Platelet Transfusion Therapy

Prophylactic versus restrictive platelet transfusion strategy in patients with haematological malignancies in the ICU setting, a propensity-score analysis

PURPOSE

Prophylactic platelet transfusions (PT) aim to reduce bleeding. We assessed whether restrictive PT compared to prophylactic strategy could apply in ICU.

MATERIAL AND METHODS

We conducted a retrospective monocentric study including patients >18 yo with haematological malignancy admitted to the ICU with thrombocytopenia <20 G/L between 2018 and 2021. Patients were classified in 2 groups according transfusion strategy applied during the first 3 days: prophylactic or restrictive transfusion.

RESULTS

180 patients were included, 87 and 93 in the restrictive and prophylactic groups respectively. After propensity-score analysis, 2 groups of 54 matched patients were analyzed. Restrictive strategy led to a significant reduction in PT with incidence rate for 100-ICU-patients-days of 34.9 and 49.9, incidence rate ratio = 0.699 [0.5-0.9], p = 0.006, representing a 31% decrease. Decreased PT persisted until day 28 with platelet concentrates transfusions-free days at day 28 of 21 [13-25] and 16.5 [10.2-21] in the 2 groups (p = 0.04). Restrictive strategy did not result in higher grade ≥ 2 bleeding. Transfusion efficiency was low with similar number of days with platelet <10 or < 20 G/L regardless of strategy. Platelet transfusion strategy was not associated with 28-day mortality. Platelet nadir <5G/L was associated with day-28 mortality with HR = 1.882 [1.011-3.055], p = 0.046.

CONCLUSION

A restrictive PT strategy appears feasible in the ICU.

Effect of double dose plateletpheresis on target yield and donor platelet recovery

INTRODUCTION

The demand for apheresis platelets has increased in the recent past and the shrinking donor pool has shifted the trend to collection of double-dose or higher yield of platelets.

OBJECTIVE

The present study aimed to determine the effect of double-dose plateletpheresis on the target yield and donor platelet recovery.

METHODS

The study was conducted on 100 healthy plateletpheresis donors, 50 of whom were in the study group, which underwent double-dose plateletpheresis (DDP), and 50 of whom were in the control group for single-donor plateletpheresis. Pre- and post-procedure samples of donors were subjected to a complete blood count. The DDP product was sampled for platelet yield and then split into two parts. Platelet yield, collection efficiency, collection rate, recruitment factor and donor platelet loss were calculated.

RESULTS

The mean platelet yield in the SDP was 4.09 ± 1.15 × 10¹¹ and in the DDP, 5.93 ± 1.04 × 10¹¹. There was a significant correlation between the pre-donation platelet count and platelet yield. The total of platelets processed for the SDP were 5.42 ± 1.08 × 10¹¹ and for the DDP, 7.94 ± 0.77 × 10¹¹. The collection efficiency was 71.93 ± 25.14% in the SDP and 72.94 ± 16.28% in the DDP, while the collection rates were 0.78 × 10¹¹ and 0.94 × 10¹¹ per minute, respectively. The average recruitment factor observed was 0.98 in the SDP, while it was 0.99 in the DDP. The mean platelet loss observed in the SDP was 35.55 ± 8.53% and in the DDP, 37.76 ± 8.65%.

CONCLUSION

The double-dose plateletpheresis supplements the platelet inventory in developing countries where the apheresis donor pool is limited. It is prudent to ensure stringent donor selection criteria for donors donating high-yield platelet products, thus enhancing donor safety and retention.

Efficacy of anti-thymocyte globulin for platelet transfusion refractoriness in serious aplastic anemia patients

Platelet transfusion refractoriness (PTR) is a life threatening, intractable clinical issue suffered by some serious aplastic anemia (SAA) patients. Unlike immune thrombocytopenia, effective treatments for PTR remain largely unknown. In our clinical work, we noted that PTR in some SAA patients could be rapidly relieved with the application of anti-thymocyte globulin (ATG), therefore, we retrospectively analyzed its management and outcomes for PTR in SAA patients. A cohort including 29 SAA with PTR patients who received ATG administration was enrolled in this study. All patients suffered from PTR before ATG administration. Among the 29 PTR patients treated with ATG, 21 (72.4.0 %) patients had response, importantly, 13 (44.8 %) patients had an immediately response following the first dose of ATG administration. Bleeding events of grade 3 or above occurred in 23 patients (79.3 %). With the recovery of effective platelet transfusion, the bleeding events in responders could be quickly relieved. The non-responders suffered from aggravated bleeding, including intracranial bleeding in two non-responders, which appeared on eighth and 29th days after ATG administration. Our study indicated that ATG was an effective and safe intervention in the management of PTR in SAA patients.

