Bad blood: the risks of red cell storage

Functional effects of an African glucose-6-phosphate dehydrogenase (G6PD) polymorphism (Val68Met) on red blood cell hemolytic propensity and post-transfusion recovery

BACKGROUND

Donor genetic variation is associated with red blood cell (RBC) storage integrity and post-transfusion recovery. Our previous large-scale genome-wide association study demonstrated that the African G6PD deficient A- variant (rs1050828, Val68Met) is associated with higher oxidative hemolysis after cold storage. Despite a high prevalence of X-linked G6PD mutation in African American population (>10%), blood donors are not routinely screened for G6PD status and its importance in transfusion medicine is relatively understudied.

STUDY DESIGN AND METHODS

To further evaluate the functional effects of the G6PD A- mutation, we created a novel mouse model carrying this genetic variant using CRISPR-Cas9. We hypothesize that this humanized G6PD A- variant is associated with reduced G6PD activity with a consequent effect on RBC hemolytic propensity and post-transfusion recovery.

RESULTS

G6PD A- RBCs had reduced G6PD protein with ~5% residual enzymatic activity. Significantly increased in vitro hemolysis induced by oxidative stressors was observed in fresh and stored G6PD A- RBCs, along with a lower GSH:GSSG ratio. However, no differences were observed in storage hemolysis, osmotic fragility, mechanical fragility, reticulocytes, and post-transfusion recovery. Interestingly, a 14% reduction of 24-h survival following irradiation was observed in G6PD A- RBCs compared to WT RBCs. Metabolomic assessment of stored G6PD A- RBCs revealed an impaired pentose phosphate pathway (PPP) with increased glycolytic flux, decreasing cellular antioxidant capacity.

DISCUSSION

This novel mouse model of the common G6PD A- variant has impaired antioxidant capacity like humans and low G6PD activity may reduce survival of transfused RBCs when irradiation is performed.

Adverse effects of microparticles on transfusion of stored red blood cell concentrates

BACKGROUND

Systemic and pulmonary coagulopathy and inflammation are important characteristics of transfusion-related acute lung injury (TRALI). Whether microparticles that accumulate in transfused red blood cell concentrates (RBCs) have proinflammatory and procoagulant potential and contribute to adverse reactions of RBC transfusions is unclear.

AIM

To investigate the ability of microparticles in stored RBCs to promote thrombin generation and induce human pulmonary microvascular endothelial cell (HMVEC) activation and damage.

METHODS

The number and size of microparticles were determined by flow cytometric and nanoparticle tracking analyses, respectively. Thrombin generation and the intrinsic coagulation pathway were assayed by a calibrated automated thrombogram and by measuring activated partial thromboplastin time (aPTT), respectively. The expression of ICAM-1 and the release of cytokines by endothelial cells were detected by flow cytometric analyses. HMVEC damage was assessed by incubating lipopolysaccharide-activated endothelial cells with MP-primed polymorphonuclear neutrophils (PMNs).

RESULTS

The size of the microparticles in the RBC supernatant was approximately 100-300 nm. Microparticles promoted thrombin generation in a dose-dependent manner and the aPTT was shortened. Depleting microparticles from the supernatant of RBCs stored for 35 days by either filtration or centrifugation significantly decreased the promotion of thrombin generation. The expression of ICAM-1 on HMVECs was increased significantly by incubation with isolated microparticles. Furthermore, microparticles induced the release of interleukin-6 (IL-6) and interleukin-8 (IL-8) from HMVECs. Microparticles induced lipopolysaccharide-activated HMVEC damage by priming PMNs, but this effect was prevented by inhibiting the PMNs respiratory burst with apocynin.

CONCLUSION

Microparticles in stored RBCs promote thrombin generation, HMVEC activation and damage which may be involved in TRALI development.

Assessment of stored red blood cells through lab-on-a-chip technologies for precision transfusion medicine

Transfusion of red blood cells (RBCs) is one of the most valuable and widespread treatments in modern medicine. Lifesaving RBC transfusions are facilitated by the cold storage of RBC units in blood banks worldwide. Currently, RBC storage and subsequent transfusion practices are performed using simplistic workflows. More specifically, most blood banks follow the "first-in-first-out" principle to avoid wastage, whereas most healthcare providers prefer the "last-in-first-out" approach simply favoring chronologically younger RBCs. Neither approach addresses recent advances through -omics showing that stored RBC quality is highly variable depending on donor-, time-, and processing-specific factors. Thus, it is time to rethink our workflows in transfusion medicine taking advantage of novel technologies to perform RBC quality assessment. We imagine a future where lab-on-a-chip technologies utilize novel predictive markers of RBC quality identified by -omics and machine learning to usher in a new era of safer and precise transfusion medicine.

Measuring Mitochondrial Oxygen Tension during Red Blood Cell Transfusion in Chronic Anemia Patients: A Pilot Study

In light of the associated risks, the question has been raised whether the decision to give a blood transfusion should solely be based on the hemoglobin level. As mitochondria are the final destination of oxygen transport, mitochondrial parameters are suggested to be of added value. The aims of this pilot study were to investigate the effect of a red blood cell transfusion on mitochondrial oxygenation as measured by the COMET device in chronic anemia patients and to explore the clinical usability of the COMET monitor in blood transfusion treatments, especially the feasibility of performing measurements in an outpatient setting. To correct the effect of volume load on mitochondrial oxygenation, a red blood cell transfusion and a saline infusion were given in random order. In total, 21 patients were included, and this resulted in 31 observations. If patients participated twice, the order of infusion was reversed. In both the measurements wherein a blood transfusion was given first and wherein 500 mL of 0.9% saline was given first, the median mitochondrial oxygen tension decreased after red blood cell transfusion. The results of this study have strengthened the need for further research into the effect of blood transfusion tissue oxygenation and the potential role of mitochondrial parameters herein.

Label-free testing strategy to evaluate packed red blood cell quality before transfusion to leukemia patients

Patients worldwide require therapeutic transfusions of packed red blood cells (pRBCs), which is applied to the high-risk patients who need periodic transfusions due to leukemia, lymphoma, myeloma and other blood diseases or disorders. Contrary to the general hospital population where the transfusions are carried out mainly for healthy trauma patients, in case of high-risk patients the proper quality of pRBCs is crucial. This leads to an increased demand for efficient technology providing information on the pRBCs alterations deteriorating their quality. Here we present the design of an innovative, label-free, noninvasive, rapid Raman spectroscopy-based method for pRBCs quality evaluation, starting with the description of sample measurement and data analysis, through correlation of spectroscopic results with reference techniques' outcomes, and finishing with methodology verification and its application in clinical conditions. We have shown that Raman spectra collected from the pRBCs supernatant mixture with a proper chemometric analysis conducted for a minimum one ratio of integral intensities of the chosen Raman marker bands within the spectrum allow evaluation of the pRBC quality in a rapid, noninvasive, and free-label manner, without unsealing the pRBCs bag. Subsequently, spectroscopic data were compared with predefined reference values, either from pRBCs expiration or those defining the pRBCs quality, allowing to assess their utility for transfusion to patients with acute myeloid leukemia (AML) and lymphoblastic leukemia (ALL).

