Interpretation of Viscoelastic Hemostatic Assays in Cardiac Surgery Patients: Importance of Clinical Context

BACKGROUND

Rotational thromboelastometry (ROTEM) is widely used for point-of-care coagulation testing to reduce blood transfusions. Accurate interpretation of ROTEM data is crucial and requires substantial training. This study investigates the inter- and intrarater reliability of ROTEM interpretation among experts and compares their interpretations with a ROTEM-guided algorithm.

METHODS

This study was conducted at Amsterdam University Medical Center and included 90 cardiac surgery patients. ROTEM data were collected at 4 surgical stages: before induction, after aortic declamping, postcoagulation correction, and within 2 hours of intensive care unit (ICU) admission. An international panel of 7 cardiovascular anesthesiologists and one intensivist interpreted the data. Interrater reliability was assessed using Fleiss' kappa for binary decisions and the simple matching coefficient (SMC) for multiple-choice questions. Intrarater reliability with the ROTEM-guided algorithm was also evaluated.

RESULTS

Three hundred forty-three ROTEM measurements were analyzed. The interrater reliability for binary decisions was substantial to almost perfect, except after declamping (Fleiss' kappa = 0.34). The SMC for determining type of abnormality and interventions ranged from good to excellent across all ROTEM measuring moments (SMC ≥0.75). Intrarater reliability was almost perfect for binary questions (intraclass correlation coefficient [ICC] ≥0.81) and showed excellent agreement for multiple-choice questions. Comparing expert recommendations with the algorithm resulted in an average SMC of 0.70 indicating differences in intervention recommendations, with experts frequently recommending fibrinogen and protamine over the algorithm's suggestions of plasma and PCC.

CONCLUSIONS

This study demonstrates high inter- and intrarater reliability in ROTEM interpretation among trained professionals in cardiac surgery, with almost perfect agreement on abnormalities and interventions. However, differences between expert evaluations and the ROTEM-guided algorithm underscore the need for advanced clinical decision-making tools. Future efforts should focus on developing personalized, data-driven algorithms without predefined cutoff values to improve accuracy and patient outcomes.

Pathogen Reduction Technologies and Their Impact on Metabolic and Functional Properties of Treated Platelet Concentrates: A Systematic Review

Pathogen reduction technologies (PRTs) such as Mirasol and Intercept were developed to eliminate transfusion-transmitted infections. The impact of PRTs on platelet function during the storage period, their effect on platelet storage lesions, and the optimal storage duration following PRTs have not been clearly defined. The aim of this study was to systematically review the existing literature and investigate the impact of PRTs on functional alterations of PRT-treated platelets during the storage period. The authors identified 68 studies suitable to be included in this review. Despite the high heterogeneity in the literature, the results of the published studies indicate that PRTs may increase platelet metabolic activity, accelerate cell apoptosis, and enhance platelet activation, which can subsequently lead to a late exhaustion of activation potential and reduced aggregation response. However, these effects have a minor impact on platelet function during the early storage period and become more prominent beyond the fifth day of the storage period. Large in vivo trials are required to evaluate the effectiveness of PRT-treated platelets during the storage period and investigate whether their storage can be safely extended to more than 5 days, and up to the traditional 7-day storage period.

Clinical application of viscoelastic point-of-care tests of coagulation-shifting paradigms

Bleeding during cardiac surgery, liver transplant, trauma and post partum hemorrhage are often multifactorial and these factors are dynamic as new factors crop up during the course of management. Conventional tests of coagulation offer information of a part of the coagulation system and also is time consuming. Viscoelastic point of care tests (VE POCTs) like rotational thromboelastometry, thromboelastogram and Sonoclot, are based on analysis of the viscoelastic properties of clotting blood and provide information for the entire coagulation pathway. In this comprehensive review being presented here, we have examined the pros and cons of VE POCTs including clinical, cost and survival benefits. The recommendations of the various guidelines regarding use of VE POCTs in various scenarios have been discussed. The review also tried to offer suggestions as to their optimal role in management of bleeding during cardiac surgeries, extracorporeal membrane oxygenation, left ventricular assist devices, liver transplant and briefly in trauma and postpartum hemorrhage.

Coagulopathy, Bleeding Events, and Outcome According to Rotational Thromboelastometry in Patients With Acute Liver Injury/Failure

BACKGROUND AND AIMS

Patients with acute liver injury or failure (ALI/ALF) experience bleeding complications uncommonly despite an abnormal hemostatic profile. Rotational thromboelastometry (ROTEM), which assesses clot formation in whole blood, was used to determine the nature of abnormal hemostasis and whether it contributes to bleeding events, illness severity, or survival.

APPROACH AND RESULTS

A total of 200 patients were recruited from sites of the ALF Study Group. Blood collected daily for up to 5 days was analyzed using ROTEM delta devices. Consistent with standard laboratory evidence of hypocoagulability (median international normalized ratio = 2.9 and platelet count = 144 × 109 /L), patients frequently exhibited ROTEM parameters outside the normal range (73% and 62% had abnormalities in clot formation from extrinsic and intrinsic clotting cascades, respectively); however, measures of clot stability were generally normal. Eighteen patients (9%) experienced bleeding events, in whom clot initiation, assembly, and firmness were more severely deranged than patients without bleeding. Abnormal ROTEM parameters were more frequently observed in patients with non-acetaminophen ALI/ALF than those with acetaminophen ALI/ALF (clot initiation [P < 0.001], assembly [P = 0.02], firmness at 10 minutes [P = 0.05], and maximal firmness [P = 0.06]). Patients with more severe systemic complications (high-grade hepatic encephalopathy and need for renal replacement therapy) also had a higher incidence of abnormal ROTEM parameters. Finally, more hypocoagulable ROTEM parameters (clot initiation (P = 0.005), stiffness at 10 minutes (P = 0.05), and maximal stiffness by fibrin assembly (P = 0.004)) were observed in patients who died or underwent liver transplantation than those who survived with their native liver.

CONCLUSIONS

In patients with ALI/ALF, abnormal ROTEM parameters are frequent and proportional to disease severity. Whether the increased bleeding risk associated with abnormal ROTEM indicates hemostatic failure or is a proxy for disease severity requires additional study.

Role of Thromboelastography and Rotational Thromboelastometry in the Management of Cardiovascular Diseases

The monitoring of coagulation by viscoelastometric methods—thromboelastography and rotational thromboelastometry—may detect the contributions of cellular and plasma components of hemostasis. These methods might overcome some of the serious limitations of conventional laboratory tests. Viscoelastic testing can be repeatedly performed during and after surgery and thus provides a dynamic picture of the coagulation process during these periods. Several experiences with the use of these methods in cardiovascular surgery have been reported, but there is perspective for more frequent use of these assays in the assessment of platelet response to antiplatelet therapy and in the assessment of coagulation in patients on long-term dabigatran therapy. This article reviews the current role and future perspectives of thromboelastography and thromboelastometry in the management of cardiovascular diseases.

