Experiences with frozen blood products in the Netherlands military

Downscaling platelet cryopreservation: Are platelets frozen in tubes comparable to standard cryopreserved platelets?

BACKGROUND

Platelet cryopreservation extends the shelf-life to at least 2 years. However, platelets are altered during the freeze/thaw process. Downscaling platelet cryopreservation by freezing in tubes would enable rapid screening of novel strategies to improve the quality of cryopreserved platelets (CPPs). The aim of this study was to characterize the effect of freezing conditions on the in vitro phenotype and function of platelets frozen in a low volume compared to standard CPPs.

METHODS

Platelets were prepared for cryopreservation using 5%-6% DMSO and processed using standard protocols or aliquoted into 2 mL tubes. Platelets were hyperconcentrated to 25 mL (standard CPPs) or 200 μL (tubes) before freezing at -80°C (n = 8). Six insulators/controlled rate freezing containers were used to vary the freezing rate of platelets in tubes. Platelets were thawed, resuspended in plasma, and then assessed by flow cytometry and thromboelastography.

RESULTS

The use of different insulators for tubes changed the freezing rate of platelets compared to platelets frozen using the standard protocol (p < .001). However, this had no impact on the recovery of the platelets (p = .87) or the proportion of platelets expressing GPIbα (p = .46) or GPVI (p = .07), which remained similar between groups. A lower proportion of platelets frozen in tubes externalized phosphatidylserine compared to standard CPPs (p < .001). The clot-forming ability (thromboelastography) of platelets was similar between groups (p > .05).

CONCLUSION

Freezing platelets in tubes modified the freezing rate and altered some platelet characteristics. However, the functional characteristics remained comparable, demonstrating the feasibility of downscaling platelet cryopreservation for high-throughput exploratory investigations.

A randomized cross-over study of cryopreserved platelets in prophylactic transfusions of thrombocytopenic patients

BACKGROUND

The short shelf-life of liquid-stored platelets (LP) at 20-24°C poses shortage and wastage challenges. Cryopreserved platelets have significantly extended shelf-life, and were safe and efficacious for therapeutic transfusions of bleeding patients in the Afghanistan conflict and phase 2 randomized studies. Although hematology patients account for half of platelets demand, there is no randomized study on prophylactic cryopreserved platelet transfusions in them.

METHODS

We performed a phase 1b/2a randomized cross-over study comparing the safety and efficacy of cryopreserved buffy coat-derived pooled platelets (CP) to LP in the prophylactic transfusions of thrombocytopenic hematology patients.

RESULTS

A total of 18 adults were randomly assigned 1:1 to CP and LP for their first thrombocytopenic period (TP) of up to 28-days. A total of 14 crossed over to the other platelet-arm for the second TP. Overall, 17 subjects received 51 CP and 15 received 52 LP. CP-arm had more treatment emergent adverse event (29.4% vs. 13.3% of subjects, 9.8% vs. 3.8% of transfusions) than LP-arm but all were mild. No thromboembolism was observed. Both arms had similar bleeding rates (23.5% vs. 26.7% of subjects) which were all mild. Subjects in CP-arm had lower average corrected count increments than LP-arm (mean [SD] 5.6 [4.20] vs. 22.6 [9.68] ×109 /L at 1-4 h, p < .001; 5.3 [4.84] vs. 18.2 [9.52] ×109 /L at 18-30 h, p < .001). All TEG parameters at 1-4 h and maximum amplitude (MA) at 18-30 h improved from baseline post-CP transfusion (p < .05) though improvements in K-time and MA were lower than LP (p < .05).

DISCUSSION

During shortages, CP may supplement LP in prophylactic transfusions of thrombocytopenic patients.

Cryopreserved platelets washed with a dialysis machine for dimethyl sulphoxide removal

BACKGROUND AND OBJECTIVES

Cryopreserved platelets (cPLTs) can be stored for years and are mainly used in military settings. However, the commonly used cryoprotectant dimethyl sulphoxide (DMSO) has toxic side effects when utilized in high quantities. We developed a novel method to aseptically remove DMSO from thawed cPLTs by dialysis.

MATERIALS AND METHODS

One unit of platelets (N = 6) was mixed with 75 mL of 27% DMSO within 4 days after collection and stored at -80°C for 1 week. The platelet counts, platelet distribution width, mean platelet volume (MPV), platelet activity, platelet release, platelet aggregation, platelet metabolism indicators and platelet ultrastructural features (determined by electron microscopy) of the samples at the pre-freeze, post-thaw wash (post-TW) and 24 h post-thaw wash (24-PTW) stages were determined and compared.

RESULTS

The DMSO clearance rate from the post-TW platelets was 95.56 ± 1.3%, and the platelet recovery rate after washing was 74.66 ± 6.34%. The total count, activity, release factors, aggregation and thrombolytic ability of the post-TW platelets were lower, whereas the MPV and apoptosis rates were higher compared with those of the pre-freeze platelets. The lactic acid, glucose and potassium ions released from the platelets during washing were filtered away by the dialyser, which significantly reduced their concentration. However, 24-PTW platelets were metabolically active, resulting in a decrease in pH and glucose content and an increase in lactic acid content. The level of potassium ions remained low after 24 h of storage and washing. The pre-freeze platelets maintained their normal disc shape and exhibited an open canalicular system (OCS) and a dense tubular system. The cPLTs appeared irregular after washing, with protruding pseudopodia and an extensive OCS, which increased the release of their contents.

CONCLUSION

We developed a novel dialysis method to effectively remove DMSO from cPLTs under aseptic conditions and maintain platelet quality. The clinical efficacy of our method remains to be determined. However, the function of the platelets declined 24 h after washing, making them unsuitable for transfusion.

Identification of platelet subpopulations in cryopreserved platelet components using multi-colour imaging flow cytometry

Cryopreservation of platelets, at  - 80 °C with 5-6% DMSO, results in externalisation of phosphatidylserine and the formation of extracellular vesicles (EVs), which may mediate their procoagulant function. The phenotypic features of procoagulant platelets overlap with other platelet subpopulations. The aim of this study was to define the phenotype of in vitro generated platelet subpopulations, and subsequently identify the subpopulations present in cryopreserved components. Fresh platelet components (n = 6 in each group) were either unstimulated as a source of resting platelets; or stimulated with thrombin and collagen to generate a mixture of aggregatory and procoagulant platelets; calcium ionophore (A23187) to generate procoagulant platelets; or ABT-737 to generate apoptotic platelets. Platelet components (n = 6) were cryopreserved with DMSO, thawed and resuspended in a unit of thawed plasma. Multi-colour panels of fluorescent antibodies and dyes were used to identify the features of subpopulations by imaging flow cytometry. A combination of annexin-V (AnnV), CD42b, and either PAC1 or CD62P was able to distinguish the four subpopulations. Cryopreserved platelets contained procoagulant platelets (AnnV+/PAC1-/CD42b+/CD62P+) and a novel population (AnnV+/PAC1-/CD42b+/CD62P-) that did not align with the phenotype of aggregatory (AnnV-/PAC1+/CD42b+/CD62P+) or apoptotic (AnnV+/PAC1-/CD42b-/CD62P-) subpopulations. These data suggests that the enhanced haemostatic potential of cryopreserved platelets may be due to the cryo-induced development of procoagulant platelets, and that additional subpopulations may exist.

Cryopreserved platelets in bleeding management in remote hospitals: A clinical feasibility study in Sweden

Background

Balanced transfusions, including platelets, are critical for bleeding patients to maintain hemostasis. Many rural hospitals have no or limited platelet inventory, with several hours of transport time from larger hospitals. This study aimed to evaluate the feasibility of using cryopreserved platelets that can be stored for years, in remote hospitals with no or limited platelet inventory.

