Autologous Platelet Survival Research Articles

A randomized study of buffy coat platelets in platelet additive solution stored 1–5 versus 6–7 days prior to prophylactic transfusion of allogeneic haematopoietic progenitor cell transplant recipients

Storage of platelets > 5 days provides improved availability, logistical management and decreased outdating. Promising results on in vitro parameters and on in vivo post-transfusion recovery and survival of autologous platelets in healthy volunteers have earlier been shown. To provide additional verification, randomized patient transfusion studies are needed. Sixty allogeneic haematopoietic progenitor cell transplant recipients were randomized to receive buffy-coat (BC) platelets stored in platelet additive solution (PAS) for 1-5 days the first time a prophylactic transfusion was needed after transplantation, followed the second time by platelets stored for 6-7 days or vice versa. The corrected count increment (CCI) for 1 and 24 h were calculated. CCI 1 h and CCI 24 h were higher for platelets stored 1-5 days as compared to 6-7 days, 10.4 +/- 5.1 vs. 7.4 +/- 3.8 (P < 0.001) and 5.4 +/- 4.1 vs. 2.6 +/- 2.6 (P < 0.001), respectively. Time to next platelet transfusion was significantly longer after a transfusion of platelets stored for 1-5 days as compared to platelets stored for 6-7 days: 2.2 +/- 1.1 vs. 1.6 +/- 0.8 days, respectively (P < 0.005). No differences in bleeding events and no transfusion reaction were recorded. The advantage of an extension of platelet storage time beyond day 5 should be balanced against the increased need for platelet transfusions that may occur and the conceivable risk of transfusion failure.

Pathophysiology and thrombokinetics in autoimmune thrombocytopenia

Studies that have measured platelet survival by autologous platelet labeling with 111In and51 Cr have differed in their results. Although all studies have revealed a significant decrease in platelet life span, the rates of platelets entering the circulation, a calculated and inferred determination, have been found to be moderately decreased to as much as five times normal. Several mechanisms have been proposed to explain an apparent decrease in platelet production, including a true decrease due to damage to the megakaryocytes by autoantibody, versus a decrease only in ‘effective’ production due to intramedullary destruction by the reticuloendothelial system. Recently, the identification of the cytokine, thrombopoietin, has allowed the evaluation of another aspect of the pathophysiology of thrombocytopenic states. Megakaryocyte growth factor levels are increased 10 to 20 times in patients who are thrombocytopenic due to chemotherapy or aplastic anemia, but may be decreased, normal, or only modestly raised in patients with immune platelet destruction. Autologous platelet survival measurements, prior to and while on therapy with a stable platelet count, reveal that removal of part of the reticuloendothelial system with splenectomy leads to increased platelet survival and platelet number. Similar studies reveal that corticosteroid treatment for immune thrombocytopenic purpura (ITP) effectively increases the rate of platelet production but does not change platelet survival. It may be that other therapies are effective by a combination of these mechanisms. Stimulation of thrombopoietin production or administering exogenous cytokine may have a role to play in future management of patients with ITP.

Platelet concentrates stored for 5 days in a reduced volume of plasma maintain hemostatic function and viability

Platelet concentrates prepared from whole blood are generally suspended in a standard volume of 50 to 60 mL of plasma and can be stored thus at 20 to 24 degrees C for up to 5 days. In vitro studies suggested that this plasma volume could be reduced to 30 to 35 mL without impairing platelet function. This study evaluated whether platelets stored for 5 days in a reduced volume (30-35 mL) of plasma maintained their in vivo viability, hemostatic function, and recovery in recipients. Paired autologous platelet survival studies were done in 20 adult volunteers to assess platelet viability. A rabbit ear bleeding-time model was used to compare the hemostatic effectiveness of human platelet concentrates stored for 5 days in the standard or reduced volume of plasma. Platelet recovery was compared in thrombocytopenic hospital patients. Paired platelet survival studies indicated no significant difference between the values in platelet concentrates stored for 5 days in the reduced volume of plasma and the values in those stored in the standard volume. In the animal model, there was no significant difference in the bleeding times achieved by either set of platelet concentrates. The platelet count increments in thrombocytopenic patients were measured. The platelet count increments in patients who received reduced-volume platelet concentrates were as good as the increments achieved in patients given standard-volume concentrates. The in vivo viability, recovery, and hemostatic function of platelets collected in polyvinylchloride plastic containers and stored in 30 to 35 mL of plasma for 5 days are maintained as well as those of platelets stored in 50 to 60 mL of plasma.

