Properties of stored red blood cells: understanding immune and vascular reactivity

CD71+ RBCs: A potential immune mediator in transfusion

Donor - recipient sex - mismatched transfusion is associated with increased mortality. The mechanisms for this are not clear, but it may relate to transfusion-related immunomodulation. Recently, CD71⁺ erythroid cells (CECs), including reticulocytes (CD71⁺ RBCs) and erythroblasts, have been identified as potent immunoregulatory cells. The proportion of CD71⁺ RBCs in the peripheral blood is sufficient to play a potential immunomodulatory role. Differences in the quantity of CD71⁺ RBCs are dependent on blood donor sex. The total number of CD71⁺ RBCs in red cell concentrates is also affected by blood manufacturing methods, and storage duration. As a component of the total CECs, CD71⁺ RBCs can affect innate and adaptive immune cells. Phagocytosed CECs directly reduce TNF-α production from macrophages. CECs can also suppress the production of TNF-α production from antigen presenting cells. Moreover, CECs can suppress T cell proliferation thorough immune mediation and / or direct cell-to-cell interactions. Different in their biophysical features compared to mature RBCs, blood donor CD71⁺ RBCs may be preferential targets for the macrophages. This report summarizes the currently literature supporting an important role for CD71⁺ RBCs in adverse transfusion reactions including immune mediation and sepsis.

Elevated IL-12, TNF-α, and TNF-α/IL-10 Ratios in Stored Plasmodium falciparum-Infected Whole Blood: Implications for Safe Haemotransfusion

Although Plasmodium falciparum infections in blood donors have been reported, the impact of parasitaemia on cytokine levels in stored whole blood has not been explored. This study evaluated the effect of P. falciparum parasitaemia on circulating cytokines and their relationship with haematological parameters in banked blood. In this case-control study, two groups of donor whole blood were recruited: P. falciparum-infected donors (parasitaemia: 515–1877 parasites/μL) and noninfected blood donors (control). At day 0 (baseline), 7, 14, 21, and 35 of banking circulating cytokine levels of tumor necrosis factor alpha (TNF-α), interleukin- (IL-) 12, IL-10, and IL-6 levels and haematological parameters were determined. Kruskal-Wallis test determined differences in weekly cytokine levels while Dunn's post hoc test determined exact significant points. At baseline, the mean TNF-α (33.81 pg/mL vs. 22.70 pg/mL), IL-12 (28.39 pg/mL vs. 16.15 pg/mL), IL-10 (51.04 pg/mL vs. 18.95 pg/mL), and IL-6 (71.03 pg/mL vs. 30.89 pg/mL) levels were significantly higher in infected donor whole blood. Significant rate of increase was observed in TNF-α, IL-12 levels, and TNF-α/IL-10 ratios in infected blood, while decreased levels were observed in IL-10. IL-6 peaked at day 21 and fell below baseline level at day 35. Significant changes in TNF-α, IL-12, IL-10, IL-6 levels, and TNF-α/IL-10 ratios in infected donor blood were observed 7 days after storage. Unlike in noninfected stored whole blood, TNF-α, IL-6, IL-12, and TNF-α/IL-10 ratio levels in infected stored whole blood related inversely to haematological parameters (white cells, red cells, platelets, and haemoglobin levels) during storage. However, in both groups, significant direct relationship was observed in IL-10 and haematological parameters. In conclusion, banking of P. falciparum-infected donor whole blood may lead to infusion of large quantities of inflammatory cytokines with potential adverse immunological response in recipients.

Effect of red blood cell storage duration on major postoperative complications in cardiac surgery: A randomized trial

BACKGROUND

Although observational studies suggest an association between transfusion of older red blood cell (RBC) units and increased postoperative risk, randomized trials have not supported this. The objective of this randomized trial was to test the effect of RBC storage age on outcomes after cardiac surgery.

METHODS

From July 2007 to May 2016, 3835 adults undergoing coronary artery bypass grafting, cardiac valve procedures, or ascending aorta repair, either alone or in combination, were randomized to transfusion of RBCs stored for ≤14 days (younger units) or for ≥20 days (older units) intraoperatively and throughout the postoperative hospitalization. According to protocol, 2448 patients were excluded because they did not receive RBC transfusions. Among the remaining 1387 modified intent-to-treat patients, 701 were randomized to receive younger RBC units (median age, 11 days) and the remaining 686 to receive older units (median age, 25 days). The primary endpoint was composite morbidity and mortality, analyzed using a generalized estimating equation (GEE) model. The trial was discontinued midway owing to enrollment constraints.

RESULTS

A total of 5470 RBC units were transfused, including 2783 in the younger RBC storage group and 2687 in the older RBC storage group. The GEE average relative-effect odds ratio was 0.77 (95% confidence interval [CI], 0.50-1.19; P = .083) for the composite morbidity and mortality endpoint. In-hospital mortality was lower for the younger RBC storage group (2.1% [n = 15] vs 3.4% [n = 23]), as was occurrence of other adverse events except for atrial fibrillation, although all CIs crossed 1.0.

CONCLUSIONS

This clinical trial, which was stopped at its midpoint owing to enrollment constraints, supports neither the efficacy nor the futility of transfusing either younger or older RBC units. The effects of transfusing RBCs after even more prolonged storage (35-42 days) remains untested.

Impact of stored red cells on clinical outcome in critically ill

BACKGROUND

The use and benefit of fresh blood and leuco-reduced blood for critically ill patients has been inconclusive. In this study we have tried to observe the same, in patients admitted to intensive care unit.

STUDY DESIGN AND METHODS

Prospective study was done to observe the effect of transfusion in critically ill patients in a tertiary care hospital. Clinical condition in cases and controls was assessed with the help of Simplified Acute Physiology Score II scoring tool. Clinical outcome among patients who received blood was compared using two cutoffs, 14 and 21 days of shelf life to delineate fresh from old blood. Length of hospital stay, length of stay in ICU, number of days on ventilator and number of hospital acquired infections were used as the surrogate markers for morbidity.

RESULTS

Of the 558 critically ill patients admitted during the study period, 427 received (cases) while 131 did not receive the transfusion (controls). Mean SAPS II scores of cases and controls were comparable. We observed a significantly higher rate of mortality among patients who received RBC units over 21 days. However morbidity parameters were affected even when the cutoff of 14 days is considered. Buffy-coat reduced blood did not influence the outcome in the study group.

CONCLUSION

Critically ill patients may be prioritized for receiving fresher units of packed red cells preferably less than 21 days old. Transfusion is an independent risk factor for morbidity. Hence the risk to benefit ratio should be carefully assessed for every red cell transfusion in critically ill patients.

Haematological quality and age of donor blood issued for paediatric transfusion to four hospitals in sub-Saharan Africa

BACKGROUND AND OBJECTIVES

Paediatric blood transfusion for severe anaemia in hospitals in sub-Saharan Africa remains common. Yet, reports describing the haematological quality of donor blood or storage duration in routine practice are very limited. Both factors are likely to affect transfusion outcomes.

MATERIALS AND METHODS

We undertook three audits examining the distribution of pack types, haematological quality and storage duration of donor blood used in a paediatric clinical trial of blood at four hospitals in Africa (Uganda and Malawi).