Hemoglobin Oxidation in Stored Blood Accelerates Hemolysis and Oxidative Injury to Red Blood Cells

Introduction  Maintaining blood supply is a challenge in blood banks. Red blood cells (RBCs) stored at 4°C experience issues of biochemical changes due to metabolism of cells, leading to changes collectively referred to as “storage lesions.” Oxidation of the red cell membrane, leading to lysis, contributes to these storage lesions.

Methods  Blood bags with CPD-SAGM stored at 4°C for 28 days were withdrawn aseptically on days 1, 14, and 28. Hematology analyzer was used to investigate RBC indices. Hemoglobin oxidation was studied through spectrophotometric scan of spectral change. RBC lysis was studied with the help of Drabkin's assay, and morphological changes were observed by light and scan electron microscopy.

Results  RBCs show progressive changes in morphology echinocytes and spherocytes on day 28. There was 0.85% RBC lysis, an approximately 20% decrease in percentage oxyhemoglobin, and a 14% increase in methemoglobin formation, which shows hemoglobin oxidation on day 28.

Conclusions  Oxidative damage to RBC, with an increase in storage time was observed in the present study. The observed morphological changes to RBC during the course of increased time shows that there is progressive damage to RBC membrane and a decrease in hemoglobin concentration; percentage RBC lysis is probably due to free hemoglobin and iron.

Effectiveness of administering tranexamic acid to high-risk hip and knee arthroplasty patients: a systematic review protocol

OBJECTIVE

The objective of this review is to assess the safety and effectiveness in administering tranexamic acid in high-risk hip and knee arthroplasty patients.

INTRODUCTION

Arthroplasty surgery is associated with a significant amount of perioperative blood loss. Tranexamic acid is an antifibrinolytic used to counteract blood loss. Although various studies have demonstrated the effectiveness of tranexamic acid without significant adverse effects, a majority of these studies have excluded high-risk patients. Due to this selection bias there is a lack of clear evidence of the safety of administering tranexamic acid in high-risk patients.

INCLUSION CRITERIA

This review will consider studies that included high-risk patients aged >18 years who had previous myocardial infarction including cardiac stents, deep vein thrombosis and/or pulmonary embolism, transient ischemic attacks and/or stroke and clotting disorders. No exclusions will be made for the dosing route of tranexamic acid. The outcomes measured will be 1) thromboembolic complications of deep vein thrombosis, pulmonary embolism, transient ischemic attacks, stroke, myocardial infarction and death; 2) requirements of blood transfusion and 3) the amount of blood loss.

METHODS

A search will be conducted in PubMed, Embase, Scopus and Web of Science databases with the results being reported in a PRISMA flow diagram. Selected studies will be critically appraised by two independent reviewers for methodological quality. Study and outcome quality will be reported using the GRADE approach. Data will be extracted using a standardized data extraction tool. Studies will, where possible, be pooled in statistical meta-analysis. Effect sizes will be expressed as either odds ratios (for dichotomous data) or standardized mean differences (for continuous data) and their 95% confidence intervals will be calculated for analysis.

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.

Intra-operative blood transfusion significantly increases the risk of post-operative pulmonary embolism

Background

Pulmonary embolism (PE) is a serious and preventable complication after surgery. Blood transfusion is a common event during surgery. The aim of the present study was to identify whether intra-operative blood product transfusions increase the risk of symptomatic post-operative PE.

Methods

A retrospective, single-center case-control study at Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University between 1 January 2013 and 31 December 2016 was performed. Adult hospitalized patients with confirmed symptomatic PE after surgery were defined as case group. Each patient was matched with two adult patients without symptomatic PE who underwent the same procedure on the same day or within one week. Perioperative data especially detailed blood transfusion was collected. Forward stepwise logistic regression analysis was performed.

Results

During the study period, altogether 188,512 procedures were included, and postoperative PE were confirmed in 40 (0.02%) patients. Twelve (30.0%) case patients and 16 (20.0%) control patients received intra-operative blood transfusion. Intra-operative blood transfusion was revealed as a significant predictor for symptomatic post-operative PE (OR 80.669, 95% CI: 3.312-1,964.641, P=0.007), along with female sex (OR 86.921, 95% CI: 4.242-1,781.124, P=0.004), older age (OR 1.078, 95% CI: 1.005-1.156, P=0.035), longer length of stay before surgery (OR 1.124, 95% CI: 1.040-1.214, P=0.003) and longer operation time (OR 1.013, 95% CI: 1.002-1.025, P=0.024).

Conclusions

Intra-operative blood transfusion was associated with an increased risk of symptomatic post-operative PE. PE prophylaxis and selective screening should be considered in patients who had received intra-operative blood transfusion, especially in female patients.

Perioperative allogenic blood transfusion increases the incidence of postoperative deep vein thrombosis in total knee and hip arthroplasty

Background

Excessive blood loss caused by total joint arthroplasty (TJA) often increases the requirement for blood transfusion, which is associated with adverse outcomes. The purpose of this study was to determine the relationship between perioperative transfusion and postoperative DVT in TJA.

Methods

This retrospective study reviewed medical records of 715 patients, who consecutively underwent primary unilateral total knee arthroplasty (TKA) or total hip arthroplasty (THA) at our institution between September 2015 and March 2017. Demographic, clinical and surgical parameters were introduced into the univariate analysis to find risk factors for DVT within postoperative 30 days. In order to identify if allogenic blood transfusion was independently associated with DVT, a multivariate logistic regression analysis was conducted to adjust for gender, age, body mass index (BMI), diagnosis, and type of surgery.

Results

The incidence of perioperative allogenic blood transfusion was 12.4% (n = 89). Fifty-seven patients (8.0%) developed DVT after surgery. Univariate analysis demonstrated that there were differences between DVT group and non-DVT group in gender (P = 0.045), age (P < 0.001), BMI (P = 0.026), primary diagnosis (P = 0.001), type of surgery (P < 0.001), and transfusion rates (P = 0.040). After adjustment by using multivariate logistic regression analysis, transfusion appeared to be the independent risk factor for DVT in TJA (P = 0.001; OR = 3.9, 95%CI 1.8–8.4).

Conclusion

We found that perioperative allogenic blood transfusion was significantly associated with DVT following TJA. In order to reduce the risk of DVT and other adverse outcomes, methods to decrease transfusion rates should be used in clinical practice.

Transfusion practice in anemic, non-bleeding patients: Cross-sectional survey of physicians working in general internal medicine teaching hospitals in Switzerland

Background

Transfusion practice might significantly influence patient morbidity and mortality. Between European countries, transfusion practice of red blood cells (RBC) greatly differs. Only sparse data are available on transfusion practice of general internal medicine physicians in Switzerland.

Methods

In this cross-sectional survey, physicians working in general medicine teaching hospitals in Switzerland were investigated regarding their self-reported transfusion practice in anemic patients without acute bleeding. The definition of anemia, transfusion triggers, knowledge on RBC transfusion, and implementation of guidelines were assessed.

