Transfused older stored red blood cells improve the clinical course and outcome in a canine lethal hemorrhage and reperfusion model

Impact of a cell salvage device on blood transfusions to dogs undergoing surgery at a referral veterinary hospital

OBJECTIVE

To determine the number of homologous blood transfusions received by canine surgical patients after introducing a cell salvage device (CSD), trends in surgeries requiring blood transfusion, and the incidence of transfusion reactions.

STUDY DESIGN

Retrospective study.

SETTING

Single referral hospital.

ANIMALS

All dogs having surgery at a single center (November 2015 to February 2021).

INTERVENTIONS

Medical records of dogs having surgical treatment, including those that received either an autologous or homologous blood transfusion, were reviewed. The surgical patients were the baseline population, and the 2 transfusion groups were compared within this population to analyze the trends.

MAIN RESULTS

A total of 37 and 86 dogs received autologous and homologous blood transfusions, respectively. There was an upward trend in the number of total monthly blood transfusions. No significant increase in the monthly number of homologous transfusions was observed before or after acquisition of the CSD. There was also an upward trend in total monthly surgeries, including those with higher risks of hemorrhage. Dogs receiving homologous blood transfusions had a higher incidence of clinical signs consistent with transfusion reactions (6.98%).

CONCLUSIONS

An upward trend in autologous blood transfusions was seen with the introduction of a CSD. Hospitals with large surgical caseloads at high risk of hemorrhage may see a decreased need for outsourced blood products with the use of the CSD. The device can lead to a more responsible use of an increasingly scarce resource and decrease the risk of a blood transfusion reaction in dogs.

Different-sized extracellular vesicles derived from stored red blood cells package diverse cargoes and cause distinct cellular effects

BACKGROUND

The formation of extracellular vesicles (EVs) occurs during cold storage of RBCs. Transfusion of EVs may contribute to adverse responses in recipients receiving RBCs. However, EVs are poorly characterized with limited data on whether distinct vesicles are formed, their composition, and potential biological effects.

STUDY DESIGN AND METHODS

Stored RBC-derived EVs were purified using protocols that separate larger microvesicle-like EVs (LEVs) from smaller exosome-like vesicles (SEVs). Vesicles were analyzed by electron microscopy, content of hemoglobin, heme, and proteins (by mass spectrometry), and the potential to mediate lipid peroxidation and endothelial cell permeability in vitro.

RESULTS

SEVs were characterized by having an electron-dense double membrane whereas LEVs had more uniform electron density across the particles. No differences in hemoglobin nor heme levels per particle were observed, however, due to smaller volumes, SEVs had higher concentrations of oxyHb and heme. Both particles contained antioxidant proteins peroxiredoxin-2 and copper/zinc superoxide dismutase, these were present in higher molecular weight fractions in SEVs suggesting either oxidized proteins are preferentially packaged into smaller vesicles and/or that the environment associated with SEVs is more pro-oxidative. Furthermore, total glutathione (GSH + GSSG) levels were lower in SEVs. Both EVs mediated oxidation of liposomes that were prevented by hemopexin, identifying heme as the pro-oxidant effector. Addition of SEVs, but not LEVs, induced endothelial permeability in a process also prevented by hemopexin.

CONCLUSION

These data show that distinct EVs are formed during cold storage of RBCs with smaller particles being more likely to mediate pro-oxidant and inflammatory effects associated with heme.

