Hypothermia helps decrease anoxic brain injury after cardiac arrest

2/20/2002

Two important articles from New England Journal of Medicine (Feb 21, 2002) will likely change ICU management of cardiac arrest patients after ACLS codes.  The two studies showed that after successful resuscitation from cardiac arrest with coma, induction of hypothermia improves neurological outcome in in-hospital and out-of -hospital arrests. 

In the first (in-patient) study from Austria, they blow cold air using a cold air blanket to aim for a core temperature of 32-34 deg C, as follows:

"Sedation was induced by the intravenous administration of midazolam (0.125 mg per kilogram of body weight per hour initially) and fentanyl (0.002 mg per kilogram per hour initially), and the doses were adjusted as needed for 32 hours for the management of mechanical ventilation. To prevent shivering, paralysis was induced by the intravenous administration of pancuronium (0.1 mg per kilogram) every 2 hours for a total of 32 hours. Intracranial pressure was not monitored.

The temperature on admission was measured with an infrared tympanic thermometer (Ototemp LighTouch, Exergen, Watertown, Mass.). Further temperature measurements were made with a bladder-temperature probe (Foley catheter). Patients randomly assigned to the normothermia group were placed on a conventional hospital bed, and normothermia was maintained. Those randomly assigned to the hypothermia group were cooled to a target temperature of 32°C to 34°C with the use of an external cooling device (TheraKool, Kinetic Concepts, Wareham, United Kingdom). This device consists of a mattress with a cover that delivers cold air over the entire body. The goal was to reach the target bladder temperature within four hours after the return of spontaneous circulation. If this goal was not achieved, ice packs were applied. The temperature was maintained at 32°C to 34°C for 24 hours from the start of cooling, followed by passive rewarming, which we expected would occur over a period of 8 hours."

In the second study from Australia, they use ice-pack, as follows:

(hypothermia is induced) by means of extensive application of ice packs around the head, neck, torso, and limbs. When the core temperature reached 33°C, the ice packs were removed, and this temperature was maintained until 12 hours after arrival at the hospital while the patient continued to be sedated and paralyzed with small doses of midazolam and vecuronium, as required, to prevent shivering that might lead to warming. Beginning at 18 hours, the patients were actively rewarmed for the next 6 hours by external warming with a heated-air blanket, with continued sedation and neuromuscular blockade to suppress shivering.

Both have improved neuro outcome.  In the perspective, the editoralist speculate that this may change post-ACLS treatment.

This is the most exciting paper I have seen in the field of anoxic brain injury in the past two decades.