Most patients in the cardiac intensive care unit at Boston Children’s Hospital are recovering from heart surgery. At any moment, their blood pressure could plummet, their tiny hearts stop beating.

The doctors there have struggled to predict which child was likely to take a sudden turn for the worse. They had to choose from among a half-dozen monitors for the most revealing information. And after a crisis, they could not look back at patient data­ to see what might have led to it, said Dr. Melvin C. Almodovar, the unit’s medical director.