Results

560 physicians of 71 hospitals (64%) responded to the survey. Anemia was defined at very diverging hemoglobin values (by 38% at a hemoglobin <130 g/L for men and by 57% at <120 g/L in non-pregnant women). 62% and 43% respectively, did not define anemia in men and in women according to the World Health Organization. Fifty percent reported not to transfuse RBC according to international guidelines. Following factors were indicated to influence the decision to transfuse: educational background of the physicians, geographical region of employment, severity of anemia, and presence of known coronary artery disease. 60% indicated that their knowledge on Transfusion-related Acute Lung Injury (TRALI) did not influence transfusion practice. 50% of physicians stated that no local transfusion guidelines exist and 84% supported the development of national recommendations on transfusion in non-acutely bleeding, anemic patients.

Conclusion

This study highlights the lack of adherence to current transfusion guidelines in Switzerland. Identifying and subsequently correcting this deficit in knowledge translation may have a significant impact on patient care.

Previous Cryopreservation Alters the Natural History of the Red Blood Cell Storage Lesion

BACKGROUND

During storage, packed red blood cells (pRBCs) undergo a number of biochemical, metabolic, and morphologic changes, collectively known as the "storage lesion." We aimed to determine the effect of cryopreservation on the red blood cell storage lesion compared with traditional 4°C storage.

METHODS

Previously cryopreserved human pRBCs were compared with age-matched never-frozen pRBCs obtained from the local blood bank. The development of the red cell storage lesion was evaluated after 7, 14, 21, 28, and 42 days of storage at 4°C in AS-3 storage medium. We measured physiological parameters including cell counts, lactic acid, and potassium concentrations as well as signs of eryptosis including loss of phosphatidylserine (PS) asymmetry, microparticle production, and osmotic fragility in hypotonic saline.

RESULTS

Compared with controls, previously cryopreserved pRBC at 7 days of storage in AS-3 showed lower red cell counts (3.7 vs. 5.3 × 10 cells/μL, P < 0.01), hemoglobin (Hgb) (12.0 vs. 16.5 g/dL, P < 0.01), hematocrit (33.0% vs. 46.5%, P < 0.01), and pH (6.27 vs. 6.72, P < 0.01). Over 28 days of storage, storage cryopreserved pRBC developed increased cell-free Hgb (0.7 vs. 0.3 g/dL, P < 0.01), greater PS exposure (10.1% vs. 3.3%, P < 0.01), and microparticle production (30,836 vs. 1,802 MP/μL, P < 0.01). Previously cryopreserved cells were also less resistant to osmotic stress.

CONCLUSION

The red blood cell storage lesion is accelerated in previously cryopreserved pRBC after thawing. Biochemical deterioration of thawed and deglycerolized red cells suggests that storage time before transfusion should be limited to achieve similar risk profiles as never-frozen standard liquid storage pRBC units.

Preischemic transfusion of old packed RBCs exacerbates early-phase warm hepatic ischemia reperfusion injury in rats

BACKGROUND

Hepatic innate immune cells are considered to play a central role in the early phase of hepatic ischemia reperfusion (IR) injury. Transfusion of old red blood cells (RBCs) is known to prime immune cells, and transfusion before IR may exacerbate liver injury because of the expected hyperresponsiveness of immune cells.

MATERIALS AND METHODS

Twenty-four Sprague-Dawley rats were divided into four groups: sham operation (Sham); hepatic IR only (IR Control); and two transfusion groups, preischemic (Pre-T) and postischemic (Post-T), in which allogeneic RBCs stored for 2 weeks were transfused before hepatic IR or after reperfusion, respectively. Partial hepatic ischemia was induced for 90 min, and reperfusion was allowed for 120 min. Serum alanine transaminase levels, area of necrosis, and apoptotic cells were then assessed. Inflammatory (tumor necrosis factor alpha, interleukin 1 beta [IL-1β], IL-6, IL-10, and cyclooxygenase 2) and oxidative mediators (heme oxygenase 1, superoxide dismutase, and glutathione peroxidase 1) were assessed for elucidating the relevant mechanisms underlying the hepatic injury.

RESULTS

Pre-T, but not Post-T, showed increased serum alanine transaminase levels than IR Control (P < 0.05). Area of necrosis was more severe in Pre-T than in IR Control or Post-T (P < 0.01), and apoptotic cells were also more abundant in Pre-T than in IR Control (P < 0.01). tumor necrosis factor alpha and IL-6 levels were higher in Pre-T than in IR Control or Post-T (P < 0.05), with no significant difference in cytoprotective protein levels.

CONCLUSIONS

Preischemic transfusion of old RBCs aggravated hepatic injury. Inflammatory cytokines seemed to play a crucial role in liver injury exacerbation. Our results indicate that transfusion before hepatic ischemia may be detrimental.

Acquired Amino Acid Deficiencies: A Focus on Arginine and Glutamine

Nonessential amino acids are synthesized de novo and therefore not diet dependent. In contrast, essential amino acids must be obtained through nutrition since they cannot be synthesized internally. Several nonessential amino acids may become essential under conditions of stress and catabolic states when the capacity of endogenous amino acid synthesis is exceeded. Arginine and glutamine are 2 such conditionally essential amino acids and are the focus of this review. Low arginine bioavailability plays a pivotal role in the pathogenesis of a growing number of varied diseases, including sickle cell disease, thalassemia, malaria, acute asthma, cystic fibrosis, pulmonary hypertension, cardiovascular disease, certain cancers, and trauma, among others. Catabolism of arginine by arginase enzymes is the most common cause of an acquired arginine deficiency syndrome, frequently contributing to endothelial dysfunction and/or T-cell dysfunction, depending on the clinical scenario and disease state. Glutamine, an arginine precursor, is one of the most abundant amino acids in the body and, like arginine, becomes deficient in several conditions of stress, including critical illness, trauma, infection, cancer, and gastrointestinal disorders. At-risk populations are discussed together with therapeutic options that target these specific acquired amino acid deficiencies.

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.

Cryopreserved packed red blood cells in surgical patients: past, present, and future

Since the advent of anticoagulation and component storage of human blood products, allogeneic red blood cell transfusion has been one of the most common practices in modern medicine. Efforts to reduce the biochemical effects of storage, collectively known as the red blood cell storage lesion, and prolong the storage duration have led to numerous advancements in erythrocyte storage solutions. Cryopreservation and frozen storage of red blood cells in glycerol have been successfully utilised by many civilian and military institutions worldwide. Through progressive improvements in liquid storage of erythrocytes in novel storage solutions, the logistical need for cryopreserved red blood cells in the civilian setting has diminished. A growing body of current literature is focused on the clinical consequences of packed red blood cell age. Modern cryopreservation techniques show promise as a cost-effective method to ameliorate the negative effect of the red blood cell storage lesion, while meeting the technical and logistical needs of both civilian and military medicine. This review outlines the history of red blood cell cryopreservation, the clinical impact of red cell storage, and highlights the current literature on frozen blood and its impact on modern transfusion.