RESULTS

The overall distribution of whole blood, packed cells (plasma-reduced by centrifugation) and red cell concentrates (RCC) (plasma-reduced by gravity-dependent sedimentation) used in a randomised trial was 40·7% (N = 1215), 22·4% (N = 669) and 36·8% (N = 1099), respectively. The first audit found similar median haematocrits of 57·0% (50·0,74·0), 64·0% (52·0,72·5; P = 0·238 vs. whole blood) and 56·0% (48·0,67·0; P = 0·462) in whole blood, RCC and packed cells, respectively, which resulted from unclear pack labelling by blood transfusion services (BTS). Re-training of the BTS, hospital blood banks and clinical teams led to, in subsequent audits, significant differences in median haematocrit and haemoglobins across the three pack types and values within expected ranges. Median storage duration time was 12 days (IQR: 6, 19) with 18·2% (537/2964) over 21 days in storage. Initially, 9 (2·8%) packs were issued past the recommended duration of storage, dropping to 0·3% (N = 7) in the third audit post-training.

CONCLUSION

The study highlights the importance of close interactions and education between BTS and clinical services and the importance of haemovigilance to ensure safe transfusion practice.

Delineating the Effects of Ionizing Radiation on Erythropoietic Lineage-Implications for Radiation Biodosimetry

The overall lethality/morbidity of ionizing radiation exposure involves multiple forms of inhibitory or cytotoxic effects that may manifest in different tissues with a varying dose and time response. One of the major systemic effects leading to lethality of radiation includes its suppressive effect on hematopoiesis, which could be observed even at doses as low as 1-2 Gy, whereas effects on gastrointestinal and nervous systems appear at relatively higher doses in the same order. This article reviews the effects of radiation on the three distinct stages of erythropoiesis-formation of erythroid progenitor cells, differentiation of erythroid precursor cells, and terminal maturation. During these stepwise developmental processes, erythroid progenitor cells undergo rapid expansion to form terminally differentiated red blood cells that are continuously replenished from bone marrow into the circulating peripheral blood stream. Cellular radiation response depends upon many factors such as cell lineage, rate of proliferation, and differentiation status. Therefore, we discuss radiation-induced alterations during the progenitor, precursor, and terminal maturation stages and the implications thereof. Since biomarkers of ionizing radiation exposure in human populations are of great interest for assessing normal tissue injury as well as for biodosimetry in the event of accidental or incidental radiation exposures, we also highlight blood-based biomarkers that have potential utility for medical management.

Storage related haematological and biochemical changes in Plasmodium falciparum infected and sickle cell trait donor blood

Background

In sub-Saharan Africa where sickle cell trait (SCT) and malaria is prevalent, significant proportions of blood donors may be affected by one or more of these abnormalities. The haemato-biochemical properties of SCT and asymptomatic malaria in donor blood have not been evaluated. This study evaluated the haemato-biochemical impact of SCT and asymptomatic malaria infections in citrate-phosphate-dextrose-adenine (CPDA-1) stored donor blood units.

Methods

Fifty-milliliters of sterile CPDA-1 anti-coagulated blood were drained into the sample pouch attached to the main blood bag. Ten units each of sickle cell/malaria negative, sickle cell and malaria positive blood were analyzed. Baseline and weekly haematological profiling and week 1, 3 and 5 concentrations of plasma haemoglobin, % haemolysis, sodium, potassium and chloride and lactate dehydrogenase (LDH) were assayed. Differences between baseline and weekly data were determined using one-way analysis of variance (ANOVA) and Kruskal-Wallis test, whereas differences between baseline parameters and week 1-3 data pairs were determined using paired t-test. P-value < 0.05 was considered statistically significant.

Results

Storage of SCT and malaria infected blood affected all haematological cell lines. In the SCT donors, red blood cells (RBC) (4.75 × 10¹²/L ± 1.43^baseline to 3.49 × 10¹²/L ± 1.09^week-5), haemoglobin (14.45 g/dl ± 1.63^baseline to 11.43 g/dl ± 1.69^week-5) and haematocrit (39.96% ± 3.18^baseline to 33.22% ± 4.12^week-5) were reduced. In the asymptomatic malaria group, reductions were observed in RBC (5.00 × 10¹²/L ± 0.75^baseline to 3.72 × 10¹²/L ± 0.71^week-5), haemoglobin (14.73 g/dl ± 1.67^baseline to 11.53 g/dl ± 1.62^week-5), haematocrit (42.72% ± 5.16^baseline to 33.38% ± 5.80^week-5), mean cell haemoglobin concentration (35.48 g/dl ± 1.84^baseline to 35.01 g/dl ± 0.64^week-5) and red cell distribution width coefficient of variation (14.81% ± 1.54^baseline to 16.26% ± 1.37^week-5). Biochemically, whereas plasma LDH levels significantly increased in asymptomatic malaria blood donors (319% increase at week 5 compared to baseline), SCT blood donors had the most significant increase in plasma potassium levels at week 5 (382% increase). Sodium ions significantly reduced in SCT/malaria negative and sickle cell trait blood at an average rate of 0.21 mmol/L per day. Moreover, elevations in lymphocytes-to-eosinophils and lymphocytes-to-neutrophils ratios were associated with SCT and malaria positive blood whilst elevation lymphocytes-to-basophils ratio was exclusive to malaria positive blood.

Conclusion

Severe storage lesions were significant in SCT or malaria positive donor blood units. Proper clinical evaluation must be done in prospective blood donors to ensure deferral of such donors.

Review: In vitro generation of red blood cells for transfusion medicine: Progress, prospects and challenges

In vitro generation of red blood cells (RBCs) has the potential to circumvent the shortfalls in global demand for blood for transfusion applications. The conventional approach for RBC generation has been from differentiation of hematopoietic stem cells (HSCs) derived from cord blood, adult bone marrow or peripheral blood. More recently, RBCs have been generated from human induced pluripotent stem cells (hiPSCs) as well as from immortalized adult erythroid progenitors. In this review, we highlight the recent advances to RBC generation from these different approaches and discuss the challenges and new strategies that can potentially make large-scale in vitro generation of RBCs a feasible approach.

Transfusion of Red Blood Cells Stored More Than 28 Days is Associated With Increased Morbidity Following Spine Surgery

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to describe the association between storage duration of packed red blood cells (PRBCs) and perioperative adverse events in patients undergoing spine surgery at a tertiary care center.

SUMMARY OF BACKGROUND DATA

Despite retrospective studies that have shown that longer PRBC storage duration worsens patient outcomes, randomized clinical trials have found no difference in outcomes. However, no studies have examined the impact of giving the oldest blood (28 days old or more) on morbidity within spine surgery.

METHODS

The surgical administrative database at our institution was queried for patients transfused with PRBCs who underwent spine surgery between December 4, 2008, and June 26, 2015. Patients undergoing spinal fusion, tumor-related surgeries, and other identified spine surgeries were included. Patients were divided into two groups on the basis of storage duration of blood transfused: exclusively ≤28 days' storage or exclusively >28 days' storage. The primary outcome was composite in-hospital morbidity, which included (1) infection, (2) thrombotic event, (3) renal injury, (4) respiratory event, and/or (5) ischemic event.

RESULTS

In total, 1141 patients who received a transfusion were included for analysis in this retrospective study; 710 were transfused exclusively with PRBCs ≤28 days' storage and 431 exclusively with PRBCs >28 days' storage. Perioperative complications occurred in 119 patients (10.4%). Patients who received blood stored for >28 days had higher odds of developing any one complication [odds ratio (OR) = 1.82; 95% confidence interval (95% CI), 1.20-2.74; P = 0.005] even after adjusting for competing perioperative risk factors.