Large Animal Models for Simulating Physiology of Transfusion of Red Cell Concentrates-A Scoping Review of The Literature

Background and Objectives: Transfusion of red cell concentrates is a key component of medical therapy. To investigate the complex transfusion-associated biochemical and physiological processes as well as potential risks for human recipients, animal models are of particular importance. This scoping review summarizes existing large animal transfusion models for their ability to model the physiology associated with the storage of erythrocyte concentrates. Materials and Methods: The electronic databases PubMed, EMBASE, and Web of Science were systematically searched for original studies providing information on the intravenous application of erythrocyte concentrates in porcine, ovine, and canine animal models. Results: A total of 36 studies were included in the analysis. The majority of porcine studies evaluated hemorrhagic shock conditions. Pig models showed high physiological similarities with regard to red cell physiology during early storage. Ovine and canine studies were found to model typical aspects of human red cell storage at 42 days. Only four studies provided data on 24 h in vivo survival of red cells. Conclusions: While ovine and canine models can mimic typical human erythrocyte storage for up to 42 days, porcine models stand out for reliably simulating double-hit pathologies such as hemorrhagic shock. Large animal models remain an important area of translational research since they have an impact on testing new pharmacological or biophysical interventions to attenuate storage-related adverse effects and allow, in a controlled environment, to study background and interventions in dynamic and severe disease conditions.

Allergy, inflammation, hepatopathy and coagulation biomarkers in dogs with suspected anaphylaxis due to insect envenomation

Objectives

To compare concentrations of biomarkers of; allergy [mast cell tryptase (MCT) and histamine], inflammation [interleukin (IL)-6,-10, and-18, CXCL8, CCL2, keratinocyte chemoattractant (KC), C-reactive protein (CRP)], endothelial glycocalyx shedding (hyaluronan), coagulation [prothrombin time, activated partial thromboplastin time, fibrinogen concentration, and von Willebrand Factor antigen, protein C (PC) and antithrombin (AT) activity], and hepatopathy [alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and total bilirubin] between dogs with anaphylaxis after suspected insect exposure, dogs with critical illness, and healthy dogs.

Design

This was a single center prospective clinical observational comparative biomarker study that included 25 dogs with anaphylaxis (evidence of insect exposure, acute dermatological signs, and other organ involvement), 30 dogs with other critical illness, and 20 healthy dogs. Differences across groups in biomarker concentrations were tested using one-way ANOVA or Kruskal-Wallis test, with significant P values (<0.05) reported for pairwise differences detected by post-hoc tests. Logistic regression models were used to calculate the area under the receiver operator characteristic curve (AUROC) for discrimination between anaphylaxis and non-anaphylactic illness.

Results

Histamine concentration was significantly higher in the anaphylaxis group than the healthy (P < 0.001) and critically ill groups (P < 0.001), whereas no differences in MCT were detected amongst groups. Biomarker concentrations that were increased relative to healthy dogs in both the anaphylaxis and critically ill groups included IL-10 (P < 0.001 and P = 0.007, respectively), CCL2 (P = 0.007 and P < 0.001, respectively) and AST (both P < 0.001), whereas only the critically ill group had significantly increased CRP (P < 0.001), IL-6 (P < 0.001), KC (P < 0.001), ALP (P < 0.001), and fibrinogen (P = 0.016) concentrations, compared to the healthy group. Only dogs with anaphylaxis had significantly higher hyaluronan (P = 0.021) and ALT (P = 0.021) concentrations, and lower PC (P = 0.030) and AT (P = 0.032) activities, compared to healthy dogs. Both CRP and histamine concentration showed good discrimination between anaphylaxis and other critical illness, with an AUROC of 0.96 (95% CI 0.91-1) and 0.81 (95% CI 0.69-0.93), respectively.

Conclusions

This preliminary study in dogs with anaphylaxis after suspected insect exposure, found evidence of an early innate immune response, glycocalyx shedding and anticoagulant consumption. Both CRP and histamine showed potential clinical utility for differentiation between anaphylaxis and other critical illness.

