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Graded hypotension and MCA occlusion duration: effect in transient focal ischemia
1Department of Pathology, Faculty of Medicine, University of Calgary, Alberta, Canada.
Abstract:
The first 2 h of middle cerebral artery occlusion (MCAO) are likely critical in determining the final outcome in ischemic stroke. To study this early postischemic period, male Wistar rats (n = 161) were subjected to right MCAO with closely spaced step variations in both duration of MCAO and blood pressure (BP), using the intraluminal suture technique. Quantitative neuropathology was performed at 25 coronal planes of the brain after 1-week survival. Atrophy was measured as the difference between the two hemispheres and was added to cortical and striatal necrosis to obtain total tissue loss. Damage consistently increased monotonically with increasing duration of occlusion only when infarct size was expressed as percentage of the contralateral hemisphere, but not when expressed as mm3, because of variable tissue size. The results showed that already at 1 week, the quantity of tissue loss due to resorption and transsynaptic effects approached the quantity of geographically traceable necrosis in cortex and striatum. Minimum brain damage (5%) occurred after 60 min at a BP of 80 mm Hg, with almost no cortical necrosis. Damage was extremely sensitive to hypotension and MCAO duration. At a BP of 40 mm Hg, 60 min of MCAO produced 25% damage, accelerating every 20 min during the 2-h period studied. At BP 80 mm Hg, 120 min of MCAO produced the same damage as only 80 min of MCAO at BP 60 mm Hg. At 60-, 80-, 100-, and 120-min duration of MCAO, infarct size was significantly reduced with increasing BP.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
The initial 2 hours after middle cerebral artery occlusion (MCAO) are critical for ischemic stroke outcomes. Lower blood pressure and longer MCAO duration significantly increase brain damage, even after one week.
Area of Science:
- Neuroscience
- Pathology
- Ischemic Stroke Research
Background:
- The early hours following middle cerebral artery occlusion (MCAO) are crucial in determining the extent of brain damage in ischemic stroke.
- Understanding the relationship between occlusion duration, blood pressure, and resulting brain tissue loss is vital for developing effective treatments.
Purpose of the Study:
- To investigate the quantitative neuropathology of brain damage in rats subjected to middle cerebral artery occlusion (MCAO) within the first two hours.
- To determine the impact of varying MCAO durations and blood pressure levels on infarct size and overall tissue loss after one week.
Main Methods:
- Male Wistar rats (n=161) underwent right MCAO using the intraluminal suture technique with controlled variations in occlusion duration and blood pressure.
- Quantitative neuropathology was assessed across 25 coronal brain planes after a 1-week survival period.
- Total tissue loss was calculated by combining atrophy measurements with cortical and striatal necrosis.
Main Results:
- Brain damage increased monotonically with MCAO duration when expressed as a percentage of the contralateral hemisphere.
- At 1 week, tissue loss from resorption and transsynaptic effects approached geographically traceable necrosis.
- Minimum damage (5%) occurred after 60 min MCAO at 80 mm Hg BP, with minimal cortical necrosis.
- Damage was highly sensitive to hypotension and MCAO duration; for example, 60 min MCAO at 40 mm Hg BP caused 25% damage.
Conclusions:
- Both blood pressure and MCAO duration are critical factors influencing ischemic stroke severity and long-term brain damage.
- Even short durations of MCAO combined with hypotension can lead to significant and accelerated brain tissue loss.
- Therapeutic interventions aimed at maintaining adequate blood pressure during the early phase of ischemic stroke are crucial.