Does red blood cell storage affect clinical outcome? When in doubt, do the experiment

Red Blood Cell Deformability, Vasoactive Mediators, and Adhesion

Healthy red blood cells (RBCs) deform readily in response to shear stress in the circulation, facilitating their efficient passage through capillaries. RBCs also export vasoactive mediators in response to deformation and other physiological and pathological stimuli. Deoxygenation of RBC hemoglobin leads to the export of vasodilator and antiadhesive S-nitrosothiols (SNOs) and adenosine triphosphate (ATP) in parallel with oxygen transport in the respiratory cycle. Together, these mediated responses to shear stress and oxygen offloading promote the efficient flow of blood cells and in turn optimize oxygen delivery. In diseases including sickle cell anemia and conditions including conventional blood banking, these adaptive functions may be compromised as a result, for example, of limited RBC deformability, impaired mediator formation, or dysfunctional mediator export. Ongoing work, including single cell approaches, is examining relevant mechanisms and remedies in health and disease.

Transfusion of red blood cells stored for shorter versus longer duration for all conditions

BACKGROUND

Red blood cell (RBC) transfusion is a common treatment for anaemia in many conditions. The safety and efficacy of transfusing RBC units that have been stored for different durations before a transfusion is a current concern. The duration of storage for a RBC unit can be up to 42 days. If evidence from randomised controlled trials (RCT) were to indicate that clinical outcomes are affected by storage duration, the implications for inventory management and clinical practice would be significant.

OBJECTIVES

To assess the effects of using red blood cells (RBCs) stored for a shorter versus a longer duration, or versus RBCs stored for standard practice duration, in people requiring a RBC transfusion.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, PubMed (for epublications), LILACS, Transfusion Evidence Library, Web of Science CPCI-S and four international clinical trial registries on 20 November 2017.

SELECTION CRITERIA

We included RCTs that compared transfusion of RBCs of shorter versus longer storage duration, or versus standard practice storage duration.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods.

MAIN RESULTS

We included 22 trials (42,835 participants) in this review.The GRADE quality of evidence ranged from very low to moderate for our primary outcome of in-hospital and short-term mortality reported at different time points.Transfusion of RBCs of shorter versus longer storage duration Eleven trials (2249 participants) compared transfusion of RBCs of shorter versus longer storage duration. Two trials enrolled low birth weight neonates, two enrolled children with severe anaemia secondary to malaria or sickle cell disease, and eight enrolled adults across a range of clinical settings (intensive care, cardiac surgery, major elective surgery, hospitalised in-patients, haematology outpatients). We judged only two trials to be at low risk of bias across all domains; most trials had an unclear risk for multiple domains.Transfusion of RBCs of shorter versus longer storage duration probably leads to little or no difference in mortality at seven-day follow-up (risk ratio (RR) 1.42, 95% confidence interval (CI) 0.66 to 3.06; 1 trial, 3098 participants; moderate quality evidence) or 30-day follow-up (RR 0.85, 95%CI 0.50 to 1.45; 2 trials, 1121 participants; moderate quality evidence) in adults undergoing major elective cardiac or non-cardiac surgery.For neonates, no studies reported on the primary outcome of in-hospital or short-term mortality. At 40 weeks gestational age, the effect of RBCs of shorter versus longer storage duration on the risk of death was uncertain, as the quality of evidence is very low (RR 0.90, 95% CI 0.41 to 1.85; 1 trial, 52 participants).The effect of RBCs of shorter versus longer storage duration on the risk of death in children with severe anaemia was also uncertain within 24 hours of transfusion (RR 1.50, 95% CI 0.43 to 5.25; 2 trials, 364 participants; very low quality evidence), or at 30-day follow-up (RR 1.40, 95% CI 0.45 to 4.31; 1 trial, 290 participants; low quality evidence).Only one trial, in children with severe anaemia (290 participants), reported adverse transfusion reactions. Only one child in each arm experienced an adverse reaction within 24 hours of transfusion.Transfusion of RBCs of shorter versus standard practice storage duration Eleven trials (40,588 participants) compared transfusion of RBCs of shorter versus standard practice storage duration. Three trials enrolled critically ill term neonates; two of these enrolled very low birth weight neonates. There were no trials in children. Eight trials enrolled critically ill and non-critically ill adults, with most being hospitalised. We judged four trials to be at low risk of bias across all domains with the others having an unclear risk of bias across multiple domains.Transfusion of RBCs of shorter versus standard practice storage duration probably leads to little or no difference in adult in-hospital mortality (RR 1.05, 95% CI 0.97 to 1.14; 4 trials, 25,704 participants; moderate quality evidence), ICU mortality (RR 1.06, 95% CI 0.98 to 1.15; 3 trials, 13,066 participants; moderate quality evidence), or 30-day mortality (RR 1.04, 95% CI 0.96 to 1.13; 4 trials, 7510 participants;moderate quality evidence).Two of the three trials that enrolled neonates reported that there were no adverse transfusion reactions. One trial reported an isolated case of cytomegalovirus infection in participants assigned to the standard practice storage duration group. Two trials in critically ill adults reported data on transfusion reactions: one observed no difference in acute transfusion reactions between arms (RR 0.67, 95% CI 0.19 to 2.36, 2413 participants), but the other observed more febrile nonhaemolytic reactions in the shorter storage duration arm (RR 1.48, 95% CI 1.13 to 1.95, 4919 participants).Trial sequential analysis showed that we may now have sufficient evidence to reject a 5% relative risk increase or decrease of death within 30 days when transfusing RBCs of shorter versus longer storage duration across all patient groups.

