Loss of GPVI and GPIbα contributes to trauma-induced platelet dysfunction in severely injured patients

Immature platelet dynamics are associated with clinical outcomes after major trauma

BACKGROUND

Major trauma results in dramatic changes in platelet behavior. Newly formed platelets are more reactive than older platelets, but their contributions to hemostasis and thrombosis after severe injury have not been previously evaluated.

OBJECTIVES

To determine how immature platelet metrics and plasma thrombopoietin relate to clinical outcomes after major injury.

METHODS

A prospective observational cohort study was performed in adult trauma patients. Platelet counts and the immature platelet fraction (IPF) were measured at admission and 24 hours, 72 hours, and 7 days after injury. Thromboelastometry was performed at admission. Plasma thrombopoietin, c-Mpl, and GPIbα were quantified in a separate cohort. The primary outcome was in-hospital mortality; secondary outcomes were venous thromboembolic events and multiple organ dysfunction syndrome (MODS).

RESULTS

On admission, immature platelet counts (IPCs) were significantly lower in nonsurvivors (n = 40) than in survivors (n = 236; 7.3 × 109/L vs 10.6 × 109/L; P = .009), but IPF did not differ. Similarly, impaired platelet function on thromboelastometry was associated with lower admission IPC (9.1 × 109/L vs 11.9 × 109/L; P < .001). However, at later time points, we observed significantly higher IPF and IPC in patients who developed venous thromboembolism (21.0 × 109/L vs 11.1 × 109/L; P = .02) and prolonged MODS (20.9 × 109/L vs 11 × 109/L; P = .003) than in those who did not develop complications. Plasma thrombopoietin levels at admission were significantly lower in nonsurvivors (P < .001), in patients with MODS (P < .001), and in those who developed venous thromboembolism (P = .04).

CONCLUSION

Lower levels of immature platelets in the acute phase after major injury are associated with increased mortality, whereas higher immature platelet levels at later time points may predispose to thrombosis and MODS.

Plasma Soluble Glycoprotein VI, Platelet Function, Bleeding, and Ischemic Events in Patients Undergoing Elective Percutaneous Coronary Intervention

BACKGROUND AND AIMS

 Glycoprotein VI (GPVI) is the major platelet-specific collagen receptor. GPVI shedding with generation of soluble GPVI (sGPVI) is an endogenous feedback mechanism preventing platelet overstimulation. sGPVI has not been investigated in patients with chronic coronary syndrome (CCS) undergoing percutaneous coronary intervention (PCI), especially regarding its potential value as a predictor of ischemic and bleeding risk.

METHODS

 Baseline plasma sGPVI levels were available in 318 patients with CCS undergoing PCI. Platelet function was assessed by measuring both adenosine diphosphate (ADP) and collagen-induced platelet aggregation. Co-primary endpoints were a composite of death or myocardial injury at 48 hours after PCI, and Bleeding Academic Research Consortium (BARC) type 1 to 5 bleeding at 30 days.

RESULTS

 There was no significant correlation between sGPVI and platelet function at baseline or at 48 hours after PCI and loading with antiplatelet drugs. Baseline plasma sGPVI levels were not associated with the ischemic risk: the incidence of the ischemic endpoint was 25.0% in the lower, 22.9% in the middle, and 26.7% in the upper sGPVI tertile (p = 0.82). There was a significant nonlinear relationship between sGPVI and the risk of bleeding: the incidence of the bleeding endpoint was 11.8% in the lower, 12.6% in the middle, and 26.4% in the upper sGPVI tertile (p = 0.006).

CONCLUSION

 In patients with CCS undergoing PCI, plasma levels of sGPVI did not correlate with ADP- or collagen-induced platelet aggregation. Patients with higher baseline levels of sGPVI may carry an increased risk of bleeding at 30 days after PCI but no excess risk of ischemic events.