Screening for platelet function disorders with Multiplate and platelet function analyzer

Light transmission aggregation (LTA) is the gold standard for the diagnosis of platelet function disorders (PFDs), but it is time-consuming and limited to specialized laboratories. Whole-blood impedance aggregometry (Multiplate) and platelet function analyzer (PFA) may be used as rapid screening tools to exclude PFDs. The aim of this study is to assess the diagnostic performance of Multiplate and PFA for PFDs, as detected by LTA.Data from preoperative patients, patients referred to the hematologist for bleeding evaluation, and patients with a diagnosed bleeding disorder were used. PFDs were defined as ≥2 abnormal LTA curves. Diagnostic performance of Multiplate and PFA for detecting PFDs was expressed as sensitivity and specificity. The ability of Multiplate agonists and PFA kits to detect corresponding LTA curve abnormalities was expressed as area under the receiver operating characteristic curve. Prevalence of PFDs was 16/335 (4.8%) in preoperative patients, 10/54 (18.5%) in referred patients, and 3/25 (12%) in patients with a diagnosed bleeding disorder. In preoperative and referred patients, the sensitivity of Multiplate and PFA for detecting mild PFDs varied between 0% and 40% and AUCs for detecting corresponding LTA curve abnormalities were close to 0.50. In patients with a diagnosed bleeding disorder, both assays could detect Glanzmann thrombasthenia (GT) with sensitivity of 100% and AUCs of 0.70-1.00. Multiplate and PFA cannot discriminate between preoperative and referred patients with and without mild PFDs, meaning that they cannot be used as screening tests to rule out mild PFDs in these populations. Both Multiplate and PFA can detect GT in previously diagnosed patients.

Near-patient coagulation testing to predict bleeding after cardiac surgery: a cohort study

BACKGROUND

Coagulopathic bleeding is common after cardiac surgery and is associated with increased morbidity, mortality and healthcare costs. Implementation of blood management algorithms in which patients with severe bleeding undergo near-patient coagulation testing results in less overall bleeding and transfusion. However, it is unknown whether there is additional value from pre-emptive near-patient testing to predict whether severe bleeding will occur.

OBJECTIVES

To evaluate how well a comprehensive panel of 28 near-patient platelet and viscoelastometry tests predict bleeding after cardiac surgery, compared to prediction using baseline clinical characteristics alone.

METHODS

Single-center, prospective cohort study in adults undergoing a range of cardiac surgery procedures. The primary outcome was clinical concern about bleeding (CCB), a composite of high blood loss (chest drain volume >600 mL within 6 hours), re-operation for bleeding or administration of a pro-haemostatic treatment directed by clinician judgement.

RESULTS

In 1833 patients recruited between March 2010 and August 2012, the median number of abnormal near-patient test results was 5/28 per patient (range 0-18). CCB occurred in 449/1833 patients (24.5%). The c-statistic for a predictive model for CCB using only baseline clinical characteristics (baseline-only model) was 0.72 (95% CI 0.69-0.75). Addition of near-patient test results to this model (baseline-plus-test model) improved the prediction of CCB (c-statistic 0.75 [0.72-0.77]), but increased the number of correctly classified patients by only 18 (0.98%).

CONCLUSIONS

Near-patient coagulation testing predicts bleeding in cardiac surgery patients, but offers little improvement in prediction compared to baseline clinical characteristics alone. trial registration: ISRNCTN 20778544 (http://www.isrctn.com/).

Preoperative thromboelastometry for the prediction of increased chest tube output in cardiac surgery: A retrospective study

Bleeding following cardiac surgery is a serious event with potentially life-threatening consequences. Preoperative recognition of coagulation abnormalities and detection of cardiopulmonary bypass (CPB) related coagulopathy could aid in the start of preventive treatment strategies that minimize perioperative blood loss. Most algorithms that analyze thromboelastometry coagulation tests in elective cardiac surgery do not include test results performed before surgery. We evaluated preoperative rotational thromboelastometry test results for their ability to predict blood loss during and after cardiac surgery.A total of 114 adult patients undergoing cardiac surgery with CPB were included in this retrospective analysis. Each patient had thromboelastometry tests done twice: preoperatively, before the induction of anesthesia and postoperatively, 10 minutes after heparin reversal with protamine after decannulation.Patients were placed into 1 of 2 groups depending on whether preoperative thromboelastometry parameters deviated from reference ranges: Group 1 [N = 29; extrinsically activated test (EXTEM) or INTEM results out of normal range] or Group 2 (N = 85; EXTEM and INTEM results within the normal range). We observed that the total amount of chest tube output was significantly greater in Group 1 than in Group 2 (700 mL vs 570 mL, P = .03). At the same time, the preoperative values of standard coagulation tests such as platelet count, aPTT, and INR did not indicate any abnormalities of coagulation.Preoperative coagulation abnormalities diagnosed with thromboelastometry can predict increased chest tube output in the early postoperative period in elective adult cardiac surgery. Monitoring of the coagulation system with thromboelastometry allows rapid diagnosis of coagulation abnormalities even before the start of the surgery. These abnormalities could not always be detected with routine coagulation tests.

Prothrombin Complex Concentrates in Pediatric Cardiac Surgery: The Current State and the Future

BACKGROUND

After decades of practice of pediatric cardiac surgery, postoperative bleeding due to the immaturity of hemostasis, hemodilution, and hypothermia remains a concern. Recently, a new approach for adult coagulopathy after bypass has emerged. Prothrombin complex concentrates (PCCs), designed to treat bleeding in hemophilia patients, are safely and efficiently used off label for hemorrhage after bypass. However, optimal dosing, indications and contraindications, and laboratory tests to assess the efficacy of PCC use in children have not yet been established. This literature review outlines the challenges of bypass-related coagulopathy, the pharmacology, and the experience in use of PCCs, with a focus on their potential in pediatric cardiac surgery.

METHODS

After a thorough literature search of MEDLINE, Scopus, and Ovid databases using the term "prothrombin complex concentrate AND pediatric," 23 relevant articles were selected.

RESULTS

The data supporting successful use of PCCs in acquired coagulopathy after cardiac surgery in adults have been increasing. Although small volume, low immunogenicity, efficiency, and speed in correcting coagulopathy are attractive qualities of PCCs for pediatric practice, current evidence is only anecdotal. The main concerns are unknown dosing regimens, the inability to closely monitor the effects of PCCs in real time, and a possibility of thrombotic complications, which can be particularly devastating in young congenital cardiac patients whose lives frequently depend upon the patency of artificial shunts.

CONCLUSIONS

Extensive, high-quality research is warranted to fill in the gaps of knowledge regarding using PCCs in pediatric cardiac practice.

Anticoagulant Effect of Sugammadex: Just an In Vitro Artifact

BACKGROUND

Sugammadex prolongs activated partial thromboplastin time (aPTT) and prothrombin time (PT) suggestive of anticoagulant effects. To pinpoint its presumed anticoagulant site of action, the authors assessed Sugammadex's impact on a panel of coagulation assays.

METHODS

Sugammadex, Rocuronium, Sugammadex and Rocuronium combined, or saline were added to blood samples from healthy volunteers and analyzed using plasmatic (i.e., aPTT, thrombin time, and fibrinogen concentration) (n = 8 each), PT (quick), activities of plasmatic coagulation factors, and whole blood (extrinsically and intrinsically activated thromboelastometry) assays (n = 18 each). Furthermore, dose-dependent effects of Sugammadex were also assessed (n = 18 each) in diluted Russel viper venom time (DRVVT) assays with low (DRVVT1) and high (DRVVT2) phospholipid concentrations and in a highly phospholipid-sensitive aPTT assay.