Irradiation of platelets in Transfusion Medicine: risk and benefit judgments

Irradiation of platelet products is generally used to prevent transfusion-associated graft-versus-host disease (TA-GvHD) as well as transfusion-transmitted infections. As an essential prerequisite, gamma-irradiation of blood products prior to transfusion is required in patients who may develop TA-GVHD. Most studies suggest that gamma irradiation has no significant effect on the quality of platelet products; however, more recent studies have shown that the oxidative effects of gamma irradiation can lead to the induction of platelet storage lesion (PSL) and to some extent reduce the efficiency of transfused platelets. As the second widely used irradiation technique, UV-illumination was primarily introduced to reduce the growth of infectious agents during platelet storage, with the advantage that this method can also prevent TA-GvHD. However, the induction of oxidative conditions and platelet pre-activation that lead to PSL is more pronounced after UV-based methods of pathogen reduction. Since these lesions are large enough to clearly affect the post-transfusion platelet recovery and survival, more studies are needed to improve the safety and effectiveness of pathogen reduction technologies (PRTs). Therefore, pointing to other benefits of PRTs, such as preventing TA-GvHD or prolonging the shelf life of products by eliminating the possibility of pathogen growth during storage, does not yet seem to justify their widespread use due to above-mentioned effects. Even for gamma-irradiated platelets, some researchers have suggested that due to decreased 1-hour post-transfusion increments and increased risk of platelet refractoriness, their use should be limited to the patients who may develop TA-GVHD. It is noteworthy that due to the effect of X-rays in preventing TA-GvHD, some recent studies are underway to examine its effects on the quality and effectiveness of platelet products and determine whether X-rays can be used as a more appropriate and cost-effective alternative to gamma radiation. The review presented here provides a detailed description about irradiation-based technologies for platelet products, including their applications, mechanistic features, advantages, and disadvantages.

On the Quest for In Vitro Platelet Production by Re-Tailoring the Concepts of Megakaryocyte Differentiation

The demand of platelet transfusions is steadily growing worldwide, inter-donor variation, donor dependency, or storability/viability being the main contributing factors to the current global, donor-dependent platelet concentrate shortage concern. In vitro platelet production has been proposed as a plausible alternative to cover, at least partially, the increasing demand. However, in practice, such a logical production strategy does not lack complexity, and hence, efforts are focused internationally on developing large scale industrial methods and technologies to provide efficient, viable, and functional platelet production. This would allow obtaining not only sufficient numbers of platelets but also functional ones fit for all clinical purposes and civil scenarios. In this review, we cover the evolution around the in vitro culture and differentiation of megakaryocytes into platelets, the progress made thus far to bring the culture concept from basic research towards good manufacturing practices certified production, and subsequent clinical trial studies. However, little is known about how these in vitro products should be stored or whether any safety measure should be implemented (e.g., pathogen reduction technology), as well as their quality assessment (how to isolate platelets from the rest of the culture cells, debris, microvesicles, or what their molecular and functional profile is). Importantly, we highlight how the scientific community has overcome the old dogmas and how the new perspectives influence the future of platelet-based therapy for transfusion purposes.

The effect of gamma irradiation on platelet redox state during storage

BACKGROUND

As a method with insignificant adverse effects on in vitro quality of platelet concentrates (PCs), gamma irradiation is applied to abrogate the risk of transfusion-associated graft-vs-host disease in vulnerable recipients. However, there is some evidence of lower posttransfusion responses and proteomic alterations in gamma-irradiated platelets (PLTs), which raises some questions about their quality, safety, and efficacy. Since reactive oxygen species (ROS) are considered as markers of PLT storage lesion (PSL), the study presented here investigated oxidant state in gamma-irradiated PCs.

STUDY DESIGN AND METHODS

PLT-rich plasma PC was split into two bags, one kept as control while other was subjected to gamma irradiation. Within 7 days of storage, the levels of intra-PLT superoxide, H₂ O₂ , mitochondrial ROS, P-selectin expression, and phosphatidylserine (PS) exposure were detected by flow cytometry while intracellular reduced glutathione (GSH), glucose concentration, and lactate dehydrogenase (LDH) activity were measured by enzymocolorimetric method.

RESULTS

GSH decreased, while ROS generation and LDH activity increased, during storage. Gamma irradiation significantly attenuated GSH whereas increased ROS generation in earlier and later stages of storage associated with either P-selectin or PS exposure increments.

CONCLUSION

Gamma irradiation can significantly increase cytosolic ROS generation in two distinct phases, one upon irradiation and another later in longer-stored PCs. While earlier ROS influx seems to be governed by direct effect of irradiation, the second phase of oxidant stress is presumably due to the storage-dependent PLT activation. Intriguingly, these observations were also in line with early P-selectin increments and increased PS exposure in longer-stored PLTs. Given the mutual link between ROS generation and PLT activation, further investigation is required to explore the effect of gamma irradiation on the induction of PSL.