AUTHORS' CONCLUSIONS

The effect of storage duration on clinically important outcomes has now been investigated in large, high quality RCTs, predominantly in adults. There appears to be no evidence of an effect on mortality that is related to length of storage of transfused RBCs. However, the quality of evidence in neonates and children is low. The current practice in blood banks of using the oldest available RBCs can be continued safely. Additional RCTs are not required, but research using alternative study designs, should focus on particular subgroups (e.g. those requiring multiple RBC units) and on factors affecting RBC quality.

Fresh versus old red cell transfusions: what have the recent clinical trials found?

PURPOSE OF REVIEW

Red blood cell transfusion is a common treatment for anaemia worldwide, but concerns continue to be raised about adverse effects of cellular blood components, which are biological products. One hypothesis for the adverse effects associated with blood transfusion is the harmful effects of storage on red cells that have been demonstrated in laboratory and animal studies. Over the past few years, a number of more significant randomized controlled trials comparing 'fresh' versus 'older' blood have been published in an attempt to address the clinical consequences of storage age, with two further large trials ongoing.

RECENT FINDINGS

These recent trials enrolled approximately 4000 participants across a variety of populations - cardiac surgical, critically ill, paediatric and acute hospitalized in-patients. All trials achieved statistically significant separation of red cell storage duration between both groups. The results of all these trials have found no clinical benefit to using fresher red cells when compared with older or standard-issue red cells. However, certain subgroups of patients either receiving red cells stored at more extreme ages of storage or those with additional risks for impaired microcirculations (critically ill elderly, severe sepsis and major haemorrhage) were either underrepresented or not included in these trials.

SUMMARY

At present, on the basis of recent trials, there is no indication for blood transfusion services to implement preferential utilization of fresher red cell units.

Whole blood for hemostatic resuscitation of major bleeding

Recent combat experience reignited interest in transfusing whole blood (WB) for patients with life-threatening bleeding. US Army data indicate that WB transfusion is associated with improved or comparable survival compared to resuscitation with blood components. These data complement randomized controlled trials that indicate that platelet (PLT)-containing blood products stored at 4°C have superior hemostatic function, based on reduced bleeding and improved functional measures of hemostasis, compared to PLT-containing blood products at 22°C. WB is rarely available in civilian hospitals and as a result is rarely transfused for patients with hemorrhagic shock. Recent developments suggest that impediments to WB availability can be overcome, specifically the misconceptions that WB must be ABO specific, that WB cannot be leukoreduced and maintain PLTs, and finally that cold storage causes loss of PLT function. Data indicate that the use of low anti-A and anti-B titer group O WB is safe as a universal donor, WB can be leukoreduced with PLT-sparing filters, and WB stored at 4°C retains PLT function during 15 days of storage. The understanding that these perceived barriers are not insurmountable will improve the availability of WB and facilitate its use. In addition, there are logistic and economic advantages of WB-based resuscitation compared to component therapy for hemorrhagic shock. The use of low-titer group O WB stored for up to 15 days at 4°C merits further study to compare its efficacy and safety with current resuscitation approaches for all patients with life-threatening bleeding.

