BACKGROUND:Triggering receptor expressed on myeloid cells-like transcript 1 (TLT-1), a platelet-specific α-granule protein, is implicated in hemostasis, but its regulation remains unclear. Platelet dysfunction contributes to trauma-induced coagulopathy (TIC) and thrombotic complications in trauma or mechanical circulatory support (MCS); however, underlying mechanisms remain poorly understood. OBJECTIVES:This study investigated the molecular mechanisms underlying soluble TLT (sTLT)-1 release and its role as a biomarker of platelet dysfunction in patients with severe trauma or receiving MCS. METHODS:TLT-1 dynamics on platelets exposed to glycoprotein (GP)VI ligand, coagulation, or shear stress in vitro were evaluated by ELISA and immunoblotting. sTLT-1 was measured in plasma from trauma or MCS-treated patients and healthy donors. Associations with TIC, injury severity, and mortality were assessed. RESULTS:Proteolysis of TLT-1 to release a 10- to 17-kDa fragment was metalloproteinase dependent and blocked by ADAM10 and ADAM17 inhibition. Unlike GPVI, platelet TLT-1 exposure increased following PAR-1 activation. sTLT-1 was elevated in trauma patients compared with controls and correlated with TIC (P < .05) and injury severity (P < .01). Receiver-operating characteristic analysis demonstrated discriminatory performance for TIC (area under the curve, 0.78; P = .011), with a Youden cutoff of 1.180 ng/mL yielding 89% sensitivity and 73% specificity. Platelet TLT-1 was basally expressed, mobilized 2.5-fold with activation, and shed in response to GPVI ligation and plasma recalcification. Shear-exposed platelets and plasma from MCS-treated patients exhibited elevated sTLT-1 levels. CONCLUSION:Unlike GPVI, TLT-1 increased on activated platelets and was regulated by ADAM10 and ADAM17. TLT-1 release is triggered by shear stress, GPVI ligands or activated factor X. Plasma sTLT-1 was associated with trauma severity and TIC.

Immune thrombotic thrombocytopenic purpura (iTTP), an autoimmune disorder characterised by thrombocytopenia and microangiopathic haemolytic anaemia, is associated with significant morbidity. The diagnosis is made when ADAMTS13 activity is <10% in conjunction with supporting clinical features. Treatment includes plasma exchange with immunosuppressive and anti-von Willebrand factor therapies. While diagnosis and management of acute iTTP are well established, our understanding of optimal monitoring during clinical remission remains incomplete. Clinical relapse of iTTP occurs most commonly within the first year of remission, however, there is little consensus as to the frequency of ADAMTS13 monitoring during clinical remission and when to intervene when there is ongoing deficiency. Through selecting studies that performed ADAMTS13 activity testing during clinical remission of iTTP we critically analyse the current research of ADAMTS13 monitoring during clinical remission and suggest areas for further research with a focus on clinically important outcomes.

Prior studies have suggested that immune thrombotic thrombocytopenic purpura (iTTP) may display seasonal variation; however, methodologic limitations and sample sizes have diminished the ability to perform a rigorous assessment. This 5-year retrospective study assessed the epidemiology of iTTP and determined whether it displays a seasonal pattern. Patients with both initial and relapsed iTTP (defined as a disintegrin and metalloprotease with thrombospondin type motifs 13 activity <10%) from 24 tertiary centers in Australia, Canada, France, Greece, Italy, Spain, and the US were included. Seasons were defined as: Northern Hemisphere-winter (December-February); spring (March-May); summer (June-August); autumn (September-November) and Southern Hemisphere-winter (June-August); spring (September-November); summer (December-February); autumn (March-May). Additional outcomes included the mean temperature in months with and without an iTTP episode at each site. A total of 583 patients experienced 719 iTTP episodes. The observed proportion of iTTP episodes during the winter was significantly greater than expected if equally distributed across seasons (28.5%, 205/719, 25.3%-31.9%; p = .03). Distance from the equator and mean temperature deviation both positively correlated with the proportion of iTTP episodes during winter. Acute iTTP episodes were associated with the winter season and colder temperatures, with a second peak during summer. Occurrence during winter was most pronounced at sites further from the equator and/or with greater annual temperature deviations. Understanding the etiologies underlying seasonal patterns of disease may assist in discovery and development of future preventative therapies and inform models for resource utilization.