Volume Resuscitation in the Acutely Hemorrhaging Patient: Historic Use to Current Applications

Acute hemorrhage in small animals results from traumatic and non-traumatic causes. This review seeks to describe current understanding of the resuscitation of the acutely hemorrhaging small animal (dog and cat) veterinary patient through evaluation of pre-clinical canine models of hemorrhage and resuscitation, clinical research in dogs and cats, and selected extrapolation from human medicine. The physiologic dose and response to whole blood loss in the canine patient is repeatable both in anesthetized and awake animals and is primarily characterized clinically by increased heart rate, decreased systolic blood pressure, and increased shock index and biochemically by increased lactate and lower base excess. Previously, initial resuscitation in these patients included immediate volume support with crystalloid and/or colloid, regardless of total volume, with a target to replace lost vascular volume and bring blood pressure back to normal. Newer research now supports prioritizing hemorrhage control in conjunction with judicious crystalloid administration followed by early consideration for administration of platelets, plasma and red blood during the resuscitation phase. This approach minimizes blood loss, ameliorates coagulopathy, restores oxygen delivery and correct changes in the glycocalyx. There are many hurdles in the application of this approach in clinical veterinary medicine including the speed with which the bleeding source is controlled and the rapid availability of blood component therapy. Recommendations regarding the clinical approach to volume resuscitation in the acutely hemorrhaging veterinary patient are made based on the canine pre-clinical, veterinary clinical and human literature reviewed.

Mechanistic insights into cell-free hemoglobin-induced injury during septic shock

Cell-free hemoglobin (CFH) levels are elevated in septic shock and are higher in nonsurvivors. Whether CFH is only a marker of sepsis severity or is involved in pathogenesis is unknown. This study aimed to investigate whether CFH worsens sepsis-associated injuries and to determine potential mechanisms of harm. Fifty-one, 10-12 kg purpose-bred beagles were randomized to receive Staphylococcus aureus intrapulmonary challenges or saline followed by CFH infusions (oxyhemoglobin >80%) or placebo. Animals received antibiotics and intensive care support for 96 h. CFH significantly increased mean pulmonary arterial pressures and right ventricular afterload in both septic and nonseptic animals, effects that were significantly greater in nonsurvivors. These findings are consistent with CFH-associated nitric oxide (NO) scavenging and were associated with significantly depressed cardiac function, and worsened shock, lactate levels, metabolic acidosis, and multiorgan failure. In septic animals only, CFH administration significantly increased mean alveolar-arterial oxygenation gradients, also to a significantly greater degree in nonsurvivors. CFH-associated iron levels were significantly suppressed in infected animals, suggesting that bacterial iron uptake worsened pneumonia. Notably, cytokine levels were similar in survivors and nonsurvivors and were not predictive of outcome. In the absence and presence of infection, CFH infusions resulted in pulmonary hypertension, cardiogenic shock, and multiorgan failure, likely through NO scavenging. In the presence of infection alone, CFH infusions worsened oxygen exchange and lung injury, presumably by supplying iron that promoted bacterial growth. CFH elevation, a known consequence of clinical septic shock, adversely impacts sepsis outcomes through more than one mechanism, and is a biologically plausible, nonantibiotic, noncytokine target for therapeutic intervention.NEW & NOTEWORTHY Cell-free hemoglobin (CFH) elevations are a known consequence of clinical sepsis. Using a two-by-two factorial design and extensive physiological and biochemical evidence, we found a direct mechanism of injury related to nitric oxide scavenging leading to pulmonary hypertension increasing right heart afterload, depressed cardiac function, worsening circulatory failure, and death, as well as an indirect mechanism related to iron toxicity. These discoveries alter conventional thinking about septic shock pathogenesis and provide novel therapeutic approaches.

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.

RBC Storage Lesion Studies in Humans and Experimental Models of Shock

The finding of toxicity in a meta-analysis of observational clinical studies of transfused longer stored red blood cells (RBC) and ethical issues surrounding aging blood for human studies prompted us to develop an experimental model of RBC transfusion. Transfusing older RBCs during canine pneumonia increased mortality rates. Toxicity was associated with in vivo hemolysis with release of cell-free hemoglobin (CFH) and iron. CFH can scavenge nitric oxide, causing vasoconstriction and endothelial injury. Iron, an essential bacterial nutrient, can worsen infections. This toxicity was seen at commonly transfused blood volumes (2 units) and was altered by the severity of pneumonia. Washing longer-stored RBCs mitigated these detrimental effects, but washing fresh RBCs actually increased them. In contrast to septic shock, transfused longer stored RBCs proved beneficial in hemorrhagic shock by decreasing reperfusion injury. Intravenous iron was equivalent in toxicity to transfusion of longer stored RBCs and both should be avoided during infection. Storage of longer-stored RBCs at 2 °C instead of higher standard temperatures (4-6 °C) minimized the release of CFH and iron. Haptoglobin, a plasma protein that binds CFH and increases its clearance, minimizes the toxic effects of longer-stored RBCs during infection and is a biologically plausible novel approach to treat septic shock.

