Lyophilized platelets versus cryopreserved platelets for management of bleeding in thrombocytopenic dogs: A multicenter randomized clinical trial

Characterization of a canine freeze-dried platelet-derived hemostatic agent: A preclinical model for surgical and traumatic hemorrhage

INTRODUCTION

A freeze-dried, platelet-derived hemostatic agent (FPH) was developed for acute hemorrhage. The canine product (cFPH) was developed for use in preclinical models supporting human product (hFPH) investigations.

MATERIALS AND METHODS

A carotid artery bypass graft (CABG) study in dogs compared 3 dosages of cFPH to canine liquid stored platelets (cLSP) and vehicle (VEH) control groups. Histopathological analysis and blood loss assessments were completed. A separate ex-vivo synthetic graft study assessed thrombogenicity via blood from human and canine donors that was combined with species-specific FPH or apheresis platelets. Characterization of cFPH and hFPH included thrombin generation, total thrombus formation, and scanning electron microscopy.

RESULTS

Blood loss was reduced in CABG dogs receiving standard of care (cLSP) or cFPH treatment compared to VEH control; a cFPH dose effect signal was observed. Further, cFPH dosing up to 5 × 109 cells/kg was not associated with increased mortality or occlusion of the anastomosis sites, and histopathologic evidence of off-target thrombosis was not detected. When passed through a synthetic graft (ex vivo), whole blood combined with species-specific FPH did not result in thrombosis beyond that of whole blood control. In vitro testing and imaging of cFPH and FPH were comparable.

CONCLUSIONS

A single dose of cFPH or cLSP reduced blood loss in a pilot surgical study and was well tolerated with no related adverse events. Further, the hemostatic activity and characteristics of cFPH are comparable to that of hFPH, suggesting that research findings from the canine product are likely to inform the development of the human product.

Evaluation of activation characteristics of a canine platelet concentrate produced by a commercial double centrifugation system

Introduction

In veterinary medicine there are few readily available products for platelet transfusion to patients with thrombocytopenia. Commercial tabletop platelet concentrating systems have recently become available to veterinarians, primarily directed towards uses associated with regenerative medicine. These systems could potentially be used to produce fresh concentrated platelets for use in transfusion medicine. This study evaluated the concentration, activation, and sterility of a double centrifugation platelet concentrate (PC) produced by a commercial benchtop system.

Methods

Ten healthy dogs were studied. Whole blood was collected and mixed with ACD-A in a 1:7.6 ratio of ACD-A to whole blood. 12 mL of this mixture was processed into PC via single centrifugation, while 60 mL of the anticoagulated whole blood was processed via a commercial double centrifugation system. Both types of PC were evaluated for platelet concentration, CD62P expression with and without thrombin stimulation, and for sterility.

Results

Mean platelet count in the double centrifuged PC was 863 ± 352 × 103/μL, with very low white blood cell contamination (median of 0.47 × 103 leukocyte/μL (range 0.15-2.18 × 103/μL)). The double-centrifuged PC had similar baseline activation characteristics (as determined by P-selectin expression) as the single centrifuge PC (0.76% vs. 0.72% unstimulated, 30.5% vs. 34.9% stimulated, p = 0.432).

Discussion

The benchtop PC system studied here did not cause activation of platelets during production and produced a sterile product that can be further investigated as a source of fresh platelet concentrates for transfusion purposes.

