The functional integrity of platelets in volume-reduced platelet concentrates

Separation of platelets by size in a microfluidic device based on controlled incremental filtration

The significant biological and functional differences between small and large platelets suggested by recent studies could have profound implications for transfusion medicine. However, investigating the relationship between platelet size and function is challenging because separating platelets by size without affecting their properties is difficult. A standard approach is centrifugation, but it inevitably leads to premature activation and aggregation of separated platelets. This paper describes the development and validation of a microfluidic device based on controlled incremental filtration (CIF) for separating platelets by size without the cell damage and usability limitations associated with centrifugation. Platelet samples derived from whole blood were used to evaluate the dependence of the CIF device separation performance on design parameters and flow rate, and to compare the properties of PLT fractions generated by the CIF device with those produced using a centrifugation protocol in a split-sample study. This was accomplished by quantifying the platelet size distribution, mean platelet volume (MPV), platelet-large cell ratio (P-LCR) and platelet activation before and after processing for all input and output samples. The 'large platelet' fractions produced by the CIF device and the centrifugation protocol were essentially equivalent (no significant difference in MPV and P-LCR). Platelets in the 'small platelet' fraction produced by the CIF device were significantly smaller than those produced by centrifugation (lower MPV and P-LCR). This was because the CIF 'small platelet' fraction was contaminated by much fewer large platelets (∼2-times lower recovery of >12 fL platelets) and retained the smallest platelets that were discarded by the centrifugation protocol. There was no significant difference in platelet activation between the two methods. However, centrifugation required a substantial amount of additional anticoagulant to prevent platelet aggregation during pelleting. Unlike centrifugation, the CIF device offered continuous, flow-through, single-step processing that did not cause platelet aggregation. Such a capability has the potential to accelerate the basic studies of the relationship between platelet size and function, and ultimately improve transfusion practice, particularly in the pediatric setting, where the need for low-volume, high-quality platelet transfusions is most urgent.

Neonatal Blood Banking Practices

There is little formal guidance to direct neonatal blood banking practices and, as a result, practices vary widely across institutions. In this vulnerable patient population with a high transfusion burden, considerations for blood product selection include freshness, extended-storage media, pathogen inactivation, and other modifications. The authors discuss the potential unintended adverse impacts in the neonatal recipient. Concerns such as immunodeficiency, donor exposures, cytomegalovirus transmission, volume overload, transfusion-associated hyperkalemia, and passive hemolysis from ABO incompatibility have driven modifications of blood components to improve safety.

Preventing adverse reactions in pediatric transfusions using washed platelet concentrate

Blood transfusion is an important form of supportive care in children; however, transfusion-associated adverse reactions (TARs) are a problem. As with adults, allergic transfusion reactions (ATRs) and febrile non-hemolytic transfusion reactions (FNHTRs) are major TARs, and the frequency of ATRs caused by platelet concentrate (PC) tends to be particularly high. The plasma component of the blood product is thought to be a major factor in the onset of TARs such as ATR and FNHTR. By contrast, in children, age, underlying disease, and number of blood transfusions may be relevant patient-related factors. Although acetaminophen or diphenhydramine may be used prophylactically to prevent TARs, there is no clear evidence of their effectiveness. Volume-reduced PC is used to prevent TARs; however, it may be difficult to maintain the quality of platelets. Plasma-replaced PC stored with platelet additive solution raises the concern that TARs cannot be completely prevented by residual plasma. Washed PC removes most of the plasma, so it can effectively prevent ATR and FNHTR. The recent development of platelet additive solution [M-sol, bicarbonate Ringer's solution supplemented with acid-citrate-dextrose formula A (BRS-A)] in Japan has enabled the maintenance of the quality of platelets for long periods. The clinical use of washed PC in Japan has therefore progressed. Washed PC with M-sol or BRS-A for pediatric patients can effectively prevent TARs without diminishing the transfusion effect. The supply of washed PC has begun from the Japanese Red Cross Society, and it has become possible to use washed PC at all medical institutions in Japan.

Transfusion outcome for volume- and plasma-reduced platelet concentrates for pediatric patients

BACKGROUND AND OBJECTIVES

Plasma reduction in platelet concentrate (PC) products has been reported to prevent large volume load and transfusion-related adverse reactions (TRARs). However, volume reduction might be associated with a poor transfusion response because of a deterioration in platelet (PLT) quality. Because PLT quality control and transfusion responses for recently washed PCs using PLT additive solutions are superior, we investigated the clinical safety and transfusion efficacy of volume-reduced washed PCs in pediatric patients.

