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How long can you keep your pRBC transfusions around? | VETgirl Veterinary CE Podcasts

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In today’s VETgirl online veterinary continuing education podcast, we review how long you can keep your packed red blood (pRBC) cell transfusions around. 2-3 weeks? 4-6 weeks? What’s the right answer? Does it depend on the patient, their disease, or the hospital’s protocol?

Most people have become aware of the controversy around the appropriate storage time for blood products, beyond which their administration can result in harmful effects in the recipient. Since the introduction of blood component therapy several decades ago, strategies to maximum storage duration and oxygen-carrying capacity of red blood cell-containing blood products have been investigated. Depending on the anticoagulant and RBC preservative used (e.g., CPDA, etc.), pRBCs can be stored for up to 5-6 weeks. However, storage lesions or changes in the red cells can occur during storage, can alter oxygen-carrying capacity, lead to red cell fragility, and result in molecular changes that have been associated with negative immune responses in recipients.

These “storage lesions” are thought to account for the findings in recent studies linking the administration of blood products stored for longer periods of time to complications such as acute lung injury (ALI), acute kidney injury (AKI), multiple organ failure, immunomodulation, and even death in human patients. Less information is available in the veterinary literature investigating blood product age with complications; however, there is evidence to suggest that similar changes in immune function, as well as organ compromise can occur in animals. A recent retrospective study by Hann et al out of the University of Pennsylvania investigated the association between the age of transfused pRBCs and complications in approximately 3,100 dogs. In this study, they found that longer pRBC storage was associated with the development of coagulopathies and thromboembolic disease. Specifically, in a subset of dogs with hemolysis (of which 90% had IMHA), for every 7 day increase in PRBC storage, there was a 0.8 lesser odds of 30 day survival. This study suggests that longer storage of blood products has negative effects on recipient morbidity and mortality; however, prospective studies are needed to confirm these associations.

Concerns regarding the appropriate time to store RBC-containing blood products has led to ethical debates about which patients should receive which stored blood products. Ethical debates also exist about the sustainability of today’s blood banking system, should the duration of acceptable storage be decreased below what is currently accepted. Already, some human and veterinary hospitals have adjusted their transfusion strategies to favor the administration of younger PRBCs in certain situations. (VETgirl personally does this for IMHA patients). As you can imagine, if your blood products are not closely monitored or used regularly, this can lead to the discard of several blood products once they become “older”, perhaps even before their 4-6 week expiration date. Therefore, Holowaychuk et al wanted to evaluate this in a study entitled The effect of blood usage protocol on the age of packed red blood cell transfusions administered at 2 veterinary teaching hospitals. They wanted to assess the differences in the age of units of packed RBCs administered to dogs at 2 tertiary referral veterinary teaching hospitals with different age-related blood transfusion protocols.

Information was collected from the medical records of dogs receiving pRBC transfusions at North Carolina State University and the Ontario Veterinary College over a 1-year period between June 2010 and May 2011. Dogs were excluded from the analysis if the medical record or administered PRBC information was incomplete or missing, or if pRBC from commercial blood banks were administered, since the age of purchased PRBCs was often unavailable. The data that was recorded from the medical record included number of transfused units that were older than 14 days, number of transfused units that were older than 30 days, and the age of the oldest unit transfused during that visit. The mean age of pRBC units administered during the visit was also recorded and was calculated by dividing the sum of the age of all of the PRBC units transfused by the total number of units transfused during that visit.

During the year that the study was performed, NCSU’s policy was to store units in a designated blood product refrigerator, with instructions for clinicians and veterinary technicians to first select the oldest available PRBC unit of the appropriate volume and compatibility. Sometimes newly collected units were not made available for crossmatching until most of the older units were used, which was at discretion of the blood bank coordinator. By comparison, at OVC units were stored in a designated refrigerator, but according to age calculated from the date of blood collection. Specifically, units were categorized as less than or equal to 12 days old or > 12 days old and were chosen at the discretion of the clinician or veterinary technician such that fresher units could be administered if desired. Both hospitals had otherwise identical hospital-run canine blood banking programs that performed routine blood collections from client- and staff-owned dogs to meet the needs of the hospitalized patients. A triple-bag collection system with added red cell preservative was used and units were stored for a maximum of 42 days.

