"It seems like a good idea, but there are so many variables," says Barco's cardiologist, Jonathan Gomberg, who, despite working with Becker and Abella at Penn, still seems uncertain about hypothermia. If a patient's heart has stopped for more than a certain length of time, is he still worth cooling? Penn's limit is an hour; much longer than that, and severe brain damage is difficult to avoid. If a patient wakes up after resuscitation and seems OK, should he be sedated again for cooling, since more sedation can also pose risks? Penn says no. The list goes on. "When the science is clear, there's one answer, and that's what you do," says Abella, now the hospital's clinical-research director. But that's not the case with hypothermia yet, so each hospital has to develop its own protocol. Even Penn cools only about 25 cardiac-arrest patients a year.