RESULTS

Sugammadex increased PT (+9.1%; P < 0.0001), aPTT (+13.1%; P = 0.0002), and clotting time in extrinsically (+33.1%; P = 0.0021) and intrinsically (+22.4%; P < 0.0001) activated thromboelastometric assays. Furthermore, activities of factors VIII, IX, XI, and XII decreased (-7%, P = 0.009; -7.8%, P < 0.0001; -6.9%, P < 0.0001; and -4.3%, P = 0.011, respectively). Sugammadex dose-dependently prolonged both DRVVT1 and the highly phospholipid-sensitive aPTT assays, but additional phospholipids in the DRVVT2 assay almost abolished these prolongations. Thrombin time, a thromboelastometric thrombin generation assay, clot firmness, clot lysis, fibrinogen concentration, and activities of other coagulation factors were unaltered. Rocuronium, Sugammadex and Rocuronium combined, and saline exerted no effects.

CONCLUSION

Sugammadex significantly affects various coagulation assays, but this is explainable by an apparent phospholipid-binding effect, suggesting that Sugammadex`s anticoagulant effects are likely an in vitro artifact.

Impaired Platelet Aggregation and Rebalanced Hemostasis in Patients with Chronic Hepatitis C Virus Infection

Increased risk of both cardiovascular disease (CVD) and bleeding has been found in patients with chronic hepatitis C (CHC) infection, and a re-balanced hemostasis has been proposed. The aim of this study was to investigate functional whole blood coagulation and platelet function in CHC infection. The prospective study included 82 patients with CHC infection (39 with advanced liver fibrosis and 43 with no or mild liver fibrosis) and 39 healthy controls. A total of 33 patients were treated for CHC infection and achieved sustained virological response (SVR). Baseline and post-treatment blood samples were collected. Hemostasis was assessed by both standard coagulation tests and functional whole blood hemostatic assays (thromboelastograhy (TEG), and platelet aggregation (Multiplate). Patients with CHC and advanced fibrosis had impaired platelet aggregation both compared to patients with no or mild fibrosis and to healthy controls. Patients with CHC and advanced fibrosis also had lower antithrombin, platelet count, and coagulation factors II-VII-X compared to healthy controls. In contrast, TEG did not differ between groups. In treated patients achieving SVR, post-treatment platelet count was higher than pre-treatment counts (p = 0.033) and ADPtest, ASPItest, and RISTOhightest all increased post treatment (all p < 0.05). All Multiplate tests values, however, remained below those in the healthy controls. CHC-infected patients displayed evidence of rebalanced hemostasis with only partly hemostatic normalization in patients achieving SVR. The implications of rebalanced hemostasis and especially the impact on risk of CVD and bleeding warrants further studies.

Platelet reactivity in thromboelastometry. Revision of the FIBTEM test: a basic study

This study aimed to investigate modifications to the FIBTEM test to better assess fibrinogen levels and the quality of fibrin polymerization in citrated blood using Multiplate impedance aggregometry to verify platelet inhibition. Blood samples from 26 healthy volunteers were subjected to thromboelastometry studies (EXTEM/FIBTEM tests) in accordance with the standard study protocol (cytochalasin D) and according to a modified protocol (synthetic IIbIIIa receptor antagonist vs. acetylsalicylic acid [ASA] + synthetic IIbIIIa receptor antagonist instead of cytochalasin D). Independent of thromboelastometry, Multiplate impedance aggregometry was used to assess the degree of restriction by the platelet blocked with the following treatments: (1) cytochalasin D, (2) synthetic IIbIIIa antagonist or (3) ASA + synthetic IIbIIIa antagonist to assess the aggregation response to activation with an agonist (ADP, collagen, thrombin receptor activating peptide-6 [TRAP-6], and arachidonic acid). Via aggregometry, cytochalasin D more weakly inhibited platelet aggregation than simultaneous administration of the -IIbIIIa receptor antagonist with ASA. However, total platelet aggregation inhibition was observed after simultaneous administration of cytochalasin D combined with a synthetic IIbIIIa receptor antagonist. In the thromboelastometry, a significant decrease of the A10, A20 and MCF parameters were observed in the EXTEM/FIBTEM tests after they were modified by the addition of a synthetic IIbIIIa receptor antagonist alone or in combination with ASA. In conclusion, in this Multiplate- and ROTEM-based laboratory approach, a two-way blockade (IIbIIIa-antagonist + cytochalasine D) was sufficient to completely inhibit procoagulant platelet function as observed by aggregometry and thromboelastometry.

Current Limitations of the Assessment of Haemostasis in Adult Extracorporeal Membrane Oxygenation Patients and the Role of Point-of-Care Testing

Haemostatic perturbations are commonly seen in extracorporeal membrane oxygenation (ECMO) patients and remain a clinical challenge, contributing significantly to morbidity and mortality. The approach to anticoagulation monitoring and the management of bleeding varies considerably across ECMO centres. Routine laboratory tests have their limitations in terms of turnaround time and specificity of information provided. Newer point-of-care testing (POCT) for coagulation may overcome these issues, as it provides information about the entire coagulation pathway from clot initiation to lysis. It is also possible to obtain qualitative information on platelet function from these tests. Furthermore, the ability to incorporate these results into a goal-directed algorithm to manage bleeding with targeted transfusion strategies appears particularly attractive and cost effective. Further studies are required to evaluate the utility of POCT to optimise bleeding and anticoagulation management in these complex patients.

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.

Protocol guided bleeding management improves cardiac surgery patient outcomes

BACKGROUND AND OBJECTIVES

Excessive bleeding is a risk associated with cardiac surgery. Treatment invariably requires transfusion of blood products; however, the transfusion itself may contribute to postoperative sequelae. Our objective was to analyse a quality initiative designed to provide an evidenced-based approach to bleeding management.

MATERIALS AND METHODS

A retrospective analysis compared blood product transfusion and patient outcomes 15 months before and after implementation of a bleeding management protocol. The protocol incorporated point-of-care coagulation testing (POCCT) with ROTEM and Multiplate to diagnose the cause of bleeding and monitor treatment.

RESULTS

Use of the protocol led to decreases in the incidence of transfusion of PRBCs (47·3% vs. 32·4%; P < 0·0001), FFP (26·9% vs. 7·3%; P < 0·0001) and platelets (36·1% vs. 13·5%; P < 0·0001). During the intra-operative period, the percentage of patients receiving cryoprecipitate increased (2·7% vs. 5·1%; P = 0·002), as did the number of units transfused (248 vs. 692; P < 0·0001). The proportion of patients who received tranexamic acid increased (13·7% to 68·2%; P < 0·0001). There were reductions in re-exploration for bleeding (5·6% vs. 3·4; P = 0·01), superficial chest wound (3·3% vs. 1·4%; P = 0·002), leg wound infection (4·6% vs. 2·0%; P < 0·0001) and a 12% reduction in mean length of stay from operation to discharge (95%: 9-16%, P < 0·0001). Acquisition cost of blood products decreased by $1 029 118 in the 15-month period with the protocol.

CONCLUSIONS

The implementation of a bleeding management protocol supported by POCCT in a cardiac surgery programme was associated with significant reductions in the transfusion of allogeneic blood products, improved outcomes and reduced cost.

Preoperative Thromboelastometry as a Predictor of Transfusion Requirements during Adult Living Donor Liver Transplantation

BACKGROUND

The ability to predict transfusion requirements may improve perioperative bleeding management as an integral part of a patient blood management program. Therefore, the aim of our study was to evaluate preoperative thromboelastometry as a predictor of transfusion requirements for adult living donor liver transplant recipients.

