Split red blood cell units contain defined extracellular K levels, which are improved by a washing procedure.

Background And Objectives: We should control free K during massive transfusion (>80 mL/kg) of red blood cells (RBCs) in small children. To manage this, several national and international guidelines recommend using RBCs stored only up to 7 days. We tested a washing step for RBCs in saline-adenine-glucose-mannitol (SAGM) with or without irradiation to reduce supernatant K levels, improve quality and potentially extend the shelf life of stored RBCs.

Materials And Methods: RBCs of 240-330 mL were prepared from whole blood donations, then split into halves and stored in SAGM solution at 4 ± 2°C for 21 days. RBCs were split and washed on Days 1 and 8, and some were gamma-irradiated on Day 8. Glucose, lactate, lactate dehydrogenase (LDH), adenosine triphosphate (ATP), K and haemolysis were determined over 21 days.

Results: After washing on Day 1, only glucose and lactate improved, whereas after washing on Day 8, LDH and K also improved. Irradiation resulted in accelerated K accumulation and increased haemolysis. Mean extracellular K concentrations were 21.2 ± 1.03 mM after irradiation on Day 8 versus 1.12 ± 0.05 mM after irradiation plus wash on Day 8, and 38.80 ± 2.13 mM on Day 10 after irradiation on Day 8 and 16.6 ± 0.05 mM on Day 10 after irradiation plus wash on Day 8.

Conclusion: K concentrations remained <25 mM within 8 days of storage. We recommend irradiation by Day 8 at the latest for neonatal transfusion. The shelf life may be extended by another 48 h if the RBCs are also washed.