Platelet-inspired synthetic nanoparticles improve hemostasis and hemodynamics in a rabbit model of abdominal hemorrhage.

BACKGROUND: Early platelet transfusion is associated with reduced mortality in traumatic hemorrhage. However, platelet usage is severely limited because of the challenges of donor availability, platelet portability, and storage. Here, we report on a bioinspired synthetic platelet (SP) nanoconstruct that utilizes liposome surface-decoration with peptides that mimic injury site-specific platelet adhesion to von Willebrand Factor and collagen, and fibrinogen-mediated platelet aggregation. Synthetic platelet has previously shown promising hemostatic outcomes in vitro and in vivo. Here, we evaluated hemostasis and hemodynamic effects of SP in a rabbit model of abdominal hemorrhage. METHODS: Twenty-three adult male New Zealand white rabbits (2.5-3.5 kg) were treated with either buffer, control particles (CPs), or SP. Under general anesthesia with invasive monitoring, rabbits underwent laparotomy with combined splenic and hepatic injury. Hemodynamics were monitored for 30 minutes and blood loss was quantified. Blood counts, aggregometry, catecholamine and platelet factor 4 (PF4) assays were performed at multiple timepoints. Analysis used analysis of variance and post hoc Tukey testing with α = 0.05. RESULTS: Rabbits in the SP (n = 7) group had significantly lower weight-normalized blood loss compared with both buffer (n = 8) and CP (n = 8) animals (21.1 vs. 33.2 vs. 40.4 g/kg, p < 0.001). Synthetic platelet-treated animals had higher systolic blood pressure area under curve compared with buffer- and CP-treated animals (1567 vs. 1281 vs. 1109 mm Hg*min, p = 0.006), although post hoc differences were only significant for the SP/CP comparison ( p = 0.005). Platelet counts, catecholamine levels, PF4, and aggregometry were similar between groups. CONCLUSION: Synthetic platelet treatment significantly reduced blood loss and improved hemodynamics in a rabbit abdominal hemorrhage model. Synthetic platelet has potential as an intravenous hemostatic platelet surrogate with donor-independent availability and scalable manufacture.

High Dose of Metformin Decreases Susceptibility to Occlusive Arterial Thrombosis in Diabetic Mice.

Introduction: Metformin is the most prescribed medication in Diabetes Mellitus(DM). Metformin has shown to decrease mean platelet volume, with promising antiplatelet effects. High doses of Metformin have also been associated with hypercoagulation. We hypothesize that Metformin will protect DM mice from occlusive arterial thrombus formation by altering platelet activation and mitochondrial bioenergetics. Methods: DM was developed by low dose of Streptozotocin, non-DM (healthy) mice are controls. Either vehicle or Metformin was administered twice daily via oral gavage for 7-days. Ferric chloride (FeCl3) arterial thrombosis and tail bleeding time were performed. Whole blood aggregometry, platelet activation/adhesion and mitochondrial bioenergetics were evaluated. Results: Metformin decreased susceptibility of DM mice to arterial thrombosis. Platelet bioenergetics show DM mice have increased platelet mitochondrial respiration, but no differences were observed with Metformin treatment. In non-DM (healthy) mice, Metformin modulated ADP-dependent increase in platelet adhesion. Non-DM (healthy) mice, Metformin shortens bleeding time with faster thrombotic occlusion. Metformin also increased platelet mitochondrial maximal respiration and spare respiratory capacity uniquely in non-DM (healthy) mice. Conclusion: Metformin regulates platelet bioenergetics and ADP-mediated platelet function in DM mice which attenuates susceptibility to arterial thrombosis. Future studies will evaluate clinically relevant doses of Metformin that regulates thrombotic function in diabetic platelets.

High Dose of Metformin Decreases Susceptibility to Occlusive Arterial Thrombosis in Diabetic Mice.

