Coagulopathy in critically ill patients: part 1: platelet disorders

A Contemporary Review of Blood Transfusion in Critically Ill Patients

Blood transfusion is a common therapeutic intervention in hospitalized patients. There are numerous indications for transfusion, including anemia and coagulopathy with deficiency of single or multiple coagulation components such as platelets or coagulation factors. Nevertheless, the practice of transfusion in critically ill patients has been controversial mainly due to a lack of evidence and the need to consider the appropriate clinical context for transfusion. Further, transfusion carries many risk factors that must be balanced with benefits. Therefore, transfusion practice in ICU patients has constantly evolved, and we endeavor to present a contemporary review of transfusion practices in this population guided by clinical trials and expert guidelines.

Viruses and thrombocytopenia

Thrombocytopenia, characterized by a decrease in platelet count, is a multifaceted clinical manifestation that can arise from various underlying causes. This review delves into the intriguing nexus between viruses and thrombocytopenia, shedding light on intricate pathophysiological mechanisms and highlighting the pivotal role of platelets in viral infections. The review further navigates the landscape of thrombocytopenia in relation to specific viruses, and sheds light on the diverse mechanisms through which hepatitis C virus (HCV), measles virus, parvovirus B19, and other viral agents contribute to platelet depletion. As we gain deeper insights into these interactions, we move closer to elucidating potential therapeutic avenues and preventive strategies for managing thrombocytopenia in the context of viral infections.

In-hospital outcomes after acute myocardial infarction with obstructive coronary artery disease in critically ill patients hospitalized for non-cardiac disease

BACKGROUND

Acute myocardial infarction (AMI) is one of the major cardiac complications in patients hospitalized in the intensive care unit (ICU) for non-cardiac disease. A better knowledge of ischemic and bleeding risks in these patients is needed to identify those most likely to benefit from specific cardiac management. We therefore assessed the incidence and predictors of a composite outcome of severe ischemic event (AMI recurrence, ischemic stroke), major bleeding, or all-cause death in this setting.

METHODS

In this multicenter retrospective study, all consecutive adult patients admitted for non-cardiac disease to four French university hospital ICUs between January 2012 and December 2018 who had an AMI with obstructive coronary artery disease (OCAD) during the ICU stay were considered for inclusion. AMI with OCAD was defined as an elevated cardiac troponin value associated with at least one sign (clinical, electrocardiographic, or echocardiographic) suggestive of myocardial ischemia and presence of OCAD on coronary angiography. The primary endpoint was in-hospital occurrence of the composite outcome.

RESULTS

Ninety-six patients [median age 69 years, 22 women (23%), 59 with sepsis (61%), 35 with ST elevation (37%), median sequential organ failure assessment (SOFA) of 8 on the day of AMI] were included. The median peak cardiac troponin value was 131 (IQR 44-303) times the upper reference limit. Dual antiplatelet, therapeutic anticoagulation, and early mechanical reperfusion therapies were administered in 61 (64%), 68 (71%), and 47 (49%) patients, respectively. The composite outcome occurred in 48 (50%) patients. Severe ischemic events occurred in 17 (18%) patients and major bleeding in 26 (27%) patients; 26 patients (27%) died in the hospital. AMI management was not significantly different in patients with and without the composite outcome. A history of arterial hypertension (HR 2.05, 95% CI 1.01-4.16) and high SOFA score at the time of AMI (HR 1.07, 95% CI 1.00-1.15) were independent risk factors for the composite outcome.

CONCLUSIONS

Patients who have an AMI with OCAD during an ICU stay for non-cardiac disease are at risk of a composite outcome of severe ischemia, major bleeding, and death. A history of arterial hypertension and high SOFA scores were independent hazards for poor prognosis.

Circulating Extracellular Vesicles: Their Role in Patients with Abdominal Aortic Aneurysm (AAA) Undergoing EndoVascular Aortic Repair (EVAR)

Abdominal aortic aneurysm (AAA) is a frequent aortic disease. If the diameter of the aorta is larger than 5 cm, an open surgical repair (OSR) or an endovascular aortic repair (EVAR) are recommended. To prevent possible complications (i.e., endoleaks), EVAR-treated patients need to be monitored for 5 years following the intervention, using computed tomography angiography (CTA). However, this radiological method involves high radiation exposure in terms of CTA/year. In such a context, the study of peripheral-blood-circulating extracellular vesicles (pbcEVs) has great potential to identify biomarkers for EVAR complications. We analyzed several phenotypes of pbcEVs using polychromatic flow cytometry in 22 patients with AAA eligible for EVAR. From each enrolled patient, peripheral blood samples were collected at AAA diagnosis, and after 1, 6, and 12 months following EVAR implantation, i.e. during the diagnostic follow-up protocol. Patients developing an endoleak displayed a significant decrease in activated-platelet-derived EVs between the baseline condition and 6 months after EVAR intervention. Furthermore, we also observed, that 1 month after EVAR implantation, patients developing an endoleak showed higher concentrations of activated-endothelial-derived EVs than patients who did not develop one, suggesting their great potential as a noninvasive and specific biomarker for early identification of EVAR complications.

Disseminated Intravascular Coagulation (DIC): Old player creates new perspectives on the polymicrobial sepsis model of CASP

BACKGROUND

Disseminated Intravascular Coagulation (DIC) is a life-threatening complication of sepsis. In surgical ICUs, DIC is frequently caused by abdominal sepsis, and the disarranged coagulation and complications often lead to death. The severity of sepsis is associated with a higher DIC score according to the parameters proposed by the International Society of Hemostasis and Thrombosis (ISTH) in 2001: platelet count, bleeding time (Quick), D-dimer, and fibrinogen. One problem in studying DIC is finding an adequate animal model that reflects the clinical situation of polymicrobial overwhelming infection.

AIMS AND METHODS

We investigated whether a well-established polymicrobial sepsis model of colon ascendens stent peritonitis (CASP) is suited to investigate the complexity of DIC. For this purpose, CASP-operated mice were examined 20 h after the operation with regard to coagulation parameters using cell counts, bleeding times, rotational thromboelastometry (ROTEM), ELISAs for D-dimer and fibrinogen, and platelet accumulation in affected organs via immunohistochemistry to see if the mice develop a coagulation disorder that meets the definition of DIC proposed by the ISTH 2001 consensus conference.

