5-day storage of platelet concentrates in CLX containers: effect of type of agitation

In vitro properties of concentrated canine platelets stored in two additive solutions: a comparative study

BACKGROUND

Platelet transfusion therapy poses many challenges in veterinary clinical practice. Lack of readily available blood donors, short shelf-life, and inability to administer a sufficient number of platelets to meet a dog's transfusion need are the major difficulties encountered. Platelet additive solutions are already in use at American and European human blood banks, showing to be a realistic alternative. This study compares the in vitro platelet function in plasma, Composol, or SSP+ during storage for 13 days. Platelet rich plasma-platelet concentrate with 35% plasma and 65% platelet additive solutions (Composol or SSP+) and a control group (100% plasma) were prepared. Swirling, platelet count, blood gases, metabolic variables, platelet activation markers, and apoptosis markers were analyzed on days 1, 5, 9 and 13.

RESULTS

Swirling was well preserved and pH was acceptable (> 6.2) during storage for all platelet additive solutions units until day 9. SSP + units showed more stable pH and metabolic variables until day 13. Platelets in plasma showed higher glucose consumption than in Composol or in SSP+. The platelet additive solutions units showed better platelet metabolism maintenance, reduced glucose consumption and lactate production. The apoptotic markers were still low for 9 days in platelet concentrates with platelet additive solutions, suggesting the possibility to extend the shelf life with the use of SSP+ or Composol.

CONCLUSIONS

Our findings suggest that the uses of Composol and SSP+ in canine platelet concentrates are potential alternatives in veterinary blood banks.

Hemostatic function of apheresis platelets stored at 4°C and 22°C

INTRODUCTION

Platelet refrigeration decreases the risk of bacterial contamination and may preserve function better than standard-of-care room temperature (RT) storage. Benefits could include lower transfusion-related complications, decreased costs, improved hemostasis in acutely bleeding patients, and extended shelf life. In this study, we compared the effects of 22°C and 4°C storage on the functional and activation status of apheresis platelets.

METHODS

Apheresis platelets (n = 5 per group) were stored for 5 days at 22°C with agitation (RT) versus at 4°C with agitation (4°C + AG) and without (4°C). Measurements included platelet counts, mean platelet volume, blood gas analytes, aggregation response, thromboelastography, thromboxane B2 and soluble CD40 ligand release, activation markers, and microparticle formation.

RESULTS

Sample pH levels were within acceptable limits for storage products (pH 6.2-7.4). Platelet glucose metabolism (P < 0.05), aggregation response (adenosine diphosphate: RT 0; 4°C + AG 5.0 ± 0.8; 4°C 5.6 ± 0.9; P < 0.05), and clot strength (maximum amplitude: RT 58 ± 2; 4°C + AG 63 ± 2; 4°C 67 ± 2; P < 0.05) were better preserved at 4°C compared with RT storage. Refrigerated samples were more activated compared with RT (P < 0.05), although thromboxane B2 (P < 0.05) and soluble CD40 ligand release (P < 0.05) were higher at RT. Agitation did not improve the quality of 4°C-stored samples.

CONCLUSIONS

Apheresis platelets stored at 4°C maintain more viable metabolic characteristics, are hemostatically more effective, and release fewer proinflammatory mediators than apheresis platelets stored at RT over 5 days. Given the superior bacteriologic safety of refrigerated products, these data suggest that cold-stored platelets may improve outcomes for acutely bleeding patients.