Altogether, 124 dogs from NCSU and 66 dogs from OVC were included. Statistical analysis showed that NCSU administered PRBC units with a significantly higher mean age, which was 19 days compared to a mean age of 11 days at OVC. NCSU also transfused a larger number of units more than 14 days old, which was a median of 1 unit per dog visit, compared to 0 per dog visit at OVC. Finally, the oldest unit administered at NCSU was also older than OVC in that it was a median of 21 days at NCSU vs. 9 days at OVC. But probably the most compelling information that was garnered from this study was the discovery that almost 100 expired units were discarded at OVC during the year-long study period, compared to an estimated 15 expired units at NCSU. Whereas NCSU had to purchase some pRBC units to meet the demands of their hospital, OVC did not purchase any pRBC units from commercial blood banks during the study period. A difference in the number of units transfused > 30 days old was not found between the 2 hospitals, but this was likely because both hospitals, especially OVC, transfused relatively few units in this age range.

So, what can we learn from this VETgirl podcast? Well…clearly the discovery of the large number of pRBC units that were discarded during this year-long study at OVC was a disturbing finding. Unfortunately, the year that this study was performed represented a time when the hospital’s caseload dropped substantially. The change in economy in Canada was about 2 years behind that in the USA and at the same time the economy took a downturn, 2 new referral hospitals were built in the greater Toronto area. These factors affected the OVC caseload, which affected the overall number of transfusions administered. Because people were in the habit of choosing the “fresher” blood products, but the blood bank had not adjusted its supply of products, more products were moved into the > 12 day old category and became less desired by clinicians and technicians. Since this study was performed, the protocol at OVC has changed such that there is no longer a designation of < or > 12 day old products and the number of donations has been adjusted to more appropriately meet demand. At both NCSU and OVC, an electronic spreadsheet is used to closely follow blood product use, donor availability, and blood product demand in order to minimize the number of discarded expired products.

But the question remains…if older blood products are “bad” for our patients, how can we go about maximizing our use of stored blood products while minimizing the number we discard? A recent study used a simulation model to investigate a protocol whereby the oldest blood that is < 14 days old is chosen and if no blood < 14 days old is available then the youngest blood > 14 days is chosen. The authors of the study determined that as long as a hospital’s blood product supply is greater than the demand, this strategy would decrease the mean age of transfused blood products, while decreasing the amount that would need to be purchased from outside sources. Essentially, this is a strategy that would have worked out well for a hospital such as OVC during the study period, when blood products might reach their expiration date. However, this protocol would not be needed for a hospital such as NCSU, whose demand would sometimes exceed their supply. In those situations, the authors of the study suggested that the hospitals continue to administer the oldest products first, as they were unlikely to administer products near the end of their expiration.

So, for now it seems that the practice of administering the oldest blood products first continues to be the most logical choice, for most hospitals whose blood product demands exceed their supply. Alternative strategies might be considered for those whose supply exceeds their demand, but with caution not to over-select for younger or fresher products, such that older products expire and are discarded. Blood products remain too precious of a resource and given the volunteer time of owners and dogs that participate in blood donor programs, we want to use these products as much as we can! There is no doubt that as with so many subjects in veterinary medicine, prospective randomized trials are needed to more accurately assess associations between the age of transfused RBC units and outcome in dogs, before firm recommendations can be made regarding the appropriate storage duration and allocation of blood products in veterinary hospitals. In the meantime, don’t let those blood products go to waste!

References:
1. Holowaychuk MK, Musulin SE. The effect of blood usage protocol on the age of packed red blood cell transfusions administered at 2 veterinary teaching hospitals J Vet Emerg Crit Care 2015;25(5):679-683.

2. Hann L, Brown DC, King LG, Callan MB. Effect of duration of packed red blood cell storage on morbidity and mortality in dogs after transfusion: 3,095 cases (2001-2010). J Vet Intern Med 2014;28(6):1830-1837.

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