ACVIM consensus statement on the treatment of immune thrombocytopenia in dogs and cats

Management of immune thrombocytopenia (ITP) in dogs and cats is evolving, but there are no evidence-based guidelines to assist clinicians with treatment decisions. Likewise, the overall goals for treatment of ITP have not been established. Immunosuppressive doses of glucocorticoids are the first line treatment, but optimal treatment regimens beyond glucocorticoids remain uncertain. Additional options include secondary immunosuppressive drugs such as azathioprine, modified cyclosporine, and mycophenolate mofetil, usually selected based on clinician preference. Vincristine, human IV immunoglobulin (hIVIg), and transfusion of platelet or red blood cell-containing products are often used in more severe cases. Splenectomy and thrombopoietin receptor agonists are usually reserved for refractory cases, but when and in which patient these modalities should be employed is under debate. To develop evidence-based guidelines for individualized treatment of ITP patients, we asked 20 Population Intervention Comparison Outcome (PICO) format questions. These were addressed by 17 evidence evaluators using a literature pool of 288 articles identified by a structured search strategy. Evidence evaluators, using panel-designed templates and data extraction tools, summarized evidence and created guideline recommendations. These were integrated by treatment domain chairs and then refined by iterative Delphi survey review to reach consensus on the final guidelines. In addition, 19 non-PICO questions covering scenarios in which evidence was lacking or of low quality were answered by expert opinion using iterative Delphi surveys with panelist integration and refinement. Commentary was solicited from multiple relevant professional organizations before finalizing the consensus. The rigorous consensus process identified few comparative treatment studies, highlighting many areas of ITP treatment requiring additional studies. This statement is a companion manuscript to the ACVIM Consensus Statement on the Diagnosis of Immune Thrombocytopenia in Dogs and Cats.

Mechanisms of action of an investigational new freeze-dried platelet-derived hemostatic product

BACKGROUND

A safe and efficacious hemostatic product with a long shelf-life is needed to reduce mortality from hemorrhage due to trauma and improve surgical outcomes for persons with platelet deficiency or dysfunction. Thrombosomes, a trehalose-stabilized, leukoreduced, pooled blood group-O freeze-dried platelet-derived hemostatic (FPH) with a 3-year shelf-life, may satisfy this need.

OBJECTIVES

To characterize the mechanism of action of FPH.

METHODS

FPH's ability to adhere to collagen, aggregate with and without platelets, and form clots was evaluated in vitro. Nonobese diabetic-severe combined immunodeficiency mouse models were used to assess circulation persistence and hemostatic efficacy.

RESULTS

FPH displays the morphology and surface proteins of activated platelets. FPH adheres to collagen, aggregates, and promotes clots, producing an insoluble fibrin mesh. FPH is rapidly cleared from circulation, has hemostatic efficacy comparable to apheresis platelets in a murine tail-cut, and acts in a dose-dependent manner.

CONCLUSION

FPH is a first-in-class investigational treatment and shows strong potential as a hemostatic agent that is capable of binding exposed collagen, coaggregating with endogenous platelets, and promoting the coagulation cascade. These properties may be exploited to treat active platelet-related or diffuse vascular bleeding. FPH has the potential to fulfill a large unmet patient need as an acute hemostatic treatment in severe bleeding, such as surgery and trauma.

Freeze-Dried Mesenchymal Stem Cells: From Bench to Bedside. Review

This review describes the freeze-dried mesenchymal stem cells (MSCs) and their ability to restore damaged tissues and organs. An analysis of the literature shows that after the lyophilization MSCs retain >80% of paracrine factors and that the mechanism of their action on the restoration of damaged tissues and organs is similar to the mechanism of action of paracrine factors in fresh and cryopreserved mesenchymal stem cells. Based on the own materials, the use of paracrine factors of freeze-dried MSCs in vivo and in vitro for the treatment of various diseases of organs and tissues has shown to be effective. The study also discusses about the advantages and disadvantages of freeze-dried MSCs versus cryopreserved MSCs. However, for the effective use of freeze-dried MSCs in clinical practice, a more detailed study of the mechanism of interaction of paracrine factors of freeze-dried MSCs with target cells and tissues is required. It is also necessary to identify possible other specific paracrine factors of freeze-dried MSCs. In addition, develop new therapeutic strategies for the use of freeze-dried MSCs in regenerative medicine and tissue bioengineering.