CONCLUSION

Blood stored for >28 days is independently associated with higher odds of developing perioperative complications in patients transfused during spinal surgery. Our results suggest that blood storage duration may be an appropriate parameter to consider when developing institutional transfusion guidelines that seek to optimize patient outcomes.

LEVEL OF EVIDENCE

3.

Mechanisms of red blood cell transfusion-related immunomodulation

Red blood cell (RBC) transfusion is common in critically ill, postsurgical, and posttrauma patients in whom both systemic inflammation and immune suppression are associated with adverse outcomes. RBC products contain a multitude of immunomodulatory mediators that interact with and alter immune cell function. These interactions can lead to both proinflammatory and immunosuppressive effects. Defining clinical outcomes related to immunomodulatory effects of RBCs in transfused patients remains a challenge, likely due to complex interactions between individual blood product characteristics and patient-specific risk factors. Unpacking these complexities requires an in-depth understanding of the mechanisms of immunomodulatory effects of RBC products. In this review, we outline and classify potential mediators of RBC transfusion-related immunomodulation and provide suggestions for future research directions.

Controlling Phlebotomy Volume Diminishes PICU Transfusion: Implementation Processes and Impact

BACKGROUND AND OBJECTIVES

Phlebotomy excess contributes to anemia in PICU patients and increases the likelihood of red blood cell transfusion, which is associated with risk of adverse outcomes. Excessive phlebotomy reduction (EPR) strategies may reduce the need for transfusion, but have not been evaluated in a PICU population. We hypothesized that EPR strategies, facilitated by implementation science methods, would decrease excess blood drawn and reduce transfusion frequency.

METHODS

Quantitative and qualitative methods were used. Patient and blood draw data were collected with survey and focus group data to evaluate knowledge and attitudes before and after EPR intervention. The Consolidated Framework for Implementation Research was used to interpret qualitative data. Multivariate regression was employed to adjust for potential confounders for blood overdraw volume and transfusion incidence.

RESULTS

Populations were similar pre- and postintervention. EPR strategies decreased blood overdraw volumes 62% from 5.5 mL (interquartile range 1-23) preintervention to 2.1 mL (interquartile range 0-7.9 mL) postintervention (P < .001). Fewer patients received red blood cell transfusions postintervention (32.1% preintervention versus 20.7% postintervention, P = .04). Regression analyses showed that EPR strategies reduced blood overdraw volume (P < .001) and lowered transfusion frequency (P = .05). Postintervention surveys reflected a high degree of satisfaction (93%) with EPR strategies, and 97% agreed EPR was a priority postintervention.

CONCLUSIONS

Implementation science methods aided in the selection of EPR strategies and enhanced acceptance which, in this cohort, reduced excessive overdraw volumes and transfusion frequency. Larger trials are needed to determine if this approach can be applied in broader PICU populations.

Red blood cell storage duration and long-term mortality in patients undergoing cardiac intervention: a Danish register study

OBJECTIVES

To study the effect of red blood cell (RBC) storage duration on long-term mortality in patients undergoing cardiac intervention.

BACKGROUND

RBCs undergo numerous structural and functional changes during storage. Observational studies have assessed the association between RBC storage duration and patient outcomes with conflicting results.

METHODS

Between January 2006 and December 2014, 82 408 patients underwent coronary angiography. Of these, 1856 patients received one to four RBC units within 30 days after this procedure. Patients were allocated according to length of RBC storage duration: short-term (≤11 days), intermediate (IM)-term (12-23 days) and long-term (≥24 days). The study endpoints were 30-day and long-term all-cause mortality.

RESULTS

A total of 4168 RBC units were given to 1856 patients. The mean RBC storage duration was 8.5 ± 2.1, 17.7 ± 3.4 and 29.9 ± 3.4 days in the short-term, IM-term and long-term storage groups, respectively. There was no difference in baseline characteristics between the groups. The long-term storage group received significantly more units (2.4 ± 1.0 units) as compared to the short-term (2.0 ± 1.0 units; P < 0.001) and IM-term storage group (2.2 ± 1.0 units; P < 0.01). In the survival analysis, there was no significant difference in all-cause mortality between the groups (log-rank: 0.509 for 30-days mortality; 0.493 for 5-year mortality). Additional stratified analysis demonstrated no association between RBC storage duration and long-term mortality.

CONCLUSION

This study did not find an association between RBC storage duration and 30-days or long-term mortality in patients undergoing cardiac intervention.

Enhancing uniformity and overall quality of red cell concentrate with anaerobic storage

BACKGROUND

Recent research focused on understanding stored red blood cell (RBC) quality has demonstrated high variability in measures of RBC function and health across units. Studies have historically linked this high variability to variations in processing, storage method, and age. More recently, a large number of studies have focused on differences in donor demographics, donor iron sufficiency, and genetic predisposition of the donor to poor storage, particularly through mechanisms of accelerated oxidative damage. A study was undertaken to evaluate a potential additional source of unit to unit variation in stored RBC: the role of variable percent oxygen saturation (%SO₂) levels on blood quality parameters during storage.

MATERIALS AND METHODS

%SO₂ data from 492 LR-RBC/AS-3 units used for internal and external collaborative research was included in the analysis. Whole blood units were processed into red blood cells, AS-3 added, leucocyte reduced, in compliance with American Association of Blood Banks guidelines. LR-RBC/AS-3 products were subsequently analysed for %SO₂ levels within 3-24 hours of phlebotomy using a co-oximeter. Separately, to evaluate the impact of pre-storage as well as increasing levels of %SO₂ during storage, a pool-and-split study was performed. Four units of LR-RBC/AS-3 were split 6 ways; "as is" (control), hyperoxygenated to more than 90%, and four levels of pre-storage %SO₂. The units were periodically sampled up to 42 days and analysed for %SO₂, pCO₂, methaemoglobin, ATP, 2,3-BPG as well as with the metabolomics workflow.

RESULTS

The measured mean %SO₂ in LR-RBC/AS-3 within 24 hours of collection was 45.9±17.5% with (32.7-61.0 IQR). %SO₂ in all products increased to approximately 95-100% in three weeks. Measured blood quality parameters including ATP, % haemolysis, methaemoglobin, oxidised lipids, and GSH/GSSG indicated suppressed cellular metabolism and increased red cell degradation in response to higher %SO₂ levels.

DISCUSSION

The surprisingly high variability in starting %SO₂ levels, coupled with negative impacts of high oxygen saturation on red blood cell quality indicates that oxygen levels may be an important and under-appreciated source of unit-to-unit variability in RBC quality.

A retrospective analysis of the effect of blood transfusion on cerebral oximetry entropy and acute kidney injury

Purpose:

Acute anemia is associated with both cerebral dysfunction and acute kidney injury and is often treated with red blood cell transfusion. We sought to determine if blood transfusion changed the cerebral oximetry entropy, a measure of the complexity or irregularity of the oximetry values, and if this change was associated with subsequent acute kidney injury.

Methods:

This was a retrospective, case-control study of patients undergoing cardiac surgery with cardiopulmonary bypass at a tertiary care hospital, comparing those who received a red blood cell transfusion to those who did not. Acute kidney injury was defined as a perioperative increase in serum creatinine by ⩾26.4 μmol/L or by ⩾50% increase. Entropy was measured using approximate entropy, sample entropy, forbidden word entropy and basescale4 entropy in 500-point sets.