RESULTS

Herein, we showed that the CASP model is an all-encompassing animal model to analyze the complexity of systemic DIC in murine abdominal sepsis. There is highly reproducible thrombocytopenia, a significant prolongation of the bleeding time, and a loss of fibrinogen in plasma. We also observed microvascular thrombosis due to platelet accumulation in the microcirculation of the liver.

CONCLUSION

The CASP model seems superior to other artificial models, e.g., injecting substances, for inducing DIC. CASP is one of the best true-to-life models for analyzing the complexity of disseminated intravascular coagulation in polymicrobial sepsis.

Development and validation of a prediction model for in-hospital mortality of patients with severe thrombocytopenia

Risk stratification and prognosis evaluation of severe thrombocytopenia are essential for clinical treatment and management. Currently, there is currently no reliable predictive model to identify patients at high risk of severe thrombocytopenia. This study aimed to develop and validate a prognostic nomogram model to predict in-hospital mortality in patients with severe thrombocytopenia in the intensive care unit. Patients diagnosed with severe thrombocytopenia (N = 1561) in the Medical Information Mart for Intensive Care IV database were randomly divided into training (70%) and validation (30%) cohorts. In the training cohort, univariate and multivariate logistic regression analyses with positive stepwise selection were performed to screen the candidate variables, and variables with p < 0.05 were included in the nomogram model. The nomogram model was compared with traditional severity assessment tools and included the following 13 variables: age, cerebrovascular disease, malignant cancer, oxygen saturation, heart rate, mean arterial pressure, respiration rate, mechanical ventilation, vasopressor, continuous renal replacement therapy, prothrombin time, partial thromboplastin time, and blood urea nitrogen. The nomogram was well-calibrated. According to the area under the receiver operating characteristics, reclassification improvement, and integrated discrimination improvement, the nomogram model performed better than the traditional sequential organ failure assessment (SOFA) score and simplified acute physiology score II (SAPS II). Additionally, according to decision curve analysis, a threshold probability between 0.1 and 0.75 indicated that our constructed nomogram model showed more net benefits than the SOFA score and SAPS II. The nomogram model we established showed superior predictive performance and can assist in the quantitative assessment of the prognostic risk in patients with severe thrombocytopenia.

Anticoagulation in Patients with Platelet Disorders

Platelet disorders comprise heterogeneous diseases featured by reduced platelet counts and/or impaired platelet function causing variable bleeding symptoms. Despite their bleeding diathesis, patients with platelet disorders can develop transient or permanent prothrombotic conditions that necessitate prophylactic or therapeutic anticoagulation. Anticoagulation in patients with platelet disorders is a matter of concern because the bleeding risk could add to the hemorrhagic risk related to the platelet defect. This review provides an overview on the evidence on anticoagulation in patients with acquired and inherited thrombocytopenia and/or platelet dysfunction. We summarize tools to evaluate and balance bleeding- and thrombotic risks and describe a practical approach on how to manage these patients if they have an indication for prophylactic or therapeutic anticoagulation.

Continuous renal replacement therapy without anticoagulation in critically ill patients at high risk of bleeding: A systematic review and meta-analysis

The current clinical guideline recommends continuous renal replacement therapy (CRRT) proceed without anticoagulation in patients with contraindication to citrate and increased bleeding risk. Nevertheless, the efficacy of anticoagulation-free CRRT remains inconsistent. The purpose of our present systematic review is to evaluate the efficacy and safety of anticoagulant-free CRRT based on the current literatures. The primary outcomes were filter lifespan and risk factors for filter failure. Seventeen observational studies and three randomized controlled trials were included in our present meta-analysis. There was no significant difference in filter lifespan and azotemic control between the anticoagulation-free and systemic heparin group. The regional citrate anticoagulation (RCA) protocol seems to be superior to the anticoagulation-free protocol in terms of filter lifespan (WMD -23.01, 95% CI [-28.62, -17.39], p < 0.001; I²  = 0%, p = 0.53) and azotemic control. Nafamostat protocol could significantly prolong filter lifespan (WMD -8.4, 95% CI [-9.9, -6.9], p < 0.001; I²  = 33.7%, p = 0.21) as compared with anticoagulation-free protocol without better azotemic control. The conventional coagulation parameters showed poor predictive performence for filter failure and the necessity of anticoagulants use before CRRT. Currently, the optimal choice of anticoagulation strategy for critically ill patients with increased bleeding risk could be RCA under close monitoring.

Current understanding and future implications of sepsis-induced thrombocytopenia

Sepsis is a global health burden that needs intensive medical care. Thrombocytopenia in sepsis is well known to increase morbidity as well as mortality. Several studies have been performed both in animal models and in humans to understand the mechanism by which sepsis causes thrombocytopenia. Recent studies have shown that inhibiting thrombocytopenia improves outcomes in sepsis patients. Understanding these mechanisms to identify targets in use of newer treatment modalities besides using resuscitation measures, antibiotics and removal of thrombocytopenia inducing agent could potentially help us improve outcomes in sepsis.

Critical Care Society of Southern Africa adult patient blood management guidelines: 2019 Round-table meeting, CCSSA Congress, Durban, 2018

The CCSSA PBM Guidelines have been developed to improve patient blood management in critically ill patients in southern Africa. These consensus recommendations are based on a rigorous process by experts in the field of critical care who are also practicing in South Africa (SA). The process comprised a Delphi process, a round-table meeting (at the CCSSA National Congress, Durban, 2018), and a review of the best available evidence and international guidelines. The guidelines focus on the broader principles of patient blood management and incorporate transfusion medicine (transfusion guidelines), management of anaemia, optimisation of coagulopathy, and administrative and ethical considerations. There are a mix of low-middle and high-income healthcare structures within southern Africa. Blood products are, however, provided by the same not-for-profit non-governmental organisations to both private and public sectors. There are several challenges related to patient blood management in SA due most notably to a high incidence of anaemia, a frequent shortage of blood products, a small donor population, and a healthcare system under financial strain. The rational and equitable use of blood products is important to ensure best care for as many critically ill patients as possible. The summary of the recommendations provides key practice points for the day-to-day management of critically ill patients. A more detailed description of the evidence used to make these recommendations follows in the full clinical guidelines section.

