Advances in veterinary blood purification
Illustration of the centrifugal separation and collection of blood components in an apheresis machine (right), and photograph of the actual separation cartridge in the spinning centrifuge (left).
Most people are familiar with the process of hemodialysis—taking impure blood from one’s system, purifying it, and returning it to the body. That’s a very simple explanation of a highly complicated process. A new, state-of-the-art blood purification procedure—therapeutic plasma exchange (TPE)—is making headway in veterinary medicine, joining the ranks of hemodialysis and another method, hemoperfusion. TPE is an apheresis (removal of impurities from blood) treatment in which plasma contaminated with damaging (pathogenic) antibodies, toxins or abnormal proteins is separated from the patient’s flowing blood and exchanged with donor plasma that is returned to the patient to render the patient less susceptible to or free from immunologic attack or other pathologic processes.
Unlike hemodialysis or hemoperfusion (in which impurities are removed from intact blood), therapeutic apheresis separates the blood into its component fractions, and the pathogenic fraction is removed or specifically altered prior to return to the patient. The remainder of the (purified) blood is returned to the patient. The pathologic component is delivered to a waste bag and discarded.
TPE has been used for decades in human medicine to manage a variety of disorders. The indications for, and evidence-based effectiveness of, TPE for these conditions has been grouped into four categories, establishing TPE as: the standard of care (category I), having evidence-based effectiveness (category II), having inconclusive evidence (category III), or having little identified effect (category IV). These categories help clinicians decide whether to use TPE to treat specific disorders. Experience with the use of TPE in animals is limited to date, and it is difficult to predict effectiveness comparable to that achieved for similar diseases in people; however, this classification provides guidance for potential use of TPE to treat animal diseases when the current standard of care is ineffective.
The Hemodialysis and Blood Purification Service at the VMTH now has experience in the use of TPE to manage immune- mediated neurologic disorders (myasthenia gravis and polyradiculoneuropathy) and immune-mediated hemolytic anemia refractory to medical management. TPE has emerged as a viable and promising treatment option for dogs with these two life-threatening conditions. The role of TPE in several other immune-mediated, metabolic, or toxic conditions in animals awaits further investigation. UC Davis researchers and clinicians are hopeful that the broad TPE categorizations and successes seen in human healthcare can soon translate to veterinary medicine for the benefit of animals.
To date, TPE has been used on about a dozen dogs and one horse. The treatment on the horse, conducted in May, is (to our knowledge) the first known equine application of TPE in veterinary medicine.
Communications & Marketing Officer - UC Davis Veterinary Medical Teaching Hospital