WASHINGTON — Nikita, a 308-pound Amur tiger, was blissfully gassed out on a gurney at the National Zoo. On Saturday morning, as the orange, black and white feline lay on her side, her tongue dangling out, some 15 zoo staffers fearlessly hovered.

They opened her mouth, checked her heart rate, and, crucially, monitored for the slightest signs of muscle twitches and the long-shot chance that she’d suddenly wake.

Everyone knew the stakes. It would be bad, very bad, if Nikita woke up in this moment, in this very small room. The 6-year-old was getting a root canal.

Then, Barron Hall, a Northern Virginia-based, board-certified animal dentist, did what no other sane human would do to a sleeping tiger. He jammed a needle into her upper left canine tooth. Near the top. Near the gums. He kept doing this. Over and over.

But this was his job — digging a hole, irrigating the tooth’s precious insides, and restoring it — and he’s one of animal dentistry’s best. (He has worked on Secret Service dogs and more than 50 tigers.) And Nikita deserved the best. She’s part of the Amur tiger subspecies, an endangered population that lives mostly near the Amur River in Siberia. Poaching and habitat loss have reduced their numbers dangerously. As few as 360 are left, according to the National Zoo, but conservation efforts in Russia promoted by President Vladimir Putin have helped slow down the decline.

Fear not, Nikita does not hail from an Internet troll farm. And she’s no spy.

Hopefully, she’s a breeder.

Nikita was born at the Bronx Zoo in New York in 2012 and came to Washington in November 2018 so she could commune with the National Zoo’s other Amur tiger, an 11-year-old named Pavel. He arrived at the National Zoo in the fall of 2017 from Lincoln Park Zoo in Chicago. For the National Zoo, Pavel was a huge prize: He was the first of his endangered subspecies to be exhibited here since 1948.

The zoo’s wish is that Nikita and Pavel produce at least one litter.

“With the cats, however many they have is awesome,” said Craig Saffoe, the zoo’s curator of the Great Cats. “We’d love to get a breeding at bare minimum.”

But before Nikita and Pavel could begin their courtship, she needed that root canal.

As Hall, the dentist, began the procedure Saturday morning, he explained the root problem. Since Nikita fractured the crown of her tooth at some point in the past several months, bacteria had wormed their way into the tooth’s exposed cavity — the “pulp” — which contains blood vessels and nerves.

Without medical intervention, the bacteria would continue festering. The pus and necrotic tissue, left to stay, would put Nikita in endless pain. “She would suffer in silence. That’s what most animals do,” Hall said.

Finally, the drilling, the jamming, the digging, it was all over, mercifully. He’d cleaned her tooth out and filled it in. Cosmetically, Nikita looked brand new.