Introduction: Metformin is the most prescribed medication in Diabetes Mellitus(DM). Metformin has shown to decrease mean platelet volume, with promising antiplatelet effects. High doses of Metformin have also been associated with hypercoagulation. We hypothesize that Metformin will protect DM mice from occlusive arterial thrombus formation by altering platelet activation and mitochondrial bioenergetics. Methods: DM was developed by low dose of Streptozotocin, healthy (non-DM) mice are controls. Either vehicle or Metformin was administered twice daily via oral gavage for 7-days. Ferric chloride (FeCl3) arterial thrombosis and tail bleeding time were performed. Whole blood aggregometry, platelet activation/adhesion and mitochondrial bioenergetics were evaluated. Results: Metformin decreased susceptibility of DM mice to arterial thrombosis. Platelet bioenergetics show DM mice have increased platelet mitochondrial respiration, but no differences were observed with Metformin treatment. In healthy mice, Metformin modulated ADP-dependent increase in platelet adhesion. In healthy mice, Metformin shortens bleeding time with faster thrombotic occlusion. Metformin also increased platelet mitochondrial maximal respiration and spare respiratory capacity uniquely in healthy mice. Conclusion: Metformin regulates platelet bioenergetics and ADP-mediated platelet function in DM mice which attenuates susceptibility to arterial thrombosis. Future studies will evaluate clinically relevant doses of Metformin that regulates thrombotic function in diabetic platelets.

Hemostatic In Vitro Properties of Novel Plasma Supernatants Produced from Late-storage Low-titer Type O Whole Blood.

BACKGROUND: The use of low-titer group O whole blood is increasing. To reduce wastage, unused units can be converted to packed red blood cells. Supernatant is currently discarded post-conversion; however, it could be a valuable transfusable product. The aim of this study was to evaluate supernatant prepared from late-storage low-titer group O whole blood being converted to red blood cells, hypothesizing it will have higher hemostatic activity compared to fresh never-frozen liquid plasma. METHODS: Low-titer group O whole blood supernatant (n = 12) prepared on storage day 15 was tested on days 15, 21, and 26 and liquid plasma (n = 12) on 3, 15, 21, and 26. Same-day assays included cell counts, rotational thromboelastometry, and thrombin generation. Centrifuged plasma from units was banked for microparticle characterization, conventional coagulation, clot structure, hemoglobin, and additional thrombin generation assays. RESULTS: Low-titer group O whole blood supernatant contained more residual platelets and microparticles compared to liquid plasma. At day 15, low-titer group O whole blood supernatant elicited a faster intrinsic clotting time compared to liquid plasma (257 ± 41 vs. 299 ± 36 s, P = 0.044), and increased clot firmness (49 ± 9 vs. 28 ± 5 mm, P < 0.0001). Low-titer group O whole blood supernatant showed more significant thrombin generation compared to liquid plasma (day 15 endogenous thrombin potential 1,071 ± 315 vs. 285 ± 221 nM·min, P < 0.0001). Flow cytometry demonstrated low-titer group O whole blood supernatant contained significantly more phosphatidylserine and CD41+ microparticles. However, thrombin generation in isolated plasma suggested residual platelets in low-titer group O whole blood supernatant were a greater contributor than microparticles. Additionally, low-titer group O whole blood supernatant and liquid plasma showed no difference in clot structure, despite higher CD61+ microparticle presence. CONCLUSIONS: Plasma supernatant produced from late-storage low-titer group O whole blood shows comparable, if not enhanced, in vitro hemostatic efficacy to liquid plasma.

Comparison of platelet quality and function across apheresis collection platforms.

BACKGROUND: Platelet concentrates (PLT) can be manufactured using a combination of apheresis collection devices and suspension media (plasma or platelet additive solution (PAS)). It is unclear how platelet quality and hemostatic function differ across the current in-use manufacturing methods in the United States. The objective of this study was therefore to compare baseline function of PLT collected using different apheresis collection platforms and storage media. STUDY DESIGN AND METHODS: PLT were collected at two sites with identical protocols (N = 5 per site, N = 10 total per group) on the MCS® + 9000 (Haemonetics; "MCS"), the Trima Accel® 7 (Terumo; "Trima"), and the Amicus Cell Separator (Fresenius Kabi, "Amicus"). MCS PLT were collected into plasma while Trima and Amicus PLT were collected into plasma or PAS (Trima into Isoplate and Amicus into InterSol; yielding groups "TP", "TI" and "AP", "AI", respectively). PLT units were sampled 1 h after collection and assayed to compare cellular counts, biochemistry, and hemostatic function. RESULTS: Differences in biochemistry were most evident between plasma and PAS groups, as anticipated. MCS and TP had the highest clot strength as assessed by viscoelastometry. AI had the lowest thrombin generation capacity. Both TP and TI had the highest responses on platelet aggregometry. AI had the greatest number of microparticles. DISCUSSION: Platelet quality and function differ among collection platforms at baseline. MCS and Trima platelets overall appear to trend toward higher hemostatic function. Future investigations will assess how these differences change throughout storage, and if these in vitro measures are clinically relevant.