Results:

Forty-four transfused patients were matched to 88 randomly selected non-transfused patients. All measures of entropy had small changes in the transfused group, but increased in the non-transfused group (p<0.05, for all comparisons). Thirty-five of 132 patients (27%) suffered acute kidney injury. Based on preoperative factors, patients who suffered kidney injury were similar to those who did not, including baseline cerebral oximetry levels. After analysis with hierarchical logistic regression, the change in basescale4 entropy (odds ratio = 1.609, 95% confidence interval = 1.057–2.450, p = 0.027) and the interaction between basescale entropy and transfusion were significantly associated with subsequent development of acute kidney injury.

Conclusions:

The transfusion of red blood cells was associated with a smaller rise in entropy values compared to non-transfused patients, suggesting a change in the regulation of cerebral oxygenation, and these changes in cerebral oxygenation are also associated with acute kidney injury.

Blood Products

Perioperative hemorrhage, anemia, thrombocytopenia, and coagulopathy are common in the surgical intensive care unit. As a result, blood product transfusion occurs frequently. While red blood cell, plasma, and platelet transfusions have a lifesaving role in the resuscitation of patients with trauma and hemorrhagic shock, their application in other settings is under scrutiny. Current data would suggest a conservative approach be taken, thus avoiding unnecessary transfusion and associated potential adverse events. New and developmental products such as prothrombin complex concentrates offer appealing alternatives to traditional transfusion practice—potentially with fewer risks—however, further investigation into their safety and efficacy is required before practice change can take place.

Techniques to improve detection and analysis of extracellular vesicles using flow cytometry

Extracellular vesicles (EVs) range in size from 50 nm to 1 µm. Flow cytometry (FCM) is the most commonly used method for analyzing EVs; however, accurate characterization of EVs remains challenging due to their small size and lack of discrete positive populations. Here we report the use of optimization techniques that are especially well-suited for analyzing EVs from a high volume of clinical samples. Utilizing a two pronged approach that included 1) pre-filtration of antibodies to remove aggregates, followed by 2) detergent lysis of a replicate sample to account for remaining false positive events, we were able to effectively limit false positive non-EV events. In addition, we show that lysed samples are a useful alternative to isotypes for setting gates to exclude background fluorescence. To reduce background, we developed an approach using filters to "wash" samples post-staining thus providing a faster alternative to ultracentrifugation and sucrose gradient fractionation. In conclusion, use of these optimized techniques enhances the accuracy and efficiency of EV detection using FCM.

Clinical effects of red blood cell storage

BACKGROUND

Well-characterized biochemical, structural, and physiological changes occur when red blood cells (RBCs) are stored for a period of time and are collectively called the storage lesion.

METHODS

Key study results are summarized and contrasted and new data from recently completed randomized controlled trials will be discussed.

RESULTS

It is unclear whether in vitro changes to RBCs that occur during storage are clinically relevant. The clinical effects of RBC storage have been the focus of observational studies in recent years. However, these studies lack any consensus, possibly because of methodological limitations.

CONCLUSIONS

The clinical significance of storing RBCs is controversial, although new data from randomized controlled trials of neonates and patients undergoing cardiac surgery suggest that the duration of RBC storage is not associated with adverse clinical outcomes in these patient populations.

All plasma products are not created equal: Characterizing differences between plasma products

BACKGROUND

Plasma can be manufactured by multiple methods. Few studies have compared quality parameters between plasma products that may affect efficacy and safety.

METHODS

Four different plasma products were analyzed to include fresh frozen plasma (FFP), liquid plasma (LP), solvent detergent plasma (SDP), and a spray-dried, solvent detergent-treated plasma (SD-SDP) at multiple time points of storage. Parameters measured included red blood cell, platelet, and white blood cell counts; microparticle phenotypes; thrombin generation; and thrombelastography. These parameters were compared in 10 samples of each product.

RESULTS

SDP and SD-SDP contained the smallest number of residual cells compared with FFP and LP. Platelets were the most common residual cell in all products and were highest in LP. FFP contained the greatest number of residual red blood cells. Total microparticle counts were elevated in LP and FFP compared with SDP and SD-SDP. Cell-derived microparticles in both LP and FFP were mostly platelet in origin. Microparticle counts in SDP and SD-SDP were negligible. Thrombelastography results demonstrated similar thrombin, fibrinogen, and platelet function on Day 28 LP compared with Day 5 thawed FFP. Thrombin generation assays revealed that the total, lag time to, and peak thrombin formation were higher in SDP and SD-SDP compared with FFP and LP. All parameters in FFP and LP products were characterized by a large degree of variability.

CONCLUSION

The differences in cellular, microparticle, and functional hemostatic parameters measured between plasma products have the potential to affect efficacy and safety. Further study is needed to elucidate the potential immune effects of the cellular and microparticle differences noted as well as the clinical implications of altered thrombin generation kinetics in SD products.

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.

The influence of the storage lesion(s) on pediatric red cell transfusion

PURPOSE OF REVIEW

This article will analyze and evaluate the current evidence regarding the use of older, longer-stored red blood cells (RBCs) for transfusion in pediatric patients and will examine some of the postulated mechanisms of injury related to prolonged refrigerated storage of RBCs and studies reporting clinical outcomes.

RECENT FINDINGS

Three randomized controlled trials and seven observational studies have been conducted entirely in pediatric patients. The outcomes, mortality and morbidity in critically ill patients and children undergoing cardiac surgery, and necrotizing enterocolitis in premature infants, have been inconsistent. However, many of these studies have been confounded by study design, mixed patient populations, red cell preparation, and other factors.

SUMMARY

Further exploration into the possible deleterious effects of older, longer-stored RBC transfusions on mortality and morbidity in different pediatric populations is merited. Understanding the potential mechanisms of injury should help explain the clinical findings.

Age of transfused blood in critically ill adults

BACKGROUND

Fresh red cells may improve outcomes in critically ill patients by enhancing oxygen delivery while minimizing the risks of toxic effects from cellular changes and the accumulation of bioactive materials in blood components during prolonged storage.

METHODS

In this multicenter, randomized, blinded trial, we assigned critically ill adults to receive either red cells that had been stored for less than 8 days or standard-issue red cells (the oldest compatible units available in the blood bank). The primary outcome measure was 90-day mortality.

RESULTS

Between March 2009 and May 2014, at 64 centers in Canada and Europe, 1211 patients were assigned to receive fresh red cells (fresh-blood group) and 1219 patients were assigned to receive standard-issue red cells (standard-blood group). Red cells were stored a mean (±SD) of 6.1±4.9 days in the fresh-blood group as compared with 22.0±8.4 days in the standard-blood group (P<0.001). At 90 days, 448 patients (37.0%) in the fresh-blood group and 430 patients (35.3%) in the standard-blood group had died (absolute risk difference, 1.7 percentage points; 95% confidence interval [CI], -2.1 to 5.5). In the survival analysis, the hazard ratio for death in the fresh-blood group, as compared with the standard-blood group, was 1.1 (95% CI, 0.9 to 1.2; P=0.38). There were no significant between-group differences in any of the secondary outcomes (major illnesses; duration of respiratory, hemodynamic, or renal support; length of stay in the hospital; and transfusion reactions) or in the subgroup analyses.

CONCLUSIONS

Transfusion of fresh red cells, as compared with standard-issue red cells, did not decrease the 90-day mortality among critically ill adults. (Funded by the Canadian Institutes of Health Research and others; Current Controlled Trials number, ISRCTN44878718.).

