Perioperative assessment of platelet function by Thromboelastograph Platelet Mapping in cardiovascular patients undergoing non-cardiac surgery

Thromboelastography-Guided Antiplatelet Therapy for Patients with Ischemic Cerebrocardiovascular Diseases: A Systematic Review and Meta-Analysis

INTRODUCTION

The effectiveness of thromboelastography (TEG)-guided antiplatelet therapy in patients with ischemic cerebrocardiovascular diseases is not well-established. This systematic review evaluates the efficacy and safety of TEG-guided antiplatelet therapy compared to standard treatment in patients with ischemic cerebrocardiovascular diseases.

METHODS

Randomized controlled trials (RCTs) and observational studies comparing TEG-guided antiplatelet therapy with standard therapy in patients suffering from ischemic stroke (IS) or coronary artery disease (CAD) were identified. The primary efficacy measure was a composite of ischemic and hemorrhagic events. Secondary efficacy measures included any ischemic events, while safety was assessed by the occurrence of bleeding events.

RESULTS

Ten studies involving 4 RCTs and 6 observational studies with a total of 1,678 patients were included. When considering a composite of ischemic and hemorrhagic events in RCTs, a significant reduction was observed in IS or CAD patients under TEG-guided therapy compared to standard therapy (OR: 0.45, 95% CI: 0.27-0.75, p = 0.002). After pooling RCTs and observational studies together, compared to standard antiplatelet therapy, TEG-guided therapy significantly reduced the risk of a composite of ischemic and hemorrhagic events (OR: 0.26, 95% CI: 0.19-0.37; p < 0.00001), ischemic events (OR: 0.28, 95% CI: 0.19-0.41; p < 0.00001), and bleeding events (OR: 0.31, 95% CI: 0.16-0.62; p = 0.0009) in patients with IS or CAD.

CONCLUSION

TEG-guided antiplatelet therapy appears to be both effective and safe for patients with IS or CAD. These findings support the use of TEG testing to tailor antiplatelet therapy in individuals with ischemic cerebrocardiovascular diseases.

The Role of Viscoelastic Testing in Assessing Hemostasis: A Challenge to Standard Laboratory Assays?

Viscoelastic testing is increasingly being used in clinical and research settings to assess hemostasis. Indeed, there are potential situations in which viscoelastic testing is reportedly superior to standard routine laboratory testing for hemostasis. We report the current testing platforms and terminology, as well as providing a concise narrative review of the published evidence to guide its use in various clinical settings. Notably, there is increasing evidence of the potential utility of viscoelastic testing for assessment of direct oral anticoagulants, and bleeding associated with chronic liver disease, orthotopic liver transplantation, cardiac surgery, trauma, obstetrics and pediatrics.

The role of viscoelastic testing in assessing peri-interventional platelet function and coagulation

We carried out a literature search in MEDLINE (PubMed) and EMBASE literature databases to provide a concise review of the role of viscoelastic testing in assessing peri-interventional platelet function and coagulation. The search identified 130 articles that were relevant for the review, covering the basic science of VHA and VHA in clinical settings including cardiac surgery, cardiology, neurology, trauma, non-cardiac surgery, obstetrics, liver disease, and COVID-19. Evidence from these articles is used to describe the important role of VHAs and platelet function testing in various peri-interventional setups. VHAs can help us to comprehensively assess the contribution of platelets and coagulation dynamics to clotting at the site-of-care much faster than standard laboratory measures. In addition to standard coagulation tests, VHAs are beneficial in reducing allogeneic transfusion requirements and bleeding, in predicting ischemic events, and improving outcomes in several peri-interventional care settings. Further focused studies are needed to confirm their utility in the peri-interventional case.

Viscoelastic Hemostatic Assays and Platelet Function Testing in Patients with Atherosclerotic Vascular Diseases

Platelets play crucial role in acute vascular atherosclerotic diseases, including myocardial infarction and stroke. Additionally, platelet aggregation is a key target of antiplatelet agents, forming the keystone of pharmacotherapy of various atherosclerotic cardiovascular diseases. Thromboelastography and thromboelastometry, representing currently available viscoelastic hemostatic assays (VHA), are designed as whole blood, real-time analyzers of clot formation and clot resolution. These assays could, in theory, overcome some limitations of currently available platelet function testing assays. This article reviews the current experience with the use of VHA for platelet function testing and for monitoring of the response to antiplatelet therapy.