Material and methods

Three remote hospitals participated in a prospective study including adult bleeding patients where platelet transfusions were indicated. Cryopreserved platelets were prepared in a university hospital, concentrated in 10 ml, transported on dry ice, and stored at -80°C at the receiving hospital. At request, the concentrated platelet units were thawed and diluted in fresh frozen plasma. The indications, blood transfusion needs, and laboratory parameters pre- and post-transfusion, as well as logistics, such as time from request to transfusion and work efforts in preparing cryopreserved platelets, were evaluated.

Results

Twenty-three bleeding patients were included. Nine patients (39%) were treated for gastrointestinal bleeding, five (22%) for perioperative bleeding, and four (17%) for trauma bleeding. The transfusion needs were 4.9 ± 3.3 red blood cell units, 3.2 ± 2.3 plasma units, and 1.9 ± 2.2 platelet units, whereof cryopreserved were 1.5 ± 1.1 (mean ± SD). One patient had a mild allergic reaction. We could not show the difference in laboratory results between pre- and post-transfusion of the cryopreserved units in the bleeding patients. The mean time from the order of cryopreserved platelets to transfusion was 64 min, with a range from 25 to 180 min.

Conclusion

Cryopreserved platelets in remote hospitals are logistically feasible in the treatment of bleeding. The ability to have platelets in stock reduces the time to platelet transfusion in bleeding patients where the alternative often is many hours delay. Clinical effectiveness and safety previously shown in other studies are supported in this small feasibility study.

Frozen for combat: Quality of deep-frozen thrombocytes, produced and used by The Netherlands Armed Forces 2001-2021

BACKGROUND

The Netherlands Armed Forces (NLAF) are using -80°C deep-frozen thrombocyte concentrate (DTC) since 2001. The aim of this study is to investigate the effect of storage duration and alterations in production/measurement techniques on DTC quality. It is expected that DTC quality is unaffected by storage duration and in compliance with the European guidelines for fresh and cryopreserved platelets.

STUDY DESIGN AND METHODS

Pre-freeze and post-thaw product platelet content and recovery were collected to analyze the effects of dimethyl sulfoxide (DMSO) type, duration of frozen storage (DMSO-1 max 12 years and DMSO-2 frozen DTC max 4 years at -80°C) and type of plasma used to suspend DTC. Coagulation characteristics of thawed DTC, plasma and supernatant of DTC (2× 2500 G) were measured with Kaolin thromboelastography (TEG) and phospholipid (PPL) activity assay.

RESULTS

Platelet content and recovery of DTC is ±10%-15% lower in short-stored products and remained stable when stored beyond 0.5 years. Thawed DTC (n = 1724) were compliant to the European guidelines (98.1% post-thaw product recovery ≥50% from original product, 98.3% ≥200 × 10⁹ platelets/unit). Compared to DMSO-1, products frozen with DMSO-2 showed ±8% reduced thaw-freeze recovery, a higher TEG clot strength (MA 58 [6] vs. 64 [8] mm) and same ±11 s PPL clotting time. The use of cold-stored thawed plasma instead of fresh thawed plasma did not influence product recovery or TEG-MA.

DISCUSSION

Regardless of alterations, product quality was in compliance with European guidelines and unaffected by storage duration up to 12 years of -80°C frozen storage.

Cryopreserved platelets compared with liquid-stored platelets for the treatment of surgical bleeding: protocol for two multicentre randomised controlled blinded non-inferiority trials (the CLIP-II and CLIPNZ-II trials)

INTRODUCTION

Cryopreservation at -80°C in dimethylsulphoxide extends platelet shelf-life from 7 days to 2 years. Only limited comparative trial data supports the safety and effectiveness of cryopreserved platelets as a treatment for surgical bleeding. Cryopreserved platelets are not currently registered for civilian use in most countries.

METHODS AND ANALYSIS

CLIP-II and CLIPNZ-II are harmonised, blinded, multicentre, randomised, controlled clinical non-inferiority trials comparing bleeding, transfusion, safety and cost outcomes associated with cryopreserved platelets versus conventional liquid platelets as treatment for bleeding in cardiac surgery. CLIP-II is planning to enrol patients in 12 tertiary hospitals in Australia; CLIPNZ-II will recruit in five tertiary hospitals in New Zealand. The trials use near-identical protocols aside from details of cryopreserved platelet preparation. Patients identified preoperatively as being at high risk of requiring a platelet transfusion receive up to three units of study platelets if their treating doctor considers platelet transfusion is indicated. The primary endpoint is blood loss through the surgical drains in the 24 hours following intensive care unit (ICU) admission after surgery. Other endpoints are blood loss at other time points, potential complications, adverse reactions, transfusion and fluid requirement, requirement for procoagulant treatments, time to commencement of postoperative anticoagulants, delay between platelet order and commencement of infusion, need for reoperation, laboratory and point-of-care clotting indices, cost, length of mechanical ventilation, ICU and hospital stay, and mortality. Transfusing 202 (CLIP-II) or 228 (CLIPNZ-II) patients with study platelets will provide 90% power to exclude the possibility of greater than 20% inferiority in the primary endpoint. If cryopreserved platelets are not inferior to liquid-stored platelets, the advantages of longer shelf-life would justify rapid change in clinical practice. Cost-effectiveness analyses will be incorporated into each study such that, should clinical non-inferiority compared with standard care be demonstrated, the hospitals in each country that would benefit most from changing to a cryopreserved platelet blood bank will be known.

ETHICS AND DISSEMINATION

CLIP-II was approved by the Austin Health Human Research Ethics Committee (HREC/54406/Austin-2019) and by the Australian Red Cross Lifeblood Ethics Committee (2019#23). CLIPNZ-II was approved by the New Zealand Southern Health and Disability Ethics Committee (21/STH/66). Eligible patients are approached for informed consent at least 1 day prior to surgery. There is no provision for consent provided by a substitute decision-maker. The results of the two trials will be submitted separately for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBERS

NCT03991481 and ACTRN12621000271808.

The haemostatic effect of deep-frozen platelets versus room temperature-stored platelets in the treatment of surgical bleeding: MAFOD—study protocol for a randomized controlled non-inferiority trial

Background

The Netherlands Armed Forces have been successfully using deep-frozen (− 80 °C) thrombocyte concentrate (DTC) for the treatment of (massive) bleeding trauma patients in austere environments since 2001. However, high-quality evidence for the effectiveness and safety of DTCs is currently lacking. Therefore, the MAssive transfusion of Frozen bloOD (MAFOD) trial is designed to compare the haemostatic effect of DTCs versus room temperature-stored platelets (RSP) in the treatment of surgical bleeding.

Methods

The MAFOD trial is a single-blinded, randomized controlled non-inferiority trial and will be conducted in three level 1 trauma centres in The Netherlands. Patients 12 years or older, alive at hospital presentation, requiring a massive transfusion including platelets and with signed (deferred) consent will be included. The primary outcome is the percentage of patients that have achieved haemostasis within 6 h and show signs of life. Haemostasis is defined as the time in minutes from arrival to the time of the last blood component transfusion (plasma/platelets or red blood cells), followed by a 2-h transfusion-free period. This is the first randomized controlled study investigating DTCs in trauma and vascular surgical bleeding.

Discussion

The hypothesis is that the percentage of patients that will achieve haemostasis in the DTC group is at least equal to the RSP group (85%). With a power of 80%, a significance level of 5% and a non-inferiority limit of 15%, a total of 71 patients in each arm are required, thus resulting in a total of 158 patients, including a 10% refusal rate. The data collected during the study could help improve the use of platelets during resuscitation management. If proven non-inferior in civilian settings, frozen platelets may be used in the future to optimize logistics and improve platelet availability in rural or remote areas for the treatment of (massive) bleeding trauma patients in civilian settings.

Trial registration

ClinicalTrials.gov NCT05502809. Registered on 16 August 2022.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06739-2.