Sex dimorphisms in coagulation: Implications in trauma-induced coagulopathy and trauma resuscitation

Trauma-induced coagulopathy (TIC) is one of the leading causes of preventable death in injured patients. Consequently, it is imperative to understand the mechanisms underlying TIC and how to mitigate this mortality. An opportunity for advancement stems from the awareness that coagulation demonstrates a strong sex-dependent effect. Females exhibit a relative hypercoagulability compared to males, which persists after injury and confers improved outcomes. The mechanisms underlying sex dimorphisms in coagulation and its protective effect after injury have yet to be elucidated. This review explores sex dimorphisms in enzymatic hemostasis, fibrinogen, platelets, and fibrinolysis, with implications for resuscitation of patients with TIC.

Platelets in Hemostasis, Thrombosis, and Inflammation After Major Trauma

Trauma currently accounts for 10% of the total global burden of disease and over 5 million deaths per year, making it a leading cause of morbidity and mortality worldwide. Although recent advances in early resuscitation have improved early survival from critical injury, the mortality rate in patients with major hemorrhage approaches 50% even in mature trauma systems. A major determinant of clinical outcomes from a major injury is a complex, dynamic hemostatic landscape. Critically injured patients frequently present to the emergency department with an acute traumatic coagulopathy that increases mortality from bleeding, yet, within 48 to 72 hours after injury will switch from a hypocoagulable to a hypercoagulable state with increased risk of venous thromboembolism and multiple organ dysfunction. This review will focus on the role of platelets in these processes. As effectors of hemostasis and thrombosis, they are central to each phase of recovery from injury, and our understanding of postinjury platelet biology has dramatically advanced over the past decade. This review describes our current knowledge of the changes in platelet behavior that occur following major trauma, the mechanisms by which these changes develop, and the implications for clinical outcomes. Importantly, supported by research in other disease settings, this review also reflects the emerging role of thromboinflammation in trauma including cross talk between platelets, innate immune cells, and coagulation. We also address the unresolved questions and significant knowledge gaps that remain, and finally highlight areas that with the further study will help deliver further improvements in trauma care.

Elevation of White Blood Cell Subtypes in Adult Trauma Patients with Stress-Induced Hyperglycemia

BACKGROUND

Blood immune cell subset alterations following trauma can indicate a patient's immune-inflammatory status. This research explored the influence of stress-induced hyperglycemia (SIH) on platelet counts and white blood cell (WBC) subtypes, including the derived indices of the monocyte-to-lymphocyte ratio (MLR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), in trauma patients.

METHODS

We studied 15,480 adult trauma patients admitted from 1 January 1998 to 31 December 2022. They were categorized into four groups: nondiabetic normoglycemia (NDN, n = 11,602), diabetic normoglycemia (DN, n = 1750), SIH (n = 716), and diabetic hyperglycemia (DH, n = 1412). A propensity score-matched cohort was formed after adjusting for age, sex, and comorbidities, allowing for comparing the WBC subtypes and platelet counts.

RESULTS

Patients with SIH exhibited significantly increased counts of monocytes, neutrophils, and lymphocytes in contrast to NDN patients. However, no significant rise in platelet counts was noted in the SIH group. There were no observed increases in these cell counts in either the DN or DH groups.

CONCLUSIONS

Our results demonstrated that trauma patients with SIH showed significantly higher counts of monocytes, neutrophils, and lymphocytes when compared to NDN patients, whereas the DN and DH groups remained unaffected. This underscores the profound association between SIH and elevated levels of specific WBC subtypes.

Breakthrough infections after COVID-19 vaccinations do not elicit platelet hyperactivation and are associated with high platelet-lymphocyte and low platelet-neutrophil aggregates

Background

Severe COVID-19 is associated with an excessive immunothrombotic response and thromboinflammatory complications. Vaccinations effectively reduce the risk of severe clinical outcomes in patients with COVID-19, but their impact on platelet activation and immunothrombosis during breakthrough infections is not known.

Objectives

To investigate how preemptive vaccinations modify the platelet-immune crosstalk during COVID-19 infections.

