Mild therapeutic hypothermia after cardiac arrest: mechanisms of action and protocol development Hipotermia terapêutica em pacientes pós-parada cardiorrespiratória: mecanismos de ação e desenvolvimento de protocolo assistencial

Cardiac arrest (CA) is a medical emergency defined as sudden and unexpected cessation of vital functions, characterized by absence of heart beats, respiratory movements and unresponsiveness to stimuli.(1) Nevertheless the development of reanimation maneuvers, mortality of cardiac arrest patients remains high.(2,3) Cardiac arrest produces sudden brain blood flow cessation, causing neuronal ischemia.(4) The extension of neurological damage depends on the degree of brain tissues hypoxemia, leading to permanent damage after 5 to 10 minutes of complete blood flow cessation.(5) Persistent vegetative state is the most severe feature of the ongoing ischemia and is characterized by complete unconsciousness and irresponsiveness to stimuli, maintaining the sleep-waking cycle.(6) Between 10 to 30% of cardiac arrest survivors are estimated to progress with vegetative state.(7) The costs related to the care of these patients reach one billion dollars every year.(8) Several trials have tried to identify prognostic factors able to predict patients with increased risk of persistent vegetative state. Physical neurological examination, electroencephalogram, computed tomography, biochemical neural injury markers, somatosensorial evoked potential, all these methods have their limitations and, to a Tatiana Helena Rech1, Sílvia Regina Rios Vieira2