Effect of ticagrelor versus clopidogrel on platelet reactivity measured by thrombelastography in patients with minor stroke or TIA

In this study, we tested the effect of ticagrelor versus clopidogrel on platelet reactivity in patients with minor stroke or transient ischemic attack (TIA). A pre-specified subgroup analysis of a randomized controlled trial was conducted. Platelet reactivity was assessed by thrombelastography (TEG) platelet mapping. Patients were divided into carriers and non-carriers according to the carrier status of CYP2C19 loss-of-function (LOF) alleles. The primary outcome was the proportion of patients with high on-treatment platelet reactivity (HOPR) (defined as maximum amplitude induced by adenosine diphosphate > 47mm) at 90±7 days. Clinical outcomes within 90±7 days were followed up. Among 339 patients, 170 were randomized to ticagrelor/aspirin and 169 to clopidogrel/aspirin. Compared with clopidogrel/aspirin, the proportion of HOPR at 90±7 days in ticagrelor/aspirin was significantly lower (12.2% versus 30.0%, P < 0.001). Ticagrelor/aspirin had a lower proportion of HOPR among carriers (11.0% versus 35.6%, P < 0.001), but not among non-carriers (13.5% versus 22.4%, P = 0.17). Ticagrelor was superior to clopidogrel in inhibiting platelet reactivity measured by TEG platelet mapping among patients with acute minor stroke or TIA, particularly in carriers of the CYP2C19 LOF alleles. Large randomised controlled trials are needed to confirm our findings.

Viscoelastic testing in cardiac surgery

Bleeding complications are common in cardiac surgery and lead to an increase in morbidity and mortality. This is multifactorial in aetiology including the effects of cardiopulmonary bypass, the drugs given to manipulate the coagulation system and the vascular nature of the surgery itself. Viscoelastic tests provide a point of care, rapid assessment of coagulation which offer the advantage of faster turnaround times and a nuanced view of the elements of the coagulation system allowing targeted therapy to be delivered quickly. Both thomboelastography (TEG)and thromboelastometry (ROTEM) have been recommended for use in cardiac surgery, both have shown a reduction in transfusion and bleeding when used as part of a testing algorithm. They are particularly useful in assessing residual heparinisation and fibrinogen levels. Additionally, TEG allows the evaluation of the effects of anti-platelet agents on platelet function. This review discusses the mechanisms by which bleeding occurs in cardiac surgery and explores three uses of viscoelastic testing in cardiac surgery: to predict bleeding, to assess platelet function and peri-operative testing to reduce transfusion.

Body weight, CYP2C19, and P2Y12 receptor polymorphisms relate to clopidogrel resistance in a cohort of Chinese ischemic stroke patients with aspirin intolerance

PURPOSE

Dual antiplatelet therapy (DAT) with clopidogrel and aspirin is not suitable for clopidogrel resistance (CR) patients with aspirin intolerance. To investigate the prevalence of CR in patients with aspirin intolerance after ischemic stroke (IS) and to assess the relationship between CR and CYP2C19, P2Y12 receptor genotypes in patients with aspirin intolerance after IS.

METHODS

We enrolled 126 IS patients with aspirin intolerance from Han Chinese in Shangqiu from January 2016 to November 2018. All IS patients with aspirin intolerance were treated with clopidogrel for 7 days. Adenosine diphosphate-induced platelet inhibition rate was measured by thrombelastography (TEG) mapping assay. The SNPs CYP2C19*2, CYP2C19*3, and P2Y12 receptor (52 G >T) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Binary logistic regression analyses were performed using SPSS version 20.0.

RESULTS

The prevalence of CR in patients with aspirin intolerance after IS was approximately 31.0%. Multivariate regression analysis showed that body weight (OR 1.091 (95% CI 1.031-1.155), p = 0.003), CYP2C19 phenotype intermediate metabolizer (IM) (OR 3.820 (95% CI 1.021-14.288), p = 0.046), and CYP2C19 phenotype poor metabolizer (PM) (OR 14.481 (95% CI 2.791-75.129), p = 0.001) significantly increased the risk of CR and P2Y12 receptors (52 G >T) (OR 3.498 [95% CI 1.251-9.784], p = 0.017) increased the risk of CR.

