Effects of storage-aged red blood cell transfusions on endothelial function in hospitalized patients

Vesiculation of Red Blood Cells in the Blood Bank: A Multi-Omics Approach towards Identification of Causes and Consequences

Microvesicle generation is an integral part of the aging process of red blood cells in vivo and in vitro. Extensive vesiculation impairs function and survival of red blood cells after transfusion, and microvesicles contribute to transfusion reactions. The triggers and mechanisms of microvesicle generation are largely unknown. In this study, we combined morphological, immunochemical, proteomic, lipidomic, and metabolomic analyses to obtain an integrated understanding of the mechanisms underlying microvesicle generation during the storage of red blood cell concentrates. Our data indicate that changes in membrane organization, triggered by altered protein conformation, constitute the main mechanism of vesiculation, and precede changes in lipid organization. The resulting selective accumulation of membrane components in microvesicles is accompanied by the recruitment of plasma proteins involved in inflammation and coagulation. Our data may serve as a basis for further dissection of the fundamental mechanisms of red blood cell aging and vesiculation, for identifying the cause-effect relationship between blood bank storage and transfusion complications, and for assessing the role of microvesicles in pathologies affecting red blood cells.

Storage time of red blood cells among ICU patients with septic shock

BACKGROUND

We aimed to describe the exposure to blood transfusions and mortality among patients with septic shock.

METHODS

We did a retrospective cohort study of two cohorts-patients with septic shock registered in a Danish ICU database (2008-2010) and patients from the Transfusion Requirements in Septic Shock (TRISS) trial (2011-2013). We extracted information on blood transfusions issued to all patients. We investigated the number of patients receiving very fresh blood (less than 7 days), very old blood (more than 24 days) and blood with a mixture of storage time.

RESULTS

In the Danish cohort, 1637 patients were included of whom 1394 (85%) received 20,239 blood units from 14 days prior the ICU admission to 90 days after; 33% were transfused before, 77% in the ICU and 36% after ICU. The exposure to exclusively very fresh or very old blood was 3% and 4%, respectively. In the TRISS cohort, 77% of the 937 patients received 5047 RBC units; 3% received exclusively very fresh and 13% very old blood. The point estimate of mortality was higher among patients receiving large amounts of exclusively very fresh and very old blood, but the number of patients were very small.

CONCLUSIONS

Patients with septic shock were transfused both before and after ICU. Exposure to blood of less than 7 days or more than 24 days old were limited. We were not able to detect higher mortality among the limited number of patients with septic shock transfused with very fresh or very old blood.

Total plasma heme concentration increases after red blood cell transfusion and predicts mortality in critically ill medical patients

BACKGROUND

Relationships between red blood cell (RBC) transfusion, circulating cell-free heme, and clinical outcomes in critically ill transfusion recipients are incompletely understood. The goal of this study was to determine whether total plasma heme increases after RBC transfusion and predicts mortality in critically ill patients.

STUDY DESIGN AND METHODS

This was a prospective cohort study of 111 consecutive medical intensive care patients requiring RBC transfusion. Cell-free heme was measured in RBC units before transfusion and in the patients' plasma before and after transfusion.

RESULTS

Total plasma heme levels increased in response to transfusion, from a median (interquartile range [IQR]) of 35 (26-76) μmol/L to 47 (35-73) μmol/L (p < 0.001). Posttransfusion total plasma heme was higher in nonsurvivors (54 [35-136] μmol/L) versus survivors (44 [31-65] μmol/L, p = 0.03). Posttransfusion total plasma heme predicted hospital mortality (odds ratio [95% confidence interval] per quartile increase in posttransfusion plasma heme, 1.76 [1.17-2.66]; p = 0.007). Posttransfusion total plasma heme was not correlated with RBC unit storage duration and weakly correlated with RBC unit cell-free heme concentration.