A survey of US and Canadian hospitals' paediatric massive transfusion protocol policies

BACKGROUND

Trauma is the leading cause of death in children >1 year of age, with haemorrhage as the most common cause of medically preventable deaths. While massive transfusion protocols (MTPs) have been investigated and used in adults to reduce death from haemorrhage, there are a paucity of published data on MTP practices and outcomes in children. This study aimed to survey current MTP policies and the frequency of activation at paediatric care centres.

STUDY DESIGN AND METHODS

We conducted a survey of MTPs at hospitals in the United States and Canada, including children's general hospitals, children's specialty hospitals and children's units in general hospitals. We collected information on how the MTP is activated, what therapeutics are given, frequency of its use, and how it is audited for compliance.

RESULTS

Forty-six survey responses were analysed. Physician discretion was the most common activation criteria (89%). A majority of sites (78%) targeted a 'high' (≥1 : 2) ratio of plasma to red blood cells (RBC). Fifteen percent of sites use antifibrinolytics in their MTPs. Eighty nine percent of sites have type-O RBC units and 48% of sites had thawed plasma units stored in an immediately available location.

CONCLUSION

There is a wide variation in MTPs among paediatric hospitals with regard to both activation criteria and products administered. This underscores the need for future prospective studies to determine the most effective resuscitation methods for paediatric populations to improve outcomes and therapeutic safety for massive bleeding.

Transfusion of fresher vs older red blood cells in hospitalized patients: a systematic review and meta-analysis

The impact of transfusing fresher vs older red blood cells (RBCs) on patient-important outcomes remains controversial. Two recently published large trials have provided new evidence. We summarized results of randomized trials evaluating the impact of the age of transfused RBCs. We searched MEDLINE, EMBASE, CINAHL, the Cochrane Database for Systematic Reviews, and Cochrane CENTRAL for randomized controlled trials enrolling patients who were transfused fresher vs older RBCs and reported outcomes of death, adverse events, and infection. Independently and in duplicate, reviewers determined eligibility, risk of bias, and abstracted data. We conducted random effects meta-analyses and rated certainty (quality or confidence) of evidence using the GRADE approach. Of 12 trials that enrolled 5229 participants, 6 compared fresher RBCs with older RBCs and 6 compared fresher RBCs with current standard practice. There was little or no impact of fresher vs older RBCs on mortality (relative risk [RR], 1.04; 95% confidence interval [CI], 0.94-1.14; P = .45; I2 = 0%, moderate certainty evidence) or on adverse events (RR, 1.02; 95% CI, 0.91-1.14; P = .74; I2 = 0%, low certainty evidence). Fresher RBCs appeared to increase the risk of nosocomial infection (RR, 1.09; 95% CI, 1.00-1.18; P = .04; I2 = 0%, risk difference 4.3%, low certainty evidence). Current evidence provides moderate certainty that use of fresher RBCs does not influence mortality, and low certainty that it does not influence adverse events but could possibly increase infection rates. The existing evidence provides no support for changing practices toward fresher RBC transfusion.

Transfusion of fresher versus older red blood cells for all conditions

BACKGROUND

Red blood cell transfusion is a common treatment for anaemia in many clinical conditions. One current concern is uncertainty as to the clinical consequences (notably efficacy and safety) of transfusing red blood cell units that have been stored for different durations of time before a transfusion. If evidence from randomised controlled trials were to indicate that clinical outcomes are affected by storage age, the implications for inventory management and clinical practice would be significant.

