Influence of resuscitation fluids, fresh frozen plasma and antifibrinolytics on fibrinolysis in a thrombelastography-based, in-vitro, whole-blood model

Variability of fibrinolytic activity in pregnant patients exposed to tissue plasminogen activator: an in vitro study utilizing rotational thromboelastometry

BACKGROUND

The investigation into the variability of fibrinolysis in obstetric patients is notably limited despite its relevance to postpartum hemorrhage. We investigate an in vitro model of fibrinolysis measured by rotational thromboelastrometry (ROTEM) in maternal blood samples with lysis stimulated by tissue plasminogen activator (tPA).

METHODS

Written informed consent was obtained from 19 patients at term pregnancy during admission to the labor and delivery unit. Patients who were taking medication affecting coagulation were excluded. Tissue plasminogen activator was added to whole blood samples to a final concentration of 100 or 220 ng/mL prior to ROTEM testing.

RESULTS

The addition of tPA produced high intra-individual fibrinolytic variability for clot firmness and lysis parameters. Patients responded differently to each tPA dose ranging from clot lysis within the range of 0 ng/mL tPA group to complete clot lysis. The coefficient of variation (CV) values for the 220 ng/mL tPA group were: EXTEM MCF 0.510, EXTEM LI30 1.601, FIBTEM MCF 0.349, FIBTEM LI30 2.097. CV values for the 100 ng/mL tPA group were: EXTEM MCF 0.144, EXTEM LI30 1.038, FIBTEM MCF 0.096, FIBTEM LI30 1.238.

CONCLUSION

We demonstrate a wide range of fibrinolytic response in the obstetric population to exogeneous tPA. We found subgroups of patients that were very responsive to tPA and insensitive to tPA. This study represents a preliminary exploration into classifying the obstetric fibrinolytic phenotypes. Further research will integrate relevant coagulation factors to establish a predictive model for testing susceptibility to lysis that can be applied at the point of care.

Hyperfibrinolysis drives mechanical instabilities in a simulated model of trauma induced coagulopathy

INTRODUCTION

Trauma induced coagulopathy (TIC) is common after severe trauma, increasing transfusion requirements and mortality among patients. TIC has several phenotypes, with primary hyperfibrinolysis being among the most lethal. We aimed to investigate the contribution of hypercoagulation, hemodilution, and fibrinolytic activation to the hyperfibrinolytic phenotype of TIC, by examining fibrin formation in a plasma-based model of TIC. We hypothesized that instabilities arising from TIC will be due primarily to increased fibrinolytic activation rather than hemodilution or tissue factor (TF) induced hypercoagulation.

METHODS

The influence of TF, hemodilution, fibrinogen consumption, tissue plasminogen activator (tPA), and the antifibrinolytic tranexamic acid (TXA) on plasma clot formation and structure were examined using rheometry, optical properties, and confocal microscopy. These were then compared to plasma samples from trauma patients at risk of developing TIC.

RESULTS

Combining TF-induced clot formation, 15 % hemodilution, fibrinogen consumption, and tPA-induced fibrinolysis, the clot characteristics and hyperfibrinolysis were consistent with primary hyperfibrinolysis. TF primarily increased fibrin polymerization rates and reduced fiber length. Hemodilution decreased clot optical density but had no significant effect on mechanical clot stiffness. TPA addition induced primary clot lysis as observed mechanically and optically. TXA restored mechanical clot formation but did not restore clot structure to control levels. Patients at risk of TIC showed increased clot formation, and lysis like that of our simulated model.

CONCLUSIONS

This simulated TIC plasma model demonstrated that fibrinolytic activation is a primary driver of instability during TIC and that clot mechanics can be restored, but clot structure remains altered with TXA treatment.

Management of Anticoagulation during Extracorporeal Membrane Oxygenation in Children

Extracorporeal Membrane Oxygenation (ECMO) is often used in critically ill children with severe cardiopulmonary failure. Worldwide, about 3600 children are supported by ECMO each year, with an increase of 10% in cases per year. Although anticoagulation is necessary to prevent circuit thrombosis during ECMO support, bleeding and thrombosis are associated with significantly increased mortality risk. In addition, maintaining balanced hemostasis is a challenging task during ECMO support. While heparin is a standard anticoagulation therapy in ECMO, recently, newer anticoagulant agents are also in use. Currently, there is a wide variation in anticoagulation management and diagnostic monitoring in children receiving ECMO. This review intends to describe the pathophysiology of coagulation during ECMO support, review of literature on current and newer anticoagulant agents, and outline various diagnostic tests used for anticoagulation monitoring. We will also discuss knowledge gaps and future areas of research.