Donor platelet and leukocyte count as predictive factors of the quality of platelet concentrates obtained from whole blood by semiautomated fractionation

Platelet concentrates (PCs) obtained from whole blood are produced by fractionation of the buffy coat (BC) or the platelet-rich plasma. Despite the improvements in the technologies used for the hemocomponent fractionation, the proportion of PCs that do not accomplish the quality requirements is high. This study aimed to determine whether the basal platelet and leukocyte counts are predictive factors of the quality of the PCs obtained from BC by semiautomated fractionation. Quality control registers of 196 PCs were analyzed. Gender- and age-dependence of the blood cell count and the characteristics of PCs were evaluated. Platelet yield and residual leukocytes in the PCs were correlated with the platelet and leukocyte counts and the age of the donors. Predictive efficacy was assessed, and an optimal cut-off was established. The proportions of PCs accepted and rejected by using or not the optimal cut-off were compared. 50.0% of the PCs accomplished all the quality control requirements. Female donors had a higher basal platelet count than males. A correlation was observed between basal platelets and platelet yield, but not between basal leukocytes and residual leukocytes. The basal platelet count predicted the quality of the PCs. A cut-off of 231,000 platelets/mm³ was established, but it did not improve the proportion of accepted PCs. In conclusion, we found that the basal platelet count is correlated with the platelet yield. The basal leukocyte count is not correlated with the residual leukocytes. The established cut-off for the basal platelet count did not improve the proportion of accepted PCs.

A polymer-based systemic hemostatic agent

Uncontrolled noncompressible hemorrhage is a major cause of mortality following traumatic injuries in civilian and military populations. An injectable hemostat for point-of-care treatment of noncompressible hemorrhage represents an urgent medical need. Here, we describe an injectable hemostatic agent via polymer peptide interfusion (HAPPI), a hyaluronic acid conjugate with a collagen-binding peptide and a von Willebrand factor-binding peptide. HAPPI exhibited selective binding to activated platelets and promoted their accumulation at the wound site in vitro. In vivo studies in mouse tail vein laceration model demonstrated a reduction of >97% in both bleeding time and blood loss. A 284% improvement in the survival time was observed in the rat inferior vena cava traumatic model. Lyophilized HAPPI could be stably stored at room temperature for several months and reconstituted during therapeutic intervention. HAPPI provides a potentially clinically translatable intravenous hemostat.

Immune Thrombocytopenic Purpura in Pregnancy

Importance

Immune thrombocytopenia purpura (ITP), an autoimmune disease characterized by destruction of platelets, is a hematological disorder that can present in both pregnant and nonpregnant patients. Although thrombocytopenia in pregnancy can be caused by more common pathologies such as gestational thrombocytopenia and preeclampsia, ITP can present initially during pregnancy, further complicating diagnosis. Management must be considerate of both the pregnancy itself and the fetus.

Objective

Review the diagnosis, treatment, and management of ITP in pregnancy based on current recommendations.

Evidence Acquisition

Review articles, original research, and case studies were utilized.

Results

Throughout pregnancy, patients are screened for a variety of conditions or disorders of pregnancy. Thrombocytopenia is a common pathology of pregnancy, but ITP is a rare condition that a provider needs to be aware of. After ruling out secondary causes of thrombocytopenia or more common causes such as gestational thrombocytopenia or preeclampsia, ITP should be considered. After diagnosis, treatment options should be discussed and initiated to provide safety for both the mother and fetus.

Conclusions

After reading this article, the reader will understand the current recommendations regarding the diagnosis, treatment, and management of ITP in pregnancy.

Relevance

The practitioner will be comfortable treating this condition during pregnancy.

Real-Time Ultrasound-Guided Paracentesis by Radiologists: Near Zero Risk of Hemorrhage without Correction of Coagulopathy

PURPOSE

To evaluate the rate and risk factors for hemorrhage in patients undergoing real-time, ultrasound-guided paracentesis by radiologists without correction of coagulopathy.

MATERIALS AND METHODS

This was a retrospective study of all patients who underwent real-time, ultrasound-guided paracentesis at a single institution over a 2-year period. In total, 3116 paracentesis procedures were performed: 757 (24%) inpatients and 2,359 (76%) outpatients. Ninety-five percent of patients had a diagnosis of cirrhosis. Mean patient age was 56.6 years. Mean international normalized ratio (INR) was 1.6; INR was > 2 in 437 (14%) of cases. Mean platelet count was 122 x 10³/μL; platelet count was < 50 x 10³/μL in 368 (12%) of patients. Seven hundred seven (23%) patients were dialysis dependent. Patients were followed for 2 weeks after paracentesis to assess for hemorrhage requiring transfusion or rescue angiogram/embolization. Univariate analysis was performed to determine risk factors for hemorrhage. Blood product and cost saving analysis were performed.

RESULTS

Significant post-paracentesis hemorrhage occurred in 6 (0.19%) patients, and only 1 patient required an angiogram with embolization. No predictors of post-procedure bleeding were found, including INR and platelet count. Transfusion of 1125 units of fresh frozen plasma and 366 units of platelets were avoided, for a transfusion-associated cost savings of $816,000.

CONCLUSIONS

Without correction of coagulation abnormalities with prophylactic blood product transfusion, post-procedural hemorrhage is very rare when paracentesis is performed with real-time ultrasound guidance by radiologists.