Recovery and survival in vivo of platelet concentrates prepared with prostaglandin E1.

In follow-up to previous studies showing that stimulators of adenylate cyclase inhibit the activation of platelets in platelet concentrates (PC), the posttransfusion recovery and survival of autologous platelets prepared and stored after the addition of prostaglandin E1 (PGE1) to platelet-rich plasma at a concentration of 1.3 X 10(-8) M were investigated. Six normal subjects were studied on the two occasions, using PC stored with and without PGE1 and radiolabeling with 51Cr. The mean recovery of platelets prepared with PGE1 (35.2 +/- 8.1%) was significantly lower (p less than 0.013) than that of routinely prepared platelet concentrates (46.3 +/- 9.4%). The mean life-spans of platelets prepared with and without PGE1 were 7.1 +/- 0.4 and 6.2 +/- 1.0 days, respectively (p = NS). Despite its ability to inhibit the activation of platelets during concentration and storage, prostaglandin E1 appears to reduce posttransfusion recovery of platelets significantly in this experimental model and cannot be recommended at this time as an adjunct for PC preparation.

Donor variables affecting survival of autologous platelets.

While platelet survival studies have been carried out by numerous laboratories for many years, general agreement has not been reached on a single method or for the value of this test. Available data indicate that in spite of certain difficulties, reliable comparisons can be obtained using relatively small numbers of donors. Indeed, a difference in platelet survival of as little as 10 percent can be detected by using eight donors, whereas only four donors are required if one wishes to detect a 20 percent change. Should studies be done using donors preselected according to strict criteria of age, sex, health, etc.? It might be that less scatter among the data points would be observed and perhaps even fewer donors would be required to obtain significant values. In surveying the available information, it is clear that many investigators do have data on normal controls which could be extracted and analyzed to provide an answer to this question. Such information would be of great value in determining the criteria for selection of donors for autologous platelet survival studies.

The relationship among platelet-associated IgG, platelet lifespan, and reticuloendothelial cell function

Platelet-associated IgG (PAIgG) has been reported to be elevated in nonthrombocytopenic patients who have a normal platelet lifespan. This has been interpreted as indicating that PAIgG is a nonspecific finding in these patients and not a determinant of platelet survival. It is important to recognize that the reticuloendothelial (RE) system plays an important role in the clearance of antibody-sensitized cells. In this study, we related the level of PAIgG and the platelet lifespan to the RE function in patients with: (A) idiopathic thrombocytopenic purpura (ITP), and (B) five patients with elevated levels of PAIgG yet normal or near-normal platelet counts. RE function was assessed by measuring the clearance of autologous chromium-labeled red cells sensitized with a precise amount of alloantibody (2,000–3,600 molecules of IgG/cell). Eight patients with immune thrombocytopenia had significantly shortened platelet survivals (less than 2–113 hr). In contrast, the five patients with elevated PAIgG, yet normal or near- normal platelet counts, all had normal autologous platelet survivals (186–222 hr). These patients also had significantly impaired clearance of IgG-sensitized red cells, with an average of 85% of the infused red cells remaining in the circulation at 60 min (normal 42% +/- 14%, n = 10). In this study, every patient with elevated PAIgG and normal RE function had a shortened platelet lifespan. Those patients with elevated PAIgG and impaired RE function did not invariably have a shortened platelet lifespan. The observation that the PAIgG is elevated in some patients whose platelet survival is normal does not indicate that PAIgG is not biologically relevant. It indicates that these patients may have RE blockade and do not clear IgG-sensitized cells.