There and Back Again: The Once and Current Developments in Donor-Derived Platelet Products for Products for Hemostatic Therapy

Over 100 years ago, Duke transfused whole blood to a thrombocytopenic patient to raise the platelet count and prevent bleeding. Since then, platelet transfusions have undergone numerous modifications from whole blood-derived platelet-rich plasma to apheresis-derived platelet concentrates. Similarly, the storage time and temperature have changed. The mandate to store platelets for a maximum of 5-7 days at room temperature has been challenged by recent clinical trial data, ongoing difficulties with transfusion-transmitted infections, and recurring periods of shortages, further exacerbated by the COVID-19 pandemic. Alternative platelet storage approaches are as old as the first platelet transfusions. Cold-stored platelets may offer increased storage times (days) and improved hemostatic potential at the expense of reduced circulation time. Frozen (cryopreserved) platelets extend the storage time to years but require storage at -80 °C and thawing before transfusion. Lyophilized platelets can be powder-stored for years at room temperature and reconstituted within minutes in sterile water but are probably the least explored alternative platelet product to date. Finally, whole blood offers the hemostatic spectrum of all blood components but has challenges, such as ABO incompatibility. While we know more than ever before about the in vitro properties of these products, clinical trial data on these products are accumulating. The purpose of this review is to summarize the findings of recent preclinical and clinical studies on alternative, donor-derived platelet products.

Cryopreservation alters the immune characteristics of platelets

BACKGROUND

Cryopreserved platelets are under clinical evaluation as they offer improvements in shelf-life and potentially hemostatic effectiveness. However, the effect of cryopreservation on characteristics related to the immune function of platelets has not been examined.

STUDY DESIGN AND METHODS

Buffy coat derived platelets were cryopreserved at -80°C using 5%-6% dimethylsulfoxide (DMSO, n = 8). Paired testing was conducted pre-freeze (PF), post-thaw (PT0), and after 24 h of post-thaw storage at room temperature (PT24). The concentration of biological response modifiers (BRMs) in the supernatant was measured using commercial ELISAs and surface receptor abundance was assessed by flow cytometry.

RESULTS

Cryopreservation resulted in increased RANTES, PF4, and C3a but decreased IL-1β, OX40L, IL-13, IL-27, CD40L, and C5a concentrations in the supernatant, compared to PF samples. C4a, endocan, and HMGB1 concentrations were similar between the PF and PT0 groups. The abundance of surface-expressed P-selectin, siglec-7, TLR3, TLR7, and TLR9 was increased PT0; while CD40, CLEC2, ICAM-2, and MHC-I were decreased, compared to PF. The surface abundance of CD40L, B7-2, DC-SIGN, HCAM, TLR1, TLR2, TLR4, and TLR6 was unchanged by cryopreservation. Following 24 h of post-thaw storage, all immune associated receptors and TLRs increased to levels higher than observed on PF and PT0 platelets.

CONCLUSION

Cryopreservation alters the immune phenotype of platelets. Understanding the clinical implications of the observed changes in BRM release and receptor abundance are essential, as they may influence the likelihood of adverse events.

A pilot randomized clinical trial of cryopreserved versus liquid-stored platelet transfusion for bleeding in cardiac surgery: The cryopreserved versus liquid platelet-New Zealand pilot trial

BACKGROUND AND OBJECTIVES

Platelets for transfusion have a shelf-life of 7 days, limiting availability and leading to wastage. Cryopreservation at -80°C extends shelf-life to at least 1 year, but safety and effectiveness are uncertain.

MATERIALS AND METHODS

This single centre blinded pilot trial enrolled adult cardiac surgery patients who were at high risk of platelet transfusion. If treating clinicians determined platelet transfusion was required, up to three units of either cryopreserved or liquid-stored platelets intraoperatively or during intensive care unit admission were administered. The primary outcome was protocol safety and feasibility.

RESULTS

Over 13 months, 89 patients were randomized, 23 (25.8%) of whom received a platelet transfusion. There were no differences in median blood loss up to 48 h between study groups, or in the quantities of study platelets or other blood components transfused. The median platelet concentration on the day after surgery was lower in the cryopreserved platelet group (122 × 10³ /μl vs. 157 × 10³ /μl, median difference 39.5 ×10³ /μl, p = 0.03). There were no differences in any of the recorded safety outcomes, and no adverse events were reported on any patient. Multivariable adjustment for imbalances in baseline patient characteristics did not find study group to be a predictor of 24-h blood loss, red cell transfusion or a composite bleeding outcome.

CONCLUSION

This pilot randomized controlled trial demonstrated the feasibility of the protocol and adds to accumulating data supporting the safety of this intervention. Given the clear advantage of prolonged shelf-life, particularly for regional hospitals in New Zealand, a definitive non-inferiority phase III trial is warranted.

Cryopreserved buffy-coat-derived platelets reconstituted in platelet additive solution: A safe and available product with sufficient haemostatic effectiveness

BACKGROUND

Platelets (PLTs) stored at 20-24 °C have a short shelf life of only 5 days, which can result in their restricted availability. PLT cryopreservation extends the shelf life to 2 years.

METHODS

We implemented a method of PLT freezing at -80 °C in 5-6% dimethyl sulfoxide. Buffy-coat-derived leucodepleted fresh PLTs blood group O (FP) were used for cryopreservation. Cryopreserved pooled leucodepleted PLTs (CPP) were thawed at 37 °C, reconstituted in PLT additive solution SSP + and compared to FP regarding PLT content, PLT concentration, pH, volume, PLT loss, anti-A/B antibody titre, total protein, plasma content, and PLT swirling. Clot properties were evaluated via rotational thromboelastometry. PLT microparticle number and surface receptor phenotype were assessed via flow cytometry.

RESULTS

CPP met the required quality parameters. The mean freeze-thaw PLT loss was 22.24 %. Anti-A/B antibody titre and plasma content were significantly lower in CPP. CPP were characterised by faster clot initiation and form stable PLT clots. The number of PLT microparticles increased 25 times in CPP and there were more particles positive for the activation marker CD62 P compared to FP.

CONCLUSION

Thawing and reconstitution are easy and fast processes if platelet additive solution is used. Low anti-A/B antibody titre and plasma content make possible the use of CPP of blood group O reconstituted in SSP + as universal ABO products, including clinical situations where washed PLTs are required. Clot properties evaluated via rotational thromboelastometry demonstrated that CPP retain a significant part of their activity compare to FP and are haemostatically effective.

Cryopreservation of platelets treated with riboflavin and UV light and stored at -80°C for 1 year

BACKGROUND

The combination of pathogen reduction technologies (PRTs) and cryopreservation can contribute to building a safe and durable platelet (PLT) inventory. Information about cryopreserved riboflavin and UV light-treated PLTs is scarce.

STUDY DESIGN AND METHODS

Twenty-four buffy coat (BC) PLT concentrates were grouped into 12 type-matched pairs, pooled, and divided into 12 non-PRT-treated control units and 12 riboflavin and UV light PRT-treated test units. Both were cryopreserved with 5% DMSO and stored at -80°C for 1 year. The cryopreservation method used was designed to avoid the formation of aggregates. PLT variables (PLT recovery, swirling, pH, MPV, and LDH) and hemostatic function measured by thromboelastography (TEG) were analyzed before cryopreservation (day 1) and post-cryopreservation at day 14 and months 3, 6, and 12 of storage at -80°C. The analyses were carried out within 1-h post-thaw.

RESULTS

No aggregates were found in either PLT group at any time. Swirling was observed in both groups. MPV increased and mean pH values decreased over time (p < .001), but the mean pH value was never below 6.4 in either group after 12 months of storage at -80°C. PLT recovery was good and clotting time became significantly shorter over the storage period in both groups (p < .001).

CONCLUSION

Our cryopreservation and thawing method prevented aggregate formation in cryopreserved riboflavin-UV-light-treated PLTs, which exhibited good recovery, swirling, pH > 6.4, and procoagulant potential, as evidenced by a reduced clotting time after 12 months of storage at -80°C. The clinical relevance of these findings should be further investigated in clinical trials.