Peroxiredoxin-2 recycling is inhibited during erythrocyte storage

AIMS

Transfusion with stored red blood cells (RBCs) is associated with increased morbidity and mortality. Peroxiredoxin-2 (Prx-2) is a primary RBC antioxidant that limits hydrogen peroxide (H2O2)-mediated toxicity. Whether Prx-2 activity is altered during RBC storage is not known.

RESULTS

Basal and H2O2-induced Prx-2 activity was measured in RBCs (stored for 7-35 days). Basal Prx-2 thiol oxidation increased with RBC age, whereas H2O2-dependent formation of dimeric Prx-2 was similar. However, reduction of Prx-2 dimers to monomers became progressively slower with RBC storage, which was associated with increased H2O2-induced hemolysis. Surprisingly, no change in the NADPH-dependent thioredoxin (Trx)/Trx-reductase system, which recycles dimeric Prx-2, was observed in stored RBCs. Using mouse RBCs expressing human wild type (β93Cys) or hemoglobin (Hb) in which the conserved β93Cys residue is replaced by Ala (β93Ala), a role for this thiol in modulating Prx-2 reduction was demonstrated. Specifically, Prx-2 recycling was blunted in β93Ala RBC, which was reversed by carbon monoxide-treatment, suggesting that heme autoxidation-derived H2O2 maintains Prx-2 in the oxidized form in these cells. Moreover, assessment of the oxidative state of the β93Cys in RBCs during storage showed that while it remained reduced on intraerythrocytic Hb in stored RBC, it was oxidized to dehydroalanine on hemolyzed or extracellular Hb.

INNOVATION

A novel mechanism for regulated Prx-2 activity in RBC via the β93Cys residue is suggested.

CONCLUSION

These data highlight the potential for slower Prx-2 recycling and β93Cys oxidation in modulating storage-dependent damage of RBCs and in mediating post-transfusion toxicity.

Red blood cell storage duration and trauma

Numerous retrospective clinical studies suggest that transfusion of longer stored red blood cells (RBCs) is associated with an independent risk of poorer outcomes for certain groups of patients, including trauma, intensive care, and cardiac surgery patients. Large multicenter randomized controlled trials are currently underway to address the concern about RBC storage duration. However, none of these randomized controlled trials focus specifically on trauma patients with hemorrhage. Major trauma, particularly due to road accidents, is the leading cause of critical injury in the younger-than-40-year-old age group. Severe bleeding associated with major trauma induces hemodynamic dysregulation that increases the risk of hypoxia, coagulopathy, and potentially multiorgan failure, which can be fatal. In major trauma, a multitude of stress-associated changes occur to the patient's RBCs, including morphological changes that increase cell rigidity and thereby alter blood flow hemodynamics, particularly in the microvascular vessels, and reduce RBC survival. Initial inflammatory responses induce deleterious cellular interactions, including endothelial activation, RBC adhesion, and erythrophagocytosis that are quickly followed by profound immunosuppressive responses. Stored RBCs exhibit similar biophysical characteristics to those of trauma-stressed RBCs. Whether transfusion of RBCs that exhibit storage lesion changes exacerbates the hemodynamic perturbations already active in the trauma patient is not known. This article reviews findings from several recent nonrandomized studies examining RBC storage duration and clinical outcomes in trauma patients. The rationale for further research on RBC storage duration in the trauma setting is provided.

Role of transfused red blood cells for shock and coagulopathy within remote damage control resuscitation

The philosophy of damage control resuscitation (DCR) and remote damage control resuscitation (RDCR) can be summarized by stating that the goal is to prevent death from hemorrhagic shock by "staying out of trouble instead of getting out of trouble." In other words, it is preferred to arrest the progression of shock, rather than also having to reverse this condition after significant tissue damage and organ injury cascades are established. Moreover, to prevent death from exsanguination, a balanced approach to the treatment of both shock and coagulopathy is required. This was military doctrine during World War II, but seemed to be forgotten during the last half of the 20th century. Damage control resuscitation and RDCR have revitalized the approach, but there is still more to learn about the most effective and safe resuscitative strategies to simultaneously treat shock and hemorrhage. Current data suggest that our preconceived notions regarding the efficacy of standard issue red blood cells (RBCs) during the hours after transfusion may be false. Standard issue RBCs may not increase oxygen delivery and may in fact decrease it by disturbing control of regional blood flow distribution (impaired nitric oxide processing) and failing to release oxygen, even when perfusing hypoxic tissue (abnormal oxygen affinity). Standard issue RBCs may assist with hemostasis but appear to have competing effects on thrombin generation and platelet function. If standard issue or RBCs of increased storage age are not optimal, then are there alternatives that will allow for an efficacious and safe treatment of shock while also supporting hemostasis? Studies are required to determine if fresh RBCs less than 7 to 10 days provide an outcome advantage. A resurgence in the study of whole blood stored at 4°C for up to 10 days also holds promise. Two randomized controlled trials in humans have indicated that following transfusion with either whole blood stored at 4°C or platelets stored at 4°C there was less clinical bleeding than when blood was reconstituted with components or when platelets were stored at 22°C. Early reversal of shock is essential to prevent exacerbation of coagulopathy and progression of cell death cascades in patients with severe traumatic injuries. Red blood cell storage solutions have evolved to accommodate the needs of non-critically ill patients yet may not be optimal for patients in hemorrhagic shock. Continued focus on the recognition and treatment of shock is essential for continued improvement in outcomes for patients who require damage control resuscitation and RDCR.

One size will never fit all: the future of research in pediatric transfusion medicine

There is concern at the National Heart, Lung, and Blood Institute (NHLBI) and among transfusion medicine specialists regarding the small number of investigators and studies in the field of pediatric transfusion medicine (PTM). Accordingly, the objective of this article is to provide a snapshot of the clinical and translational PTM research considered to be of high priority by pediatricians, neonatologists, and transfusion medicine specialists. Included is a targeted review of three research areas of importance: (i) transfusion strategies, (ii) short- and long-term clinical consequences, and (iii) transfusion-transmitted infectious diseases. The recommendations by PTM and transfusion medicine specialists represent opportunities and innovative strategies to execute translational research, observational studies, and clinical trials of high relevance to PTM. With the explosion of new biomedical knowledge and increasingly sophisticated methodologies over the past decade, this is an exciting time to consider transfusion medicine as a paradigm for addressing questions related to fields such as cell biology, immunology, neurodevelopment, outcomes research, and many others. Increased awareness of PTM as an important, fertile field and the promotion of accompanying opportunities will help establish PTM as a viable career option and advance basic and clinical investigation to improve the health and wellbeing of children.

Impact of the age of transfused red blood cells in the trauma population: a feasibility study

Following injury, transfusion of red blood cells (RBCs) of increased storage duration has been associated with an increased morbidity and mortality. Prospective trials focusing on the impact of the storage age of RBCs in severely bleeding trauma patients have failed to accrue patients. This has been attributed to an inability to maintain a large inventory of fresh RBCs, and the difficulties in obtaining consent in severely bleeding trauma patients. To address these issues, we performed a prospective, observational pilot study to evaluate the feasibility of conducting a trial focusing on RBC age in patients following injury.

METHODS

Patients with bleeding due to trauma were transfused RBCs ≤10 day old if they were ABO blood Type O (Group O) or were transfused the oldest RBCs in inventory if they were Type A, B or AB (Group A/B/AB). Clinicians were unaware of the specific age of the RBCs.