Red Blood Cells Store and Release Interleukin-33

Interleukin-33 (IL-33) is a member of the IL-1 cytokine superfamily that potently drives production of a variety of cytokines and contributes to the pathogenesis of inflammatory diseases. The IL-33 is a nuclear protein and is released from apoptotic or necrotic cells. Serum IL-33 levels are increased in various diseases, such as atopic dermatitis, chronic hepatitis C infection, and asthma. Here, we show that red blood cells (RBCs) are one of the major sources of plasma IL-33. The IL-33 levels are significantly increased in supernatants from lysed RBCs. Plasma IL-33 levels are increased in patients during hemolysis, and plasma IL-33 levels show a positive correlation with degree of hemolysis. The IL-33 protein and messenger RNA levels were detected in the late stages of differentiation in ex vivo primary human erythroid progenitor cell cultures, suggesting that IL-33 is expressed during maturation of RBCs. Furthermore, hemoglobin depleted red cell lysates induced IL-8 expression in human epithelial cells. This effect was attenuated in IL-33 decoy receptor expressing cells and was enhanced in IL-33 receptor expressing cells. These results suggest that erythroid progenitor cells produce IL-33 and circulating RBCs represent a major source of IL-33 that is released upon hemolysis.

Identified metabolic signature for assessing red blood cell unit quality is associated with endothelial damage markers and clinical outcomes

BACKGROUND

There has been interest in determining whether older red blood cell (RBC) units have negative clinical effects. Numerous observational studies have shown that older RBC units are an independent factor for patient mortality. However, recently published randomized clinical trials have shown no difference of clinical outcome for patients receiving old or fresh RBCs. An overlooked but essential issue in assessing RBC unit quality and ultimately designing the necessary clinical trials is a metric for what constitutes an old or fresh RBC unit.

STUDY DESIGN AND METHODS

Twenty RBC units were profiled using quantitative metabolomics over 42 days of storage in SAGM with 3- to 4-day time intervals. Metabolic pathway usage during storage was assessed using systems biology methods. The detected time intervals of the metabolic states were compared to clinical outcomes.

RESULTS

Using multivariate statistics, we identified a nonlinear decay process exhibiting three distinct metabolic states (Days 0-10, 10-17, and 17-42). Hematologic variables traditionally measured in the transfusion setting (e.g., pH, hemolysis, RBC indices) did not distinguish these three states. Systemic changes in pathway usage occurred between the three states, with key pathways changing in both magnitude and direction. Finally, an association was found between the time periods of the metabolic states with the clinical outcomes of more than 280,000 patients in the country of Denmark transfused over the past 15 years and endothelial damage markers in healthy volunteers undergoing autologous transfusions.

CONCLUSION

The state of RBC metabolism may be a better indicator of cellular quality than traditional hematologic variables.

Topical versus intravenous tranexamic acid in total knee arthroplasty

The objective of this study is to compare the effectiveness of intravenous versus topical application of tranexamic acid in patients undergoing knee arthroplasty. All patients who underwent primary knee arthroplasty at our total joint center over a 12-month period were included in the study. One surgeon utilized 1 g of IV TXA at time of incision in all patients (n=373) except those with a documented history of venous thromboembolism (VTE). Two surgeons utilized a topical application of TXA for all patients without exception (n=198) in which the joint was injected after capsular closure with 3 g TXA/100 mL saline. The transfusion rate was 0% in the topical group vs. 2.4% in the IV group and this was statistically significant (P<0.05).

Detection of microparticles from human red blood cells by multiparametric flow cytometry

BACKGROUND

During storage, red blood cells (RBC) undergo chemical and biochemical changes referred to as "storage lesions". These events determine the loss of RBC integrity, resulting in lysis and release of microparticles. There is growing evidence of the clinical importance of microparticles and their role in blood transfusion-related side effects and pathogen transmission. Flow cytometry is currently one of the most common techniques used to quantify and characterise microparticles. Here we propose multiparametric staining to monitor and quantify the dynamic release of microparticles by stored human RBC.

MATERIAL AND METHODS

RBC units (n=10) were stored under blood bank conditions for up to 42 days. Samples were tested at different time points to detect microparticles and determine the haemolysis rate (HR%). Microparticles were identified by flow cytometry combining carboxyfluorescein diacetate succinimidyl ester (CFSE) dye, annexin V and anti-glycophorin A antibody.

RESULTS

We demonstrated that CFSE can be successfully used to label closed vesicles with an intact membrane. The combination of CFSE and glycophorin A antibody was effective for monitoring and quantifying the dynamic release of microparticles from RBC during storage. Double staining with CFSE/glycophorin A was a more precise approach, increasing vesicle detection up to 4.7-fold vs the use of glycophorin A/annexin V alone. Moreover, at all the time points tested, we found a robust correlation (R=0.625; p=0.0001) between HR% and number of microparticles detected.

DISCUSSION

Multiparametric staining, based on a combination of CFSE, glycophorin A antibody and annexin V, was able to detect, characterise and monitor the release of microparticles from RBC units during storage, providing a sensitive approach to labelling and identifying microparticles for transfusion medicine and, more broadly, for cell-based therapies.

Metabolomics profile comparisons of irradiated and nonirradiated stored donor red blood cells

BACKGROUND

Understanding the metabolites that are altered by donor red blood cell (RBC) storage and irradiation may provide insight into the metabolic pathways disrupted by the RBC storage lesion.

STUDY DESIGN AND METHODS

Patterns of metabolites, representing more than 11,000 distinct mass-to-charge ratio (m/z) features, were compared between gamma-irradiated and nonirradiated CPDA-1-split RBCs from six human donors over 35 days of storage using multilevel sparse partial least squares discriminant analysis (msPLSDA), hierarchical clustering, pathway enrichment analysis, and network analysis.

RESULTS

In msPLSDA analysis, RBC units stored 7 days or fewer (irradiated or nonirradiated) showed similar metabolomic profiles. By contrast, donor RBCs stored 10 days or more demonstrated distinct clustering as a function of storage time and irradiation. Irradiation shifted metabolic features to those seen in older units. Hierarchical clustering analysis identified at least two clusters of metabolites that differentiated between RBC units based on storage time and irradiation exposure, confirming results of the msPLSDA analysis. Pathway enrichment analysis, used to map the discriminatory biochemical features to specific metabolic pathways, identified four pathways significantly affected by irradiation and/or storage including arachidonic acid (p = 3.3 × 10(-33)) and linoleic acid (p = 1.61 × 10(-11)) metabolism.

CONCLUSION

RBC storage under blood bank conditions produces numerous metabolic alterations. Gamma irradiation accentuates these differences as the age of blood increases, indicating that at the biochemical level irradiation accelerates metabolic aging of stored RBCs. Metabolites involved in the cellular membrane are prominently affected and may be useful biomarkers of the RBC storage lesion.