OBJECTIVES

To assess the effects of using fresher versus older red blood cells in people requiring a red blood cell transfusion.

SEARCH METHODS

We ran the search on 29th September 2014. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OvidSP), Embase (OvidSP), CINAHL (EBSCO), PubMed (for e-publications), three other databases and trial registers.

SELECTION CRITERIA

We included randomised controlled trials comparing fresher red blood cell transfusion versus active transfusion of older red blood cells, and comparing fresher red blood cell transfusion versus current standard practice. All definitions of 'fresher' and 'older'/'standard practice' red blood cells were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted from the trial report data on adverse red blood cell transfusion reactions, when reported.

MAIN RESULTS

We included 16 trials (1864 participants) in the review. Eight trials (279 participants) compared transfusion of fresher red blood cells versus transfusion of older stored red blood cells ('fresher' vs 'older'). Eight trials (1585 participants) compared the transfusion of fresher red blood cells versus current standard practice ('fresher' vs 'standard practice'). Five trials enrolled neonates, one trial enrolled children and 12 trials enrolled adults. Overall sample sizes were small: only two trials randomly assigned more than 100 participants.We performed no meta-analyses for a variety of reasons: no uniform definition of 'fresher' or 'older' red blood cell storage; overlap in the distribution of the age of red blood cells; and heterogeneity in measurements and reporting of outcomes of interest to this review. We tabulated and reported results by individual trial. Overall risk of bias was low or unclear, with four incidences of high risk of bias: in allocation concealment (three trials) and in incomplete outcome data (one trial).No trial measured all of the outcomes of interest in this review. Four trials comparing 'fresher' with 'older' red blood cells reported the primary outcome: mortality within seven days (one study; 74 participants) and at 30 days (three trials; 62 participants). Six trials comparing 'fresher' with 'standard practice' red blood cells reported the primary outcome: mortality within seven days (three studies; 159 participants) and at 30 days (three trials; 1018 participants). All 10 trials reported no clear differences in mortality at either time point between intervention arms.Three trials comparing 'fresher' with 'standard practice' red blood cells reported red blood cell transfusion-associated adverse events. No adverse reactions were reported in two trials, and one incidence of cytomegalovirus (CMV) infection was described in the 'standard practice' arm in one trial.Overall the trials reported no clear difference between either of the intervention comparisons in long-term mortality (three trials; 478 participants); clinically accepted measures of multiple organ dysfunction (two trials: 399 participants); incidence of in-hospital infection (two trials; 429 participants); duration of mechanical ventilation (three trials: 95 participants); and number of participants requiring respiratory organ support (five trials; 528 participants) or renal support (one trial; 57 participants). The outcome 'physiological markers of oxygen consumption or alterations in microcirculation' was reported by 11 studies, but the measures used were highly varied, and no formal statistical analysis was undertaken.

AUTHORS' CONCLUSIONS

Several factors precluded firm conclusions about the clinical outcomes of transfusing red blood cell units that have been stored for different periods of time before transfusion, including differences in clinical population and setting, diversity in the interventions used, methodological limitations and differences in how outcomes were measured and reported.No clear differences in the primary outcome - death - were noted between 'fresher' and 'older' or 'standard practice' red blood cells in trials that reported this outcome. Findings of a large number of ongoing trials will be incorporated into this review when they are published.Updates of this review will explore the degree of overlap in trials between 'fresher', 'older' and 'standard practice' storage ages of red blood cells and will consider whether the size of any observed effects is dependent on recipient factors such as clinical background, patient age or clinical presentation.

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.

Association between red blood cell storage duration and clinical outcome in patients undergoing off-pump coronary artery bypass surgery: a retrospective study

Background

Prolonged storage of red blood cells (RBCs) leads to fundamental changes in both the RBCs and the storage media. We retrospectively evaluated the relationship between the RBC age and in-hospital and long-term postoperative outcomes in patients undergoing off-pump coronary artery bypass.

