Acquired disorders of platelet function

Pharmacological activation of constitutive androstane receptor induces female-specific modulation of hepatic metabolism

Background & Aims

The constitutive androstane receptor (CAR) is a nuclear receptor that binds diverse xenobiotics and whose activation leads to the modulation of the expression of target genes involved in xenobiotic detoxification and energy metabolism. Although CAR hepatic activity is considered to be higher in women than in men, its sex-dependent response to an acute pharmacological activation has seldom been investigated.

Methods

The hepatic transcriptome, plasma markers, and hepatic metabolome, were analysed in Car+/+ and Car-/- male and female mice treated either with the CAR-specific agonist 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) or with vehicle.

Results

Although 90% of TCPOBOP-sensitive genes were modulated in a sex-independent manner, the remaining 10% showed almost exclusive female liver specificity. These female-specific CAR-sensitive genes were mainly involved in xenobiotic metabolism, inflammation, and extracellular matrix organisation. CAR activation also induced higher hepatic oxidative stress and hepatocyte cytolysis in females than in males. Hepatic expression of flavin monooxygenase 3 (Fmo3) was almost abolished and was associated with a decrease in hepatic trimethylamine-N-oxide (TMAO) concentration in TCPOBOP-treated females. In line with a potential role in the control of TMAO homeostasis, CAR activation decreased platelet hyper-responsiveness in female mice supplemented with dietary choline.

Conclusions

More than 10% of CAR-sensitive genes are sex-specific and influence hepatic and systemic responses such as platelet aggregation. CAR activation may be an important mechanism of sexually-dimorphic drug-induced liver injury.

Impact and implications

CAR is activated by many drugs and pollutants. Its pharmacological activation had a stronger impact on hepatic gene expression and metabolism in females than in males, and had a specific impact on liver toxicity and trimethylamine metabolism. Sexual dimorphism should be considered when testing and/or prescribing xenobiotics known to activate CAR.

Pharmacological Strategies for Stroke Intervention: Assessment of Pathophysiological Relevance and Clinical Trials

OBJECTIVES

The present review describes stroke pathophysiology in brief and discusses the spectrum of available treatments with different promising interventions that are in clinical settings or are in clinical trials.

METHODS

Relevant articles were searched using Google Scholar, Cochrane Library, and PubMed. Keywords for the search included ischemic stroke, mechanisms, stroke interventions, clinical trials, and stem cell therapy.

RESULTS AND CONCLUSION

Stroke accounts to a high burden of mortality and morbidity around the globe. Time is an important factor in treating stroke. Treatment options are limited; however, agents with considerable efficacy and tolerability are being continuously explored. With the advances in stroke interventions, new therapies are being formulated with a hope that these may aid the ongoing protective and reparative processes. Such therapies may have an extended therapeutic time window in hours, days, weeks, or longer and may have the advantage to be accessible by a majority of the patients.

Multivisceral Transplant in a Patient With Portopulmonary Hypertension: A Case Report

Portopulmonary hypertension, a type of pulmonary arterial hypertension in the setting of cirrhotic or noncirrhotic portal hypertension, is associated with elevated morbidity and mortality during and after transplantation. Uncontrolled portopulmonary hypertension may prevent or delay listing for transplant candidates, and the prognosis without treatment and ultimately transplant is extremely poor. We present a 29-year-old White woman, who had a post-liver transplant at infancy due to biliary atresia. Later on, she developed extensive portal vein thrombosis and portopulmonary hypertension and underwent a multivisceral transplant (liver, stomach, pancreaticoduodenal complex, and small and large intestine). Preoperative mean pulmonary artery pressure was <30 mm Hg with a pulmonary vascular resistance of <300 dynes^.s/cm⁵ on oral sildenafil and intravenous epoprostenol. Intraoperatively, management required comprehensive transfusion protocols, a careful balance between correcting blood loss and preventing thrombosis. Intravenous epoprostenol, sildenafil, milrinone, and inhaled nitric oxide were used to reduce elevated mean pulmonary artery pressure and right ventricular strain associated with vascular clamping, reperfusion, and massive fluid shifts. Nitric oxide and epoprostenol use unleashed antiplatelet effects on a patient already susceptible to coagulopathy. A multimodal and multidisciplinary approach continued throughout the surgery and in the postoperative period, which led to a successful outcome.

Diagnosis of Platelet Function Disorders: A Challenge for Laboratories

In patients with normal plasmatic coagulation and bleeding tendency, platelet function defect can be assumed. Congenital platelet function defects are rare. Much more commonly they are acquired. The clinical bleeding tendency of platelet function defects is heterogeneous, which makes diagnostic approaches difficult. During the years, a large variety of tests for morphological phenotyping and functional analysis have been developed. The diagnosis of platelet function defects is based on standardized bleeding assessment tools followed by a profound morphological evaluation of the platelets. Platelet function assays like light transmission aggregation, luminoaggregometry, and impedance aggregometry followed by flow cytometry are commonly used to establish the diagnosis in these patients. Nevertheless, despite great efforts, standardization of these tests is poor and in most cases, quality control is lacking. In addition, these tests are still limited to specialized laboratories. This review summarizes the approaches to morphologic phenotyping and platelet testing in patients with suspected platelet dysfunction, beginning with a standardized bleeding score and ending with flow cytometry testing. The diagnosis of a functional defect requires a good collaboration between the laboratory and the clinician.