Methods

Cross-sectional flow cytometry study of the phenotype and interactions of platelets circulating in vaccinated (n = 21) and unvaccinated patients with COVID-19, either admitted to the intensive care unit (ICU, n = 36) or not (non-ICU, n = 38), in comparison to matched SARS-CoV-2-negative patients (n = 48), was performed.

Results

In the circulation of unvaccinated non-ICU patients with COVID-19, we detected hyperactive and hyperresponsive platelets and platelet aggregates with adaptive and innate immune cells. In unvaccinated ICU patients with COVID-19, most of whom had severe acute respiratory distress syndrome, platelets had high P-selectin and phosphatidylserine exposure but low capacity to activate integrin αIIbβ3, dysfunctional mitochondria, and reduced surface glycoproteins. In addition, in the circulation of ICU patients, we detected microthrombi and platelet aggregates with innate, but not with adaptive, immune cells. In vaccinated patients with COVID-19, who had no acute respiratory distress syndrome, platelets had surface receptor levels comparable to those in controls and did not form microthrombi or platelet-granulocyte aggregates but aggregated avidly with adaptive immune cells.

Conclusion

Our study provides evidence that vaccinated patients with COVID-19 are not associated with platelet hyperactivation and are characterized by platelet-leukocyte aggregates that foster immune protection but not excessive immunothrombosis. These findings advocate for the importance of vaccination in preventing severe COVID-19.

Research and Clinical Approaches to Assess Platelet Function in Flowing Blood

Platelet adhesion and activation is fundamental to the formation of a hemostatic response to limit loss of blood and instigate wound repair to seal a site of vascular injury. The process of platelet aggregate formation is supported by the coagulation system driving injury-proximal formation of thrombin, which converts fibrinogen to insoluble fibrin. This highly coordinated series of molecular and membranous events must be routinely achieved in flowing blood, at vascular fluid shear rates that place significant strain on molecular and cellular interactions. Platelets have long been recognized to be able to slow down and adhere to sites of vascular injury and then activate and recruit more platelets that forge and strengthen adhesive ties with the vascular wall under these conditions. It has been a major challenge for the Platelet Research Community to construct experimental conditions that allow precise definition of the molecular steps occurring under flow. This brief review will discuss work to date from our group, as well as others that has furthered our understanding of platelet function in flowing blood.

Protease-activated receptors and glycoprotein VI cooperatively drive the platelet component in thromboelastography

BACKGROUND

Thromboelastography (TEG) is used for real-time determination of hemostatic status in patients with acute risk of bleeding. Thrombin is thought to drive clotting in TEG through generation of polymerized fibrin and activation of platelets through protease-activated receptors (PARs). However, the specific role of platelet agonist receptors and signaling in TEG has not been reported.

OBJECTIVES

Here, we investigated the specific receptors and signaling pathways required for platelet function in TEG using genetic and pharmacologic inhibition of platelet proteins in mouse and human blood samples.

METHODS

Clotting parameters (R time, α-angle [α], and maximum amplitude [MA]), were determined in recalcified, kaolin-triggered citrated blood samples using a TEG 5000 analyzer.

RESULTS

We confirmed the requirement of platelets, platelet contraction, and αIIbβ3 integrin function for normal α and MA. Loss of the integrin adaptor Talin1 in megakaryocytes/platelets (Talin1mKO) also reduced α and MA, but only minimal defects were observed in samples from mice lacking Rap1 GTPase signaling. PAR4mKO samples showed impaired α but normal MA. However, impaired TEG traces similar to those in platelet-depleted samples were observed with samples from PAR4mKO mice depleted of glycoprotein VI on platelets or with addition of a Syk inhibitor. We reproduced these results in human blood with combined inhibition of PAR1, PAR4, and Syk.

CONCLUSION

Our results demonstrate that standard TEG is not sensitive to platelet signaling pathways critical for integrin inside-out activation and platelet hemostatic function. Furthermore, we provide the first evidence that PARs and glycoprotein VI play redundant roles in platelet-mediated clot contraction in TEG.