Methods

The electronic medical records of 1,072 OPCAB patients were reviewed and information on the transfused RBCs and clinical data were collected. The effects of RBCs age (mean age, oldest age of transfused RBCs, any RBCs older than 14 days) on various in-hospital postoperative complications and long-term major adverse cardiovascular and cerebral events over a mean follow-up of 31 months were investigated. Correlations between RBCs age and duration of intubation, intensive care unit, or hospital stay, and base excess at the first postoperative morning were also analyzed.

Results

After adjusting for confounders, there was no relationship between the RBCs age and in-hospital and long-term clinical outcomes except for postoperative wound complications. A significant linear trend was observed between the oldest age quartiles of transfused RBCs and the postoperative wound complications (quartile 1 vs. 2, 3 and 4: OR, 8.92, 12.01 and 13.79, respectively; P for trend = 0.009). The oldest transfused RBCs showed significant relationships with a first postoperative day negative base excess (P = 0.021), postoperative wound complications (P = 0.001), and length of hospital stay (P = 0.008).

Conclusions

In patients undergoing off-pump coronary artery bypass, the oldest age of transfused RBCs were associated with a postoperative negative base excess, increased wound complications, and a longer hospital stay, but not with the other in-hospital or long-term outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2253-14-95) contains supplementary material, which is available to authorized users.

Transfusion related morbidity in premature babies: Possible mechanisms and implications for practice

Many premature babies, especially those with a low birth weight are given multiple transfusions during their first few weeks of life. The major serious complications of prematurity include bronchopulmonary dysplasia, with lesser incidences of retinopathy of prematurity, intraventricular haemorrhage, and necrotising enterocolitis. Many studies have shown correlations between the receipt of blood transfusions and the development of these conditions, but little is known of the underlying pathophysiology of this relationship. Recent studies are beginning to provide some answers. This review examines recent findings with regard to the influence of preparation and storage of paediatric packed red blood cell units on heme, iron, and oxidative status of the units and relates these to the ability of the premature baby to deal with these changes following the receipt of blood transfusions. Paediatric packed red blood cell units are a potential source of heme, redox active iron and free radicals, and this increases with storage age. Haemolysis of transfused red blood cells may add further iron and cell free haemoglobin to the recipient baby. Premature babies, particularly those with low birth weight and gestational age appear to have little reserve to cope with any additional iron, heme and/or oxidative load. The consequences of these events are discussed with regard to their contribution to the major complications of prematurity and a novel hypothesis regarding transfusion-related morbidity in premature babies is presented. The review concludes with a discussion of potential means of limiting transfusion related iron/heme and oxidative load through the preparation and storage of packed red blood cell units and through modifications in clinical practice.

Storage time of red blood cells and mortality of transfusion recipients

Storage of red cells and the associated storage lesion have been suggested to contribute to adverse clinical outcomes. The aim of this study was to investigate whether increasing storage time of red cells is associated with mortality of recipients. From all patients who received red cell transfusions between January 2005 and May 2009, in the Leiden University Medical Center, we selected those who received only-young or only-old red cells, defined as below or above the median storage time. Mortality was compared in a Cox regression model. Subsequently, similar comparisons were made between subgroups with increasing contrast between old and young red cells. Among adult patients, after correction for potential confounders, the hazard ratio of death within 1 year after receiving red cells stored for more than 17 days compared with 17 days or less was 0.98 (95% confidence interval, 0.83-1.2). With increasing contrast, the hazard ratio decreased to 0.56 (95% confidence interval, 0.32-0.97) for red cells stored for more than 24 days compared with less than 10 days. In contrast to what has previously been suggested, we find an almost 2-fold increase in mortality rate after the transfusion of fresh red cells compared with old red cells. Results dependent on analyses chosen and previous studies may not have used optimal analyses. The tendency to demand ever-fresher blood could actually be detrimental for at least some patient groups.

Will clinical studies elucidate the connection between the length of storage of transfused red blood cells and clinical outcomes? An analysis based on the simulation of randomized controlled trials

BACKGROUND

The temporal pattern of the biologic mechanism linking red blood cell (RBC) storage duration with clinical outcomes is yet unknown. This study investigates how such a temporal pattern can affect the power of randomized controlled trials (RCT) to detect a relevant clinical outcome mediated by the transfusion of stored RBCs.