Thrombocytopenia in the Intensive Care Unit

The evaluation and management of thrombocytopenia is a daily challenge for clinicians in the intensive care unit (ICU). Thrombocytopenia is incredibly common, present in upwards of 60% of ICU patients. Additionally, thrombocytopenia in the critically ill is rarely caused by a single etiology. Several causes of thrombocytopenia in the ICU including heparin-induced thrombocytopenia (HIT) and thrombotic thrombocytopenic purpura demand urgent recognition and intervention. This chapter provides a general overview of thrombocytopenia in the ICU and highlights important diagnostic and management considerations for some of the most common etiologies.

Thrombocytopenia in the intensive care unit

Thrombocytopenia is a frequent finding in intensive care unit especially among adults and medical ICU patients. Thrombocytopenia is defined as a platelet count less than 100×10⁹/l in ICU setting. Platelets are made in the bone marrow from megakaryocytes. Although not fully understood, proplatelets transform into platelets in the lung. The body tries to maintain platelet count relatively constant throughout life. Pathophysiology of thrombocytopenia can be defined by hemodilution, elevated levels of platelet consumption, compromise of platelet production, increased platelet sequestration and increased platelet destruction. Unlike in other situations, absolute platelet count alone does not provide sufficient data in characterizing thrombocytopenia in ICU patients. In such cases, the time course of changes in platelet count is also pivotal. The dynamics of platelet count decrease vary considerably between different ICU patient populations including trauma, major surgery and minor surgery/medical conditions. There are strong evidences available that delay in platelet count restoration in ICU patients is an indicator of a bad outcome.

Spectrum of Diseases/conditions Exhibiting Hemostatic Abnormalities in Patients Admitted to a Medical Intensive Care Unit of a Tertiary Care Hospital

Background and Aims:

In a medical intensive care unit (MICU), many patients develop hemostatic abnormalities, ranging from abnormal clotting tests to frank bleeding. The aim of this study was to assess the etiology of diseases that present with bleeding, its common bleeding manifestations, incidence, MICU stay, mortality, and transfusion requirements in an Indian setup and also to assess if the Acute Physiology and Chronic Health Evaluation II (APACHE II) score can be used as a predictor for blood transfusion requirements.

Materials and Methods:

Between July 2013 and August 2014, 200 patients with clinically significant bleeding admitted in the MICU were prospectively evaluated. Detailed history, examination, laboratory investigations, APACHE II score, and requirement of blood products were also noted. The endpoints were discharge or death.

Results:

The spectrum of diseases that presented with bleeding was 47 patients with malaria (23.5%) followed by 36 acute undifferentiated febrile illness (18.0%), 33 dengue (16.5%), 30 leptospirosis (15.0%), 31 acute fulminant hepatitis (15.5%), 14 sepsis (7.0%), and the rest nine miscellaneous causes. The most common bleeding manifestation observed was hematuria in 62/200 (31%). Among the patients studied, 126 expired (63%) and 74 survived (37%). Of the 200 patients, 48/200 (24%) received packed cells, 78/200 (39%) fresh frozen plasma, and 82/200 (41%) platelets.

Conclusions:

Tropical diseases formed the majority of admissions with bleeding manifestations. Thrombocytopenia is an important marker to predict mortality and also has a significant association with MICU stay. APACHE II score was found to be a good predictor of blood transfusion requirements.

Amicus or Adversary Revisited: Platelets in Acute Lung Injury and Acute Respiratory Distress Syndrome

Platelets are essential cellular effectors of hemostasis and contribute to disease as circulating effectors of pathologic thrombosis. These are their most widely known biologic activities. Nevertheless, recent observations demonstrate that platelets have a much more intricate repertoire beyond these traditional functions and that they are specialized for contributions to vascular barrier integrity, organ repair, antimicrobial host defense, inflammation, and activities across the immune continuum. Paradoxically, on the basis of clinical investigations and animal models of disease, some of these newly discovered activities of platelets appear to contribute to tissue injury. Studies in the last decade indicate unique interactions of platelets and their precursor, the megakaryocyte, in the lung and implicate platelets as essential effectors in experimental acute lung injury and clinical acute respiratory distress syndrome. Additional discoveries derived from evolving work will be required to precisely define the contributions of platelets to complex subphenotypes of acute lung injury and to determine if these remarkable and versatile blood cells are therapeutic targets in acute respiratory distress syndrome.

Endogenous thrombin potential as marker of procoagulant response that can be useful in early stage of sepsis

: Sepsis is associated with complex procoagulant and anticoagulant changes that modify inflammatory response. Identification of coagulation markers that can differentiate useful procoagulant response from adverse alteration of clotting mechanism in patient with sepsis. In total, 150 patients who fulfilled criteria for diagnosis of sepsis were included in this study. Patients were categorized in two groups according to sepsis severity in the first 24 h from intensive care unit admission: sepsis and septic shock. In total, 28-day mortality was assessed. Platelet count, activated partial thromboplastin time, prothrombin time, D-dimer, fibrinogen, protein C, protein S, antithrombin levels, and endogenous thrombin potential were determined within first 24 h from ICU admission. Differences between groups of septic patients were assessed by Mann-Whitney U test. Categorical variables were compared using χ test. Receiver operating characteristic curves were plotted to determine predictive values of variables for sepsis severity prediction. Activated partial thromboplastin time and prothrombin time were significantly prolonged with higher D-dimer, lower fibrinogen, and natural anticoagulant levels (protein C, protein S, and antithrombin) in patients with more severe form of the disease and worse outcome (P < 0.05). Endogenous thrombin potential [area under the curve (AUC) %] was significantly decreased in patients with more severe form of sepsis (66.01 ± 41.51 vs. 83.21 ± 28.83; AUC 0.76) and in patients with worse outcome (67.66 ± 37.79 vs. 81.79 ± 32.15; AUC 0.68; P < 0.05). Evaluation of initial thrombin generation is useful to distinguish between beneficial coagulation activation and hazardous haemostatic alteration, and to predict multiorgan dysfunction development and poor outcome in septic patients.

