CAtion leakage from stored RED blood cells (CARED)
Dr Rebecca Cardigan
Institution or company
NHS Blood and Transplant
The ‘CARED’ study investigates rare genetic variants in red blood cells which cause a condition known as familial pseudohyperkalaemia (FP). Pseudohyperkalaemia means ‘falsely elevated potassium in blood’. In FP, red cells behave normally at body temperature but not at cold temperatures; thus, FP is not known to affect an individual’s wellbeing and it is usually undetected.
Red cells from donated blood are stored in special storage bags in the fridge for up to 35 days prior to transfusion. During this time potassium slowly leaks out of the red cells into the surrounding liquid in the storage bag. FP red cells release high levels of potassium much more quickly than red cells without FP (standard) at cold temperatures.
Due to the help from the Bioresource volunteers, who donated their blood for this study, the research team were able to show that red cells from individuals with FP, have similar potassium levels in the bag on day 7 of cold storage to standard red cells on day 35.
In the blood service, the Blood Service now restrict the shelf life of red cells meant for transfusing babies or small children at large amounts from 35 to only 5 days after the blood has been collected; in part to control for the amount of potassium in the bag of red cells. This is because transfusion of large amounts of potassium could have negative consequences for vulnerable recipient groups. As FP red cells would have unexpectedly high levels of potassium early in storage, the risk is too high for the infant population. Therefore, due to this study, red cell donations from known FP individuals are prevented from being transfused to babies or small children. However, red cell donations from FP individuals are still acceptable for transfusion to adult recipients.
In a follow up study, the research team wanted to see what effect irradiation has on FP red cells. Irradiating red cells is a standard procedure for recipients with low immune system, as it ensures any white cells left over in the red cell bag, which could harm the recipient, are rendered inactive. Irradiation causes some damage to the red cells, including increased release of potassium, so the team wanted to determine whether this damage is worse in FP red cells.
In a study conducted across 2 centres, in Cambridge and in Australia, blood was collected from Bioresource volunteers, as well as from Australian Red Cross Lifeblood from donors in Australia. The team found that irradiating FP red cells did not cause worse damage, and the red cells have acceptable quality for transfusion. This is an important finding that reassures our patients’ safety.
The CARED group would like to thank Bioresource volunteers for their donation that made these studies feasible.
The findings from this study have been published in The Journal of AABB Transfusion. See here for further details.