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Haemodynamic changes in pre and post ischaemia following simulated embolic stroke of middle cerebral artery occlusion
Abstract:
The effects of middle cerebral artery (MCA) occlusion (15, 30, 60 min) and recirculation of cerebral blood flow (CBF) were studied in 18 rabbits. The change of cortical oxygen tension (CoPo2) accompanying MCA occlusion was also recorded in 12 rabbits and was compared with the results of CBF recording. CBF and CoPo2 immediately decreased to a minimal level following MCA occlusion and partially improved in the first 5 min of occlusion. CBF and CoPo2 values in the first 5 min following occlusion were significantly higher than the minimal values. The degree of CBF and CoPo2 recovery in the first 5 min of occlusion had a statistically significant correlation with the minimal values. It was postulated that local tissue acidosis due to ischaemia was responsible for this recovery in the early occlusive phase. CBF and CoPo2 became relatively stable after 5 min of occlusion. The results suggest that following embolic occlusion, the degree of recovery of CBF following its initial depression is one of the pathophysiological mechanisms that differentiate between TIAs and stroke. Postischaemic hyperperfusion was observed in all cases after 15 to 60 min of occlusion. The duration of postischaemic hyperperfusion did not correlate with the CBF value just before reperfusion. However, the magnitude of postischaemic hyperperfusion had a significant correlation with the depression of the CBF value just before reperfusion. It could be concluded from our results that the magnitude of postischaemic hyperperfusion represented the severity of ischaemia, at least up to 60 min of occlusion.
Insights
Cerebral blood flow (CBF) recovery after middle cerebral artery (MCA) occlusion in rabbits may distinguish transient ischemic attacks (TIAs) from stroke. Post-ischemic hyperperfusion magnitude indicates ischemia severity.
Area of Science:
- Neuroscience
- Cerebrovascular Research
- Ischemia Pathophysiology
Background:
- Middle cerebral artery (MCA) occlusion is a model for studying ischemic stroke.
- Understanding cerebral blood flow (CBF) dynamics during and after ischemia is crucial for differentiating transient ischemic attacks (TIAs) from stroke.
- Cortical oxygen tension (CoPo2) changes reflect CBF alterations during ischemic events.
Purpose of the Study:
- To investigate the effects of MCA occlusion and reperfusion on CBF and CoPo2 in rabbits.
- To determine if early CBF recovery patterns can differentiate between transient and permanent ischemic events.
- To correlate post-ischemic hyperperfusion with the severity of cerebral ischemia.
Main Methods:
- 18 rabbits underwent MCA occlusion for 15, 30, or 60 minutes, with subsequent reperfusion.
- CBF was measured during occlusion and reperfusion.
- CoPo2 was recorded in 12 rabbits during MCA occlusion and compared with CBF data.
Main Results:
- CBF and CoPo2 initially decreased sharply upon MCA occlusion, with partial recovery within the first 5 minutes.
- Early CBF and CoPo2 recovery correlated significantly with their minimal values, potentially due to local tissue acidosis.
- Post-ischemic hyperperfusion was observed in all cases, with its magnitude correlating significantly with the preceding CBF depression, indicating ischemia severity.
Conclusions:
- Early CBF recovery following initial depression is a potential differentiator between TIAs and stroke.
- The magnitude of post-ischemic hyperperfusion serves as an indicator of ischemic severity up to 60 minutes of occlusion.
- These findings contribute to understanding the pathophysiology of cerebral ischemia and its clinical manifestations.