MATERIALS AND METHODS

We prepared a simplified resuspended PC product (RPC) as a washed PC. Regular RPC (R-RPC) included equivalent volumes of bicarbonate Ringer's solution and anticoagulant citrate dextrose solution A (BRS-A) as the resuspension solution. Half RPC (H-RPC) was prepared by adding a half volume of BRS-A. Twenty-four pediatric patients were scheduled for transfusions with R-RPC and H-RPC up to 4 times. R-RPC was transfused 42 times into 24 patients. H-RPC was transfused 41 times into 23 patients.

RESULTS

Neither product was observed to cause TRARs. Although the calculated PLT recovery for H-RPC was significantly reduced, the posttransfusion corrected count increment (24 h) did not differ. Moreover, similar results were observed for vital signs during transfusion.

CONCLUSION

Volume-reduced washed PC can be transfused without causing TRARs, differences in vital signs, or inferior transfusion responses. Volume-reduced washed PC also provides the advantages of shortened transfusion times and reduced volume loads. Although a standard technique for stable resuspension is necessary, volume-reduced washed PC may be a beneficial option for children, including neonates, or individuals with cardiovascular or renal problems.

Platelet Administration During Cardiopulmonary Bypass in Neonates: A Universal Therapy Applied in a Novel Way

Advances in pharmaceuticals (eg, factor concentrates), laboratory testing (eg, rotational thromboelastometry), and processes (eg, transfusion protocols) have contributed to improved outcomes regarding transfusion in neonates undergoing surgical repair for congenital heart disease. A novel strategy, platelets administered during the rewarming phase of cardiopulmonary bypass, as a solution to improved hemostasis, was prospectively evaluated in 42 neonates. Improved intraoperative and postoperative hemostasis was observed in neonates given platelets during the rewarming phase of cardiopulmonary bypass.

Traditional and emerging technologies for washing and volume reducing blood products

Millions of blood components including red blood cells, platelets, and granulocytes are transfused each year in the United States. The transfusion of these blood products may be associated with adverse clinical outcomes in some patients due to residual proteins and other contaminants that accumulate in blood units during processing and storage. Blood products are, therefore, often washed in normal saline or other media to remove the contaminants and improve the quality of blood cells before transfusion. While there are numerous methods for washing and volume reducing blood components, a vast majority utilize centrifugation-based processing, such as manual centrifugation, open and closed cell processing systems, and cell salvage/autotransfusion devices. Although these technologies are widely employed with a relatively low risk to the average patient, there is evidence that centrifugation-based processing may be inadequate when transfusing to immunocompromised patients, neonatal and infant patients, or patients susceptible to transfusion-related allergic reactions. Cell separation and volume reduction techniques that employ centrifugation have been shown to damage blood cells, contributing to these adverse outcomes. The limitations and disadvantages of centrifugation-based processing have spurred the development of novel centrifugation-free methods for washing and volume reducing blood components, thereby causing significantly less damage to the cells. Some of these emerging technologies are already transforming niche applications, poised to enter mainstream blood cell processing in the not too distant future.

Blood banking/immunohematology: special relevance to pediatric patients

Blood banking/immunohematology is an area of laboratory medicine that involves the preparation of blood and blood components for transfusion as well as the selection and monitoring of those components following transfusion. The preparation, modification, and indications of both traditional and newer products are described in this review, along with special considerations for neonates, patients undergoing hematopoietic stem cell transplantation, those with sickle cell disease, and others. Immunohematological techniques are critical in the provision of blood and blood products and are briefly discussed.

Maintenance of storage properties of pediatric aliquots of apheresis platelets in fluoroethylene propylene containers

BACKGROUND

Platelet (PLT) aliquots for pediatric use have been shown to retain in vitro properties when stored in gas-impermeable syringes for up to 6 hours. As an alternative, PLT aliquots can be stored for longer periods in containers used for storage of whole blood-derived PLTs. These containers are not available separate from whole blood collection sets and PLT volumes less than 35 mL either have not been evaluated or may be unsuitable for PLT storage. Gas-permeable fluoroethylene propylene (FEP) containers have been used in the storage of cell therapy preparations and are available in multiple sizes as single containers but have not been evaluated for PLT storage.

STUDY DESIGN AND METHODS

A single apheresis unit was divided on Day 3 into small aliquots with volume ranging from 20 to 60 mL, transferred using a sterile connection device, and stored for an additional 2 days either in CLX (control) or in FEP containers. PLT storage properties of PLTs stored in FEP containers were compared to those stored in CLX containers. Standard PLT in vitro assays were performed (n =6).

RESULTS

PLT storage properties were either similar to those of CLX containers or differed by less than 20% excepting carbon dioxide levels, which varied less than 60%.