METHODS

The correlation between preoperative thromboelastometry variables in 100 adult living donor liver transplant recipients and intraoperative blood transfusion requirements was examined by univariate and multivariate linear regression analysis. Thresholds of thromboelastometric parameters for prediction of packed red blood cells (PRBCs), fresh frozen plasma (FFP), platelets, and cryoprecipitate transfusion requirements were determined with receiver operating characteristics analysis. The attending anesthetists were blinded to the preoperative thromboelastometric analysis. However, a thromboelastometry-guided transfusion algorithm with predefined trigger values was used intraoperatively. The transfusion triggers in this algorithm did not change during the study period.

RESULTS

Univariate analysis confirmed significant correlations between PRBCs, FFP, platelets or cryoprecipitate transfusion requirements and most thromboelastometric variables. Backward stepwise logistic regression indicated that EXTEM coagulation time (CT), maximum clot firmness (MCF) and INTEM CT, clot formation time (CFT) and MCF are independent predictors for PRBC transfusion. EXTEM CT, CFT and FIBTEM MCF are independent predictors for FFP transfusion. Only EXTEM and INTEM MCF were independent predictors of platelet transfusion. EXTEM CFT and MCF, INTEM CT, CFT and MCF as well as FIBTEM MCF are independent predictors for cryoprecipitate transfusion. Thromboelastometry-based regression equation accounted for 63% of PRBC, 83% of FFP, 61% of cryoprecipitate, and 44% of platelet transfusion requirements.

CONCLUSION

Preoperative thromboelastometric analysis is helpful to predict transfusion requirements in adult living donor liver transplant recipients. This may allow for better preparation and less cross-matching prior to surgery. The findings of our study need to be re-validated in a second prospective patient population.

Coagulation testing in the perioperative period

Perioperative coagulation management is a complex task that has a significant impact on the perioperative journey of patients. Anaesthesia providers play a critical role in the decision-making on transfusion and/or haemostatic therapy in the surgical setting. Various tests are available in identifying coagulation abnormalities in the perioperative period. While the rapidly available bedside haemoglobin measurements can guide the transfusion of red blood cells, blood product administration is guided by many in vivo and in vitro tests. The introduction of newer anticoagulant medications and the implementation of the modified in vivo coagulation cascade have given a new dimension to the field of perioperative transfusion medicine. A proper understanding of the application and interpretation of the coagulation tests is vital for a good perioperative outcome.

Effect of thromboelastography (TEG®) and rotational thromboelastometry (ROTEM®) on diagnosis of coagulopathy, transfusion guidance and mortality in trauma: descriptive systematic review

Introduction

The understanding of coagulopathies in trauma has increased interest in thromboelastography (TEG®) and thromboelastometry (ROTEM®), which promptly evaluate the entire clotting process and may guide blood product therapy. Our objective was to review the evidence for their role in diagnosing early coagulopathies, guiding blood transfusion, and reducing mortality in injured patients.

Methods

We considered observational studies and randomized controlled trials (MEDLINE, EMBASE, and Cochrane databases) to February 2014 that examined TEG®/ROTEM® in adult trauma patients. We extracted data on demographics, diagnosis of early coagulopathies, blood transfusion, and mortality. We assessed methodologic quality by using the Newcastle-Ottawa scale (NOS) for observational studies and QUADAS-2 tool for diagnostic accuracy studies.

Results

Fifty-five studies (12,489 patients) met inclusion criteria, including 38 prospective cohort studies, 15 retrospective cohort studies, two before-after studies, and no randomized trials. Methodologic quality was moderate (mean NOS score, 6.07; standard deviation, 0.49). With QUADAS-2, only three of 47 studies (6.4%) had a low risk of bias in all domains (patient selection, index test, reference standard and flow and timing); 37 of 47 studies (78.8%) had low concerns regarding applicability. Studies investigated TEG®/ROTEM® for diagnosis of early coagulopathies (n = 40) or for associations with blood-product transfusion (n = 25) or mortality (n = 24). Most (n = 52) were single-center studies. Techniques examined included rapid TEG® (n =12), ROTEM® (n = 18), TEG® (n = 23), or both TEG® and rapid TEG® (n = 2). Many TEG®/ROTEM® measurements were associated with early coagulopathies, including some (hypercoagulability, hyperfibrinolysis, platelet dysfunction) not assessed by routine screening coagulation tests. Standard measures of diagnostic accuracy were inconsistently reported. Many abnormalities predicted the need for massive transfusion and death, but predictive performance was not consistently superior to routine tests. One observational study suggested that a ROTEM®-based transfusion algorithm reduced blood-product transfusion, but TEG®/ROTEM®-based resuscitation was not associated with lower mortality in most studies.

Conclusions

Limited evidence from observational data suggest that TEG®/ROTEM® tests diagnose early trauma coagulopathy and may predict blood-product transfusion and mortality in trauma. Effects on blood-product transfusion, mortality, and other patient-important outcomes remain unproven in randomized trials.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0518-9) contains supplementary material, which is available to authorized users.

Impact of -455G/A Polymorphism of the β-Fibrinogen Gene on Platelet Aggregation in Patients With Acute Coronary Syndrome

We aimed to investigate the association of aspirin and/or clopidogrel low response with −455G/A polymorphism of β-fibrinogen in patients with acute coronary syndrome (ACS). We enrolled 114 consecutive patients (mean age 61 ± 7, 31 female [27.2%], 83 male [72.8%]) with a first ACS. The diagnostic criteria for ACS were based on current guidelines. The -455 G/A β-fibrinogen polymorphism genotype distribution in the patient group was determined as the following: 54.4% GG homozygote, 39.5% GA, and 6.1% AA homozygote. Clopidogrel low response was present in 25 (21.9%) patients, aspirin low response in 21 (18.4%) patients, and dual antiplatelet low response in 9 (7.9%) patients. In our study, no difference was observed in terms of the distribution of -455 G/A β-fibrinogen polymorphism between the groups with and without aspirin and/or clopidogrel or dual antiplatelet low response in the patient group who underwent aspirin and clopidogrel treatment for ACS ( P > .05).

Point of care perioperative coagulation management in liver transplantation and complete portal vein thrombosis

Liver transplantation (LT) is a serious hemostatic challenge in patients with portal vein thrombosis (PVT). Advances in monitoring systems have improved surgery in this setting. We report the successful application of a point-of-care (POC) rotational viscoelastic thromboelastometry-guided (TEM) testing system (ROTEM) which allowed management of coagulation during LT in a 64-year-old cirrhotic patient with a model for end-stage liver disease (MELD) score of 16. Perioperatively, the patient showed complete PVT, hepatomegaly, splenomegaly, recanalization of the umbilical vein, and portosystemic shunt. Macroscopic liver and spleen adherences with collateral circulation were evident. Coagulation factors and fibrinolysis were assessed preoperatively and at graft reperfusion to evaluate the need of hemostatic therapy. Based on ROTEM findings, the patient received 16 g of human fibrinogen concentrate, half preoperatively (with prothrombin complex concentrate 2000 IU, tranexamic acid 1 g, and platelets 2 IU), and two doses of 4 g before and after graft reperfusion; we achieved normalization of all monitored parameters. No ischemia-reperfusion syndrome was present. Postoperatively portal vein flux at Color-Doppler ultrasonography was normal. After a 3-day ICU stay, the patient was moved to the Department of Surgery and discharged on day 14. The postoperative course was uneventful and did not require any further haemostatic therapy.