CONCLUSIONS

The patients with high body weight, the CYP2C19 phenotypes, and P2Y12 receptor (52 G >T) variant alleles are at risk of CR during clopidogrel treatment in Chinese IS patients with aspirin intolerance. The higher body weight and relevant polymorphisms may help to predict CR in Chinese IS patients with aspirin intolerance.

Comparison between thromboelastography and thromboelastometry

Two of the most commonly used viscoelastic hemostatic assays, thromboelastometry (ROTEM) and thrombelastography (TEG), have proven to decrease allogenic blood transfusions with cost reduction and possibly decrease mortality and morbidity in cardiac, trauma, and other bleeding patients. This article compares the two devices to provide guidance on the selection and use of these monitoring systems. Their second-generation assays, TEG 6S and ROTEM Sigma, are also discussed.

Assessment of Thrombelastography and Platelet Life Span in Ovines

Ovines are a common animal model for the study of cardiovascular devices, where consideration of blood biocompatibility is an essential design criterion. In the ovine model, tools to assess blood biocompatibility are limited and continued investigation to identify and apply additional assays is merited. Toward this end, the thrombelastograph, clinically utilized to assess hemostasis, was used to characterize normal ovine parameters. In addition, platelet labeling with biotin was evaluated for its potential applicability to quantify ovine platelet life span. Mean ovine thrombelastograph values were reaction-time: 4.9 min, K-time: 2 min, angle: 64.1°, maximum amplitude: 68.6mm, actual clot strength: 11.9 kd/s, and coagulation index: 1.5. Reaction time was significantly shorter and maximum amplitude, actual clot strength, and coagulation index were all significantly higher when compared to normal human thrombelastograph values suggesting some hypercoagulability of sheep blood. Biotinylation and reinfusion of ovine platelets allowed temporal tracking of the labeled platelet cohort with flow cytometry. These data indicated a mean ovine platelet life span of 188h with a half-life of 84h. The collection of these parameters for normal ovines demonstrates the applicability of these techniques for subsequent studies where cardiovascular devices may be evaluated and provides an indication of normal ovine values for comparison purposes.

Antiplatelet Effect of Ketorolac in Children After Congenital Cardiac Surgery

Background:

Ketorolac is used for pediatric analgesia after surgery despite its known platelet inhibition via the arachidonic acid (AA) pathway. The degree of platelet inhibitory effect after cardiac surgery is not well characterized. Thromboelastography with platelet mapping (TEG-PM) is emerging as a frequently used test to evaluate platelet inhibition via the AA pathway.

Methods:

Post hoc analysis of a data set collected in a prospective observational cohort study evaluating platelet inhibition in children after congenital heart surgery with cardiopulmonary bypass (CPB). Categorization into two groups: (1) received ketorolac and (2) did not receive ketorolac for analgesia after surgery. The TEG-PM was evaluated at two time points (prior to surgery and 12-48 hours after CPB).

Results:

Fifty-three children were studied; mean age was 6.6 (range: 0.07-16.7) years and 45% (n = 24) were female. Participants were distributed into two groups by ketorolac use, 41 within the ketorolac group and 12 in the no ketorolac group. All 41 participants who received ketorolac had platelet inhibition and 11 (91.7%) of 12 participants who did not receive ketorolac had normal platelet function after surgery ( P < .0001). There was no difference in patient characteristics or clinical data between the two groups.

Conclusions:

Ketorolac use in a cohort of children after congenital cardiac surgery was associated with platelet inhibition via the AA pathway when evaluated by TEG-PM.

The safety of triple antiplatelet therapy under thromboelastography guidance in patients undergoing stenting for ischemic cerebrovascular disease

OBJECTIVE

To investigate the safety of triple antiplatelet therapy (TAT) with cilostazol in patients undergoing stenting for extracranial and/or intracranial artery stenosis.

METHODS

A prospectively collected database was reviewed to identify patients who underwent stenting for extracranial and/or intracranial artery stenosis and showed resistance to aspirin and/or clopidogrel as assessed by pre-stenting thromboelastography (TEG) testing. Patients were assigned to a TAT group and a dual antiplatelet therapy (DAT) group. Major complications were defined as thromboembolic events (transient ischemic attack (TIA), ischemic stroke, and stent thrombosis) or major bleeding events within 30 days, and minor complications were defined as extracranial bleeding that did not require vascular surgery or transfusion within 30 days.