CONCLUSION

Pediatric PLT aliquots of 20, 30, and 60mL transferred on Day 3 into FEP cell culture containers adequately maintain PLT properties for an additional 2days of storage.

In vitro platelet quality in storage containers used for pediatric transfusions

BACKGROUND

The in vitro quality of small-volume platelet (PLT) aliquots for pediatric transfusions was assessed to determine the best practice approach.

STUDY DESIGN AND METHODS

Small volumes (50 mL) of single apheresis PLT components (APCs), collected on either CaridianBCT Trima or Haemonetics MCS+ instruments, were aliquoted on Days 2, 3, 4, and 5 postcollection into Fenwal PL1240 or 4R2014 bags or 60-mL polypropylene syringes. Samples were tested for in vitro quality at their recommended expiry times (4 hr for 4R2014 bags and syringes or Day 5 for PL1240 bags). Assays included pH, CD62P expression, and metabolic measures.

RESULTS

CD62P expression increased throughout storage in all containers. Among the small-volume containers, pH, pCO(2) , lactate, and bicarbonate varied considerably. Regardless of the day of aliquoting, pCO(2) was significantly higher and pO(2) was significantly lower in gas-impermeable syringes than other containers. No bacterial growth was detected in any sample.

CONCLUSION

The quality of APCs aliquoted into small-volume containers meets regulatory requirements and is generally equivalent to that of full-volume APCs at expiry.

The effect of plasma removal from apheresis platelet concentrates on platelet function

The effect of plasma removal on platelet function has scarcely been investigated. Plasma removal from apheresis platelet concentrates was achieved by centrifugation at 5000 g for 6 min or 2000 g for 10 min. After resting for 1 h, platelet concentrates were resuspended in 0·9% NaCl. Platelet function was tested before centrifugation and after resuspension by multiple electrode impedance aggregometry (MEA) and light transmission aggregometry (LTA). Plasma removal resulted in 10-14% lower response to TRAP-6 by MEA using both washing procedures, whereas TRAP-6-inducible aggregation by LTA increased slightly (2-5%). Neither plasma removal method affected collagen-induced aggregation. Thus, platelet function did not deteriorate significantly by either method.

Storage of aliquots of apheresis platelets for neonatal use in syringes with and without agitation

BACKGROUND

To facilitate volume control in neonates, platelets (PLTs) are aliquoted and stored for short periods in non-gas-permeable syringes before infusion. Although agitation of PLTs during storage in gas-permeable bags is performed to maintain their quality, the effect of syringe agitation during storage is unknown.

STUDY DESIGN AND METHODS

Double apheresis PLTs (n = 6) were collected and split, providing two identical products. On Days 2 and 4 of storage, aliquots from one bag of each pair were transferred to two syringes and stored for 6 hours on flatbed agitator or were left at 20 to 24 °C without agitation. A series of in vitro tests was performed on Days 0, 2 (Hours 0 and 6), and 4 (Hours 0 and 6). Control samples were obtained from the second matched bag that was stored on the agitator. Data were analyzed by one-way analysis of variance with differences considered significant if the p value was less than 0.05.

RESULTS

Comparable results for several PLT variables were obtained with or without agitation of the syringes. On Day 4 Hour 6, pH values were 7.18 ± 0.12 (agitated syringes) and 7.19 ± 0.1 (nonagitated syringes), and extent of shape change and hypotonic shock response measurements were not significantly different between agitated syringes and nonagitated syringes (23.7 ± 6.4 and 74.3 ± 9.8% vs. 23.3 ± 5.4 and 76.0 ± 7.6%), respectively.

CONCLUSION

Based on in vitro testing, apheresis PLT aliquots can be stored in syringes for at least 6 hours without agitation before transfusions.

A comparison of washed and volume-reduced platelets with respect to platelet activation, aggregation, and plasma protein removal

BACKGROUND

Washed or volume-reduced platelets (PLTs) are occasionally requested for patients with a history of allergic or anaphylactic transfusion reactions. However, conclusive data are not available as to which method is more suitable.

STUDY DESIGN AND METHODS

A direct comparison of saline-washed and volume-reduced PLTs was performed by splitting 11 units of 6-day-old apheresis PLT units. PLT activation, aggregation, plasma protein, and PLT count were determined before and after each procedure. To assess whether washing using neutral, calcium-free Ringer's acetate (NRA) would better preserve PLT function, 8 additional units of apheresis PLTs were split and were washed in saline or NRA.

RESULTS

Saline washing resulted in significantly increased number of activated, P-selectin-expressing PLTs compared to volume reduction (24.2% vs. 10.3%, p = 0.001). Aggregation was also significantly reduced (-40.6% vs. -0.8%, p = 0.004). Plasma protein removal was significantly better for saline-washed than volume-reduced PLTs (96% vs. 51.1%, p < 0.001). PLT recovery was not significantly different for saline-washed versus volume-reduced PLTs (70.5% vs. 80.7%, p = 0.079). There was no difference between washing in saline or NRA with regard to PLT activation and loss of aggregation.