Applicability of an instrument to identify human leukocyte antigen-compatible donors for platelet transfusions

Background

The selection of compatible human leukocyte antigen platelets has been associated with improved platelet increments. Therefore, an effective strategy would be the selection of donors who are genetically compatible according to the human leukocyte antigen system. Nonetheless, this is costly as it concerns a highly polymorphic system, which requires a large bank of genotyped donors.

Methods

This study evaluated the feasibility of virtual crossmatching using EpVix software, which simplifies the identification of compatible donors or donors with acceptable incompatibilities.

Results

Forty-three oncohematological patients were evaluated, in 96 platelet transfusion episodes with 16.3% of the patients being found to be refractory to platelet transfusions. Eight alloimmunized, multitransfused patients were selected to evaluate human leukocyte antigen compatibility against a bank of 336 platelet donors. At least partially compatible donors were found for all patients. The number of compatible donors was found to be inversely proportional to the human leukocyte antigen-panel reactive antibody score of each patient. It was noted that five patients with scores of 15% or less had at least 190 compatible donors; four fully compatible donors were found for two other patients with scores greater than 80% and only one patient (score of 93%) did not have a fully compatible donor. However, for this last patient, 40 donors were partially compatible according to the software.

Conclusion

The results showed the effectiveness of the use of the EpVix tool to identify potential platelet donors for multitransfused and/or alloimmunized patients, even with a small number of human leukocyte antigen genotyped donors available.

The role of thromboelastography in predicting hemorrhage risk in patients with leukemia

This study aimed to compare the efficacy of thromboelastography (TEG) and conventional coagulation methods in predicting hemorrhage risk in patients with leukemia.A total of 226 patients diagnosed with leukemia were included and divided into bleeding and nonbleeding groups. All patients had their blood samples taken for TEG test to measure the reaction time (R time), alpha (α angle), and maximum amplitude (MA) as well as measure platelet count (PLT), prothrombin time, and activated partial thromboplastin time. Patients were followed up for bleeding episodes.The multivariate analysis showed that PLT [odds ratio (OR) = 0.993] and MA (OR = 0.921) have better association with bleeding risk. Receiver operating characteristic (ROC) analysis showed that the combination of PLT and MA (AUC = 0.824) was better for hemorrhage risk prediction than PLT [area under the curve (AUC) = 0.730] and MA (AUC = 0.819) alone.The combination of TEG and conventional coagulation methods could help in assessing the risk of hemorrhage in patients with leukemia.

Resveratrol preserves the function of human platelets stored for transfusion

Stored platelets undergo biochemical, structural and functional changes that lead to decreased efficacy and safety of platelet transfusions. Not only do platelets acquire markers of activation during storage, but they also fail to respond normally to agonists post-storage. We hypothesized that resveratrol, a cardioprotective antioxidant, could act as a novel platelet storage additive to safely prevent unwanted platelet activation during storage, while simultaneously preserving normal haemostatic function. Human platelets treated with resveratrol and stored for 5 d released less thromboxane B2 and prostaglandin E2 compared to control platelets. Resveratrol preserved the ability of platelets to aggregate, spread and respond to thrombin, suggesting an improved ability to activate post-storage. Utilizing an in vitro model of transfusion and thromboelastography, clot strength was improved with resveratrol treatment compared to conventionally stored platelets. The mechanism of resveratrol's beneficial actions on stored platelets was partly mediated through decreased platelet apoptosis in storage, resulting in a longer half-life following transfusion. Lastly, an in vivo mouse model of transfusion demonstrated that stored platelets are prothrombotic and that resveratrol delayed vessel occlusion time to a level similar to transfusion with fresh platelets. We show resveratrol has a dual ability to reduce unwanted platelet activation during storage, while preserving critical haemostatic function.

Platelet refractoriness--practical approaches and ongoing dilemmas in patient management

Platelet refractoriness can represent a significant clinical problem that complicates the provision of platelet transfusions, is associated with adverse clinical outcomes and increases health care costs. Although it is most frequently due to non-immune platelet consumption, immunological factors are also often involved. Human leucocyte antigen (HLA) alloimmunization is the most important immune cause. Despite the fact that systematic reviews of the clinical studies evaluating different techniques for selecting HLA compatible platelets have not been powered to demonstrate improved clinical outcomes, platelet refractoriness is currently managed by the provision of HLA-matched or cross matched platelets. This review will address a practical approach to the diagnosis and management of platelet refractoriness while highlighting on-going dilemmas and knowledge gaps.

Road blocks in making platelets for transfusion

The production of laboratory-generated human platelets is necessary to meet present and future transfusion needs. This manuscript will identify and define the major roadblocks that must be overcome to make human platelet production possible for clinical use, and propose solutions necessary to accelerate development of laboratory-generated human platelets to market.