CONCLUSIONS

Total plasma heme concentration increases in critically ill patients after RBC transfusion and is independently associated with mortality. This transfusion-associated increase in total plasma heme is not fully explained by RBC unit storage age or cell-free heme content. Additional studies are warranted to define mechanisms of transfusion-related plasma heme accumulation and test prevention strategies.

Red blood cell storage lesion: causes and potential clinical consequences

Red blood cells (RBCs) are a specialised organ that enabled the evolution of multicellular organisms by supplying a sufficient quantity of oxygen to cells that cannot obtain oxygen directly from ambient air via diffusion, thereby fueling oxidative phosphorylation for highly efficient energy production. RBCs have evolved to optimally serve this purpose by packing high concentrations of haemoglobin in their cytosol and shedding nuclei and other organelles. During their circulatory lifetimes in humans of approximately 120 days, RBCs are poised to transport oxygen by metabolic/redox enzymes until they accumulate damage and are promptly removed by the reticuloendothelial system. These elaborate evolutionary adaptions, however, are no longer effective when RBCs are removed from the circulation and stored hypothermically in blood banks, where they develop storage-induced damages ("storage lesions") that accumulate over the shelf life of stored RBCs. This review attempts to provide a comprehensive view of the literature on the subject of RBC storage lesions and their purported clinical consequences by incorporating the recent exponential growth in available data obtained from "omics" technologies in addition to that published in more traditional literature. To summarise this vast amount of information, the subject is organised in figures with four panels: i) root causes; ii) RBC storage lesions; iii) physiological effects; and iv) reported outcomes. The driving forces for the development of the storage lesions can be roughly classified into two root causes: i) metabolite accumulation/depletion, the target of various interventions (additive solutions) developed since the inception of blood banking; and ii) oxidative damages, which have been reported for decades but not addressed systemically until recently. Downstream physiological consequences of these storage lesions, derived mainly by in vitro studies, are described, and further potential links to clinical consequences are discussed. Interventions to postpone the onset and mitigate the extent of the storage lesion development are briefly reviewed. In addition, we briefly discuss the results from recent randomised controlled trials on the age of stored blood and clinical outcomes of transfusion.

Effects of shorter versus longer storage time of transfused red blood cells in adult ICU patients: a systematic review with meta-analysis and Trial Sequential Analysis

PURPOSE

Patients in the intensive care unit (ICU) are often transfused with red blood cells (RBC). During storage, the RBCs and storage medium undergo changes, which may have clinical consequences. Several trials now have assessed these consequences, and we reviewed the present evidence on the effects of shorter versus longer storage time of transfused RBCs on outcomes in ICU patients.

METHODS

We conducted a systematic review with meta-analyses and trial sequential analyses (TSA) of randomised clinical trials including adult ICU patients transfused with fresher versus older or standard issue blood.

RESULTS

We included seven trials with a total of 18,283 randomised ICU patients; two trials of 7504 patients were judged to have low risk of bias. We observed no effects of fresher versus older blood on death (relative risk 1.04, 95% confidence interval (CI) 0.97-1.11; 7349 patients; TSA-adjusted CI 0.93-1.15), adverse events (1.26, 0.76-2.09; 7332 patients; TSA-adjusted CI 0.16-9.87) or post-transfusion infections (1.07, 0.96-1.20; 7332 patients; TSA-adjusted CI 0.90-1.27). The results were unchanged by including trials with high risk of bias. TSA confirmed the results and the required information size was reached for mortality for a relative risk change of 20%.

CONCLUSIONS

We may be able to reject a clinically meaningful effect of RBC storage time on mortality in transfused adult ICU patients as our trial sequential analyses reject a 10% relative risk change in death when comparing fresher versus older blood for transfusion.