The Relationship Among Platelet-Associated IgG, Platelet Lifespan, and Reticuloendothelial Cell Function

Platelet-associated IgG (PAIgG) has been reported to be elevated in nonthrombocytopenic patients who have a normal platelet lifespan. This has been interpreted as indicating that PAIgG is a nonspecific finding in these patients and not a determinant of platelet survival. It is important to recognize that the reticuloendothelial (RE) system plays an important role in the clearance of antibody-sensitized cells. In this study, we related the level of PAIgG and the platelet lifespan to the RE function in patients with: (A) idiopathic thrombocytopenic purpura (ITP), and (B) five patients with elevated levels of PAIgG yet normal or near-normal platelet counts. RE function was assessed by measuring the clearance of autologous chromium-labeled red cells sensitized with a precise amount of alloantibody (2,000-3,600 molecules of IgG/cell). Eight patients with immune thrombocytopenia had significantly shortened platelet survivals (less than 2-113 hr). In contrast, the five patients with elevated PAIgG, yet normal or near-normal platelet counts, all had normal autologous platelet survivals (186-222 hr). These patients also had significantly impaired clearance of IgG-sensitized red cells, with an average of 85% of the infused red cells remaining in the circulation at 60 min (normal 42% +/- 14%, n = 10). In this study, every patient with elevated PAIgG and normal RE function had a shortened platelet lifespan. Those patients with elevated PAIgG and impaired RE function did not invariably have a shortened platelet lifespan. The observation that the PAIgG is elevated in some patients whose platelet survival is normal does not indicate that PAIgG is not biologically relevant. It indicates that these patients may have RE blockade and do not clear IgG-sensitized cells.

Separation of platelet-rich plasma by modified centrifugal elutriation.

The Beckman centrifugal elutriation (CE) system is modified for the separation of platelet-rich plasma (PRP) from human and rabbit blood. The Beckman separation chamber is found inadequate for this purpose, and a new chamber of conical shape has been developed. Optimal flow rate for separating PRP from whole blood with the new chamber of 11.3 ml capacity is 3.5 ml/min while centrifuging at 2500 rpm or 700 g. Collection process takes about 4 minutes. This new process is based on the principle of centrifugal counterflow displacement and filtration, and is different from the CE process which is based on counterflow centrifugation and differential elution. About 90% of total platelets are recovered with this new process. The collected samples are free of leucocytes and contained only a few erythrocytes. Platelets collected by either differential centrifugation (DC) or new procedures are found to be similar in morphological characteristics, both being discoidal. Other characteristics such as aggregation response induced by ADP or epinephrine, serotonin-14C secretion, and survival of autologous platelets in rabbits are also found to be similar. However, ATP release induced by ADP is consistently higher from platelets prepared by our procedure than from those prepared by the DC procedure.

712 SPLENECTOMY AND PROPHYLACTIC ANTIBIOTICS IN THE MANAGEMENT OF THE WISKOTT-ALDRICH SYNDROME (WAS)

The WAS, an x-linked disorder with the triad of recurrent infections, eczema, and thrombocytopenia with hemorrhage, is a difficult management problem. 1/3 of WAS patients die of thrombo-cytopenia with catastrophic intracranial hemorrhage the principal threat. Because of the experience that splenectomized WAS patients died within a few months of overwhelming sepsis, splenectomy has been considered relatively contraindicated. 18 splenectomized WAS patients were evaluated for their response in terms of hemostatic improvement and subsequent clinical course. 17 of the 18 patients (94%) had elevations of their platelet counts (pc) to normal or near normal levels with control of bleeding. The mean pc rose from 19 to 249 × 103/mm3. Autologous platelet survival became normal post splenectomy in the one patient studied. 7 of the 18 patients are alive with a mean survival of 8 years post splenectomy. 7 of the 7 survivors are on prophylactic antibiotics and have been free of septic complications while on antibiotics. Of the 9 patients who have died, only one was or long term antibiotic coverage which had been stopped 10 days before the onset of his fatal septic episode. Splenectomy appears to offer a useful therapeutic modality for controlling hemorrhage and increasing survival in WAS when combined with the use of prophylactic antibiotics. The critical requirement for continuous antibiotic coverage, however, cannot be overemphasized when considering this form of therapy.