RESULTS

A total of 183 patients were identified. The incidence of major complications was significantly lower in the TAT group than in the DAT group (TAT group vs. DAT group, 1/110 vs. 6/73; P=0.017). TIAs occurred in four patients, with one in the TAT group and three in the DAT group (1/110 vs. 3/73; P=0.303). Ischemic strokes occurred in three patients in the DAT group (TAT group vs. DAT group, P=0.062). No major bleeding events or stent thrombosis was recorded in either group. Two patients (one in each group) experienced minor complications that resolved without additional treatment (1/110 vs. 1/73; P>0.999).

CONCLUSIONS

TAT under TEG guidance appears to be a safe antiplatelet strategy in patients undergoing stenting for extracranial and/or intracranial artery stenosis. By employing TAT under TEG guidance, favorable outcomes can be achieved in these patients.

Thromboelastographic assessment of the impact of mexiletine on coagulation abnormalities induced by air or normal saline intravenous injections in conscious rats

BACKGROUND

Thromboelastography (TEG) in venous air embolism (VAE) has been poorly studied. We induced coagulation abnormalities by VAE in a rat model, assessed by TEG with and without mexiletine, a lidocaine analogue local anesthetic.

METHODS

Twenty-three Sprague Dawley rats instrumented under isoflurane anesthesia and allowed to recover five days prior to the experiments were randomized into three experimental groups: 1) VAE (n = 6); 2) VAE and mexiletine (n = 9); and 3) normal saline (NS) alone (control group, n = 8). Blood samples were collected at baseline, one hour (h) and 24 h in all groups and analyzed by TEG to record the R, K, angle α and MA parameters.

RESULTS

In Group 1, VAE decreased significantly R at 1 h (31%), K at 1 h (59%) and 24 h (34%); α increased significantly at 1 h (30%) and 24 h (22%). While R returned to baseline values within 24 h, K, MA and α did not. In group-2 (Mexiletine + VAE), K and R decreased at 1 h (48% and 29%, respectively) and at 24 h the changes were non-significant. Angle α increased at 1 h (28%) and remained increased for 24 h (25%). In group 3 (NS), only R was temporarily affected. MA increased significantly at 24 h only in the VAE alone group.

CONCLUSION

As expected, VAE produced a consistent and significant hypercoagulable response diagnosed/confirmed by TEG. Mexiletine prevented the MA elevation seen with VAE and corrected R and K time at 24 h, whereas angle α remained unchanged. Mexiletine seemed to attenuate the hypercoagulability associated with VAE in this experiment. These results may have potential clinical applications and deserve further investigation.

Platelet Aggregometry Testing: Molecular Mechanisms, Techniques and Clinical Implications

Platelets play a fundamental role in normal hemostasis, while their inherited or acquired dysfunctions are involved in a variety of bleeding disorders or thrombotic events. Several laboratory methodologies or point-of-care testing methods are currently available for clinical and experimental settings. These methods describe different aspects of platelet function based on platelet aggregation, platelet adhesion, the viscoelastic properties during clot formation, the evaluation of thromboxane metabolism or certain flow cytometry techniques. Platelet aggregometry is applied in different clinical settings as monitoring response to antiplatelet therapies, the assessment of perioperative bleeding risk, the diagnosis of inherited bleeding disorders or in transfusion medicine. The rationale for platelet function-driven antiplatelet therapy was based on the result of several studies on patients undergoing percutaneous coronary intervention (PCI), where an association between high platelet reactivity despite P2Y12 inhibition and ischemic events as stent thrombosis or cardiovascular death was found. However, recent large scale randomized, controlled trials have consistently failed to demonstrate a benefit of personalised antiplatelet therapy based on platelet function testing.