Introduction: There have been only a few case reports of T/ megakaryocytic MPALs.We describe here a case of T/megakaryocytic MPAL in a child.Case report: A 10-year-old Chinese boy presented with fever for 1 week.Bone marrow immunophenotyping showed 71% blasts expressing CD34/CD117/CD33/CD11b/CD56/CD9/ HLA-DR/CD133.T-cell markers expressed included cytoplasmic CD3/CD7.Megakaryocyte markers, CD41a/CD61, were partially expressed.39% co-expressed cytoplasmic CD3/ CD41a.The case was concluded as MPAL with T/megakaryocytic differentiation.Molecular studies showed ETV6-FOXO1 rearrangement.He received 4 drug induction and chemotherapy based on high-risk acute lymphoblastic leukaemia protocol.He remains in remission 8 months after end of treatment.Discussion: Erythroid and megakaryocytic lineages are postulated to be the earliest to differentiate, so no cells with T and megakaryocytic differentiation potential would normally exist.Hence, WHO and EGIL do not include megakaryocytic and erythroid markers in lineage assignment criteria for MPAL.However, the concept of binary and irreversible lineage fate decisions is being challenged with recent studies suggesting megakaryocytes can be generated from multiple pathways, including from lymphoid precursors.ETV6-FOXO1 rearrangement has been reported in MPAL and is likely to contributory to the leukaemogenesis.It is important to consider the existence of this phenotype for further characterization to define the most appropriate treatment.

Paroxysmal nocturnal haemoglobinura is an acquired life-threatening haemolytic condition, which is generally well controlled with terminal complement blockade with eculizumab. Whilst almost all patients treated with terminal complement inhibitors develop extravascular haemolysis, only a small proportion of these results in symptomatic anaemia limiting their activities and requiring red cell transfusion. This case highlights the potential role for the C3 inhibitor, pegcetacoplan, in controlling both intravascular and extravascular haemolysis, and is the first case to report on the use of additional doses of pegcetacoplan to control breakthrough haemolysis.

Objectives: This study aimed to assess what diameter constitutes clinically-significant left common iliac vein (LCIV) compression in patients with May-Thurner syndrome (MTS). Materials and Methods: Nineteen patients with MTS were over a 10-year period. Minimum LCIV diameter was compared to 100 asymptomatic controls and 27 age- and gender-matched controls. Results: Mean LCIV diameter in MTS group was 3.82 mm (standard deviation [SD] 1.38), control group (mean 7.17 mm SD 3.19, P < 0.0001), and matched control group (mean 6.86 mm SD 3.03, P = 0.007). Statistical threshold analysis showed in MTS patients, a LCIV diameter of 4.7mm or less had an 87.5% sensitivity and 72.7% specificity for the diagnosis. Conclusions: Patients with MTS had a minimum LCIV diameter threshold of 4.7mm, and this can be used in correlating the diagnosis of MTS on computed tomography. However, minimum diameters less than 4.7 mm are also seen in the general population and as such compression alone does not constitute a diagnosis of MTS.

The increased understanding of the pathophysiology of both atypical hemolytic uremic syndrome (aHUS) and thrombotic thrombocytopenic purpura (TTP) in recent years has led to significant therapeutic advances for both conditions. These advances have placed an increased emphasis on a more rapid differentiation of both disorders which remain clinical diagnoses. In particular, recent data demonstrating the effectiveness of complement inhibition in patients with aHUS have increased the need for a more rapid and accurate differentiation of aHUS and TTP. Previously utilized criteria have used the presence or absence of neurologic or renal injury and the pretreatment ADAMTS13 activity to differentiate aHUS from TTP. The use of presenting clinical symptoms and findings alone to differentiate these conditions is problematic given their overlapping clinical presentations. Similarly, the use of the pretreatment ADAMTS13 activity alone to differentiate aHUS from TTP is also problematic, and could lead to the inappropriate witholding of plasma exchange (PEX) therapy. However, when used collectively, the pretreatment clinical findings (symptoms and laboratory data) and ADAMTS13 activity in the context of the patient's response to PEX therapy can allow for a more effective differentiation of these two disorders in a timely fashion that will allow for the prompt initiation of the most appropriate therapy.

