Intracerebral monitoring in comatose patients treated with hypothermia after a cardiac arrest

Induced mild hypothermia (32-34 degrees C) has proven to reduce ischemic brain injury and improve outcome after a cardiac arrest (CA). The aim of this investigation was to study the occurrence of increased intracranial pressure (ICP) and neurochemical metabolic changes indicating cerebral ischemia, after CA and cardiopulmonary resuscitation (CPR), when induced hypothermia was applied. ICP, brain chemistry and brain temperature were monitored during induced hypothermia and re-warming in four adult unconscious patients with restoration of spontaneous circulation after CA and CPR. ICP was occasionally above 20 mmHg. Neurochemical changes indicating cerebral ischemia (increased lactate/pyruvate ratio) and excitoxicity (increased glutamate) were found after CA, and signs of ischemia were also observed during the re-warming phase. A biphasic increase in glycerol was seen, which may have been a result of both membrane degradation and overspill from the general circulation. Intracerebral microdialysis and ICP monitoring may be used in selected patients not requiring anticoagulants and PCI to obtain information regarding the common disturbances of intracranial dynamics after CA. The results of this study underline the importance of inducing hypothermia quickly after CA and emphasize the need for developing tools for guidance of the re-warming.