In vitro hemolysis of stored units of canine packed red blood cells

Effect of leukoreduction on the omics phenotypes of canine packed red blood cells during refrigerated storage

BACKGROUND

Red blood cell (RBC) storage promotes biochemical and morphological alterations, collectively referred to as storage lesions (SLs). Studies in humans have identified leukoreduction (LR) as a critical processing step that mitigates SLs. To date no study has evaluated the impact of LR on metabolic SLs in canine blood units using omics technologies.

OBJECTIVE

Compare the lipid and metabolic profiles of canine packed RBC (pRBC) units as a function of LR in fresh and stored refrigerated (up to 42 days) units.

ANIMALS

Packed RBC units were obtained from 8 donor dogs enrolled at 2 different Italian veterinary blood banks.

STUDY DESIGN AND METHODS

Observational study. A volume of 450 mL of whole blood was collected using Citrate-Phosphate-Dextrose-Saline-Adenine-Glucose-Mannitol (CPD-SAGM) transfusion bags with a LR filter to produce 2 pRBC units for each donor, without (nLR-pRBC) and with (LR-pRBC) LR. Units were stored in the blood bank at 4 ± 2°C. Sterile weekly samples were obtained from each unit for omics analyses.

RESULTS

A significant effect of LR on fresh and stored RBC metabolic phenotypes was observed. The nLR-pRBC were characterized by higher concentrations of free short and medium-chain fatty acids, carboxylic acids (pyruvate, lactate), and amino acids (arginine, cystine). The LR-pRBC had higher concentrations of glycolytic metabolites, high energy phosphate compounds (adenosine triphosphate [ATP]), and antioxidant metabolites (pentose phosphate, total glutathione).

CONCLUSION AND CLINICAL IMPORTANCE

Leukoreduction decreases the metabolic SLs of canine pRBC by preserving energy metabolism and preventing oxidative lesions.

Viability of erythrocytes in canine packed red blood cells stored in CPDA-1 is related to the presence of Mycoplasma haemocanis

Hemotropic mycoplasmas are associated with subclinical disease in dogs and should be identified in blood donors. The objective was to investigate the presence and effect of M. haemocanis in units of packed red blood cells (pRBC) during storage. Canine donors (n = 10) were screened for M. haemocanis by quantitative real-time PCR. pRBCs were obtained from 5 hemoplasma negative dogs and 5 hemoplasma positive dogs. Each pRBC was aliquoted into two 100 mL transfer bags and stored at 4 °C. M. haemocanis loads and biochemical variables (pH, bicarbonate, potassium, sodium, chlorite, glucose, lactate, ammonia, PCV, and % hemolysis) were evaluated on days 1, 7, 18, and 29. M. haemocanis loads increased in pRBC from day 1-29 of storage. Glucose decreased and lactate increase faster in pRBC with M. haemocanis. This study contributes to understand hemoplasma metabolism and reinforces that dog donors should be tested for hemoplasmas.

The hemostatic profile of cold-stored whole blood from non-greyhound and greyhound dogs over 42 days

Objectives

To compare the hemostatic characteristics of cold-stored whole blood (CSWB) from non-greyhound dogs (NGD) and greyhound dogs (GD) over 42 days of storage, notably, platelet closure time (PCT) (NGD only), manual platelet count (PLT) (GD only), ellagic acid (INTEM) and tissue factor activated (EXTEM) rotational thromboelastometry, prothrombin (PT) and activated partial thromboplastin time (aPTT), fibrinogen concentration (FIB), and the activities of factors (F) FII, FV, FVII, FVIII, FIX, FX, FXIII antigen (FXIII:Ag), and von Willebrand factor antigen (vWF:Ag).

Design

Whole blood from 10 NGD and 10 GD, was refrigerated in CPD blood bags at 4°C for 42 days. Blood was analyzed before refrigeration (day 0) and at day 1 (d1), 3, 5, 7, 10, 14, 17, 21, 24, 28, 31, 35, 38, and 42. Multivariate linear mixed effects models were created to evaluate coagulation parameters over time and compare NGD and GD. Data are summarized as estimated marginal means with 95% confidence intervals. Significance was set at P < 0.05.