Frozen Blood Reserves

Frozen blood reserves are an important component in meeting blood needs. The idea behind a frozen blood reserve is twofold: to freeze units of rare blood types for later use by patients with special transfusion needs and for managing special transfusion circumstances. The permeating additive glycerol is used as a cryoprotectant to protect red blood cells (RBCs) from freezing damage. The use of thawed RBCs has been hampered by a 24-h outdating period due to the potential bacterial contamination when a functionally open system is used for addition and removal of the glycerol. The introduction of an automated, functionally closed system for glycerolization and deglycerolization of RBCs improved the operational practice. More importantly, the closed process allowed for extended shelf life of the thawed RBCs. In the current chapter, a cryopreservation procedure for RBCs using a functionally closed processing system is described.

Transfusion in critical care: Past, present and future

Anaemia and coagulopathy are common in critically ill patients and are associated with poor outcomes, including increased risk of mortality, myocardial infarction, failure to be liberated from mechanical ventilation and poor physical recovery. Transfusion of blood and blood products remains the corner stone of anaemia and coagulopathy treatment in critical care. However, determining when the benefits of transfusion outweigh the risks of anaemia may be challenging in some critically ill patients. Therefore, the European Society of Intensive Care Medicine prioritised the development of a clinical practice guideline to address anaemia and coagulopathy in non-bleeding critically ill patients. The aims of this article are to: (1) review the evolution of transfusion practice in critical care and the direction for future developments in this important area of transfusion medicine and (2) to provide a brief synopsis of the guideline development process and recommendations in a format designed for busy clinicians and blood bank staff. These clinical practice guidelines provide recommendations to clinicians on how best to manage non-bleeding critically ill patients at the bedside. More research is needed on alternative transfusion targets, use of transfusions in special populations (e.g., acute neurological injury, acute coronary syndromes), use of anaemia prevention strategies and point-of-care interventions to guide transfusion strategies.

Prolonged (post-thaw) shelf life of -80°C frozen AB apheresis plasma

BACKGROUND

Early plasma transfusion is important in the treatment of patients with major hemorrhage. Prolonged shelf life of AB type frozen −80°C and cold‐stored (4°C) deep frozen plasma (DFP) will improve strategic stock management, minimize need for resupply, and make pre‐hospital implementation more feasible.

METHODS AND MATERIALS

Plasma products type AB of different age and origin (−30°C Fresh Frozen [(FFP], −80°C DFP [short (±1 year) and long (±7 year)] stored) were thawed (Day 0), stored at 4°C, and sampled on Days 7 and 14. Additionally, samples of plasma containing blood products (Octaplas LG®, whole blood and platelets) were compared for coagulation factor activity, phospholipid clotting time (PPL), and kaolin TEG during 4°C or 22°C storage.

RESULTS

Coagulation profiles of FFP, short‐ and long‐stored −80°C DFP were not significantly different after thaw. Cold storage did not affect fibrinogen, Protein C, and Antithrombin III activities whereas factor V, VII, VIII, and Protein S decreased in all blood products. After 14 days DFP still meets the guidelines for clinical use, except for Protein S (0.4 IU/mL). With exception of Octaplas LG®, phospholipid activity and TEG coagulation were similar between plasma containing blood components during storage.

CONCLUSION

AB DFP quality was unaffected by almost 7 years of frozen storage. Quality of thawed 14‐day stored AB DFP met, with exception of Protein S, all minimal guidelines which implies that its quality is sufficient for use in the (pre)‐hospital (military) environment for treatment of major hemorrhage.

Characterizing the ability of an ice recrystallization inhibitor to improve platelet cryopreservation

Improving aspects of platelet cryopreservation would help ease logistical challenges and potentially expand the utility of frozen platelets. Current cryopreservation procedures damage platelets, which may be caused by ice recrystallization. We hypothesized that the addition of a small molecule ice recrystallization inhibitor (IRI) to platelets prior to freezing may reduce cryopreservation-induced damage and/or improve the logistics of freezing and storage. Platelets were frozen using standard conditions of 5-6% dimethyl sulfoxide (Me₂SO) or with supplementation of an IRI, N-(2-fluorophenyl)-d-gluconamide (2FA), prior to storage at -80 °C. Alternatively, platelets were frozen with 5-6% Me₂SO at -30 °C or with 3% Me₂SO at -80 °C with or without 2FA supplementation. Supplementation of platelets with 2FA improved platelet recovery following storage under standard conditions (p = 0.0017) and with 3% Me₂SO (p = 0.0461) but not at -30 °C (p = 0.0835). 2FA supplementation was protective for GPVI expression under standard conditions (p = 0.0011) and with 3% Me₂SO (p = 0.0042). Markers of platelet activation, such as phosphatidylserine externalization and microparticle release, were increased following storage at -30 °C or with 3% Me₂SO, and 2FA showed no protective effect. Platelet function remained similar regardless of 2FA, although functionality was reduced following storage at -30 °C or with 3% Me₂SO compared to standard cryopreserved platelets. While the addition of 2FA to platelets provided a small level of protection for some quality parameters, it was unable to prevent alterations to the majority of in vitro parameters. Therefore, it is unlikely that ice recrystallization is the major cause of cryopreservation-induced damage.

The use of cryopreserved platelets in a trauma-induced hemorrhage model

BACKGROUND

Cryopreserved platelet products can be stored for years and are mainly used in military settings. Following thawing, cryopreserved platelets are activated, resulting in faster clot formation but reduced aggregation in vitro, rendering their efficacy in bleeding unknown. Also, concerns remain on the safety of these products. The aim was to investigate the efficacy and safety of cryopreserved platelets in a rat model of traumatic hemorrhage.

STUDY DESIGN AND METHODS

After 1 hour of shock, rats (n = 13/group) were randomized to receive a balanced transfusion pack (1:1:1 red blood cell:plasma:platelet) made from syngeneic rat blood, containing either liquid stored platelets or cryopreserved platelets. Primary outcome was the transfusion volume required to obtain a mean arterial pressure (MAP) of 60 mmHg. Secondary outcomes were coagulation as assessed by thromboelastometry (ROTEM®) and organ failure as assessed by biochemistry and histopathology.

RESULTS

The transfusion volume to obtain a MAP of 60 mmHg was lower in animals receiving cryopreserved platelets (5.4 [4.1-7.1] mL/kg) compared to those receiving liquid stored platelets (7.5 [6.4-8.5] mL/kg, p < 0.05). ROTEM® clotting times were shorter (45 [41-48] vs. 49 [45-53]sec, p < 0.05), while maximum clot firmness was slightly lower (68 [67-68] vs. 69 [69-71]mm, p < 0.01). Organ failure was similar in both groups.

CONCLUSIONS

Use of cryopreserved platelets required less transfusion volume to reach a targeted MAP compared to liquid stored platelets, while organ injury was similar. These results provide a rationale for clinical trials with cryopreserved platelets in (traumatic) bleeding.

From battlefront to homefront: creation of a civilian walking blood bank

Hemorrhagic shock remains the leading cause of preventable death on the battlefield, despite major advances in trauma care. Early initiation of balanced resuscitation has been shown to decrease mortality in the hemorrhaging patient. To address transfusion limitations in austere environments or in the event of multiple casualties, walking blood banks have been used in the combat setting with great success. Leveraging the success of the region-wide whole blood program in San Antonio, Texas, we report a novel plan that represents a model response to mass casualty incidents.

-80 °C deep frozen erythrocytes during military operations. The Dutch frozen concept

The Dutch military uses frozen blood products for the treatment of bleeding trauma patients during military deployments. With -80 °C frozen blood products it is possible to follow operational demand while reducing the number of resupply transports and loss of products due to expiration. In this paper lessons learned are described on efficient blood management with -80 °C deep-frozen erythrocytes (DEC).

Calcium chelation: a novel approach to reduce cryopreservation-induced damage to frozen platelets

BACKGROUND

Cryopreserved platelets are phenotypically and functionally different to conventionally stored platelets. Calcium may be released from internal stores during the freeze-thaw process, initiating signaling events which lead to these alterations. It was hypothesized that the addition of a calcium chelator prior to cryopreservation may mitigate some of these changes.