Implementation of a rapid HIT immunoassay at a university hospital - Retrospective analysis of HIT laboratory orders in patients with thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a rare cause of thrombocytopenia and a potentially life-threatening adverse drug reaction. Clinical overdiagnosis of HIT results in costly laboratory tests and anticoagulation. Criteria and algorithms for diagnosis are established, but their translation into clinical practice is still challenging.

STUDY DESIGN AND METHODS

In a retrospective approach we studied all HIT related laboratory test requests within four years and evaluated data before (1st period, 24month) and after (2nd period, 24month) replacing particle gel immunoassay (PaGIA) and enzyme-linked immunosorbent assay (ELISA) by a chemiluminescent immunoassay (CLIA). HIT was confirmed by heparin-induced platelet activation (HIPA) test. Clinical pretest probability for HIT using an implemented simplified 4Ts score and platelet count were evaluated. Costs for laboratory tests and alternative anticoagulation were calculated.

RESULTS

In 1850 patients with suspected HIT, 2327 laboratory orders were performed. In 87.2% of these orders an intermediate/high simplified 4Ts score was found. Thrombocytopenia was present in 87.1%. After replacing PaGIA and ELISA by CLIA the number of immunological and functional laboratory tests was reduced by 38.2%. The number of positive HIT immunoassays declined from 22.6% to 6.0%, while the number of positive HIPA tests among positive immunological tests increased by 19%. Altogether, acute HIT was confirmed in 59 patients. A decline in the use of alternative anticoagulants was observed in the 2nd period.

CONCLUSION

Our study shows that in a university hospital setting HIT is well-known, but diagnosis requires a precise laboratory confirmation. Replacing PaGIA and ELISA by CLIA did not influence laboratory order behavior but results in reduced overall costs for laboratory diagnostics and alternative anticoagulation.

A Missense Genetic Variant in LRRC16A/CARMIL1 Improves Acute Respiratory Distress Syndrome Survival by Attenuating Platelet Count Decline

RATIONALE

Platelets are believed to contribute to acute respiratory distress syndrome (ARDS) pathogenesis through inflammatory coagulation pathways. We recently reported that leucine-rich repeat-containing 16A (LRRC16A) modulates baseline platelet counts to mediate ARDS risk.

OBJECTIVES

To examine the role of LRRC16A in ARDS survival and its mediating effect through platelets.

METHODS

A total of 414 cases with ARDS from intensive care units (ICUs) were recruited who had exome-wide genotyping data, detailed platelet counts, and follow-up data during ICU hospitalization. Association of LRRC16A single-nucleotide polymorphisms (SNPs) and ARDS prognosis, and the mediating effect of SNPs through platelet counts were analyzed. LRRC16A mRNA expression levels for 39 cases with ARDS were also evaluated.

MEASUREMENTS AND MAIN RESULTS

Missense SNP rs9358856G>A within LRRC16A was associated with favorable survival within 28 days (hazard ratio [HR], 0.57; 95% confidence interval [CI], 0.38-0.87; P = 0.0084) and 60 days (P = 0.0021) after ICU admission. Patients with ARDS who carried the variant genotype versus the wild-type genotype showed an attenuated platelet count decline (∆PLT) within 28 days (difference of ∆PLT, -27.8; P = 0.025) after ICU admission. Patients with ∆PLT were associated with favorable ARDS outcomes. Mediation analysis indicated that the SNP prognostic effect was mediated through ∆PLT within 28 days (28-day survival: HR_Indirect, 0.937; 95% CI, 0.918-0.957; P = 0.0009, 11.53% effects mediated; 60-day survival: HR_Indirect, 0.919; 95% CI, 0.901-0.936; P = 0.0001, 14.35% effects mediated). Functional exploration suggested that this SNP reduced LRRC16A expression at ICU admission, which was associated with a lesser ∆PLT during ICU hospitalization.

CONCLUSIONS

LRRC16A appears to mediate ∆PLT after ICU admission to affect the prognosis in patients with ARDS.

[Thrombocytopenia in the intensive care unit]

Thrombozytopenie ist ein häufiges Phänomen in der Intensivmedizin. Eine Vielzahl von Ursachen kann für erniedrigte Plättchenzahlen verantwortlich sein. Da Plättchen Teil der primären Hämostase sind, ist Blutungsneigung die wichtigste Komplikation einer Thrombopenie. Strukturiertes Aufarbeiten der Differenzialdiagnose und Identifikation der Ursache ist essenziell, da die verschiedenen Krankheitsbilder unterschiedliche diagnostische und therapeutische Maßnahmen erfordern. Eine erniedrigte Thrombozytenzahl ist ein starker Prädiktor der Mortalität kritisch kranker Patienten.

Dieser Artikel fasst die Differenzialdiagnose und die diagnostische Aufarbeitung der Thrombopenie in der Intensivmedizin zusammen und gibt einen Überblick über die wichtigsten Krankheitsbilder und die therapeutischen Optionen.

How I evaluate and treat thrombocytopenia in the intensive care unit patient

Multiple causes (pseudothrombocytopenia, hemodilution, increased consumption, decreased production, increased sequestration, and immune-mediated destruction of platelets) alone or in combination make thrombocytopenia very common in intensive care unit (ICU) patients. Persisting thrombocytopenia in critically ill patients is associated with, but not causative of, increased mortality. Identification of the underlying cause is key for management decisions in individual patients. While platelet transfusion might be indicated in patients with impaired platelet production or increased platelet destruction, it could be deleterious in patients with increased intravascular platelet activation. Sepsis and trauma are the most common causes of thrombocytopenia in the ICU. In these patients, treatment of the underlying disease will also increase platelet counts. Heparin-induced thrombocytopenia requires alternative anticoagulation at a therapeutic dose and immune thrombocytopenia immunomodulatory treatment. Thrombocytopenia with symptomatic bleeding at or above World Health Organization grade 2 or planned invasive procedures are established indications for platelet transfusions, while the evidence for a benefit of prophylactic platelet transfusions is weak and controversial. If the platelet count does not increase after transfusion of 2 fresh ABO blood group-identical platelet concentrates (therapeutic units), ongoing platelet consumption and high-titer anti-HLA class I antibodies should be considered. The latter requires transfusion of HLA-compatible platelet concentrates.