EFFECT OF IRRIGATION FLUID COMPOSITION ON HEMOSTASIS IN MOUSE BLEEDING MODELS.

ABSTRACT: Introduction: Intraoperative irrigation, usually with normal saline (NS), aids in bleeding identification and management. We investigated the effect of different irrigation fluids, with additives, on hemostasis using two bleeding models. Methods: C57BL/6 J mice were subjected to a tail bleed model or uncontrolled abdominal hemorrhage via liver laceration followed by abdominal cavity irrigation. We compared NS, lactated Ringer's (LR), and PlasmaLyte. We examined NS and LR at different temperatures. Normal saline or LR with calcium (Ca 2+ ) or tranexamic acid (TXA) was studied. Results: Compared with room temperature (RT), increasing the temperature of the irrigation fluid to 37°C and 42°C reduced tail vein bleeding times substantially in both NS and LR (all P < 0.001), with no significant differences between the two fluids. At RT, LR, but not PlasmaLyte, substantially reduced bleeding times in comparison to NS ( P < 0.0001). Liver injury blood loss was lower with LR ( P < 0.01). Normal saline supplemented with 2.7 mEq/L of Ca 2+ decreased bleeding time and blood loss volume ( P < 0.001 and P < 0.01, respectively) to similar levels as LR. Normal saline with 150 mg/mL of TXA markedly reduced bleeding time ( P < 0.0001), and NS with 62.5 mg/mL TXA decreased blood loss ( P < 0.01). Conclusion: Whereas Ca 2+ - and TXA-supplemented NS reduced bleeding, LR remained superior to all irrigation fluid compositions. As LR contains Ca 2+ , and Ca 2+ -supplemented NS mirrored LR in response, Ca 2+ presence in the irrigation fluid seems key to improving solution's hemostatic ability. Because warming the fluids normalized the choice of agents, the data also suggest that Ca 2+ -containing fluids such as LR may be more suitable for hemostasis when used at RT.

Recent Changes in Durable Left Ventricular Assist Device Bridging to Heart Transplantation.

This study evaluates the impact of the recent United Network for Organ Sharing (UNOS) allocation policy change on outcomes of patients bridged with durable left ventricular assist devices (LVADs) to orthotopic heart transplantation (OHT). Adults bridged to OHT with durable LVADs between 2010 and 2019 were included. Patients were stratified based on the temporal relationship of their OHT to the UNOS policy change on October 18, 2018. The primary outcome was early post-OHT survival. In total, 9,628 OHTs were bridged with durable LVADs, including 701 (7.3%) under the new policy. Of all OHTs performed during the study period, the proportion occurring following durable LVAD bridging decreased from 45% to 34% (p < 0.001). The more recent cohort was higher risk, including more extracorporeal membrane oxygenation bridging (2.6% vs. 0.3%, p < 0.001), more mechanical right ventricular support (9.7% vs. 1.4%, p < 0.001), greater pretransplant ICU admission (22.8% vs. 8.7%, p < 0.001) more need for total functional assistance (62.8% vs. 53.0%, p < 0.001), older donor age (33.3 vs. 31.7 years, p < 0.001), and longer ischemic times (3.38 vs. 3.13 hours, p < 0.001). Despite this, early post-OHT survival was comparable at 30 days (96.1% vs. 96.0%, p = 0.89), 90 days (93.7% vs. 94.0%, p = 0.76), and 6 months (91.0% vs. 93.0%, p = 0.96), findings that persisted after risk-adjustment. In this early analysis, OHT following bridging with durable LVADs is performed less frequently and in higher risk recipients under the new allocation policy. Despite this, short-term posttransplant outcomes appear to be unaffected in this patient cohort in the current era.

The emerging therapeutic potential of extracellular vesicles in trauma.

