Von Willebrand factor multimer structure is neither acutely nor chronically affected by plateletpheresis.

BACKGROUND: Plateletpheresis (PltPh) exposes the donor's blood to artificial surfaces and mechanical forces such as shear stress and centrifugation. In terms of the donor's safety and the quality of the apheresis platelet concentrate (APC), possible impairment of platelet function due to PltPh should be excluded. Von Willebrand factor (VWF) plays a pivotal role in platelet adhesion and aggregation. VWF is a multimeric protein and can be damaged by adsorption or shear stresses. It is unclear whether VWF structure could be damaged during PltPh, leading to platelet dysfunction. METHODS: We analyzed VWF antigen (VWF:Ag), ristocetin cofactor (VWF:RCo), and VWF multimer structure immediately before and after apheresis in the donor and in the APC. These parameters and factor VIII activity (FVIII:C) and closure time using PFA-100 (CT) were also analyzed in blood samples taken from new donors before the first and before subsequent donations and from long-term donors. RESULTS: During apheresis, VWF:Ag falls by about 15% but the VWF multimer structure remains unchanged. In samples taken before subsequent donations, there was a tendency of VWF:Ag and FVIII:C to increase throughout the initial donations, but no alteration of multimer structure. Long-term donors, however, show a normal VWF multimer structure and normal concentrations of VWF:Ag, VWF:RCo, and FVIII:C. In some donors with low-normal VWF:Ag and VWF:RCo, PFA-100 CT was prolonged. CONCLUSIONS: VWF multimer structure is neither acutely nor chronically affected by plateletpheresis. A decrease in VWF:Ag with no functional damage only occurs acutely and can be explained by the withdrawal of plasma and dilution with the anticoagulant ACD-A due to apheresis.

'New' direct oral anticoagulants in the perioperative setting.

PURPOSE OF REVIEW: Out of the anesthetist's perspective, some uncertainties remain with the perioperative management of the so-called NOACs. This review emphasizes on the question of bleeding and thromboembolic risk as well as the management of bleedings and the discontinuing intervals in the context of regional anesthesia. RECENT FINDINGS: Managing patients with NOAC therapy, an interdisciplinary approach and consent with surgeons and specialist in hemostaseology has to be found. For severe and lifethreatening bleeding there are specific antidotes in development; however, until clinical provement is not yet finished the application of four-factor prothrombin complex concentrate may be the most promising approach. SUMMARY: NOACs like dabigatran etexilate, rivaroxaban, apixaban and edoxaban are effective alternatives to warfarin in primary and secondary prophylaxis of thromboembolic conditions. In the perioperative setting, some uncertainties and evidence gaps remain in estimating the bleeding risks associated with surgical procedures, emergency trauma and neuroaxial anesthesia. A discontinuation of NOACs should be at least 1 day before elective operation. Renal and liver impairment, older age, or co-medications could afford longer intervals. As no specific reversal agents are yet available for life-threatening bleeding or emergency surgery; nonspecific prohemostatic therapies are mainly recommended. Oral charcoal, application of tranexamic acid or hemodialysis could bring additional benefit depending on the individual NOAC. Practitioners need to be aware that NOACs can interfere in different pathways with the measurement of common hemostasis parameters. Estimating the bleeding risks and reversal strategies requires careful evaluation also in the light of a potential risk of thromboembolic complications. In difference to warfarin, 'bridging' concepts are not generally recommended for NOACs.

Travel habits and complications in patients treated with vitamin K antagonists: a cross sectional analysis.

BACKGROUND: Travel-related conditions have impact on the quality of oral anticoagulation therapy (OAT) with vitamin K-antagonists. No predictors for travel activity and for travel-associated haemorrhage or thromboembolic complications of patients on OAT are known. METHODS: A standardised questionnaire was sent to 2500 patients on long-term OAT in Austria, Switzerland and Germany. 997 questionnaires were received (responder rate 39.9%). Ordinal or logistic regression models with travel activity before and after onset of OAT or travel-associated haemorrhages and thromboembolic complications as outcome measures were applied. RESULTS: 43.4% changed travel habits since onset of OAT with 24.9% and 18.5% reporting decreased or increased travel activity, respectively. Long-distance worldwide before OAT or having suffered from thromboembolic complications was associated with reduced travel activity. Increased travel activity was associated with more intensive travel experience, increased duration of OAT, higher education, or performing patient self-management (PSM). Travel-associated haemorrhages or thromboembolic complications were reported by 6.5% and 0.9% of the patients, respectively. Former thromboembolic complications, former bleedings and PSM were significant predictors of travel-associated complications. CONCLUSIONS: OAT also increases travel intensity. Specific medical advice prior travelling to prevent complications should be given especially to patients with former bleedings or thromboembolic complications and to those performing PSM.