CONCLUSIONS

PLT washing with saline or NRA significantly increases PLT activation and decreases PLT aggregability. On the other hand, volume reduction does not adequately remove plasma proteins. Therefore, PLT washing should be reserved for patients with a history of severe allergic or anaphylactic transfusion reactions. We suggest that fresher PLTs be selected to improve the functionality of washed PLTs.

Effects of storage duration and volume on the quality of leukoreduced apheresis-derived platelets: implications for pediatric transfusion medicine

BACKGROUND

Platelet (PLT) storage adversely affects PLT structure and function in vitro and is associated with decreased PLT recovery and function in vivo. In pediatric transfusion medicine, it is not uncommon for small residual volumes to remain in parent units after aliquot preparation of leukoreduced apheresis-derived PLTs (LR-ADP). However, limited data exist regarding the impact of storage on residual small-volume LR-ADP.

STUDY DESIGN AND METHODS

Standard metabolic testing was performed on residual volumes of LR-ADP after aliquot removal and PLT aggregometry using a dual agonist of ADP and collagen was performed on stored, small-volume aliquots (10-80mL) created from an in vitro model of PLT storage.

RESULTS

Seventy-seven LR-ADP underwent metabolic (n=67) or metabolic and aggregation (n=10) studies. All products maintained a pH value of more than 6.89 throughout storage. Lactate and pCO(2) increased proportionally with longer storage time. Regardless of acceptable metabolism during storage, aggregation in 10- to 20-mL aliquots was impaired by Day 4 and aliquots less than 40 mL demonstrated the most dramatic decrease in aggregation from baseline.

CONCLUSIONS

Despite maintenance of acceptable metabolic conditions, residual volumes of LR-ADP develop impaired aggregation in vitro that may adversely affect PLT survival and function in vivo. At volumes below 40mL, LR-ADP revealed reduced aggregation. As a result, it is recommended to monitor and record volumes of LR-ADP used for pediatric transfusion. Moreover, once LR-ADP attain a volume of 50mL or less on Day 4 or Day 5 of storage, consider discarding these products until their in vivo efficacy can be studied.

Platelet Transfusion Therapy

This article provides guidelines for the appropriate use of platelet transfusions to reduce unnecessary transfusions, thereby avoiding transfusion-related risks to the patients and the costs of platelet therapy. Platelet products available for transfusion are whole blood derived platelet concentrates and apheresis platelets. Leukoreduced platelets can be used to reduce platelet alloimmunization, cytomegalovirus transmission, and febrile transfusion reactions, while gamma irradiation prevents transfusion-associated graftversus-host disease. Other topics discussed are the expected response to transfused platelets and reasons for poor responses related to alloimmunization, underlying disease state, clinical conditions, and drugs. Appropriate transfusion guidelines based on pretransfusion platelet count, platelet dose, and whether the transfusion is prophylactic or therapeutic are outlined. Identification, prevention, and management of adverse consequences of platelet transfusions and platelet refractoriness are discussed.

Evidence-based platelet transfusion guidelines

Transfused platelets (plts) are either pooled random-donor platelet (plt) concentrates or single-donor apheresis plts. When stored for 5 days, all of these products are equally efficacious. A 10,000/microL prophylactic plt transfusion trigger has been documented to be both hemostatically efficacious and cost effective in reducing plt transfusion requirements. The optimal plt dose/transfusion is being evaluated in an ongoing clinical trial. Therapeutic plt transfusions to control or prevent bleeding with trauma or surgical procedures require higher transfusion triggers of 100,000/microL for neurosurgical procedures and between 50,000/microL and 100,000/microL for other invasive procedures or trauma. Leukoreduction has been documented to reduce plt alloimmunization rates, cytomegalovirus (CMV) transmission by transfusion, and febrile transfusion reactions. Whether it reduces immunomodulatory effects of transfusion (i.e., decreases infection rates and cancer recurrence) is still controversial, as is universal leukoreduction. Poor responses to plt transfusions are often multifactorial. For alloimmune plt refractoriness, HLA matching, cross-matching, and identification of the specificity of the patient's antibodies with avoidance of mismatched donor antigens are all equally effective in identifying compatible plts for transfusion. Other causes of poor plt responses are splenomegaly, ABO mismatching, females with 2 or more pregnancies and males, use of heparin or amphotericin, bleeding, fever, graft-vs-host disease (GVHD), and vaso-occlusive disease (VOD).