A teenager dying of a severe infection and blood poisoning went to a country hospital four times in 32 hours before his blood pressure and other basic readings were recorded, a coroner has heard.

Alex Braes, 18, died at Sydney’s Royal Prince Alfred Hospital in the early hours of September 22, 2017, after arriving by plane from his home town, Broken Hill.

His inquest, which began on Monday, was told the teenager died of complications arising from an infection and severe septicaemia.

But that wasn’t picked up by staff at Broken Hill Hospital until after they’d sent him home three times on September 20, when he’d reported knee pain after hearing a “popping sound”.

Except for one nurse at one presentation noting the teen’s temperature as “normal” and his pulse as “regular”, no vital signs were recorded until his fourth presentation, about 11am on September 21.

By that stage, Mr Braes was in severe pain, had a left knee and ankle that were swollen and dark, and required a wheelchair to move around.

A doctor who saw him an hour later during a rapid response said he was shocked by Mr Braes’ condition and described him “as the sickest patient he’d ever seen at Broken Hill”, the inquest was told on Monday.

A panel of experts are due to tell the inquest the small-to-non-existent opportunity to save Mr Braes’ life evaporated by the time he was sent home on Wednesday night.

Mr Braes likely had invasive grade A streptococcal, an infection that can be fast-acting, cause devastating complications such as toxic shock syndrome and sometimes develop into necrotising fasciitis or flesh-eating disease.

Even with treatment, the death rate for invasive group A streptococcal can be as high as 50 per cent, counsel assisting Kirsten Edwards said in her opening address.

But at least one on the panel of experts, former Australasian College for Emergency Medicine president Sally McCarthy, was “very critical” of the hospital’s failure to take and record the teen’s vital signs.

John Braes, who accompanied his son on each presentation, had numerous concerns about the treatment and the hospital’s later response to the death.

“We kind of sensed it wasn’t right from day dot,” he said.

“To not take a temperature, to not take blood pressure … in this day and age, it’s just so easy to do.”

The first doctor to see Mr Braes, about 3.30am on September 20, diagnosed him with a potential knee ligament injury, prescribed crutches and asked him to return in the morning for scans.

Despite being told Mr Braes didn’t play sport, the doctor “kept bringing it back to sport”, frustrating John Braes, the father told the inquest.

The inquest heard a root cause analysis wasn’t done on the episode until almost a year after his death, following lobbying of the NSW Ministry of Health by local doctors.

Hospital management then got in contact with the Braes family on the first anniversary of the teenager’s death – a “gut-wrenching” and “distasteful” occurrence in the eyes of John Braes.

The inquest will examine the treatment of Mr Braes at Broken Hill as well as the process to evacuate him to a tertiary hospital when his condition rapidly deteriorated on the afternoon of September 21.

“The ordeal endured by the family is almost unbearable, to imagine their loss is incalculable,” Ms Edwards said.

The inquest is expected to run until Friday in Broken Hill, before resuming in Sydney in August.

-AAP