RESULTS

63 patients were analyzed (Group O, n=19; Group A/B/AB, n=44). Half of all patients had severe injuries ISS (median 22). The median admission base deficit was -5 mEq/L, and median total 24h use of RBC and FFP was 1.2 L. The age of RBCs transfused to Group O was significantly lower than for Group A/B/AB [median (IQR) A/B/AB=18.4 (11.4-25.4) days, and Group O=6 (4.2-7.8) days; p<0.001].

CONCLUSIONS

It appears feasible to conduct a RBC age trial in trauma patients using ABO blood type to construct comparative groups. Adequate RBC age separation between cohorts and reduced RBC age in the "young" group of patients who received units ≤10 days old was achieved.

Storage duration of red blood cell transfusion and Clostridium difficile infection: a within person comparison

OBJECTIVE

Randomized controlled trials demonstrated that red blood cell (RBC) transfusion elevates the risk of infection, and trials are underway to evaluate whether RBC storage affects outcomes. We previously reported that transfusion predicts Clostridium difficile infection (CDI) and, therefore, planned an investigation to examine this further using a more robust design.

DESIGN

Within-person case-crossover study. Hospitalizations in which CDI developed (n = 406) were compared to hospitalizations for the same individuals in which CDI did not occur (n = 949). Transfusion volume and storage duration were assessed prior to the onset of CDI.

SETTING

University of Michigan Health System.

PATIENTS

Participants were individuals with a diagnosis of CDI from July 2009 through June 2012.

MEASUREMENTS AND MAIN RESULTS

During the hospitalizations when CDI occurred, 34.7% of the patients received allogeneic RBC transfusions (mean volume, 688 ml) compared to 19.0% of patients in hospitalizations without CDI (mean volume, 180 ml). The odds of healthcare-associated CDI increased by 76% (95% CI 1.39-2.23) for every liter of RBCs transfused and was elevated in both nonsurgical (OR = 1.90) and surgical (OR = 1.86) hospitalizations. In patients who received RBC transfusions, the odds of developing CDI increased by 6% for every additional day of RBC stored and by 53% for every week of additional storage (P = 0.002).

CONCLUSIONS

Hospitalizations in which a patient received a greater volume of RBC transfusions were more likely to be associated with the development of CDI. RBC units stored for a longer duration were associated with the development of healthcare-associated CDI after adjustment for RBC volume.

Exosomes from red blood cell units bind to monocytes and induce proinflammatory cytokines, boosting T-cell responses in vitro

Extracellular vesicles (EVs) are small, double membrane vesicles derived from leukocytes, platelets, and cells of other tissues under physiological or pathological conditions. Generation of EVs in stored blood is thought to be associated with adverse effects and potentially immunosuppression in blood transfusion recipients. We measured the quantity and cells of origin for EVs isolated from stored red blood cell (RBC) units and tested whether they had any effects on T-cell-mediated immune responses. Mixing peripheral blood mononuclear cells (PBMCs) with EVs resulted in secretion of proinflammatory cytokines and chemokines and increased survival of unstimulated PBMCs. EVs augmented mitogen-induced CD4(+) and CD8(+) T-cell proliferation in an antigen-presenting cell (APC)-dependent manner. We demonstrated that EVs interacted primarily with monocytes and induced proinflammatory cytokine secretion. We also showed that the exosome fraction of EVs and not larger microvesicles was responsible for induction of TNF-α production by monocytes. Furthermore, blockade of CD40 or CD40L accessory molecules largely neutralized the EV augmentation of T-cell responses, implying a role for cell-cell interaction between T cells and EV-activated monocytes. Contrary to our hypothesis, the data demonstrate that EVs isolated from RBC units increase the potency of APCs and boost mitogen-driven T-cell proliferative responses.

Effects of non-leukocyte-reduced and leukocyte-reduced packed red blood cell transfusions on oxygenation of rat spinotrapezius muscle

Leukoreduction of blood used for transfusion alleviates febrile transfusion reactions, graft versus host disease and alloimmunization to leukocyte antigen. However, the actual clinical benefit of leukoreduction in terms of microcirculatory tissue O2 delivery after packed red blood cell (pRBC) transfusion has not been investigated. As such, the aim of this study was to determine the effects of non-leukoreduced (NLR) and leukoreduced (LR) fresh pRBC transfusion on interstitial oxygenation in anesthetized male Sprague-Dawley rats. Interstitial fluid PO2 and arteriolar diameters in spinotrapezius muscle preparations were monitored before and after transfusion with NLR- or LR-pRBCs. The major findings were that (1) transfusion of NLR-pRBCs significantly decreased interstitial oxygenation whereas transfusion of LR-pRBCs did not, and (2) transfusion with LR-pRBCs elicited a substantially greater increase in arterial blood pressure (ABP) than did transfusion with NLR-pRBCs. These changes in PO2 and ABP were not associated with changes in the diameters of resistance arterioles in the spinotrapezius muscle. These data suggest that transfusion of fresh NLR-pRBCs may negatively affect tissue oxygenation via enhanced leukocyte influx and decreased O2 delivery. They also suggest that leukocytes diminish the capability of transfused pRBCs to increase cardiac output. As such, transfusion of LR-pRBCs may be less deleterious on tissue PO2 levels than NLR-pRBCs although a concomitantly greater increase in ABP may accompany transfusion of LR-pRBCs.

Red blood cell storage: how long is too long?

Red blood cells (RBCs) undergo biochemical and structural changes during storage, commonly referred to as the "storage lesion." Evidence suggests that the longer the RBC product is stored, the less effective is the transfused blood. Many studies linking morbidity to transfusion have not considered duration of RBC storage as a variable that may modulate the effect. In addition, the effects of supply and demand and RBC inventory management strategies have been incompletely investigated. It is possible to envision a blood management system based on modern inventory management strategies that could greatly reduce storage duration.

In vitro measures of membrane changes reveal differences between red blood cells stored in saline-adenine-glucose-mannitol and AS-1 additive solutions: a paired study

BACKGROUND

Saline-adenine-glucose-mannitol (SAGM) and a variant solution, AS-1, have been used for more than 30 years to preserve red blood cells (RBCs). Reputedly these RBC components have similar quality, although no paired study has been reported. To determine whether differences exist, a paired study of SAGM RBCs and AS-1 RBCs was conducted to identify membrane changes, including microparticle (MP) quantitation and in vitro RBC-endothelial cell (EC) interaction.

STUDY DESIGN AND METHODS

Two whole blood packs were pooled and split and RBCs were prepared (n=6 pairs). One pack was suspended in SAGM and one in AS-1. Samples were collected during 42 days of refrigerated storage. RBC shape and size and glycophorin A (GPA)(+) and phosphatidylserine (PS)(+) MPs were measured by flow cytometry. RBC adhesion to ECs was determined by an in vitro flow perfusion assay. Routine variables (pH, hemolysis) were also measured.

RESULTS

Compared to SAGM RBCs, AS-1 RBCs had lower hemolysis (p<0.04), lower GPA(+) MPs (p<0.03), and lower PS(+) MPs (p<0.03) from Day 14 onward. AS-1 RBCs had higher (p<0.02) side scatter from Day 28 onward compared to SAGM RBCs. SAGM RBCs were more adherent to ECs on Day 28 of storage compared to AS-1 RBCs (p=0.04), but reversed on Day 42 (p=0.02).

CONCLUSION

SAGM RBCs lose more membrane during storage. SAGM RBCs had increased adherence to ECs on Day 28 of storage, while AS-1 RBCs were more adherent on Day 42. The effect of these differences on the function and survival of SAGM RBCs and AS-1 RBCs after transfusion remains to be determined.