[Thrombocytopenia in the intensive care unit : Diagnosis, differential diagnosis, and treatment]

Thrombozytopenie ist ein häufiges Phänomen in der Intensivmedizin. Eine Vielzahl von Ursachen kann für erniedrigte Plättchenzahlen verantwortlich sein. Da Plättchen Teil der primären Hämostase sind, ist Blutungsneigung die wichtigste Komplikation einer Thrombopenie. Strukturiertes Aufarbeiten der Differenzialdiagnose und Identifikation der Ursache ist essenziell, da die verschiedenen Krankheitsbilder unterschiedliche diagnostische und therapeutische Maßnahmen erfordern. Eine erniedrigte Thrombozytenzahl ist ein starker Prädiktor der Mortalität kritisch kranker Patienten.

Dieser Artikel fasst die Differenzialdiagnose und die diagnostische Aufarbeitung der Thrombopenie in der Intensivmedizin zusammen und gibt einen Überblick über die wichtigsten Krankheitsbilder und die therapeutischen Optionen.

Blood Products

Perioperative hemorrhage, anemia, thrombocytopenia, and coagulopathy are common in the surgical intensive care unit. As a result, blood product transfusion occurs frequently. While red blood cell, plasma, and platelet transfusions have a lifesaving role in the resuscitation of patients with trauma and hemorrhagic shock, their application in other settings is under scrutiny. Current data would suggest a conservative approach be taken, thus avoiding unnecessary transfusion and associated potential adverse events. New and developmental products such as prothrombin complex concentrates offer appealing alternatives to traditional transfusion practice—potentially with fewer risks—however, further investigation into their safety and efficacy is required before practice change can take place.

Statistical and prognostic analysis of dynamic changes of platelet count in ICU patients

Laboratory tests are a primary resource to diagnose patient's diseases. However, physicians often make decisions based on the available information, which commonly includes the last test results as a static picture and have limited perspective of the role of trends in commonly measured parameters in enhancing the diagnostic process. By providing a dynamic patient profile the diagnosis could be more accurate and, as a consequence, physicians could anticipate changes in recovery trajectory and prescribe interventions more effectively. Intensive care unit (ICU) patients need continuous monitoring, which commonly includes the assessment of several blood components. One of these components is the platelet count which is used in assessing blood clotting. However, platelet counts represent a dynamic equilibrium of many simultaneous processes including altered capillary permeability, inflammatory cascades, as well as the coagulation process. To characterize the value of dynamic changes in platelet counts we applied analytic methods to datasets of critically ill patients in (i) a homogeneous population of ICU cardiac surgery patients, where an observation appears to be predictive of patient's complications and mortality and (ii) a heterogeneous group of ICU patients to confirm the previous observation.

[Coagulation disorders in the intensive care station]

Coagulation disorders are frequently encountered in the intensive care unit (ICU) and are challenging due to a variety of potential etiologies. Critically ill patients with coagulation abnormalities may present with an increased risk of bleeding, show coagulation activation resulting in thromboembolism, or have no specific symptoms. Hemostatic abnormalities observed in ICU patients range from isolated thrombocytopenia or prolonged global clotting tests to complex and life-threatening coagulation defects. Successful management of coagulation disorders requires prompt and accurate identification of the underlying cause. This review describes the most frequently occurring diagnoses found in intensive care patients with thrombocytopenia and coagulation test abnormalities and summarizes appropriate diagnostic interventions and current approaches to differential diagnosis.

Mechanisms and etiologies of thrombocytopenia in the intensive care unit: impact of extensive investigations

BACKGROUND

Thrombocytopenia is common in the intensive care unit. Potential mechanisms and etiologies behind this phenomenon are multiple and often entangled. We assessed the effect of a systematic approach, using routinely available tests, on the proportion of patients in whom the mechanism (primary objective) and etiology (secondary objective) of thrombocytopenia in a mixed intensive care unit (ICU) could be identified.

METHODS

Before-and-after study of all patients with thrombocytopenia was used. 'Before' group had no intervention. New standard operating procedures for thrombocytopenia management were introduced. In the 'After' group, bone marrow aspiration; determination of fibrinogen dosage, prothrombin time, factor V, D-dimers; assay of fibrin monomers, ferritin, triglycerides, lactic acid dehydrogenase, aspartate transaminase, alanine aminotransferase, vitamin B12, folates, reticulocytes, haptoglobin, and bilirubin were performed.

RESULTS

In the Before group (n = 20), the mechanism (central, peripheral, or mixed) was identified in 10 % versus 83% in After group (n = 23) (p < 0.001) (48% peripheral, 35% mixed). Before intervention, ≥1 etiology was identified in 15% versus 95.7% in the After group (p < 0.001).

CONCLUSIONS

Systematic and extensive investigation using routine tests highlights the mechanisms and etiology of thrombocytopenia in most cases.

Thrombocytopenia is associated with acute respiratory distress syndrome mortality: an international study

Background

Early detection of the Acute Respiratory Distress Syndrome (ARDS) has the potential to improvethe prognosis of critically ill patients admitted to the intensive care unit (ICU). However, no reliable biomarkers are currently available for accurate early detection of ARDS in patients with predisposing conditions.

Objectives

This study examined risk factors and biomarkers for ARDS development and mortality in two prospective cohort studies.

Methods

We examined clinical risk factors for ARDS in a cohort of 178 patients in Beijing, China who were admitted to the ICU and were at high risk for ARDS. Identified biomarkers were then replicated in a second cohort of1,878 patients in Boston, USA.

