New research shows less is more when it comes to using blood during heart surgery for older patients.
The surprising find will help save lives and conserve donor blood resources, one of the study's authors says.
Until now, it was thought that patients over the age of 75 benefitted from being given more blood during heart surgery.
But a new international study, including 500 New Zealanders, found using less blood for transfusion in older patients led to better outcomes.
Intensive Care Specialist at Auckland City Hospital, Dr Shay McGuinness is one of the study's lead authors.
"The results suggest that about one out of 27 of them won't get a serious complication and those serious complications are things like stroke, heart attack and severe kidney damage after surgery."
Wellington Hospital Intensive Care Specialist, and study co-author, Paul Young, says the research is already having an impact in hospitals.
"These findings have already changed practice around the world and people are shifting to being more restrictive."
Dr McGuinness says it could save lives as well as a lot of donated blood.
"It could halve the amount of blood used during cardiac surgery in New Zealand," says Dr McGuinness.
NZ Blood Service spokesperson and Transfusion Medicine Specialist Dr Richard Charlewood says it's good for donors and the Blood Service.
"We're very keen to make sure that blood is not used wastefully and if less blood is needed that's all the better for everyone," says Dr Charlewood.
The Health Research Council-backed study is the very first completed by the New Zealand Improving Outcomes After Cardiac Surgery Network.