Haptoglobin improves shock, lung injury, and survival in canine pneumonia

During the last half-century, numerous antiinflammatory agents were tested in dozens of clinical trials and have proven ineffective for treating septic shock. The observation in multiple studies that cell-free hemoglobin (CFH) levels are elevated during clinical sepsis and that the degree of increase correlates with higher mortality suggests an alternative approach. Human haptoglobin binds CFH with high affinity and, therefore, can potentially reduce iron availability and oxidative activity. CFH levels are elevated over approximately 24-48 hours in our antibiotic-treated canine model of S. aureus pneumonia that simulates the cardiovascular abnormalities of human septic shock. In this 96-hour model, resuscitative treatments, mechanical ventilation, sedation, and continuous care are translatable to management in human intensive care units. We found, in this S. aureus pneumonia model inducing septic shock, that commercial human haptoglobin concentrate infusions over 48-hours bind canine CFH, increase CFH clearance, and lower circulating iron. Over the 96-hour study, this treatment was associated with an improved metabolic profile (pH, lactate), less lung injury, reversal of shock, and increased survival. Haptoglobin binding compartmentalized CFH to the intravascular space. This observation, in combination with increasing CFHs clearance, reduced available iron as a potential source of bacterial nutrition while decreasing the ability for CFH and iron to cause extravascular oxidative tissue injury. In contrast, haptoglobin therapy had no measurable antiinflammatory effect on elevations in proinflammatory C-reactive protein and cytokine levels. Haptoglobin therapy enhances normal host defense mechanisms in contrast to previously studied antiinflammatory sepsis therapies, making it a biologically plausible novel approach to treat septic shock.

Role of heme in lung bacterial infection after trauma hemorrhage and stored red blood cell transfusion: A preclinical experimental study

BACKGROUND

Trauma is the leading cause of death and disability in patients aged 1-46 y. Severely injured patients experience considerable blood loss and hemorrhagic shock requiring treatment with massive transfusion of red blood cells (RBCs). Preclinical and retrospective human studies in trauma patients have suggested that poorer therapeutic efficacy, increased severity of organ injury, and increased bacterial infection are associated with transfusion of large volumes of stored RBCs, although the mechanisms are not fully understood.