Monitoring the hemostasis with rotation thromboelastometry in patients with acute STEMI on dual antiplatelet therapy: First experiences

Rotation thromboelastometry (ROTEM) is a viscoelastometric point-of-care-test for the complex evaluation of changes in hemostasis, performed in whole blood. However, no prospective study evaluating the efficacy of the antiplatelet therapy using ROTEM was performed.Fifty-six patients (34 men, 22 women, mean age 67.75 years, and age range 34-88 years) with acute ST-elevation myocardial infarction (STEMI), treated with dual antiplatelet therapy, undergoing urgent coronary angiography and percutaneous coronary intervention (PCI) of culprit coronary lesion were included. Three blood samples were taken (sample 1 taken before the urgent coronary angiography, sample 2 in 24 hours after the admission, and sample 3 in 30 days after acute STEMI). Twenty-one healthy blood donors (17 men, 4 women, mean age 50.38 years, and age range 40-74 years) were recruited as the control group. Blood samples were tested with ROTEM Gamma (Pentapharm GmbH, Munich, Germany) and light transmission aggregometry (LTA).Clotting time (CT) was significantly prolonged and maximum clot firmness (MCF) was significantly higher in patients compared to controls. Mean platelet aggregation after the induction with arachidonic acid (33.2% vs 74.6% in sample 1 and 21.1% vs 74.6% in sample 2), as well as adenosine diphosphate (51.4% vs 72.7% in sample 1 and 37.1% vs 72.7% in sample 2), were significantly lower in patients with acute STEMI.Significantly prolonged CT and increased MCF was found in patients with acute STEMI. This study confirmed the ability of ROTEM to identify changes in hemostasis in ACS patients on antithrombotic therapy.

The impact of P2Y12 promoter DNA methylation on the recurrence of ischemic events in Chinese patients with ischemic cerebrovascular disease

The primary mechanism of clopidogrel resistance is still unclear. We aimed to investigate whether the methylation status of the P2Y12 promoter has effects on platelet function and clinical ischemic events. Patients with ischemic cerebrovascular disease were enrolled into our study. Venous blood samples were drawn for thrombelastograpy (TEG) and active metabolite assay. Patients were divided into a case- or control-group based on the occurrence of ischemic events during a one year follow-up. Two TEG parameters between the case and control groups were statistically significant [ADP inhibition rate (ADP%): P = 0.018; ADP-induced platelet-fibrin clot strength (MA_ADP): P = 0.030]. The concentrations of clopidogrel active metabolite had no significant difference (P = 0.281). Sixteen CpG dinucleotides on P2Y12 promoter were tested. Three CpG sites (CpG11 and CpG12 + 13) showed lower methylation status, which correlated with a strong association with increased risk of clinical events. Changes of MA_ADP and ADP% were also associated with methylation levels of CpG 11 and CpG 12 + 13. Hypomethylation of the P2Y12 promoter is associated with a higher platelet reactivity and increased risk of ischemic events in our patients. Methylation analysis of peripheral blood samples might be a novel molecular marker to help early identification of patients at high risk for clinical ischemic events.

Platelet function testing in cardiac surgery

Bleeding in cardiac surgery is known to cause increased morbidity and mortality. The rise in the use of anti-platelet medication has led to an increase in the number of patients presenting for cardiac surgery with platelet dysfunction, who are at a heightened risk of bleeding. However, the extent of platelet inhibition is well known to differ among individuals. In the past few years, a number of point-of-care platelet function testing devices, which may be able to assess platelet reactivity, have entered the market. This review will examine the devices most commonly studied and the evidence surrounding their use in cardiac surgery and their effect on blood loss.

Clinically relevant exaggerated pharmacodynamic response to dual antiplatelet therapy detected by Thromboelastogram(®) Platelet Mapping™

Dual antiplatelet therapy (DAPT) is the standard of care for primary and secondary prevention strategies in patients with coronary artery disease after stenting. Current guidelines recommend that DAPT be continued for 12 months in patients after receiving drug eluting stents. Approximately 5% of these patients will present within this 12-month period for noncardiac surgery. This case report describes a clinically relevant exaggerated pharmacodynamic response to DAPT detected by preoperative assessment of platelet function. Based on the clinical history and physical exam and subsequent lab results, a general anesthetic was performed rather than a spinal anesthetic and the surgical procedure was changed. An exaggerated pharmacodynamic response to DAPT poses its own set of risks (unexpected uncontrolled bleeding, epidural hematoma following neuraxial block placement) that point-of-care aggregation testing may decrease or mitigate by altering clinical decision making. If the clinical history and physical exam reveal possible platelet dysfunction in patients receiving DAPT, preoperative platelet function testing should be considered.

