Background to the SWiFT Aotearoa Trial

For the last ten years, the Auckland Rescue Helicopter has been carrying two units of whole blood for use in haemorrhaging patients. While various services have carried blood for specific missions, the Auckland Rescue Helicopter was the first in the Southern hemisphere to do this as a routine. This meant that they were prepared in case they got retasked to a different emergency while already in the air.

Pre-hospital transfusion has been shown to save lives, especially if the transport time is longer than 20 minutes. One of the significant variables in studies in pre-hospital transfusion is whether the intensity of care is able to proceed once the patient arrives at hospital. With this in mind, Code Crimson was initiated at hospitals where the Auckland Rescue Helicopter took patients. This is a "system activation" where key hospital personnel and services are notified and readied for the arrival of the patient so that definitive haemorrhage care can be started as soon as the patient arrives.

The Auckland Rescue Helicopter has been unusual in being able to carry whole blood, rather than separate units of red cells and plasma. Both red cells and plasma are needed but having them in a single bag makes it quicker and easier to transfuse in the field in a high complexity situation.

The next step in the evolution of pre-hospital transfusion is to look at the make-up of whole blood. The standard of care in New Zealand is a leucodepleted unit of O negative whole blood. The standard leucodepletion filter removes white cells, known to cause reactions in patients and not add to their care. Unfortunately, this filter also removes the platelets from the blood. Platelets are an integral part of clotting. What is unclear is if giving platelets early in haemorrhage resuscitation contributes to outcomes.

Terumo BCT has manufactured a leucodepletion filter that allows platelets to pass through. This filter is in use in a number of countries, most notably in the United States. However, the filter is more expensive than the standard filter, so there were concerns about the justification for this added expense.

In early 2023, the SWiFT trial in the UK started, comparing platelet-rich whole blood with red cells & plasma. New Zealand had planned to join this trial but, due to faster than expected recruitment of patients, the UK opted to keep the trial as a single country trial.

However, what became apparent in discussions with the UK trial co-ordinators is that the transport times in the UK trial were often short. This is due to the density of hospitals in the UK.

With that in mind, we believed that New Zealand, with its longer transport times, as well as comparing platelet-rich vs platelet-poor whole blood (as opposed to separate bags of red cells and plasma) would be able to contribute to the understanding of whole blood transfusion in pre-hospital transfusion.