METHODS

Buffy coat-derived platelets that had been pooled and split were tested fresh and following cryopreservation (n = 8 per group). Platelets were cryopreserved using 5%-6% dimethylsulfoxide (DMSO) or were supplemented with increasing concentrations of the internal calcium chelator, BAPTA-AM (100 μM, 200 μM, or 400 μM), prior to storage at -80°C.

RESULTS

Supplementation of platelets with BAPTA-AM prior to freezing improved platelet recovery in a dose response manner (400 μM: 84 ± 2%) compared to standard DMSO cryopreserved platelets (70 ± 4%). There was a loss of GPIbα, GPVI, and GPIIb/IIIa receptors on platelets following cryopreservation, which was rescued when platelets were supplemented with BAPTA-AM (400 μM: p < 0.0001 for all). Platelet activation markers, such as phosphatidylserine and P-selectin, were externalized on platelets following cryopreservation. However, the addition of BAPTA-AM significantly reduced the increase of these activation markers on cryopreserved platelets (400 μM: p < 0.0001 for both). Both cryopreserved platelet groups exhibited similar functionality as assessed by thromboelastography, forming clots at a faster rate than fresh platelets.

CONCLUSIONS

This study demonstrates that calcium plays a crucial role in mediating cryopreservation-induced damage to frozen platelets. The addition of the calcium chelator, BAPTA-AM, prior to cryopreservation reduces this damage.

Emergency Supply Policy of Cryopreserved RBC and PLT: The Czech Republic Concept

Supply of blood for urgent substitution is a strategic logistical problem for the military medical services across the world. The limited shelf life of blood- derived bioproductsin the liquid state and the need for special transport and use conditions, apart from donor and donations availability are among the causes for concern. To solve these problems many national health-care authorities implemented the national emergency blood crisis policy, to get a large amount of blood at any time at any place in the case of disaster, terrorist attack or war. The civil therapeutic problems in immunohematolgy cases can also be solved by stocks of fresh and cryopreserved homologous or autologous blood for patients with rare RBCs antigens or HLA / HPA platelet refractoriness with no chance to use common blood. The short shelf life of fresh platelets limits their efficient inventory management and availability during a massive transfusion protocol. Building an inventory of frozen blood components can mitigate the risk of insufficient availability. Since the beginning of the century in the Czech Republic, used, like other countries, the use of of cryopreserved blood-derived bioproducts has become the current method used to overcome the shortages of a timely supply. The Military University Hospital, Prague, and its bank of cryopreserved blood have been operating under this policy since 2006. There is currently a stock of frozen RBCs for military reserve, for a national blood crisis and, also, a stock of rare RBC units. For crisis management there are also stored, frozen PLTs, which are used in the treatment of heavily bleeding polytrauma patients. Both the containment and research development mitigation policy programs are in place for civil / military emergency situations. Even pathogen reduced frozen PLTs and frozen RBCs were successfully investigated for clinical use if demands arose. Currently, it is possible to meet operational demand while reducing the number of resupply transports and loss of products due to expiration. A lesson has been learned from the current containment, reseach and mitigation programs of efficient blood supply management with cryopreserved blood and blood derived bioproducts.

Platelet Biochemistry and Morphology after Cryopreservation

Platelet cryopreservation has been investigated for several decades as an alternative to room temperature storage of platelet concentrates. The use of dimethylsulfoxide as a cryoprotectant has improved platelet storage and cryopreserved concentrates can be kept at −80 °C for two years. Cryopreserved platelets can serve as emergency backup to support stock crises or to disburden difficult logistic areas like rural or military regions. Cryopreservation significantly influences platelet morphology, decreases platelet activation and severely abrogates platelet aggregation. Recent data indicate that cryopreserved platelets have a procoagulant phenotype because thrombin and fibrin formation kicks in earlier compared to room temperature stored platelets. This happens both in static and hydrodynamic conditions. In a clinical setting, low 1-h post transfusion recoveries of cryopreserved platelets represent fast clearance from circulation which may be explained by changes to the platelet GPIbα receptor. Cryopreservation splits the concentrate in two platelet subpopulations depending on GPIbα expression levels. Further research is needed to unravel its physiological importance. Proving clinical efficacy of cryopreserved platelets is difficult because of the heterogeneity of indications and the ambiguity of outcome measures. The procoagulant character of cryopreserved platelets has increased interest for use in trauma stressing the need for double-blinded randomized clinical trials in actively bleeding patients.

The Lipid Composition of Platelets and the Impact of Storage: An Overview

Lipids and bioactive lipid mediators are essential for platelet function. The lipid profile of platelets is highly dynamic due to free exchange of lipids with the plasma, release of extracellular vesicles, and both enzymatic and nonenzymatic lipid conversion. The lipidome of platelets changes in response to activation to accommodate the functional requirements of platelets, particularly for maintenance of hemostasis. Furthermore, when stored at room temperature as a component for transfusion, the lipid profile of platelets is altered. Although there is a growing interest in alternate storage conditions, such as refrigeration and cryopreservation, few contemporary studies have examined the impact of these storage modes on the lipid profile. However, evidence exists that bioactive lipid mediators produced over the storage of blood products may have functional implications once these products are transfused. As such, there is a need to determine the changes occurring to the lipid profile of these products over storage. This review outlines the role of lipids in platelets and discusses the current state of lipidomics for studying platelet components for transfusion in an effort to highlight the necessity for additional transfusion-focused investigations.

A randomized, controlled pilot clinical trial of cryopreserved platelets for perioperative surgical bleeding: the CLIP-I trial (Editorial, p. 2759)

BACKGROUND

Cryopreservation extends platelet (PLT) shelf life from 5 to 7 days to 2 to 4 years. However, only 73 patients have been transfused cryopreserved PLTs in published randomized controlled trials (RCTs), making safety data insufficient for regulatory approval.

STUDY DESIGN AND METHODS

The Cryopreserved vs. Liquid Platelet (CLIP) study was a double-blind, pilot, multicenter RCT involving high-risk cardiothoracic surgical patients in four Australian hospitals. The objective was to test, as the primary outcome, the feasibility and safety of the protocol. Patients were allocated to study group by permuted block randomization, with patients and clinicians blinded by use of an opaque shroud placed over each study PLT unit. Up to 3 units of cryopreserved or liquid-stored PLTs were administered per patient. No other aspect of patient care was affected. Adverse events were actively sought.

RESULTS

A total of 121 patients were randomized, of whom 23 received cryopreserved PLTs and 18 received liquid-stored PLTs. There were no differences in blood loss (median, 715 mL vs. 805 mL at 24 hr; difference between groups 90 mL [95% CI, -343.8 to 163.8 mL], p = 0.41), but the Bleeding Academic Research Consortium criterion for significant postoperative hemorrhage in cardiac surgery composite bleeding endpoint occurred in nearly twice as many patients in the liquid-stored group (55.6% vs. 30.4%, p = 0.10). Red blood cell transfusion requirements were a median of 3 units in the cryopreserved group versus 4 units with liquid-stored PLTs (difference between groups, 1 unit [95% CI, -3.1 to 1.1 units]; p = 0.23). Patients in the cryopreserved group were more likely to be transfused fresh-frozen plasma (78.3% vs. 27.8%, p = 0.002) and received more study PLT units (median, 2 units vs. 1 unit; difference between groups, 1 unit [95% CI, -0.03 to 2.0 units]; p = 0.012). There were no between-group differences in potential harms including deep venous thrombosis, myocardial infarction, respiratory function, infection, and renal function. No patient had died at 28 days, and postoperative length of stay was similar in each group.

CONCLUSION

In this pilot RCT, compared to liquid-stored PLTs, cryopreserved PLTs were associated with no evidence of harm. A definitive study testing safety and hemostatic effectiveness is warranted.

Impact of cold storage on platelets treated with Intercept pathogen inactivation

BACKGROUND

Pathogen inactivation and cold or cryopreservation of platelets (PLTs) both significantly affect PLT function. It is not known how PLTs function when both are combined.