Relationship between red cell storage duration and outcomes in adults receiving red cell transfusions: a systematic review

INTRODUCTION

The duration of red blood cell (RBC) storage before transfusion may alter RBC function and supernatant and, therefore, influence the incidence of complications or even mortality.

METHODS

A MEDLINE search from 1983 to December 2012 was performed to identify studies reporting age of transfused RBCs and mortality or morbidity in adult patients.

RESULTS

Fifty-five studies were identified; most were single-center (93%) and retrospective (64%), with only a few, small randomized studies (eight studies, 14.5%). The numbers of subjects included ranged from eight to 364,037. Morbidity outcomes included hospital and intensive care unit (ICU) length of stay (LOS), infections, multiple organ failure, microcirculatory alterations, cancer recurrence, thrombosis, bleeding, vasospasm after subarachnoid hemorrhage, and cognitive dysfunction. Overall, half of the studies showed no deleterious effects of aged compared to fresh blood on any endpoint. Eleven of twenty-two (50%) studies reported no increased mortality, three of nine (33%) showed no increased LOS with older RBCs and eight of twelve (66%) studies showed no increased risks of organ failure. Ten of eighteen (55%) studies showed increased infections with transfusion of older RBCs. The considerable heterogeneity among studies and numerous methodological flaws precluded a formal meta-analysis.

CONCLUSIONS

In this systematic review, we could find no definitive argument to support the superiority of fresh over older RBCs for transfusion.

The acute coagulopathy of trauma: mechanisms and tools for risk stratification

Trauma remains the leading cause of death, with bleeding as the primary cause of preventable mortality. When death occurs, it happens quickly, typically within the first 6 h after injury. The principal drivers of the acute coagulopathy of trauma have been characterized, but another group of patients with early evidence of coagulopathy both physiologically and mechanistically distinct from this systemic acquired coagulopathy has been identified. This distinct phenotype is present in 25% to 30% of patients with major trauma without being exposed to the traditional triggers and is associated with higher morbidity and a 4-fold increase in mortality. Despite improvements in the resuscitation of exsanguinating patients, one of the remaining keys is to expeditiously and reproducibly identify the patients most likely to require transfusion including massive transfusion with damage control resuscitation principles. Several predictive scoring systems/algorithms for transfusion including massive transfusion in both civilian and military trauma populations have been introduced. The models developed usually suggest combinations of physiologic, hemodynamic, laboratory, injury severity, and demographic triggers identified on the initial evaluation. Many use a combination of dichotomous variables that are readily accessible after the patient's arrival to the trauma bay, but others rely on time-consuming mathematical calculations and may thus have limited real-time application. Weighted and more sophisticated systems including higher numbers of variables perform superiorly. A common limitation to all models is their retrospective nature, and prospective validations are needed. Point-of-care viscoelastic testing may be an alternative to early recognize trauma-induced coagulopathy with the risk of ongoing hemorrhage and transfusion.

Critically ill and septic patient: is red blood cell transfusion adding to the Domino Effect?

Sepsis is a major cause of patient morbidity and mortality. Many critically ill patients are septic, and red blood cell transfusion is often part of their treatment plan. Studies have shown that red blood cell transfusion is associated with a dose-dependent increase in patient morbidity and mortality. Although red blood cells are transfused to increase the recipient's oxygen-carrying capacity, there are new and emerging data to support that red blood cell transfusion may potentially decrease perfusion and oxygen delivery to the microcirculation, particularly when older red blood cells are transfused. In addition, there are similar effects in the pathophysiology of sepsis that may overlap with the changes that occur with storage of red blood cells. This article will discuss recent literature addressing red cell transfusion in critically ill and septic patients and discuss general guidelines for red cell transfusion in this patient population. This article will also discuss the epidemiology and pathophysiology of sepsis and relate how storage and transfusion of red cells may potentially contribute to changes observed in a septic patient.

Clinical and economic outcomes associated with blood transfusions among elderly Americans following coronary artery bypass graft surgery requiring cardiopulmonary bypass

BACKGROUND

Blood transfusion occurring during hospitalisation for heart surgery has been shown to be associated with increased morbidity and mortality and with increased time spent in hospital, use of healthcare services, and costs. The objective of this study was to assess how perioperative blood transfusion among adults 65 years and older who underwent coronary artery bypass graft surgery requiring cardiopulmonary bypass in the United States is associated with immediate and longer term clinical and economic outcomes.

MATERIALS AND METHODS

Using data from a 5% random sample of Medicare patients who underwent their first (within 2 years) coronary artery bypass graft requiring cardiopulmonary bypass procedure in 2005 or 2006, this study estimated associations (hazard ratios and regression coefficients) between transfusion status (received or not) and complications after surgery, serious adverse events, death, and costs using Cox proportional hazard and generalised linear models adjusting for patients' demographic and clinical characteristics.

RESULTS

Adjusted hazard ratios were statistically significant (P<0.05) for risks of complications (1.20), serious adverse events (1.58), and death (1.49). There was also a statistically significantly (P≤0.01) and strong relationship between receiving transfused blood and Medicare payments over the subsequent 45 months following discharge ($5,778 per calendar quarter for those receiving transfusion vs $5,197; all costs are measured in 2011 USD).

CONCLUSION

Blood transfusion during hospitalisation for coronary artery bypass graft requiring cardiopulmonary bypass was significantly associated with increased long-term post-operative morbidity, mortality, and overall healthcare costs. This study contributes to the evidence demonstrating an association between transfusion and adverse clinical and economic outcomes by using a nationally representative longitudinal cost and utilisation database.

Extracellular vesicles in the circulation: are erythrocyte microvesicles a confounder in the plasma haemoglobin assay?

Blood contains a mixture of extracellular vesicles from different cell types, primarily platelets, endothelial cells, leucocytes and erythrocytes. Erythrocytes are the most abundant cell type in blood and could, especially in certain pathologies, represent an important source of vesicles. Since erythrocytes contain the haemoglobin components iron and haem, which are potentially toxic, it is important to investigate the contribution of vesicle-associated haemoglobin to total cell-free haemoglobin levels. To our knowledge, this is the first time that cell-free plasma haemoglobin has been differentiated into vesicle-associated and molecular species. We investigated the contribution of vesicle-associated haemoglobin in residual patient material that was routinely analysed for total cell-free plasma haemoglobin. All patient samples included in the study were haemolytic with total cell-free haemoglobin concentration ranging from 80 to 2500 mg/l. In the majority of the samples, total cell-free haemoglobin concentration was between 100 and 200 mg/l. No haemoglobin could be detected in the vesicle fraction, indicating that the contribution of vesicle-associated haemoglobin to total cell free-haemoglobin levels in plasma is negligible. It is important to investigate whether erythrocyte vesicles are not formed in blood or that their production is not increased during pathologies associated with haemolysis or that the clearance rate of the vesicles surpasses the formation rate.

Oxygen delivery during extreme anemia with ultra-pure earthworm hemoglobin

AIM

Lumbricus terrestris (earthworm) erythrocruorin (LtEc) is a naturally occurring extracellular hemoglobin (Hb) with high molecular weight (3.6MDa), low autoxidation rate, and limited nitric oxide (NO) dioxygenation activity. These properties make LtEc a potential candidate for use as red blood cell (RBC) substitute, i.e. Hb-based oxygen carrier (HBOC). Previous studies have shown that small amounts of LtEc can be safely transfused into mice, rats, and hamsters without eliciting major side effects. Therefore, this study was designed to understand oxygen (O(2)) transport to tissues and systemic/microvascular hemodynamics induced by LtEc during anemic conditions.

