Platelet Transfusion Therapy

Objective indexes for comparing platelet usage among peer hospitals during the COVID-19 pandemic: A cross-sectional study

Background and Aims

Besides hospital size, clinical diagnosis and severity of patient cases determine the total platelet usage. Therefore, the appropriateness of platelet usage could not be compared simply with the total units of platelet usage in each hospital. This study aimed to objectively monitor and analyze platelet usage after implementing a single-unit issuing policy for each platelet transfusion in our hospital in October 2020.

Materials and Methods

We used three objective indices, X, Y, and Z, to monitor platelet usage and compared it with other hospitals. Three indices were generated by dividing the annual total units of platelet usage by the total annual reimbursement, total number of admissions, and average total reimbursement per admission for each hospital.

Results

The new indices X and Y alleviated hospital size-dependent differences. Index Y was preferred over X because its value fluctuated less during the COVID-19 pandemic. The Z index was adjusted for the average total reimbursement per admission, and the results showed that more patients with higher disease complexity did not have increased platelet usage during the COVID-19 pandemic. In our hospital (H1), index Z decreased from 2019 to 2021 due to a policy of issuing a single unit for each platelet transfusion.

Conclusion

These three objective indices are suitable for peer comparison and monitoring platelet usage in hospitals, irrespective of their size. They could be applied to promote patient blood management and provide an early response to the gradual shortage of blood resources owing to the aging population and declining birth rate in Taiwan.

Cold-stored platelets are effective in an in vitro model of massive transfusion protocol assessed by rotational thromboelastometry

BACKGROUND

Platelets are a key component of massive transfusion in treating actively bleeding patients. While optimized for prophylactic transfusions, the effectiveness of the current standard room temperature stored platelets (RPs) in treating actively bleeding patients is not clear. Cold-stored platelets (CPs) have been shown to have superior hemostatic functions and the potential to extend shelf life. In this study, we explored the effect of using CPs versus RPs in an in vitro transfusion model based on the massive transfusion protocol.

STUDY DESIGN AND METHODS

RPs or CPs were combined with RBCs and plasma in a 1:1:1 volume ratio to make transfusion packages. Whole blood was collected and then either diluted to 20% hematocrit or mixed with tPA (8.8 μg/ml). By volume, 70% of transfusion package was mixed with 30% whole blood to simulate massive transfusions and analyzed by rotational thromboelastometry. Transfusion package supernatant was analyzed for PAI-1 activity as well.

RESULTS

Both transfusion packages restored the clot characteristics of hemodiluted or hyperfibrinolytic whole blood. Specifically, only transfusion packages made with CPs significantly reduced the maximum clot lysis of hyperfibrinolytic whole blood. PAI-1 activity in CPs transfusion packages were also significantly higher.

DISCUSSION

Transfusion packages containing cold-stored platelets may be able to restore the blood hemostatic profile of bleeding patients. In addition, transfusion packages made from CPs may provide additional benefit of resisting hyperfibrinolysis in bleeding patients. In trauma where post-transfusion platelet recovery is less of a concern, CPs are a viable option to restore hemostasis.

Intrinsic apoptosis circumvents the functional decline of circulating platelets but does not cause the storage lesion

BAK/BAX depletion in murine platelets reveals that intrinsic apoptosis is not required for the development of the platelet storage lesion. Restriction of platelet life span by intrinsic apoptosis is pivotal to maintain a functional, hemostatically reactive platelet population.

The platelet Fc receptor, FcγRIIa

Human platelets express FcγRIIa, the low-affinity receptor for the constant fragment (Fc) of immunoglobulin (Ig) G that is also found on neutrophils, monocytes, and macrophages. Engagement of this receptor on platelets by immune complexes triggers intracellular signaling events that lead to platelet activation and aggregation. Importantly these events occur in vivo, particularly in response to pathological immune complexes, and engagement of this receptor on platelets has been causally linked to disease pathology. In this review, we will highlight some of the key features of this receptor in the context of the platelet surface, and examine the functions of platelet FcγRIIa in normal hemostasis and in response to injury and infection. This review will also highlight pathological consequences of engagement of this receptor in platelet-based autoimmune disorders. Finally, we present some new data investigating whether levels of the extracellular ligand-binding region of platelet glycoprotein VI which is rapidly shed upon engagement of platelet FcγRIIa by autoantibodies, can report on the presence of pathological anti-heparin/platelet factor 4 immune complexes and thus identify patients with pathological autoantibodies who are at the greatest risk of developing life-threatening thrombosis in the setting of heparin-induced thrombocytopenia.

