Effects of potassium adsorption filters on the removal of ammonia from blood products.

BACKGROUND: Although ammonia in plasma does not usually pass through the blood-brain barrier (BBB), in cases of traumatic brain injury it may do so, acting as a neurotoxin on the brain. Excess intake of ammonia should be restricted in conditions involving BBB breakdown, such as traumatic brain injury. Washing is a method to remove ammonia from blood products, but fresh-frozen plasma and albumin products cannot be washed. A potassium adsorption filter (PAF) can remove not only potassium, but also ammonia from red blood cell solutions. We, therefore, examined the effects of a PAF on the removal of ammonia from a range of blood products.

MATERIALS AND METHODS: Ammonia concentrations were measured in expired red blood cell solutions, fresh-frozen plasma, and platelet concentrates and purchased albumin products before and after filtration through a PAF. The PAF was primed with saline, which was removed before the filter was used.

RESULTS: The percentages of ammonia removal from the red blood cell solutions, fresh-frozen plasma, plasma concentrates, 20% albumin and 5% albumin were approximately 76-87%, 21-31%, 53%, 77-92% and 49-63%, respectively.

DISCUSSION: A PAF appears capable of removing ammonia from a range of blood products, although the reason for the lesser effect on the ammonia concentration in fresh-frozen plasma compared to other blood products remains unknown. We hypothesise that, by lowering ammonia levels in blood products, the PAF could improve the clinical prognosis of neonates with an underdeveloped BBB or patients with BBB breakdown following traumatic brain injury.