Neuroprotective effect of mild hypothermia in the temporary brain ischemia in cats

Abstract

-Objective: to evaluate the neuroprotective effect of mild hypothermia during temporary focal ischemia in cats. Method: 20 cats underwent middle cerebral artery 60 minutes occlusion and 24 hours reperfusion: 10 under normothermia and 10 under mild hypothermia (32º c). Brain coronal sections 2mm thick were stained with 2,3,5-triphenyltetrazolium hydrochloride, photographed and evaluated with software for volume calculation. Results: cortical ischemia was found in 7 and basal ganglia ischemia in 8 animals of group 1 and in both regions in 5 animals of group 2 (no difference: p=0.6499 for cortical; p=0.3498 for basal ganglia). No ischemia was found in 5 animals of group 2 and in none of group 1 (significant difference, p=0.0325). the infarct volume was greater in group 1 than 2 (p=0.0433). Conclusion: Mild hypothermia did not interfere with location of ischemia, but it was effective for reducing the infarct volume.Key words: cats, focal cerebral ischemia, mild hypothermia, neuroprotection.Efeito neuroprotetor da hipotermia leve na isquemia cerebral focal temporária em gatos resuMo -Objetivo: Avaliar o efeito neuroprotetor da hipotermia leve na isquemia cerebral focal temporária em gatos. Método: oclusão da artéria cerebral média durante 60 minutos e 24 horas de reperfusão em 10 gatos sob normotermia e 10 sob hipotermia leve (32º c). secções cerebrais coronais de 2 mm coradas com 2,3,5-cloreto de trifeniltetrazolio, fotografadas e cálculos volumétricos (hemisférios/áreas isquêmi-cas) com programa específico. Resultados: Isquemia cortical em 7 e nos gânglios da base em 8 animais do grupo 1 e em ambas as regiões em 5 animais do grupo 2 (sem diferença: p=0,6499 cortical; p=0,3498 gân-glios da base). cinco animais do grupo 2 e nenhum do grupo 1 não apresentaram isquemia (diferença significante, p=0,0325). o volume do infarto foi maior no grupo 1 (p=0,0433). Conclusão: Hipotermia leve não interferiu com a localização da isquemia mas foi eficaz para reduzir o volume do infarto.PAlAvrAs-cHAve: gatos, isquemia cerebral focal, hipotermia leve, neuroproteção. Dr. Benedicto Oscar Colli -Departamento de Cirurgia / HCFMRP -Campus Universitário USP -14048-900 Ribeirão Preto SP -Brasil. E-mail: bocolli@fmrp.usp.brBrain ischemia is common found in arterial vasospasm secondary to subarachnoid hemorrhage, by brain injury and during temporary occlusion of arteries during neurovascular procedures. despite attempts of using many strategies, the results of treatment for cerebral stroke are not ever satisfactory. the severity of brain lesion depends on the duration of ischemia, on the vessel occluded and on collateral circulation. several studies aiming better understanding of the ischemia/reperfusion pathophysiology and the improvement of brain protection in these phenomena have been done. In human being, these studies are generally clinical evaluations and image examinations that not allow detection of early cellular phenomena secondary to ischemia/reperfusion. experimental models have the advantage of better control of biolog...

Protection in Animal Models of Brain and Spinal Cord Injury with Mild to Moderate Hypothermia

“…This model therefore leads to a focal ischemic insult, followed by reperfusion injury affecting neuronal populations in specific arterial territories. In contrast to the limited and inconsistent beneficial results seen with permanent MCA occlusion, moderate hypothermia has been shown to be protective in several models of transient MCA occlusion when initiated immediately (Ridenour et al, 1992;Zhang et al, 1993;Huh et al, 2000;Nakano et al, 2007) or in a delayed fashion after occlusion (Karibe et al, 1994;Maier et al, 1998;Corbett et al, 2000). Morikawa et al (1992) demonstrated that selective brain hypothermia (308C) during a period of 2 h of reversible MCA occlusion reduced infarct volume.…”

Protocol to the induction of loco-regional mild hypothermia for temporay clipping in the surgery of the middle cerebral artery aneurysm

“…Even more, while neuroprotection by deep hypothermia can be explained by a decrease in cerebral blood flow and metabolic demand for oxygen, this by itself cannot fully explain the equal protection that has been shown when the temperature is lowered by only a few degrees, 17 . A high degree of neuroprotection was conferred by postischemic cooling (2h) to 32ºC which is virtually equivalent to that observed with intraischemic cooling at the same level in focal cerebral ischemia4 Nakano et al have demonstrated the neuroprotective effect of mild hypothermia in the temporary brain ischemia in cats 20 . Hypothermia was induced with an ice bag over the chest/abdomen.…”

“…Over the last 20 years a large number of studies have demonstrated that mild hypothermia (31-33ºC) can have the same neuroprotective effect provided by deep hypothermia in ischemic brain 1,2,3,5,6,9,14,16,19,20,22,21,28 .…”