Peritransplantation Red Blood Cell Transfusion Is Associated with Increased Risk of Graft-versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation

More than 90% of allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients receive red blood cell (RBC) or platelet transfusions in the peritransplantation period. We tested the hypothesis that transfusions are associated with the development of severe (grade III-IV) acute graft-versus-host disease (aGVHD) or mortality after allo-HSCT in a retrospective study of 322 consecutive patients receiving an allogeneic bone marrow or granulocyte colony-stimulating factor-mobilized blood stem cell graft for a hematologic malignancy. Counting transfused RBC and platelet units between day -7 pretransplantation and day +27 post-transplantation, but excluding transfusions administered after a diagnosis of aGVHD, yielded medians of 5 RBC units and 2 platelet units transfused. Sixty-three patients (20%) developed a maximal grade III-IV aGVHD with onset up to day +150 post-transplantation (median aGVHD onset of 28 days). HLA mismatch (hazard ratio [HR], 2.4; 95% confidence interval [CI], 1.2 to 4.7; P = .01), and transfusion of more than the median number of RBC units (HR, 2.1; 95% CI, 1.1 to 3.7; P = .02) were independently associated with greater risk of grade III-IV aGVHD in a multivariable analysis model. Disease risk strata (HR, 1.7; 95% CI, 1.2 to 2.4 for high risk versus low risk; P = .005) and transfusion of more than the median number of RBC units (HR, 1.4; 95% CI, 1.0 to 2.0; P = .054) were independently associated with inferior overall survival. These data support our hypothesis that peritransplantation RBC transfusions are associated with the risk of developing severe aGVHD and worse overall survival following allo-HSCT, and suggest that strategies to reduce routine RBC transfusion may favorably reduce the incidence and severity of GVHD.

Exposure of Stored Packed Erythrocytes to Nitric Oxide Prevents Transfusion-associated Pulmonary Hypertension

BACKGROUND

Transfusion of packed erythrocytes stored for a long duration is associated with increased pulmonary arterial pressure and vascular resistance. Prolonged storage decreases erythrocyte deformability, and older erythrocytes are rapidly removed from the circulation after transfusion. The authors studied whether treating stored packed ovine erythrocytes with NO before transfusion could prevent pulmonary vasoconstriction, enhance erythrocyte deformability, and prolong erythrocyte survival after transfusion.

METHODS

Ovine leukoreduced packed erythrocytes were treated before transfusion with either NO gas or a short-lived NO donor. Sheep were transfused with autologous packed erythrocytes, which were stored at 4°C for either 2 ("fresh blood") or 40 days ("stored blood"). Pulmonary and systemic hemodynamic parameters were monitored before, during, and after transfusion. Transfused erythrocytes were labeled with biotin to measure their circulating lifespan. Erythrocyte deformability was assessed before and after NO treatment using a microfluidic device.

RESULTS

NO treatment improved the deformability of stored erythrocytes and increased the number of stored erythrocytes circulating at 1 and 24 h after transfusion. NO treatment prevented transfusion-associated pulmonary hypertension (mean pulmonary arterial pressure at 30 min of 21 ± 1 vs. 15 ± 1 mmHg in control and NO-treated packed erythrocytes, P < 0.0001). Washing stored packed erythrocytes before transfusion did not prevent pulmonary hypertension.

CONCLUSIONS

NO treatment of stored packed erythrocytes before transfusion oxidizes cell-free oxyhemoglobin to methemoglobin, prevents subsequent NO scavenging in the pulmonary vasculature, and limits pulmonary hypertension. NO treatment increases erythrocyte deformability and erythrocyte survival after transfusion. NO treatment might provide a promising therapeutic approach to prevent pulmonary hypertension and extend erythrocyte survival.

Trans-kingdom small RNA transfer during host-pathogen interactions: The case of P. falciparum and erythrocytes