Effectiveness of platelet inhibition on major adverse cardiac events in non-cardiac surgery after percutaneous coronary intervention: a prospective cohort study

BACKGROUND

Platelet inhibition is mandatory therapy after percutaneous coronary intervention (PCI). Withdrawal of oral antiplatelet agents has been linked to increased incidence of postoperative adverse cardiac events in post-PCI patients having non-cardiac surgery (NCS). There is limited knowledge of temporal changes in platelet inhibition in this high-risk surgical population. We therefore performed a multicentre prospective cohort study evaluating perioperative platelet function and its association with postoperative major adverse cardiac events (MACE).

METHODS

In 201 post-PCI patients having NCS, we assessed the association between platelet function and postoperative MACE. We performed perioperative platelet function testing using a platelet mapping assay (PMA). Troponin-I was measured every 8 h for 2 days, then daily until day 5. Myocardial infarction was assessed using the third universal definition. We used multivariable logistic regression to assess the association between platelet inhibition and MACE.

RESULTS

Major adverse cardiac events occurred in 40 patients within 30 days of surgery. Thirty-two of these events were non-ST-elevation myocardial infarction, four ST-elevation myocardial infarction, and four exacerbation of congestive heart failure. We were unable to show an association between platelet inhibition and MACE. The PMA showed declining levels of platelet inhibition the longer the antiplatelet therapy was withheld before surgery. Logistic regression did not show an association between preoperative platelet function or the type of stent and MACE. We found an increased cardiac risk of MACE after surgery within 6 weeks of PCI.

CONCLUSIONS

The incidence of MACE in patients undergoing NCS after previous PCI is high in spite of adequate perioperative antiplatelet therapy.

CLINICAL TRIAL REGISTRATION

NCT 01707459 (registered at http://www.clinicaltrials.gov).

Verifying the performance characteristics of the TEG5000 thromboelastogram in the clinical laboratory

OBJECTIVE

To verify the manufacturer performance claims of the TEG5000 with traditional laboratory methods.

MATERIALS AND METHODS

Samples were concurrently measured using the TEG5000 analyzer and either PT, APTT, fibrinogen, factor activities, platelet count, or platelet function testing using whole blood or platelet-rich plasma methods.

RESULTS

Within-run imprecision yielded coefficient of variation (CV) of <5%. There was no correlation of PT or APTT with R time. Only Factor VIII and factor XII activity significantly correlated with R time. There was significant correlation between k and angle with FBG, PLT count, and factor levels. There was weak inverse correlation between angle results and measures of platelet function. All laboratory methods were significantly correlated with MA. There were significant differences between citrated whole blood and fresh citrated plasma for angle and MA, and between fresh and frozen plasma for R time and MA. We demonstrated a high % inhibition noted with normal, drug naïve donors, especially with ADP PLT mapping (50% inhibition), but less so with AA PLT mapping (20% inhibition). For TEG platelet mapping, 19/22 (86.3%) and 17/22 (77.3%) results were concordant with traditional aggregation results.

CONCLUSION

We demonstrated both the lack of, and strong correlation between laboratory tests and the TEG parameters.

Platelet function tests: a comparative review

In physiological hemostasis a prompt recruitment of platelets on the vessel damage prevents the bleeding by the rapid formation of a platelet plug. Qualitative and/or quantitative platelet defects promote bleeding, whereas the high residual reactivity of platelets in patients on antiplatelet therapies moves forward thromboembolic complications. The biochemical mechanisms of the different phases of platelet activation – adhesion, shape change, release reaction, and aggregation – have been well delineated, whereas their complete translation into laboratory assays has not been so fulfilled. Laboratory tests of platelet function, such as bleeding time, light transmission platelet aggregation, lumiaggregometry, impedance aggregometry on whole blood, and platelet activation investigated by flow cytometry, are traditionally utilized for diagnosing hemostatic disorders and managing patients with platelet and hemostatic defects, but their use is still limited to specialized laboratories. To date, a point-of-care testing (POCT) dedicated to platelet function, using pertinent devices much simpler to use, has now become available (ie, PFA-100, VerifyNow System, Multiplate Electrode Aggregometry [MEA]). POCT includes new methodologies which may be used in critical clinical settings and also in general laboratories because they are rapid and easy to use, employing whole blood without the necessity of sample processing. Actually, these different platelet methodologies for the evaluation of inherited and acquired bleeding disorders and/or for monitoring antiplatelet therapies are spreading and the study of platelet function is strengthening. In this review, well-tried and innovative platelet function tests and their methodological features and clinical applications are considered.

