Hypothermia for Acute Brain Damage pp 200-203 | Cite as
Hypothermia Prolongs the Viability of Ischemic Brain Tissue Due to Neuroprotection Linked to Redistribution of Oxygen in Brain: Positron Emission Tomography Study of the Critical First 6h After Stroke in Pigs
Abstract
The objective of this study was to verify how 32°C hypothermia reduces the energy metabolism to a level that is commensurate with the prevailing blood flow and hence allows adequate distribution of oxygen to the entire brain tissue using positron emission tomography (PET) in pigs. The hypothermia reduced cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) to 50% of the baseline in 3 and 5 h, respectively. The oxygen extraction fraction (OEF) was significantly elevated to 140% of the baseline in 3h, indicating a reduction of the driving pressure of oxygen delivery in response to the reduced metabolic need, and then gradually returned to the level of the baseline. Cerebral metabolic rate of glucose (CMRglc) decreased to 75% of the baseline at 6 h of hypothermia in response to the lowered metabolism for maintenance of cellular integrity. Cerebral blood volume (CBV) decreased slightly at 3 h and to 72% of the baseline at 6 h of hypothermia. In the stroke model, the hypothermia following reperfusion decreased significantly the volume of infarction even in severe ischemia, whereas the reperfusion alone did not decrease the volume in severe ischemia. Thus, 32°C hypothermia prolongs the therapeutic time window even in severe ischemia by reducing base CMRO2, i.e., the neuroprotection linked to redistribution of oxygen in brain.
Key words
Hypothermia Ischemia Cerebral blood flow Cerebral metabolic rate of oxygen Oxygen extraction fractionPreview
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References
- 1.Busto R, Globus MY, Dietrich WD, et al (1989) Effect of mild hypothermia on ischemiainduced release of neurotransmitters and free fatty acids in rat brain. Stroke 20(7):904–910PubMedCrossRefGoogle Scholar
- 2.Sessler DI (1995) Deliberate mild hypothermia. J Neurosurg Anesthesiol 7(1):38–46PubMedCrossRefGoogle Scholar
- 3.Reith J, Jorgensen HS, Pedersen PM, et al (1996) Body temperature in acute stroke: relation to stroke severity, infarct size, mortality, and outcome. Lancet 347(8999): 422–425PubMedCrossRefGoogle Scholar
- 4.Sakoh M, Ostergaard L, Rohl L, et al (2000) Relationship between residual cerebral blood flow and oxygen metabolism as predictive of ischemic tissue viability: sequential multitracer positron emission tomography scanning of middle cerebral artery occlusion during the critical first 6h after stroke in pigs. J Neurosurg 93(4):647–657PubMedCrossRefGoogle Scholar
- 5.Ueda T, Sakaki S, Yuh WT, et al (1999) Outcome in acute stroke with successful intra-arterial thrombolysis and predictive value of initial single-photon emission-computed tomography. J Cereb Blood Flow Metab 19(1):99–108PubMedCrossRefGoogle Scholar
- 6.Sakoh M, Gjedde A (2003) Neuroprotection in hypothermia linked to redistribution of oxygen in brain. Am J Physiol Heart Circ Physiol 285:H17–H25PubMedGoogle Scholar
- 7.Vafaee MS, Gjedde A (2000) Model of blood-brain transfer of oxygen explains nonlinear flowmetabolism coupling during stimulation of visual cortex. J Cereb Blood Flow Metab 20(4): 747–754PubMedCrossRefGoogle Scholar
- 8.Baron JC, Bousser MG, Rey A, et al (1981) Reversal of focal “misery-perfusion syndrome” by extra-intracranial arterial bypass in hemodynamic cerebral ischemia. A case study with 15O positron emission tomography. Stroke 12(4):454–459PubMedCrossRefGoogle Scholar
- 9.Sakoh M, Rohl L, Gyldensted C, et al (2000) Cerebral blood flow and blood volume measured by magnetic resonance imaging bolus tracking after acute stroke in pigs: comparison with [15O]H2O positron emission tomography. Stroke 31:1958–1964PubMedCrossRefGoogle Scholar
- 10.Nemoto EM, Klementavicius R, Melick JA, et al (1996) Suppression of cerebral metabolic rate for oxygen (CMRO2) by mild hypothermia compared with thiopental. J Neurosurg Anesthesiol 8(1):52–59PubMedCrossRefGoogle Scholar