Despite advances in design and materials, as well as pharmacological prophylaxis, hemostatic complications continue to plague device recipients. Ventricular assist devices (VADs) and extracorporeal membrane oxygenation (ECMO) are associated with bleeding that is not fully explained by anticoagulant or antiplatelet use. Exposure of platelets to elevated shear in vitro leads to increased shedding. We examined blood samples from patients with heart failure or in receipt of high fluid shear mechanocirculatory support to assess whether loss of platelet receptors occurs in vivo , and the relationship with acquired von Willebrand syndrome (AVWS) and changes in inflammatory cytokines. Platelet counts, levels of inflammatory cytokines IL-1β, IL-6, TNFα, MCP-1, IL-17A and IFNγ, coagulation tests and von Willebrand factor (VWF) analyses were performed on samples from 13 continuous flow VAD (CF-VAD), 14 ECMO, and 24 heart failure patients. Levels of platelet receptors were measured by flow cytometry or ELISA. The loss of high molecular weight VWF multimers was observed in 12 of 13 CF-VAD and 7 of 14 ECMO patients, consistent with AVWS. Platelet receptor shedding was demonstrated by elevated soluble glycoprotein (GP) VI levels in plasma and significantly reduced surface GPIbα and GPVI levels in CF-VAD and ECMO patients as compared with healthy donors. Platelet receptor levels were also significantly reduced in heart failure patients. Significant differences in levels of inflammatory cytokines monocyte-chemoattractant protein and tissue necrosis factor-a in a subset of patients with decompensated HF. These data link AVWS and increased platelet receptor shedding in patients with CFVADs or ECMO. Loss of the platelet surface receptors GPIbα and GPVI in heart failure, CFVAD and ECMO patients may be linked with extent of inflammation and may contribute to ablated platelet adhesion/activation, and limit thrombus formation under high/pathologic shear conditions.

Force-dependent binding of platelet glycoprotein Ib (GPIb) receptors to plasma von Willebrand factor (VWF) plays a key role in hemostasis and thrombosis. Previous studies have suggested that VWF activation requires force-induced exposure of the GPIb binding site in the A1 domain that is autoinhibited by the neighboring A2 domain. However, the biochemical basis of this “mechanopresentation” remains elusive. From a combination of protein chemical, biophysical, and functional studies, we find that the autoinhibition is controlled by the redox state of an unusual disulfide bond near the carboxyl terminus of the A2 domain that links adjacent cysteine residues to form an eight-membered ring. Only when the bond is cleaved does the A2 domain bind to the A1 domain and block platelet GPIb binding. Molecular dynamics simulations indicate that cleavage of the disulfide bond modifies the structure and molecular stresses of the A2 domain in a long-range allosteric manner, which provides a structural explanation for redox control of the autoinhibition. Significantly, the A2 disulfide bond is cleaved in ~75% of VWF subunits in healthy human donor plasma but in just ~25% of plasma VWF subunits from heart failure patients who have received extracorporeal membrane oxygenation support. This suggests that the majority of plasma VWF binding sites for platelet GPIb are autoinhibited in healthy donors but are mostly available in heart failure patients. These findings demonstrate that a disulfide bond switch regulates mechanopresentation of VWF.

The Serious Transfusion Incident Reporting program (STIR) commenced haemovigilance in relation to RhD immunoglobulin (Ig) administration in 2015. During two years of reporting, 21 reports relating to RhD Ig administration were received. Thirty-three percent (7/21) were related to omission of RhD Ig, putting women at risk of RhD alloimmunisation and adverse consequences in future pregnancies. A recent case reported to STIR highlights poor communication and misinterpretation of pathology results leading to significant morbidity from haemolysis in the fetus. STIR makes recommendations related to education of staff and communication between clinical and laboratory staff to improve the safety of patient care.

As treatment options in modern medicine continue to expand, physicians globally have witnessed a veritable explosion in the utility of therapeutic devices. Particularly within the spheres of cardiology and critical care medicine, a plethora of devices are now available with an ever-increasing range of clinical indications. Additionally, the advent of transcatheter-mounted devices has enabled patients unsuitable for more invasive procedures to benefit from intervention, thereby greatly expanding the cohort of device-eligible patients. However, despite advances in design and materials, as well as pharmacological prophylaxis, hemostatic complications continue to plague device recipients, contributing to morbidity and mortality. Elucidating the complex interplay between components of the hemostatic system and cardiac devices has been the subject of much recent research, with greater focus on the coagulation cascade and device-induced perturbations. However, less is known about impact of mechanical surfaces on platelets and the resultant clinical complications, both hemorrhagic and thrombotic. This review will focus on exploring the pathobiology of platelet-surface interactions, contextualized within the wider hemostatic system, with a focus on the increasingly utilized technologies of transcatheter aortic-valve implantation, ventricular assist devices, and extracorporeal membrane oxygenation.