The place of new oral anticoagulants in travel medicine.

New oral anticoagulants are increasingly used instead of vitamin K antagonists or low molecular weight heparins. Hence, more individuals treated with new oral anticoagulants will seek travel medicine advice. Travel medicine experts should therefore become familiar with new oral anticoagulants and with their impact and role in travel medicine. This review summarizes pharmacological characteristics and approved indications of dabigatran, rivaroxaban and apixaban, and highlights their relevance for travellers on permanent oral anticoagulation and for the prophylaxis of travellers' thrombosis. Compared to vitamin K antagonists, the new oral anticoagulants have many advantages: they do not have interactions with food, they have lower potential for drug-drug interactions and do not require regularly performed laboratory tests. The oral administration, obviating the need to carry needles and syringes during travel may give the new oral anticoagulants a further advantage over low molecular weight heparins. Clinical experience with the new oral anticoagulants, however, is still rather limited and there is concern regarding the clinical management of patients treated with new oral anticoagulants who suffer from severe bleeding or who need urgent invasive procedures. Overall, it remains an individual decision based on a risk/benefit analysis as to whether or not patients on long-term treatment with vitamin K antagonists should be switched to new oral anticoagulants for intended travel. Further caution is also indicated so that the availability of orally administered new anticoagulants should not lead to undifferentiated and unjustified prescription of anticoagulants for the prophylaxis of traveller's thrombosis.

von Willebrand factor, clotting factors, and clotting inhibitors in apheresis platelet concentrates.

BACKGROUND: Apheresis platelet concentrates (APCs) are usually stored in citrated plasma at 22°C. The stability of coagulation proteins-von Willebrand factor (vWF), clotting factors (CFs), and their inhibitors-has often been described in association with the storage of thawed plasma. However, fewer data are available regarding changes in APCs. STUDY DESIGN AND METHODS: We measured CF activities and inhibitors in APCs on the day of manufacture (Day 0) and on Days 4, 5, and 7. vWF was determined by measuring vWF antigen (vWF:Ag) and vWF ristocetin cofactor (vWF:RCo) and by multimer analysis. RESULTS: Twenty-one PCs obtained by plateletpheresis were studied. Major changes were observed for Factor (F)VIII (37% loss of activity within 4 days), FV (20% within 4 days), and protein S (76% within 4 days). All other CF activities remained higher than 80% over the 7 days. Fibrinogen and the inhibitors antithrombin and protein C remained quite stable. FXI, FXII, and FXIII actually increased during storage (8, 11, and 12% within 4 days). vWF:Ag increased during storage of APCs by 2% per day, with a relative loss of vWF:RCo and high-molecular-weight multimers. CONCLUSION: Even after 7 days of storage at 22°C, the hemostatic potential of the plasma content in APCs was roughly preserved. The increase in FXII antigen indicates that this CF may also be stored in platelets; however, this has not yet been described.

Travel behaviour of patients with haemophilia.

BACKGROUND: We aimed to identify socio-demographic, or illness-specific variables, influencing travel behaviour of haemophilic patients. METHODS: A standardised questionnaire was sent to more than 2000 members of two German Haemophilia associations. Multivariable logistic regression with the outcomes frequent (at least two journeys per year) and long-haul travel (outside of Europe) was applied separately on adult patients and patients younger than 18 years. RESULTS: Among 345 adults, high education level, living in a partnership or travelling alone was significantly associated with frequent travel with odds ratios (ORs)/95%-confidence intervals (95%-CI) of 3.10/1.72-5.80, 1.99/1.10-3.62 and 1.73/1.01-3.62, respectively. High education level and self-application of clotting factors were significant variables for long-haul travel (OR/95%-CI: 2.45/1.43-4.26 and 3.25/1.33-8.52, respectively). Among 144 non-adults, a younger age or performing permanent prophylactic treatment was significantly associated with a lower likelihood for long-haul travel (OR/95%-CI: 0.51/0.22-0.95 and 0.10/0.01-0.65, respectively). Longer awareness of the disease increased the likelihood for long-haul travel (OR/95%-CI: 1.06/1.01-1.14). CONCLUSIONS: High education level and self-application of clotting factors influence travel intensity of adult patients most strikingly. Parents of very young patients on permanent prophylactic treatment might need special education to facilitate holiday travel for these families.

