Increased Brain Tolerance for Ischemia in Accidental Deep Hypothermia and Circulatory Arrest

Abstract

This Swiss multicenter study evaluates the long-term outcome of survivors of accidental deep hypothermia (17–28 degrees Celsius) with circulatory arrest who were rewarmed with cardiocirculatory bypass. Deep hypothermia with circulatory arrest was found in 46 of 134 patients with accidental hypothermia. In 32 patients cardiopulmonary bypass rewarming was attempted resulting in 15 long-term survivors (6 glacier-crevasse, 1 avalanche, 7 cold air, 1 cold water exposure). None of the patients suffered asphyxia and thus hypoxic brain damage before cooling down, as often occurs in avalanche or drowning. At follow-up (mean of 7 years) medical history, magnetic resonance imaging, electroencephalography and neurovascular ultrasound were obtained. MRI with volumetric measurements of the cerebral compartments was performed in 13 of the patients. At follow-up there were no hypothermia-related sequelae impairing quality of life. Neurological and neuropsychological deficits observed in the early postwarming period had fully or almost completely disappeared. One patient displayed a potentially hypothemia related cerebellar atrophy on magnetic resonance imaging with mild clinical signs. Relevant clinical abnormalities were either preexisting or due to injuries not related to hypothermia. There were no significant differences in the compartment volumes and their quotients between the 13 patients and their controls. There was a not significant increase in the CSF in the hypothermia patients (96.4+/- 23.0 ml) when compared to the controls. Our 15 patients demonstrate that accidental deep hypothermia can be survived with no or minimal cerebral impairment even with prolonged circulatory arrest. The results of this study are encouraging considering the possibilities to increase the brain tolerance for ischemia in stroke by hypothermia using global or local application of hypothermia by endovascular transarterial or tranvenous approaches. The nonsignificant trend towards an increase in CSF in the hypothermia patients is further proof that there might exist an ischemic encephalopathy in cases of hypothermia.