Management of hemorrhage in cardiothoracic surgery

Bleeding is an important issue in cardiothoracic surgery, and about 20% of all blood products are transfused in this clinical setting worldwide. Transfusion practices, however, are highly variable among different hospitals and more than 25% of allogeneic blood transfusions have been considered inappropriate. Furthermore, both bleeding and allogeneic blood transfusion are associated with increased morbidity, mortality, and hospital costs. In the past decades, several attempts have been made to find a universal hemostatic agent to ensure hemostasis during and after cardiothoracic surgery. Most drugs studied in this context have either failed to reduce bleeding and transfusion requirements or were associated with severe adverse events, such as acute renal failure or thrombotic/thromboembolic events and, in some cases, increased mortality. Therefore, an individualized goal-directed hemostatic therapy ("theranostic" approach) seems to be more appropriate to stop bleeding in this complex clinical setting. The use of point-of-care (POC) transfusion and coagulation management algorithms guided by viscoelastic tests such as thromboelastometry/thromboelastography in combination with POC platelet function tests such as whole blood impedance aggregometry, and based on first-line therapy with fibrinogen and prothrombin complex concentrate have been associated with reduced allogeneic blood transfusion requirements, reduced incidence of thrombotic/thromboembolic and transfusion-related adverse events, and improved outcomes in cardiac surgery. This article reviews the current literature dealing with the management of hemorrhage in cardiothoracic surgery based on POC diagnostics and with specific coagulation factor concentrates and its impact on transfusion requirements and patients' outcomes.

Potential value of transfusion protocols in cardiac surgery

PURPOSE OF REVIEW

On the one hand, cardiac and aortic surgery is associated with a high rate of allogeneic blood transfusion. On the other hand, both bleeding and allogeneic blood transfusion is associated with increased morbidity, mortality, and hospital costs in cardiac and aortic surgery. This article reviews the current literature between 1995 and 2012 dealing with transfusion protocols in cardiovascular surgery. The 16 studies fitting these search criteria have evaluated the impact of the implementation of ROTEM/TEG based coagulation management algorithms on transfusion requirement and outcome in overall 8507 cardiovascular surgical patients.

RECENT FINDINGS

The use of point-of-care (POC) transfusion and coagulation management algorithms based on viscoelastic tests such as thromboelastometry (ROTEM) and thrombelastography (TEG) in combination with POC platelet function tests such as whole blood impedance aggregometry (Multiplate) have been shown to be associated with reduced allogeneic blood transfusion requirements, reduced incidence of thrombotic/thromboembolic and transfusion-related adverse events, and improved outcomes in cardiac surgery.

SUMMARY

Implementation of POC algorithms including a comprehensive bundle of POC diagnostics (thromboelastometry and whole blood impedance aggregometry) in combination with first-line therapy using immediately available specific coagulation factor concentrates (fibrinogen and prothrombin complex concentrate) and defining strict indications, calculated dosages, and clear sequences for each haemostatic intervention seems to be complex but most effective in reducing perioperative transfusion requirements and has been shown to be associated with a decreased incidence of thrombotic/thromboembolic events, transfusion-related adverse events, as well as with improved patients' outcomes including 6-month mortality.

[Randomised comparative study of early versus delayed surgery in hip-fracture patients on concomitant treatment with antiplatelet drugs. Determination of platelet aggregation, perioperative bleeding and a review of annual mortality]

OBJECTIVE

A review of the perioperative management of patients with hip fractures and concomitant therapy with antiplatelet agents, and to analyse the differences in mortality and perioperative bleeding in early surgery (<48 h) versus delayed surgery (>5 days). Platelet aggregation was measured on admission and immediately before surgery in all patients included in the study

PATIENTS AND METHODS

A total of 175 patients over 65 years old, with low energy hip fracture were randomised into 3 groups: Patients on antiplatelet therapy undergoing early surgery, patients on antiplatelet therapy undergoing delayed surgery, and patients not on antiplatelet therapy undergoing early surgery. The same clinical and laboratory data were collected prospectively up to 12 months for all the patients. The platelet aggregation was determined by a semi-quantitative computerised system based on impedance aggregometry in whole blood.

RESULTS

Bleeding, transfusion requirements and analytical results showed no significant differences between groups. More than half (59.8%) of the patients not taking antiplatelet therapy had normal platelet aggregation on admission, while 13.5% of those taking antiplatelet agents did not. Multivariate analysis showed increased mortality at 12 months for the variables, low Barthel index before hip fracture (OR: 0.9-0.9) and number of transfusions (OR: 1.1-1.5). The average lenth of stay was 4.1 days greater in the delayed surgery group.

CONCLUSION

Early surgery for patients receiving antiplatelet therapy has similar clinical outcomes to the delayed, but improves hospital efficiency by reducing the average length of stay. The antiplatelet drug reported by the patient showed low concordance with the determination of the platelet aggregation.

Early thromboelastometric variables reliably predict maximum clot firmness in patients undergoing cardiac surgery: a step towards earlier decision making

BACKGROUND

While much effort has been spent on guiding coagulation and transfusion therapy in patients undergoing cardiopulmonary bypass (CPB) surgery, the use of conventional laboratory-based coagulation tests is hampered by long turnaround times and interference with heparin and protamine. To allow faster assessment of maximum clot firmness (MCF) by point-of-care thromboelastometry (ROTEM®, TEM International GmbH, Munich, Germany), we tested whether clotting time (CT), clot formation time (CFT), or early values of clot firmness (CF) predict MCF.

METHODS

Results of 437 ROTEM® assays (EXTEM®, INTEM®, FIBTEM®, and HEPTEM®) from 84 patients undergoing CPB surgery were analyzed. Measurements were performed prior to and after heparin administration, as well as after protamine administration and CT, CFT, and CF after 5, 10, and 15 min (A5, A10, and A15) after initial clotting (CT) were related to MCF.

STATISTICS

Regression and Bland-Altman analyses and receiver-operating characteristics (ROCs).

RESULTS

CFT (r = 0.87-0.95), A5 (r = 0.84-0.98; P < 0.0001), A10 (r = 0.86-0.98; P < 0.0001), and A15 (r = 0.86-0.98; P < 0.0001) demonstrated high correlation coefficients with MCF, whereas CT correlated weakly (r = 0.07-0.41). As expected, correlation coefficients increased with the time allowed to assess a specific variable. ROC analyses demonstrated excellent accuracy for CFT, A5, A10, and A15 [area under the curve (AUC): 0.9476-0.9931] to predict a subnormal MCF, whereas CT demonstrated poor accuracy (AUC: 0.5796-0.6774).

CONCLUSION

Taking into account specific bias, early values of CF (A5-A15) reliably predict maximum CF under all conditions and, therefore, allow for marked time savings in the interpretation of ROTEM® measurements. This may guide earlier and more specific treatment of CPB-related coagulation disorders.

Recombinant tissue-type plasminogen activator-evoked hyperfibrinolysis is enhanced by acidosis and inhibited by hypothermia but still can be blocked by tranexamic acid

BACKGROUND

Hypothermia and acidosis have been suggested as key initiators of trauma-induced coagulopathy, and severe bleeding caused by hyperfibrinolysis (HF) predicts mortality. We tested in vitro (1) whether clinically relevant grades of hypothermia, acidosis, and their combination impact on recombinant tissue-type plasminogen activator (r-tPA)-evoked HF and assessed (2) the efficacy of tranexamic acid (TA) in inhibiting fibrinolysis under such conditions.