Optical assay of erythrocyte function in banked blood

Stored red blood cells undergo numerous biochemical, structural, and functional changes, commonly referred to as storage lesion. How much these changes impede the ability of erythrocytes to perform their function and, as result, impact clinical outcomes in transfusion patients is unknown. In this study we investigate the effect of the storage on the erythrocyte membrane deformability and morphology. Using optical interferometry we imaged red blood cell (RBC) topography with nanometer sensitivity. Our time-lapse imaging quantifies membrane fluctuations at the nanometer scale, which in turn report on cell stiffness. This property directly impacts the cell's ability to transport oxygen in microvasculature. Interestingly, we found that cells which apparently maintain their normal shape (discocyte) throughout the storage period, stiffen progressively with storage time. By contrast, static parameters, such as mean cell hemoglobin content and morphology do not change during the same period. We propose that our method can be used as an effective assay for monitoring erythrocyte functionality during storage time.

Artificial oxygen carrier with pharmacologic actions of adenosine-5'-triphosphate, adenosine, and reduced glutathione formulated to treat an array of medical conditions

Effective artificial oxygen carriers may offer a solution to tackling current transfusion medicine challenges such as blood shortages, red blood cell storage lesions, and transmission of emerging pathogens. These products, could provide additional therapeutic benefits besides oxygen delivery for an array of medical conditions. To meet these needs, we developed a hemoglobin (Hb)-based oxygen carrier, HemoTech, which utilizes the concept of pharmacologic cross-linking. It consists of purified bovine Hb cross-linked intramolecularly with open ring adenosine-5'-triphosphate (ATP) and intermolecularly with open ring adenosine, and conjugated with reduced glutathione (GSH). In this composition, ATP prevents Hb dimerization, and adenosine promotes formation of Hb polymers as well as counteracts the vasoconstrictive and pro-inflammatory properties of Hb via stimulation of adenosine receptors. ATP also serves as a regulator of vascular tone through activation of purinergic receptors. GSH blocks Hb's extravasation and glomerular filtration by lowering the isoelectric point, as well as shields heme from nitric oxide and reactive oxygen species. HemoTech and its manufacturing technology have been broadly tested, including viral and prion clearance validation studies and various nonclinical pharmacology, toxicology, genotoxicity, and efficacy tests. The clinical proof-of-concept was carried out in sickle cell anemia subjects. The preclinical and clinical studies indicate that HemoTech works as a physiologic oxygen carrier and has efficacy in treating: (i) acute blood loss anemia by providing a temporary oxygen bridge while stimulating an endogenous erythropoietic response; (ii) sickle cell disease by counteracting vaso-occlusive/inflammatory episodes and anemia; and (iii) ischemic vascular diseases particularly thrombotic and restenotic events. The pharmacologic cross-linking of Hb with ATP, adenosine, and GSH showed usefulness in designing an artificial oxygen carrier for multiple therapeutic indications.

Characterization of red blood cell deformability change during blood storage

Stored red blood cells (RBCs) show progressive deformability changes during blood banking/storage. Their deformability changes over an 8 weeks' storage period were measured using a microfluidic device. Hydrodynamic focusing controls the orientation and position of individual RBCs within the microchannel. High-speed imaging (5000 frames s(-1)) captures the dynamic deformation behavior of the cells, and together with automated image analysis, enables the characterization of over 1000 RBCs within 3 minutes. Multiple parameters including deformation index (DI), time constant (shape recovery rate), and RBC circularity were quantified. Compared to previous studies on stored RBC deformability, our results include a significantly higher number of cells (>1000 cells per sample vs. a few to tens of cells per sample) and, for the first time, reveal deformation changes of stored RBCs when traveling through human-capillary-like microchannels. Contrary to existing knowledge, our results demonstrate that the deformation index of RBCs under folding does not change significantly over blood storage. However, significant differences exist in time constants and circularity distribution widths, which can be used to quantify stored RBC quality or age.

Endothelial nitric oxide synthase in red blood cells: key to a new erythrocrine function?

Red blood cells (RBC) have been considered almost exclusively as a transporter of metabolic gases and nutrients for the tissues. It is an accepted dogma that RBCs take up and inactivate endothelium-derived NO via rapid reaction with oxyhemoglobin to form methemoglobin and nitrate, thereby limiting NO available for vasodilatation. Yet it has also been shown that RBCs not only act as "NO sinks", but exert an erythrocrine function - i.e an endocrine function of RBC - by synthesizing, transporting and releasing NO metabolic products and ATP, thereby potentially controlling systemic NO bioavailability and vascular tone. Recent work from our and others laboratory demonstrated that human RBCs carry an active type 3, endothelial NO synthase (eNOS), constitutively producing NO under normoxic conditions, the activity of which is compromised in patients with coronary artery disease. In this review we aim to discuss the potential role of red cell eNOS in RBC signaling and function, and to critically revise evidence to this date showing a role of non-endothelial circulating eNOS in cardiovascular pathophysiology.

The effects of rejuvenation during hypothermic storage on red blood cell membrane remodeling

BACKGROUND

Our previous studies showed that hypothermic storage (HS) induces red blood cell (RBC) microparticle (RMP) generation and changes in phosphatidylserine (PS) and CD47 expression on RBCs and RMPs. The aim of this study was to evaluate the effect of cold rejuvenation treatment at multiple time points during storage on these prehemolytic indicators of RBC membrane storage lesion.

STUDY DESIGN AND METHODS

Leukoreduced RBC units in saline-adenine-glucose-mannitol were used to generate three groups: untreated controls, sham-treated units, and units treated with a cold (1-6°C) rejuvenation solution on Day 28, 35, or 42 of HS. Units were assessed for hemolysis, adenosine triphosphate (ATP) concentration, lipid composition, and RMP generation, as well as PS and CD47 expression throughout 49 days of HS.

RESULTS

Rejuvenation treatment led to a significant increase in ATP concentration in all units, irrespective of treatment day. There were no significant differences between sham- and rejuvenation-treated RBC samples in the levels of PS externalization, CD47 expression, or the rate of RMP formation. RBCs rejuvenated on Day 28 were enriched in glycerophosphocholine (+23.5%), depleted in sphingomyelin (-14%), and slightly depleted in cholesterol (-3.5%).

CONCLUSION

Cold rejuvenation in hypothermically stored RBCs affects the lipid composition of RBCs and respective RMPs in a time-dependent fashion.

Circulating blood endothelial nitric oxide synthase contributes to the regulation of systemic blood pressure and nitrite homeostasis

OBJECTIVE

Mice genetically deficient in endothelial nitric oxide synthase (eNOS(-/-)) are hypertensive with lower circulating nitrite levels, indicating the importance of constitutively produced nitric oxide (NO•) to blood pressure regulation and vascular homeostasis. Although the current paradigm holds that this bioactivity derives specifically from the expression of eNOS in endothelium, circulating blood cells also express eNOS protein. A functional red cell eNOS that modulates vascular NO• signaling has been proposed.

