The season ends on a cliffhanger, with Nate undergoing the high-risk surgical procedure required to save his life.

Health workers infected with the virus would have to receive approval from local panels before performing the high-risk procedures.

The more health-care workers a clinic has, or the greater the number of high-risk procedures it performs, the higher its premiums climb.

But bone-marrow transplants are painful, high-risk procedures that cost nearly $100,000.

And, costs aside, subjecting patients to high-risk surgical procedures that have little or no likelihood of affecting their health raises profound ethical questions.

Even where bills are lower, the charges have soared high enough to drive some doctors to retire, leave the state or give up high-risk procedures.

Ma authorized the high-risk procedure, and was hoping to visit China had it been successful.

Such treatments, like high-risk surgical procedures, are intended not to kill but to improve the quality of life, even though they might prove fatal.

The American Dental Association said it expects to issue its list of high-risk procedures next month.

Yet doctors might avoid doing a high-risk procedure, even if it was a patient's only chance for survival.