HaemophiliaVolume 22, Issue 4 p. e345-e346 Letter to the Editor M1761K mutation in the von Willebrand factor A3 domain associated with impaired collagen binding and without platelet dysfunction D. M. Ong, D. M. Ong Department of Haematology, Alfred Health, Melbourne, Vic., AustraliaSearch for more papers by this authorH. Aumann, H. Aumann Department of Haematology, Alfred Health, Melbourne, Vic., AustraliaSearch for more papers by this authorR. K. Andrews, R. K. Andrews Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., AustraliaSearch for more papers by this authorE. E. Gardiner, E. E. Gardiner Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., AustraliaSearch for more papers by this authorS. E. Rodgers, S. E. Rodgers Haematology Division, SA Pathology, Adelaide, SA, AustraliaSearch for more papers by this authorA. K. Davis, Corresponding Author A. K. Davis Department of Haematology, Alfred Health, Melbourne, Vic., Australia Correspondence: Dr Amanda Davis, The Alfred Hospital, Commercial Rd, Prahran, Melbourne, Vic. 3181, Australia. Tel.: +61 3 9076 8008; fax: +61 3 9076 3424; e-mail: am.davis@alfred.org.auSearch for more papers by this author D. M. Ong, D. M. Ong Department of Haematology, Alfred Health, Melbourne, Vic., AustraliaSearch for more papers by this authorH. Aumann, H. Aumann Department of Haematology, Alfred Health, Melbourne, Vic., AustraliaSearch for more papers by this authorR. K. Andrews, R. K. Andrews Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., AustraliaSearch for more papers by this authorE. E. Gardiner, E. E. Gardiner Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., AustraliaSearch for more papers by this authorS. E. Rodgers, S. E. Rodgers Haematology Division, SA Pathology, Adelaide, SA, AustraliaSearch for more papers by this authorA. K. Davis, Corresponding Author A. K. Davis Department of Haematology, Alfred Health, Melbourne, Vic., Australia Correspondence: Dr Amanda Davis, The Alfred Hospital, Commercial Rd, Prahran, Melbourne, Vic. 3181, Australia. Tel.: +61 3 9076 8008; fax: +61 3 9076 3424; e-mail: am.davis@alfred.org.auSearch for more papers by this author First published: 28 June 2016 https://doi.org/10.1111/hae.12976Citations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume22, Issue4July 2016Pages e345-e346 RelatedInformation

Essentials Relationship of acquired von Willebrand disease (VWD) and platelet dysfunction is explored. Patients with ventricular assist devices and on extracorporeal membrane oxygenation are investigated. Acquired VWD and platelet receptor shedding is demonstrated in the majority of patients. Loss of platelet adhesion receptors glycoprotein (GP) Ibα and GPVI may increase bleeding risk.