The utility of therapeutic plasma exchange in Hyperviscosity syndrome associated with juvenile rheumatoid arthritis: A case report

Hyperviscosity syndrome (HVS) is a life-threatening syndrome caused by high concentrations of large plasma proteins like IgM, rheumatoid factor, and other immune complexes, leading to increased blood viscosity and symptoms such as visual abnormalities, neurological impairment, bleeding diathesis, and thrombosis. While Waldenström's macroglobulinemia accounts for 80% to 90% of cases, HVS may develop in other clinical settings characterized by elevations in plasma proteins. Limited evidence currently exists describing the safety and efficacy of therapeutic plasma exchange (TPE) for the management of HVS secondary to non-neoplastic conditions. We report a case of recurrent HVS associated with juvenile rheumatoid arthritis and Felty syndrome that demonstrated improvement in clinical symptoms following initiation of TPE. These findings suggest that TPE may be utilized as an adjunct treatment option in patients with HVS secondary to autoimmune disorders.

Thrombocytopenia: Effect in Ischemic and Hemorrhagic Stroke

BACKGROUND

There are 2 classification of strokes: ischemic, if caused by an arterial occlusion from a clot or obstruction by atherosclerosis, and hemorrhagic, if caused by the rupture of a vessel and subsequent bleeding. Each type of stroke is influenced by platelet counts and platelet function. The intention of this article is to discuss the role of the platelet in the pathophysiology of acute stroke processes. This serves as a prelude to discussing these processes as disrupted with thrombocytopenia (low platelet counts). Platelets initiate clot formation and obstruct blood flow through the creation of a platelet plug. They also extend the penumbra in ischemic and hemorrhagic strokes. Thrombocytopenia can be a causal factor in an ischemic stroke, a risk factor for hemorrhagic stroke, and a risk factor for hemorrhagic stroke conversion.

METHODS

The aims of this study were to review 1 case study that illustrates the pivotal role of the platelet in strokes and to review the aspect that was impacted by autoimmune thrombocytopenia.

DISCUSSION

Thrombocytopenia is a hematologic disorder not often included in stroke care discussions. Thrombocytopenia sets up strokes to occur and, paradoxically, may also set the patient up for bleeding complications in the brain or groin.

CONCLUSION

Acknowledging the impact of both platelet and thrombocytopenia on stroke causation, stroke interventions, and outcomes is a pivotal aspect of comprehensive stroke care. Platelet function processes are impactful in each point of the continuum of stroke care, prevention, intervention, and discharge.

Direct oral anticoagulants in patients with hematologic malignancies

The anticoagulant treatment for patients with hematologic malignancies is low molecular weight heparin (LMWH), which is considered the safest in this particular patients setting. Although direct oral anticoagulants (DOACs) have proven their efficacy and safety in patients with cancer, their use can be challenging in patients with hematologic malignancies due to the peculiarity of these neoplasms: high thrombotic risk, possible onset of thrombocytopenia and concomitant anticancer therapies. The aim of our study was to evaluate the efficacy and safety of DOACs for venous thromboembolism or atrial fibrillation in patients with hematologic malignancies and plasmatic DOACs level during anticancer therapy and at time of bleeding or thrombotic complications. We evaluated patients with hematologic malignancies treated with DOACs for venous thromboembolism or atrial fibrillation-therapy was maintained until the platelet count was ≥50 × 10⁹ /L. In case of concomitant anticancer treatment and haemorrhagic or thrombotic events, we checked DOACs plasma levels (trough and peak). The patients evaluated were 135: 104/135 were on anticancer therapy. We did not observe either thrombotic or major haemorrhagic adverse events. Minor bleedings occurred in 10 patients and clinical relevant non-major (CRNM) in two patients. There was a statistically significant correlation between bleedings and myelodysplastic syndrome. DOACs resulted effective and safe in patients with hematologic malignancies. DOACs plasma level can be helpful in suggesting an early dose adjustment to prevent haemorrhagic adverse event in patients on concomitant anticancer therapy. Larger prospective studies including hematologic patients are warranted to confirm the safety and efficacy of DOACs.

Platelet Disorders

After vascular injury and exposure of subendothelial matrix proteins to the intravascular space, mediators of hemostasis are triggered and allow for clot formation and restoration of vascular integrity. Platelets are the mediators of primary hemostasis, creating a platelet plug and allowing for initial cessation of bleeding. Platelet disorders, qualitative and quantitative, may result in bleeding signs and symptoms, particularly mucocutaneous bleeding such as epistaxis, bruising, petechiae, and heavy menstrual bleeding. Increasing evidence suggests that platelets have functional capabilities beyond hemostasis, but this review focuses solely on platelet hemostatic properties. Herein, normal platelet function as well as the effects of abnormal function and thrombocytopenia are reviewed.

Expert consensus on the diagnosis and treatment of thrombocytopenia in adult critical care patients in China

Thrombocytopenia is a common complication of critical care patients. The rates of bleeding events and mortality are also significantly increased in critical care patients with thrombocytopenia. Therefore, the Critical Care Medicine Committee of Chinese People's Liberation Army (PLA) worked with Chinese Society of Laboratory Medicine, Chinese Medical Association to develop this consensus to provide guidance for clinical practice. The consensus includes five sections and 27 items: the definition of thrombocytopenia, etiology and pathophysiology, diagnosis and differential diagnosis, treatment and prevention.