Results

Of 178 patients recruited from participating hospitals in Beijing, 75 developed ARDS. After multivariate adjustment, sepsis (odds ratio [OR]:5.58, 95% CI: 1.70–18.3), pulmonary injury (OR: 3.22; 95% CI: 1.60–6.47), and thrombocytopenia, defined as platelet count <80×10³/µL, (OR: 2.67; 95% CI: 1.27–5.62)were significantly associated with increased risk of developing ARDS. Thrombocytopenia was also associated with increased mortality in patients who developed ARDS (adjusted hazard ratio [AHR]: 1.38, 95% CI: 1.07–1.57) but not in those who did not develop ARDS(AHR: 1.25, 95% CI: 0.96–1.62). The presence of both thrombocytopenia and ARDS substantially increased 60-daymortality. Sensitivity analyses showed that a platelet count of <100×10³/µLin combination with ARDS provide the highest prognostic value for mortality. These associations were replicated in the cohort of US patients.

Conclusions

This study of ICU patients in both China and US showed that thrombocytopenia is associated with an increased risk of ARDS and platelet count in combination with ARDS had a high predictive value for patient mortality.

Active exercise in critically ill adults affected by thrombocytopaenia

Introduction

Thrombocytopaenia (TCP), or low platelet count, is a haematological disorder that commonly occurs in critically ill patients and is defined as a platelet count below 100 000/μL. Patients are at higher risk of muscular atrophy and other complications after prolonged bed rest. This literature review aims to clarify the appropriateness of active exercise in critically ill adult patients with TCP.

Methods

A review of the literature was conducted using the following key words that are PubMed medical subheading (MeSH) terms: ‘critical illness’, ‘exercise therapy’, ‘manual therapy’, ‘physical therapy’, ‘physiotherapy’, ‘postoperative care’, ‘rehabilitation’, ‘thrombocytopenia’, and ‘thrombopenia’. The search was limited by publication date (2000 to 2013) and language (English only) in three main databases: PubMed, SCOPUS, and CINAHL.

Results

The key word searches found a total of 78 citations. Of these, only those meeting the inclusion criteria were selected after reading the title and abstract. Two studies were included after reading the full-texts. Exercise is used to treat muscular atrophy in critically ill adult patients, and rehabilitation plays an important role in the care pathway. Results of our analysis do not support evidence for or against exercise in critically ill adult patients with TCP; therefore, health professionals must pay close attention to the presence of signs of bleeding in these patients when proposing exercise.

Discussion

Surprisingly, no study was found that directly covered this issue. Aggressive exercise may not be appropriate in patients with very low platelet counts. On the other hand, critically ill patients are at high risk of muscular atrophy due to the forced bed rest, especially after complex surgery or in prolonged hospitalisation. Physiotherapists and those providing care must share their observations with the rest of the multidisciplinary team before treatment starts.

Conclusions

Active exercise in critically ill adult patients with severe TCP must be personalised and platelet count carefully monitored before proposing physical activity. Physical recovery can be challenging in critically ill adult patients, and it can be limited by severe TCP, mostly when bleeding is present.

Percutaneous Tracheostomy Can be Safely Performed in Patients with Uncorrected Coagulopathy after Cardiothoracic Surgery

Objective

It is a common situation after cardiothoracic surgery that a tracheostomy is required for patients who are coagulopathic or on therapeutic anticoagulation. We present our results of percutaneous tracheostomy with uncorrected coagulopathy.

Methods

Between 2007 and 2012, a total of 149 patients in our Cardiothoracic Surgical Intensive Care Unit underwent percutaneous tracheostomy using the Ciaglia Blue Rhino system (Cook Medical, Bloomington, IN USA). The patients were divided into coagulopathic (platelets, ≤50,000; international normalized ratio of prothrombin time, ≥1.5; and/or partial thromboplastin time, ≥50) and noncoagulopathic groups. Coagulopathy, if present before percutaneous tracheostomy, was not routinely corrected.

Results

A total of 75 patients (49%) were coagulopathic. Twenty-one patients (14%) had two or more criteria. The coagulopathic patients had a lower platelet count [108 (106) vs 193 (111) (thousands), P < 0.001], with the lowest of 10; higher international normalized ratio of prothrombin time [1.7 (0.6) vs 1.2 (0.1), P < 0.001], with the highest of 5.3; longer partial thromboplastin time [40 (13) vs 33 (7) seconds, P < 0.001], with the longest of 85; and higher total bilirubin [4.6 (7.3) vs 1.9 (3.3) mg/dL, P = 0.005]. Patient demographics and comorbidities were comparable between the groups. No patients had overt bleeding. One coagulopathic patient (1.3%) had clinical oozing treated with packing, as opposed to zero in the noncoagulopathic patients ( P = 1.00). There were no patients with posttracheostomy mediastinitis or late tracheal stenosis.

Conclusions

Uncorrected coagulopathy and therapeutic anticoagulation did not increase bleeding risk for percutaneous tracheostomy in our cardiothoracic surgical patients.

Hematologic Complications

Critically ill patients are at high risk of developing various hematologic complications that may be present on admission or occur during their stay in the Intensive Care Unit (ICU). Often times the etiology of specific hematologic abnormalities is unclear and the diagnosis may be challenging due to the complexity of critically ill patients. This chapter will focus on diagnosis and management of the most commonly encountered hematologic problems in the critically ill such as anemia, neutropenia, thrombocytopenia, coagulopathy and thrombotic complications, with specific focus on diagnosis and management of these conditions.

Relationship between the 4Ts scoring system and the antiplatelet factor 4/heparin antibodies test in critically ill patients

Aim

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction and potentially progresses to fatal thrombosis. The 4Ts scoring system has been reported as a clinical pretest for HIT. However, its usefulness in critically ill patients has not yet been thoroughly examined. Thus, we evaluated the clinical usefulness of the 4Ts score in the diagnosis of HIT in critically ill patients.

Methods

One hundred and four critically ill patients who were admitted to our intensive care unit and who underwent the antiplatelet factor 4/heparin complex antibodies (PF4/heparin Ab) test with suspected HIT were enrolled in the study. The primary endpoint variable was the 4Ts score. The secondary endpoint variables were laboratory data, length of stay, and mortality, compared between thePF4/heparin Ab positive and negative groups.

Results

There was no significant difference in the 4Ts scores between the PF4/heparin Ab positive and negative groups. The positive predictive value (HIT patients/4T high score patients) was 15.4% (2/13), the negative predictive value (non-HIT patients/4T low score patients) was 87.5% (42/48), and the false-negative rate for the 4Ts score (4T low score patients/HIT patients) was as high as 54.5% (6/11). The PF4/heparin Ab positive patients had longer stay in intensive care compared to the PF4/heparin Ab negative patients (P = 0.035).