This review focuses on the role of trans-kingdom movement of small RNA (sRNA) molecules between parasites, particularly Plasmodium falciparum, and their respective host cells. While the intercellular transfer of sRNAs within organisms is well recognized, recent studies illustrate many examples of trans-kingdom sRNA exchange within the context of host-parasite interactions. These interactions are predominantly found in the transfer of host sRNAs between erythrocytes and the invading P. falciparum, as well as other host cell types. In addition, parasite-encoded sRNAs can also be transferred to host cells to evade the immune system. The transport of these parasite sRNAs in the body fluids of the host may also offer means to detect and monitor the parasite infection. These isolated examples may only represent the tip of the iceberg in which the transfer of sRNA between host and parasites is a critical aspect of host-pathogen interactions. In addition, the levels of these sRNAs and their speed of transfer may vary dramatically under different contexts to push the biologic equilibrium toward the benefit of hosts vs. parasites. Therefore, these sRNA transfers may offer potential strategies to detect, prevent or treat parasite infections. Here, we review a brief history of the discovery of host erythrocyte sRNAs, their transfers and interactions in the context of P. falciparum infection. We also provide examples and discuss the functional significance of the reciprocal transfer of parasite-encoded sRNAs into hosts. These understandings of sRNA exchanges are put in the context of their implications for parasite pathogenesis, host defenses and the evolution of host polymorphisms driven by host interactions with these parasites.

B-type natriuretic peptide and plasma hemoglobin levels following transfusion of shorter-storage versus longer-storage red blood cells: Results from the TOTAL randomized trial

BACKGROUND

Prior studies have suggested that transfusion of stored red blood cells (RBCs) with increased levels of cell-free hemoglobin might reduce the bioavailability of recipient nitric oxide (NO) and cause myocardial strain.

METHODS

Ugandan children (ages 6-60 months) with severe anemia and lactic acidosis were randomly assigned to receive RBCs stored 1-10 days versus 25-35 days. B-type natriuretic peptide (BNP), vital signs, renal function test results, and plasma hemoglobin were measured. Most children had either malaria or sickle cell disease and were thus at risk for reduced NO bioavailability.

RESULTS

Seventy patients received RBCs stored 1-10 days, and 77 received RBCs stored 25-35 days. The median (interquartile range) cell-free hemoglobin was nearly 3 times higher in longer-storage RBCs (26.4 [15.5-43.4] μmol/L) than in shorter-storage RBCs (10.8 [7.8-18.6] μmol/L), P < .0001. Median (interquartile range) BNP 2 hours posttransfusion was 156 (59-650) pg/mL (shorter storage) versus 158 (59-425) pg/mL (longer storage), P = .76. BNP values 22 hours posttransfusion were 110 (46-337) pg/mL (shorter storage) versus 96 (49-310) pg/mL (longer storage), P = .76. Changes in BNP within individuals from pretransfusion to 2 hours (or 22 hours) posttransfusion were not significantly different between the study groups. BNP change following transfusion did not correlate with the concentration of cell-free hemoglobin in the RBC supernatant. Blood pressure, blood urea nitrogen, creatinine, and change in plasma hemoglobin were not significantly different in the 2 groups.

CONCLUSION

In a randomized trial among children at risk for reduced NO bioavailability, we found that BNP, blood pressure, creatinine, and plasma hemoglobin were not higher in patients receiving RBCs stored for 25-35 versus 1-10 days.

Hematological disorders and pulmonary hypertension

Pulmonary hypertension (PH), a serious disorder with a high morbidity and mortality rate, is known to occur in a number of unrelated systemic diseases. Several hematological disorders such as sickle cell disease, thalassemia and myeloproliferative diseases develop PH which worsens the prognosis. Associated oxidant injury and vascular inflammation cause endothelial damage and dysfunction. Pulmonary vascular endothelial damage/dysfunction is an early event in PH resulting in the loss of vascular reactivity, activation of proliferative and antiapoptotic pathways leading to vascular remodeling, elevated pulmonary artery pressure, right ventricular hypertrophy and premature death. Hemolysis observed in hematological disorders leads to free hemoglobin which rapidly scavenges nitric oxide (NO), limiting its bioavailability, and leading to endothelial dysfunction. In addition, hemolysis releases arginase into the circulation which converts L-arginine to ornithine, thus bypassing NO production. Furthermore, treatments for hematological disorders such as immunosuppressive therapy, splenectomy, bone marrow transplantation, and radiation have been shown to contribute to the development of PH. Recent studies have shown deregulated iron homeostasis in patients with cardiopulmonary diseases including pulmonary arterial hypertension (PAH). Several studies have reported low iron levels in patients with idiopathic PAH, and iron deficiency is an important risk factor. This article reviews PH associated with hematological disorders and its mechanism; and iron homeostasis and its relevance to PH.