The Year in Coagulation and Transfusion: Selected Highlights from 2022

This is an annual review to cover highlights in transfusion and coagulation in patients undergoing cardiovascular surgery. The goal of this article is to provide readers with a focused summary of the most important transfusion and coagulation topics published in 2022. This includes a discussion covering the management of anemia and red blood cell transfusion, the management of factor Xa inhibitors, updates in coagulation testing, updates in the use of factor concentrates, advances in platelet therapy, advances in anticoagulation management of patients on extracorporeal membrane oxygenation and other forms of mechanical circulatory support, and advances in the diagnosis and management of heparin-induced thrombocytopenia.

Evaluation of platelet additive solution for prolonging storage of functional canine platelet concentrate

OBJECTIVE

To assess storage lesion development, platelet function, and bacterial growth in canine platelet concentrates (PCs) stored in a platelet additive solution (PAS) or a plasma control at 4°C for 21 days.

DESIGN

Prospective, ex vivo, experimental controlled study.

SETTING

University veterinary teaching hospital.

ANIMALS

Ten units of canine PCs collected from blood bank donations.

INTERVENTIONS

The PCs were separated into 2 bags, 1 containing 100% plasma and the other containing 35% plasma and 65% of a PAS (Plasma-Lyte A), and stored at 4°C for 21 days. At days 0, 7, 14, and 21, PCs were analyzed for the presence of swirling, aggregate formation, platelet counts, platelet indices, glucose, lactate, lactate dehydrogenase, Pvco2 , Pvo2 , aggregation via light aggregometry, activation percentages using flow cytometry, and bacterial growth.

MEASUREMENTS AND MAIN RESULTS

Cold-stored PCs in both PAS and plasma control maintained mean pH >6.8 and mean lactate <9.0 mmol/L over 21 days, with no difference in glucose utilization. Swirl was maintained in both solutions for most days (76/80 combined total samples), with no difference in aggregate formation between solutions. The Pvco2 was higher in plasma on all days (P < 0.001), with no difference in Pvo2 . Platelet indices did not reflect significant storage lesion development in either solution. Lactate dehydrogenase did not differ between solutions but did increase from day 7 to day 21. Mean maximal aggregation percentage was reduced overall but with no significant difference between solutions. The only observed difference in mean activation percentage between solutions was in PAS on day 7, which was significantly higher than plasma (P < 0.05). No bacterial growth occurred during storage.

CONCLUSIONS

Cold storage in PAS and plasma allowed PCs to be stored for up to 21 days with minimal storage lesion development, maintenance of platelet function, limited platelet activation, and no bacterial growth within stored bags.

The standards of reporting trials in pets (PetSORT): Explanation and elaboration

Well-designed randomized controlled trials (RCTs) provide the best evidence of the primary research designs for evaluating the effectiveness of interventions. However, if RCTs are incompletely reported, the methodological rigor with which they were conducted cannot be reliably evaluated and it may not be possible to replicate the intervention. Missing information also may limit the reader's ability to evaluate the external validity of a trial. Reporting guidelines are available for clinical trials in human healthcare (CONSORT), livestock populations (REFLECT), and preclinical experimental research involving animals (ARRIVE 2.0). The PetSORT guidelines complement these existing guidelines, providing recommendations for reporting controlled trials in pet dogs and cats. The rationale and scientific background are explained for each of the 25 items in the PetSORT reporting recommendations checklist, with examples from well-reported trials.

Dose-dependent effect of canine lyophilized platelet on an in vitro hemodilution model

The transfusion of stored platelets has emerged as an efficient method for treating dogs with thrombocytopenia. However, the availability of fresh platelets is limited in veterinary medicine due to demanding storage conditions. Lyophilized platelets have long shelf lives and can be easily stored, increasing their accessibility for thrombocytopenic dogs. Due to the lack of research and information on the dose effect, canine lyophilized platelets are used at a clinical dosage without research-based evidence. This study was to evaluate the dose effect of lyophilized canine platelets on blood coagulability. Three different concentrations of lyophilized canine platelets were added to in vitro hemodilution blood model, increasing the platelet count by 25, 50, and 100 × 10⁶/ml and coagulation profiles were analyzed. The coagulability was evaluated via the plasma fibrinogen concentration, coagulation time, thromboelastography (TEG), and platelet function analyzer (PFA). Higher concentrations of lyophilized platelets showed dose-dependent association with decreased aPTT and R-time of TEG and increased alpha angle and MA of TEG. These results showed the potential that the higher dose of canine lyophilized platelets better improve blood coagulability than the standard dose and provided the basis for further safety and clinical studies.

