Ventilators aren’t the only machines in intensive care units that are in short supply. Doctors have been confronting an unexpected rise in patients with failing kidneys. In recent weeks, doctors on the front lines in intensive care units in New York and other hard-hit cities have learned that the coronavirus isn’t only a respiratory disease that has led to a crushing demand for ventilators. The disease is also shutting down some patients’ kidneys, posing yet another series of life-and-death calculations for doctors who must ferry a limited supply of specialized dialysis machines from one patient in kidney failure to the next. All the while fearing they may not be able to hook up everyone in time to save them.