In a previous issue of the British Journal of Anaesthesiaan important multicentre, randomized controlled trial was published comparing fibrinogen concentrate vsplacebo in patients undergoing complex cardiovascular surgery complicated by bleeding.1Rahe-Meyer N Levy J Mazer D et al.Randomised evaluation of fibrinogen versus placebo in complex cardiovascular surgery (REPLACE): a double-blind phase III study of haemostatic therapy.Br J Anaesth. 2016; 117: 41-51Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar This study showed a statistically significant increase in the use of blood products in those patients randomly assigned to receive fibrinogen concentrate. It provides additional important information to three recent publications that have shown no statistically significant benefit with the use of fibrinogen concentrate. This is an important study that will help to guide clinical practice and the design of future trials in bleeding patients with regard to the role of fibrinogen replacement. The standard of care to treat bleeding patients is variable around the world. However, the general principles are to replace red cells, clotting factors, and platelets lost with haemorrhage and manage any coagulopathy that occurs as a result of the underlying condition (e.g. disseminated intravascular coagulation in post-partum haemorrhage or trauma). Treatment can follow an approach whereby results are checked and deficiencies are replaced, or if the bleeding is too rapid and ongoing, without time to wait for results of testing, a ratio-based approach can be followed. There are many guidelines outlining the optimal approach, but a recent systematic review found little evidence to support one approach over another.2McQuilten ZK Crighton G Engelbrecht S et al.Transfusion interventions in critical bleeding requiring massive transfusion: a systematic review.Transfus Med Rev. 2015; 29: 127-137Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar Importantly, acquired hypofibrinogenemia can arise in the bleeding patient. In the developed world, fibrinogen replacement can be provided in the form of fresh frozen plasma (FFP), cryoprecipitate, or fibrinogen concentrate. A recent review of critical fibrinogen levels in bleeding identifies that ‘historically’ a fibrinogen threshold level of 1.0 g/L has been used to guide the need for supplementation, and the vast majority of current treatment guidelines use this level to trigger replacement.3Levy JH Welsby I Goodnough LT Fibriongen as a therapeutic target for bleeding: a review of critical levels and replacement therapy.Transfusion. 2014; 54: 1389-1405Crossref PubMed Scopus (215) Google Scholar In part, the trigger to replace fibrinogen has been guided by those unfortunate and rare patients who have congenital afibrinogenemia. In general, a target fibrinogen concentration of >1 g/L is effective in preventing bleeding in these patients while undergoing major surgery or with haemorrhage.4Bornikova L Peyvandi F Allen G et al.Fibrinogen replacement therapy for congenital fibrinogen deficiency.J Thromb Haemost. 2011; 9: 1687-1704Crossref PubMed Scopus (117) Google Scholar The available options for supplementing fibrinogen and a comparison of the different plasma products, cryoprecipitate, and fibrinogen concentrate have also recently been outlined.3Levy JH Welsby I Goodnough LT Fibriongen as a therapeutic target for bleeding: a review of critical levels and replacement therapy.Transfusion. 2014; 54: 1389-1405Crossref PubMed Scopus (215) Google Scholar In some countries, routine use of fibrinogen concentrate has already been adopted without robust clinical evidence, therefore this and other recent publications are welcomed in order to inform us of how best to manage patients who are bleeding with regard to fibrinogen supplementation. The search for a magic haemostatic agent has remained elusive, and while there were high expectations that recombinant factor 7a would be beneficial in the bleeding patient, numerous clinical trials did not show improved outcomes and raised concern regarding thromboembolic complications.5Yank V Tuohy CV Logan AC et al.Systematic review: benefits and harms of in-hospital use of recombinant factor VIIa for off-label indications.Ann Intern Med. 2011; 154: 529-540Crossref PubMed Scopus (199) Google Scholar,6O’Connell KA Wood JJ Wise RP Lozier JN Braun MM Thromboembolic adverse events after use of recombinant human coagulation factor VIIa.JAMA. 2006; 295: 293-298Crossref PubMed Scopus (576) Google Scholar Thus an important lesson was learned when the randomized controlled trials (RCTs) showed the drug to be non-efficacious in this clinical setting. In their study, Rahe-Meyer and colleagues1Rahe-Meyer N Levy J Mazer D et al.Randomised evaluation of fibrinogen versus placebo in complex cardiovascular surgery (REPLACE): a double-blind phase III study of haemostatic therapy.Br J Anaesth. 