Transfusion of Blood and Blood Products

In transfusion medicine, several blood products can be prepared and used as replacement therapy; however, four of these products are more commonly used in general practice: RBCs, fresh frozen plasma (FFP), platelets and cryoprecipitate. RBC transfusions are mainly administered to improve tissue oxygenation in cases of anaemia or acute blood loss due to trauma or surgery. FFP, platelets and cryoprecipitate are used for the prevention and treatment of bleeding.

Split Blood Products

The last 20 years have seen many advances in transfusion therapy and safety. Blood products are biological products engendering complex interactions with the immune system. Prestorage leukoreduction results in a reduced risk of febrile reactions, CMV transmission, and immune modulation, proving to be safer for patients than non-leuko reduced products.

Simple patient identification issues and clerical error continue to be the primary causes of ABO-incompatible transfusions. Rigorous donor screening as well as serologic and nucleic acid testing for transfusion transmitted infection have brought the blood supply to a very safe level, although transmission of these agents continues to be a problem in underdeveloped countries. Emerging infectious diseases, beyond current laboratory detection capabilities, combined with global travel, pose unknown imminent risks everywhere. We also briefly discuss the current risks of transfusion-transmitted infections.

We review currently available hemostatic blood products, their compositions, and their clinical indications; we mention product modifications currently in development; and we touch upon the hemostatic properties and drawbacks of whole blood, which is currently gaining popularity as an alternative to split blood products. We conclude with an in-depth overview of the risks associated with transfusion, including incompatibility, hemolytic transfusion reactions, transfusion-associated circulatory overload (TACO), and transfusion-related acute lung injury (TRALI).

Role of interleukin-6 in differentiating interleukin-11 induced fever and early bacterial infection

OBJECTIVE

To evaluate the role of Th1/Th2 cytokines (IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ) in differentiating interleukin 11 induced fever with C-reactive protein elevation from early bacterial infection.

METHODS

A total of 74 patients were enrolled in this retrospective study. Serum Th1/Th2 cytokines were determined using cytometric bead array (CBA) techniques. Whenever the patients had febrile disease or elevated CRP, systemic inflammatory signs, procalcitonin (PCT), blood culture and X-ray examination were done. The patients were assigned into infected and non-infected groups based on the clinical and laboratory findings.

RESULTS

The CRP levels in both the groups were significantly increased, but no statistically significant difference was found (P = 0.574). IL-6 levels of the infected group were significantly elevated with simultaneously elevated IL-10 levels in a proportion of the patients. IL-6 levels of non-infected patients were normal. IL-6 and IL-10 levels of infected patients were significantly higher than those of non-infected patients (P = 0.005, 0.015, respectively).

CONCLUSIONS

For the patients treated with recombinant human interleukin 11 (rhIL-11), IL-6 and IL-10 measurements can be a useful adjuvant tool for the differentiation of rhIL-11 induced fever with C-reactive protein elevation from early bacterial infection.

Blood product transfusions and reactions

Blood product transfusions are an essential component of the practice of emergency medicine. From acute traumatic hemorrhage to chronic blood loss necessitating transfusion for symptomatic anemia, familiarity with individual blood products and their indications for transfusion is an essential tool for every emergency physician (EP). Although the focus of this article is primarily on the transfusion of red blood cells, many of the concepts are applicable to the transfusion of all blood products. EPs must be fully familiar with both the individual blood components and the potential reactions and complications of these transfusions.

Rituximab, plasma exchange and intravenous immunoglobulins as a new treatment strategy for severe HLA alloimmune platelet refractoriness

Platelet refractoriness (PR) due to HLA alloimmunization is a common and serious complication of patients receiving long-term packed red blood cell and platelet transfusions. Although most alloimmunized patients will respond to HLA-matched platelets, 20-50% of patients will remain refractory even to matched platelets. Several measures have been reported to overcome this complication, such as intravenous immunoglobulins (IVIG), plasma exchange (PE), protein A column therapy, or rituximab. We report a woman with acute myeloid leukemia secondary to myelodysplastic syndrome who was diagnosed with PR because of HLA alloimmunization. Due to difficulties in finding HLA-compatible platelet donors by cross-reactive groups in our panel of HLA-typed platelet donors, the patient received treatment with rituximab, PEs and IVIG. With this treatment strategy, the presence of HLA antibodies decreased from a panel-reactive antibody (PRA) of 89-0%. This allowed the performance of hematopoietic progenitor cell transplantation with random donor platelets. Rituximab, PE, and IVIG may be an option to overcome severe PR due to poly-specific HLA alloimmunization.

A consistent approach to platelet transfusion in the NICU

Platelet transfusions are the principal means of treating thrombocytopenia in neonatal intensive care units (NICUs), and are generally used as treatment of thrombocytopenic neonates who have active bleeding and as prophylactic administration in thrombocytopenic neonates who do not have hemorrhage but appear to be at high risk for bleeding. In this article, we summarize the rationale, benefits and risks of platelet transfusions in neonates. We review the importance of choosing the best product available for platelet transfusion, and we emphasize the importance of adopting and adhering to transfusion guidelines.