Anti-high-mobility group box-1 treatment strategies improve trauma-induced coagulopathy in a mouse model of trauma and shock

BACKGROUND

Trauma-induced coagulopathy is associated with platelet dysfunction and contributes to early mortality after traumatic injury. Plasma concentrations of the damage molecule high-mobility group box-1 (HMGB-1) increase after trauma, which may contribute to platelet dysfunction. We hypothesised that inhibition of HMGB-1 with a monoclonal antibody (mAb) or with recombinant thrombomodulin (rTM) improves trauma-induced coagulopathy in a murine model of trauma and shock.

METHODS

Male 129S2/SvPasOrlRJ mice were anaesthetised, mechanically ventilated, and randomised into five groups: (i) ventilation control (VENT), (ii) trauma/shock (TS), (iii) TS+anti-HMGB-1 mAb (TS+AB), (iv) TS+rTM (TS+TM), and (v) TS+anti-HMGB-1 mAb+rTM (TS+COMBI). Primary outcome was rotational thromboelastometry EXTEM. Secondary outcomes included tail bleeding time, platelet count, plasma HMGB-1 concentration, and platelet activation.

RESULTS

Trauma and shock resulted in a hypocoagulable thromboelastometry profile, increased plasma HMGB-1, and increased platelet activation markers. TS+AB was associated with improved clot firmness after 5 min compared with TS (34 [33-37] vs 32 [29-34] mm; P=0.043). TS+COMBI was associated with decreased clot formation time (98 [92-125] vs 122 [111-148] s; P=0.018) and increased alpha angle (77 [72-78] vs 69 [64-71] degrees; P=0.003) compared with TS. TS+COMBI also reduced tail bleeding time compared with TS (P=0.007). The TS+TM and TS+COMBI groups had higher platelet counts compared with TS (P=0.044 and P=0.041, respectively).

CONCLUSIONS

Inhibition of HMGB-1 early after trauma in a mouse model improves clot formation and strength, preserves platelet count, and decreases bleeding time.

Association between plasma metal elements and platelet dysfunction in trauma-induced coagulopathy rat model

BACKGROUND

Disorders of metal elements and platelet dysfunction are common in patients with trauma-induced coagulopathy (TIC).

AIM

The aim of this study was to explore the potential role of plasma metal elements in platelet dysfunction in TIC.

METHODS

Thirty Sprague-Dawley rats were divided into control, hemorrhage shock (HS) and multiple injury (MI) groups. At timepoints of 0.5 and 3 h after trauma and being documented as _{HS 0.5 h}, HS_3 h, _{MI 0.5 h} or MI_3 h, blood samples were harvested for inductively coupled plasma mass spectrometer, conventional coagulation function and thromboelastograph.

RESULTS

The plasma zinc (Zn), vanadium (V) and cadmium (Ca) decreased initially in HS _0.5 h and recovered slightly in HS_3 h, whereas their plasma concentrations continued to decrease from beginning till MI_3 h (p < 0.05). In HS, plasma Ca, V and nickel were negatively correlated to the time taken to reach the initial formation (R), whereas R was positively correlated to plasms Zn, V, Ca and selenium in MI (p < 0.05). In MI, plasma Ca was positively correlated to maximum amplitude, and plasma V was positively correlated to platelet count (p < 0.05).

CONCLUSION

The plasma concentrations of Zn, V and Ca appeared to contribute to platelet dysfunction in _{HS 0.5 h}, HS_3 h, _{MI 0.5 h} and MI_3 h, which were trauma type sensitive.

