Selective therapeutic hypothermia: A review of invasive and noninvasive techniques / Hipotermia terapêutica seletiva: uma revisão de técnicas invasivas e não invasivas

OBJECTIVE: Therapeutic hypothermia is a promising treatment to prevent secondary neurologic injury. Clinical utility is limited by systemic complications of global hypothermia. Selective brain cooling remains a largely uninvestigated application. We review techniques of inducing selective brain cooling. METHOD: Literature review. RESULTS: Strategies of inducing selective brain cooling were divided between non-invasive and invasive techniques. Non-invasive techniques were surface cooling and cooling via the upper airway. Invasive cooling methods include transvascular and compartmental (epidural, subdural, subarachnoid and intraventricular) cooling methods to remove heat from the brain. CONCLUSION: Selective brain cooling may offer the best strategy for achieving hypothermic neuroprotection. Non-invasive strategies have proven disappointing in human trials. There is a paucity of human experiments using invasive methods of selective brain cooling. Further application of invasive cooling strategies is needed.

OBJETIVO: A hipotermia terapêutica é uma estratégia promissora para prevenção do dano neurológico secundário. Sua utilidade clínica é limitada por complicações sistêmicas da hipotermia global. Resfriamento cerebral seletivo (RCS), entretanto, permanece uma técnica pouco estudada. Revisamos aqui as diferentes técnicas de indução de RCS. MÉTODO: Revisão de literatura. RESULTADOS: As estratégias de indução de RCS foram divididas em invasivas e não-invasivas. Métodos de remoção de calor do cérebro não-invasivos incluem o resfriamento de superfície e o de vias aéreas superiores; as técnicas invasivas incluem resfriamento transvascular e compartimental (epidural, subdural, subaracnóideo e intraventricular). CONCLUSÃO: RCS pode oferecer a melhor estratégia para alcançar neuroproteção hipotérmica. Estratégias não-invasivas têm se mostrado ineficazes em estudos clínicos. Técnicas invasivas foram raramente estudadas em humanos e necessitam ser mais investigadas para tornarem-se úteis.

The Comparison of the Cerebroprotective Effects between Postischemic Systemic Hypothermia and Selective Brain Cooling in Focal Cerebral Infarction

The cerebroprotective effects of mild to moderate hypothermia(about 32degreesC) in brain ischemia have been well established. Taking into consideration of potential deleterious systemic effects of total body cooling, selective brain cooling(SBC) can be considered as an alternative mean, and recently the protective effects of SBC in focal cerebral ischemia have been reported. However, there has been no attempt to draw a comparison of antiischemic and systemic effects between systemic hypothermia(SH) and SBC. The present study investigates the effects of SH and SBC on the physiological variables, neurological outcome, and the volume of brain infarction and edema, and compares each other. In thirty adult male Sprague-Dawley rats weighing 300-400g, permanent middle cerebral artery(MCA) occlusions were performed. Five groups of animals were studied; group 1, normothermic control(n=6); group 2, systemic hypothermia for 30min(n=6); group 3, selective brain cooling for 30min(n=6); group 4, systemic hypothermia for 60min(n=6); and group 5, selective brain cooling for 60min(n=6). In the hypothermia groups, active cooling was performed 15min following MCA occlusion. During the experimental procedures, the physiological variables such as mean arterial blood pressure and blood gases were continuously monitored. Twenty-four hours following MCA occlusion, the rats were sacrificed. Eight predefined coronal sections were stained with hematoxylin-eosin and the volume of ischemic damage and edema was computed. The results are as follows: 1) There were no differences in the physiological variables between SH and SBC groups. 2) In the hypothermia groups, neurological outcome was much better(p<0.05) than that in the control. 3) The volume of ischemic damage was significantly reduced to 49.2%(p<0.05) in group 4 and 26.7%(p<0.05) in group 5, compared to group 1. 4) Ischemic brain edema was significantly attenuated in group 4(23.6%; p<0.05) and group 5(7.8%; p<0.05), compared to group 1. These results reveal that systemic hypothermia may exert more beneficial effects upon focal cerebral infarction without significant systemic complication than selective brain cooling.