Initial performance evaluation of the UniCel® DxH 800 Coulter® cellular analysis system

The Beckman Coulter UniCel® DxH 800 is a hematology analyzer incorporating new electronic and mechanical design with advanced algorithm technology to perform CBC, white blood cell (WBC) differential, nucleated red blood cell (NRBC), and reticulocyte analysis. Evaluation of this instrument was performed in our 800-bed tertiary care hospital and specifically centered upon the correlation of WBC, NRBC, and platelet (PLT) enumeration when compared to a predicate analyzer, the Coulter® LH 780, and flow cytometry (FCM) reference methods. Of particular interest were those samples with morphologically confirmed interference and extreme leukocytosis (evaluated with respect to red blood cell parameter correction). The sample set (n=272) consisted of morphologically normal and hematologically abnormal patients. Correlation of the WBC, PLT, and NRBC showed r(2) values of 0.994, 0.985, and 0.910 for the DxH 800 vs. FCM, respectively. The presence of interfering particles did not affect the accuracy of the DxH 800 with respect to WBC counts. The DxH 800 showed accurate PLT and NRBC counts in the clinically significant low range when compared to FCM. Compared to the LH 780, flagging rates were significantly reduced (NRBC flag), or equivalent (WBC, PLT flag) on the DxH 800. The DxH 800 demonstrated higher sensitivity and specificity for PLTs and NRBCs and achieved a lower NRBC false negative rate compared to the LH 780. The UniCel® DxH 800 represents a significant improvement to previous impedance analyzers in accurately detecting the presence of NRBCs at counts >1/100 WBC. Furthermore, it provides accurate PLT and WBC counts in the presence of interference and improved NRBC flagging efficiency when compared to the LH 780. Correction of red blood cell parameters is appropriate and accurate in cases of extreme leukocytosis.

Disseminated fusariosis and endogenous fungal endophthalmitis in acute lymphoblastic leukemia following platelet transfusion possibly due to transfusion-related immunomodulation

Background

To report a case of disseminated fusariosis with endogenous endophthalmitis in a patient with acute lymphoblastic leukemia. Transfusion-associated immune modulation secondary to platelet transfusion could play an important role in the pathophysiology of this case.

Case Presentation

A 9 year-old male with acute lymphoblastic leukemia complicated by pancytopenia and disseminated Intravascular coagulation was given platelet transfusion. He developed disseminated fusariosis and was referred to the ophthalmology team for right endogenous endophthalmitis. The infection was controlled with aggressive systemic and intravitreal antifungals.

Conclusion

Patients with acute lymphoblastic leukemia are predisposed to endogenous fungal endophthalmitis. Transfusion-associated immune modulation may further increase host susceptibility to such opportunistic infections.

From whole blood to component therapy: the economic, supply/demand need for implementation of component therapy in sub-Saharan Africa

Blood may be transfused as whole blood or as one of its components. Because patients seldom require all of the components of whole blood, it makes sense to transfuse only that portion needed by the patient for a specific condition or disease. This treatment, known as "blood component therapy", allows several patients to benefit from one unit of donated whole blood. Blood components include red blood cells, plasma, platelets, and cryoprecipitate. A considerable literature has accumulated over the past decade indicating that leukocytes present in allogeneic cellular blood components, intended for transfusion, are associated with adverse effects to the recipient. These include the development of febrile transfusion reactions, graft-versus-host disease, alloimmunization to leukocyte antigens, and the immunomodulatory effects that might influence the prognosis of patients with a malignancy. Moreover, it has become evident that such leukocytes may be the vector of infectious agents such as cytomegalovirus (CMV), Human T-Lymphotrophic Virus 1/11 (HTLV-I/II), and Epstein Barr (EBV) as well as other viruses. Effective stewardship of blood ensuring that several patients potentially benefit from components derived from one unit of donated whole blood is important for economic, supply/demand reasons and to protect the national inventory at times of national blood shortage. Blood safety in developing countries can be improved by more appropriate use of blood components rather than whole blood transfusion and the provision of alternatives such as oral and intravenous iron, erythropoietin, saline and colloids. This will facilitate the optimal use of the limited blood supply. Political will and open-mindedness to innovative ways to improve supply, appropriateness, optimal use and safety of blood from all types of donors are essential to promote more evidence-based approaches to blood transfusion practice in sub-Saharan Africa.