Traumatic injury is a major cause of morbidity and mortality worldwide, despite significant advances in treatments. Most deaths occur either very early, through massive head trauma/CNS injury or exsanguination (despite advances in transfusion medicine), or later after injury often through multiple organ failure and secondary infection. Extracellular vesicles (EVs) are known to increase in the circulation after trauma and have been used to limited extent as diagnostic and prognostic markers. More intriguingly, EVs are now being investigated as both causes of pathologies post trauma, such as trauma-induced coagulopathy, and as potential treatments. In this review, we highlight what is currently known about the role and effects of EVs in various aspects of trauma, as well as exploring current literature from investigators who have begun to use EVs therapeutically to alter the physiology and pathology of traumatic insults. The potential effectiveness of using EVs therapeutically in trauma is supported by a large number of experimental studies, but there is still some way to go before we understand the complex effects of EVs in what is already a complex disease process.

Pre-implant left ventricular dimension is not associated with worse outcomes after left ventricular assist device implantation.

BACKGROUND: Left ventricular dimension has the potential to impact clinical outcomes following implantation of left ventricular assist devices (LVAD). We investigated the effect of pre-implant left ventricular end-diastolic diameter (LVEDD) on outcomes following LVAD implantation. METHODS: Patients implanted with a continuous-flow LVAD between 2004 and 2018 at a single institution were included. The primary outcome was death while on LVAD support. Secondary outcomes included adverse event rates such as renal failure requiring dialysis, device thrombosis, and right ventricular failure. The LVEDD measurements were dichotomized using restricted cubic splines and threshold regression. Survival was determined using Kaplan-Meier estimates. Multivariable logistic regression was used to determine risk-adjusted mortality based on LVEDD. RESULTS: A total of 344 patients underwent implantation of a continuous flow LVAD during the study period. The optimal cut point for LVEDD was 65 mm, with 126 (36.6%) subjects in the <65 mm group and 165 (48.0%) in the >65 mm group. The LVEDD <65 mm group was older, had more females, higher incidence of diabetes, more pre-implant mechanical ventilation, and more admissions for acute myocardial infarctions (all, P<0.05). Importantly, post-implant adverse events were similar between the groups (all, P>0.05). Risk-adjusted survival at 1-year (OR 1.3, 95% CI: 0.6-2.5, P=0.53) was also comparable between the groups. Furthermore, incremental increases in LVEDD when modeled as a continuous variable did not impact overall mortality (OR 0.98, 95% CI: 0.9-1.0, P=0.09). CONCLUSIONS: Preoperative LVEDD was not associated with rates of major morbidities or mortality following LVAD implantation.

The effect of pathogen inactivation on cryoprecipitate: a functional and quantitative evaluation.

BACKGROUND: As a pooled donor blood product, cryoprecipitate (cryo) carries risks of pathogen transmission. Pathogen inactivation (PI) improves the safety of cryoprecipitate, but its effects on haemostatic properties remain unclear. This study investigated protein expression in samples of pathogen inactivated cryoprecipitate (PI-cryo) using non-targeted quantitative proteomics and in vitro haemostatic capacity of PI-cryo. MATERIALS AND METHODS: Whole blood (WB)- and apheresis (APH)-derived plasma was subject to PI with INTERCEPT® Blood System (Cerus Corporation, Concord, CA, USA) and cryo was prepared from treated plasma. Protein levels in PI-cryo and paired controls were quantified using liquid chromatography-tandem mass spectrometry. Functional haemostatic properties of PI-cryo were assessed using a microparticle (MP) prothrombinase assay, thrombin generation assay, and an in vitro coagulopathy model subjected to thromboelastometry. RESULTS: Over 300 proteins were quantified across paired PI-cryo and controls. PI did not alter the expression of coagulation factors, but levels of platelet-derived proteins and platelet-derived MPs were markedly lower in the WB PI-cryo group. Compared to controls, WB (but not APH) cryo samples demonstrated significantly lower MP prothrombinase activity, prolonged clotting time, and lower clot firmness on thromboelastometry after PI. However, PI did not affect overall thrombin generation variables in either group. DISCUSSION: Data from this study suggest that PI via INTERCEPT® Blood System does not significantly impact the coagulation factor content or function of cryo but reduces the higher MP content in WB-derived cryo. PI-cryo products may confer benefits in reducing pathogen transmission without affecting haemostatic function, but further in vivo assessment is warranted.

Rejuvenation solution as an adjunct cold storage solution maintains physiological haemoglobin oxygen affinity during early-storage period of red blood cells.