Effect of Transfusion Strategy in Acute Non-variceal Upper Gastrointestinal Bleeding: A Nationwide Study of 5861 Hospital Admissions in Denmark

BACKGROUND

Acute non-variceal upper gastrointestinal bleeding (NVUGIB) is a common cause of admissions as well as aggressive transfusion of blood products. Whether the transfusion strategy in NVUGIB impacts on hemostasis is unknown and constitutes the focus of this study.

METHOD

Retrospective analysis of all hospital admissions in Denmark between 2011 and 2013 where hemostatic endoscopic interventions in either the stomach or duodenum had been employed. Regression modeling was used to predict the effect of units transfused of packed red blood cells (PRBC), fresh frozen plasma (FFP), and platelets (PLT) on primary outcome 30-day mortality as well as secondary hemostasis-related outcomes and need for re-endoscopy and conversion to surgery. The model was corrected for confounders, including transfusion of other blood products (PRBC, FFP, and PLT, respectively), patient age as well as pre-existing medical conditions.

RESULTS

5107 patients received 10783 therapeutic endoscopic interventions. Units of PRBC transfused were identified as a predictor of re-endoscopy, surgery, and 30-day mortality with odds ratio (OR) 1.08 (1.06-1.09, p < 0.01), 1.05 (1.03-1.07, p < 0.01), and 1.04 (1.01-1.06, p < 0.01), respectively. Units of FFP transfused were associated with a higher risk of surgery and 30-day mortality with OR 1.05 (1.02-1.08, p < 0.01) and 1.04 (1.02-1.07, p < 0.01), respectively. Units of PLTs transfused were independently associated with a reduction in risk of re-endoscopy 0.93 (0.87-0.98, p = 0.02). A high ratio of PRBC:FFP:PLT (1:1:1) was associated with reduced need for re-endoscopy OR 0.23 (0.06-0.67, p = 0.01) but increased mortality with OR 3.60 (1.34-11.38, p = 0.02).

CONCLUSION

PRBC transfusion was associated with adverse events, including 30-day mortality and failure of hemostasis. In contrast, transfusion of PLT was associated with a reduction in need for re-endoscopy.

The effect of fresh versus standard blood transfusion on microvascular endothelial function

BACKGROUND

The duration of red blood cell (RBC) storage may have a negative impact on endothelial nitric oxide bioavailability. We tested the hypothesis that transfused fresh blood will have a more favorable effect on microvascular endothelial function as compared to older standard issue blood.

METHODS

Participants requiring chronic RBC transfusions were enrolled in a crossover design study to receive fresh (<7 days of storage) or standard (up to 42 days of storage) blood on 2 separate visits. Endothelial function was assessed by reactive hyperemia peripheral arterial tonometry that was measured before and after transfusions. For each participant, the difference between endothelial function pretransfusion and posttransfusion was assessed in relation to blood storage time.

RESULTS

Twenty-one patients (71 ± 16 years, 52% females) were enrolled. Mean age of fresh blood was 5.5 days (±1.0), and that of standard blood was 24.5 days (±7.9 days). The pretransfusion hemoglobin was 83.1 ± 2.5 g/L; and posttransfusion, 98.9 ± 2.6 g/L. An average of 2 U of packed RBCs was transfused. Microvascular endothelial function decreased more frequently after transfusion of standard blood compared to fresh blood. Standard issue blood transfusion was associated with decrease in reactive hyperemia peripheral arterial tonometry index (-0.25 ± 0.63) compared to fresh blood (+0.03 ± 0.49); P = .026.

CONCLUSION

Transfusions of standard issue blood are associated with less favorable effect on microvascular endothelial function as compared to fresh blood.