Current practice and future directions for optimization of platelet transfusions in patients with severe therapy-induced cytopenia

Platelet transfusions are mainly used for patients with thrombocytopenia due to bone marrow failure, especially cancer patients developing severe chemotherapy-induced thrombocytopenia (e.g. patients with acute leukemia or other hematologic malignancies). A prophylactic transfusion strategy is now generally accepted in developed countries. Some clinical data, however, support the use of a therapeutic transfusion strategy at least for certain subsets of these patients. Several methodological approaches can then be used to evaluate the outcome of platelet transfusions, including peripheral blood platelet increments and bleeding assessments. Several factors will influence the efficiency of platelet transfusions; fever and ongoing hemorrhage are among the most important patient-dependent factors, but the number and quality of the transfused platelets are also important. The quality of transfused platelets can be evaluated by analyzing platelet activation, metabolism or senescence/apoptosis. Only evaluation of metabolism is included in international guidelines, but high-throughput methods for evaluation of activation and senescence/apoptosis are available and should be incorporated into routine clinical practice if future studies demonstrate that they reflect clinically relevant platelet characteristics. Finally, platelet transfusions have additional biological effects that may cause immunomodulation or altered angioregulation; at present it is not known whether these effects will influence the long-time prognosis of cancer patients. Thus, several questions with regard to the optimal use of platelet transfusions in cancer patients still need to be answered.

Impact of platelet transfusion on hematoma expansion in patients receiving antiplatelet agents before intracerebral hemorrhage

OBJECTIVES

Patients receiving antiplatelet medications are reported to be at increased risk for hematoma enlargement and worse clinical outcomes following intracerebral hemorrhage (ICH). While platelet transfusions are frequently administered to counteract qualitative platelet defects in the setting of ICH, conclusive evidence in support of this therapeutic strategy is lacking. In fact, platelet transfusions may be associated with adverse effects, and represent a finite resource. We sought to determine the clinical efficacy of platelet transfusion and its impact on systemic complications following ICH in a cohort of patients receiving antiplatelet medications.

METHODS

We retrospectively analysed the medical records of 66 patients admitted to our institution from June 2003 to July 2008 who suffered a primary ICH while receiving antiplatelet (acetylsalicylic acid and/or clopidogrel) therapy. The primary outcome was the rate of significant (>25% increase from admission) hematoma expansion in transfused (n=35) versus non-transfused (n=31) patients. Discharge modified-Rankin score (mRS) and the rates of systemic complications were also assessed.

RESULTS

There were no statistically significant differences in rates of hematoma expansion between cohorts, nor were there differences in demographic variables, systemic complications or discharge mRS. Subgroup analysis revealed that there was a higher rate of hematoma expansion in the clopidogrel cohort (p=0.034) than in the cohort of patients receiving aspirin alone.

DISCUSSION

This study suggests that platelet administration does not reduce the frequency of hematoma expansion in ICH patients receiving antiplatelet medications. This lack of efficacy may relate to transfusion timing, as a significant proportion of hematoma expansion occurs within 6 hours post-ictus. Additionally, the increased rates of hematoma expansion in the clopidogrel cohort may relate to its prolonged half-life. A larger, prospective study is warranted.

Release abilities of adenosine diphosphate from phospholipid vesicles with different membrane properties and their hemostatic effects as a platelet substitute

We have constructed phospholipid vesicles with hemostatic activity as a platelet substitute. The vesicles were conjugated with a dodecapeptide (HHLGGAKQAGDV, H12), which is a fibrinogen γ-chain carboxy-terminal sequence (γ400-411). We have recently exploited these vesicles as a potential drug delivery system by encapsulation of adenosine 5'-diphosphate (ADP) (H12-(ADP)-vesicles). Here we explore the relationship between the ADP release from H12-(ADP)-vesicles with different membrane properties and their hemostatic effects. In total, we prepared five kinds of H12-(ADP)-vesicles with different lamellarities and membrane flexibilities. By radioisotope-labeling, we directly show that H12-(ADP)-vesicles were capable of augmenting platelet aggregation by releasing ADP in an aggregation-dependent manner. The amount of ADP released from the vesicles was dependent on their membrane properties. Specifically, the amount of ADP released increased with decreasing lamellarity and tended to increase with increasing membrane flexibility. Our in vivo results clearly demonstrated that H12-(ADP)-vesicles with the ability to release ADP exert considerable hemostatic action in terms of correcting prolonged bleeding time in a busulphan-induced thrombocytopenic rat model. We propose a recipe to control the hemostatic abilities of H12-(ADP)-vesicles by modulating ADP release based on membrane properties. We believe that this concept will be invaluable to the development of platelet substitutes and other drug carriers.

Platelet transfusions: trigger, dose, benefits, and risks

Over the last half century, platelet transfusion has been an effective therapy for the prevention and treatment of bleeding, particularly in patients with hematologic malignancies. Recent randomized trials have demonstrated that current practices may be suboptimal in a number of ways. The rationale for parsimony in the use of this powerful therapy includes previously described severe and fatal adverse outcomes (including refractoriness, hemolysis from ABO-mismatched transfusions, acute lung injury, and bacterial sepsis), newly described serious potential risks (including thrombosis and earlier leukemic recurrence), difficulty in maintaining adequate supplies of platelets, the need to place volunteer donors on cell separators to provide the product, and cost. Recent findings demonstrate that the platelet count threshold for prophylactic transfusion can be as low as 10,000/µL, and a therapeutic rather than a prophylactic strategy of transfusion for bleeding manifestations only may be equally safe for most patients. Another recently completed study suggests that very low doses of platelet transfusions (the equivalent of half a unit of apheresis platelets or two to three units of whole blood-derived platelets) are as effective at preventing bleeding as much higher doses. One question for which there are no randomized trial data is at what threshold prophylactic platelet transfusion should be given before invasive procedures or major surgery. The typically recommended threshold of 50,000/µL is based only on expert opinion, and substantial observational data indicate that this threshold leads to many transfusions that are likely unnecessary and therefore represent risk with little or no additional benefit.