BACKGROUND: Red blood cell (RBC) units accumulate morphologic and metabolic lesions during storage before transfusion. Pyruvate-inosine-phosphate-adenine (PIPA) solutions (Rejuvesol, Biomet, Warsaw, IN) can be incubated with RBC units to mitigate storage lesions. This study proposes a PIPA treatment process, termed cold 'rejuvenation', using Rejuvesol as an adjunct additive solution, to prevent biomechanical storage lesions while avoiding the 1 h PIPA incubation required with standard PIPA treatment. We compared the efficacy of cold to standard 'rejuvenation' in improving metabolic lesions that occur during cold storage of RBCs, without altering function. METHODS: Twelve leucoreduced, A-positive RBC units were obtained. Each unit was aliquoted into either control (standard storage), washed (W), standard rejuvenation (SR) or cold rejuvenation (CR) groups, the latter two requiring washing. A volume-adjusted dose of Rejuvesol was instilled into the CR group upon receipt (Day 3). After 15 days of storage, p50, RBC deformability, in-bag haemolysis and mechanical fragility were analysed. 'Any treatment' is defined as W, SR and CR, with comparisons in reference to control. RESULTS: Higher p50s were seen in rejuvenated groups (>30 mmHg vs. <19 mmHg; P < 0·0001). Any treatment significantly increased elongation index (P = 0·034) but did not significantly increase in-bag haemolysis (P = 0·062). Mechanical fragility was not significantly different between groups (P = 0·055) at baseline, but the control (CTL) group was more fragile after 2 h in a cardiac bypass simulation than any treatment (P < 0·0001). CONCLUSIONS: This study demonstrates that rejuvenation (standard or cold) prevents the leftward p50 shift of storage lesions without detrimental effect on RBC deformity, in-bag haemolysis or mechanical fragility.

Metabolic impact of red blood cell exchange with rejuvenated red blood cells in sickle cell patients.

BACKGROUND: Red blood cell exchange (RCE) transfusions are a mainstay in the treatment of sickle cell anemia (SCA), and allow a temporary restoration of physiological parameters with respect to erythrocyte oxygen carrying capacity and systems metabolism. Recently, we noted that 1) RCE significantly impacts recipients' metabolism in SCA; 2) fresh and end-of-storage red blood cell (RBC) units differently impact systems of metabolism in healthy autologous recipients; and 3) phosphate/inosine/pyruvate/adenine (PIPA) solution reverses the metabolic age of stored RBCs. Therefore, we hypothesized that RCE with PIPA-treated RBC units could further increase the metabolic benefits of RCE in SCA patients. STUDY DESIGN AND METHODS: Circulating plasma and erythrocytes were collected from patients with SCA before and after RCE, with either conventional or PIPA-treated RBC units, prior to metabolomics analyses. RESULTS: Consistent with prior work, RCE significantly decreased circulating levels of markers of systemic hypoxemia (lactate, succinate) and decreased plasma levels of acyl-carnitines and amino acids. However, PIPA-treated exchanges were superior to untreated RCEs, with a higher energy state and an increased capacity to activate the pentose phosphate pathway and glutamine metabolism. In addition, RBCs and plasma from recipients of PIPA-treated RBC units resulted in significantly decreased levels of post-transfusion plasticizers, though at the expense of higher circulating levels of oxidized purines (hypoxanthine, xanthine, and the antioxidant urate). CONCLUSION: Transfusion of PIPA-treated RBCs further increases the metabolic benefits of RCE to patients with SCA, significantly reducing the levels of post-transfusion plasticizers.

Interval decline in hemoglobin A is associated with annual clinical event rate in sickle cell anemia patients receiving maintenance apheresis RBC exchange.

BACKGROUND: Apheresis red blood cell (RBC) exchange (RCE) is a standard intervention for patients with sickle cell anemia (SCA) who have had previous thromboembolic stroke or intractable chronic pain. Replacing sickling cells with those containing hemoglobin A (HbA) minimizes microvascular pathophysiology that produces clinical crises. Limited data exist regarding the interval changes in HbA between transfusions. We sought to describe the HbA decrement between RCE procedures and its relationship to clinical status. STUDY DESIGN AND METHODS: SCA patients (all hemoglobin SS disease) treated with maintenance RCE (n = 21) over a 15-month period at two neighboring institutions were retrospectively reviewed. Time-normalized daily HbA decrement was calculated to reflect loss of transfused RBCs, and annual events of either emergency department or hospital admissions for SCA complications were noted. Associations between HbA decrement and laboratory measures were calculated using mixed linear regression models and unpaired t test was used to compare HbA decrement between high and low event rate groups. RESULTS: A total of 31 events were recorded, and mean HbA decrement per day was 0.77 ± 0.16%. The mean interval between RCEs was 36 ± 12 days. Patients with more annual events exhibited a significantly greater daily HbA decrement (p = 0.007). No significant association between RBC unit age and HbA decrement or annual event rate was observed. CONCLUSIONS: Patients exhibiting greater daily HbA decrement were more likely to have multiple emergency department visits or admissions for sickling crises. Modulating HbA decrement may merit study as an intermediate metric for interventions to improve outcomes in hemoglobin SS disease.