Impact of aspirin use on morbidity and mortality in massively transfused cardiac surgery patients: a propensity score matched cohort study

PURPOSE

Aspirin may prevent organ dysfunction in critically ill patients and mitigate transfusion associated acute lung injury. We hypothesized that aspirin use might be associated with decreased morbidity and mortality in massively transfused cardiac surgery patients.

METHODS

A single center retrospective cohort study was performed using data from an 8.5-year period (2006-2014). Massive transfusion was defined as receiving at least 2400 ml (8 units) of red blood cell units intraoperatively. A propensity score model was created to account for the likelihood of receiving aspirin and matched pairs were identified using global optimal matching. The primary endpoint, in-hospital mortality, was compared between aspirin users and non-users. Secondary outcomes including: ICU hours, mechanical lung ventilation hours, prolonged mechanical lung ventilation (>24 h), pneumonia, stroke, acute renal failure, atrial fibrillation, deep sternal wound infection, and multiple organ dysfunction syndrome were also compared.

RESULTS

Of 7492 cardiac surgery patients, 452 (6 %) were massively transfused and mortality was 30.6 %. There were 346 patients included in the matched cohort. No significant association was found between preoperative aspirin use and in-hospital mortality; absolute risk reduction with aspirin = 7.5 % (95 % CI -2.0 to 16.9 %, p = 0.12). Preoperative aspirin use was associated with fewer total mechanical lung ventilation hours (p = 0.02) and less prolonged mechanical lung ventilation; absolute risk reduction = 11.0 % (95 % CI 1.1-20.5 %, p = 0.02).

CONCLUSIONS

Preoperative aspirin use is not associated with decreased in-hospital mortality in massively transfused cardiac surgery patients, but may be associated with less mechanical lung ventilation time.

Acid Sphingomyelinase Inhibition Prevents Hemolysis During Erythrocyte Storage

Background/Aims

During storage, units of human red blood cells (pRBCs) experience membrane destabilization and hemolysis which may cause harm to transfusion recipients. This study investigates whether inhibition of acid sphingomyelinase could stabilize erythrocyte membranes and prevent hemolysis during storage.

Methods

Human and murine pRBCs were stored under standard blood banking conditions with and without the addition of amitriptyline, a known acid sphingomyelinase inhibitor. Hemoglobin was measured with an electronic hematology analyzer and flow cytometry was used to measure erythrocyte size, complexity, phosphatidylserine externalization, and band 3 protein expression.

Results

Cell-free hemoglobin, a marker of hemolysis, increased during pRBC storage. Amitriptyline treatment decreased hemolysis in a dose-dependent manner. Standard pRBC storage led to loss of erythrocyte size and membrane complexity, increased phosphatidylserine externalization, and decreased band 3 protein integrity as determined by flow cytometry. Each of these changes was reduced by treatment with amitriptyline. Transfusion of amitriptyline-treated pRBCs resulted in decreased circulating free hemoglobin.

Conclusion

Erythrocyte storage is associated with changes in cell size, complexity, membrane molecular composition, and increased hemolysis. Acid sphingomyelinase inhibition reduced these changes in a dose-dependent manner. Our data suggest a novel mechanism to attenuate the harmful effects after transfusion of aged blood products.

The Effect of Red Blood Cell Transfusion on Cerebral Autoregulation in Patients with Severe Traumatic Brain Injury

BACKGROUND

Red blood cell (RBC) transfusion is associated with inconsistent changes in brain tissue oxygenation (PbO2). Previous studies have failed to consider alterations in cerebral autoregulation. Our objective was to investigate the effect of RBC transfusion on cerebral autoregulation, as measured by pressure reactivity index (PRx).