METHODS

To assess the effects of r-tPA-evoked HF, venous blood (3,000 μL) from healthy volunteers was incubated with r-tPA (final concentration, 100 ng/mL) or saline (control) for 30 minutes at the final measurement temperature. Before thromboelastometric measurements, samples were acidified (addition of 40 μL of 0.5 or 1N hydrochloric acid, respectively) to achieve a pH (alpha-stat) of approximately 7.1 or 6.9, respectively. To assess effects of hypothermia, tests were performed at blood/thromboelastometer temperatures of 33°C and 37°C, respectively. Coagulation was analyzed using rotational thromboelastometry (ROTEM), particularly assessing the Clot Lysis Index (CLI) after 45 minutes (CLI45) in extrinsically activated assays (EXTEM).

RESULTS

Addition of r-tPA evoked fibrinolysis (CLI45: median, 64; 25th/75th percentile, 48/80) compared with saline controls (CLI45: median, 93; 25th/75th percentile, 91/96). Moderate acidosis (pH [mean ± SD], 7.12 ± 0.03) did not affect r-tPA-induced fibrinolysis. However, severe acidosis (pH, 6.91 ± 0.02) significantly aggravated r-tPA-induced fibrinolysis (CLI45: median, 49; 25th/75th percentile, 26/71; p = 0.0039) compared with fibrinolysis with normal pH and normothermia (median, 77; 25th/75th percentile, 65.5/83). In contrast, hypothermia (33°C) at normal pH (median ± SD, 7.37 ± 0.02) markedly mitigated fibrinolysis (CLI45: median, 94; 25th/75th percentile, 88/96; p = 0.0156) compared with normothermia (CLI45: median, 64; 25th/75th percentile, 48/80). TA (final concentration, 0.33 mg/mL) abolished r-tPA-evoked fibrinolysis even during severe acidosis (CLI45: median, 92; 25th/75th percentile, 86.5/94; p = 0.0039).

CONCLUSION

Severe acidosis significantly increases r-tPA-evoked fibrinolysis, whereas hypothermia markedly mitigates HF. The latter finding may imply that rapid rewarming of trauma patients might aggravate fibrinolysis. TA reliably abolished fibrinolysis also under these conditions, supporting its role in trauma-induced coagulopathy.

Discrepant fibrinolytic response in plasma and whole blood during experimental endotoxemia in healthy volunteers

Background

Sepsis induces early activation of coagulation and fibrinolysis followed by late fibrinolytic shutdown and progressive endothelial damage. The aim of the present study was to investigate and compare the functional hemostatic response in whole blood and plasma during experimental human endotoxemia by the platelet function analyzer, Multiplate and by standard and modified thrombelastography (TEG).

Methods

Prospective physiologic study of nine healthy male volunteers undergoing endotoxemia by means of a 4-hour infusion of E. coli lipopolysaccharide (LPS, 0.5 ng/kg/hour), with blood sampled at baseline and at 4 h and 6 h. Physiological and standard biochemical data and coagulation tests, TEG (whole blood: TEG, heparinase-TEG, Functional Fibrinogen; plasma: TEG±tissue-type plasminogen activator (tPA)) and Multiplate (TRAPtest, ADPtest, ASPItest, COLtest) were recorded. Mixed models with Tukey post hoc tests and correlations were applied.

Results

Endotoxemia induced acute SIRS with increased HR, temperature, WBC, CRP and procalcitonin and decreased blood pressure. It also induced a hemostatic response with platelet consumption and reduced APTT while INR increased (all p<0.05). Platelet aggregation decreased (all tests, p<0.05), whereas TEG whole blood clot firmness increased (G, p = 0.05). Furthermore, during endotoxemia (4 h), whole blood fibrinolysis increased (clot lysis time (CLT), p<0.001) and Functional Fibrinogen clot strength decreased (p = 0.049). After endotoxemia (6 h), whole blood fibrinolysis was reduced (CLT, p<0.05). In contrast to findings in whole blood, the plasma fibrin clot became progressively more resistant towards tPA-induced fibrinolysis at both 4 h and 6 h (p<0.001).

Conclusions

Endotoxemia induced a hemostatic response with reduced primary but enhanced secondary hemostasis, enhanced early fibrinolysis and fibrinogen consumption followed by downregulation of fibrinolysis, with a discrepant fibrinolytic response in plasma and whole blood. The finding that blood cells are critically involved in the vasculo-fibrinolytic response to acute inflammation is important given that disturbances in the vascular system contribute significantly to morbidity and mortality in critically ill patients.

Hypertension as a Risk Factor for Aspirin and Clopidogrel Resistance in Patients With Stable Coronary Artery Disease

Background:

Platelets play an important role in the pathogenesis of coronary artery disease (CAD). The importance of dual antiplatelet therapy to prevent recurrent ischemic events in patients who have acute coronary syndrome and who will undergo percutaneous coronary intervention (PCI) is well known and widely accepted as a gold standard. However, despite this apparently effective therapy, incidence of adverse ischemic events could not be decreased enough. Resistance to aspirin/clopidogrel is an important risk factor for adverse ischemic clinical events. Up-to-date studies revealed many risk factors for antiplatelet resistance, one of which is hypertension (HT). Currently, there is no sufficient number of studies evaluating the association between HT and antiplatelet resistance, which is the aim of this study.

Methods:

We enrolled 145 consecutive patients (19 female [13.1%], 126 male [86.9%], mean age 55 ± 10) with stable CAD receiving regular antiplatelet therapy composed of 100 mg/d aspirin and 75 mg/d clopidogrel. All patients had been implanted nondrug-eluting coronary stent and/or stents at least 1 month ago. The HT was diagnosed by 24-hour blood pressure (BP) monitoring. Clopidogrel and aspirin resistance was measured by impedance aggregometry method.

Results:

We included 49 patients with HT and 96 nonhypertensive patients with stable CAD. Aspirin resistance was detected in 22 (16.4%) of 134 patients who received aspirin. Clopidogrel resistance was detected in 55 (37.9%) of 145 patients who received clopidogrel. Prevalance of aspirin and clopidogrel resistance was significantly higher in the hypertensive group than in the nonhypertensive group ( P = .030 and P = .007, respectively). Correlation analysis revealed weak but significantly positive correlation between clopidogrel resistance and serum uric acid levels, mean platelet volume, platelet count, and 24-hour mean systolic BP ( r = −.180, P = .030; r = .189, P = .016; r = .226, P = .006; and r = .200, P = .016, respectively).

Conclusion:

We demonstrated higher incidence of antiplatelet resistance in patients with HT. Upon this finding, which is emerged from an actual group of patients with HT, cardioprotective effect of antiplatelet therapy in patients with HT should be argued.