Results

The PCT for all NGD CSWB was above the device limit by d7. The PLT for GD CSWB did not change during storage. The mean alpha-angle for INTEM and EXTEM decreased to <50% of baseline at d38 and d31 for NGD, and d31 and d17 for GD CSWB. The mean maximum clot firmness (MCF) for INTEM and EXTEM reduced to <50% of baseline at d42 and d28 for both GD and NGD. PT and aPTT for NGD and GD increased over time. For NGD CSWB, the mean FVIII and vWF:Ag activities decreased to <50% of baseline at d7 and d28, respectively, and FIB reached 0.982 g/dL by d24. For GD CSWB, FVIII, FXIII:Ag and FV activities decreased to <50% of baseline by d3, d38, and d38, respectively, and FIB was 0.982 g/dL at baseline. Alpha-angle and MCF for both INTEM and EXTEM, and activities for FII, FV, FIX, FXIII:Ag were significantly lower, and vWF:Ag was significantly higher overall in GD CSWB compared with NGD. A significant difference in the pattern of change over time was detected between NGD and GD in EXTEM alpha-angle, INTEM and EXTEM MCF, FII, and FVIII activities.

Conclusions

The in vitro viscoelastic parameters of GD and NGD CSWB declines over 42 days, but numerous hemostatic parameters (INTEM and EXTEM alpha-angle and MCF, activity of FII, FV, FV, FVII, FIX, FX, FXIII:Ag, vWF:Ag, and FIB) remain within 50% of baseline for more than 14 days. CSWB from GD compared to NGD has reduced hemostatic activity overall, but a similar pattern of decline for most parameters over time.

Evaluation of selected hematological, biochemical and oxidative stress parameters in stored canine CPDA-1 whole blood

Blood transfusions are mainly given to intensive care patients; therefore, additional complications that could arise from storage lesions in preserved blood should be avoided. It has been shown that human stored red blood cells are subject to changes that are considered to be a number of interdependent processes involving metabolic disarrangement and oxidative stress. The aim of our study was to determine alterations in selected hematological and biochemical parameters and to assess whether and when oxidative stress is a significant phenomenon in stored dog CPDA-1 whole blood. Ten ½ unit bags of whole blood donated from dogs and preserved with CPDA-1 (anticoagulant containing citrate, phosphate, dextrose and adenine) were stored for 5 weeks. Each week, a 9 ml sample was drawn aseptically to measure hematological parameters, selected metabolites, free hemoglobin content, osmotic fragility, antioxidant enzyme activity, total antioxidant capacity, malondialdehyde concentration and protein carbonyl content.

The results revealed an MCV decrease in the first week of storage and then a gradual increase; osmotic fragility decreased at that time and remained low throughout the study period. Leukodepletion became significant in the fourth week of storage. The free hemoglobin concentration continuously increased, with the greatest changes observed in the last two weeks of storage. The total antioxidant capacity changed in a reverse manner. Superoxide dismutase and glutathione peroxidase activities decreased from week 0 to week 3, and catalase activity tended to decrease over time. The highest malondialdehyde concentrations in blood supernatant were measured in the first week of storage, and the carbonyl concentration increased after 35 days.

Hematological changes and oxidative stress are already present in the first week of storage, resulting in depletion of the antioxidant system and subsequent accumulation of oxidation products as well as erythrocyte hemolysis, which are most pronounced at the end of the storage period.

Effect of microaggregate filter passage on feline whole blood stored for 35 days

OBJECTIVES

The aim of this study was to compare the characteristics of fresh and stored feline red blood cells (RBCs) after passage through an 18 μm microaggregate filter.

METHODS

Nine cats were recruited for a single blood donation using an open collection system. A simulated transfusion using a syringe driver and microaggregate filter was performed over 2 h with half the blood on the day of donation and the other half after 35 days of storage. Differences in haematological parameters, haemolysis percentage and osmotic fragility (OF) were compared on the day of donation pre-filter passage (D0-) vs day of donation post-filter (D0+) or day 35 storage pre-filter (D35-) and post-filter (D35+). Blood was cultured at D0+ and D35+.

RESULTS

There were no statistically significant differences in the D0- vs D0+ comparisons. There were statistically significant (P <0.05) increases in haemolysis percentage, red cell distribution width (RDW) percentage and mean OF, and decreases in packed cell volume (PCV), RBC count, haemoglobin and haematocrit for D0- vs D35-. The same was found for D0- vs D35+ with the addition of a significant increase in mean cell haemoglobin (MCH). For D35- vs D35+ only MCH significantly increased. At day 35, 6/9 units had haemolysis percentages that exceeded 1%. This increased to 8/9 of stored units post-filter passage. All blood units cultured negative.

