Circulatory Arrest

There's a morbid saying in medicine: no one's dead until they're warm and dead. That is, a hypothermic person may have none of the usual signs we associate with life - they may be pulseless, not breathing, unresponsive, with no blood pressure - and yet, if warmed up, they may reawaken. We know this from stories of children who have fallen into icy ponds, rescued an hour later, yet who sustain little or no long-term injury.

We take advantage of this in some cardiac and neurologic surgeries, and the most extreme example is circulatory arrest. Normally when we go on bypass and the heart is stopped, the bypass machine perfuses the other organs of the body, and only the heart is ischemic. But in order to work on an empty, still heart, the surgeons must be able to put a clamp across the aorta. If the surgery involves that area of the aortic root and there is no place to put a cross-clamp, then we may do a circulatory arrest. In this case, we cool the body, sometimes even down to 18 degrees. We stop all blood flow and the surgeon has an extremely narrow window of time to create a synthetic aortic root to allow a cross-clamp. Most times, we do not do this under true circulatory arrest because the surgeons place a catheter into one of the arteries going to the brain to allow some selective perfusion. Nevertheless, other than the patient's temperature, the patient's vital signs are essentially nonexistent. But if all goes well, we warm the patient, and that brings them back to life.