Coagulation management in patients undergoing mechanical circulatory support

The incidence of bleeding and thrombo-embolic complications in patients undergoing mechanical circulatory support therapy remains high and is associated with bad outcomes and increased costs. The need for anticoagulation and anti-platelet therapy varies widely between different pulsatile and non-pulsatile ventricular-assist devices (VADs) and extracorporeal membrane oxygenation (ECMO) systems. Therefore, a unique anticoagulation protocol cannot be recommended. Notably, most thrombo-embolic complications occur despite values of conventional coagulation tests being within the targeted range. This is due to the fact that conventional coagulation tests such as international normalised ratio (INR), activated partial thromboplastin time (aPTT) and platelet count cannot detect hyper- or hypofibrinolysis, hypercoagulability due to tissue factor expression on circulating cells or increased clot firmness, and platelet aggregation as well as response to anti-platelet drugs. By contrast, point-of-care (POC) whole blood viscoelastic tests (thromboelastometry/-graphy) and platelet function tests (impedance or turbidimetric aggregometry) reflect in detail the haemostatic status of patients undergoing mechanical circulatory support therapy and the efficacy of their anticoagulation and antiaggregation therapy. Therefore, monitoring of haemostasis using POC thromboelastometry/-graphy and platelet function analysis is recommended during mechanical circulatory support therapy to reduce the risk of bleeding and thrombo-embolic complications. Notably, these haemostatic tests should be performed repeatedly during mechanical circulatory support therapy since thrombin generation, clot firmness and platelet response may change significantly over time with a high inter- and intra-individual variability. Furthermore, coagulation management can be hampered in non-pulsatile VADs by acquired von Willebrand syndrome, and in general by acquired factor XIII deficiency as well as by heparin-induced thrombocytopenia. In addition, POC testing can be used in bleeding patients to guide calculated goal-directed therapy with allogeneic blood products, haemostatic drugs and coagulation factor concentrates to optimise the haemostasis and to minimise transfusion requirements, transfusion-associated adverse events and to avoid thrombo-embolic complications, as well. However, coagulation management in patients undergoing mechanical circulatory support therapy is somehow like navigating between Scylla and Charybdis, and development of protocols based on POC testing seems to be beneficial.

Ökonomie und Gerinnungsmanagement

<b><i>Hintergrund: </i></b>Bei erworbenen oder chronisch bestehenden Störungen der Gerinnung ist in der perioperativen Phase eine gezielte Therapie von herausragender Bedeutung. Der kostenintensive Einsatz von Blut- und Gerinnungspräparaten und die Beeinflussung des Patientenoutcomes werden hinsichtlich des G-DRG(German Diagnosis Related Groups)-Systems und der Anwendung von Point-of-Care-Geräten bewertet. <b><i>Methode: </i></b>Anhand einer Literaturübersicht und eigener Daten wird der aktuelle Sachstand analysiert und diskutiert. <b><i>Ergebnisse: </i></b>Die perioperative Behandlung von Störungen der Gerinnung ist komplex. Neben der klassischen Labordiagnostik unterstützen und beschleunigen Point-of-Care-Geräte die Therapieentscheidungen. Die Anwendung eines Algorithmus-basierten Applikationsregimes von Blut- und Gerinnungspräparaten optimiert die Verbrauchsmengen und verbessert das Patientenoutcome. Demgegenüber können durch das G-DRG-System bedingte finanzielle Effekte aufgrund von kosten- und erlösseitigen Änderungen für das Krankenhaus negativ ausfallen. Fallpauschalen und Zusatzentgelte decken vor allem bei komplexen Behandlungsfällen wie der Lebertransplantation nicht die tatsächlichen Aufwendungen. Systemisch finanzielle Anreize zur Therapieentscheidung, die unabhängig von einer medizinischen Indikation sein können, sind vorherrschend. <b><i>Schlussfolgerungen: </i></b>Die Therapie von Gerinnungsstörungen stellt Ärzte, die Krankenhausverwaltungen und das G-DRG-System vor besondere Herausforderungen. Nicht selten besteht eine paradoxe Situation zwischen dem Streben nach einer bestmöglichen Patientenversorgung und einer adäquaten Leistungsvergütung des Krankenhauses. Finanzielle Anreize durch Pauschalen und Zusatzentgelte mit Mengenschwellen, die Therapieentscheidungen beeinflussen können, sind zukünftig zu eliminieren.

Fast interpretation of thromboelastometry in non-cardiac surgery: reliability in patients with hypo-, normo-, and hypercoagulability

BACKGROUND

Conventional coagulation test are not useful to guide haemostatic therapy in severe bleeding due to their long turn-around time. In contrast, early variables assessed by point-of-care thromboelastometry (ROTEM(®)) are available within 10-20 min and increasingly used to guide haemostatic therapy in liver transplantation and severe trauma. However, the reliability of early ROTEM(®) variables to predict maximum clot firmness (MCF) in non-cardiac surgery patients with subnormal, normal, and supranormal MCF has not yet been evaluated.

METHODS

Retrospective data of 14,162 ROTEM(®) assays (3939 EXTEM(®), 3654 INTEM(®), 3287 FIBTEM(®), and 3282 APTEM(®) assays) of patients undergoing non-cardiac surgery were analysed. ROTEM(®) variables [clotting time (CT), clot formation time (CFT), α-angle, A5, A10, and A15] were related to MCF by linear or non-linear regression, as appropriate. The Bland-Altman analyses to assess the bias between early ROTEM(®) variables and MCF and receiver operating characteristics (ROC) were also performed.

RESULTS

Taking the best and worst correlation coefficients for each assay type, CT (r=0.18-0.49) showed the worst correlation to MCF. In contrast, α-angle (r=0.85-0.88) and CFT (r=0.89-0.92) demonstrated good but non-linear correlation with MCF. The best and linear correlations were found for A5 (r=0.93-0.95), A10 (r=0.96), and A15 (r=0.97-0.98). ROC analyses provided excellent area under the curve (AUC) values for A5, A10, and A15 (AUC=0.962-0.985).

CONCLUSIONS

Early values of clot firmness allow for fast and reliable prediction of ROTEM(®) MCF in non-cardiac patients with subnormal, normal, and supranormal MCF values and therefore can be used to guide haemostatic therapy in severe bleeding.

Reference intervals for platelet aggregation assessed by multiple electrode platelet aggregometry

INTRODUCTION

Analyses of platelet aggregation in hirudin whole blood using Multiplate® was validated. Reference intervals for the most commonly used agonists were established, and the association between platelet aggregation, age, gender and haematological values was analysed.

MATERIAL AND METHODS

We included 121 healthy individuals to establish reference intervals and six healthy individuals for evaluation of the day-to-day variation. Platelet aggregation was evaluated on hirudin whole blood employing Multiplate® induced by arachidonic acid, ADP, collagen and ristocetin (RISTOlow and RISTOhigh). Measurements of haematological values were performed employing Sysmex K-4500.

RESULTS

We found no association between platelet aggregation and age (p>0.57 for all agonists, except RISTOlow: p=0.05). Platelet aggregation was significantly higher in women compared to men for all agonists (p<0.0003), except RISTOlow (p=0.05). A reference interval is presented as 95% confidence interval suitable for any age and both sex. Day-to-day variation was <11% for all agonists except for RISTOlow. No association was found between platelet aggregation and haematocrit or red blood cell count after adjusting for age and gender except for RISTOhigh. A positive significant association was found between platelet count and platelet aggregation (p<0.04). Finally, a significant positive association was found between platelet aggregation and white blood cell count for all agonists (p<0.05) except RISTOlow and RISTOhigh (p>0.05).

CONCLUSION

Reference intervals for platelet aggregation in healthy individuals (age: 17 to 66 years) were established in hirudin whole blood measured by Multiplate® employing the most commonly used agonists.

Hemostatic function of buffy coat platelets in additive solution treated with pathogen reduction technology

BACKGROUND

Pathogen reduction technologies (PRTs) may influence the hemostatic potential of stored platelet (PLT) concentrates. To investigate this, buffy coat PLTs (BCPs) stored in PLT additive solution (SSP+) with or without Mirasol PRT treatment (CaridianBCT Biotechnologies) were compared by functional hemostatic assays.