APPROACH AND RESULTS

To test the hypothesis that blood cells contribute to mammalian blood pressure regulation via eNOS-dependent NO• generation, we cross-transplanted wild-type and eNOS(-/-) mice, producing chimeras competent or deficient for eNOS expression in circulating blood cells. Surprisingly, we observed a significant contribution of both endothelial and circulating blood cell eNOS to blood pressure and systemic nitrite levels, the latter being a major component of the circulating NO• reservoir. These effects were abolished by the NOS inhibitor L-NG-nitroarginine methyl ester and repristinated by the NOS substrate L-arginine and were independent of platelet or leukocyte depletion. Mouse erythrocytes were also found to carry an eNOS protein and convert (14)C-arginine into (14)C-citrulline in NOS-dependent fashion.

CONCLUSIONS

These are the first studies to definitively establish a role for a blood-borne eNOS, using cross-transplant chimera models, that contributes to the regulation of blood pressure and nitrite homeostasis. This work provides evidence suggesting that erythrocyte eNOS may mediate this effect.

Storage of red blood cells affects membrane composition, microvesiculation, and in vitro quality

BACKGROUND

During storage detrimental biochemical and biomechanical changes occur within a red blood cell (RBC). RBC microparticles (RMPs) produced during storage have been identified as biomarkers of RBC quality, being potentially immunogenic and inhibitory to nitric oxide regulation.

STUDY DESIGN AND METHODS

In this study, microvesiculation and changes in the composition of the RBC membrane were investigated throughout 49 days of storage and were correlated with in vitro assays examining membrane quality. Leukoreduced RBC units produced using the buffy coat method were collected and stored at 1 to 6°C and were tested weekly for hemolysis, osmotic fragility, deformability, ATP, hematologic indices, and morphology. Microvesiculation was assessed using multicolor flow cytometry. High-performance liquid chromatography and mass spectrometry were used to determine the composition and quantity of phospholipids (PLs) and cholesterol (C) on Days 2 and 43.

RESULTS

The assessment of RBCs throughout storage revealed significant increases in percent hemolysis, while significant decreases in ATP concentrations, and the mean corpuscular hemoglobin concentration were observed. Flow cytometry analysis revealed a significant increase in the mean number of microparticles per microliter during storage. Throughout storage, significant decreases were identified in the amount of PLs and total lipids within the RBC membrane. No significant change in the amount of C in the RBC membrane was identified.

CONCLUSION

Significant changes to the RBC membrane occur during storage. The length of storage will influence RMP generation, osmotic fragility, hemolysis, and changes in deformability. These changes in RBC in vitro quality may contribute to transfusion reactions and negative posttransfusion outcomes.

Age of red blood cells and transfusion in critically ill patients

Red blood cells (RBC) storage facilitates the supply of RBC to meet the clinical demand for transfusion and to avoid wastage. However, RBC storage is associated with adverse changes in erythrocytes and their preservation medium. These changes are responsible for functional alterations and for the accumulation of potentially injurious bioreactive substances. They also may have clinically harmful effects especially in critically ill patients. The clinical consequences of storage lesions, however, remain a matter of persistent controversy. Multiple retrospective, observational, and single-center studies have reported heterogeneous and conflicting findings about the effect of blood storage duration on morbidity and/or mortality in trauma, cardiac surgery, and intensive care unit patients. Describing the details of this controversy, this review not only summarizes the current literature but also highlights the equipoise that currently exists with regard to the use of short versus current standard (extended) storage duration red cells in critically ill patients and supports the need for large, randomized, controlled trials evaluating the clinical impact of transfusing fresh (short duration of storage) versus older (extended duration of storage) red cells in critically ill patients.

Hemoglobin infusion does not alter murine pulmonary vascular tone

Plasma hemoglobin (Hb) scavenges endothelium-derived nitric oxide (NO), producing systemic and pulmonary vasoconstriction in many species. We hypothesized that i.v. administration of murine cell-free Hb would produce pulmonary vasoconstriction and enhance hypoxic pulmonary vasoconstriction (HPV) in mice. To assess the impact of plasma Hb on basal pulmonary vascular tone in anesthetized mice we measured left lung pulmonary vascular resistance (LPVRI) before and after infusion of Hb at thoracotomy. To confirm the findings obtained at thoracotomy, measurements of right ventricular systolic pressure (RVSP) and systemic arterial pressure (SAP) were obtained in closed-chest wild-type mice. To elucidate whether pretreatment with Hb augments HPV we assessed the increase in LPVRI before and during regional lung hypoxia produced by left mainstem bronchial occlusion (LMBO) in wild-type mice pretreated with Hb. Infusion of Hb increased SAP but did not change pulmonary arterial pressure (PAP), left lung pulmonary arterial flow (QLPA) or LPVRI in either wild-type or diabetic mice with endothelial dysfunction. Scavenging of NO by plasma Hb did not alter HPV in wild-type mice. Inhibition of NO synthase with l-NAME did not change the basal LPVRI, but augmented HPV during LMBO. Our data suggest that scavenging of NO by plasma Hb does not alter pulmonary vascular tone in mice. Therefore, generation of NO in the pulmonary circulation is unlikely to be responsible for the low basal pulmonary vascular tone of mice.

Red blood cell microparticles and blood group antigens: an analysis by flow cytometry

BACKGROUND

The storage of blood induces the formation of erythrocytes-derived microparticles. Their pathogenic role in blood transfusion is not known so far, especially the risk to trigger alloantibody production in the recipient. This work aims to study the expression of clinically significant blood group antigens on the surface of red blood cells microparticles.

MATERIAL AND METHODS

Red blood cells contained in erythrocyte concentrates were stained with specific antibodies directed against blood group antigens and routinely used in immunohematology practice. After inducing erythrocytes vesiculation with calcium ionophore, the presence of blood group antigens was analysed by flow cytometry.

RESULTS

The expression of several blood group antigens from the RH, KEL, JK, FY, MNS, LE and LU systems was detected on erythrocyte microparticles. The presence of M (MNS1), N (MNS2) and s (MNS4) antigens could not be demonstrated by flow cytometry, despite that glycophorin A and B were identified on microparticles using anti-CD235a and anti-MNS3.

DISCUSSION

We conclude that blood group antigens are localized on erythrocytes-derived microparticles and probably keep their immunogenicity because of their capacity to bind specific antibody. Selective segregation process during vesiculation or their ability to elicit an immune response in vivo has to be tested by further studies.

Low levels of tissue factor lead to alveolar haemorrhage, potentiating murine acute lung injury and oxidative stress

BACKGROUND

Systemic blockade of tissue factor (TF) attenuates acute lung injury (ALI) in animal models of sepsis but the effects of global TF deficiency are unknown. We used mice with complete knockout of mouse TF and low levels (∼1%) of human TF (LTF mice) to test the hypothesis that global TF deficiency attenuates lung inflammation in direct lung injury.

METHODS

LTF mice were treated with 10 μg of lipopolysaccharide (LPS) or vehicle administered by direct intratracheal injection and studied at 24 h.

