Abstract
Numerous processes that contribute to neuronal death after brain ischemia/hypoxia have been identified. Among these processes, high concentrations of excitotoxic neurotransmitters, in particular glutamate, and accumulation of intracellular Ca2+ appear to be major factors. Recently, it has been demonstrated that mild hypothermia (32∼34°C) suppresses these ischemia-induced events, and protects the brain against ischemic/hypoxic injury. In the present article, the use of mild hypothermia in clinical practice, including our own experience and the United States' experience in head injury, is reviewed.
Indications for mild hypothermic therapy include head injury, cerebral infarction, vasospasm following subarachnoid hemorrhage, and ischemic injury associated with cardiopulmonary arrest. Our institution's protocol requires initiation of hypothermia within six hours after the ischemic insult. Maintenance of intravascular volume and peripheral vasodilation must be accomplished before the start of cooling. The target core body temperature is 32∼34°C and the duration is 2 to 10 days, depending upon the cerebral pathophysiology. Temperature reduction is accomplished by body surface cooling, chilled intravenous fluids, and cold gastric lavage. Brain oriented neuro-intensive care is necessary and specific neuromonitoring, such as internal jugular bulb blood temperature and oxygen saturation is useful. Blood and cerebrospinal fluid biochemistry analysis is performed. The timing of rewarming is based on computed tomographic determination of intracranial pressure. Rewarming may be accomplished over several days. Core body temperature in excess of 37°C is carefully avoided. The adverse effects of the mild hypothermia therapy have included cardiac arrhythmias, hypokalemia, hyperglycemia, coagulopathy and immuno-suppression. The management approaches to these adverse effects are described.
In conclusion, mild hypothermia appears to be effective for brain protection resuscitation. Safe and standardized methods for the clinical application of mild hypothermia have been well defined. However, the technique should be applied carefully and, for the immediate future, in conjunction with informed consent.