Diagnosis and Management of Heavy Menstrual Bleeding and Bleeding Disorders in Adolescents

IMPORTANCE

Heavy menstrual bleeding is a common cause of anemia and reduced quality of life in adolescents. There is a higher prevalence of bleeding disorders in girls with heavy menstrual bleeding than in the general population. Pediatricians should be comfortable with the initial evaluation of heavy menstrual bleeding and the indications for referral to subspecialty care.

OBSERVATIONS

The most common cause of heavy menstrual bleeding in adolescents is ovulatory dysfunction, followed by coagulopathies. The most common inherited bleeding disorder is von Willebrand disease, and its incidence in adolescents with heavy menstrual bleeding is high. Distinguishing the etiology of heavy menstrual bleeding will guide treatment, which can include hemostatic medications, hormonal agents, or a combination of both. Among hormonal agents, the 52-mg levonogestrel intrauterine device has been shown to be superior in its effect on heavy menstrual bleeding and is safe and effective in adolescents with bleeding disorders.

CONCLUSIONS AND RELEVANCE

Anemia, need for transfusion of blood products, and hospitalization may be avoided with prompt recognition, diagnosis, and treatment of heavy menstrual bleeding, especially when in the setting of bleeding disorders. Safe and effective treatment methods are available and can greatly improve quality of life for affected adolescents. A multidisciplinary approach to the treatment of girls with bleeding disorders and history of heavy menstrual bleeding is optimal.

Acquired platelet function disorders

The possibility of an acquired platelet function disorder should be considered in patients who present with recent onset muco-cutaneous bleeding. Despite the availability of newer and faster platelet function assays, light transmission aggregometry (LTA) remains the preferred diagnostic test. This review examines and discusses the causes of acquired platelet dysfunction; most commonly drugs, dietary factors, medical disorders and procedures. In addition to well-known antiplatelet therapies, clinicians should be alert for newer drugs which can affect platelets, such as ibrutinib. There is little clinical trial evidence to guide the management of acquired platelet function defects, but we summarise commonly employed strategies, which include addressing the underlying cause, antifibrinolytic agents, desmopressin infusions, and in selected patients, platelet transfusions.

The Effect of Oxidant Hypochlorous Acid on Platelet Aggregation and Dityrosine Concentration in Chronic Heart Failure Patients and Healthy Controls

Background and objective: One of the reasons for thrombosis in chronic heart failure (CHF) might be reactive forms of oxygen activating platelets. The aim of this study was to evaluate the effect of oxidant hypochlorous acid (HOCl) on platelet aggregation and dityrosine concentration in CHF patients and healthy controls. Materials and Methods: CHF patients (n = 67) and healthy (n = 31) were investigated. Heart echoscopy, 6-min walking test, complete blood count, platelet aggregation, and dityrosine concentration were performed. Platelet aggregation and dityrosine concentration were measured in plasma samples after incubation with different HOCl concentrations (0.15, 0.0778, and 0.0389 mmol/L). Results: Platelet aggregation without oxidant was lower (p = 0.049) in CHF patients than in controls. The spontaneous platelet aggregation with oxidant added was higher in CHF patients (p = 0.004). Dityrosine concentration was also higher (p = 0.032) in CHF patients. Platelet aggregation was the highest in samples with the highest oxidant concentration in both healthy controls (p = 0.0006) and in CHF patients (p = 0.036). Platelet aggregation was higher in NYHA III group in comparison to NYHA II group (p = 0.0014). Concentration of dityrosine was significantly higher in CHF samples (p = 0.032). The highest concentration of dityrosine was obtained in NYHA IV group samples (p < 0.05). Intensity of platelet aggregation, analyzed with ADP, was correlated with LV EF (r = 0.42, p = 0.007). Dityrosine concentration was correlated with NYHA functional class (r = 0.27, p < 0.05). Conclusions: The increase in platelet aggregation in CHF and healthy controls shows the oxidant effect on platelets. The increase in dityrosine concentration in higher NYHA functional classes shows a higher oxidative stress in patients with worse condition.

Acquired von Willebrand syndrome and impaired platelet function during venovenous extracorporeal membrane oxygenation: Rapid onset and fast recovery

BACKGROUND

Bleeding contributes to the high mortality of venovenous extracorporeal membrane oxygenation (vvECMO). The development of acquired von Willebrand syndrome (AVWS) has been identified as relevant pathology during ECMO. This study was performed to determine the onset of AVWS after implantation and the recovery of von Willebrand factor (VWF) parameters after explantation of ECMO in a large cohort of patients.

METHODS

VWF parameters of 59 patients treated with vvECMO at a university ECMO center were obtained before ECMO implantation, during therapy, and after explantation. In a subgroup of patients, light transmission aggregometry of platelets and flow-cytometric quantification of platelet granule secretion were performed.

RESULTS

All patients developed severe AVWS hours after implantation of vvECMO. After explantation, AVWS recovered within 3 hours in 60%, within 6 hours in 86%, and in all patients within 1 day. Aggregometry showed hypoaggregability of platelets after stimulation with ADP, ristocetin, collagen, and epinephrine. Flow-cytometric platelet analyses revealed severely reduced expression of CD62 and CD63.