Functional recovery of stored platelets after transfusion

BACKGROUND

Platelet (PLT) concentrates are prophylactically given to prevent major bleeding complications. The corrected count increment (CCI) is currently the only tool to monitor PLT transfusion efficacy. PLT function tests cannot be performed in patients with thrombocytopenia. Therefore, an optimized agonist-induced assay was used to determine PLT function, in patients with severe thrombocytopenia before and after transfusion.

STUDY DESIGN AND METHODS

PLT reactivity toward adenosine diphosphate (ADP), thrombin receptor-activating peptide SFLLRN (TRAP), and convulxin (CVX) was assessed by flow cytometry. P-selectin expression was measured on PLTs from 11 patients with thrombocytopenia before and 1 hour after transfusion, on stored PLTs, and on stored PLTs incubated for 1 hour in whole blood from patients ex vivo.

RESULTS

The mean (±SEM) CCI after 1 hour was 11.4 (±1.5). After transfusion, maximal agonist-induced PLT P-selectin expression was on average 29% higher for ADP (p = 0.02), 25% higher for TRAP (p = 0.007), and 24% higher for CVX (p = 0.0008). ADP-induced reactivity of stored PLTs increased with 46% after ex vivo incubation (p = 0.007). These PLTs also showed an overall higher P-selectin expression compared to PLTs 1 hour after transfusion (p = 0.005). After normalization for this background expression, a similar responsiveness was observed.

CONCLUSIONS

Our study shows recovery of PLT function after transfusion in patients with thrombocytopenia. The majority of functional PLTs measured after transfusion most likely represents stored transfused PLTs that regained functionality in vivo. The difference in baseline P-selectin expression in vivo versus ex vivo suggests a rapid clearance from circulation of PLTs with increased P-selectin expression.

Improving platelet transfusion safety: biomedical and technical considerations

Platelet concentrates account for near 10% of all labile blood components but are responsible for more than 25% of the reported adverse events. Besides factors related to patients themselves, who may be particularly at risk of side effects because of their underlying illness, there are aspects of platelet collection and storage that predispose to adverse events. Platelets for transfusion are strongly activated by collection through disposal equipment, which can stress the cells, and by preservation at 22 °C with rotation or rocking, which likewise leads to platelet activation, perhaps more so than storage at 4 °C. Lastly, platelets constitutively possess a very large number of bioactive components that may elicit pro-inflammatory reactions when infused into a patient. This review aims to describe approaches that may be crucial to minimising side effects while optimising safety and quality. We suggest that platelet transfusion is complex, in part because of the complexity of the "material" itself: platelets are highly versatile cells and the transfusion process adds a myriad of variables that present many challenges for preserving basal platelet function and preventing dysfunctional activation of the platelets. The review also presents information showing--after years of exhaustive haemovigilance--that whole blood buffy coat pooled platelet components are extremely safe compared to the gold standard (i.e. apheresis platelet components), both in terms of acquired infections and of immunological/inflammatory hazards.

Transfusion-induced alloimmunization and platelet refractoriness in a mouse model: mechanisms and interventions

BACKGROUND

Platelet (PLT) transfusions can be an essential therapy for patients with thrombocytopenia to maintain hemostasis. However, some patients become alloimmunized to antigens on PLTs (typically HLA), which can prevent efficacy of PLT transfusion due to antibody-mediated clearance. In extreme cases, patients with alloimmunization to multiple HLAs can become "refractory" to PLT transfusion, such that insufficient compatible PLT units can be found to meet transfusion needs.