Temporal in vivo platelet labeling in mice reveals age-dependent receptor expression and conservation of specific mRNAs

The proportion of young platelets, also known as newly formed or reticulated, within the overall platelet population has been clinically correlated with adverse cardiovascular outcomes. However, our understanding of this is incomplete because of limitations in the technical approaches available to study platelets of different ages. In this study, we have developed and validated an in vivo temporal labeling approach using injectable fluorescent antiplatelet antibodies to subdivide platelets by age and assess differences in functional and molecular characteristics. With this approach, we found that young platelets (<24 hours old) in comparison with older platelets respond to stimuli with greater calcium flux and degranulation and contribute more to the formation of thrombi in vitro and in vivo. Sequential sampling confirmed this altered functionality to be independent of platelet size, with distribution of sizes of tracked platelets commensurate with the global platelet population throughout their 5-day lifespan in the circulation. The age-associated decrease in thrombotic function was accompanied by significant decreases in the surface expression of GPVI and CD31 (PECAM-1) and an increase in CD9. Platelet messenger RNA (mRNA) content also decreased with age but at different rates for individual mRNAs indicating apparent conservation of those encoding granule proteins. Our pulse-chase-type approach to define circulating platelet age has allowed timely reexamination of commonly held beliefs regarding size and reactivity of young platelets while providing novel insights into the temporal regulation of receptor and protein expression. Overall, future application of this validated tool will inform age-based platelet heterogeneity in physiology and disease.

Revacept, an Inhibitor of Platelet Adhesion in Symptomatic Carotid Stenosis: A Multicenter Randomized Phase II Trial

BACKGROUND

Patients with symptomatic internal carotid artery (ICA) stenosis are at high risk of recurrent ischemic stroke and require early interventional treatment and antiplatelet therapy. Increased bleeding rates might counterbalance the periprocedural efficacy of intensified platelet inhibition. We aim to investigate, whether Revacept, a competitive antagonist of glycoprotein VI, adjunct to standard antiplatelet therapy reduces the occurrence of ischemic lesions in patients with symptomatic ICA stenosis.

METHODS

International, multicenter (16 sites), 3-arm, randomized (1:1:1), double-blind, and placebo-controlled study with parallel groups, including patients with symptomatic ICA stenosis. A single infusion over 20 minutes of either placebo, 40 mg or 120 mg Revacept in addition to guideline-conform antiplatelet therapy was evaluated with regard to the exploratory efficacy end point: Number of new ischemic lesions on diffusion-weighted magnetic resonance imaging after treatment initiation. Main clinical outcome was the combined safety and efficacy end point including any stroke or death, transient ischemic attack, myocardial infarction, coronary intervention, and bleeding complications during follow-up.

RESULTS

Out of 160 randomized patients, 158 patients (68±10.1 years, 24% female) received study medication (51 patients placebo, 54 patients 40 mg Revacept and 53 patients 120 mg Revacept) and were followed for 11.2±2.3 months. A total of 1.16 (95% CI, 0.88-1.53)/1.05 (95% CI, 0.78-1.42; P=0.629)/0.63 (95% CI, 0.43-0.93) new diffusion-weighted magnetic resonance imaging lesions per patient were detected in the placebo/40 mg/120 mg Revacept groups, without statistical evidence of a difference. A reduction of the combined safety and efficacy end point during the study period was observed in patients who received 120 mg (HR, 0.46 [95% CI, 0.21-0.99]; P=0.047), but not 40 mg Revacept compared with placebo (HR, 0.72 [95% CI, 0.37-1.42]; P=0.343).

CONCLUSIONS

Revacept 120 mg reduced the combined safety and efficacy end point in patients with symptomatic ICA stenosis.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique Identifier: NCT01645306.

GPVI expression is linked to platelet size, age, and reactivity

Juvenile platelets show increased GPVI expression.

These platelets are highly responsive and more abundant among large platelets.