CONCLUSIONS

All patients during vvECMO support rapidly develop AVWS and platelet dysfunction, resulting in severe impairment of coagulation. After explantation, AVWS overwhelmingly recovers within hours, resulting in a hypercoagulative state. These findings augment the need for novel extracorporeal technologies with reduced shear stress, and shift the emphasis for intense anti-coagulation during ECMO instead to a time-point after explantation.

Targeted Thromboelastographic (TEG) Blood Component and Pharmacologic Hemostatic Therapy in Traumatic and Acquired Coagulopathy

Trauma-induced coagulopathy (TIC) is a recently described condition which traditionally has been diagnosed by the common coagulation tests (CCTs) such as prothrombin time/international normalized ratio (PT/INR), activated partial thromboplastin time (aPTT), platelet count, and fibrinogen levels. The varying sensitivity and specificity of these CCTs have led trauma coagulation researchers and clinicians to use Viscoelastic Tests (VET) such as Thromboelastography (TEG) to provide Targeted Thromboelastographic Hemostatic and Adjunctive Therapy (TTHAT) in a goal directed fashion to those trauma patients in need of hemostatic resuscitation. This review describes the utility of VETs, in particular, TEG, to provide TTHAT in trauma and acquired non-trauma-induced coagulopathy.

Acquired platelet disorders

In contrast to congenital platelet disorders, which are rare, acquired platelet dysfunctions are more common in clinical practice. Their main causes are medications and systemic/hematologic diseases. Typical clinical manifestations are mucosal bleeding, epistaxis, or superficial epidermal bleeding normally of modest entity. In most cases, the molecular mechanisms underlying impaired platelet function are not fully established, making it difficult to optimize patient care. We here provide a short overview of the various forms of acquired platelet disorders, with a particular focus on recent mechanistic studies on platelet dysfunction in von Willebrand disease.

Epistaxis as a Common Presenting Symptom of Glanzmann's Thrombasthenia, a Rare Qualitative Platelet Disorder: Illustrative Case Examples

Children often present to emergency departments (EDs) with uncontrollable nose bleeding. Although usually due to benign etiologies, epistaxis may be the presenting symptom of an inherited bleeding disorder. Whereas most bleeding disorders are detected through standard hematologic assessments, diagnosing rare platelet function disorders may be challenging. Here we present two case reports and review diagnostic and management challenges of platelet function disorders with a focus on Glanzmann's thrombasthenia (GT). Patient 1 was a 4-year-old boy with uncontrolled epistaxis. His medical history included frequent and easy bruising. Previous laboratory evaluation revealed only mild microcytic anemia. An otolaryngologist stopped the bleeding, and referral to a pediatric hematologist led to the definitive diagnosis of GT. Patient 2 was a 2.5-year-old girl with severe epistaxis and a history of milder recurrent epistaxis. She had a bruise on her abdomen with a palpable hematoma and many scattered petechiae. Previous assessments revealed no demonstrable hemostatic anomalies. Platelet aggregation studies were performed following referral to a pediatric hematologist, leading to the diagnosis of GT. As evidenced by these cases, the ED physician may often be the first to evaluate severe or recurrent epistaxis and should recognize indications for coagulation testing and hematology consultation/referral for advanced hematologic assessments.

Management of extreme thrombocytosis in myeloproliferative neoplasms: an international physician survey

Extreme thrombocytosis (ExT) has been associated with an increased bleeding risk in myeloproliferative neoplasm (MPN) patients and is included in the high risk category in treatment guidelines. Treatment of patients with ExT has not been studied in prospective trials. To study physicians' approaches to ExT, we distributed a web based questionnaire with clinical case scenarios to 202 members of MPN working groups. Cases included low thrombotic risk essential thrombocythemia (ET) with either JAK2V617F or CALR mutation, polycythemia vera with ExT either with or without leukocytosis, an ET patient needing urgent orthopedic surgery, and a poorly controlled ET patient with acute cerebral venous sinus thrombosis. Responses were received from 90 physicians (45 %) and were variable in most case scenarios. Country of practice had the most significant influence on physician response. The USA and Israel physicians responded similarly in most cases and differently to the Europe physicians. Treatment of asymptomatic JAK2V617F positive ET and target platelet count on cytoreduction were significantly influenced by physician years of experience. Responses were not influenced by the volume of MPN practice or by whether MPN was considered a major interest by the physician. Our results show a lack of consensus on how to manage MPN patients with ExT. Randomized controlled trials properly designed to address these questions are needed.

Platelet function testing: from routine to specialist testing

Platelets have many functions within the haemostatic system, and when these actions are diminished for whatever reason, a bleeding tendency can manifest. Unravelling the reason(s) for this bleeding can be complex due to the multiple roles platelets perform. This review seeks to explain each level of platelet testing moving from those performed at local hospital laboratories to those performed by specialist centres and university research departments. It will examine the testing available and discuss when to move on to additional testing.