STUDY DESIGN AND METHODS

This study was a computer simulation of four RCTs, each using a specific categorization of the RBC storage time. The trial's endpoint was evaluated assuming five hypothetical temporal patterns for the biologic mechanism linking RBC storage duration with clinical outcomes.

RESULTS

Power of RCTs to unveil a significant association between RBC storage duration and clinical outcomes was critically dependent on a complex interaction among three factors: 1) the way the RBC storage time is categorized in the trial design, 2) the temporal pattern assumed for the RBC storage lesion, and 3) the age distribution of RBCs in the inventory from which they are picked up for transfusion. For most combinations of these factors, the power of RCTs to detect a significant treatment effect was below 80%. All the four simulated RCTs had a very low power to disclose a harmful clinical effect confined to last week of the maximum 42-day shelf life of stored RBCs.

CONCLUSIONS

Ongoing RCTs may lack enough power to settle the issue of whether or not the transfusion of stored blood has a negative clinical impact. A precautionary reduction of the maximum storage time to 35 days is advisable.

A novel allocation strategy for blood transfusions: investigating the tradeoff between the age and availability of transfused blood

BACKGROUND

Recent studies show that transfusing older blood may lead to increased mortality. This raises the issue of whether transfusing fresher blood can be achieved without jeopardizing blood availability.

STUDY DESIGN AND METHODS

We propose a simple family of policies that is defined by a single threshold: rather than transfusing the oldest available blood that is younger than 42 days, we transfuse the oldest blood that is younger than the threshold, and if there is no blood younger than the threshold then we transfuse the youngest blood that is older than the threshold. To assess this policy, we build a simulation model using data from Stanford University Medical Center. We focus on the tradeoff between the mean age of transfused blood and the fraction of transfused blood that is imported.

RESULTS

For hospitals in which the local supply is greater than demand, our policy with a threshold of 14 days leads to a decrease of 10 to 20 days in the mean age of transfused blood while increasing the fraction of imported blood to less than 0.005 (i.e., 0.5%). If the health benefits from transfusing fresher blood can be confirmed by randomized clinical trials, then conservative assumptions suggest that this policy could reduce the annual number of transfused patients who die within 1 year by 20,000.

CONCLUSION

The proposed allocation policy with a threshold of 14 days could allow many US hospitals to significantly reduce the age of transfused blood, thereby possibly reducing morbidity and mortality, while having a negligible impact on supply chain operations.

Development of the S-303 Pathogen Inactivation Technology for Red Blood Cell Concentrates

Pathogen inactivation systems are in use in many European countries as routine procedures. However, a pathogen inactivation system for erythrocytes is currently not available. Although significant improvements have been made to decrease the incidence of transfusion-transmitted infections, risks remain for infectious disease agents specific to red blood cell concentrates, such as parasitic infections resulting in babesiosis and malaria. The pathogen inactivation system for erythrocytes utilizes S-303 and glutathione for the treatment of red blood cell concentrates. Preclinical studies to assess the pathogen inactivation efficacy and toxicology as well as preliminary clinical studies have been completed. Preclinical studies have shown log reduction for leukocytes, several viruses and bacteria in excess of 4 to 6 logs. Preclinical toxicology studies were conducted to enable the initiation of two phase III clinical studies in the USA for support of acute and chronic anemia. A second-generation system was developed after observation of an unexpected immune response in two chronic anemia patients. Preclinical pathogen inactivation studies, serological evaluations and a clinical study to evaluate survival of S-303-treated erythrocytes have been completed to support advanced development of the S-303 pathogen inactivation system. A functional system for the inactivation of red blood cell concentrates has been completed and is reaching clinical application.

Age of blood as a limitation for transfusion: potential impact on blood inventory and availability

BACKGROUND

Evolving concerns about storage lesions for red blood cells (RBCs) have led to ongoing trials evaluating the benefits of transfusing fresher blood to acutely ill patients.