Platelets within one individual display heterogeneity in reactivity, size, age, and expression of surface receptors. To investigate the combined intraindividual contribution of platelet size, platelet age, and receptor expression levels on the reactivity of platelets, we studied fractions of large and small platelets from healthy donors separated by using differential centrifugation. Size-separated platelet fractions were perfused over a collagen-coated surface to assess thrombus formation. Multicolor flow cytometry was used to characterize resting and stimulated platelet subpopulations, and platelet age was determined based on RNA and HLA-I labeling. Signal transduction was analyzed by measuring consecutive phosphorylation of serine/threonine-protein kinase Akt. Compared with small platelets, large platelets adhered faster to collagen under flow and formed larger thrombi. Among the large platelets, a highly reactive juvenile platelet subpopulation was identified with high glycoprotein VI (GPVI) expression. Elevated GPVI expression correlated with high HLA-I expression, RNA content, and increased platelet reactivity. There was a stronger difference in Akt phosphorylation and activation upon collagen stimulation between juvenile and older platelets than between large and small platelets. GPVI expression and platelet reactivity decreased throughout platelet storage at 22°C and was better maintained throughout cold storage at 4°C. We further detected higher GPVI expression in platelets of patients with immune thrombocytopenia. Our findings show that high GPVI expression is a feature of highly reactive juvenile platelets, which are predominantly found among the large platelet population, explaining the better performance of large platelets during thrombus formation. These data are important for studies of thrombus formation, platelet storage, and immune thrombocytopenia.

Multiplate Platelet Function Testing upon Emergency Room Admission Fails to Provide Useful Information in Major Trauma Patients Not on Platelet Inhibitors

Platelet dysfunction is a suggested driver of trauma-induced coagulopathy. However, there is still a paucity of data regarding the impact of injury pattern on platelet function and the association of platelet dysfunction on transfusion requirements and mortality. In this retrospective cohort study, patients were grouped into those with isolated severe traumatic brain injury (TBI group), those with major trauma without TBI (MT group), and a combination of both major trauma and traumatic brain injury (MT + TBI group). Platelet function was assessed by whole blood impedance aggregometry (Multiplate^®, MP). Three different platelet activators were used: adenosine-diphosphate (ADP test), arachidonic acid (ASPI test), and thrombin activated peptide-6 (TRAP test). Blood transfusion requirements within 6 h and 24 h and the association of platelet dysfunction on mortality was investigated. A total of 328 predominantly male patients (75.3%) with a median age of 53 (37–68) years and a median ISS of 29 (22–38) were included. No significant difference between the TBI group, the MT group, and the MT + TBI group was detected for any of the investigated platelet function tests. Unadjusted and adjusted for platelet count, the investigated MP assays revealed no significant group differences upon ER admission and were not able to sufficiently predict massive transfusion, neither within the first 6 h nor for the first 24 h after hospital admission. No association between platelet dysfunction measured by MP upon ER admission and mortality was observed. Conclusion: Injury pattern did not specifically impact platelet function measurable by MP. Platelet dysfunction upon ER admission measurable by MP was not associated with transfusion requirements and mortality. The clinical relevance of platelet function testing by MP in trauma patients not on platelet inhibitors is questionable.

The Platelet Collagen Receptor GPVI Is Cleaved by Tspan15/ADAM10 and Tspan33/ADAM10 Molecular Scissors

The platelet-activating collagen receptor GPVI represents the focus of clinical trials as an antiplatelet target for arterial thrombosis, and soluble GPVI is a plasma biomarker for several human diseases. A disintegrin and metalloproteinase 10 (ADAM10) acts as a ‘molecular scissor’ that cleaves the extracellular region from GPVI and many other substrates. ADAM10 interacts with six regulatory tetraspanin membrane proteins, Tspan5, Tspan10, Tspan14, Tspan15, Tspan17 and Tspan33, which are collectively termed the TspanC8s. These are emerging as regulators of ADAM10 substrate specificity. Human platelets express Tspan14, Tspan15 and Tspan33, but which of these regulates GPVI cleavage remains unknown. To address this, CRISPR/Cas9 knockout human cell lines were generated to show that Tspan15 and Tspan33 enact compensatory roles in GPVI cleavage, with Tspan15 bearing the more important role. To investigate this mechanism, a series of Tspan15 and GPVI mutant expression constructs were designed. The Tspan15 extracellular region was found to be critical in promoting GPVI cleavage, and appeared to achieve this by enabling ADAM10 to access the cleavage site at a particular distance above the membrane. These findings bear implications for the regulation of cleavage of other ADAM10 substrates, and provide new insights into post-translational regulation of the clinically relevant GPVI protein.