2016; 117: 41-51Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar report the results of an RCT where fibrinogen concentrate was compared with placebo for bleeding patients undergoing elective aortic surgery requiring cardiopulmonary bypass. Bleeding was measured as a 5-min bleeding mass of 60–250 g after separation from cardiopulmonary bypass and surgical haemostasis. A transfusion algorithm was then followed. The primary outcome was the number of allogeneic blood products (ABPs) used. A total of 519 of the 579 patients consented were randomized; of those, 152 had a bleeding mass >60 g and received fibrinogen concentrate or placebo. Unexpectedly, there was a greater need for allogeneic blood transfusion in the group randomized to receive fibrinogen concentrate. In the fibrinogen group, the median ABP use was 5 [interquartile range (IQR) 2.0–11.0] units compared with 3 (IQR 0.0–7.0) units in the placebo group (P= 0.026). In addition, among those receiving fibrinogen, fewer patients avoided postoperative transfusion [12/78 (15.4%)] compared with those receiving placebo [21/74 (28.4%)] (P= 0.047). The main difference in ABP transfused patients appeared to be the requirement for FFP rather than red cells or platelets (P= 0.017). Return to theatre for surgical bleeding was also higher in the fibrinogen concentrate group [6/78 (8%)] compared with placebo [3/74 (3%)]. In post hocexploratory analysis, the group assigned to receive fibrinogen required more postoperative transfusions, even when separately analysing patients where the transfusion algorithm was successfully followed. These results suggested a potentially adverse effect of fibrinogen concentrate on bleeding outcomes following complex cardiac surgery. A principal strength of this study is its multisite randomized design, which lends strong generalizability to the conclusions. The study is the largest randomized trial of fibrinogen concentrate in cardiac surgery. Cardiac surgical patients are a group who typically can utilize a large number of blood products and transfusion has been associated with worse outcomes7Feneck RO Anaemia and cardiac surgery.Anaesthesia. 2016; 71: 611-626Crossref PubMed Scopus (5) Google Scholar, therefore cardiac surgery patients seem to have been a good choice of patients to study. Three limitations in this study may have influenced the observed outcome. First, the inclusion criteria were designed to identify the subset of complex cardiac patients with early post-bypass haemorrhage by using a bleeding mass of 60–250 g during the first 5 min. This criterion, while immediate and practical, may not have identified patients most likely to benefit from supplemental fibrinogen and fails to consider the circulating fibrinogen level of the patient at the time of fibrinogen administration. Second, while a transfusion algorithm was followed, such algorithms are difficult to validate for effectiveness. The algorithm was followed in 68% of patients, and while there is some variability across study centres, the study was randomized and therefore the effect of this should be balanced across the two groups. Finally, data were not provided regarding the use of cell salvage or the number of patients receiving tranexamic acid, which may reduce bleeding in this patient group. In contrast to the use of fibrinogen concentrate as a treatment for bleeding, two previously published single-site RCTs examined the role of prophylactic fibrinogen concentrate in cardiac surgery. These studies have conflicting results. The single-centre Italian study by Ranucci and colleagues8Ranucci M Baryshnikova E Crapelli GB et al.Randomized, double-blinded, placebo-controlled trial of fibrinogen concentrate supplementation after complex cardiac surgery.J Am Heart Assoc. 2015; 4: e002066Crossref Scopus (118) Google Scholar found that when prophylactic fibrinogen concentrate, at a median dose of 4 g, was given to patients after complex cardiac surgery, they used fewer blood products: 39/58 (67.2%) patients in the fibrinogen concentrate group received no ABPs vs26/58 (44.8%) in the placebo group (P= 0.012). A Swedish study by Jeppson and colleagues9Jeppsson A Walden K Roman-Emanuel C Preoperative supplementation with fibrinogen concentrate in cardiac surgery: a randomized controlled study.Br J Anaesth. 2016; 116: 208-214Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar randomized patients undergoing cardiopulmonary artery bypass grafting to receive 2 g of fibrinogen concentrate prophylactically or placebo. The primary outcome was the mediastinal drain volume in the first 12 h postoperatively. Twenty-six patients were randomized to each arm. There was no statistical difference in the amount drained at 12 h in either group (median of 650 ml fibrinogen concentrate vs730 ml placebo; P= 0.29). There are several reasons why these studies may have varying results, including the slightly different patient groups, the larger dose in the more complex surgical group, and the different primary outcomes. As a result of these two studies, the question of optimal study design with relation to these factors is highlighted. Another patient group in whom bleeding can be a major problem is women with post-partum haemorrhage (PPH). In Denmark, Wikkelso and colleagues10Wikkelso AJ Edwards HM Afshari A et al.Pre-emptive treatment with fibrinogen concentrate for postpartum haemorrhage: randomized controlled trial.Br J Anaesth. 2015; 114: 623-633Abstract Full Text Full Text PDF PubMed Scopus (154) Google Scholar performed a multicentre RCT in 249 subjects with severe PPH. In this study they randomized patients to a single dose of 2 g of fibrinogen concentrate (in 100 ml sterile water) vsplacebo (100 ml saline). They hypothesized that the fibrinogen concentrate would reduce the need for red blood cell (RBC) transfusion in patients with PPH. The primary outcome was RBC transfusion up to 6 weeks post-partum. The mean blood loss was 1459 ml. Post-partum blood transfusion occurred in 25 (20%) of the fibrinogen group and 26 (22%) of the placebo group, which was not statistically significant. There was also no difference in the predefined secondary outcomes. Importantly, no thromboembolic events were noted, although the study was not powered to detect a difference in thromboembolic events. The baseline mean fibrinogen concentration was 4.5 g/l in both groups with only one patient in the fibrinogen concentrate group and four patients in the placebo group having a fibrinogen concentration <2 g/l. The study by Wikkelso and colleagues10Wikkelso AJ Edwards HM Afshari A et al.Pre-emptive treatment with fibrinogen concentrate for postpartum haemorrhage: randomized controlled trial.Br J Anaesth. 