Roberto Mazzara

Experimental basis for the use of red cell transfusion in the management of anemic-thrombocytopenic patients

The Baumgartner perfusion technique was used as an experimental model to study the combined influence of red cell (RBC) and platelet counts on the interaction of platelets with the subendothelium. At normal hematocrit and a platelet count of 100,000 per microliter, platelet adhesion and platelet aggregate (PAG) formation on subendothelium were statistically decreased. At lower platelet counts (50,000/μliter), there was an even more marked reduction in the formation of PAGs. The critical role of RBCs was demonstrated in experiments at low hematocrit; the formation of PAGs was impaired in perfusions at 20 percent hematocrit at any platelet count tested. Platelet deposition on subendothelium was almost absent at 50,000 platelets per μliter, suggesting a negative synergistic effect for the association of low hematocrit (20%) with a low platelet count. Perfusion experiments carried out with nonanticoagulated blood drawn directly from anemic patients with mild thrombocytopenia (43,000–58,000 platelets/μliter) before and after RBC transfusion were in agreement with previous experiments that indicated that normalization of both platelet count and hematocrit is required to achieve optimum hemostasis. Our data give experimental support for the transfusional management of patients with anemia and thrombocytopenia.

Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome: a multivariate analysis of factors predicting the response to plasma exchange

The aim of this study was to investigate pretreatment prognostic factors that could be useful in predicting the response to plasma exchange in thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS). Thirty-two patients with TTP/HUS, treated with plasma exchange at our institution from 1980 to 1994, were studied. The main clinical and laboratory data at the beginning of plasma exchanges were analyzed by the Cox stepwise logistic regression, applied to either treatment failure or death. Seventeen (53%) patients attained a complete remission and 22 (69%) survived (five in advanced renal failure and long-term hemodialysis). Longer delay in initiating plasma exchanges, presence of stupor or coma, and higher creatinine levels at the beginning of plasma exchanges were independent predictors of treatment failure. Stupor or coma at the beginning of plasma exchanges was the only predictor of mortality from unremitted TTP/HUS. Hemoglobin levels, platelet count, and LDH activity, traditionally envisaged as markers of disease activity, neither correlated with previous duration of TTP/HUS nor had any prognostic value. Early diagnosis of TTP/HUS and prompt initiation of intensive plasma exchange emerged from this study as the most effective interventions for improving the prognosis of TTP/HUS patients.

Prevalence of hepatitis C virus infection in patients with antiphospholipid syndrome

BACKGROUND/AIMS The aim of this study was to determine the prevalence and clinical significance of hepatitis C virus (HCV) infection in patients with the antiphospholipid syndrome (APS). METHODS A series of 88 consecutive patients (78 female and 10 male), with a mean age of 39 years (range 15-79), was prospectively studied. All patients had been diagnosed with APS: 54 (61%) primary APS and 34 (39%) APS associated with systemic lupus erythematosus. A group of 200 apparently healthly blood donors was included in the study. Anti-HCV antibodies were investigated in the serum of all patients using a third-generation ELISA and confirmed by recombinant immunoblot assay. RNA-HCV was investigated in anti-HCV positive samples by polymerase chain reaction. Anticardiolipin, anti-beta2-glycoprotein I and antiprothrombin antibodies were evaluated by ELISA. Lupus anticoagulant was studied by coagulometric assays. RESULTS Only 2 (2.2%) patients showed positivity for anti-HCV antibodies, but none of them had clinical or biochemical signs of liver disease. Furthermore, RNA-HCV was not detected in serum of any of these patients. Lupus anticoagulant was positive in 57% of patients. Anticardiolipin antibodies were positive in 60% of patients, anti-beta2-glycoprotein I antibodies in 43% of patients, and antiprothrombin antibodies in 56% of patients. The prevalence of anti-HCV in blood donors was 1%. CONCLUSIONS The prevalence of anti-HCV in patients with APS is low and similar to that in healthy people in our area. HCV infection does not seem to be involved in the etiopathogenesis of this syndrome.

Platelet concentrates prepared and stored under currently optimal conditions: minor impact on platelet adhesive and cohesive functions after storage

BACKGROUND: The effect on platelets of two standard methods of platelet concentrate (PC) preparation was studied by flow cytometry. The findings were correlated with those obtained in an experimental in vitro perfusion model.

Platelet transfusions from D+ donors to D- patients: a 10-year follow-up study of 1014 patients

BACKGROUND: Current guidelines recommend that platelets (PLTs) from D− donors should be given to D− patients. However, such evidence comes from studies with a limited number of included patients that reported an incidence of anti‐D alloimmunization to be up to 19%. We thus decided to extend these findings by examining anti‐D alloimmunization at our institution, where PLT transfusions from D+ donors are transfused to D− patients because of logistic constraints.

Leukoreduced buffy coat–derived platelet concentrates photochemically treated with amotosalen HCl and ultraviolet A light stored up to 7 days: assessment of hemostatic function under flow conditions

BACKGROUND: Amotosalen plus ultraviolet A light photochemical treatment (PCT) inactivates high titers of bacteria, and other pathogens, in platelet concentrates (PCs) potentially allowing the storage of platelets (PLTs) for up to 7 days. Adhesion and aggregation of PLTs to injured vascular surfaces are critical aspects of PLT hemostatic function.

Effects of the addition of second-messenger effectors to platelet concentrates separated from whole-blood donations and stored at 4°C or –80°C

BACKGROUND: Platelet concentrates (PCs) are currently stored at 22°C under continuous agitation. Because of the potential risk of the overgrowth of bacteria in case of contamination, PC shelf life is limited to 5 days. A mixture of second‐messenger effectors is being evaluated to determine if it has benefits for cold liquid storage and cryopreservation of platelets.

Infusible platelet membranes improve hemostasis in thrombocytopenic blood: experimental studies under flow conditions.

BACKGROUND : The potential hemostatic effect of infusible platelet membranes (IPM; Cyplex, Cypress Bioscience) prepared from outdated human platelets is investigated.

In vitro Evaluation of the Hemostatic Effectiveness of Non Viable Platelet Preparations: Studies with Frozen‐Thawed, Sonicated or Lyophilized Platelets

Objectives: Because of the limited life span of platelets in regular storage systems, we were interested in investigating the effects on hemostasis of nonliving platelet derivatives. Methods: We evaluated the effects of different platelet preparations on primary hemostasis in a well‐established perfusion model. Studies were carried out with blood anticoagulated with low molecular weight heparin. Similar amounts of frozen‐thawed, sonicated or lyophilized platelets were added to normal blood or to blood which had been experimentally depleted of platelets. Platelet interaction with the subendothelium and fibrin deposition were morphometrically evaluated. Results: Addition of nonviable platelet preparations to thrombocytopenic blood always promoted a statistically significant increase in the deposition of fibrin on the subendothelium, but only lyophilized platelets retained some ability to interact with the subendothelium. Flow cytometry studies demonstrated the presence of GPIb, GPIIIa and P‐selectin on lyophilized platelets. Conclusions: Preparations containing nonviable platelets may still retain some hemostatic properties.

Platelet concentrates promote procoagulant activity: evidence from experimental studies using a perfusion technique

BACKGROUND: Evaluation of the hemostatic effectiveness of platelet transfusions is difficult. Perfusion methods have been employed to test the quality and function of platelet concentrates, allowing differentiation between platelet‐platelet and platelet‐surface interactions.