STUDY DESIGN AND METHODS

Standard PLT concentrates (PCs) were compared to pathogen‐inactivated PCs treated with amotosalen photochemical treatment (AS‐PCT) when stored at room (RT, 22°C), cold (4°C, n = 6), or cryopreservation (−80°C, n = 8) temperatures. The impact of alternative storage methods on both arms was studied in flow cytometry, light transmittance aggregometry, and hemostasis in collagen‐coated microfluidic flow chambers.

RESULTS

Platelet aggregation of cold‐stored AS‐PCT PLTs was 44% ± 11% compared to 57% ± 14% for cold‐stored standard PLTs and 58% ± 21% for RT‐stored AS‐PCT PLTs. Integrin activation of cold‐stored AS‐PCT PLTs was 53% ± 9% compared to 77% ± 6% for cold‐stored standard PLTs and 69% ± 13% for RT‐stored AS‐PCT PLTs. Coagulation of cold‐stored AS‐PCT PLTs started faster under flow (836 ± 140 sec) compared to cold‐stored standard PLTs (960 ± 192 sec) and RT‐stored AS‐PCT PLTs (1134 ± 220 sec). Fibrin formation rate under flow was also highest for cold‐stored AS‐PCT PLTs. This was in line with thrombin generation in static conditions because cold‐stored AS‐PCT PLTs generated 297 ± 47 nmol/L thrombin compared to 159 ± 33 nmol/L for cold‐stored standard PLTs and 83 ± 25 nmol/L for RT‐stored AS‐PCT PLTs. So despite decreased PLT activation and aggregation, cold storage of AS‐PCT PLTs promoted coagulation. PLT aggregation of cryopreserved AS‐PCT PLTs (23% ± 10%) was not significantly different from cryopreserved standard PLTs (25% ± 8%).

CONCLUSION

This study shows that cold storage of AS‐PCT PLTs further affects PLT activation and aggregation but promotes (pro)coagulation. Increased procoagulation was not observed after cryopreservation.

Transfusion of cryopreserved platelets exacerbates inflammatory liver and lung injury in a mice model of hemorrhage

BACKGROUND

Platelets are essential for primary hemostasis and also play an important role in inflammatory reactions. The hemostatic property of cryopreserved platelets (CPPs) has been confirmed in the treatment of bleeding casualties, but inflammatory injury induced by CPP transfusion is relatively unclear. We aim to investigate the effects of CPP transfusion on inflammatory organ injury in mice after hemorrhage.

METHODS

Mice were subjected to a volume-controlled hemorrhage over 1 hour, and then were transfused with fresh platelets (FPs), Liquid-stored platelets (LPPs), CPPs, or fresh frozen plasma (FFP, control). At 6 hours posttransfusion, mice were sacrificed, and blood and tissues were sampled. Tissue sections were examined histologically and by immunohistochemical staining of neutrophils and macrophages. Plasma alanine aminotransferase, hepatic myeloperoxidase activity and inflammatory cytokine levels were measured.

RESULTS

Transfusion of stored platelets (LPPs and CPPs) caused more serious histological injury in liver and lung compared with FPs and FFP (p < 0.05). However, kidney histological injury was similar among groups. Significantly higher numbers of Ly-6G-positive neutrophils were detected in liver and of F4/80-positive macrophages in liver and lung of mice transfused with LPPs or CPPs compared with FPs or FFP (p < 0.05). Transfusion of CPPs caused the most severe inflammatory liver injury, as reflected by alanine aminotransferase levels, hepatic macrophage infiltration, and hepatic myeloperoxidase activity and inflammatory cytokine levels (macrophage inflammatory protein-2, tumor necrosis factor-α, and interleukin-1β).

CONCLUSION

Cryopreserved platelet transfusion is more likely to aggravate hemorrhage-induced liver and lung injury by activating macrophage and facilitating neutrophil infiltration into hepatic tissues.

Transfusion strategies for major haemorrhage in trauma

Trauma is a leading cause of death worldwide in persons under 44 years of age, and uncontrolled haemorrhage is the most common preventable cause of death in this patient group. The transfusion management of trauma haemorrhage is unrecognisable from 20 years ago. Changes in clinical practice have been driven primarily by an increased understanding of the pathophysiology of trauma-induced coagulopathy (TIC), which is associated with poor clinical outcomes, including a 3- to 4-fold increased risk of death. Targeting this coagulopathy alongside changes to surgical and anaesthetic practices (an overarching strategy known as damage control surgery/damage control resuscitation) has led to a significant reduction in mortality rates over the last two decades. This narrative review will discuss the transfusion practices that are currently used for trauma haemorrhage and the evidence that supports these practices.

Towards increasing shelf life and haemostatic potency of stored platelet concentrates

PURPOSE OF REVIEW

Platelet transfusion is a widely used therapy in treating or preventing bleeding and haemorrhage in patients with thrombocytopenia or trauma. Compared with the relative ease of platelet transfusion, current practice for the storage of platelets is inefficient, costly and relatively unsafe, with platelets stored at room temperature (RT) for upto 5-7 days.

RECENT FINDINGS

During storage, especially at cold temperatures, platelets undergo progressive and deleterious changes, collectively termed the 'platelet storage lesion', which decrease their haemostatic function and posttransfusion survival. Recent progress in understanding platelet activation and host clearance mechanisms is leading to the consideration of both old and novel storage conditions that use refrigeration and/or cryopreservation to overcome various storage lesions and significantly extend platelet shelf-life with a reduced risk of pathogen contamination.

SUMMARY

A review of the advantages and disadvantages of alternative methods for platelet storage is presented from both a clinical and biological perspective. It is anticipated that future platelet preservation involving cold, frozen and/or pathogen reduction strategies in a proper platelet additive solution will enable longer term and safer platelet storage.

Cryopreservation of buffy coat-derived platelet concentrates photochemically treated with amotosalen and UVA light

BACKGROUND

Cryopreserved platelets (CPPs) are considered a promising approach for extended platelet storage, bridging inventory shortages of conventionally stored platelets. It is unknown if platelet concentrates exposed to photochemical treatment (PCT) with amotosalen and ultraviolet A (UVA) light, to inactivate pathogens, are suitable for freezing. The objective of this study was to analyze potential effects of PCT on CPPs as compared with untreated CPPs.

STUDY DESIGN AND METHODS

A total of 12 PCT-treated and 12 untreated platelet units from buffy coats were cryopreserved at -80°C in 5% dimethyl sulfoxide. CPPs of both types were rapidly thawed at 37°C and resuspended in 200 mL fresh plasma. In vitro properties were analyzed prefreezing, postfreezing and thawing, and on Day 1 after thawing.

RESULTS

Directly after thawing, no major differences in platelet content, lactase hydrogenase, adenosine triphosphate, mitochondrial membrane potential, CD62P, CD42b, and platelet endothelial cell adhesion molecule were seen between PCT-CPPs and conventional CPPs. Agonist-induced PAC-1 expression and contribution of CPPs to blood coagulation in an experimental rotational thromboelastometry setup were also similar between the groups. On Day 1 after thawing, the CPPs of both types performed less well. The PCT-CPPs tended to be more affected by the freezing process than the conventional CPPs.

CONCLUSIONS

PCT-CPPs appeared slightly more susceptible to lesion effects by freezing than conventional CPPs, in particular in assays on Day 1 after thawing, but these differences were small relative to the dramatic effects of the freezing process itself.

The contribution of the individual blood elements to the variability of thromboelastographic measures

BACKGROUND

Thromboelastography (TEG) is widely advocated as a rapid method for obtaining critical blood coagulation data to guide resuscitation, but the method suffers well-known limits in sensitivity, repeatability, and interpretability.

STUDY DESIGN AND METHODS

Mixtures of fresh human blood components were prepared that represent the range of blood element concentrations seen in health and disease and after injury. These mixtures were tested in a TEG device after kaolin, tissue factor and phospholipid, or tissue factor and phospholipid with abciximab activation. The results were measured as reproducibility and nonlinear effects in regression analysis and evaluated for interpretability.