Platelet preservation: agitation and containers

For platelets to maintain their in vitro quality and in vivo effectiveness, they need to be stored at room temperature with gentle agitation in gas-permeable containers. The mode of agitation affects the quality of the platelets, and a gentle method of agitation, either a circular or a flat bed movement, provides the best results. Tumblers or elliptical agitators induce platelet activation and subsequent damage. As long as the platelets remain in suspension, the agitation speed is not important. Agitation of the platelet concentrates ensures that the platelets are continuously oxygenated, that sufficient oxygen can enter the storage container and that excess carbon dioxide can be expelled. During transportation of platelet concentrates, nowadays over long distances where they are held without controlled agitation, platelets may tolerate a certain period without agitation. However, evidence is accumulating that during the time without agitation, local hypoxia surrounding the platelets may induce irreversible harm to the platelets. Over the decades, more gas-permeable plastics have been used to manufacture platelet containers. The use of different plastics and their influence on the platelet quality both in vitro and in vivo is discussed. The improved gas-permeability has allowed the extension of platelet storage from 3 days in the early 1980s, to currently at least 7 days. In the light of new developments, particularly the introduction of pathogen reduction techniques, the use of platelet additive solutions and the availability of improved automated separators, further (renewed) research in this area is warranted.

Preparation, storage and quality control of platelet concentrates

Patients with thrombocytopaenia need transfusions of platelet concentrates to prevent or stop bleeding. A platelet transfusion should provide platelets with good functionality. The quality of platelet concentrates (PCs) is affected by the preparation method and the storage conditions including duration of storage, type of storage container, and storage solution (plasma or an additive solution). Different in vivo and in vitro techniques can be used to analyse PCs. Platelets can be collected by apheresis technique, and from whole blood using either the buffy-coat or the platelet-rich plasma method. PCs can be gamma irradiated to prevent occurrence of graft-versus-host disease in the recipient. Pathogen inactivation procedures have been developed to prevent transmission of bacteraemia.

Use of prostaglandin E1 during preparation of platelet concentrates

A paired study in 10 autologous volunteer donors was undertaken to investigate the efficacy of adding prostaglandin E1 (PGE1) in vitro during routine platelet concentrate (PC) production. After 5 days storage, PCs prepared with PGE1 were compared with control PCs. In vivo platelet recovery, survival and biodistribution were determined following autologous infusion of indium-111 labelled platelets into volunteers, together with the in vitro evaluation of platelet function and biochemistry. PGE1 facilitated easier and faster platelet resuspension following centrifugation. After storage there were few significant in vitro differences between PCs prepared with PGE1 and control PCs. The artifactual leucocyte concentration was significantly lower in the presence of PGE1, suggesting less platelet aggregates had been formed during storage and beta-thromboglobulin release was significantly reduced by PGE1, 14.0 +/- 6.0 micrograms per 10(9) platelets compared with 22.3 +/- 9.8 micrograms per 10(9) platelets in control PCs, (P < 0.01), indicating PGE1 reduced both platelet aggregation and activation probably at the initial preparation stage, known to produce the greatest trauma. Initial in vivo platelet recovery for PCs prepared with PGE1 was similar to that of control PCs, 41.1 +/- 12.5% vs. 44.4 +/- 8.0%, respectively, and there were no differences in organ distribution at 24 h. However, in vivo multiple hit survival was reduced in the presence of PGE1, 5.8 +/- 1.6 days compared with 6.9 +/- 1.4 days in control PCs (P < 0.05). Despite the ability of PGE1 to facilitate platelet resuspension and inhibit platelet aggregation and activation during preparation of the PCs, the reduced in vivo survival time may preclude the use of PGE1 during routine PC preparation.

Effect of agitation on the quality of platelet concentrates

Platelet concentrates (PCs) were stored for 4 days at 22 degrees C in 400 ml second-generation (PL1240) platelet packs with either constant agitation, manual mixing once every 24 h or without agitation at any time. After 4 days storage, in vivo recovery, survival and biodistribution were determined following indium-111 labelling of platelets and infusion into autologous volunteers. In vitro assays of platelet function and biochemistry were likewise carried out after 4 days storage. The PCs stored without agitation had significantly lower in vivo recoveries, pH and aggregation responses to ionophore A23187 and a combination of collagen and epinephrine and significantly higher beta-thromboglobulin and indium-111 release than the agitated PCs. The manually mixed PCs were not significantly different from the constantly agitated PCs. PCs mixed simply once every 24 h remained viable with active oxidative phosphorylation and a pH above 6.74 in all but 1 case indicating that PCs stored at 22 degrees C for up to 4 days with only intermittent mixing are satisfactory for transfusion. A change from constant agitation would reduce capital costs in mixing equipment and simplify the transport of PCs from the transfusion centre to small hospital blood banks.