STUDY DESIGN AND METHODS

We performed in vitro comparison of PRT (PRT-BCP) and control pooled-and-split BCPs (CON-BCP) after 2, 3, 6, 7, and 8 days' storage. Hemostatic function was evaluated with thrombelastography (TEG) and impedance aggregometry (Multiplate), the latter also in a sample matrix (Day 2) with or without addition of red blood cells (RBCs), control plasma, and/or PRT-treated plasma.

RESULTS

PRT treatment of 8-day-stored BCPs influenced clot formation (TEG) minimally, with reductions in maximum clot strength (maximum amplitude, p = 0.014) but unchanged initial fibrin formation (R), clot growth rate (α), and fibrinolysis resistance. In the absence of RBCs and plasma, PRT impaired aggregation (Multiplate) in stored BCPs, with reduced aggregation against thrombin receptor activating peptide-6 (p < 0.001), collagen (p = 0.014), adenosine 5'-diphosphate (p = 0.007), and arachidonic acid (p = 0.070). Addition of RBCs and PRT-treated or untreated plasma to PRT-BCP and CON-BCP, respectively, enhanced aggregation in both groups.

CONCLUSIONS

Mirasol PRT treatment of BCPs had a minimal influence on clot formation, whereas aggregation in the absence of RBCs and plasma was significantly reduced. Addition of RBCs and plasma increased agonist-induced responses resulting in comparable aggregation between PRT-BCP and CON-BCP. The clinical relevance for PLT function in vivo of these findings will be investigated in a clinical trial.

Impact of platelet count on results obtained from multiple electrode platelet aggregometry (Multiplate)

OBJECTIVES

Use of potent antiplatelet drugs requires evaluation of platelet function. While platelet function in elective cases is usually assessed in a central laboratory environment, there is also an urgent need for rapid perioperative point-of-care assessment. Recently, multiple electrode platelet aggregometry has been developed and assumed to measure platelet function independent from platelet count. We tested the hypothesis that results of multiple electrode platelet aggregometry are affected by platelet count, in particular if platelet count is below normal range.

METHODS

Whole blood samples from 20 healthy volunteers were prepared containing platelet concentrations of 50,000, 100,000, 150,000, 200,000, and 250,000 microl(-1) while maintaining hematocrit. Platelet aggregation was induced by collagen, thrombin receptor activating peptide 6 (TRAP-6), adenosine-diphoshate (ADP), and arachidonic acid, respectively, and aggregation was measured by multiple electrode platelet aggregometry (Multiplate).

RESULTS

Results of multiple electrode platelet aggregometry significantly decreased in blood samples with platelet count below normal range. Compared to results measured in blood samples with platelet count within normal range, aggregometry results decreased by 18.4 % (p<0.001) and 37.2 % (p<0.001) in blood samples with a platelet count of 100.000 and 50.000 microl(-1), respectively. On the other hand, large interindividual variation has been observed and some blood samples showed normal results even with platelet counts of 50.000 microl(-1).

CONCLUSION

The results obtained with Multiplate. Analyzer are influenced by platelet function as well as platelet count thus displaying the overall platelet aggregability within the blood sample rather than platelet function alone.

Point-of-care coagulation testing and transfusion algorithms

Patients with cardiovascular disease have an array of haemostasis disorders that predispose to the development of thrombotic and embolic disease states. These patients are often maintained on anti-thrombotic medication to prevent adverse cardiovascular events. Patients undergoing cardiac surgery also have haemostatic disorders that include their intrinsic disease state, adjunctive medication, and the coagulation disturbances induced by cardiopulmonary bypass. The following review introduces the monitors that are available for monitoring perioperative coagulation, with an emphasis on cardiovascular surgery. Heparin monitors, platelet function monitors for use in transfusion algorithms, and monitoring anti-platelet drugs will be discussed.

Measurement of platelet aggregation in ovine blood using a new impedance aggregometer

BACKGROUND

Whole blood platelet aggregometry (impedance) is an important method to investigate platelet function disorders. Examination of hemostatic function in sheep is important with respect to their role as an animal model of human disease.

OBJECTIVE

The aim of this study was to evaluate and optimize selected methodological aspects (anticoagulant, agonist concentration) of impedance aggregometry in ovine blood using the new Multiplate 5.0 analyzer.

METHODS

Blood samples were collected in hirudin anticoagulant from 40 clinically healthy sheep. Samples from selected sheep were collected in citrate, with or without the addition of calcium chloride. The agonists adenosine diphosphate (ADP), collagen, ristocetin, arachidonic acid, and thrombin receptor-activating peptide (TRAP) were added in several concentrations to induce aggregation.

RESULTS

Based on maximum aggregation values and internal precision, no significant difference was found between ADP concentrations of 3-10 micromol/L and collagen concentrations of 3-5 microg/mL (P>.05). The lowest interindividual variation of approximately 3-4-fold was seen with 4 and 5 micromol/L ADP and 4 and 5 microg/mL collagen. Ristocetin, arachidonic acid, and TRAP did not induce significant aggregation at any concentration. Aggregation results were significantly lower when measured in citrate- vs hirudin-anticoagulated blood, regardless of the presence of calcium chloride.

CONCLUSIONS

Our results indicate that the multiplate impedance aggregometer is suitable for the measurement of platelet aggregation in sheep using optimal agonist concentrations of 4-5 micromol/L ADP and 4-5 microg/mL collagen. Hirudin-anticoagulated blood is the preferred sample material.

Measurement of platelet function in dogs using a novel impedance aggregometer

The aim of this study was to optimise the technique and establish reference values for whole blood aggregometry in dogs using a novel multiplate analyser. Measurements were performed on the hirudin-anticoagulated blood of healthy dogs using a wide range of agonists. Optimal agonist concentrations were 10 micromol/L of adenosine diphosphate, 5 microg/mL of collagen and 1 mmol/L of arachidonic acid. Ristocetin (at 0.2 and 1 mg/mL) and thrombin receptor activating peptide (TRAP-6 at 32 and 160 micromol/L) did not consistently induce platelet aggregation. Coefficients of variance for within-run imprecision (n=10 repetitions) varied from 5% to 18%. Measurement signals were significantly higher when analyses were performed on standard samples (hirudin-anticoagulated blood) compared to citrated blood or blood samples anticoagulated with citrate buffer, regardless of whether or not re-calcification was performed (P<0.05). The findings indicate that the analyser is suitable for the investigation of platelet aggregation in dogs and analysis should be performed on hirudin-anticoagulated blood using optimised agonist concentrations.

Assessment of platelet function on whole blood by multiple electrode aggregometry in high-risk patients with coronary artery disease receiving antiplatelet therapy

This study sought to compare Multiplate impedance platelet aggregometry (IPA) with light transmission aggregometry (LTA) and the PFA-100 for determining the prevalence of residual platelet reactivity (RPR) by the Multiplate IPA in 297 patients with acute coronary syndrome receiving dual antiplatelet therapy. Aggregations were induced by adenosine-5 diphosphate (ADP), arachidonic acid, and collagen. PFA-100 closure times were measured by collagen and ADP and epinephrine (CEPI) cartridges. Significant correlations were observed between Multiplate IPA and LTA after all stimulations (P < .0001) and between Multiplate IPA (arachidonate and collagen) and PFA-100 CEPI closure time (P < .0001 for both). Cutoff values of Multiplate IPA (for all stimulations) were calculated for the identification of RPR. Between the Multiplate IPA and LTA good agreement was found with all 3 agonists (P < .0001 for all). Multiplate IPA might represent a reliable, handy, rapid tool to monitor antiplatelet therapy in clinical practice and for clinical investigations.