Pre, intra and post-ischemic hypothermic neuroprotection in temporary focal cerebral ischemia in rats: morphometric analysis / Neuroproteção hipotérmica pré, intra e pós-isquêmica na isquemia cerebral focal temporária em ratos: análise morfométrica

OBJECTIVE: To evaluate the neuroprotection of mild hypothermia, applied in different moments, in temporary focal cerebral ischemia in rats. METHODS: Rats was divided into Control (C), Sham (S), Ischemic-control(IC), Pre-ischemic Hypothermia (IH1), Intra-ischemic Hypothermia (IH2), and Post-ischemic Hypothermia (IH3) groups. Morphometry was performed using the KS400 software (Carl Zeiss®) in coronal sections stained by Luxol Fast Blue. Ischemic areas and volumes were obtained. RESULTS: Statistically, blue areas showed difference for C vs. IC, IC vs. IH1 and IC vs. IH2 (p=0.0001; p=0.01; p=0.03), and no difference between C vs. S, IC vs. IH3 and IH vs. IH2 (p=0.39; p=0.85; p=0.63). Red areas showed difference between C vs. IC, IC vs. IH1 and IC vs. IH2 (p=0.0001; p=0.009; p=0.03), and no difference between C vs. S, IC vs. IH3 and IH1 vs. IH2 (p=0.48; p=0.27; p=0.68). Average ischemic areas and ischemic volumes showed difference between IC vs. IH1 and IC vs. IH2 (p=0.0001 and p=0.0011), and no difference between IC vs. IH3 and IH1 vs. IH2 (p=0.57; p=0.79). CONCLUSION: Pre-ischemic and intra-ischemic hypothermia were shown to be similarly neuroprotective, but this was not true for post-ischemic hypothermia.

OBJETIVO: Avaliar a neuroproteção da hipotermia leve, aplicada em diferentes momentos, durante isquemia cerebral focal temporária em ratos. MÉTODOS: Ratos foram divididos em grupos: Controle (C), Sham (S), Controle-isquêmico (IC), Hipotermia Pré-isquêmica (IH1), Hipotermia Intra-isquêmica (IH2) e Hipotermia Pós-isquêmica (IH3). A morfometria foi realizada em secções coronais coradas por Luxol Fast Blue através do programa KS400 (Carl Zeiss®). Foram calculados áreas e volumes isquêmicos. RESULTADOS: Estatisticamente, áreas azuis demonstraram diferença entre os grupos C vs. IC, IC vs. IH1 e IC vs. IH2 (p=0,0001; p=0,01; p=0,03), e nenhuma diferença entre C vs. S, IC vs. IH3 e IH vs. IH2 (p=0,39; p=0,85; p=0,63). Áreas vermelhas demonstraram diferença entre C vs. IC, IC vs. IH1 e IC vs. IH2 (p=0,0001; p=0,009; p=0,03), e nenhuma diferença entre C vs. S, IC vs. IH3 e IH1 vs. IH2 (p=0,48; p=0,27; p=0,68). Áreas isquêmicas médias e volumes isquêmicos demonstraram diferença entre os grupos IC vs. IH1 e IC vs. IH2 (p=0,0001 and p=0,0011), e nenhuma diferença entre IC vs. IH3 and IH1 vs. IH2 (p=0,57; p=0,79). CONCLUSÃO: Hipotermias pré-isquêmica e intra-isquêmica demonstraram neuroproteção em grau semelhante, o que não ocorreu com hipotermia pós-isquêmica.

The effects of mild hypothermia on coagulation tests and haemodynamic variables in anaesthetized rabbits / Efectos de la hipotermia leve sobre las pruebas de coagulación y las variables hemodinámicas en conejos anestesiados

OBJECTIVE: Hypothermia has been associated with coagulation defects. The purpose of this experimental study was to investigate the effect of mild hypothermia on clinically used coagulation tests and on haemodynamic variables. METHODS: Νine New Zealand rabbits were subjected to mild core hypothermia by administration of general anaesthesia and exposure to room temperature of 22°C for 60 minutes. Blood samples were obtained at normothermia and mild hypothermia for measurement of prothrombin time, activated partial thromboplastin time, fibrinogen levels, platelet count and haemoglobin concentration. Hypothermic values were compared to the normothermic values. Additionally, the progressive temperature drop and haemodynamic changes (blood pressure, heart rate) were recorded. RESULTS: Core temperature decreased significantly over time changing from 39.4 ± 0.27 to 36.6 ± 0.28°C (p = 0.0001). Prothrombin time and activated partial thromboplastin time decreased at hypothermia, but the changes were not statistically significant (p = 0.203 and p = 0.109, respectively). Platelet count, fibrinogen levels and haemoglobin concentration decreased significantly (p = 0.0001, p = 0.03 and p = 0.027) but remained within normal limits. Mean arterial pressure and heart rate declined significantly over time (p = 0.0001 and p = 0.0001, respectively). CONCLUSION: The results of this study suggest that short term mild hypothermia may affect the coagulation mechanism to a clinically nonsignificant extent, while haemodynamic responses are significantly suppressed.

OBJETIVO: La hipotermia ha sido asociada con defectos de coagulación. El propósito de este estudio experimental fue investigar el efecto de la hipotermia leve sobre las pruebas de coagulación de uso clínico, así como sobre las variables hemodinámicas. MÉTODOS: Nueve conejos de Nueva Zelanda fueron sometidos a hipotermia central leve mediante la administración de anestesia general y exposición a una temperatura ambiente de 22°C durante 60 minutos. Se obtuvieron muestras de sangre en condiciones de normotermia e hipotermia leve para medir el tiempo de protrombina, el tiempo de tromboplastina parcial activada, los niveles de fibrinógeno, el conteo de plaquetas, y la concentración de hemoglobina. Se compararon los valores hipotérmicos con los valores normotérmicos. Además, se registraron la caída progresiva de la temperatura y los cambios hemodinámicos (presión sanguínea, frecuencia cardíaca). RESULTADOS: La temperatura corporal central disminuyó significativamente con el tiempo, cambiando de 39.4 ± 0.27 a 36.6 ± 0.28°C (p = 0.0001). El tiempo de protrombina y el tiempo de tromboplastina parcial activado disminuyeron en la hipotermia, pero los cambios no fueron estadísticamente significativos (p = 0.203 y p = 0.109, respectivamente). El conteo de plaquetas, los niveles de fibrinógeno y la concentración de la hemoglobina disminuyeron significativamente (p = 0.0001, p = 0.03 y p = 0.027) pero permanecieron dentro de los límites normales. La presión arterial promedio y la frecuencia cardíaca disminuyeron significativamente con el tiempo (p = 0.0001 y p = 0.0001, respectivamente). CONCLUSIÓN: Los resultados de este estudio sugieren que la hipotermia leve a corto plazo puede afectar el mecanismo de la coagulación hasta un punto clínicamente no significativo, mientras que respuestas hemodinámicas se suprimen significativamente.

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

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 (32° 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.

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 (32° C). Secções cerebrais coronais de 2 mm coradas com 2,3,5-cloreto de trifeniltetrazolio, fotografadas e cálculos volumétricos (hemisférios/áreas isquêmicas) 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 gânglios 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.