Prophylactic use of a lyophilized platelet product for rhinoscopic diagnosis and treatment of sinonasal aspergillosis in a dog with a P2Y12 platelet receptor mutation

OBJECTIVE

To describe the periprocedural use of a lyophilized platelet product during rhinoscopic diagnosis and treatment of sinonasal aspergillosis in a Greater Swiss Mountain Dog with a P2Y12 platelet receptor disorder.

CASE SUMMARY

After the development of severe epistaxis, a Greater Swiss Mountain Dog was diagnosed with thrombopathia secondary to a P2Y12 receptor gene mutation. Concurrent primary nasal disease was also suspected due to persistent mucopurulent nasal discharge. One month after the initial presentation for epistaxis, the dog was readmitted for workup of nasal disease. Computed tomography of the head showed turbinate lysis and regional lymphadenopathy. Because of concern for a high risk of bleeding in a thrombopathic patient subjected to rhinoscopy and nasal biopsies, a lyophilized platelet product was administered prior to the procedure. Rhinoscopic exam revealed fungal plaques consistent with Aspergillus spp. that were later confirmed on fungal culture to be Aspergillus fumigatus. Rhinoscopic biopsies were performed as well as debridement of the fungal plaques, followed by topical administration of clotrimazole solution. Bleeding was minimal during and after the procedure, and the dog recovered uneventfully.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first report of the prophylactic use of lyophilized platelets in a thrombopathic patient undergoing an invasive procedure with potential for significant hemorrhage. Minimal bleeding occurred during the procedure, suggesting that lyophilized platelets could be used for the prevention of bleeding in thrombopathic patients undergoing invasive procedures.

Retrospective evaluation of fresh platelet concentrate administration in dogs: Patient characteristics, outcomes, and transfusion practices in 189 transfusion episodes (2008-2019)

OBJECTIVE

To describe patient characteristics, underlying disease processes, clinical outcomes, transfusion dose and type (therapeutic or prophylactic), platelet count changes, and adverse events associated with platelet concentrate (PC) administration in dogs.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

A total of 149 dogs, representing 189 PC transfusion episodes.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In this population, 39 of 149 dogs (26.2%) were diagnosed with primary immune-mediated thrombocytopenia, 22 of 149 (14.8%) had decreased bone marrow production, 12 of 149 (8.0%) received PC during a massive transfusion, 3 of 149 (2.0%) had congenital thrombocytopathia, 59 of 149 (39.6%) had severe thrombocytopenia of other causes, and 14 of 149 (9.4%) underwent transfusion for miscellaneous causes without a documented severe thrombocytopenia. In 117 of 149 dogs (78.5%), >1 site of hemorrhage was noted. The most common sites of hemorrhage were the gastrointestinal (GI) tract in 89 of 149 (59.7%) and the skin in 78 of 149 (52.3%). Overall survival to discharge was 59.1% (88/149). The median PC dose was 0.8 units per 10 kg of body weight per transfusion episode (range: 0.2-6.7). Of 189 episodes, 29 of 189 (15.7%) were prophylactic, and 158 of 189 (83.6%) were therapeutic. For 99 of 189 transfusion episodes, paired pre- and postplatelet counts were available within 24 hours. The median platelet count change was 5.0 × 10⁹ /L (5000/μL; range: -115 × 10⁹ /L to 158 × 10⁹ /L [-115,000 to 158,000/μL]); the posttransfusion platelet count was significantly higher than pretransfusion (P < 0.0001). The increase in platelet count after transfusion was greater in the prophylactic group than the therapeutic group (P = 0.0167). Transfusion reactions were suspected during 2 of 168 episodes (1.2%).

