There's not a gurney anywhere in the world big enough to roll the Oregon Zoo's next patient into surgery.

So they have trained him to walk in, lie down, and submit to a needle being stuck in his ear.

Oregon Zoo

Tusko, an Asian bull elephant.

Slideshow: Tusko the elephant

The patient is Tusko, a 37-year-old asian elephant with a broken and chronically infected tusk. The infections have persisted so long, zoo officials have decided they must remove it in a risky surgery.

VIDEO: Watch Tusko

An elephant cage will serve as the operating room and a giant waterbed as the surgical table.

For weeks Tusko has been trained every morning to lie down on a water bed so large and durable it can hold his 13,000 pound frame.

"He's astonishingly well trained. He is a very very smart elephant," says zoo veterinarian Mitch Finnegan. "He figured out what we were trying to get him to do very quickly."

Tusko's cooperation is the linchpin to the operation which will involve a dozen people.

Finnegan says, "If he doesn't want to do it, it's not going to happen."

Just as important will be Tusko's physical reaction to the anesthetic. If it produces heart or breathing problems, Finnegan says there is no way to administer C.P.R. "Nobody," he says, "can compress his chest hard enough to get his heart going."

Of equal concern to veterinarians is Tusko's recovery immediately after the surgery.

Says Finnegan, "You're worried they're going to have a nerve injury or a muscle injury that will prevent them from getting up."

The last elephant surgery at the Oregon Zoo ended tragically. Belle, the famous mother of Packy, had to be euthanized when she could not stand after the surgery was over.

"We don't have a lot of options," says Finnegan, "if Tusko cannot get up on his own."

Anesthesiologists will monitor Tusko's ability to breathe and will likely need to give additional doses to keep him asleep during the four hour surgery on Saturday.

Finnegan says, "The closer we get to it the more nervous I get."