METHODS

Retrospective analysis of 28 severe traumatic brain injury (TBI) patients from a prospective registry between 2007 and 2014. We recorded hemoglobin (Hb) concentration, intracranial pressure, PbO2, cerebral perfusion pressure, PRx, and cerebral lactate/pyruvate ratio for 6 h before and after RBC transfusion. We also recorded body temperature, PaO2, PCO2, pH, and fraction of inspired oxygen. Subgroups of normoxia (PbO2 >20 mmHg) and hypoxia (PbO2 <20 mmHg) prior to transfusion were defined a priori.

RESULTS

The median age was 36 years [interquartile range (IQR) 27-49], 32% were female. The median admission Glasgow Coma score was 5 (IQR 4-9) and injury severity score was 16 (IQR 9-21). Overall, mean Hb concentration [80 g/L (SD 7) to 89 g/L (SD 8), p < 0.001] and PbO2 increased [23.5 mmHg (SD 8) to 25.0 mmHg (SD 9), p = 0.033] following transfusion. PRx increased post-transfusion [0.028 (SD 0.29) to 0.11 (SD 0.24), p = 0.034], indicating worsening cerebrovascular pressure reactivity. In patients with mean PbO2 >20 mmHg pre-transfusion (n = 20), the PRx increased significantly [-0.052 (SD 0.24) to 0.079 (SD 0.22), p = 0.007] but did not change in patients with PbO2 <20 mmHg: PRx [0.22 (SD 0.34) to 0.18 (SD 0.30), p = 0.36].

CONCLUSION

RBC transfusion in severe TBI patients results in worsening PRx, indicating impaired cerebral autoregulation.

Effects of Aged Stored Autologous Red Blood Cells on Human Endothelial Function

RATIONALE

A major abnormality that characterizes the red cell "storage lesion" is increased hemolysis and reduced red cell lifespan after infusion. Low levels of intravascular hemolysis after transfusion of aged stored red cells disrupt nitric oxide (NO) bioavailabity, via accelerated NO scavenging reaction with cell-free plasma hemoglobin. The degree of intravascular hemolysis post-transfusion and effects on endothelial-dependent vasodilation responses to acetylcholine have not been fully characterized in humans.

OBJECTIVES

To evaluate the effects of blood aged to the limits of Food and Drug Administration-approved storage time on the human microcirculation and endothelial function.

METHODS

Eighteen healthy individuals donated 1 U of leukopheresed red cells, divided and autologously transfused into the forearm brachial artery 5 and 42 days after blood donation. Blood samples were obtained from stored blood bag supernatants and the antecubital vein of the infusion arm. Forearm blood flow measurements were performed using strain-gauge plethysmography during transfusion, followed by testing of endothelium-dependent blood flow with increasing doses of intraarterial acetylcholine.

MEASUREMENTS AND MAIN RESULTS

We demonstrate that aged stored blood has higher levels of arginase-1 and cell-free plasma hemoglobin. Compared with 5-day blood, the transfusion of 42-day packed red cells decreases acetylcholine-dependent forearm blood flows. Intravascular venous levels of arginase-1 and cell-free plasma hemoglobin increase immediately after red cell transfusion, with more significant increases observed after infusion of 42-day-old blood.

CONCLUSIONS

We demonstrate that the transfusion of blood at the limits of Food and Drug Administration-approved storage has a significant effect on the forearm circulation and impairs endothelial function. Clinical trial registered with www.clinicaltrials.gov (NCT 01137656).

Molecular mechanisms of erythrocyte aging

Anemia and hemorrhagic shock are leading causes of morbidity and mortality worldwide, and transfusion of human blood products is the ideal treatment for these conditions. As human erythrocytes age during storage in blood banks they undergo many biochemical and structural changes, termed the red blood cell 'storage lesion'. Specifically, ATP and pH levels decrease as metabolic end products, oxidative stress, cytokines, and cell-free hemoglobin increase. Also, membrane proteins and lipids undergo conformational and organizational changes that result in membrane loss, viscoelastic changes and microparticle formation. As a result, transfusion of aged blood is associated with a host of adverse consequences such as decreased tissue perfusion, increased risk of infection, and increased mortality. This review summarizes current research detailing the known parts of the erythrocyte storage lesion and their physiologic consequences.