CONCLUSIONS AND RELEVANCE

Fresh RBCs exhibited no in vitro evidence of injury following passage through an 18 μm microaggregate filter. Increased MCH was observed in the stored blood and may represent haemolysis induced by the filter. All other changes can be explained by storage lesion rather than filter passage. The findings highlight the importance of blood banking quality controls and the need for further research to assess the effects of transfusion technique, specifically filter passage, on storage lesion-affected feline blood.

The influence of leukoreduction on the acute transfusion-related complication rate in 455 dogs receiving 730 packed RBCs: 2014-2017

OBJECTIVE

To investigate the influence of prestorage leukoreduction of packed RBCs (pRBCs) on acute transfusion-related complication rate in dogs.

SETTING

Two private referral hospitals.

DESIGN

Retrospective case study.

ANIMALS

Four hundred and fifty-five dogs receiving nonleukoreduced (nLR) or leukoreduced (LR) pRBC between January 1, 2014 and July 31, 2017.

MEASUREMENTS AND MAIN RESULTS

Transfusions were retrospectively reviewed to record data about the patient, donor, unit, transfusion event, acute complications, hospital discharge, and cause of death. Of 730 transfusion events in 455 dogs, 288 used LR pRBC and 442 used nLR pRBC. There was a 18.9% (138/730) overall complication rate. Seven (0.96%) complications were life-threatening. The most common complications were pyrexia (5.6%), gastrointestinal signs (4.9%), and hemolysis with no other signs (4.1%). Pyrexia with no other clinical signs, consistent with a febrile nonhemolytic transfusion reaction (FNHTR), occurred in 3.2% of transfusion events. There was a significant (P = 0.03) decrease in the rate of FNHTR with LR pRBC (1%) versus nLR pRBC (4.5%). Use of LR pRBC did not decrease in-hospital mortality. The odds of any complication, hemolysis only, FNHTR, and more severe complications increased with pRBC age. Leukoreduction did not decrease the impact of pRBC age on these complications. Use of older pRBC did not increase the incidence of life-threatening complications or mortality. Dogs receiving pRBC for blood loss were more likely to have gastrointestinal and more severe complications than those dogs that had hemolysis. The effect of pRBC unit age on complications was not influenced by the underlying reason for transfusion. Dogs that received a previous transfusion were more likely to have respiratory complications.

CONCLUSION

In this study, the use of LR pRBC was associated with a decreased rate of FNHTR but no other complications. Unit age was associated with the incidence of hemolysis, FNHTR, and complication severity but not the rate of life-threatening complications or mortality.

The effect of position and frequency of mixing on canine packed red blood cell units during storage

OBJECTIVE

Hemolysis is an indicator of storage lesion that occurs in stored packed red blood cells (pRBCs) over time. Intermittent mixing of red blood cells in the additive solutions may be beneficial but may also result in iatrogenic injury. Position of units in storage may also affect the quality of the pRBCs. This prospective study was designed to evaluate hemolytic effect of mixing frequency and storage position on canine pRBCs over a period of 28 days.

DESIGN

Prospective in vitro study SETTING: Private practice referral hospital with an internal blood bank ANIMALS: Thirty-two healthy prescreened dogs enrolled in a volunteer blood banking program INTERVENTIONS: None MEASUREMENTS AND MAIN RESULTS: A total of 160 samples were evaluated. Forty canine pRBC units were split into 4 daughter bags and stored in varying positions with different mixing frequencies. Samples were stored upright and mixed daily, upright and mixed weekly, horizontally and mixed daily, or horizontally and mixed weekly for a period of 28 days. At days 0, 7, 14, and 28, samples from the units were analyzed to calculate percent hemolysis. No differences were found in any hemolytic indicators investigated (total hemoglobin, free plasma hemoglobin, and packed cell volume) until day 28 in all test groups. Canine pRBCs stored upright and mixed weekly or stored horizontally and mixed weekly resulted in less hemolysis and free plasma hemoglobin when compared to units stored horizontally and mixed daily only at day 28.

CONCLUSIONS

Statistically significant hemolysis was not evident amongst canine pRBC groups less than 28 days old suggesting that positioning and mixing frequency was irrelevant until day 28. Beyond 28 days despite the presence of hemolysis, no definitive recommendation could be made with respect to best practice for storage position or mixing frequency of stored canine pRBCs.