Transfusion therapy in paediatric trauma patients: a review of the literature

Haemorrhage is a leading cause of death in paediatric trauma patients. Predefined massive transfusion protocols (MTP) have the potential to significantly reduce mortality by treating haemorrhagic shock and coagulopathy, in adhering to the principles of haemostatic resuscitation with rapid administration of balanced ratios of packed red blood cells (RBC), fresh frozen plasma (FFP) and platelets (PLT).

Because of their substantial physiological reserve, initial vital signs may not be good predictors of early haemorrhage in paediatric patients. Determining the triggers for MTP activation in paediatric trauma patients is challenging, and the optimal blood product ratio that will increase survival in massively bleeding paediatric trauma patients has yet to be determined. To date, only a few small descriptive studies and case reports have investigated the use of predefined MTP in paediatric trauma patients.

MTP with increased FFP or PLT to RBC ratios combined with viscoelastic haemostatic assay (VHA) guided haemostatic resuscitation have not yet been tested in paediatric populations but based on results from adult trauma patients, this therapeutic approach seems promising.

Considering the high prevalence of early coagulopathy in paediatric trauma patients, immediate identification and implementation of VHA-directed treatment of traumatic coagulopathy could ensure faster haemostasis and thereby, potentially, reduce bleeding as well as the total transfusion requirements and further improve outcome in paediatric trauma patients. Prospective randomized trials investigating this therapeutic approach in paediatric trauma patients are highly warranted.

Point of care coagulation testing in neurosurgery

Impaired haemostasis represents a major risk factor for bleeding complications in neurosurgical patients. Coagulopathy commonly occurs after (brain) trauma and major haemorrhage or originates from antithrombotic medication. Point of care (POC) devices for bedside assessment of haemostatic parameters are increasingly used in various medical specialties. Results can be instantly implemented into treatment modalities as results are delivered within a very short period. POC coagulation testing has also shown beneficial effects in the treatment of neurosurgical patients. Identification of hyperfibrinolysis is achieved through viscoelastic testing of haemostasis and bedside coagulometry hastens the management of anticoagulated patients in need of urgent neurosurgical procedures. Results of POC testing of platelet function have been correlated with patient outcomes after traumatic brain injury and furthermore, quantification of antiplatelet medication effects on platelet activity is made possible through the use of these devices. Further studies are needed to characterise the potential of POC testing of platelet function. Antiplatelet medication plays an important role in regard to haemorrhagic and thromboembolic risks. Therefore, POC testing of platelet activity may improve treatment modalities in patients undergoing neurosurgical procedures as well as neurointerventional procedures (such as intracranial stent placement). In this article we summarise the available data of POC testing in neurosurgical patients and discuss the potential of these devices in this field. POC technologies have improved patient care in various medical fields and in our view it is likely that this will also apply to the field of neurosurgery.

Assessment of platelet function: Laboratory and point-of-care methods

In the event of blood vessel damage, human platelets are promptly recruited on the site of injury and, after their adhesion, activation and aggregation, prevent blood loss with the formation of a clot. The consequence of abnormal regulation can be either hemorrhage or the development of thrombosis. Qualitative and/or quantitative defects in platelets promote bleeding, whereas the residual reactivity of platelets, despite antiplatelet therapies, play an important role in promoting arterial thrombotic complications. Platelet function is traditionally assessed to investigate the origin of a bleeding syndrome, to predict the risk of bleeding prior surgery or during pregnancy or to monitor the efficacy of antiplatelet therapy in thrombotic syndromes that, now, can be considered a new discipline. “Old” platelet function laboratory tests such as the evaluation of bleeding time and the platelet aggregation analysis in platelet-rich plasma are traditionally utilized to aid in the diagnosis and management of patients with platelet and hemostatic disorders and used as diagnostic tools both in bleeding and thrombotic diathesis in specialized laboratories. Now, new and renewed automated systems have been introduced to provide a simple, rapid assessment of platelet function including point of care methods. These new methodologies are also suitable for being used in non-specialized laboratories and in critical area for assessing platelet function in whole blood without the requirement of sample processing. Some of these methods are also beginning to be incorporated into routine clinical use and can be utilized as not only as first panel for the diagnosis of platelet dysfunction, but also for monitoring anti-platelet therapy and to potentially assess risk of both bleeding and/or thrombosis.