Novel platelet substitutes: disk-shaped biodegradable nanosheets and their enhanced effects on platelet aggregation

We have studied biocompatible spherical carriers carrying a dodecapeptide, HHLGGAKQAGDV (H12), on their surface as platelet substitutes. This peptide is a fibrinogen γ-chain carboxy-terminal sequence (γ400-411) and specifically recognizes the active form of glycoprotein IIb/IIIa on activated platelets. Our purpose is to assess the possibility of making a novel platelet substitute consisting of disk-shaped nanosheets having a large contact area for the targeting site, rather than conventional small contact area spherical carriers. The H12 peptide was conjugated to the surface of the free-standing nanosheets made of biodegradable poly(d,l-lactide-co-glycolide) (PLGA). These H12-PLGA nanosheets were fabricated onto 3 μm disk-shaped patterned hydrophobic octadecyl regions on a SiO(2) substrate. By way of comparison, spherical H12-PLGA microparticles with the same surface area and conjugation number of H12 were also prepared. The resulting H12-PLGA nanosheets specifically interacted with the activated platelets adhered on the collagen surface at twice the rate of the H12-PLGA microparticles under flow conditions, and showed platelet thrombus formation in a two-dimensional spreading manner. Thus, H12-PLGA nanosheets might be a suitable candidate novel platelet alternative substitute for infused human platelet concentrates for the treatment of bleeding in patients with severe thrombocytopenia.

Aplastic anaemia in pregnancy with severe thrombocytopenia refractory to platelet transfusion: a case and management plan

Aplastic anaemia is a rare haematological disorder during pregnancy, which when complicated by severe thrombocytopenia poses a significant maternal risk. A woman with aplastic anaemia and a platelet (PLT) count of 11 × 10(9)/L refractory to PLT transfusion required caesarean delivery. Proactive planning by a multidisciplinary team, large volume PLT transfusion prior to surgery and postoperative uterine artery embolization resulted in avoidance of mortality. Maternal preferences should be discussed in detail due to the high risk of maternal morbidity and mortality associated with severe aplastic anaemia. This report outlines a management plan to address the medical and ethical issues faced when caring for a pregnant patient with severe aplastic anaemia and severe thrombocytopenia. We credit the good outcome to our proactive multidisciplinary approach.

Performance of automated platelet quantification using different analysers in comparison with an immunological reference method in thrombocytopenic patients

BACKGROUND

Rapidly available and accurate platelet counts play an important role in the evaluation of haemorrhagic status and in assessing the need for platelet transfusions. We, therefore, evaluated platelet counting performance of haematology analysers using optical, impedance and immunological methods in thrombocytopenic patients.

MATERIALS AND METHODS

We considered 99 patients with a platelet (plt) count under 50 x 10(9) plt/L. We compared the platelet counts obtained using ADVIA 2120 (optical method), Cell-Dyn Sapphire (optical, impedance and immunological methods with CD61) and a reference, double staining (CD41+CD61) immunological method.

RESULTS

The platelet counts of all the considered methods showed good correlation with those of the reference method, despite an overestimation in platelet quantification. The degree of inaccuracy was greater for platelet counts under 20 x10(9) plt/L.

CONCLUSIONS

Clinicians who use platelet thresholds below 20 x10(9) plt/L for making clinical decisions must be aware of the limitations in precision and accuracy of cell counters at this level of platelet count. Inaccurate counts of low platelet numbers could create problems if attempts are made to reduce the threshold below 20 x 10(9) plt/L.

Platelet storage lesion: a new understanding from a proteomic perspective

Platelet storage and availability for the purposes of transfusion are currently restricted by a markedly short shelf life of 5 to 7 days owing to an increased risk of bacterial growth and storage-related deterioration called the platelet storage lesion. Because most bacteria grow to confluence within 5 days during storage at room temperature, there is little increased risk of bacterial overgrowth with testing in place, and the only remaining issue is the quality of platelets during the extended storage. Although the manifestations of the storage lesion have been well studied using a variety of in vitro measures, the precise biochemical pathways involved in the initiation and progression of this process have yet to be identified. Proteomics has emerged as a powerful tool to identify and monitor changes during platelet storage and, in combination with biochemical and physiologic studies, facilitates the development of a sophisticated mechanistic view. In this review, we summarize recent experimental work that has led to a detailed overview of protein changes linked to platelet functions and signaling pathways, providing potential targets for inhibitors to ameliorate the storage lesion.