Fifteen Years Since the Head Injury Retrieval Trial: What Have We Learned?

It is 15 years since the Head Injury Retrieval Trial recruited its last patient in Sydney, Australia. The trial remains the only randomised controlled trial of severely injured patients to directly compare an advanced clinical intervention team delivered by a helicopter emergency medical service to a paramedic ground response in the world medical literature. Issues with the conduct and confounding of the trial are reviewed, as well as the evolution of the Sydney prehospital trauma system in the 15 years since the trial concluded. The design of the Sydney prehospital trauma system remains suboptimal and non-evidence based.