Three-factor prothrombin complex concentrates for refractory bleeding after cardiovascular surgery within an algorithmic approach to haemostasis.

BACKGROUND/OBJECTIVES: Prothrombin complex concentrates (PCC) are increasingly administered off-label in the United States to treat bleeding in cardiovascular surgical patients and carry the potential risk for acquired thromboembolic side-effects after surgery. Therefore, we hypothesized that the use of low-dose 3-factor (3F) PCC (20-30 IU/kg), as part of a transfusion algorithm, reduces bleeding without increasing postoperative thrombotic/thromboembolic complications. MATERIALS/METHODS: After IRB approval, we retrospectively analysed 114 consecutive, complex cardiovascular surgical patients (age > 18 years), between February 2014 and June 2015, that received low-dose 3F-PCC (Profilnine® ), of which seven patients met established exclusion criteria. PCC was dosed according to an institutional perioperative algorithm. Allogeneic transfusions were recorded before and after PCC administration (n = 107). The incidence of postoperative thromboembolic events was determined within 30 days of surgery, and Factor II levels were measured in a subset of patients (n = 20) as a quality control measure to avoid excessive PCC dosing. RESULTS: Total allogeneic blood product transfusion reached a mean of 12·4 ± 9·9 units before PCC and 5·0 ± 6·3 units after PCC administration (P < 0·001). The mean PCC dose was 15·8 ± 7·1 IU/kg. Four patients (3·8%) each experienced an ischaemic stroke on postoperative day 1, 2, 4 and 27. Seven patients (6·5%) had acquired venous thromboembolic disease within 10 days of surgery. Median factor II level after transfusion algorithm adherence and PCC administration was 87%. CONCLUSIONS: 3F-PCC use for refractory bleeding after cardiovascular surgery resulted in reduced transfusion of allogeneic blood and blood products. Adherence to this algorithmic approach was associated with an acceptable incidence of postoperative thrombotic/thromboembolic complications.

Effects of red blood cell (RBC) transfusion on sickle cell disease recipient plasma and RBC metabolism.

BACKGROUND: Exchange transfusion is a mainstay in the treatment of sickle cell anemia. Transfusion recipients with sickle cell disease (SCD) can be transfused over 10 units per therapy, an intervention that replaces circulating sickle red blood cells (RBCs) with donor RBCs. Storage of RBCs makes the intervention logistically feasible. The average storage duration for units transfused at the Duke University Medical Center is approximately 2 weeks, a time window that should anticipate the accumulation of irreversible storage lesion to the RBCs. However, no metabolomics study has been performed to date to investigate the impact of exchange transfusion on recipients' plasma and RBC phenotypes. STUDY DESIGN AND METHODS: Plasma and RBCs were collected from patients with sickle cell anemia before transfusion and within 5 hours after exchange transfusion with up to 11 units, prior to metabolomics analyses. RESULTS: Exchange transfusion significantly decreased plasma levels of markers of systemic hypoxemia like lactate, succinate, sphingosine 1-phosphate, and 2-hydroxyglutarate. These metabolites accumulated in transfused RBCs, suggesting that RBCs may act as scavenger/reservoirs. Transfused RBCs displayed higher glycolysis, total adenylate pools, and 2,3-diphosphoglycerate, consistent with increased capacity to deliver oxygen. Plasma levels of acyl-carnitines and amino acids decreased, while fatty acids and potentially harmful phthalates increased upon exchange transfusion. CONCLUSION: Metabolic phenotypes confirm the benefits of the transfusion therapy in transfusion recipients with SCD and the reversibility of some of the metabolic storage lesion upon transfusion in vivo in 2-week-old RBCs. However, results also suggest that potentially harmful plasticizers are transfused.

Metabolomics evaluation of early-storage red blood cell rejuvenation at 4°C and 37°C.