METHODS AND FINDINGS

We developed a murine model of trauma hemorrhage (TH) followed by resuscitation with plasma and leukoreduced RBCs (in a 1:1 ratio) that were banked for 0 (fresh) or 14 (stored) days. Two days later, lungs were infected with Pseudomonas aeruginosa K-strain (PAK). Resuscitation with stored RBCs significantly increased the severity of lung injury caused by P. aeruginosa, as demonstrated by higher mortality (median survival 35 h for fresh RBC group and 8 h for stored RBC group; p < 0.001), increased pulmonary edema (mean [95% CI] 106.4 μl [88.5-124.3] for fresh RBCs and 192.5 μl [140.9-244.0] for stored RBCs; p = 0.003), and higher bacterial numbers in the lung (mean [95% CI] 1.2 × 10(7) [-1.0 × 10(7) to 2.5 × 10(7)] for fresh RBCs and 3.6 × 10(7) [2.5 × 10(7) to 4.7 × 10(7)] for stored RBCs; p = 0.014). The mechanism underlying this increased infection susceptibility and severity was free-heme-dependent, as recombinant hemopexin or pharmacological inhibition or genetic deletion of toll-like receptor 4 (TLR4) during TH and resuscitation completely prevented P. aeruginosa-induced mortality after stored RBC transfusion (p < 0.001 for all groups relative to stored RBC group). Evidence from studies transfusing fresh and stored RBCs mixed with stored and fresh RBC supernatants, respectively, indicated that heme arising both during storage and from RBC hemolysis post-resuscitation plays a role in increased mortality after PAK (p < 0.001). Heme also increased endothelial permeability and inhibited macrophage-dependent phagocytosis in cultured cells. Stored RBCs also increased circulating high mobility group box 1 (HMGB1; mean [95% CI] 15.4 ng/ml [6.7-24.0] for fresh RBCs and 50.3 ng/ml [12.3-88.2] for stored RBCs), and anti-HMGB1 blocking antibody protected against PAK-induced mortality in vivo (p = 0.001) and restored macrophage-dependent phagocytosis of P. aeruginosa in vitro. Finally, we showed that TH patients, admitted to the University of Alabama at Birmingham ER between 1 January 2015 and 30 April 2016 (n = 50), received high micromolar-millimolar levels of heme proportional to the number of units transfused, sufficient to overwhelm endogenous hemopexin levels early after TH and resuscitation. Limitations of the study include lack of assessment of temporal changes in different products of hemolysis after resuscitation and the small sample size precluding testing of associations between heme levels and adverse outcomes in resuscitated TH patients.

CONCLUSIONS

We provide evidence that large volume resuscitation with stored blood, compared to fresh blood, in mice increases mortality from subsequent pneumonia, which occurs via mechanisms sensitive to hemopexin and TLR4 and HMGB1 inhibition.

Proceedings of the Food and Drug Administration's public workshop on new red blood cell product regulatory science 2016

The US Food and Drug Administration (FDA) held a workshop on red blood cell (RBC) product regulatory science on October 6 and 7, 2016, at the Natcher Conference Center on the National Institutes of Health (NIH) Campus in Bethesda, Maryland. The workshop was supported by the National Heart, Lung, and Blood Institute, NIH; the Department of Defense; the Office of the Assistant Secretary for Health, Department of Health and Human Services; and the Center for Biologics Evaluation and Research, FDA. The workshop reviewed the status and scientific basis of the current regulatory framework and the available scientific tools to expand it to evaluate innovative and future RBC transfusion products. A full record of the proceedings is available on the FDA website (http://www.fda.gov/BiologicsBloodVaccines/NewsEvents/WorkshopsMeetingsConferences/ucm507890.htm). The contents of the summary are the authors' opinions and do not represent agency policy.

Parenteral irons versus transfused red blood cells for treatment of anemia during canine experimental bacterial pneumonia

BACKGROUND

No studies have been performed comparing intravenous (IV) iron with transfused red blood cells (RBCs) for treating anemia during infection. In a previous report, transfused older RBCs increased free iron release and mortality in infected animals when compared to fresher cells. We hypothesized that treating anemia during infection with transfused fresh RBCs, with minimal free iron release, would prove superior to IV iron therapy.

STUDY DESIGN AND METHODS

Purpose-bred beagles (n = 42) with experimental Staphylococcus aureus pneumonia rendered anemic were randomized to be transfused RBCs stored for 7 days or one of two IV iron preparations (7 mg/kg), iron sucrose, a widely used preparation, or ferumoxytol, a newer formulation that blunts circulating iron levels.

RESULTS

Both irons increased the alveolar-arterial oxygen gradient at 24 to 48 hours (p = 0.02-0.001), worsened shock at 16 hours (p = 0.02-0.003, respectively), and reduced survival (transfusion 56%; iron sucrose 8%, p = 0.01; ferumoxytol 9%, p = 0.04). Compared to fresh RBC transfusion, plasma iron measured by non-transferrin-bound iron levels increased with iron sucrose at 7, 10, 13, 16, 24, and 48 hours (p = 0.04 to p < 0.0001) and ferumoxytol at 7, 24, and 48 hours (p = 0.04 to p = 0.004). No significant differences in cardiac filling pressures or performance, hemoglobin (Hb), or cell-free Hb were observed.