Hemolytic anemia blunts the cytokine response to transfusion of older red blood cells in mice and dogs

BACKGROUND

Transfusion of red blood cells (RBCs) stored for longer durations induces hemolysis and inflammatory cytokine production in murine and canine models. Despite immune system activation by stored RBCs, human randomized trials suggest that fresher RBC transfusions do not improve clinical outcomes. We hypothesized that underlying recipient hemolysis may affect cytokine responses to older RBC transfusions.

STUDY DESIGN AND METHODS

C57BL/6 mouse cohorts were infused with anti-TER119 antibody to induce hemolysis, rabbit anti-platelet antiserum to induce immune thrombocytopenia (ITP), or appropriate control antibodies. Two days later, mice were transfused with fresh or stored RBCs. Furthermore, in a prospective, randomized, blinded trial, 38 client-owned dogs with primary autoimmune hemolytic anemia (AIHA) and two dogs with ITP, requiring RBC transfusion, were enrolled and randomized to receive fresh (≤7 days) or old (≥21 days) stored RBC transfusions. Monocyte chemoattractant protein (MCP)-1 levels were assessed at defined times after transfusion.

RESULTS

Prior immune-mediated hemolysis blunted the MCP-1 response to stored RBC transfusion in mice (361 ± 111 pg/ml vs. 6836 ± 1528 pg/ml in mice with immune hemolysis vs. ITP, respectively; mean ± SD; p < .0001). Although hemolysis markers increased after transfusion of older RBCs, the cytokine response was also muted in dogs with AIHA. No differences in morbidity or mortality were evident comparing dogs randomized to fresh or old RBCs.

CONCLUSION

These data suggest that underlying hemolysis blunts inflammatory responses to old RBC transfusions. The canine data support randomized trial results suggesting a lack of clinical benefit with fresh RBC transfusions in subjects with underlying, baseline hemolysis.

Association of Veterinary Hematology and Transfusion Medicine (AVHTM) Transfusion Reaction Small Animal Consensus Statement (TRACS). Part 1: Definitions and clinical signs

OBJECTIVE

To use a systematic, evidence-based consensus process to develop definitions for transfusion reactions in dogs and cats.

DESIGN

Evidence evaluation of the literature was carried out for identified transfusion reaction types in dogs and cats. Reaction definitions were generated based on synthesis of human and veterinary literature. Consensus on the definitions was achieved through Delphi-style surveys. Draft recommendations were made available through industry specialty listservs and comments were incorporated.

RESULTS

Definitions with imputability criteria were developed for 14 types of transfusion reactions.

CONCLUSIONS

The evidence review and consensus process resulted in definitions that can be used to facilitate future veterinary transfusion reaction research.

Effect of Leukoreduction on Hematobiochemical Parameters and Storage Hemolysis in Canine Whole Blood Units

Simple Summary

During the storage of blood units, cells undergo many changes, defined as storage lesions; these are biochemical, morphological and immunological modifications and seem to be responsible for adverse post-transfusion effects in recipients. The pre-storage leukoreduction seems to reduce them. The aims of this study are both to evaluate the human filter effectiveness and the effect of pre-storage leukoreduction in stored canine whole blood units. We tested whole blood units, leukoreduced and not, obtained from seven enrolled subjects, until the 42nd day. The white blood cell (WBC) and platelet (PLT) counts are reported to express the leukoreduction effectiveness. As indicators of storage-induced hemolysis, the lactate dehydrogenase activity (LDH) and sodium, potassium, and chlorine electrolytes were measured in plasma, and the red blood cell (RBC) count, hemoglobin concentration (Hgb), and hematocrit (Hct) were obtained with the complete blood count (CBC). The mean corpuscular volume (MCV) values and morphological index obtained from blood smear evaluation were used as indices of morphological changes. We observed that the leukoreduction filter for human use is equally effective on canine whole blood and that leukoreduction has a partially protective role to prevent some storage lesions.

