The hospital had already stabilised the patient, so the transfer was "quite straightforward", but something of this nature was always "challenging" for medical teams, he said.
"It really was a team effort."
The helicopter was equipped with ventilators and other medical items to ensure the patient's breathing remained stable, he said.
Rescue helicopter crews have seen a large number of severe injuries, so a single amputee situation was "not unusual", he said.
Brettkelly said he had heard that the man was taken to Whakatāne Hospital by a car, which actually passed the ambulance on the way to the scene.
A St John spokeswoman said they had sent one ambulance and a helicopter to the scene and one person was taken to Waikato Hospital in a critical condition.
The man was now stable in the hospital's High Dependency Unit, a Waikato District Health Board spokeswoman said.
Waikato Hospital had dealt with similar incidents before.
In 2009, a King Country meatworker saw his hand flapping around after nearly cutting it off with a bandsaw. Surgeons at Waikato Hospital worked for 13 hours to reattach the worker's partially amputated left wrist.
Yesterday's assault was being investigated by police.
Details including whether the victim was known to his attacker, the circumstances surrounding the incident or the weapon used were not available, as inquiries were ongoing, a police spokeswoman said.
There did not appear to be any risk to members of the public, she said.
Police were appealing for witnesses to the assault or for anyone who saw a black Great Wall ute in the Taneatua or Ruatoki area on Sunday afternoon to contact them.