A new trauma frontier: Exploratory pilot study of platelet transcriptomics in trauma patients

BACKGROUND

The earliest measurable changes to postinjury platelet biology may be in the platelet transcriptome, as platelets are known to carry messenger ribonucleic acids (RNAs), and there is evidence in other inflammatory and infectious disease states of differential and alternative platelet RNA splicing in response to changing physiology. Thus, the aim of this exploratory pilot study was to examine the platelet transcriptome and platelet RNA splicing signatures in trauma patients compared with healthy donors.

METHODS

Preresuscitation platelets purified from trauma patients (n = 9) and healthy donors (n = 5) were assayed using deep RNA sequencing. Differential gene expression analysis, weighted gene coexpression network analysis, and differential alternative splicing analyses were performed. In parallel samples, platelet function was measured with platelet aggregometry, and clot formation was measured with thromboelastography.

RESULTS

Differential gene expression analysis identified 49 platelet RNAs to have differing abundance between trauma patients and healthy donors. Weighted gene coexpression network analysis identified coexpressed platelet RNAs that correlated with platelet aggregation. Differential alternative splicing analyses revealed 1,188 splicing events across 462 platelet RNAs that were highly statistically significant (false discovery rate <0.001) in trauma patients compared with healthy donors. Unsupervised principal component analysis of these platelet RNA splicing signatures segregated trauma patients in two main clusters separate from healthy controls.

CONCLUSION

Our findings provide evidence of finetuning of the platelet transcriptome through differential alternative splicing of platelet RNA in trauma patients and that this finetuning may have relevance to downstream platelet signaling. Additional investigations of the trauma platelet transcriptome should be pursued to improve our understanding of the platelet functional responses to trauma on a molecular level.

Cryoprecipitate as an alternative to platelet transfusion in thrombocytopenia

Platelet transfusions are not always available for bleeding in severe thrombocytopenia, as storage outside of major centers is limited by their short shelf-life. Data are lacking to support alternative available blood products; however, additional fibrinogen has been shown to enhance clot formation in vitro. To test the hypothesis that cryoprecipitate supplementation could improve clot formation in severe thrombocytopenia, eight hematological malignancy patients with platelet counts under 10 × 109/L each had 10 units of apheresis cryoprecipitate transfused prior to planned prophylactic platelet transfusions. The primary endpoint of thromboelastometry amplitude at 20 min increased by a mean of 5.1 mm (p < 0.01) following cryoprecipitate transfusion despite persisting thrombocytopenia. Thromboelastometry clotting times reduced by a mean of 7.8 s (p < 0.05) and alpha angle increased by a mean of 10.6⁰ (p < 0.01). These results are consistent with cryoprecipitate enhancing the strength of the fibrin/platelet meshwork within the forming thrombus. While platelet transfusion remains the standard of care, where platelet supplies are limited, these data provide a rationale for the use of cryoprecipitate to obtain hemostasis in bleeding thrombocytopenic patients.

The effect of shock duration on trauma-induced coagulopathy in a murine model

Background

Trauma-induced coagulopathy (TIC) is a life-threatening condition associated with high morbidity and mortality. TIC can present with different coagulation defects. In this study, the aim was to determine the effect of shock duration on TIC characteristics. We hypothesized that longer duration of shock leads to a more hypocoagulable rotational thromboelastometry (ROTEM) profile compared to a shorter duration of shock.

Methods

Male B57BL/6J(c) mice (n = 5–10 per group) were sedated and mechanically ventilated. Trauma was induced by bilateral lower limb fractures and crush injuries to the liver and small intestine. Shock was induced by blood withdrawals until a mean arterial pressure of 25–30 mmHg was achieved. Groups reflected trauma and shock for 30 min (TS30) and trauma and shock for 90 min (TS90). Control groups included ventilation only (V90) and trauma only (T90).