Abstract

Storage lesions (SLs) occur when the red blood cell quality is altered during the preservation of blood units. Pre-storage leukoreduction would limit the number of SLs. The aims of this study were to evaluate the effectiveness of a leukoreduction filter for human use and the effect of pre-storage leukoreduction on some ematobiochemical parameters in stored canine whole blood. Seven canine blood units were tested. Each one was divided into two units—one leukoreduced (LRWB) and one non-leukoreduced (nLRWB). On each unit, we determined the complete blood count (CBC), lactate-dehydrogenase (LDH), electrolytes (Na⁺, K⁺, Cl⁻), morphological index (MI) and hemolysis, on storage days 0, 7, 14, 21, 28, 35, and 42. Leukoreduction allowed a 98.30% recovery of the RBC count, retaining 99.69% and 94.91% of WBCs and PLTs, respectively. We detected a significant increase of LDH and MI with strongly higher values in nLRWB compared to LRWB. A progressive increase in electrolytes and LDH concentrations was observed as indices of stored hemolysis. LDH showed significantly lower values in LRWB units compared to nLRWB, suggesting its release from leukocytes. In the majority of units, hemolysis reached 1% on the 42nd day of storage. We assert the human leukoreduction filter effectiveness on canine whole blood, and we recommend using nLRWB before day 14, especially for critically ill patients. The difference of the basal hemolysis (day 0) percentages observed between subjects suggests that more studies should be performed to confirm a possible inter-individual donor biological variability of RBC membrane resistance, as happens in humans.

Effects of storage and leukocyte reduction on the concentration and procoagulant activity of extracellular vesicles in canine packed red cells

OBJECTIVES

To characterize the size and procoagulant activity of extracellular vesicles (EV) that accumulate in canine packed red blood cells (pRBCs) over time and the effect of leukocyte reduction on these characteristics.

DESIGN

Prospective cohort study.

SETTING

Private small animal specialty referral hospital and university research laboratories.

ANIMALS

Ten healthy blood donor dogs.

INTERVENTIONS

Five pRBCs units were obtained according to standard protocols, and 5 were leukocyte-reduced prior to processing. Platelet-free supernatant from the pRBC units was collected on days 0, 10, 20, 32, and 42.

MEASUREMENTS AND MAIN RESULTS

Nanoparticle tracking analysis was performed to determine the size and concentration of EVs. Thrombin generation associated with phosphatidylserine-positive EVs was determined using a capture assay. Factor Xa generation associated with phosphatidylserine-positive EVs and tissue factor-positive EVs was measured in a subset of EVs isolated by centrifugation of the supernatant at 20,000 × g. R package nparLD and the Mann-Whitney U-test were used to determine the effect of duration of storage and the effect of leukocyte reduction, respectively. Small (mean < 125 nm) procoagulant EVs accumulated over time, with significant increases occurring on or after day 20 in both non-leukocyte reduced and leukocyte-reduced units. The procoagulant activity of the EVs was due to phosphatidylserine, not tissue factor. Increases in EV concentration and procoagulant activity occurred earlier in non-leukocyte reduced units. Extracellular vesicle accumulation and procoagulant activity were not decreased at any individual time point by leukocyte reduction.

CONCLUSIONS

Further studies characterizing and determining the clinical relevance of small procoagulant EVs in pRBCs are warranted.

Association of Veterinary Hematology and Transfusion Medicine (AVHTM) Transfusion Reaction Small Animal Consensus Statement (TRACS) Part 2: Prevention and monitoring

OBJECTIVE

To systematically review available evidence to develop guidelines for the prevention of transfusion reactions and monitoring of transfusion administration in dogs and cats.

DESIGN

Evidence evaluation of the literature (identified through Medline searches through Pubmed and Google Scholar searches) was carried out for identified transfusion reaction types in dogs and cats. Evidence was evaluated using PICO (Population, Intervention, Comparison, Outcome) questions generated for each reaction type. Evidence was categorized by level of evidence (LOE) and quality (Good, Fair, or Poor). Guidelines for prevention and monitoring were generated based on the synthesis of the evidence. Consensus on the final recommendations and a proposed transfusion administration monitoring form was achieved through Delphi-style surveys. Draft recommendations and the monitoring form were made available through veterinary specialty listservs and comments were incorporated.

RESULTS

Twenty-nine guidelines and a transfusion administration monitoring form were formulated from the evidence review with a high degree of consensus CONCLUSIONS: This systematic evidence evaluation process yielded recommended prevention and monitoring guidelines and a proposed transfusion administration form. However, significant knowledge gaps were identified, demonstrating the need for additional research in veterinary transfusion medicine.

In vitro iatrogenic hemolysis of canine packed red blood cells during various rapid transfusion techniques

OBJECTIVE

To evaluate which rapid blood administration technique causes the least iatrogenic hemolysis in canine packed red blood cells (pRBCs) as determined by plasma free hemoglobin (fHb) and percent hemolysis (% hemolysis).