Paired in vivo and in vitro comparison of apheresis and "recovered" platelet concentrates stored for 5 days

Using a paired study, in vivo and in vitro characteristics of apheresis platelets collected on a cell separator and single-donor whole-blood (recovered) platelets via platelet-rich plasma (PRP) were compared after storage for 5 days in similar plastic containers. Autologous platelets from each of 12 volunteers were labeled with 111Indium after storage and reinjected. There was no significant difference in circulating recovery between platelets prepared by the two methods, and only one of five models of survival showed a significant difference. Hypotonic shock recovery was significantly better in apheresis than recovered platelets (57.0% and 32.4%, respectively), whilst aggregation to ADP at 3.2 microM and 32 microM was significantly higher in recovered than in apheresis platelets (17.0% and 45.2% versus 7.8% and 32.9%, respectively). Lactate dehydrogenase (LDH) content was significantly higher in recovered platelets (143.3 versus 77.1 IU/10(11) platelets), but LDH release was similar (15.0% cf. 12.6%). There was no significant difference between the two platelet preparations for platelet concentration, pH, aggregation with the calcium ionophore A23187 or collagen plus epinephrine, or ATP content or release. beta-TG release was lower in apheresis platelets. Neither product was consistently better than the other for the parameters tested, but apheresis platelets have the advantage of lower donor exposure to the patient.

Evaluation of platelets collected by a new portable apheresis device

We studied the efficiency of platelet collection by the Mobile Collection System (MCS) using two types of experimental protocols and evaluated the effect of storage at 22 degrees C on the platelet concentrates (PC). MCS is a new blood cell separator that combines discontinuous flow features with a new computerized operating system and can be used to harvest either full units of apheresis PC (SDP protocol) or half units of PC together with one to two units of plasma (PLP protocol). On the average, 1.98 x 10(11) +/- 0.46 x 10(11) (mean +/- SD) platelets were obtained by the PLP protocol and 3.01 x 10(11) +/- 0.70 x 10(11) and 4.2 x 10(11) +/- 1.12 x 10(11) by the early and later versions of the SDP protocols, respectively. The mean number of WBC per PC ranged from 3.3 to 4.7 x 10(8). During the storage period pH stayed above 7.0. On the average, the production of one molecule of lactate corresponded to the consumption of 0.538 molecules of glucose, indicating that less than 8% of glucose was consumed by the oxidative pathway. There were only small increases in LDH and B thromboglobulin concentrations. Furthermore, the ability of platelets to recover from osmotic shock and to aggregate following exposure to dual agonists declined only slightly during storage, indicating that both viability and function of platelets collected by the MCS were preserved during storage.

Centrifugation of very freshly donated blood may yield platelets unstable to storage in the new generation of containers

The stability of platelets stored in the second generation of container has been examined further. Platelet concentrates prepared in CPD anticoagulant were found to deteriorate fairly rapidly during storage if prepared from very freshly donated blood, whereas a more than 4-hour delay between donation and platelet isolation yielded platelet concentrates much more stable to storage. Delays of more than 2 h (relative to the time of donation) in the isolation of platelets led to decreases in the aggregation response to low or moderate doses of collagen. Platelets from blood collected into CPD adenine showed decreased aggregation responses relative to equivalent cells from blood collected into adenine-free anticoagulant. It seems that a decreased aggregation response is associated with improved storage properties.

Effects of autoclave sterilization on the physical properties of storage bags and granulocyte function

Autoclave sterilization altered the leaching of plasticizer, CO2 gas permeability, surface area and the surface wettability of bag films. These changes affected granulocyte cell counts and functions during storage. Four types of polyvinyl chloride bags, with di-(2-ethylhexyl)phthalate (DEHP) or tri-(2-ethylhexyl)trimellitate (TOTM) as plasticizer, with or without treatment by glow discharge (H2), were sterilized with ethylene oxide (EO) or autoclaving (AC). The greatest amounts of plasticizer leached from DEHP-EO bags. TOTM plasticizer did not leach into plasma. CO2 gas permeability was greater with TOTM than DEHP. AC sterilization decreased the surface area of bags. Wettability of film surfaces was greatest with H2-TOTM-EO. After storage in these bags for 24 and 48 h at 22 degrees C, the granulocyte cell counts and functions were greatest in H2-TOTM-EO bags with the nonleaching plasticizer, higher CO2 gas permeability and higher wettable surface due to glow-discharge treatment. The H2-TOTM-EO bag was useful as a granulocyte storage container.