MAIN METHODS

Hamsters fitted with dorsal window chambers were hemodiluted to 18% hematocrit (Hct) using 6g/dL dextran 70kDa (Dex70). Hemodilution was then continued to 11% Hct using 10g/dL LtEc, 6g/dL Dex70 or 10g/dL human serum albumin (HSA). Blood pressure, heart rate, blood gas parameters, microvascular hemodynamics, microvascular blood flow, functional capillary density (FCD), intravascular pO(2) and perivascular pO(2) were studied.

KEY FINDINGS

LtEc maintained blood pressure without inducing vasoconstriction while increasing microvascular perfusion and FCD relative to Dex70 and HSA. LtEc increased blood O(2) carrying capacity and maintained systemic and microvascular parameters without decreasing arteriolar diameter or increasing vascular resistance with during extreme anemia. LtEc increased O(2) delivery compared to conventional plasma expanders.

SIGNIFICANCE

LtEc or synthetic molecules that replicate the characteristics of LtEc could be effective O(2) carriers with potential to be used in transfusion medicine to prevent tissue anoxia resulting from severe anemia.

Deformability of Red Blood Cells and Correlation with ATP Content during Storage as Leukocyte-Depleted Whole Blood

BACKGROUND: Storage duration of red cells has been associated with increased morbidity and mortality following transfusion. This association has been attributed to the loss of deformability of stored red cells leading to deterioration of microvascular perfusion. ATP content is considered a critical determinant of the deformability of stored red cells. METHODS: ATP content and deformability were determined after storage for up to 49 days in 40 leukocyte-depleted whole blood units. Red cell deformability was determined using a laser-assisted optical rotational cell analyzer (LORCA( (®) )) employing shear stress (SS) ranging from 0.3 to 30 Pa. Deformability was expressed as the elongation index (EI). EI was correlated with ATP content. RESULTS: ATP content decreased from 3.5 to 1.7 ?mol/g hemoglobin. EI increased from 0.03 to 0.05 at an SS of 0.3 Pa, and decreased from 0.62 to 0.59 at an SS of 30 Pa. Correlation coefficient (r) of ATP vs. EI at 0.3 Pa ranged from -0.17 to +0.15 during storage. At 30 Pa, r ranged from -0.03 to +0.45. Correlation increased with storage irrespective of SS, and increased with SS irrespective of storage. CONCLUSIONS: ATP content is not a valid surrogate marker for red cell deformability and may not reflect in vivo survival of stored red cells.

Stored red blood cell transfusions: Iron, inflammation, immunity, and infection

The potential adverse effects of transfusion of red blood cells after prolonged storage have been hotly debated. During refrigerated storage, red blood cells are damaged, a process known as the red blood cell "storage lesion." We hypothesized that the delivery of a bolus of iron derived from these rapidly cleared, damaged, red blood cells is responsible for some of the adverse effects of transfusion. Iron may play a role in producing a pro-inflammatory response to transfused red blood cells, potentially through the effects of reactive oxygen species on stress pathways and inflammasome activation. Furthermore, the excess iron may impair the host's ability to combat infection by its innate iron-withholding pathways. This symposium paper summarizes the background for the "iron hypothesis" as it relates to transfusion of red blood cells after prolonged refrigerated storage. It also includes a summary of the data from recent murine and human studies, and concludes with a discussion of several unresolved questions arising from these published studies.

Coagulopathy and shock on admission is associated with mortality for children with traumatic injuries at combat support hospitals

OBJECTIVE

In adults, early traumatic coagulopathy and shock are both common and independently associated with mortality. There are little data regarding both the incidence and association of early coagulopathy and shock on outcomes in pediatric patients with traumatic injuries. Our objective was to determine whether coagulopathy and shock on admission are independently associated with mortality in children with traumatic injuries.

METHODS

A retrospective review of the Joint Theater Trauma Registry from U.S. combat support hospitals in Iraq and Afghanistan from 2002 to 2009 was performed. Coagulopathy was defined as an international normalized ratio of ≥1.5 and shock as a base deficit of ≥6. Laboratory values were measured on admission. Primary outcome was inhospital mortality. Univariate analyses were performed on all admission variables followed by reverse stepwise multivariate logistic regression to determine independent associations.

SETTING

Combat support hospitals in Iraq and Afghanistan.

PATIENTS

Patients <18 yrs of age with Injury Severity Score, international normalized ratio, base deficit, and inhospital mortality were included. Of 1998 in the cohort, 744 (37%) had a complete set of data for analysis.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

The incidence of early coagulopathy and shock were 27% and 38.3% and associated with mortality of 22% and 16.8%, respectively. After multivariate logistic regression, early coagulopathy had an odds ratio of 2.2 (95% confidence interval 1.1-4.5) and early shock had an odds ratio of 3.0 (95% confidence interval 1.2-7.5) for mortality. Patients with coagulopathy and shock had an odds ratio of 3.8 (95% confidence interval 2.0-7.4) for mortality.

CONCLUSIONS

In children with traumatic injuries treated at combat support hospitals, coagulopathy and shock on admission are common and independently associated with a high incidence of inhospital mortality. Future studies are needed to determine whether more rapid and accurate methods of measuring coagulopathy and shock as well as if early goal-directed treatment of these states can improve outcomes in children.

The age of red blood cells is associated with bacterial infections in critically ill trauma patients

BACKGROUND

Blood transfusion increases the risk of nosocomial infection in trauma patients. Specific patient- and transfusion-related risk factors are largely unknown. In this study, risk factors for developing a bacterial infection after transfusion of red blood cells (RBC) or platelets were determined in a cohort of transfused critically ill trauma patients.

MATERIAL AND METHODS

A retrospective study was conducted in a mixed medical-surgical Intensive Care Unit (ICU) of a level-1 university trauma centre, in trauma patients who received a RBC or platelet transfusion. Patients who developed a bacterial infection after transfusion were compared to transfused controls who did not develop such an infection. Multivariable logistic regression was used to determine risk factors for infection.

RESULTS

Of the 7,118 patients admitted to the ICU during the study period, 196 trauma patients met the inclusion criteria. An infection developed in 56 patients (29%). Infection occurred irrespective of the administration of antibiotics as part of selective digestive tract decontamination, surgery status or Injury Severity Score. Transfusion of RBC stored for more than 14 days was associated with infection in trauma patients (odds ratio 1.038, [95% CI: 1.01-1.07], p=0.036). Neither the amount of RBC nor that of platelets was associated with onset of infection.

CONCLUSIONS

Transfusion of RBC stored for more then 14 days is a risk factor for onset of bacterial infection after trauma, irrespective of the use of prophylactic antibiotics. Transfusion of platelets was not a risk factor. These results may contribute to designing prospective studies on transfusion of fresh RBC only in trauma patients.

Immunoregulatory effects of stored red blood cells

Some clinical studies have identified potential adverse patient outcomes associated with RBC storage length. This may in part be due to the release of potentially hazardous bioactive products that accumulate during storage and are delivered at high concentrations during transfusion. In this situation, a proinflammatory tissue microenvironment may be established that can alter immunoregulatory mechanisms. This review highlights some of the potential immunomodulatory effects of stored RBCs that may be responsible for adverse transfusion reactions.