Cold-stored platelets have better preserved contractile function in comparison with room temperature-stored platelets over 21 days

Platelet ultrastructural changes stored at room temperature versus cold storage observed by electron microscopy and structured illumination microscopy

Our study seeks to provide a theoretical foundation for the clinical use of cold-stored platelets (CSPs) by interpreting ultrastructural images and quantitatively analyzing structural changes. CSPs, room temperature-stored platelets (RTPs), and delayed CSPs (delayed-CSPs) were continuously observed using scanning electron microscopy and transmission electron microscopy at eight time points. Super-resolution fluorescence microscopy was employed to observe changes in platelet microtubules and mitochondrial structure and function, whereas platelet counts, metabolism, and relevant functional indicators were measured concurrently. Quantitative statistical analysis of platelet size, morphology, canalicular systems, and five organelles was performed under electron microscopy. In CSPs stored for 1 day, the platelet shape changed from circular or elliptical to spherical, with size decreasing from 2.8 × 2.2 µm to 2.0 × 2.0 µm. CSPs exhibited wrinkling and reorganization of platelet microtubule proteins, with organelles aggregating toward the central region. CSPs stored for 14 days and delayed-CSPs for stored for 10 days exhibited numerous structurally intact and active cells. The percentage of structure-intact active cells was 92% in both groups, respectively. RTPs stored for 5 and 7 days showed minimal changes in size, a normal microtubule skeleton, and were primarily in a resting state. However, RTPs stored for 10 and 14 days displayed swelling, irregular disintegration of the microtubule skeleton, and the presence of membranous structures and vacuolated cells. The percentage of structure-intact active cells was only 45% and 7%, respectively. Our findings confirmed that the maximum storage time of platelets was 5-7 days for RTPs, within 10 days for delayed-CSPs, and 14 days for CSPs.

An Analysis of the Association of Whole Blood Transfusion With the Development of Acute Respiratory Distress Syndrome

OBJECTIVES

To determine the association of whole blood and other blood products (components, prothrombin complex concentrate, and fibrinogen concentrate) with the development of acute respiratory distress syndrome (ARDS) among blood recipients.

DESIGN

Retrospective cohort study.

SETTING

American College of Surgeons Trauma Quality Improvement Program (TQIP) database between 2020 and 2021.

PATIENTS

Patients 15 years old or older in the TQIP database between 2020 and 2022 who received at least one blood product.

INTERVENTIONS

We compared characteristics and blood product administration between patients who developed ARDS versus those who did not.

MEASUREMENTS AND MAIN RESULTS

There were 134,863 that met inclusion for this analysis. Within the included population, 1% (1927) was diagnosed with ARDS. The no ARDS group had a lower portion of serious injuries to the head/neck (31% vs. 46%), thorax (51% vs. 78%), abdomen (34% vs. 48%), and extremities (37% vs. 47%). The median composite Injury Severity Score was 21 (11-30) in the no ARDS group vs. 30 (22-41) in the ARDS group. Unadjusted survival of discharge was 74% in the no ARDS group vs. 61% in the ARDS group. In our multivariable model, we found that whole blood (unit odds ratio [uOR], 1.05; 95% CI, 1.02-1.07), male sex (odds ratio, 1.44; 95% CI, 1.28-1.63), arrival shock index (uOR, 1.03; 95% CI, 1.01-1.06), and composite Injury Severity Score (uOR, 1.03; 95% CI, 1.03-1.04) were associated with the development of ARDS. These persisted on sensitivity testing.

CONCLUSIONS

We found an association between whole blood and the development of ARDS among trauma patients who received blood transfusions. Contrary to previous studies, we found no association between ARDS and fresh frozen plasma administration. The literature would benefit from further investigation via prospective study designs.