Ovine platelet function is unaffected by extracorporeal membrane oxygenation within the first 24 h

This study investigated platelet dysfunction during short-term extracorporeal membrane oxygenation (ECMO) and secondarily to determine if hyperoxaemia contributes to this dysfunction. Healthy sheep were anaesthetized and maintained on ECMO for either 2 or 24 h, with or without induction of smoke inhalation acute lung injury. A specialized animal-operating theatre was used to conduct the experimentation. Forty-three healthy female sheep were randomized into either a test or a control group. Following anaesthesia, test groups received ECMO ± smoke inhalation acute lung injury (SALI), whereas control groups were maintained with ventilation only ± SALI. Physiological, biochemical and coagulation data were obtained throughout via continuous monitoring and blood sampling. Platelet function was quantified through whole blood impedance aggregometry using Multiplate. Ovine platelet activity induced by adenosine diphosphate (ADP) and collagen was unaffected during the first 24 h of ECMO. However, progressive divergence of ADP-induced platelet activity was noted at cessation of the experiment. PaO2 was inversely related to ADP-dependent platelet activity in the ECMO groups--a relationship not identified in the control groups. ADP and collagen-dependent platelet activity are not significantly affected within the first 24 h of ECMO in sheep. However, dysfunction in ADP-dependent platelet activity may have continued to develop if observed beyond 24 h. Hyperoxaemia during ECMO does appear to affect how platelets react to ADP and may contribute to this developing dysfunction. Long-term animal models and investigation in clinical animals are warranted to fully investigate platelet function during ECMO.

Relation Between Platelet Count and Platelet Reactivity to Thrombotic and Bleeding Risk: From the Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents Study

Whether the association between platelet count (PC) and thrombotic and bleeding risk is independent of or varies by residual platelet reactivity to antiplatelet therapies is unclear. We sought to investigate the independent and combined effects of PC and platelet reactivity on thrombotic and bleeding risk after coronary artery implantation of drug-eluting stents (DES). Patients enrolled in the prospective, multicenter Assessment of Dual AntiPlatelet Therapy with Drug-Eluting Stents study were stratified by PC tertiles. The study cohort comprised 8,402 patients. By linear regression analysis, lower PC was strongly and independently associated with higher platelet reactive units (PRUs) on clopidogrel. After multivariable adjustment (including PRU and aspirin reactive units), high, but not low, PC tertile was independently associated with higher risk of thrombotic complications, including spontaneous myocardial infarction and stent thrombosis. Although no independent association was observed between PC tertiles and hemorrhagic risk, both high and low PC tertiles were associated with increased risk for all-cause mortality. After stratification of PC tertiles by tertiles of PRUs, the crude risk of thrombotic complications was highest in patients in the high PC and high PRU tertiles. By multivariable adjustment, PRU increases were uniformly associated with higher risk of thrombotic events across PC tertiles, without evidence of interaction. In conclusion, higher PCs and higher PRUs act independently and synergistically in determining thrombotic risk. Alongside PRU, PCs could be a simple hematological parameter to consider for risk stratification and in tailoring duration and potency of pharmacologic platelet inhibition after DES implantation.

Bleeding risk of dietary supplements: A hidden nightmare for cardiac surgeons

We report a 55-year-old man who underwent off-pump bypass surgery and had diffuse oozing and bruising postoperatively. His hematological profile had been normal preoperatively and he had been off antiplatelets for a week prior to surgery. Postoperatively, a detailed talk revealed that he had been on dietary supplements containing fish oil and garlic - both of which are known to affect platelet function. It behooves the surgeon and anesthetist to screen all patients preoperatively for the possibility of intake of any dietary supplements taken by the patient.

Low dose compared to variable dose Warfarin and to Fondaparinux as prophylaxis for thromboembolism after elective hip or knee replacement surgery; a randomized, prospective study

Background

Deep vein thrombosis (DVT) and pulmonary emboli (PE), known together as venous thromboembolic (VTE) disease remain major complications following elective hip and knee surgery. This study compares three chemoprophylactic regimens for VTE following elective primary unilateral hip or knee replacement, one of which was designed to minimize risk of post-operative bleeding.

Methods

Patients were randomized and stratified for hip vs. knee to receive A: variable dose warfarin (first dose on the night preceding surgery with subsequent target INR 2.0–2.5), B: 2.5 mg fondaparinux daily starting 6–18 h postoperatively, or C: fixed 1.0 mg dose warfarin daily starting 7 days preoperatively. All treatments continued until bilateral leg venous ultrasound day 28 ± 2 or earlier upon a VTE event. The study examined primary endpoints including leg DVT, PE or death due to VTE and secondary endpoints including effects on D-dimer, estimated blood loss (EBL) at surgery and hemorrhagic complications.

Results

Three hundred fifty-five patients were randomized. None was lost to follow-up. Taking 1.0 mg warfarin for seven days preoperatively did not prolong the prothrombin time (PT). Two patients in Arm C had asymptomatic distal DVT. One major bleed occurred in Arm B and one in Arm C (ischemic colitis). Elevated d-dimer did not predict delayed VTE for one year.

Conclusions

Fixed low dose warfarin started preoperatively is equivalent to two other standards of care under study (95 % CI: -0.0428, 0.0067 for both) as VTE prophylaxis for the patients having elective major joint replacement surgery.

Trial registration

ClinicalTrials.gov identifier # NCT00767559

FDA IND: 103,716

Neonatal Platelet Function

Similarly to the development of the plasma coagulation system, which matures during the early weeks and months of life, age-dependent mechanisms and developmental changes influence platelet production and function in neonates. Platelet function testing on cord blood and peripheral blood demonstrates a generalized platelet hyporeactivity, during the first days of life. This reactivity reaches normal adult levels between the fifth and ninth day of life. The persistence of hyporeactivity after the tenth day of life might indeed suggest a platelet disorder.