STUDY DESIGN AND METHODS

We evaluated several RBC maximum shelf lives (MSLs) and their impact on RBC availability and outdate rate. First, we determined the mean age of the RBC units in our inventory by analyzing the data set of 18,987 nonirradiated RBC units transfused at our institution from April 2008 to March 2009. Second, we determined the feasibility of issuing RBC units of a designated age to patients using the same data set. We defined six scenarios where RBC units have different MSLs: Scenarios 1, 2, 3, 4, and 5 used a MSL of 7, 14, 21, 28, and 35 days, respectively. Scenario 6 used a combination of different MSLs depending on the category of patients.

RESULTS

RBC units spent on average 8.6 days on the shelf with a mean age of 10.2 days at delivery and 18.8 days at issue for transfusion. Using the original 18,987 data points, we observed a shortfall in the availability of RBC units, decreased by 51, 20, 10, 4, 1, and 0% and an increase in the outdate rate to 3.2, 2.2, 1.0, 0.6, 0.4, and 4.5% for Scenarios 1, 2, 3, 4, 5, and 6, respectively, compared to baseline.

CONCLUSION

Changing the MSL for RBC units would require novel approaches to RBC inventory management to meet hospital demands with acceptable outdate rates.

Clinical studies of the effect of blood storage on patient outcomes

It is indisputable that there are numerous biochemical, structural, inflammatory, and physiologic changes in stored red cells, sometimes referred to collectively as the "red cell storage lesion". It remains controversial however whether any of these changes have clinical relevance and actually impact the clinical outcomes in transfused patients. More than 25 published clinical studies have evaluated the effects of red blood cell storage on patient outcomes. The majority of studies are non-randomized observational studies with methodologic limitations described in this review. These studies do however provide equipoise to support the ethical conduct of the large, definitive randomized clinical trials which are now underway.

Addressing the question of the effect of RBC storage on clinical outcomes: the Red Cell Storage Duration Study (RECESS) (Section 7)

The question of whether storage of red blood cells (RBCs) alters their capacity to deliver oxygen and affects patient outcomes remains in a state of clinical equipoise. Studies of the changes which occur while RBCs are stored have led to several physiologically plausible hypotheses that these changes impair RBC function when the units are transfused. Although there is some evidence of this effect in vivo from animal model experiments, the results of several largely retrospective patient studies have not been consistent. Some studies have shown an association between worse clinical outcomes and transfusion of RBC which have been stored for longer periods of time, while others have found no effect. Three multicenter, randomized, controlled trials have been developed to address this important, but currently unanswered, question. Two clinical trials, one in low birth weight neonates and the other in intensive care unit patients, are enrolling subjects in Canada (the Age of Red Blood Cells in Premature Infants; the Age of Blood Study). The third trial, which is being developed in the United States, is the Red Cell Storage Duration Study (RECESS). This is a multicenter, randomized, controlled trial in which patients undergoing complex cardiac surgical procedures who are likely to require RBC transfusion will be randomized to receive RBC units stored for either 10 or fewer days or 21 or more days. Randomization will only occur if the blood bank has enough units of RBC of both storage times to meet the crossmatch request; hence, subjects randomized to the 21 day arm will receive RBC of the same storage time as they would have following standard inventory practice of "oldest units out first". The primary outcome is the change in the Multiple Organ Dysfunction Score (MODS), a composite measure of multiorgan dysfunction, by day 7. Secondary outcomes include the change in the MODS by day 28, all-cause mortality, and several composite and single measures of specific organ system function. The estimated total sample size required will be 1434 evaluable subjects (717 per arm).

Red cell changes during storage

Red blood cells can be stored in liquid suspension in approved additive solutions for periods up to 6 weeks with 0.4% hemolysis, 84% 24-h in vivo recovery, and normal subsequent survival of the cells that persist in the circulation for at least 24h. However, while they are stored, the red cells undergo changes including the loss of adenosine triphosphate, diphosphoglycerate, and potassium, oxidative injury to proteins, lipids, and carbohydrates, loss of shape and membrane, increased adhesiveness, decreased flexibility, reduced capillary flow, and decreased oxygen delivery. Deaths have been reported related to the high potassium and lysophospholipids, but are rare.