RESULTS

Contrary to our hypothesis, LTF mice had increased lung inflammation and injury as measured by bronchoalveolar lavage cell count (3.4×10(5) wild-type (WT) LPS vs 3.3×10(5) LTF LPS, p=0.947) and protein (493 μg/ml WT LPS vs 1014 μg/ml LTF LPS, p=0.006), proinflammatory cytokines (TNF-α, IL-10, IL-12, p<0.035 WT LPS vs LTF LPS) and histology compared with WT mice. LTF mice also had increased haemorrhage and free haemoglobin in the airspace accompanied by increased oxidant stress as measured by lipid peroxidation products (F(2) isoprostanes and isofurans).

CONCLUSIONS

These findings indicate that global TF deficiency does not confer protection in a direct lung injury model. Rather, TF deficiency causes increased intra-alveolar haemorrhage following LPS leading to increased lipid peroxidation. Strategies to globally inhibit TF may be deleterious in patients with ALI.

Temporal dynamics of microparticle elevation following subarachnoid hemorrhage

Object

Microparticles (MPs), small membrane fragments shed from various cell types, have been implicated in thrombosis, inflammation, and endothelial dysfunction. Their involvement in subarachnoid hemorrhage (SAH) and the development of cerebral infarction and clinical deterioration caused by delayed cerebral ischemia (DCI) remain ill defined. The authors sought to quantify the magnitude of elevations in MPs, delineate the temporal dynamics of elevation, and analyze the correlation between MPs and DCI in patients with SAH.

Methods

On the day of hemorrhage and on Days 1, 3, 5, 7, and 10 after hemorrhage, peripheral blood samples were drawn from 22 patients with SAH. Plasma samples were labeled with Annexin V and CD142, CD41a, CD235a, CD146, CD66b, or von Willebrand factor (vWF) and were quantified by flow cytometry. Clinical data, including the 3-month extended Glasgow Outcome Scale (GOS-E) scores, infarction as measured on MRI at 14 days after SAH, and vasospasm as measured by transcranial Doppler ultrasonography and angiography, were collected and compared with the MP burden.

Results

When averaged over time, all MP subtypes were elevated relative to controls. The CD235a+(erythrocyte)−, CD66b+(neutrophil)−, and vWF-associated MPs peaked on the day of hemorrhage and quickly declined. The CD142+(tissue factor [TF])–associated MPs and CD146+(endothelial cell)–associated MPs were significantly elevated throughout the study period. There was a strong negative correlation between TF-expressing and endothelial-derived MPs at Day 1 after SAH and the risk of infarction at Day 14 after SAH.

Conclusions

Microparticles of various subtypes are elevated following SAH; however, the temporal profile of this elevation varies by subtype. Those subtypes closely associated with thrombosis and endothelial dysfunction, for example, CD145+(TF)-associated MPs and CD146+(endothelial cell)–associated MPs, had the most durable response and demonstrated a significant negative correlation with radiographic infarction at 14 days after SAH. Levels of these MPs predict infarction as early as Day 1 post-SAH.

Improving cardiac function with new-generation plasma volume expanders

BACKGROUND

Plasma expander (PE) based on polyethylene glycol (PEG) conjugated to albumin has shown positive results maintaining blood volume during hemodilution and restoring blood volume during resuscitation from hemorrhagic shock. Polyethylene glycol conjugation to human serum albumin (HSA), PEG-HSA, increases size, weight, and colloidal osmotic pressure, with minor effects on solution viscosity.

METHODS

This study was designed to test the hypothesis that PEG-HSA (2 g/dL) produced by direct PEGylation chemistry improves cardiac function during 2 experimental models, (i) moderate hemodilution and (ii) resuscitation from hemorrhagic shock, compared with a conventional colloidal PE (Dextran 70 kd [Dx70], 6 g/dL). Cardiac function was studied using a miniaturized pressure volume conductance catheter implanted in the left ventricle and evaluated in terms of cardiac indices derived from the pressure volume measurements.

RESULTS

Polyethylene glycol-HSA increased cardiac output, stroke volume, and stroke work and decreased systemic vascular resistance compared with Dx70 in both experimental models. The improvements induced by PEG-HSA in cardiac function were sustained over the observation time. Polyethylene glycol-HSA cardiac mechanoenergetics changes are the result of increased energy transferred per stroke and decreased resistance of the vasculature connecting the heart. In summary, PEG-HSA decreased left ventricle ejection impedance.

CONCLUSION

Ejection of blood diluted with PEG-HSA presented a reduced load to the heart, increased contractile function, and lowered the energy consumed per unit volume compared with Dx70. Our results emphasize the importance of heart function as a parameter to be included in the evaluation changes induced by new PEs.

Phosphatidylserine-expressing cell by-products in transfusion: A pro-inflammatory or an anti-inflammatory effect?

Labile blood products contain phosphatidylserine-expressing cell dusts, including apoptotic cells and microparticles. These cell by-products are produced during blood product process or storage and derived from the cells of interest that exert a therapeutic effect (red blood cells or platelets). Alternatively, phosphatidylserine-expressing cell dusts may also derived from contaminating cells, such as leukocytes, or may be already present in plasma, such as platelet-derived microparticles. These cell by-products present in labile blood products can be responsible for transfusion-induced immunomodulation leading to either transfusion-related acute lung injury (TRALI) or increased occurrence of post-transfusion infections or cancer relapse. In this review, we report data from the literature and our laboratory dealing with interactions between antigen-presenting cells and phosphatidylserine-expressing cell dusts, including apoptotic leukocytes and blood cell-derived microparticles. Then, we discuss how these phosphatidylserine-expressing cell by-products may influence transfusion.

Blood transfusions increase circulating plasma free hemoglobin levels and plasma nitric oxide consumption: a prospective observational pilot study

Introduction

The increasing number of reports on the relation between transfusion of stored red blood cells (RBCs) and adverse patient outcome has sparked an intense debate on the benefits and risks of blood transfusions. Meanwhile, the pathophysiological mechanisms underlying this postulated relation remain unclear. The development of hemolysis during storage might contribute to this mechanism by release of free hemoglobin (fHb), a potent nitric oxide (NO) scavenger, which may impair vasodilation and microcirculatory perfusion after transfusion. The objective of this prospective observational pilot study was to establish whether RBC transfusion results in increased circulating fHb levels and plasma NO consumption. In addition, the relation between increased fHb values and circulating haptoglobin, its natural scavenger, was studied.

Methods

Thirty patients electively received 1 stored packed RBC unit (n = 8) or 2 stored packed RBC units (n = 22). Blood samples were drawn to analyze plasma levels of fHb, haptoglobin, and NO consumption prior to transfusion, and 15, 30, 60 and 120 minutes and 24 hours after transfusion. Differences were compared using Pearson's chi-square test or Fisher's exact test for dichotomous variables, or an independent-sample t test or Mann-Whitney U test for continuous data. Continuous, multiple-timepoint data were analyzed using repeated one-way analysis of variance or the Kruskall-Wallis test. Correlations were analyzed using Spearman or Pearson correlation.