DESIGN

Prospective in vitro randomized study.

SETTING

Private referral center.

ANIMALS

None.

INTERVENTIONS

Thirteen units of canine pRBCs were divided equally into 5 aliquots, resulting in 65 trials. The aliquots of each unit were subjected to the following administration techniques: gravity-driven (control), an infusion pump at maximal rate, application of a pressure bag, manual compression, and syringe bolus. Plasma fHb and % hemolysis were recorded before and after each trial. Rate of administration (mL/s) was calculated for each method.

MEASUREMENTS AND MAIN RESULTS

Compared to the control, there were no significant increases in % hemolysis or plasma fHb noted among any of the trial methods. The manual compression and syringe bolus methods resulted in the fastest transfusion rates, whereas the infusion pump was not faster than the gravity-driven method. Despite a storage time of ≤14 days, 15% of pRBC units had unsuitable (>0.8%) hemolysis before even being subjected to the trials.

CONCLUSIONS

Commonly used rapid infusion techniques in small animal transfusion medicine do not cause significant iatrogenic hemolysis of canine pRBCs in vitro, although a significant risk is present in stored blood. This suggests that if an expedited transfusion is needed, any method described in this study could be considered, although stored pRBCs should be tested for unsuitable levels of hemolysis prior to transfusion.

Ovine red cell concentrates for transfusion research - is the storage lesion comparable to human red cell concentrates?

BACKGROUND AND OBJECTIVES

Sheep are increasingly being used as a large in vivo animal model of blood transfusion because they provide several advantages over small animals. Understanding the effects of storage duration on ovine (ov) red cell concentrates (RCCs) and how these changes compare with stored human (hu) RCCs is necessary to facilitate clinical translation of research findings.

MATERIALS AND METHODS

OvRCCs (n = 5) collected and processed in standard human blood collection packs, and equivalent huRCCs provided by Australian Red Cross Lifeblood (n = 5), were stored at 2-6°C for 42 days, with samples collected weekly. Haemolysis index was determined by measuring supernatant haemoglobin concentration. Biochemical parameters were evaluated using a blood gas analyser. Energy metabolites and biologically active lipids were measured using commercial assays. Osmotic fragility was determined by lysis in various saline concentrations. Extracellular vesicles were characterized by nanoparticle tracking analysis.

RESULTS

Ovine red blood cells (RBCs) are double in number, smaller in size and more fragile than human RBCs. Haematological values were unchanged throughout storage. In contrast, biochemical and metabolic values, and haemolysis index in three of the five ovRCCs exceeded huRCCs licensing criteria by day 42. Accumulation of extracellular vesicles and biologically active lipids was comparable between huRCCs and ovRCCs.

CONCLUSION

This study documents similarities and differences in the storage lesion of ovRCCs and huRCCs. This new information will guide the design of ovine transfusion models to enhance translation of findings to human transfusion settings.

Hematological, biochemical and microbiological evaluation of feline whole blood units collected using an open system and stored for 35 days

Despite the increasing availability of feline blood, which is collected and stored for transfusion purposes, few studies have assessed the effect of storage on feline whole blood (WB) units. The purpose of this study was to investigate selected hematologic and biochemical changes during storage of feline WB units and to determine when they occurred. Data from a quality control program for WB units was used in this study. Twelve feline WB units, collected using an open system, were sampled every 7 days from the point of collection to the end of storage at 35 days (D0, D7, D14, D21, D28, and D35). Measurements at each time point were: (1) hematologic parameters; (2) percentage hemolysis; (3) morphologic index scored at 0-3, based on echinocyte transformation of the erythrocytes; and (4) selected biochemical parameters. Aerobic and anaerobic culture was performed at D0 and D35. Results were compared statistically to D0 (statistical significance set at <0.01). Storage did not result in statistically significant changes in measured hematological parameters. There were statistically significant increases in percentage hemolysis and morphologic index, starting from D21 (P=0.000 and P=0.004, respectively). Glucose decreased significantly from D21 (P=0.003); potassium increased significantly from D7 (P=0.001); and sodium increased significantly, starting from D28 (P=0.009). Bacteria were not isolated. Blood in feline WB units collected using an open system underwent some significant storage changes that were time-dependent. As these changes could affect the quality and the utility of stored WB used in feline transfusion medicine, further study is required to determine their clinical importance.