MATERIALS AND METHODS

An in vivo murine model of PLT-induced alloimmunization was refined so as to include both transfusion with allogeneic leukoreduced PLTs and studies of posttransfusion PLT recoveries, allowing assessment of alloimmunization and refractoriness. Basic mechanisms of antibody-mediated PLT clearance were investigated using recipients missing either the C3 complement gene or the common gamma chain for Fc receptors. In addition, the efficacy of using costimulatory blockade as a therapeutic intervention was assessed by testing CTLA4-Ig administration before PLT transfusion.

RESULTS

Fcγ receptors (but not complement C3) are required for alloantibody-mediated PLT refractoriness. In addition, levels of anti-MHC predict the extent of refractoriness in a given animal. Finally, costimulatory blockade as a therapeutic modality prevents transfusion-induced PLT refractoriness.

CONCLUSIONS

Together these findings introduce new experimental methods, basic mechanistic understanding, and a potential therapeutic intervention for alloimmunization to MHC-based antigens on transfused PLTs.

Outcomes of Cancer Patients Undergoing Percutaneous Pericardiocentesis for Pericardial Effusion

BACKGROUND

Pericardial effusion (PE) is common in cancer patients, but the optimal therapeutic approach is not well defined. Percutaneous pericardiocentesis is less invasive than surgery, but its long-term effectiveness and safety have not been well documented.

OBJECTIVES

The goal of this study was to evaluate outcomes of cancer patients undergoing percutaneous pericardiocentesis for PE and assess the procedure's safety in patients with thrombocytopenia.

METHODS

Cancer patients who underwent percutaneous pericardiocentesis for PE between November 2009 and October 2014 at the MD Anderson Cancer Center were included. Procedure-related complications, effusion recurrence rate, and overall survival were analyzed.

RESULTS

Of 1,645 cancer patients referred for PE, 212 (13%) underwent percutaneous pericardiocentesis. The procedure was successful in 99% of the cases, and there were no procedure-related deaths. Four patients had major procedure-related bleeding that did not vary by platelet count <50,000/μl or ≥50,000/μl (p = 0.1281). Patients with catheter drainage for 3 to 5 days had the lowest recurrence rate (10%). Median overall survival was 143 days; older age (i.e., >65 years), lung cancer, platelet count <20,000/μl, and malignant pericardial fluid were independently associated with poor prognosis. Lung cancer patients with proven malignant effusions had a significantly shorter median 1-year survival compared with those with nonmalignant effusions (16.2% vs. 49.0%, respectively; log-rank test p = 0.0101). A similar difference in 1-year survival was not observed in patients with breast cancer (40.2% vs. 40.0%; log-rank test p = 0.4170).

CONCLUSIONS

Percutaneous pericardiocentesis with extended catheter drainage was safe and effective as the primary treatment for PE in cancer patients, including in those with thrombocytopenia. Malignant PE significantly shortened the survival outcome of patients with lung cancer but not those with breast cancer.

2-Arachidonoylglycerol enhances platelet formation from human megakaryoblasts

Platelets modulate vascular system integrity, and their loss is critical in haematological pathologies and after chemotherapy. Therefore, identification of molecules enhancing platelet production would be useful to counteract thrombocytopenia. We have previously shown that 2-arachidonoylglycerol (2-AG) acts as a true agonist of platelets, as well as it commits erythroid precursors toward the megakaryocytic lineage. Against this background, we sought to further interrogate the role of 2-AG in megakaryocyte/platelet physiology by investigating terminal differentiation, and subsequent thrombopoiesis. To this end, we used MEG-01 cells, a human megakaryoblastic cell line able to produce in vitro platelet-like particles. 2-AG increased the number of cells showing ruffled surface and enhanced surface expression of specific megakaryocyte/platelet surface antigens, typical hallmarks of terminal megakaryocytic differentiation and platelet production. Changes in cytoskeleton modeling also occurred in differentiated megakaryocytes and blebbing platelets. 2-AG acted by binding to CB1 and CB2 receptors, because specific antagonists reverted its effect. Platelets were split off from megakaryocytes and were functional: they contained the platelet-specific surface markers CD61 and CD49, whose levels increased following stimulation with a natural agonist like collagen. Given the importance of 2-AG for driving megakaryopoiesis and thrombopoiesis, not surprisingly we found that its hydrolytic enzymes were tightly controlled by classical inducers of megakaryocyte differentiation. In conclusion 2-AG, by triggering megakaryocyte maturation and platelet release, may have clinical efficacy to counteract thrombocytopenia-related diseases.