CONCLUSIONS

During canine experimental bacterial pneumonia, treatment of mild anemia with IV iron significantly increased free iron levels, shock, lung injury, and mortality compared to transfusion of fresh RBCs. This was true for iron preparations that do or do not blunt circulating free iron level elevations. These findings suggest that treatment of anemia with IV iron during infection should be undertaken with caution.

The red cell storage lesion(s): of dogs and men

The advent of preservative solutions permitted refrigerated storage of red blood cells. However, the convenience of having red blood cell inventories was accompanied by a disadvantage. Red cells undergo numerous physical and metabolic changes during cold storage, the "storage lesion(s)". Whereas controlled clinical trials have not confirmed the clinical importance of such changes, ethical and operational issues have prevented careful study of the oldest stored red blood cells. Suggestions of toxicity from meta-analyses motivated us to develop pre-clinical canine models to compare the freshest vs the oldest red blood cells. Our model of canine pneumonia with red blood cell transfusion indicated that the oldest red blood cells increased mortality, that the severity of pneumonia is important, but that the dose of transfused red blood cells is not. Washing the oldest red blood cells reduces mortality by removing senescent cells and remnants, whereas washing fresher cells increases mortality by damaging the red blood cell membrane. An opposite effect was found in a model of haemorrhagic shock with reperfusion injury. Physiological studies indicate that release of iron from old cells is a primary mechanism of toxicity during infection, whereas scavenging of cell-free haemoglobin may be beneficial during reperfusion injury. Intravenous iron appears to have toxicity equivalent to old red blood cells in the pneumonia model, suggesting that intravenous iron and old red blood cells should be administered with caution to infected patients.

Haptoglobin or Hemopexin Therapy Prevents Acute Adverse Effects of Resuscitation After Prolonged Storage of Red Cells

BACKGROUND

Extracellular hemoglobin and cell-free heme are toxic breakdown products of hemolyzed erythrocytes. Mammals synthesize the scavenger proteins haptoglobin and hemopexin, which bind extracellular hemoglobin and heme, respectively. Transfusion of packed red blood cells is a lifesaving therapy for patients with hemorrhagic shock. Because erythrocytes undergo progressive deleterious morphological and biochemical changes during storage, transfusion of packed red blood cells that have been stored for prolonged intervals (SRBCs; stored for 35-40 days in humans or 14 days in mice) increases plasma levels of cell-free hemoglobin and heme. Therefore, in patients with hemorrhagic shock, perfusion-sensitive organs such as the kidneys are challenged not only by hypoperfusion but also by the high concentrations of plasma hemoglobin and heme that are associated with the transfusion of SRBCs.

METHODS

To test whether treatment with exogenous human haptoglobin or hemopexin can ameliorate adverse effects of resuscitation with SRBCs after 2 hours of hemorrhagic shock, mice that received SRBCs were given a coinfusion of haptoglobin, hemopexin, or albumin.

RESULTS

Treatment with haptoglobin or hemopexin but not albumin improved the survival rate and attenuated SRBC-induced inflammation. Treatment with haptoglobin retained free hemoglobin in the plasma and prevented SRBC-induced hemoglobinuria and kidney injury. In mice resuscitated with fresh packed red blood cells, treatment with haptoglobin, hemopexin, or albumin did not cause harmful effects.

CONCLUSIONS

In mice, the adverse effects of transfusion with SRBCs after hemorrhagic shock are ameliorated by treatment with either haptoglobin or hemopexin. Haptoglobin infusion prevents kidney injury associated with high plasma hemoglobin concentrations after resuscitation with SRBCs. Treatment with the naturally occurring human plasma proteins haptoglobin or hemopexin may have beneficial effects in conditions of severe hemolysis after prolonged hypotension.