Platelet storage lesion: formation of platelet fragments with platelet factor 3 activity

Certain samples of stored platelet concentrates exhibited marked platelet factor 3 activity. This activity was associated almost completely with platelet fragments formed during storage. Platelet concentrates containing high levels of these fragments and hence high platelet factor 3 activity were characterized after storage by alkaline plasma pH values, high levels of extracellular lactate dehydrogenase activity and relatively low cell counts.

Effects of plasticizers and plastic bags on granulocyte function during storage

The influence of the plasticizers, di-(2-ethylhexyl)phthalate (DEHP) and tri-(2-ethylhexyl)trimellitate (TOTM), on granulocyte function was examined. Polyvinyl chloride (PVC) bags with DEHP (DEHP-PVC) leaked DEHP into plasma, but TOTM did not dissolve in plasma under the same conditions. Glow discharge treatment inhibited the leakage of DEHP from DEHP-PVC bags. Depending on the amount of DEHP added into granulocyte suspension, chemotaxis and bactericidal activity decreased, but cell counts and phagocytosis were not affected. During storage for 24 h at 22 degrees C, granulocyte function decreased greatly in DEHP-PVC, but was well maintained in the bags which did not leak plasticizers, TOTM-PVC and glow-discharged DEHP-PVC.

Storage of platelet concentrates--an in vitro study of four types of plastic packs

Four types of plastic blood collection packs were studied for their ability to preserve platelet function during a 5 d storage period. The platelet concentrates were stored in polyvinyl chloride (Tuta Laboratories), PL 1240 and PL 732 (Fenwal Laboratories) and CLX (Cutter Laboratories) packs, on a Fenwal elliptical rotator at 20 degrees-24 degrees C. Plasma pH, lactate concentration, hypotonic shock response (HSR), platelet aggregation in response to ADP, collagen and ristocetin and levels of the plasticisers, di-2-ethylhexyl phthalate (DEHP) and tri-ethylhexyl trimellitate (TEHTM), were measured. Morphological changes were assessed by electron microscopy. No significant fall in pH occurred in any type of pack but in vitro function and platelet morphology was generally better preserved in Tuta and CLX packs than in PL 732 and PL 1240. Very little TEHTM leached out of the PL 1240 and CLX packs whereas the mean concentration of DEHP in the platelet concentrates stored in Tuta packs was 27.4 mg/100 ml plasma after 5 d of storage. The results indicate that it is possible to prepare and store platelet concentrates in polyvinyl chloride plastic packs for a period of 5 d and maintain their function and viability.

Evaluation of flatbed reciprocal motion agitators for resuspension of stored platelet concentrates

We studied the storage characteristics of platelet concentrates prepared in polyolefin (PL-732) and thin-film polyvinyl chloride (CLX) plastic bags and stored on a newly designed flatbed reciprocal motion agitator with a 1.5 inch (3.8 cm) lateral movement and an oscillation frequency of 70 cycles/min. We also studied the ability of this device to resuspend the platelet button formed after preparative centrifugation. Results showed that platelet concentrates stored on the 1.5-inch shaker had storage characteristics equivalent to those reported for the conventional 70 cycles/min, 1-inch (2.5-cm) lateral movement flatbed shaker. Due to a more rapid acceleration and deceleration rate, however, the 1.5-inch shaker resuspended the platelet button formed after preparative centrifugation much more efficiently than did the less dynamic 1-inch shaker. Furthermore, with either agitator, platelet aggregates in the CLX bag were more readily resuspended than were aggregates in the PL-732 bag due in part to differences in plastic bag wall elasticity.