2015; 114: 623-633Abstract Full Text Full Text PDF PubMed Scopus (154) Google Scholar and that by Rahe-Meyer and colleagues1Rahe-Meyer N Levy J Mazer D et al.Randomised evaluation of fibrinogen versus placebo in complex cardiovascular surgery (REPLACE): a double-blind phase III study of haemostatic therapy.Br J Anaesth. 2016; 117: 41-51Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar would suggest that there is a threshold at which fibrinogen becomes crucial to haemostasis. Previous evidence, as outlined above, would suggest that this threshold is <1.0 g/l. This informs us that future studies assessing the role of fibrinogen concentrate should carefully consider inclusion criteria and that those patients without a low level of fibrinogen are unlikely to benefit from this therapy and indeed there may be unexpected adverse effects as demonstrated in this study. A fundamental question to resolve is whether one source of fibrinogen supplementation is better than another. Is fibrinogen concentrate more efficacious than cryoprecipitate? While it could be argued that there is limited evidence for the use of cryoprecipitate, this is considered standard practice in the setting of low fibrinogen and it would seem unethical to compare cryoprecipitate to placebo in an RCT of the bleeding patient with low fibrinogen. No prospective trials have compared the efficacy of these two products in the bleeding setting. While the later product requires thawing and no viral inactivation has occurred, both products are plasma derived and carry a theoretical risk of infectious disease transmission, even though this risk is extremely low. There is a misconception that cryoprecipitate exposes patients to a large number of donors, but each unit of cryoprecipitate is made from a single donor and therefore a treatment dose of 5–10 units exposes the patient to 5–10 donors. In comparison, fibrinogen concentrate is made from thousands of donors, and while the viral inactivation step (pasteurization) in production of this product adds additional safety compared with cryoprecipitate, the product is derived from many more donors. There is also the possibility of using virally inactivated plasma products, but the availability of these products depends on in which part of the world the patient resides.3Levy JH Welsby I Goodnough LT Fibriongen as a therapeutic target for bleeding: a review of critical levels and replacement therapy.Transfusion. 2014; 54: 1389-1405Crossref PubMed Scopus (215) Google Scholar Both products are derived from plasma and therefore the possible risk of variant Creutzfeldt–Jakob disease transmission from either product exists.11Yang L Stanworth S Baglin T Cryoprecipitate: an outmoded treatment?.Transfus Med. 2012; 22: 315-320Crossref PubMed Scopus (28) Google Scholar Unlike fibrinogen concentrate, cryoprecipitate contains several other clotting factors that may be beneficial in the haemorrhaging patient, such as von Willebrand factor, factor VIII, fibronectin, and factor XIII. In most countries, the production cost of cryoprecipitate is also likely to be less than that of fibrinogen concentrate. A randomized clinical trial comparing the efficacy of cryoprecipitate vsfibrinogen concentrate for patients with bleeding would help identify which of these products is superior in efficacy. If there is a logistical advantage in terms of time to deliver one product into the bleeding patient, then this will become apparent in a properly conducted RCT and we should not assume that one product is superior. A recent feasibility study has shown that it is possible to deliver cryoprecipitate within 90 min in 85% of study participants in the setting of haemorrhage in trauma.12Curry N Rourke C Ravenport R et al.Early cryoprecipitate for major haemorrhage in trauma: a randomised controlled feasibility trial.Br J Anaesth. 2015; 115: 76-83Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar Authorship of the study by Rahe-Meyer and colleagues1Rahe-Meyer N Levy J Mazer D et al.Randomised evaluation of fibrinogen versus placebo in complex cardiovascular surgery (REPLACE): a double-blind phase III study of haemostatic therapy.Br J Anaesth. 2016; 117: 41-51Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar also includes employees of CSL Behring and it was funded by CSL Behring. Designers of future studies will hopefully be able to convince the suppliers of these two different products that a clinical trial comparing the efficacies of these two products is important for patient care. Perhaps counterintuitively, this study informs us that the use of fibrinogen concentrate increased the use of blood products in the bleeding patient undergoing elective aortic surgery. A puzzling question is the mechanism by which fibrinogen concentrate led to increased blood product use. The study raises several other remaining questions, including the most appropriate clinical scenario in which fibrinogen replacement may be efficacious, whether cryoprecipitate may be a superior source of fibrinogen, and what the threshold for treatment and the proper dose should be. The study’s results should not only caution those clinicians who have adopted off-label use of fibrinogen concentrate, but also invite a re-examination of the evidence in those countries where it is already approved. The author gratefully acknowledges Dr Sunny Dzik for his critical review of this manuscript.