High resolution multimer analysis and the PFA-100 platelet function analyser can detect von Willebrand disease type 2A without a pathological ratio of ristocetin cofactor activity and von Willebrand antigen level.

BACKGROUND: The biological variability of von Willebrand factor and the variability in assays can make diagnosis and subclassification of von Willebrand disease (VWD) difficult. We describe a case series of four patients with a typical history of VWD and prolonged closure time in the platelet function analyser (PFA-100) but initially a normal ratio of ristocetin cofactor activity (VWF:RCo) to von Willebrand factor antigen levels (VWF:Ag) for whom further diagnostics verified VWD type 2A. METHODS: For the initial VWD diagnostics we measured VWF:Ag, VWF:RCo, platelet aggregation induced by ADP, ristocetin and collagen, closure time in the PFA-100 test, and platelet count. We used VWF multimer analysis and collagen binding capacity for extended diagnostics. VWD diagnostics were carried out as part of extensive laboratory screening to exclude other haemostatic defects. RESULTS: Multimer analysis revealed the absence of ultralarge multimers in all 4 patients. Ristocetin-induced platelet aggregation was consistently diminished in three patients with hereditary VWD 2A but not in a patient with essential thrombocythaemia. After repeat testing, diminished VWF:RCo and collagen binding capacity (VWF:CB) could be identified in all patients. However, all four cases would have been missed if the initial VWD assays had been performed only once. CONCLUSIONS: A single measurement of a normal ratio of VWF:RCo/VWF:Ag does not exclude VWD 2A in patients with a typical history of VWD. The PFA-100 is suitable for screening. To ensure that no cases of VWD are missed, multimer analysis and repeat functional testing of platelet aggregation, VWF:RCo, and VWF:CB are necessary.

Effects of immediate or delayed addition of platelet additive solution on the in vitro quality of apheresis platelets.

BACKGROUND: There is little knowledge how different hold times of hyperconcentrated platelet (PLT) suspensions (HPSs) before the addition of platelet additive solution (PAS) might affect PLT quality. We compared the in vitro quality of single-donor PLT concentrates (SDPs) with immediate or delayed PAS addition and studied the quality of collected concurrent plasma (CP). STUDY DESIGN AND METHODS: We collected 6×10(11) PLTs in 175 of mL plasma and CP from 31 donors. The HPSs were split into two parts, with 162 mL of modified PAS III (PAS-IIIM) added immediately (0hr-SDP) or 2 hours later (2hr-SDP). Final SDPs had a targeted concentration of 1.2×10(12) PLTs/L and a PAS proportion of 65%. On Days 1, 5, and 7 we determined glucose and lactate concentration, pH, P-selectin expression, hypotonic shock response (HSR), and extent of shape change (ESC). Clotting Factor V (FV) and VIII (FVIII) activities and D-dimer concentration were determined in CP and donor. RESULTS: Glucose utilization, lactate production, and pH were similar for both kinds of products. Low P-selectin expression indicated no relevant PLT activation during storage. HSR and ESC were similarly well preserved. Recoveries of FV and FVIII were 100.0±14.0 and 98.6±14.9%, respectively. Concentrations of D-dimers in the donor and CP were 173.7±90.1 and 177.6±91.2 ng/dL, respectively. CONCLUSIONS: Adding PAS immediately or 2 hours after collection does not result in different in vitro quality of PLTs stored up to 7 days. The good recovery of clotting factors with no signs of activation indicates a good quality of CP.

Centrifugation after irradiation of red blood cells does not accelerate haemolysis.

BACKGROUND: For intrauterine transfusion and some other rare indications, irradiation and washing or adjustment to an elevated haematocrit is necessary. No data are currently available indicating whether irradiation of red blood cell concentrates (RBCs) might impair the mechanical stability of erythrocytes during centrifugation leading to elevated haemolysis. Consequently, if irradiation and centrifugation of RBCs is necessary, there is no definitive recommendation about the preferred sequence of steps. METHODS: We divided 20 RBC units that were not older than 9 days into two subunits. These subunits were prepared to yield irradiated RBCs with an elevated haematocrit, as they are used for intrauterine transfusion. One subunit was centrifuged and then irradiated, the other subunit was irradiated and then centrifuged. The units were evaluated in vitro before preparation and on days 1 and 7. RESULTS: We could not find any difference in the haemolysis rate, extracellular LDH or alpha-HBDH between the two groups of RBCs. This observation indicates that centrifugation after irradiation of RBCs does not accelerate haemolysis. A similar ATP content in the two subunits demonstrated no difference in energy metabolism. The extracellular potassium concentration was significantly lower in the subunits washed after irradiation. CONCLUSIONS: There is no difference in the haemolysis caused by centrifugation between irradiated and non-irradiated RBCs. However, it is well known that washing RBCs after irradiation significantly lowers the potassium content. Summarising these two findings leads to the conclusion that it is optimal first to irradiate and then to wash RBCs.

