Hawke's Bay Hospital staff are reeling after a patient tried to throttle a nurse and another patient last week.
The attacker was saved from diving out an upper-floor window by hospital staff grabbing his feet.
A hospital spokesperson said an investigation had begun into the incident and staff members were offered time off and were being supported by an occupational health and safety team.
"As part of the response to this event, a debriefing with staff has been held and an investigation has begun as part of a normal response to an event," the spokesperson said.
Staff would be involved in the investigation "and briefed over the outcomes and any actions that may be needed to be put in place to prevent an event like this happening again".
New Zealand Nurses' Organisation associate professional services manager Hilary Graham-Smith said attacks on staff were increasing.
Nurses could not predict when a patient or visitor might become agitated or violent. They were often confronted by angry family members upset at levels of treatment. "That kind of situation is happening frequently, particularly in emergency departments where people come in under the influence of alcohol and drugs. So nurses and other staff are subjected to abusive environments."
She said district health boards had responded with extra security staff "so there is somebody to call when things go badly wrong".
"It is becoming something that is experienced by everyone that works in the sector at some time or other."
Staff did not expect violence, she said.
"It is a completely unpredictable event and I don't think people are in the mindset that they are going to be attacked. They simply manage the event when it happens and it often comes as a huge shock.
"We didn't sign up for managing that stuff. We sign up for caring and providing care."
Police are investigating.