We present management strategies utilised for the first case of an urgent live-donor ABO incompatible B blood group renal transplant, in a patient with a prior A blood group lung transplant for cystic fibrosis. Three years on, renal function is excellent and stable, whilst lung function has improved.

Background: Virchow's triad identifies the three principle parameters driving haemostasis and thrombosis as: i. Changes in vessel wall properties and exposure of subendothelial matrix proteins; ii. Presentation of blood borne chemical activators (hypercoaguability); and iii. Blood-flow dependent mechanical factors (haemodynamics). Studies identifying a key role for micro-scale shear gradients in driving the earliest stages of platelet thrombus formation have informed the development of a novel set of microfluidic devices that have potential utility as rapid and efficient screening tools of shear dependent platelet function.A im: The aim of this project was to undertake a small scale clinical and laboratory based characterisation study of a microfluidic platform designed by us and to assess its ability to identify differences in platelet aggregation dynamics in citrated whole blood taken from control subjects and subjects with clinically diagnosed or undiagnosed von Willebrand disease (Types 1, 2 and 3).Method: Patients with VWD were recruited from the haemophilia outpatient clinic, Alfred hospital. Whole blood samples (250mL) or samples treated ex vivo to block the canonical platelet amplification loop pathways were perfused at a defined flow rate (45ml/mL) through a set of well defined micro-shear gradient geometries pre-coated with purified VWF to initiate platelet capture. Microfluidic geometries were characterised by an entry shear rate of 1,800.s-1, that was accelerated to a peak shear rate of either 45,000.s-1 or 150,000.s-1, returning to an exit shear rate of 1,800.s-1. The rate of initial shear acceleration was varied using a series of geometries with contraction entry angles varying from 15 - 85o.Results: The microfluidic platform was able to identify patients with Types 1 (VWF antigen < 30%), 2A and 3 VWD. ROC analysis of control versus VWD samples determined that the device sensitivity approached 94.4%, with a specificity of 100% for VWD. A statistically significant difference (p< 0.05) was observed when comparing control blood samples to type 1VWD (p< 0.001) and type 2A VWD samples (p=0.004), with both subtypes showing minimal to no platelet aggregation in the device. Patients presenting with bleeding symptoms but found not to have VWD (normal VWF:Ag levels) showed no significant difference (p=0.907) to controls. Furthermore, exogenous titration of Type 3 (n=2) VWD blood samples with purified VWF (10 - 100mg/mL) recapitulated platelet aggregation in a concentration dependent manner. Head to head comparison with standard laboratory based tests including, VWF:Ag, VWF:CB and VWF:RCo demonstrated a strong linear correlation with device output. In addition, time-course (0, 2 and 4 Hrs) trials demonstrate that the device is a sensitive measure of DDAVP treatment of VWD.Conclusion: The Studies presented demonstrate that haemodynamically sensitive platelet aggregation within our prototype platform is critically dependent on blood VWF antigen levels and demonstrates good proof-of-concept that the microfludic can selectively identify VWD dependent defects in whole blood platelet aggregation. Taken together these data suggest that a microfluidic platform with discrete haemodynamic control can operate as a sensitive screen for VWD. Future studies will focus on defining the particle and key haemodynamic parameters that shift both device selectivity and sensitivity.Disclosures No relevant conflicts of interest to declare.