Platelet transfusion for patients with cancer

BACKGROUND

Platelet transfusion is a critical and often necessary aspect of managing cancer. Low platelet counts frequently lead to bleeding complications; however, the drugs used to combat malignancy commonly lead to decreased production and destruction of the very cell whose function is essential to stop bleeding. The transfusion of allogeneic platelet products helps to promote hemostasis, but alloimmunization may make it difficult to manage other complications associated with cancer.

METHODS

The literature relating to platelet transfusion in patients with cancer was reviewed.

RESULTS

Platelet storage, dosing, transfusion indications, and transfusion response are essential topics for health care professionals to understand because many patients with cancer will require platelet transfusions during the course of treatment. The workup and differentiation of non-immune-mediated compared with immune-mediated platelet refractoriness are vital because platelet management is different between types of refractoriness.

CONCLUSIONS

A combination of appropriate utilization of platelet inventory and laboratory testing coupled with communication between those caring for patients with cancer and those providing blood products is essential for effective patient care.

Prophylactic plasma and platelet transfusion in the critically Ill patient: just useless and expensive or even harmful?

It is still common practice to correct abnormal standard laboratory test results, such as increased INR or low platelet count, prior to invasive interventions, such as tracheostomy, central venous catheter insertion or liver biopsy, in critically ill patients. Data suggest that 30-90 % of plasma transfused for these indications is unnecessary and puts the patient at risk. Plasma transfusion is associated with a high risk of transfusion-associated adverse events such as transfusion-associated circulatory overload (TACO), transfusion-related lung injury (TRALI), transfusion-related immunomodulation (TRIM), and anaphylaxis/allergic reactions. Therefore, the avoidance of inappropriate plasma transfusion bears a high potential of improving patient outcomes. The prospective study by Durila et al., published recently in BMC Anesthesiology, provides evidence that tracheostomies can be performed without prophylactic plasma transfusion and bleeding complications in critically ill patients despite increased INR in case of normal thromboelastometry (ROTEM) results. Thromboelastometry-based restrictive transfusion management helped avoid unnecessary plasma and platelet transfusion, and should reduce the incidence of transfusion-related adverse events and transfusion-associated hospital costs. Therefore, the authors believe that thromboelastometry-based strategies should be implemented to optimize patient blood management in perioperative medicine.

Identification of acquired coagulation disorders and effects of target-controlled coagulation factor substitution on the incidence and severity of spontaneous intracranial bleeding during veno-venous ECMO therapy

Introduction:

Intracranial haemorrhage is a redoubtable complication during extracorporeal membrane oxygenation (ECMO) therapy. The underlying mechanisms of haemorrhagic diathesis are still not completely understood. This study was performed to evaluate a coagulation protocol for the regular analysis of acquired coagulation disorders and the systematic substitution of coagulation factors to reach predefined target values. We hypothesised that using this strategy would lead to the identification of acquired bleeding disorders which cannot be monitored with standard coagulation tests and that substitution of the respective factors in a target-controlled approach could have an impact on the incidence and severity of intracranial haemorrhage.

Methods:

A protocol for the analysis of acquired coagulation disorders and the subsequent administration of associated factor concentrates was introduced. Previously, coagulation management was mainly based on clinical bleeding signs as the trigger for the administration of blood products. In this investigation, nineteen consecutive patients before (control group) and twenty consecutive patients after the implementation of the protocol (intervention group) have been included in the study.

Results:

Eighty-eight percent of the patients developed factor XIII deficiency, 79% acquired von Willebrand syndrome, 40% fibrinogen deficiency and 54% of the patients showed a decline in platelet count >20% within the first 24 hours of ECMO therapy. In 6 out of 19 (31%) patients in the control group and in 2 patients out of 20 (10%) in the intervention group, intracranial haemorrhage was detected. Whilst 5 of 6 patients in the control group died because of fatal bleeding, both of the patients in the intervention group recovered with a favourable neurologic outcome.

Conclusions:

Veno-venous ECMO therapy leads to thrombocytopenia, factor XIII and fibrinogen deficiency as well as acquired von Willebrand syndrome. The implementation of a coagulation protocol including a standardized determination and target-controlled substitution of coagulation factors may have a beneficial impact on the incidence and severity of intracranial haemorrhage.

Platelet dysfunction and acquired von Willebrand syndrome in patients with left ventricular assist devices

OBJECTIVES

Unexplained bleeding events are a severe complication in patients with left ventricular assist devices (LVADs). Platelet dysfunction and acquired von Willebrand syndrome (AVWS) may contribute to bleeding tendencies. Yet, comprehensive data with respect to platelet function and AVWS in LVAD patients in terms of bleeding events are scarce.

METHODS

Thirty-nine HeartMate II patients were included in this study. Data of at least two time points were available for each patient. Platelet function was analysed via light transmission aggregometry in 19 patients without LVAD, 28 in early (≤14 days) and 30 in late postimplantation states (≥30 days). Von Willebrand factor (VWF) antigen, VWF collagen binding capacity and VWF multimeric analyses were performed in 26 patients without LVAD, 39 in early and 33 in late postimplantation states to diagnose AVWS. Bleeding complications were recorded for 39 patients in the early and 33 in the late postoperative period.