Comparative analysis of human ex vivo-generated platelets vs megakaryocyte-generated platelets in mice: a cautionary tale

Thrombopoiesis is the process by which megakaryocytes release platelets that circulate as uniform small, disc-shaped anucleate cytoplasmic fragments with critical roles in hemostasis and related biology. The exact mechanism of thrombopoiesis and the maturation pathways of platelets released into the circulation remain incompletely understood. We showed that ex vivo-generated murine megakaryocytes infused into mice release platelets within the pulmonary vasculature. Here we now show that infused human megakaryocytes also release platelets within the lungs of recipient mice. In addition, we observed a population of platelet-like particles (PLPs) in the infusate, which include platelets released during ex vivo growth conditions. By comparing these 2 platelet populations to human donor platelets, we found marked differences: platelets derived from infused megakaryocytes closely resembled infused donor platelets in morphology, size, and function. On the other hand, the PLP was a mixture of nonplatelet cellular fragments and nonuniform-sized, preactivated platelets mostly lacking surface CD42b that were rapidly cleared by macrophages. These data raise a cautionary note for the clinical use of human platelets released under standard ex vivo conditions. In contrast, human platelets released by intrapulmonary-entrapped megakaryocytes appear more physiologic in nature and nearly comparable to donor platelets for clinical application.

Thoracentesis and the risks for bleeding: a new era

PURPOSE OF REVIEW

Thoracentesis is a commonly performed procedure throughout the world. Convention dictates that patients should have laboratory values such as international normalized ratio (INR) and platelets corrected or medications that affect bleeding withheld prior to performing this procedure. By transfusing blood products or withholding medications, patients are exposed to risks that are different than but equally if not more significant than the risk of hemothorax from thoracentesis. This review highlights recent studies that suggest the parameters of performing thoracentesis should be less stringent than traditionally thought.

RECENT FINDINGS

Although the safety of thoracentesis has improved with the use of ultrasound and other advancements, the number of patients on new medications that exert an influence on bleeding and those who have physiologic coagulation abnormalities continues to grow. Despite a 1991 study demonstrating the safety of thoracentesis in patients with an abnormal INR or low platelet count, transfusion of blood products to normalize laboratory values is commonplace. A number of studies within the past year address the safety of thoracentesis amidst INR and platelet abnormalities and in patients taking antiplatelet or other medications that affect a patient's bleeding potential.

SUMMARY

Although large randomized studies do not exist, recent literature suggests that it is time to reevaluate the need to correct INR and platelet counts or to transfuse blood products or withhold medications prior to thoracentesis in patients felt to have a risk of possible bleeding.

Blood transfusion practices in cancer surgery

Cancer patients are commonly transfused with blood products immediately before, during or after major surgery. Blood loss and haemodilution are the most common causes of red blood cells (RBCs) administration and coagulopathies are the indications for the infusion of fresh-frozen plasma (FFP), cryoprecipitates and platelets. Transfusion-related immune modulation is a complication associated with the administration of blood products. A decreased immune surveillance as a consequence of blood transfusions has been linked to cancer recurrence and progression. Moreover, soluble factors present in packed RBCs, platelets and FFP can directly stimulate tumour growth and spread. Two meta-analyses suggest that the administration of blood products is associated with shorter recurrence-free survival and overall survival after colorectal cancer surgery. More studies are needed to show such association in different cancer patient populations.