Travelers' thrombosis--a state of practice in Germany.

BACKGROUND: Evidence-based guidelines to prevent travelers' thrombosis (TT) are still missing. We wanted to know whether travelers perceive the risk of TT, how they and their physicians cope with this in daily life, and whether recommended thrombosis prophylaxis (TP) was actually performed. METHODS: A standardized questionnaire (Q1) asking for age, gender, travel habits, and the assessment of the risk of TT was given to randomly incoming travelers seeking for travel medicine advice prior to long haul travel. A second questionnaire (Q3) focusing on the actually performed TP was answered by these travelers after return. The physician assessed travelers' thrombosis risk (TR) and gave specific recommendations for TP in questionnaire Q2. Besides analysis of age, gender, the awareness of the risk of TT, travelers' TR, duration, and kind of travel, we compared performed and recommended TP and analyzed the influence of relevant factors on TP. RESULT: A total of 315 travelers (43.3% male, aged 43.2 ± 15.9 y) took part in this survey. We received responses from 275, 309, and 248 travelers who answered Q1, Q2, and Q3, respectively. Travelers (91.6%) were aware of the risk of TT which was significantly higher among travelers aged 60 years and older. Travelers' TR had a significant influence on recommended and performed TP (p < 0.001). We found a moderate agreement between recommended and performed TP (kappa coefficient = 0.54). More travelers than recommended performed a specific TP (49.6% vs 39.8%) which was mainly done by the intake of acetylsalicylic acid (ASA). CONCLUSIONS: Travelers are well aware of the risk of TT and are compliant to perform at least the recommended TP for which physicians predominantly consider travelers' TR. The high rate of non-recommended intake of ASA and the different dosage regimes recommended for TP with ASA or heparin, however, indicate the need of better information for travelers and physicians.

Keys to open the door for blood donors to return.

Because of demographic changes, the worldwide shortage of blood will likely be aggravated in the foreseeable future. Hence, the retention of already active blood donors (BDs) is becoming more and more important. Moreover, a substantial increase in blood donations could be achieved by a relatively small increase in BD return. Blood donation services are therefore well advised to understand their BDs' motivations to become regular and committed BDs and to consider this in planning BD retention programs. Focusing on the published literature of the last decade, we summaries some key recommendations in considering BD retention strategies. Whereas starting a career as a BD is mainly driven by external stimuli, becoming a committed BD needs a well-developed identity role; that is, a BD with a high level of intrinsic motivation. Active communications with the BD right from the beginning, introducing distinct measures to support the development of a BD's distinct identity, increasing convenience of the blood donation process, having well-trained and motivated staff, applying distinct measures to reduce anxiety as well as adverse events, making BDs satisfied with their blood donation experience, appropriate use of incentives, quickly recapturing temporarily deferred BDs, and appealing to BDs' personal motivations and moral norms--all of these are major keys to achieving this important aim.

Thromboembolic risk assessment in a phenotypically cured factor-V-Leiden carrier after orthotopic liver transplantation.

BACKGROUND: The factor V Leiden mutation is a common genetic risk factor for thromboembolism. After liver transplantation, patients may present with an acquired factor V phenotype - genotype discrepancy. CASE REPORT: We present the history of a heterozygous carrier of the factor V Leiden mutation who needed liver transplantation because of coumarin-induced acute liver failure. This led to a phenotype - genotype discrepancy with apparent cure from the factor V Leiden carrier status. CONCLUSIONS: To date the thromboembolic risk assessment regarding the need for postoperative prophylactic anticoagulation in such patients has remained controversial with respect to the intracellular fraction of factor V in platelets. However, recent observations have shown that platelet factor V Leiden is endocytosed by megacaryocytes from plasma. Therefore, former assessments of an ongoing risk for thromboembolic events despite apparent cure of the factor V Leiden carrier status after liver transplantation should be corrected.