Conclusions

The present study showed the discrepancy between the 4Ts score and PF4/heparin Ab. When HIT is suspected in critically ill patients, an immediate HIT antibody test and initiation of therapeutic management of HIT are required regardless of the 4Ts score.

The potential of antimicrobials to induce thrombocytopenia in critically ill patients: data from a randomized controlled trial

BACKGROUND

Antimicrobial-induced thrombocytopenia is frequently described in the literature among critically ill patients. Several antimicrobials have been implicated, although experimental evidence to demonstrate causality is limited. We report, using a randomized trial, the potential of antimicrobials to induce thrombocytopenia.

METHODS

Randomized trial allocated patients to antimicrobial treatment according to standard- of-care (SOC group) or drug-escalation in case of procalcitonin increases (high-exposure group). Patients were followed until death or day 28. Thrombocytopenia defined as absolute (platelet count ≤ 100 x 109/L) or relative (≥ 20% decrease in platelet count). Analyses were performed in the two randomized groups and as a merged cohort.

RESULTS

Of the 1147 patients with platelet data available, 18% had absolute thrombocytopenia within the first 24 hours after admission to intensive care unit and additional 17% developed this complication during follow-up; 57% developed relative thrombocytopenia during follow-up. Absolute and relative thrombocytopenia day 1-4 was associated with increased mortality (HR: 1.67 [95% CI: 1.30 to 2.14]; 1.71 [95% CI: 1.30 to 2.30], P<0.0001, respectively). Patients in the high-exposure group received more antimicrobials including piperacillin/tazobactam, meropenem and ciprofloxacin compared with the SOC group, whereas cefuroxime was used more frequently in the SOC group (p<0.05). Risk of absolute and relative thrombocytopenia (RR: 0.9 [0.7-1.3], p=0.7439; 1.2 [1.0-1.4], p=0.06; respectively), as well as absolute platelet count (daily difference, high-exposure vs. SOC -1.7 [-3.8-0.5], p=0.14) was comparable between groups. In observational analyses, use of ciprofloxacin and piperacillin/tazobactam predicted risk of relative thrombocytopenia (vs. cefuroxime, RR: 2.08 [1.48-2.92]; 1.44 [1.10-1.89], respectively), however only ciprofloxacin were associated with a reduction in absolute platelet count (p=0.0005).

CONCLUSION

High exposure to broad-spectrum antimicrobials does not result in a reduction in thrombocytopenia in critically ill patients. However, single use of ciprofloxacin, and less so piperacillin/tazobactam, may contribute to a lower platelet count.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00271752 http://clinicaltrials.gov/ct2/show/NCT00271752.

Coagulopathy in the intensive care unit

Coagulopathy is a potential problem for many critically ill patients, placing them at risk for hemorrhage. Critical illness activates both hemostasis and the inflammatory-immune system, leading to both physiological and potentially pathophysiological responses. Following complex surgery or trauma, patients are at high risk for development of problems such as thrombocytopenia and postoperative bleeding, challenging nurses to recognize and manage these problems. The clinical manifestations of coagulopathy may be obvious or occult, and correlation with the coagulation panel results is a complex process. Transfusion of blood and components has long been an important part of patient management, but is known to put patients at risk for transfusion-related complications. Current clinical practice guidelines provide blood conservation strategies and criteria to guide decisions on transfusion therapy.

Barriers to effective diagnosis and management of a bleeding patient with undiagnosed bleeding disorder across multiple specialties: results of a quantitative case-based survey

Background:

Bleeding symptoms commonly seen by multiple physician specialties may belie undiagnosed congenital or acquired bleeding disorders. Acquired hemophilia is a potentially life-threatening cause of unexplained acute bleeding manifested by an abnormal activated partial thromboplastin time (aPTT) that does not correct with 1:1 mixing with normal plasma.

Methods:

Practicing physicians (hematology/oncology, emergency medicine, geriatrics, internal medicine, rheumatology, obstetrics and gynecology, critical care medicine, and general surgery) completed an online survey based on a hypothetical case scenario.

Results:

Excluding surgeons and obstetrician/gynecologist respondents, 302 physicians (about 50 per specialty) were presented with an older adult woman complaining of recurrent epistaxis. Nearly 90% ordered a complete blood count and coagulation studies (aPTT, prothrombin time [PT]/international normalized ratio [INR]). Despite a prolonged aPTT of 42 seconds, <50% of nonhematologists would repeat the aPTT, and <45% would consult a hematologist; emergency medicine physicians were least likely (10%) and rheumatologists were most likely (43%) to consult. After presentation weeks later with bruising and abdominal/back pain, ≥90% of physicians within each specialty ordered a complete blood count or PT/INR/aPTT. Despite an aPTT of 63 seconds, the majority did not repeat the aPTT. At this point, approximately 75% of internal medicine and geriatric physicians indicated they would consult a hematologist, versus 47% in emergency medicine and 50% in critical care. All participants preferred abdominal computed tomography (80%–84%). After 12 hours of additional observation, 73% to 94% of respondents consulted a hematologist. Complete blood count revealed anemia and an aPTT twice the upper limit of normal; emergency medicine physicians remained least likely to request a consult.

Conclusion:

Determining the cause of an abnormal coagulation study result should carry equal weight as looking for the site of bleeding and could be facilitated by consultation with a hematologist. Insight from this survey highlights knowledge and practice gaps that could be the target of focused educational initiatives.

Why does my patient have thrombocytopenia?

Thrombocytopenia, usually defined as a platelet count of less than 150,000/μL, is a common reason for a hematology consult in both the inpatient and outpatient setting. In most patients, the cause of the thrombocytopenia can be identified and treated. This article reviews the clinical approach to the patient with thrombocytopenia, the mechanisms that underlie it, and the laboratory tests available to investigate it. A practical approach to the investigation and management of thrombocytopenia in the clinical settings commonly encountered by the hematology consultant is then described.