RESULTS

Clot strength was associated with increased platelet (PLT) content and plasma fibrinogen concentration and content. Increasing hematocrit (Hct) reduced while increasing PLT or plasma concentration increased TEG clot strength. The abciximab dose used to block PLT activity did not fully inhibit the PLT contribution to clot strength. Clot strength is logarithmically correlated in the absence and linearly correlated to PLT concentration in the presence of abciximab. TEG clot strength with or without abciximab is dependent on Hct, PLT, and plasma (fibrinogen) concentrations in complex patterns.

CONCLUSION

Interpretation of TEG variables is limited without knowledge of the concentration of the blood components present. When "normal" TEG values are known for a certain PLT-plasma-red blood cell concentration, the assay can be used to assess PLT and plasma function in coagulation. The TEG "functional fibrinogen" assay should be used only as a gross estimate of the fibrinogen concentration in whole blood.

Buffy coat-derived platelets cryopreserved using a new method: Results from in vitro studies

Cryopreservation for the long-term storage of platelets (PLTs) is a useful method to overcome the limits of platelet shortage. This is an in vitro prospective study to evaluate the count, viability, and function of buffy coat-derived pooled platelet concentrates (BC-PLTs), treated with dimethyl sulphoxide (DMSO) and cryopreserved (CRY BC-PLTs) at -80 °C with a modified Valeri method. PLTs were stored in 6% DMSO with a patented kit. Overall, 49 BC-PLTs from 245 healthy volunteer donors were prepared, cryopreserved, and analysed before and after 3, 6, and 9 months of storage. In flow cytometry, a statistically significant reduction in CD 42b (92.7 ± 4.29% at T0 vs. 23.6 ± 27.5% at T3, 16.38 ± 12.54% at T6, and 17.3 ± 9.6% at T9) and PAC-1 (1.9 ± 1.34% at T0 vs. 0.62 ± 0.4% at T3, 0.63 ± 0.83% at T6, and 0.49 ± 0.48% at T9) was observed after storage. CRY BC-PLTs showed a good and stable endogenous thrombin generation potential (nM min): 529.25 ± 98.64 at T0 vs. 533.04 ± 103.15 at T9 months. CRY BC-PLTs showed a good viability in vitro, according to currently accepted criteria for cryopreserved PLTs.

Platelet Storage Lesions: What More Do We Know Now?

Platelet concentrate (PC) transfusions are a lifesaving adjunct to control and prevent bleeding in cancer, hematologic, surgical, and trauma patients. Platelet concentrate availability and safety are limited by the development of platelet storage lesions (PSLs) and risk of bacterial contamination. Platelet storage lesions are a series of biochemical, structural, and functional changes that occur from blood collection to transfusion. Understanding of PSLs is key for devising interventions that prolong PC shelf life to improve PC access and wastage. This article will review advancements in clinical and mechanistic PSL research. In brief, exposure to artificial surfaces and high centrifugation forces during PC preparation initiate PSLs by causing platelet activation, fragmentation, and biochemical release. During room temperature storage, enhanced glycolysis and reduced mitochondrial function lead to glucose depletion, lactate accumulation, and product acidification. Impaired adenosine triphosphate generation reduces platelet capacity to perform energetically demanding processes such as hypotonic stress responses and activation/aggregation. Storage-induced alterations in platelet surface proteins such as thrombin receptors and glycoproteins decrease platelet aggregation. During storage, there is an accumulation of immunoactive proteins such as leukocyte-derive cytokines (tumor necrosis factor α, interleukin (IL) 1α, IL-6, IL-8) and soluble CD40 ligand which can participate in transfusion-related acute lung injury and nonhemolytic transfusion reactions. Storage-induced microparticles have been linked to enhanced platelet aggregation and immune system modulation. Clinically, stored PCs have been correlated with reduced corrected count increment, posttransfusion platelet recovery, and survival across multiple meta-analyses. Fresh PC transfusions have been associated with superior platelet function in vivo; however, these differences were abrogated after a period of circulation. There is currently insufficient evidence to discern the effect of PSLs on transfusion safety. Various bag and storage media changes have been proposed to reduce glycolysis and platelet activation during room temperature storage. Moreover, cryopreservation and cold storage have been proposed as potential methods to prolong PC shelf life by reducing platelet metabolism and bacterial proliferation. However, further work is required to elucidate and manage the PSLs specific to these storage protocols before its implementation in blood banks.

Refrigeration, cryopreservation and pathogen inactivation: an updated perspective on platelet storage conditions

Conventional storage of platelet concentrates limits their shelf life to between 5 and 7 days due to the risk of bacterial proliferation and the development of the platelet storage lesion. Cold storage and cryopreservation of platelets may facilitate extension of the shelf life to weeks and years, and may also provide the benefit of being more haemostatically effective than conventionally stored platelets. Further, treatment of platelet concentrates with pathogen inactivation systems reduces bacterial contamination and provides a safeguard against the risk of emerging and re-emerging pathogens. While each of these alternative storage techniques is gaining traction individually, little work has been done to examine the effect of combining treatments in an effort to further improve product safety and minimize wastage. This review aims to discuss the benefits of alternative storage techniques and how they may be combined to alleviate the problems associated with conventional platelet storage.

Characterization of biologic response modifiers in the supernatant of conventional, refrigerated, and cryopreserved platelets

BACKGROUND

Alternatives to room temperature storage of platelets (PLTs) are of interest to support blood banking logistics. The aim of this study was to compare the presence of biologic response modifiers (BRMs) in PLT concentrates stored under conventional room temperature conditions with refrigerated or cryopreserved PLTs.

STUDY DESIGN AND METHODS

A three-arm pool-and-split study was carried out using buffy coat-derived PLTs stored in 30% plasma/70% SSP+. The three matched treatment arms were as follows: room temperature (20-24°C), cold (2-6°C), and cryopreserved (-80°C with DMSO). Liquid-stored PLTs were tested over a 21-day period, while cryopreserved PLTs were tested immediately after thawing and reconstitution in 30% plasma/70% SSP+ and after storage at room temperature.

RESULTS

Coagulation factor activity was comparable between room temperature and cold PLTs, with the exception of protein S, while cryopreserved PLTs had reduced Factor (F)V and FVIII activity. Cold-stored PLTs retained α-granule proteins better than room temperature or cryopreserved PLTs. Cryopreservation resulted in 10-fold higher microparticle generation than cold-stored PLTs, but both groups contained significantly more microparticles than those stored at room temperature. The supernatant from both cold and cryopreserved PLTs initiated faster clot formation and thrombin generation than room temperature PLTs.

CONCLUSION

Cold storage and cryopreservation alter the composition of the soluble fraction of stored PLTs. These differences in coagulation proteins, cytokines, and microparticles likely influence both the hemostatic capacity of the components and the auxiliary functions.

Immunomodulatory effect of cryopreserved platelets: altered BDCA3+ dendritic cell maturation and activation in vitro

BACKGROUND

Cryopreservation of platelets (PLTs) is useful in remote areas to overcome logistic problems associated with supply and can extend the shelf life to 2 years. During cryopreservation, properties of PLTs are modified. Whether changes in the cryopreserved PLT (CPP) product are associated with modulation of recipients' immune function is unknown. We aimed to characterize the immune profile of myeloid dendritic cells (mDCs) and the specialized blood DC antigen (BDCA)3⁺ subset after exposure to CPPs.

STUDY DESIGN AND METHODS

Using an in vitro whole blood model of transfusion, the effect of CPPs on mDC and BDCA3⁺ DC surface antigen expression and inflammatory mediator production was examined using flow cytometry. In parallel, polyinosinic:polycytidylic acid (poly(I:C)) or lipopolysaccharide (LPS) was utilized to model processes activated in viral or bacterial infection, respectively.