EFFECT OF EXPERIMENTAL CYANOSIS ON PLATELET SURVIVAL

In order to determine the effect of cyanosis on platelet survival, experimental cyanosis was produced in dogs by anastomosing the left atrial appendage to the main pulmonary artery. The six cyanotic animals used in this study had arterial O2 saturations of 71%-85% and elevated hematocrits. By one month following surgery, the 51chromium-labeled autologous platelet half-life (PHL) decreased 15%-60% from preoperative values: two cyanotic dogs had progressive reduction of PHL at two and three months. Mo reduction in PHL occured in three sham operated control animals. Survival of platelets exchanged between cyanotic and control animals was determined. Platelets from cyanotic dogs studied in control animals had a 69%-87% shorter survival than the autologous PHL of the control animals, indicating an abnormality intrinsic to the platelet produced in the cyanotic dog. Normal platelets from control animals transfused into cyanotic dogs had the identical reduced survival of autologous platelets in that cyanotic animal, suggesting that some determinant of transfused platelet survival is extrinsic to the platelet. Three months after shunt closure in two dogs, the reduced PHL has persisted.

Effect of altitude exposure on platelets.

Since decompression from depth is known to produce a fall in platelet count, the effect of altitude decompression and high-altitude exposure on platelets was investigated. Sixteen subjects decompressed without hypoxia to 20,000 ft simulated altitude for two hours showed a significant (P less than 0.01) drop in circulating platelet count of approximately 10% for three days following decompression. Four of five subjects similarly exposed had a shortened autologous platelet survival compared to that prior to exposure. Subjects exposed to 9,800 ft and then 17,600 ft in a mountain environment showed a significant mean decrease in platelet count on day 2 of 7% and 25% respectively, which had returned to control by day 5. Nonhypoxic and hypoxic decompressed rabbits which received homologous chromium-51-labeled platelets had an increase in lung radioactivity compared with sea-level controls. It is postulated that altitude decompression produces platelet reductions similar to these seen after decompression from depth, and that platelets sequester in the pulmonary vascular bed.

Thrombocytosis: platelet kinetics in neoplasia.

Abstract Autologous platelet survival studies using 51 Chromium ( 51 Cr) as a label are reported for five patients with nonhematologic malignancies and associated thrombocytosis. All patients had platelet counts greater than 550,000 per microliter. The in vivo platelet disappearance was linear with a life-span of 6.0 to 7.4 days. The platelet turnover rate (platelet count divided by life-span) was increased 2 to 4 times that measured in 10 normal subjects. Base on these data, the thrombocytosis seen in association with neoplasia can be explained by an increase in platelet production. The in vivo survival of these labeled platelets is mildly shortened.

THE WISKOTT-ALDRICH SYNDROME: A GENETIC DEFECT FUNCTIONALLY EXPRESSED IN MARROW STEM CELL DERIATIVES

Three of four non-related boys presented with thrombocytopenia, eczema, bloody diarrhea and frequent infections. The fourth initially had thrombocytopenia only, was splenectomized, and subsequently developed repeated infections and eczema. Immunoglobulins were variably abnormal. Antibody production to bacteriophage OX 174 (a protein antigen) was abnormal with low primary and severely impaired secondary response. No IgG antibody was formed. Lymphocyte transformation with non-specific mitogens and allogeneic cells was significantly impaired and the number of E-rosettes diminished. Volumetric size of platelets was reduced to 50%. Except in the splenectomized patient, autologous platelet survival time was normal. In all patients, in vivo and in vitro platelet function when corrected for platelet size was normal. Since megakaryocyte mass was adequate, thrombocytopenia must result from ineffective thrombocytopoesis. Red blood cell (RBC) size was also reduced. The abnormal B and T-cell function, the ineffective platelet production and decreased size of platelets and RBC in this X-linked disease suggests that a single genetic defect is expressed functionally in all stem cell derivatives.

A modification of the technique for 51Cr-labelling of blood platelets giving increased circulating platelet radioactivity.

The influence of temperature, pH, incubation medium, and incubation time on the uptake of 51Cr by platelets was studied. The uptake of 51Cr proceeded for at least 4 hours, most rapid in a modified Ringer solution. The rate of uptake increased with temperature up to 37° C., with platelet number up to 1–2 times 106/μl. and with concentration of 51Cr, but was reduced by a surface‐active agent Triton WR 1339.Based on these observations, a modified technique for 51Cr‐labelling of platelets is presented. Provided the platelet count is normal, removal of only 120 ml. of blood from the patient is necessary. Even in severe thrombocytopenia, survival of autologous platelets can be estimated by the present method.