A Case of Thrombocytopenia due to Odontogenic Infection

Thrombocytopenia in surgical patients is a potentially serious condition,faced by surgeons. A close relationship between sepsis and thrombocytopenia has been suggested. Thrombocytopenia has even been suggested to be indicative of an acute infection. Platelet count in a septicemic patient may also serve as a prognostic tool. There are many reports of thrombocy-topenia due to septicemia in the literature but the occurrence of thrombocytopenia in maxillofacial infections is rare. Thrombocytopenia in a patient with odontogenic infection presents unique diagnostic and management challenges. A case report of an adult male patient with odontogenic infection, who developed life-threatening thrombocytopenia, is presented.

Venous thromboembolism in coagulopathic surgical intensive care unit patients: is there a benefit from chemical prophylaxis?

BACKGROUND

Coagulation abnormalities in critically ill surgical patients cause confusion in administration of venous thromboembolism (VTE) prophylaxis. Pharmaceutical VTE prophylaxis is often withheld because of presumed increased risk for bleeding and assumption that these patients would not benefit from it. Coagulopathic critically ill surgical patients are at risk for VTE and should be treated with chemical prophylaxis.

METHODS

A retrospective review was performed of all coagulopathic patients (international normalized ration >1.5 or platelets <100,000 per μL) admitted for at least 72 hours to the surgical intensive care units of a tertiary care center between January 2008 and January 2009. Patients were divided into two groups based on providing (group 1) or withholding (group 2) chemical prophylaxis. The incidence of VTE was then compared between the two groups.

RESULTS

A total of 513 patients were included in the study: 241 patients in group 1 and 272 patients in group 2. The overall incidence of VTE was 16.4%. The incidence of VTE in the patients who received chemical prophylaxis was 17.0%, whereas the incidence in patients without chemical prophylaxis was 15.8% (p = 0.72).

CONCLUSION

Coagulopathic critically ill surgical patients remain at significant risk for VTE. Unfortunately, chemical VTE prophylaxis does not seem to decrease this risk. Further research is warranted to investigate the nature of this increased risk of VTE and the reason chemical VTE prophylaxis has no benefit.

Advanced assessment of platelet function during adult donor care

Abnormal platelet function may complicate the assessment and treatment of continuing blood loss, hypotension, and coagulation disorders during adult donor care. Antiplatelet drugs, such as aspirin, nonsteroidal anti-inflammatory drugs, clopidogrel (Plavix), ticlopidine (Ticlid), prasugrel (Effient), abciximab (ReoPro), eptifibatide (Integrilin), and tirofiban (Aggrastat) are commonly prescribed for older patients. These medications may be part of home therapy or may be given during acute cardiac or cerebrovascular crises that may lead to brain death and organ donation. This discussion reviews normal platelet formation and function, drug actions, methods to evaluate medication effects, pharmacological characteristics, treatment recommendations for platelet transfusion, and risks attendant with those infusions.

Acquired hemophilia: a rare but life-threatening potential cause of bleeding in the intensive care unit

OBJECTIVE

There are a number of potential etiologies of severe bleeding encountered in the intensive care unit. Although rare, acquired hemophilia is one such etiology that often presents with major bleeding requiring intensive care. Despite the introduction of effective treatments, the reported mortality rate of patients with acquired hemophilia ranges from 6 to 8% and is in part attributable to sequential delays in diagnosis and appropriate treatment. The purpose of this review is to familiarize the intensive care specialist with this underrecognized cause of bleeding, with an emphasis on diagnosis and treatment.

METHODS

As the objective of this article was to provide a concise overview of the diagnosis and management of acquired hemophilia, a directed search of English-language literature was undertaken using the PubMed database, targeting such topics as the differential diagnosis of bleeding in the intensive care unit and the epidemiology, diagnosis, and treatment of acquired hemophilia. Clinical study findings pertaining to the efficacy of specific treatments for acquired hemophilia were summarized.

RESULTS AND CONCLUSION

Recognition of acquired hemophilia presents a clinical challenge, given the rarity of this condition, a general lack of familiarity with acquired hemophilia, and the potential for confusion with other more common causes of bleeding in the intensive care unit. Nevertheless, there are sentinel clinical and laboratory findings that should raise suspicion of this diagnosis. The treatment of acquired hemophilia is a multi-step, physiologically focused process aimed at controlling both active and recurrent bleeding. Therefore, prompt diagnosis is central to prognosis. Consultation with a hematologist may facilitate efficient diagnosis and management.

An experimental model to study isolated effects of thrombin in vivo

BACKGROUND

In addition to a recognized role in the coagulation cascade and haemostasis, thrombin is known to have multiple functions. We hypothesized that protracted intravenous infusion of thrombin at steady state will allow to study isolated thrombin effects in vivo.

METHODS

Thrombin (0.05-0.9U/kg/min) was continuously infused in Sprague Dawley rats over five hours (n=38). The study consisted of three parts: dose escalation (n=21), dose verification (n=5) and a parallel group study to investigate whether thrombin effects can be antagonised by concomitant infusion of lepirudin (n=12).

RESULTS

A thrombin dose of 0.9U/kg/min decreased platelet counts by 70% compared to the control group (median 230×10^9/L vs. 752×10^9/L; p=0.041). In accordance, infusion of 0.9U/kg/min of thrombin decreased fibrinogen level by 75% compared to the control group (56mg/dl vs. 220mg/dl; p=0.046). Cumulative thrombin doses of ≥0.1U/kg/min caused bleedings but not thromboembolic events. Thrombin at doses ≥0.15U/kg/min was lethal in four cases (30%). Platelet counts and fibrinogen levels after thrombin infusion correlated with bleeding events and mortality. Administration of thrombin at cumulative doses of 0.3-0.9U/kg/min was associated with a 3 to 6.5 -fold increase in IL-6 levels (139-306pg/ml vs. 47pg/ml, p<0.05). In contrast, thrombin infusion did not alter other markers of inflammation (IL-10, MCP-1 or TNF-alpha). In addition, lepirudin prevented thrombin- induced thrombocytopenia.

CONCLUSION

Protracted intravenous infusion of thrombin offers a new experimental model, where consumption of fibrinogen and platelets correlates with bleedings and mortality. Infusion of thrombin increased only IL-6 levels but not other cytokines.