RESULTS

Platelet dysfunction was detectable in 18 of 19 without LVAD and in all patients following LVAD implantation. Platelet aggregation values did not change over time (without-early, P = 0.27, n = 14; early-late, P = 0.17, n = 21). AVWS was not diagnosed in patients without LVAD, except for one. On LVAD, 33 of 39 patients had AVWS in the early and all in the late period (n = 33). Bleeding events occurred in 44% of patients in the early and in 64% of patients in the late period.

CONCLUSIONS

According to our data, platelet aggregation is often impaired in LVAD patients even without an implanted LVAD. Additionally, appearance of AVWS seems to be closely linked to LVAD implantation.

Management of thrombocytopenia

Thrombocytopenia is one of the most common hematologic disorders, characterized by an abnormally low number of platelets from multiple causes. The normal count of thrombocytes (platelets) is between 150,000 and 450,000 per microliter. The clinical expression of thrombocytopenia has broad variation from asymptomatic to life-threatening bleeding. Various syndromes and diseases are associated with thrombocytopenia. Thrombocytopenia is sometimes a first sign of hematologic malignancies, infectious diseases, thrombotic microangiopathies, and autoimmune disorders, and is also a common side effect of many medications. There are more than 200 diseases that include low number of platelets among their symptoms. A brief discussion of the most common etiologies and management of them is provided in this review.

Prognostic significance of post percutaneous coronary intervention thrombocytopenia

Several definitions of post percutaneous coronary intervention (PCI) thrombocytopenia (TC) were formulated. Recent studies demonstrated that a relative drop in platelet count ≥ 25% is the most appropriate criterion. By this definition a population is detected that is exposed not only to increased risk of hemorrhagic complications but also to increased risk of ischemic events, which may appear a paradox. In patients with acute coronary syndromes undergoing PCI, several conditions might be associated with TC: cardiopulmonary by-pass and the presence of extra corporeal membrane oxygenators, intra aortic balloon pump (IABP), cardiogenic shock, thrombolytic drugs and anticoagulant or antiplatelet drugs. Several studies demonstrated that TC and ischemic outcomes are related although it is unclear whether this is a direct relationship or TC is just a secondary effect of another cryptic protagonist. It is suggested that further investigations determine whether there is a real link between TC, a probably well defined covariate, and ischemic outcomes or whether IABP is the joining link between these two variables and whose presence needs in any case be considered in multivariable statistics. Post-PCI TC could be only a secondary effect of IABP use. On turn, the prolonged use of heparin necessarily accompanying the use of IABP, and producing a paradoxical pro-thrombotic TC, might also be implicated.

Reprint of "Decline in platelet count and long-term post-PCI ischemic events: implication of the intra-aortic balloon pump"

AIMS

Thrombocytopenia (TC) following a percutaneous coronary intervention (PCI) has been associated not only with hemorrhagic, but also with ischemic outcomes. The purpose of this study was to re-examine the relationship of TC with ischemic events at a 1-year follow-up, and investigate the possible associations.

METHODS AND RESULTS

We studied a real-world, unselected population of ischemic patients undergoing PCI, totaling 861 patients-year, and divided into two groups: with TC (delta platelet count ≥25% from baseline to post-PCI during the hospital admission) and without TC. Compared with patients without TC, patients with TC had a higher and earlier incidence of both hemorrhagic and ischemic events. In them, the use of intra-aortic balloon pump (IABP) was ten-fold higher. In Kaplan-Meier curves assessing the contribution of both TC and IABP to outcome, IABP was a univariate detrimental factor additive to the role of TC. In a forced Cox model, the relative decline (delta) in platelet count (p=0.05) and the use of IABP (p=0.0001) were both associated with ischemic outcomes. After excluding all patients with IABP, the delta platelet count was no longer significantly associated with ischemic outcomes (p=0.66). After excluding all patients with shock and all those who undergone thrombolysis, there was still a relationship (p=0.0042) between the delta platelet count and ischemic events.

CONCLUSIONS

In this patient population the use of IABP, but not thrombocytopenia per se, is a possible primary cause of worse ischemic outcomes.

Decline in platelet count and long-term post-PCI ischemic events: implication of the intra-aortic balloon pump

AIMS

Thrombocytopenia (TC) following a percutaneous coronary intervention (PCI) has been associated not only with hemorrhagic, but also with ischemic outcomes. The purpose of this study was to re-examine the relationship of TC with ischemic events at a 1-year follow-up, and investigate the possible associations.

METHODS AND RESULTS

We studied a real-world, unselected population of ischemic patients undergoing PCI, totaling 861 patients-year, and divided into two groups: with TC (delta platelet count ≥25% from baseline to post-PCI during the hospital admission) and without TC. Compared with patients without TC, patients with TC had a higher and earlier incidence of both hemorrhagic and ischemic events. In them, the use of intra-aortic balloon pump (IABP) was ten-fold higher. In Kaplan-Meier curves assessing the contribution of both TC and IABP to outcome, IABP was a univariate detrimental factor additive to the role of TC. In a forced Cox model, the relative decline (delta) in platelet count (p=0.05) and the use of IABP (p=0.0001) were both associated with ischemic outcomes. After excluding all patients with IABP, the delta platelet count was no longer significantly associated with ischemic outcomes (p=0.66). After excluding all patients with shock and all those who undergone thrombolysis, there was still a relationship (p=0.0042) between the delta platelet count and ischemic events.