A deep eutectic solvent is an effective cryoprotective agent for platelets

The most widely used method of platelet cryopreservation requires the addition of dimethyl sulfoxide (DMSO; Me2SO) as a cryoprotective agent (CPA) and pre-freeze removal of Me2SO before freezing to mitigate toxicity. However, alternative CPAs such as deep eutectic solvents (DES), which are less toxic could simplify this process. The aim of this study was to determine the effectiveness of a Proline-Glycerol (Prol-Gly 1:3) DES as a platelet CPA. Platelets were cryopreserved at -80 °C using 10 % Prol-Gly 1:3 (DES; n = 6), or in the absence of a cryoprotectant (no CPA; n = 6). Platelets were also cryopreserved according to the gold-standard blood-banking method using 5.5 % Me2SO (n = 6), with centrifugation and pre-freeze removal of the excess Me2SO. Platelet quality was assessed by flow cytometry and thromboelastography (TEG). Post-thaw recovery was similar between the three groups. The abundance of labile platelet glycoproteins GPIbα and GPVI were highest in the DES group, however, markers of activation (CD62P and annexin-V) were also higher in this group. In terms of function, the strength of the clot (maximum amplitude; TEG) and extent of clot retraction was better with DES platelets compared to no CPA, but lower than Me2SO platelets. DES provides a cryoprotective advantage to platelets when compared to no CPA. Importantly, when compared to Me2SO platelets, most quality parameters were similar in DES platelets. The major advantage with using a DES is biocompatibility, therefore it does not need to be removed prior to transfusion. This greatly simplifies the freezing and thawing process, avoiding the toxic effects of Me2SO.

Delayed cold-stored vs. room temperature stored platelet transfusions in bleeding adult cardiac surgery patients-a randomized multicentre pilot study (PLTS-1)

BACKGROUND

Platelets stored at 1-6 °C are hypothesized to be more hemostatically active than standard room temperature platelets (RTP) stored at 20-24 °C. Recent studies suggest converting RTP to cold-stored platelets (Delayed Cold-Stored Platelets, DCSP) may be an important way of extending platelet lifespan and increasing platelet supply while also activating and priming platelets for the treatment of acute bleeding. However, there is little clinical trial data supporting the efficacy and safety of DCSP compared to standard RTP.

METHODS

This protocol details the design of a multicentre, two-arm, parallel-group, randomized, active-control, blinded, internal pilot trial to be conducted at two cardiac surgery centers in Canada. The study will randomize 50 adult (≥ 18 years old) patients undergoing at least moderately complex cardiac surgery with cardiopulmonary bypass and requiring platelet transfusion to receive either RTP as per standard of care (control group) or DCSP (intervention group). Patients randomized to the intervention group will receive ABO-identical, buffy-coat, pathogen-reduced, platelets in platelet additive solution maintained at 22 °C for up to 4 days then placed at 4 °C for a minimum of 24 h, with expiration at 14 days after collection. The duration of the intervention is from the termination of cardiopulmonary bypass to 24 h after, with a maximum of two doses of DCSP. Thereafter, all patients will receive RTP. The aim of this pilot is to assess the feasibility of a future RCT comparing the hemostatic effectiveness of DCSP to RTP (defined as the total number of allogeneic blood products transfused within 24 h after CPB) as well as safety. Specifically, the feasibility objectives of this pilot study are to determine (1) recruitment of ≥ 15% eligible patients per center per month); (2) appropriate platelet product available for ≥ 90% of patients randomized to the cold-stored platelet group; (3) Adherence to randomization assignment (> 90% of patients administered assigned product).

DISCUSSION

DCSP represents a promising logistical solution to address platelet supply shortages and a potentially more efficacious option for the management of active bleeding. No prospective clinical studies on this topic have been conducted. This proposed internal pilot study will assess the feasibility of a larger definitive study.

TRIAL REGISTRATION

NCT06147531 (clinicaltrials.gov).

Preservation of recipient plasma sphingosine-1-phosphate levels reduces transfusion-related acute lung injury

Cold-stored (CS) platelets are once again being reintroduced for clinical use. Transfused CS platelets offer benefits over room temperature-stored (RTS) platelets such as increased hemostatic effects and prolongation of shelf-life. Despite these advantages little is known about their association with transfusion-related acute lung injury (TRALI). TRALI is associated with prolonged storage of RTS platelets and has a mortality of >15%. Determining the safety of CS platelets is important considering their proposed use in TRALI-vulnerable populations with inflammation such as surgical patients or patients with trauma. Donor platelet-derived ceramide causes TRALI, whereas donor platelet sphingosine-1-phosphate (S1P) is barrier protective. Females have higher plasma levels of S1P than males. Cold temperatures increase S1P levels in cells. Therefore, we hypothesized that female (donors or recipients) and/or CS platelets would decrease TRALI. To test this, we compared how male and female donor and recipient allogeneic platelet transfusions of CS (4°C) versus RTS (23°C) platelets stored for 5 days influence murine TRALI. Transfusion of CS platelets significantly reduced recipient lung tissue wet-to-dry ratios, bronchoalveolar lavage total protein, lung tissue myeloperoxidase enzyme activity, histological lung injury scores, and increased plasma sphingosine-1-phosphate (S1P) levels compared with RTS platelet transfusions. Female as opposed to male recipients had less TRALI and higher plasma S1P levels. Female donor mouse platelets had higher S1P levels than males. Mouse and human CS platelets had increased S1P levels compared with RTS platelets. Higher recipient plasma S1P levels appear protective considering females, and males receiving platelets from females or male CS platelets had less TRALI.NEW & NOTEWORTHY Transfusion-related acute lung injury (TRALI) though relatively rare represents a severe lung injury. The sphingolipid sphingosine-1-phosphate (S1P) regulates the severity of platelet-mediated TRALI. Female platelet transfusion recipient plasmas or stored platelets from female donors have higher S1P levels than males, which reduces TRALI. Cold storage of murine platelets preserves platelet-S1P, which reduces TRALI in platelet-transfused recipients.