CONCLUSIONS

Immune-mediated thrombocytopenia was the most common disease process that resulted in PC transfusion. PC was more frequently administered to animals with active hemorrhage rather than prophylactically, and most dogs had evidence of hemorrhage in multiple organ systems, particularly the GI tract and skin. PC transfusions typically appeared safe, and the median platelet count increased after transfusion.

Case report: Xenotransfusion of canine lyophilized platelets for hemostasis in a feline patient with post-operative abdominal hemorrhage

Objective

To describe the management of post-operative abdominal hemorrhage with a xenotransfusion of canine lyophilized platelets in a feline patient.

Case summary

A 9-year-old male castrated domestic shorthair presented for a spontaneous hemoabdomen secondary to hepatic amyloidosis. Clinically significant hemorrhage occurred in the perioperative and post-operative period and the patient received a massive transfusion and anti-fibrinolytic therapy in combination with a xenotransfusion of canine lyophilized platelets at 0.9 × 10⁹ particles/kg and recombinant human factor VIIa (rhFVIIa). The combination of these interventions decreased transfusion requirements in this patient and the xenotransfusion was well tolerated with no acute or immediate transfusion reactions noted.

New or unique information provided

This case report describes the xenotransfusion of canine lyophilized platelets in a feline patient with severe, non-compressible abdominal hemorrhage.

Freeze-dried platelets are a promising alternative in bleeding thrombocytopenic patients with hematological malignancies

Thrombosomes are trehalose-stabilized, freeze-dried group O platelets with a 3-year shelf life. They can be stockpiled, rapidly reconstituted, and infused regardless of the recipient's blood type. Thrombosomes thus represent a potential alternative platelet transfusion strategy. The present study assessed the safety and potential early signals of efficacy of Thrombosomes in bleeding thrombocytopenic patients. We performed an open-label, phase 1 study of single doses of allogeneic Thrombosomes at three dose levels in three cohorts, each consisting of eight patients who had hematologic malignancies, thrombocytopenia, and bleeding. Adverse events, dose-limiting toxicities (DLTs), World Health Organization (WHO) bleeding scores, and hematology values were assessed. No DLTs were reported. The median age was 59 years (24-71). Most patients had AML (58%) or ALL (29%), followed by MDS (8%) and myeloproliferative neoplasm (4%). The WHO scores of 22 patients who were actively bleeding at a total of 27 sites at baseline either improved (n = 17 [63%]) or stabilized (n = 10 [37%]) through day 6. Twenty-four hours after infusion, 12 patients (50%) had a clinically significant platelet count increase. Of eight patients who received no platelet transfusions for 6 days after Thrombosomes infusion, 5 had a clinically significant increase in platelet count of ≥5000 platelets/μL and 2 had platelet count normalization. Thrombosomes doses up to 3.78 × 10⁸ particles/kg demonstrated safety in 24 bleeding, thrombocytopenic patients with hematological malignancies. Thrombosomes may represent an alternative to conventional platelets to treat bleeding. A phase 2 clinical trial in a similar patient population is underway.

Lessons Learned From the Battlefield and Applicability to Veterinary Medicine - Part 2: Transfusion Advances

Since the inception of recent conflicts in Afghanistan and Iraq, transfusion practices in human military medicine have advanced considerably. Today, US military physicians recognize the need to replace the functionality of lost blood in traumatic hemorrhagic shock and whole blood is now the trauma resuscitation product of choice on the battlefield. Building on wartime experiences, military medicine is now one of the country's strongest advocates for the principle of hemostatic resuscitation using whole blood or balanced blood components as the primary means of resuscitation as early as possibly following severe trauma. Based on strong evidence to support this practice in human combat casualties and in civilian trauma care, military veterinarians strive to practice similar hemostatic resuscitation for injured Military Working Dogs. To this end, canine whole blood has become increasingly available in forward environments, and non-traditional storage options for canine blood and blood components are being explored for use in canine trauma. Blood products with improved shelf-life and ease of use are not only useful for military applications, but may also enable civilian general and specialty practices to more easily incorporate hemostatic resuscitation approaches to canine trauma care.