Results

Storage duration correlated significantly with fHb concentrations and NO consumption within the storage medium (r = 0.51, P < 0.001 and r = 0.62, P = 0.002). fHb also significantly correlated with NO consumption directly (r = 0.61, P = 0.002). Transfusion of 2 RBC units significantly increased circulating fHb and NO consumption in the recipient (P < 0.001 and P < 0.05, respectively), in contrast to transfusion of 1 stored RBC unit. Storage duration of the blood products did not correlate with changes in fHb and NO consumption in the recipient. In contrast, pre-transfusion recipient plasma haptoglobin levels inversely influenced post-transfusion fHb concentrations.

Conclusion

These data suggest that RBC transfusion can significantly increase post-transfusion plasma fHb levels and plasma NO consumption in the recipient. This finding may contribute to the potential pathophysiological mechanism underlying the much-discussed adverse relation between blood transfusions and patient outcome. This observation may be of particular importance for patients with substantial transfusion requirements.

Blood transfusions increase circulating plasma free hemoglobin levels and plasma nitric oxide consumption: a prospective observational pilot study

INTRODUCTION

The increasing number of reports on the relation between transfusion of stored red blood cells (RBCs) and adverse patient outcome has sparked an intense debate on the benefits and risks of blood transfusions. Meanwhile, the pathophysiological mechanisms underlying this postulated relation remain unclear. The development of hemolysis during storage might contribute to this mechanism by release of free hemoglobin (fHb), a potent nitric oxide (NO) scavenger, which may impair vasodilation and microcirculatory perfusion after transfusion. The objective of this prospective observational pilot study was to establish whether RBC transfusion results in increased circulating fHb levels and plasma NO consumption. In addition, the relation between increased fHb values and circulating haptoglobin, its natural scavenger, was studied.

METHODS

Thirty patients electively received 1 stored packed RBC unit (n = 8) or 2 stored packed RBC units (n = 22). Blood samples were drawn to analyze plasma levels of fHb, haptoglobin, and NO consumption prior to transfusion, and 15, 30, 60 and 120 minutes and 24 hours after transfusion. Differences were compared using Pearson's chi-square test or Fisher's exact test for dichotomous variables, or an independent-sample t test or Mann-Whitney U test for continuous data. Continuous, multiple-timepoint data were analyzed using repeated one-way analysis of variance or the Kruskall-Wallis test. Correlations were analyzed using Spearman or Pearson correlation.

RESULTS

Storage duration correlated significantly with fHb concentrations and NO consumption within the storage medium (r = 0.51, P < 0.001 and r = 0.62, P = 0.002). fHb also significantly correlated with NO consumption directly (r = 0.61, P = 0.002). Transfusion of 2 RBC units significantly increased circulating fHb and NO consumption in the recipient (P < 0.001 and P < 0.05, respectively), in contrast to transfusion of 1 stored RBC unit. Storage duration of the blood products did not correlate with changes in fHb and NO consumption in the recipient. In contrast, pre-transfusion recipient plasma haptoglobin levels inversely influenced post-transfusion fHb concentrations.

CONCLUSION

These data suggest that RBC transfusion can significantly increase post-transfusion plasma fHb levels and plasma NO consumption in the recipient. This finding may contribute to the potential pathophysiological mechanism underlying the much-discussed adverse relation between blood transfusions and patient outcome. This observation may be of particular importance for patients with substantial transfusion requirements.

Blood Product Storage

Red blood cell transfusion therapy has been used with the ultimate goal of enhancing oxygen delivery to vital organs and tissue beds, thus enhancing cellular function. Red blood cell transfusion therapy is also a long-standing practice, and since the 1950s it has only grown in utilization, especially within the United States. Recently, transfusion therapy has come under increased scrutiny with a desire to develop evidence-based therapeutic guidelines that not only decrease undue risk to the patient but also decrease the overutilization of this high-cost, low-availability product. Despite the development and implementation of these guidelines, significant complications associated with red cell therapy persist and may be related to storage of blood products. Recently, within the transfusion literature, there has been a renewed focus on red cell storage lesions and their contributions to perioperative outcomes. Several meta-analyses, and now a recently launched, multinational randomized controlled trial, have been initiated to help bring clarity to whether or not the length of product storage has any effect on patient outcomes. This review will focus on the nature of storage lesions, complications associated with storage, as well as a brief review of some of the more provocative literature surrounding this controversial topic.

Triggers of hospitalization for venous thromboembolism

BACKGROUND

The rate of hospitalization for venous thromboembolism (VTE) is increasing in the United States. Although predictors of hospital-acquired VTE are well-known, triggers of VTE before hospitalization are not as clearly defined. The objective of this study was to evaluate triggers of hospitalization for VTE.

METHODS AND RESULTS

A case-crossover study was conducted. Subjects were participants in the Health and Retirement Study, a nationally representative sample of older Americans. Data were linked to Medicare files for hospital and nursing home stays, emergency department visits, outpatient visits including physician visits, and home health visits from years 1991 to 2007 (n=16 781). The outcome was hospitalization for venous thromboembolism (n=399). Exposures during the 90-day period before hospitalization for VTE were compared with exposures occurring in 4 comparison periods. Infection was the most common trigger of hospitalization for VTE, occurring in 52.4% of the risk periods before hospitalization. The adjusted incidence rate ratios (IRRs; 95% confidence interval) were 2.90 (2.13, 3.94) for all infection, 2.63 (1.90, 3.63) for infection without a previous hospital or skilled nursing facility stay, and 6.92 (4.46, 10.72) for infection with a previous hospital or skilled nursing facility stay. Erythropoiesis-stimulating agents and blood transfusion were also associated with VTE hospitalization (IRR=9.33, 95% confidence interval: 1.19, 73.42; IRR=2.57, 95% confidence interval: 1.17, 5.64; respectively). Other predictors included major surgeries, fractures (IRR=2.81), immobility (IRR=4.23), and chemotherapy (IRR=5.70). These predictors, combined, accounted for a large proportion (69.7%) of exposures before VTE hospitalization as opposed to 35.3% in the comparison periods.

CONCLUSIONS

Risk prediction algorithms for VTE should be reevaluated to include infection, erythropoiesis-stimulating agents, and blood transfusion.

Hemolysis and cell-free hemoglobin drive an intrinsic mechanism for human disease

Blood transfusion represents the first and most prescribed cell-based therapy; however, clinical safety and efficacy trials are lacking. Clinical cohort studies have suggested that massive transfusion and/or transfusion of aged stored blood may contribute to multiorgan dysfunction in susceptible patients. In this issue of the JCI, Baek and colleagues report that aged stored blood hemolyzes after massive transfusion in a guinea pig model. Hemolysis led to vascular and kidney injury that was mediated by cell-free plasma hemoglobin and prevented by coinfusion of the specific hemoglobin scavenger protein, haptoglobin. These studies support an expanding body of research indicating that intravascular hemolysis is a pathological mechanism in several human diseases, including multiorgan dysfunction after either massive red blood cell transfusion or hemoglobin-based blood substitute therapy, the hemoglobinopathies, malaria, and other acquired and genetic hemolytic conditions.