Cold-stored platelet hemostatic capacity is maintained for three weeks of storage and associated with taurine metabolism

BACKGROUND

Platelet (PLT) product transfusion is a life-saving therapy for actively bleeding patients. There is an urgent need to maintain PLT function and extend shelf life to improve outcomes in these patients. Cold-stored PLT (CS-PLT) maintain hemostatic potential better than room temperature-stored PLT (RT-PLT). However, whether function in long-term CS-PLT is maintained under physiological flow regimes and/or determined by cold-induced metabolic changes is unknown.

OBJECTIVES

This study aimed to (i) compare the function of RT-PLT and CS-PLT under physiological flow conditions, (ii) determine whether CS-PLT maintain function after 3 weeks of storage, and (iii) identify metabolic pathways associated with the CS-PLT lesion.

METHODS

We performed phenotypic and functional assessments of RT- and CS-PLT (22 °C and 4 °C storage, respectively; N = 10 unique donors) at storage days 0, 5, and/or 21 via metabolomics, flow cytometry, aggregation, thrombin generation, viscoelastic testing, and a microfluidic assay to measure primary hemostatic function.

RESULTS

Day 21 4 °C PLT formed an occlusive thrombus under arterial shear at a similar rate to day 5 22 °C PLT. Day 21 4 °C PLTs had enhanced thrombin generation capacity compared with day 0 PLT and maintained functionality comparable to day RT-PLT across all assays performed. Key metrics from microfluidic assessment, flow cytometry, thrombin generation, and aggregation were associated with 4 °C storage, and metabolites involved in taurine and purine metabolism significantly correlated with these metrics. Taurine supplementation of PLT during storage improved hemostatic function under flow.

CONCLUSION

CS-PLT stored for 3 weeks maintain hemostatic activity, and storage-induced phenotype and function are associated with taurine and purine metabolism.

A novel, quantitative clot retraction assay to evaluate platelet function

Blood platelets are crucial to prevent excessive bleeding following injury to blood vessels. Platelets are crucial for the formation of clots and for clot strength. Platelet activation involves aggregation, attachment to fibrin and clot retraction. Most assays that address platelet function measure platelet aggregation, not clot retraction. Here, we describe a 96-well-based clot retraction assay that requires a relatively short runtime and small sample volume. The assay involves continuous optical density monitoring of platelet-rich plasma that is activated with thrombin. The data can be analyzed using time-series analytical tools to generate quantitative information about different phases of clot formation and clot retraction. The assay demonstrated good repeatability and reproducibility and was robust to different calcium concentrations. Impairment of platelet bioenergetics, actin polymerization, fibrin interaction, and signaling significantly affected clot retraction and was detected and showed good agreement with light transmission aggregometry, suggesting that clot retraction is predictive of platelet function. Using this microplate clot retraction assay, we showed a significant difference in platelets stored in autologous plasma compared with platelet additive solution after 7 days of room temperature storage.

Cold-stored platelets for acute bleeding in cardiac surgical patients: a narrative review

PURPOSE

Cold-stored platelets (CSP) are an increasingly active topic of international research. They are maintained at 1-6 °C, in contrast to standard room-temperature platelets (RTP) kept at 20-24 °C. Recent evidence suggests that CSP have superior hemostatic properties compared with RTP. This narrative review explores the application of CSP in adult cardiac surgery, summarizes the preclinical and clinical evidence for their use, and highlights recent research.

SOURCE

A targeted search of MEDLINE and other databases up to 24 February 2022 was conducted. Search terms combined concepts such as cardiac surgery, blood, platelet, and cold-stored. Searches of trial registries ClinicalTrials.gov and WHO International Clinical Trials Registry Platform were included. Articles were included if they described adult surgical patients as their population of interest and an association between CSP and clinical outcomes. References of included articles were hand searched.

