Hospital and ambulance officials have raised concerns after a dance party where thousands of revellers, many intoxicated, danced on polished concrete floors slippery with paint.
Around 5000 people attended the party at Dunedin's Forsyth Barr stadium which was promoted as an official world record attempt for the title of world's largest paint fight.
St John said it treated around 35 people at the Illuminate Paint Party on Wednesday night, sending 11 to hospital by ambulance.
"Nobody that went to hospital was sober," St John Dunedin operations team manager Doug Third said.
Some of those at the event were grossly intoxicated and "and not able to look after their own airways," he said.
Also "the polished concrete floor became extremely slippery with the paint on it".
Quite a few people slipped over on wet paint, striking their heads on the floor.
"There was an alarming number of people with bangs to the head and knocked out," Third said.
"When you drink and fall you don't put your arms out, you land on your head."
Much of the problems could have been avoided, he said. High levels of intoxication at the event contributed to the heavy workload for St John and the Dunedin Hospital emergency department.
Another problem was the low temperature, which had been only 4 degrees Celsius around 10pm and people were not wearing much clothing.
One person had an asthma attack, which could be triggered by the cold. Another broke a finger in a fall.
Medical officers of health Dr Marion Poore and Dr Keith Reid wrote a letter to the Otago Daily Times saying first-hand reports were that many of those at the party had been drinking beforehand.
Wednesday had been the busiest day in recent history for the emergency department at Dunedin Hospital, with 160 patients needing urgent medical treatment
''Included in this exceptional workload were over 20 alcohol and injury presentations - one an intoxicated 16-year-old - that might be linked to the event," the letter said.
"Once again the combination of alcohol and large numbers of young people has resulted in significant risks to individuals and our taxpayer-subsidised emergency services were placed under considerable strain."
""It's very difficult, of course, if people arrive at an event already having drunk a large amount of alcohol. That adds to the complexity but further emphasises the importance of planning," Poore told Fairfax Media.
"People managing the event need to be able to recognise when that's happening and have processes in place to prevent things becoming worse," she said.
"Where people do end up being injured and hurt you have a responsibility to review processes and procedures and make sure everything is being done appropriately."
Efforts to contact event organiser Jamie Templeton were unsuccessful.
The event was advertised as part of Otago University's Re-Orientation programme to mark the start of the second semester.
Otago University Students' Association communications and events manager Dan Hendra said the association had excellent health and safety systems.
"Due to concerns from last year we acted as an adviser to the out of town promoter and provider of some of the health and safety services for the (Illuminate) event."
The association shared some of the Southern District Health Board's concerns and hoped to work with the board at a debrief.
Event director Jamie Templeton said no one who was intoxicated had been allowed into the venue.
Part of the problem with preloading - drinking before going into an event - was that some people were drinking quickly as they walked up to the door.
"When they present themselves to the door they seem okay, but then 20 minutes later all that alcohol they have drunk kicks in," Templeton said.
About $10,000 had been spent on security and medical services for the Dunedin event. More than 50 security staff were at the event, with another 200 people there to support party-goers.
Organisers had noticed the slippery floor and were considering ways to reduce risk, possibly by adding grit, he said.