Results

Mice in the TS90 group had significantly increased base deficit compared to the V90 group. Mortality was 10% in the TS30 group and 30% in the TS90 group. ROTEM profile was more hypocoagulable, as shown by significantly lower maximum clot firmness (MCF) in the TS30 group (43.5 [37.5–46.8] mm) compared to the TS90 group (52.0 [47.0–53.0] mm, p = 0.04). ROTEM clotting time and parameters of clot build-up did not significantly differ between groups.

Conclusions

TIC characteristics change with shock duration. Contrary to the hypothesis, a shorter duration of shock was associated with decreased maximum clotting amplitudes compared to a longer duration of shock. The effect of shock duration on TIC should be further assessed in trauma patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-021-00428-1.

Acquired platelet GPVI receptor dysfunction in critically ill patients with sepsis

Glycoprotein VI (GPVI), the platelet immunoreceptor tyrosine activating motif (ITAM) receptor for collagen, plays a striking role on vascular integrity in animal models of inflammation and sepsis. Understanding ITAM-receptor signaling defects in humans suffering from sepsis may improve our understanding of the pathophysiology, especially during disease onset. In a pilot study, platelets from 15 patients with sepsis were assessed consecutively at day of admission, day 5 to 7, and the day of intensive care unit (ICU) discharge and subjected to comprehensive analyses by flow cytometry, aggregometry, and immunoblotting. Platelet function was markedly reduced in all patients. The defect was most prominent after GPVI stimulation with collagen-related peptide. In 14 of 15 patients, GPVI dysfunction was already present at time of ICU admission, considerably before the critical drop in platelet counts. Sepsis platelets failed to transduce the GPVI-mediated signal to trigger tyrosine phosphorylation of Syk kinase or LAT. GPVI deficiency was partially inducible in platelets of healthy donors through coincubation in whole blood, but not in plasma from patients with sepsis. Platelet aggregation upon GPVI stimulation increased only in those patients whose condition ameliorated. As blunted GPVI signaling occurred early at sepsis onset, this defect could be exploited as an indicator for early sepsis diagnosis, which needs to be confirmed in prospective studies.

Higher coagulation activity in hip fracture patients: A case-control study using rotational thromboelastometry

INTRODUCTION

Trauma-induced coagulopathy has been extensively investigated in the multitrauma setting, but only sparsely following moderate orthopedic trauma. The purpose of this study was to evaluate changes in the hemostatic profile of patients with hip fractures, using rotational thromboelastometry (ROTEM).

METHODS

198 patients with hip fractures who underwent surgery were included in the study. A matched group of 52 healthy individuals was also enrolled. Demographics, conventional laboratory assays, and ROTEM parameters were recorded and compared between patients and healthy adults. The preoperative and postoperative ROTEM values of fractured patients were also compared.

RESULTS

The conventional coagulation assays were similar for the 2 groups. However, several ROTEM parameters including EXTEM MCF (P < .001), EXTEM alpha angle (P < .001), INTEM MCF (P < .001), INTEM A10 (P < .001), and INTEM alpha angle (P < .001) significantly differed between the 2 groups indicating a higher coagulation potential following hip fractures. Also, fractured patients had significantly lower INTEM and EXTEM CT values (P = .008 and P = .012, respectively) and significantly lower INTEM and EXTEM CFT values (P < .001). Adjusted analysis for confounders further confirmed the direct relationship between hip fracture and higher coagulation activity. Last, INTEM CT and CFT significantly decreased (P = .008 and P < .001, respectively), while INTEM MCF, A10, and alpha angle significantly increased (P < .001) postoperatively, indicating that surgery further increases the coagulation potential.

CONCLUSION

A higher coagulation activity following hip fractures and surgical treatment can be detected by ROTEM shortly after the injury, even when this is undetectable by conventional coagulation assays.