CONCLUSIONS

In this patient population the use of IABP, but not thrombocytopenia per se, is a possible primary cause of worse ischemic outcomes.

CD34 affinity pheresis attenuates a surge among circulating progenitor cells following vascular injury

BACKGROUND

Intimal hyperplasia (restenosis) is an exaggerated healing response leading to failure of half of vascular interventions. Increasing evidence suggests that circulating progenitor cells contribute to intimal pathology, and clinical studies have demonstrated a correlation between progenitor cells and the incidence of restenosis after cardiovascular interventions. The aims of this study were to characterize the temporal response of CD34+ progenitors following vascular injury in an ovine model and to evaluate an affinity pheresis approach to attenuate this response.

METHODS

An ovine model underwent either operative vascular injury or a nonvascular surgery (n = 3 per group). Blood was examined perioperatively over 2 weeks by flow cytometry. Next, an affinity pheresis approach to mediate systemic depletion of CD34 progenitors was designed. Custom agarose pheresis matrix with antibody affinity toward CD34 or an isotype control was evaluated in vitro. Next, following vascular injury, sheep underwent perioperative whole blood volume pheresis toward either the progenitor cell marker CD34 (n = 3) or an isotype control (n = 4) for 14 days. Animals were monitored by physical exam as well as complete blood counts. Cells recovered by pheresis were eluted and examined by flow cytometry.

RESULTS

Flow cytometry revealed a focal surge of circulating CD34 cells after vascular injury but not among surgical controls (P = .05). Toward the goal of an approach to attenuate the surge of CD34 progenitors, an evaluation of high-flow affinity matrix revealed efficacy in removal of progenitors from ovine blood in vitro. Next, a separate group of animals undergoing affinity pheresis after vascular injury was evaluated to mediate systemic depletion of CD34+ cells. Again, a surge of CD34+ cells was observed among isotype pheresis animals following vascular intervention but was attenuated over 20-fold by a CD34 pheresis approach (P = .029). Furthermore, an average of 77 million CD34-positive cells were eluted from the CD34 pheresis matrix. Despite multiple sessions of pheresis, complete blood counts remained essentially unchanged over 2 weeks.

CONCLUSIONS

Despite evidence suggesting a role for CD34+ circulating progenitor cells in restenotic pathology, the temporal pattern of CD34 progenitors after vascular injury has not been previously defined. We have demonstrated a surge among circulating CD34+ cells that appears confined to procedures involving vascular injury and that this event seems to occur early after vascular injury. We further conclude that CD34 affinity pheresis attenuates the surge. This approach for direct depletion of progenitors may have important implications for the study of progenitors in vascular restenosis.

Whole blood platelet aggregation and release reaction testing in uremic patients

Background. Platelet function analysis utilizing platelet-rich plasma and optical density based aggregometry fails to identify patients at risk for uremia associated complications. Methods. We employed whole blood platelet aggregation analysis based on impedance as well as determination of ATP release from platelet granules detected by a chemiluminescence method. Ten chronic kidney disease (CKD) stage 4 or 5 predialysis patients underwent platelet evaluation. Our study aims to evaluate this platform in this patient population to determine if abnormalities could be detected. Results. Analysis revealed normal aggregation and ATP release to collagen, ADP, and high-dose ristocetin. ATP release had a low response to arachidonic acid (0.37 ± 0.26 nmoles, reference range: 0.6–1.4 nmoles). Platelet aggregation to low-dose ristocetin revealed an exaggerated response (20.9 ± 18.7 ohms, reference range: 0–5 ohms). Conclusions. Whole blood platelet analysis detected platelet dysfunction which may be associated with bleeding and thrombotic risks in uremia. Diminished ATP release to arachidonic acid (an aspirin-like defect) in uremic patients may result in platelet associated bleeding. An increased aggregation response to low-dose ristocetin (a type IIb von Willebrand disease-like defect) is associated with thrombus formation. This platelet hyperreactivity may be associated with a thrombotic diathesis as seen in some uremic patients.

Is hyperoxaemia helping or hurting patients during extracorporeal membrane oxygenation? Review of a complex problem

Extracorporeal membrane oxygenation (ECMO) facilitates organ support in patients with refractory cardiorespiratory failure whilst disease-modifying treatments can be administered. Improvements to the ECMO process have resulted in its increased utilisation. However, iatrogenic injuries remain, with bleeding and thrombosis the most significant concerns. Many factors contribute to the formation of thrombi, with the hyperoxaemia experienced during ECMO a potential contributor. Outside of ECMO, emerging evidence associates hyperoxaemia with increased mortality. Currently, no universal definition of hyperoxaemia exists, a gap in clinical standards that may impact patient outcomes. Hyperoxaemia has the potential to induce platelet activation, aggregation and, subsequently, thrombosis through markedly increasing the production of reactive oxygen species. There are minimal data in the current literature that explore the relationship between ECMO-induced hyperoxaemia and the production of reactive oxygen species – a putative link towards pathology. Furthermore, there is limited research directly linking hyperoxaemia and platelet activation. These are areas that warrant investigation as definitive data regarding the nascence of these pathological processes may delineate and define the relative risk of supranormal oxygen tension. These data could then assist in defining optimal oxygenation practice, reducing the risks associated with extracorporeal support.