Blood still kills: six strategies to further reduce allogeneic blood transfusion-related mortality

After reviewing the relative frequency of the causes of allogeneic blood transfusion-related mortality in the United States today, we present 6 possible strategies for further reducing such transfusion-related mortality. These are (1) avoidance of unnecessary transfusions through the use of evidence-based transfusion guidelines, to reduce potentially fatal (infectious as well as noninfectious) transfusion complications; (2) reduction in the risk of transfusion-related acute lung injury in recipients of platelet transfusions through the use of single-donor platelets collected from male donors, or female donors without a history of pregnancy or who have been shown not to have white blood cell (WBC) antibodies; (3) prevention of hemolytic transfusion reactions through the augmentation of patient identification procedures by the addition of information technologies, as well as through the prevention of additional red blood cell alloantibody formation in patients who are likely to need multiple transfusions in the future; (4) avoidance of pooled blood products (such as pooled whole blood-derived platelets) to reduce the risk of transmission of emerging transfusion-transmitted infections (TTIs) and the residual risk from known TTIs (especially transfusion-associated sepsis [TAS]); (5) WBC reduction of cellular blood components administered in cardiac surgery to prevent the poorly understood increased mortality seen in cardiac surgery patients in association with the receipt of non-WBC-reduced (compared with WBC-reduced) transfusion; and (6) pathogen reduction of platelet and plasma components to prevent the transfusion transmission of most emerging, potentially fatal TTIs and the residual risk of known TTIs (especially TAS).

Meta-analysis of clinical studies of the purported deleterious effects of "old" (versus "fresh") red blood cells: are we at equipoise?

BACKGROUND

A meta-analysis examined whether the available data support an adequate suspicion that transfusion of old red blood cells (RBCs) is associated with increased mortality, organ failure, infection, prolonged mechanical ventilation, and prolonged stay in the hospital or the intensive care unit. Such suspicion is required for intentionally exposing patients enrolled in randomized controlled trials (RCTs) to the known or probable--but rare--risks of old RBCs, to document (and prevent) purported common adverse effects of old RBCs.

STUDY DESIGN AND METHODS

Observational studies presenting adjusted results were eligible for analysis if the adequacy of the adjustment for confounding factors could be assessed. Three RCTs and 24 observational studies were retrieved. Medically and statistically homogeneous studies were integrated by fixed-effects methods. Otherwise homogeneous studies conducted in different clinical settings were integrated by random-effects methods.

RESULTS

Based on "as-treated" analysis, transfusion of old RBCs was associated with a significant reduction in mortality (summary odds ratio, 0.38; 95% confidence interval, 0.14-0.99; p < 0.05) across two small RCTs. Integration of adjusted findings on the same outcome, from observational studies conducted in the same setting, produced summary results that were either negative (in six analyses) or impossible to evaluate owing to uncontrolled confounding by the number of transfused RBCs (in two analyses).

CONCLUSION

The available data do not support an adequate suspicion that old RBCs may be associated with common adverse morbidity and/or mortality outcomes, so as to justify exposing experimental subjects to the other known or probable--but rare--risks of old RBCs.

Red cell storage

Blood component storage allows the donor and recipient to be separated in time and space. This separation converts transfusion from a desperate clinical act into a planned, orderly healthcare logistic activity with concomitant increases in both blood product availability and safety. However, storage has the potential to reduce the efficacy of transfused blood components by reducing their flow, functional capacity, and survival. Storage time also allows the accumulation of leaked potassium from red cells and the growth of contaminating bacteria. Many different aspects of the red cell storage lesion have been described, including changes in metabolism, shape, and rheology changes, loss of membrane carbohydrates, lipids and proteins, and alterations in secretion, oxygen delivery, and adhesion. What has been harder to show is that these known changes have significant clinical effects. Therefore, regulatory decisions about product storage have been conservative, and largely based on historic patterns of use. The increasing power of proteomics and metabolomics offers the potential of deeper understanding of blood function and storage and of better clinical products in the future.