It is understood a male patient had been sitting in the front seat of the vehicle beside the driver and an elderly man with a heart condition had been caught in the back of the ambulance when the attack unfolded on the motorway near Lower Hutt.
The ambulance driver was forced to stop at the roadside and police were called to the scene, where the alleged attacker was arrested and removed from the ambulance.
The nurse was treated at Hutt Hospital for injuries she received in the attack and was discharged the same day.
"It was a serious physical assault. After any serious incident we conduct a staff debrief with all staff involved and offer them support," Mrs Tyrer said.
"In addition, we will be carrying out a separate incident review with CapCoast and Wellington Free Ambulance. The joint review will consider the transfer arrangements [and] level of security risk assessment and controls in place."
Health, Quality and Safety Commission New Zealand would also be involved in the review, Mrs Tyrer said.
The nurse was off work recovering from her injuries and said she has had "excellent support" from Wairarapa DHB.
There had been no other "major incidents" involving patients assaulting Wairarapa Hospital staff over the past year, communications adviser Jan McLaren said.
