dena,
Sorry to hear that your nephew is in such serious condition. There are many reasons that could explain why surgery was postponed. The major one that comes to mind is a problem in your nephew's condition that poses too great a risk to proceed with surgery.
To find out the real answer, you have to ask the doctors in charge of his care. They have made this decision and they are only people who can tell you why. When discussing this, be sure to discuss his present condition and the risk it poses for surgery. In situations like this, the risk is high, but the risk of not performing surgery is higher.
Best wishes.
Martin Cane, M.D.