BACKGROUND: Refrigerated red blood cell (RBC) storage results in the progressive accumulation of biochemical and morphological alterations collectively referred to as the storage lesion. Storage-induced metabolic alterations can be in part reversed by rejuvenation practices. However, rejuvenation requires an incubation step of RBCs for 1 hour at 37°C, limiting the practicality of providing "on-demand," rejuvenated RBCs. We tested the hypothesis that the addition of rejuvenation solution early in storage as an adjunct additive solution would prevent-in a time window consistent with the average age of units transfused to sickle cell recipients at Duke (15 days)-many of the adverse biochemical changes that can be reversed via standard rejuvenation, while obviating the incubation step. STUDY DESIGN AND METHODS: Metabolomics analyses were performed on cells and supernatants from AS-1 RBC units (n = 4), stored for 15 days. Units were split into pediatric bag aliquots and stored at 4°C. These were untreated controls, washed with or without rejuvenation, performed under either standard (37°C) or cold (4°C) conditions. RESULTS: All three treatments removed most metabolic storage by-products from RBC supernatants. However, only standard and cold rejuvenation provided significant metabolic benefits as judged by the reactivation of glycolysis and regeneration of adenosine triphosphate and 2,3-diphosphoglycerate. Improvements in energy metabolism also translated into increased capacity to restore the total glutathione pool and regenerate oxidized vitamin C in its reduced (ascorbate) form. CONCLUSION: Cold and standard rejuvenation of 15-day-old RBCs primes energy and redox metabolism of stored RBCs, while providing a logistic advantage for routine blood bank processing workflows.

Estimation of Achievable Oxygen Consumption Following Transfusion With Rejuvenated Red Blood Cells.

Erythrocyte storage induces a nonphysiological increase in hemoglobin-oxygen affinity (quantified by low p50, the oxygen tension at 50% hemoglobin saturation), which can be restored through biochemical rejuvenation. The objective was to mathematically model the impact of transfusing up to 3 standard allogeneic units or rejuvenated units on oxygen delivery (DO2) and oxygen consumption (VO2). Oxygen dissociation curves were generated from additive solution-1 red blood cell (RBC) leukoreduced units (n = 7) before and after rejuvenation following manufacturer's instructions. Two of these units were used to prepare standard or rejuvenated donor RBC and added to samples of fresh whole blood. These admixtures were used to construct an in vitro transfusion model of postoperative anemia and determine a linear equation for calculating the sample p50, which was subsequently used to calculate DO2 and VO2 after simulated transfusions. Whole blood-packed red blood cell unit admixture p50s could be predicted from a linear model including the p50 of its components, the mass fraction of the transfused component, and interaction terms (R2 = .99, P < 0.001). Transfusion with standard units slightly, but significantly, increased projected DO2 compared with rejuvenated units (P = 0.03), but rejuvenated units markedly increased projected VO2 (P = 0.03). Standard units did not significantly change VO2 relative to pre-transfusion levels (P > 0.1). Using high-p50, rejuvenated RBC in simulated transfusions greatly improved projected VO2, indicating the potential for increased end-organ oxygen availability compared with standard transfusion. Patient capacity to increase cardiac output after cardiac surgery may be limited. Transfusing high-p50 RBC in this setting may improve the perioperative care of these patients.

Should modulation of p50 be a therapeutic target in the critically ill?

INTRODUCTION: A defining feature of human hemoglobin is its oxygen binding affinity, quantified by the partial pressure of oxygen at which hemoglobin is 50% saturated (p50), and the variability of this parameter over a range of physiological and environmental states. Modulation of this property of hemoglobin can directly affect the degree of peripheral oxygen offloading and tissue oxygenation. Areas covered: This review summarizes the role of hemoglobin oxygen affinity in normal and abnormal physiology and discusses the current state of the literature regarding artificial modulation of p50. Hypoxic tumors, sickle cell disease, heart failure, and transfusion medicine are discussed in the context of recent advances in hemoglobin oxygen affinity manipulation. Expert commentary: Of particular clinical interest is the possibility of maintaining adequate end-organ oxygen availability in patients with anemia or compromised cardiac function via an increase in systemic p50. This increase in systemic p50 can be achieved with small molecule drugs or a packed red blood cell unit processing variant called rejuvenation, and human trials are needed to better understand the potential clinical benefits to modulating p50.