Hana, a Pacific white-sided dolphin at the Vancouver Aquarium Marine Science Centre, has died despite attempts last week to save the animal's life with groundbreaking surgery.

The dolphin, which was suffering from a loop in its small intestine, died Sunday evening around 7 p.m. PT despite "heroic" efforts to save it.

"She looked up at everyone to have her last breath and her heart just stopped," said Dr. Martin Haulena, the aquarium's veterinarian, at a media briefing Monday morning.

On Thursday, an international team determined the animal was suffering from some sort of gastrointestinal illness.

As Hana's condition deteriorated Thursday evening, the experts decided to try surgery using general anesthesia, which the aquarium says has never been done before on a dolphin or whale.

Haulena described the surgery as a breakthrough in veterinary care. Such a procedure would have been considered impossible only a few years ago, and the animal would have been euthanized in the past.

"Certainly everyone's devastated, but the silver lining is that we tried harder than everyone has. We've taken a really huge giant leap in our ability to care for animals," said Haulena.

Hana underwent surgery using general anesthesia, something that had never been done before on a dolphin or whale, according to the aquarium. (Vancouver Aquarium)

The surgery was considered a success on Friday by Haulena, and there were small signs the dolphin was doing well.

But on Saturday afternoon, blood work indicated its condition was deteriorating. On Sunday, Hana was in endotoxic shock.

Haulena said the condition, with loops in the bowel blocking digestion and the flow of blood, is common in mammals and likely caused by a spontaneous event.

But the necropsy revealed Hana did have an abnormally narrow opening in the intestines that could have been a contributing factor.

It was also possible injuries sustained during Hana's rescue in 2003 could have contributed, he said.

'She looked up at everyone to have her last breath and her heart just stopped,' aquarium veterinarian Dr. Martin Haulena said about Hana when he spoke Monday at a media briefing. (CBC)

Hana, aged 21, had been in perfect health since arriving at the aquarium in 2005 from Enoshima Aquarium in Japan, where it was treated for injuries from a fixed-location fishing net off the country's east coast in 2003.

"Hana was a wonderful, fantastic, affectionate, loving animal. She was an amazing dolphin — certainly a friend to us," said Haulena.

Hana's death leaves one Pacific white-side dolphin at the aquarium — Helen, aged 27, which was rescued at the same time as Hana.

Helen is being closely monitored following the death of her companion, said staff.