Fluids of the Future

Fluids are a vital tool in the armament of acute care clinicians in both civilian and military resuscitation. We now better understand complications from inappropriate resuscitation with currently available fluids; however, fluid resuscitation undeniably remains a life-saving intervention. Military research has driven the most significant advances in the field of fluid resuscitation and is currently leading the search for the fluids of the future. The veterinary community, much like our civilian human counterparts, should expect the fluid of the future to be the fruit of military research. The fluids of the future not only are expected to improve patient outcomes but also be field expedient. Those fluids should be compatible with military environments or natural disaster environments. For decades, military personnel and disaster responders have faced the peculiar demands of austere environments, prolonged field care, and delayed evacuation. Large scale natural disasters present field limitations often similar to those encountered in the battlefield. The fluids of the future should, therefore, have a long shelf-life, a small footprint, and be resistant to large temperature swings, for instance. Traumatic brain injury and hemorrhagic shock are the leading causes of preventable death for military casualties and a significant burden in civilian populations. The military and civilian health systems are focusing efforts on field-expedient fluids that will be specifically relevant for the management of those conditions. Fluids are expected to be compatible with blood products, increase oxygen-carrying capabilities, promote hemostasis, and be easy to administer in the prehospital setting, to match the broad spectrum of current acute care challenges, such as sepsis and severe systemic inflammation. This article will review historical military and civilian contributions to current resuscitation strategies, describe the expectations for the fluids of the future, and describe select ongoing research efforts with a review of current animal data.

Lyophilized platelets versus cryopreserved platelets for management of bleeding in thrombocytopenic dogs: A multicenter randomized clinical trial

Background

Thrombocytopenia in dogs is common in critical care medicine, but availability of fresh platelet concentrates in veterinary medicine can be limiting. Lyophilized platelets have long shelf‐lives and can be easily transported, stored, and administered in various settings.

Objective

To evaluate the efficacy and safety of a novel trehalose‐stabilized canine lyophilized platelet product in thrombocytopenic dogs with clinically‐evident bleeding.

Animals

Eighty‐eight dogs with platelet counts <50 × 10³/μL and a standardized bleeding assessment tool (DOGiBAT) score ≥2.

Methods

Multicenter, randomized, non‐blinded, non‐inferiority clinical trial comparing dimethyl sulfoxide (DMSO)‐stabilized cryopreserved platelet concentrates (CPP) with trehalose‐stabilized lyophilized platelets (LP) for control of bleeding in thrombocytopenic dogs. Dogs were randomized to receive 3 × 10⁹ platelets/kg of LP or CPP. Primary outcome measures were change in DOGiBAT score, platelet count, need for additional red cell transfusion and all‐cause mortality.

Results

Fifty dogs received LP and 38 received CPP. Baseline demographics and clinical characteristics of both groups were comparable. At 1‐hour post‐transfusion, LP were superior for change in DOGiBAT score, and non‐inferior at 24‐hours post‐transfusion. The LP were non‐inferior to CPP for change in platelet count, need for additional red blood cell units, and survival to discharge. The LP were superior for change in hematocrit at 1‐hour post‐transfusion, and non‐inferior at 24‐hours. No adverse effects were noted in either group.

Conclusions and Clinical Importance

A novel trehalose‐stabilized canine LP product appears to be logistically superior and is clinically non‐inferior to DMSO‐stabilized canine CPP for management of bleeding in thrombocytopenic dogs.