RESULTS

Cryopreserved PLTs had minimal impact on mDC responses but significantly modulated BDCA3⁺ DC responses in vitro. Exposure to CPPs alone up regulated BDCA3⁺ DC CD86 expression and suppressed interleukin (IL)-8, tumor necrosis factor (TNF)-α, and interferon-γ inducible protein (IP)-10 production. In both models of infection-related processes, exposure to CPPs down regulated BDCA3⁺ DC expression of CD40, CD80, and CD83 and suppressed BDCA3⁺ DC production of IL-8, IL-12, and TNF-α. CPPs suppressed CD86 expression in the presence of LPS and IP-10 and IL-6 production with poly(I:C).

CONCLUSION

Cryopreserved PLTs may be immunosuppressive, and this effect is more evident when processes associated with infection are concurrently activated, especially for BDCA3⁺ DCs. This suggests that transfusion of CPPs in patients with infection may result in impaired BDCA3⁺ DC responses.

Cryopreserved platelets demonstrate reduced activation responses and impaired signaling after agonist stimulation

BACKGROUND

Room temperature-stored (20-24°C) platelets (PLTs) have a shelf life of 5 days, making it logistically challenging to supply remote medical centers with PLT products. Cryopreservation of PLTs in dimethyl sulfoxide (DMSO) and storage at -80°C enables an extended shelf life up to 2 years. Although cryopreserved PLTs have been widely characterized under resting conditions, their ability to undergo agonist-induced activation is yet to be fully explored.

STUDY DESIGN AND METHODS

Buffy coat PLTs were cryopreserved at -80°C with 5% to 6% DMSO and sampled before freezing and after thawing. PLTs were analyzed under resting conditions and after agonist stimulation with adenosine diphosphate, collagen, or thrombin receptor-activating peptide-6. The expression of activation markers, microparticle formation, and calcium mobilization were analyzed by flow cytometry. Soluble PLT proteins present in the PLT supernatant were examined by enzyme-linked immunosorbent assay. Protein phosphorylation was investigated with Western blotting.

RESULTS

After cryopreservation, PLTs displayed increased surface activation markers and higher basal calcium levels. Cryopreserved PLTs demonstrated diminished aggregation responses. Additionally, cryopreserved PLTs showed a limited ability to become activated (as measured by CD62P and phosphatidylserine exposure and cytokine release) after agonist stimulation. A reduction in the abundance and phosphorylation of key signaling proteins (Akt, Src, Lyn, ERK, and p38) was seen in cryopreserved PLTs.

CONCLUSIONS

Cryopreservation of PLTs induces dramatic changes to the basal PLT phenotype and renders them largely nonresponsive to agonist stimulation, likely due to the alterations in signal transduction. Therefore, further efforts are required to understand how cryopreserved PLTs achieve their hemostatic effect once transfused.

Comprehensive review of platelet storage methods for use in the treatment of active hemorrhage

This review considers the various methods currently in use, or under investigation, for the storage of platelets intended for use in the treatment of active hemorrhage. The current standard practice of storing platelets at room temperature (RT) (20°C-24°C) optimizes circulating time, but at the expense of hemostatic function and logistical considerations. A number of alternatives are under investigation. Novel storage media additives appear to attenuate the deleterious changes that affect RT stored platelets. Cold storage was originally abandoned due to the poor circulating time of platelets stored at 4°C, but such platelets may actually be more hemostatically effective, with a number of other advantages, compared to RT stored platelets. Periodically re-warming cold stored platelets (temperature cycling, TC) may combine the hemostatic efficacy of cold stored platelets with the longer circulating times of RT storage. Alternatives to liquid storage include cryopreservation (freezing) or lyophilization (freeze-drying). The former has had some limited clinical use and larger clinical trials are underway, while the latter is still in the preclinical stage with promising in vitro and in vivo results. The importance of platelet transfusion in the management of active hemorrhage is now well accepted, so it is timely that platelet storage methods are reviewed with consideration of not only their circulating time, but also their hemostatic efficacy.

Quality Assessment of Established and Emerging Blood Components for Transfusion

Blood is donated either as whole blood, with subsequent component processing, or through the use of apheresis devices that extract one or more components and return the rest of the donation to the donor. Blood component therapy supplanted whole blood transfusion in industrialized countries in the middle of the twentieth century and remains the standard of care for the majority of patients receiving a transfusion. Traditionally, blood has been processed into three main blood products: red blood cell concentrates; platelet concentrates; and transfusable plasma. Ensuring that these products are of high quality and that they deliver their intended benefits to patients throughout their shelf-life is a complex task. Further complexity has been added with the development of products stored under nonstandard conditions or subjected to additional manufacturing steps (e.g., cryopreserved platelets, irradiated red cells, and lyophilized plasma). Here we review established and emerging methodologies for assessing blood product quality and address controversies and uncertainties in this thriving and active field of investigation.

Transfusion: -80°C Frozen Blood Products Are Safe and Effective in Military Casualty Care

INTRODUCTION

The Netherlands Armed Forces use -80°C frozen red blood cells (RBCs), plasma and platelets combined with regular liquid stored RBCs, for the treatment of (military) casualties in Medical Treatment Facilities abroad. Our objective was to assess and compare the use of -80°C frozen blood products in combination with the different transfusion protocols and their effect on the outcome of trauma casualties.

MATERIALS AND METHODS

Hemovigilance and combat casualties data from Afghanistan 2006-2010 for 272 (military) trauma casualties with or without massive transfusions (MT: ≥6 RBC/24hr, N = 82 and non-MT: 1-5 RBC/24hr, N = 190) were analyzed retrospectively. In November 2007, a massive transfusion protocol (MTP; 4:3:1 RBC:Plasma:Platelets) for ATLS® class III/IV hemorrhage was introduced in military theatre. Blood product use, injury severity and mortality were assessed pre- and post-introduction of the MTP. Data were compared to civilian and military trauma studies to assess effectiveness of the frozen blood products and MTP.

RESULTS

No ABO incompatible blood products were transfused and only 1 mild transfusion reaction was observed with 3,060 transfused products. In hospital mortality decreased post-MTP for MT patients from 44% to 14% (P = 0.005) and for non-MT patients from 12.7% to 5.9% (P = 0.139). Average 24-hour RBC, plasma and platelet ratios were comparable and accompanying 24-hour mortality rates were low compared to studies that used similar numbers of liquid stored (and on site donated) blood products.

CONCLUSION

This report describes for the first time that the combination of -80°C frozen platelets, plasma and red cells is safe and at least as effective as standard blood products in the treatment of (military) trauma casualties. Frozen blood can save the lives of casualties of armed conflict without the need for in-theatre blood collection. These results may also contribute to solutions for logistic problems in civilian blood supply in remote areas.

Alternatives to allogeneic platelet transfusion

Allogeneic platelet transfusions are widely used for the prevention and treatment of bleeding in thrombocytopenia. Recent evidence suggests platelet transfusions have limited efficacy and are associated with uncertain immunomodulatory risks and concerns about viral or bacterial transmission. Alternatives to transfusion are a well-recognised tenet of Patient Blood Management, but there has been less focus on different strategies to reduce bleeding risk by comparison to platelet transfusion. Direct alternatives to platelet transfusion include agents to stimulate endogenous platelet production (thrombopoietin mimetics), optimising platelet adhesion to endothelium by treating anaemia or increasing von Willebrand factor levels (desmopressin), increasing formation of cross-linked fibrinogen (activated recombinant factor VII, fibrinogen concentrate or recombinant factor XIII), decreasing fibrinolysis (tranexamic acid or epsilon aminocaproic acid) or using artificial or modified platelets (cryopreserved platelets, lyophilised platelets, haemostatic particles, liposomes, engineered nanoparticles or infusible platelet membranes). The evidence base to support the use of these alternatives is variable, but an area of active research. Much of the current randomised controlled trial focus is on evaluation of the use of thrombopoietin mimetics and anti-fibrinolytics. It is also recognised that one alternative strategy to platelet transfusion is choosing not to transfuse at all.

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

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