PRINCIPAL FINDINGS

When platelets are stored at 1-6 °C, their metabolic rate is slowed, preserving hemostatic function for increased storage duration. Cold-stored platelets have superior adhesion characteristics under physiologic shear conditions, and similar or superior aggregation responses to physiologic agonists. Cold-stored platelets undergo structural, metabolic, and molecular changes which appear to "prime" them for hemostatic activity. While preliminary, clinical evidence supports the conduct of trials comparing CSP with RTP for patients with platelet-related bleeding, such as those undergoing cardiac surgery.

CONCLUSION

Cold-stored platelets may have several advantages over RTP, including increased hemostatic capacity, extended shelf-life, and reduced risk of bacterial contamination. Large clinical trials are needed to establish their potential role in the treatment of acutely bleeding patients.

Postoperative Transfusions after Administration of Delayed Cold-stored Platelets versus Room Temperature Platelets in Cardiac Surgery: A Retrospective Cohort Study

BACKGROUND

Delayed cold storage of room temperature platelets may extend shelf life from 5 to 14 days. The study hypothesized that the use of delayed cold-stored platelets in cardiac surgery would be associated with decreased postoperative platelet count increments but similar transfusion and clinical outcomes compared to room temperature-stored platelets.

METHODS

This is an observational cohort study of adults transfused with platelets intraoperatively during elective cardiac surgery between April 2020 and May 2021. Intraoperative platelets were either room temperature-stored or delayed cold-stored based on blood bank availability rather than clinical features or provider preference. Differences in transfusion and clinical outcomes, including a primary outcome of allogenic transfusion exposure in the first 24 h postoperatively, were compared between groups.

RESULTS

A total of 713 patient encounters were included: 529 (74%) room temperature-stored platelets and 184 (26%) delayed cold-stored platelets. Median (interquartile range) intraoperative platelet volumes were 1 (1 to 2) units in both groups. Patients receiving delayed cold-stored platelets had higher odds of allogeneic transfusion in the first 24 h postoperatively (81 of 184 [44%] vs. 169 of 529 [32%]; adjusted odds ratio, 1.65; 95% CI, 1.13 to 2.39; P = 0.009), including both erythrocytes (65 of 184 [35%] vs. 135 of 529 [26%]; adjusted odds ratio, 1.54; 95% CI, 1.03 to 2.29; P = 0.035) and platelets (48 of 184 [26%] vs. 79 of 529 [15%]; adjusted odds ratio, 1.91; 95% CI, 1.22 to 2.99; P = 0.005). There was no difference in the number of units administered postoperatively among those transfused. Platelet counts were modestly lower in the delayed cold-stored platelet group (-9 × 109/l; 95% CI, -16 to -3]) through the first 3 days postoperatively. There were no significant differences in reoperation for bleeding, postoperative chest tube output, or clinical outcomes.

CONCLUSIONS

In adults undergoing cardiac surgery, delayed cold-stored platelets were associated with higher postoperative transfusion utilization and lower platelet counts compared to room temperature-stored platelets without differences in clinical outcomes. The use of delayed cold-stored platelets in this setting may offer a viable alternative when facing critical platelet inventories but is not recommended as a primary transfusion approach.

EDITOR’S PERSPECTIVE

The Missing Pieces to the Cold-Stored Platelet Puzzle

Cold-stored platelets are making a comeback. They were abandoned in the late 1960s in favor of room-temperature stored platelets due to the need for longer post-transfusion platelet recoverability and survivability in patients with chronic thrombocytopenia. However, the current needs for platelet transfusions are rapidly changing. Today, more platelets are given to patients who are actively bleeding, such as ones receiving cardiac surgeries. It has been established that cold-stored platelets are more hemostatically effective, have reduced bacterial growth, and have longer potential shelf lives. These compelling characteristics led to the recent interest in bringing back cold-stored platelets to the blood systems. However, before reinstating cold-stored platelets in the clinics again, a thorough investigation of in vitro storage characteristics and in vivo transfusion effects is required. This review aims to provide an update on the recent research efforts into the storage characteristics and functions of cold-stored platelets using modern investigative tools. We will also discuss efforts made to improve cold-stored platelets to be a better and safer product. Finally, we will finish off with discussing the relevance of in vitro data to in vivo transfusion results and provide insights and directions for future investigations of cold-stored platelets.