Storage lesion: History and perspectives

Red blood cell concentrates (RBCCs) are the major labile blood component transfused worldwide to rescue severe anemia symptoms. RBCCs are frequently stored in additive solutions at 4 °C for up to 42 d, which induces cellular lesion and alters red blood cell metabolism, protein content, and rheological properties. There exists a hot debate surrounding the impact of storage lesion, with some uncertainty regarding how RBCC age may impact transfusion-related adverse clinical outcomes. Several studies show a tendency for poorer outcomes to occur in patients receiving older blood products; however, no clear significant association has yet been demonstrated. Some age-related RBCC alterations prove reversible, while other changes are irreversible following protein oxidation. It is likely that any irreversible damage affects the blood component quality and thus the transfusion efficiency. The present paper aims to promote a better understanding of the occurrence of red blood cell storage lesion, with particular focus on biochemical changes and microvesiculation, through a discussion of the historical advancement of blood transfusion processes.

Predicting storage-dependent damage to red blood cells using nitrite oxidation kinetics, peroxiredoxin-2 oxidation, and hemoglobin and free heme measurements

BACKGROUND

Storage-dependent damage to red blood cells (RBCs) varies significantly. Identifying RBC units that will undergo higher levels of hemolysis during storage may allow for more efficient inventory management decision-making. Oxidative-stress mediates storage-dependent damage to RBCs and will depend on the oxidant:antioxidant balance. We reasoned that this balance or redox tone will serve as a determinant of how a given RBC unit stores and that its assessment in "young" RBCs will predict storage-dependent hemolysis.

STUDY DESIGN AND METHODS

RBCs were sampled from bags and segments stored for 7 to 42 days. Redox tone was assessed by nitrite oxidation kinetics and peroxiredoxin-2 (Prx-2) oxidation. In parallel, hemolysis was assessed by measuring cell-free hemoglobin (Hb) and free heme (hemin). Correlation analyses were performed to determine if Day 7 measurements predicted either the level of hemolysis at Day 35 or the increase in hemolysis during storage.

RESULTS

Higher Day 7 Prx-2 oxidation was associated with higher Day 35 Prx-2 oxidation, suggesting that early assessment of this variable may identify RBCs that will incur the most oxidative damage during storage. RBCs that oxidized nitrite faster on Day 7 were associated with the greatest levels of storage-dependent hemolysis and increases in Prx-2 oxidation. An inverse relationship between storage-dependent changes in oxyhemoglobin and free heme was observed underscoring an unappreciated reciprocity between these molecular species. Moreover, free heme was higher in the bag compared to paired segments, with opposite trends observed for free Hb.

CONCLUSION

Measurement of Prx-2 oxidation and nitrite oxidation kinetics early during RBC storage may predict storage-dependent damage to RBC including hemolysis-dependent formation of free Hb and heme.

Established and theoretical factors to consider in assessing the red cell storage lesion

The collection and storage of red blood cells (RBCs) is a logistical necessity to provide sufficient blood products. However, RBC storage is an unnatural state, resulting in complicated biological changes, referred to collectively as the "storage lesion." Specifics of the storage lesion have been studied for decades, including alterations to cellular properties, morphology, molecular biology of carbohydrates, proteins and lipids, and basic metabolism. Recently, mass spectrometry-based "omics" technology has been applied to the RBC storage lesion, resulting in many new observations, the initial effects of which are more information than understanding. Meanwhile, clinical research on RBC transfusion is considering both the efficacy and also the potential untoward effects of transfusing stored RBCs of different ages and storage conditions. The myriad biological changes that have now been observed during the storage lesion have been extensively reviewed elsewhere. This article focuses rather on an analysis of our current understanding of the biological effects of different elements of the storage lesion, in the context of evolving new clinical understanding. A synopsis is presented of both established and theoretical considerations of the RBC storage lesion and ongoing efforts to create a safer and more efficacious product.