Does cooling after out-of-hospital cardiac arrest save lives? The HACA trial was a multicenter, randomized controlled trial (RCT) that aimed to evaluate the effectiveness of therapeutic hypothermia in patients who had suffered a cardiac arrest and remained comatose. The study compared the outcomes of patients who were treated with therapeutic hypothermia (cooling to 32–34 °C for 24 h) versus those who were treated with normothermia (maintaining normal body temperature). The results showed that therapeutic hypothermia significantly improved neurologic outcomes and survival at 6 months compared to the normothermic group. The trial concluded that therapeutic hypothermia was a safe and effective intervention for improving outcomes in patients who had survived a cardiac arrest but remained comatose.