle cerebral artery occlusion (MCA).
- To assess the relationship between haematocrit (Ht) and rCBF under conditions of induced cerebral ischemia and HD.
Main Methods:
- Adult cats underwent middle cerebral artery occlusion (MCA) and were divided into HD and control groups.
- Regional cerebral blood flow (rCBF) was measured using hydrogen clearance, systemic arterial pressure (SAP), pial artery pressure (PAP), and electroencephalogram (EEG) were monitored.
- In the HD group, low-molecular-weight dextran was administered to reduce haematocrit (Ht) to 24%.
Main Results:
- Haemodilution significantly increased rCBF in the ischemic region compared to the control group after 90 minutes.
- Upstream and downstream microvascular resistance were significantly reduced in the HD group.
- A significant correlation was observed between haematocrit (Ht) and rCBF in both groups.
Conclusions:
- Normovolaemic haemodilution effectively improves regional cerebral blood flow (rCBF) in ischemic conditions by reducing haematocrit (Ht) and enhancing collateral microcirculation.
- While HD improves cerebral hemodynamics, its direct impact on improving overall cerebral function requires further investigation.
Abstract:
The effect of normovolaemic haemodilution (HD) on cerebral ischaemia after middle cerebral artery occlusion (MCA) was studied. Thirteen adult cats (HD group, 5; control group, 8) were used. Systemic arterial pressure (SAP) was monitored continuously. MCA occlusion was produced by a transorbital approach. Regional cerebral blood flow (rCBF) in the ectosylvian region was measured by a hydrogen clearance method. The electroencephalogram (EEG) was monitored, and spectral power of the EEG was calculated. Pial artery pressure (PAP) in the ectosylvian region was continuously recorded non-occlusively by a micropressure recording device. In the HD group, low-molecular-weight dextran was given normovolaemically from 10 minutes after ischaemia to lower the haematocrit (Ht) to 24%. The rCBF values in the HD group were significantly higher than in the control group after 90 minutes. Upstream resistance [(SAP-PAP)/rCBF] was significantly lower in the HD group than in the control group. Furthermore, downstream resistance (PAP/rCBF) was significantly lower in the HD group than in the control group at the 180-minute point. There was no significant difference between the two groups in the spectral power of the EEG during ischaemia. The Ht was significantly correlated with rCBF in both groups. These results indicate that haemodilution can improve rCBF by lowering the Ht and improving the microcirculation of collateral vessels via pial anastomoses, although it might have insufficient effect on improvement of cerebral function.