In those without signs of life, cardiopulmonary resuscitation (CPR) should be continued during active rewarming. For ventricular fibrillation or ventricular tachycardia, a single defibrillation should be attempted. However, people with severe hypothermia may not respond to pacing or defibrillation. It is not known if further defibrillation should be withheld until the core temperature reaches . In Europe, epinephrine is not recommended until the person's core temperature reaches , while the American Heart Association recommends up to three doses of epinephrine before a core temperature of  is reached. Once a temperature of  has been reached, normal ACLS protocols should be followed.