28-day thawed plasma maintains α2 -antiplasmin levels and inhibits tPA-induced fibrinolysis

INTRODUCTION

Evidence supports the use of plasma-first resuscitation in the treatment of trauma-induced coagulopathy (TIC). While thawed plasma (TP) has logistical benefits, the ability of plasma proteins to attenuate fibrinolysis and correct TIC remain unknown. We hypothesize that TP retains the ability to inhibit tissue plasminogen activator(tPA)-induced fibrinolysis at 28-day storage.

METHODS

Healthy volunteers underwent blood draws followed by 50% dilution of whole blood (WB) with TP at 28-, 21-, 14-, 7-, 5-, and, 0-day storage, normal saline (NS), and WB control. Samples underwent citrated tPA-challenge (75 ng/ml) thromboelastography (TEG). Plasminogen activator inhibitor-1 (PAI-1) and α₂ -antiplasmin (α₂ -AP) concentrations in thawed or stored plasma were determined.

RESULTS

In the presence of tPA, 28-day TP inhibited tPA-induced coagulopathy as effectively as WB. 28-day TP had a similar R-time, MA, and fibrinolysis (P > 0·05 for all) compared to WB, while angle was enhanced (P = 0·02) compared to WB. Significant correlations were present between storage time and clot strength (P = 0·04) and storage time and fibrinolysis (P = 0·0029). Active PAI-1 levels in thawed plasma were 1·10 ± 0·54 ng/mL while total PAI-1 levels were 4·79 ± 1·41 ng/mL. There was no difference of α₂ -AP levels in FFP (40·45 ± 3·5 μg/mL) compared to plasma thawed for 14 (36·78 ± 5·39 μg/mL, P = 0·65) or 28 days (45·16 ± 5·61 μg/mL, P = 0·51).

DISCUSSION

Thawed plasma retained the ability to inhibit tPA-induced fibrinolysis over 28-day storage at 1-4°C. α₂ -AP levels were maintained in plasma thawed for 28 days and FFP. These in vitro results suggest consideration should be made to increasing the storage life of TP.

Prediction of bleeding by thromboelastography in ICU patients with haematological malignancy and severe sepsis

: ICU patients with haematological malignancy have an increased risk of bleeding. Recently, global haemostatic methods such as thromboelastography (TEG) have gained impact in evaluating coagulation. The aim of this study was to observe whether TEG could predict bleeding in haematological ICU patients with severe sepsis. Post-hoc single-centre analysis of patients with haematological malignancy included in the Scandinavian Starch for Severe Sepsis/Septic Shock (6S) trial. Clinical characteristics, TEG measurements and details regarding bleeding complications were retrieved from the 6S database. The association between TEG and bleeding were analysed by Cox regression and receiver operating characteristic curves. A total of 202 patients with severe sepsis were admitted to the ICU of Rigshospitalet, Copenhagen and included in the 6S trial. Forty-one had haematological malignancy and were analysed in the current study. During ICU stay, 20 patients (49%) had bleeding complications and 13 (32%) patients bled within the first 5 ICU days. We observed no associations between TEG and subsequent bleeding in Cox regression models. TEG variables at baseline had low predictive value for bleeding. Baseline TEG variables did not add value in identifying patients with high risk of bleeding in ICU patients with haematological malignancy and severe sepsis.

What concentration of tranexamic acid is needed to inhibit fibrinolysis? A systematic review of pharmacodynamics studies

: Intravenous tranexamic acid (TXA) reduces death because of bleeding in patients with trauma and postpartum haemorrhage. However, in some settings intravenous injection is not feasible. To find different routes of administration, we first need to determine the minimal concentration of TXA in the blood that is required to inhibit fibrinolysis.We conducted a systematic review of in-vitro and in-vivo pharmacodynamics studies. We searched MEDLINE, EMBASE, OviSP, and ISI Web of Science from database inception to November 2017 for all in-vitro (including simulated clotting models) or in-vivo studies reporting the relationship between the TXA concentration in blood or plasma and any reliable measure of fibrinolysis.We found 21 studies of which 20 were in vitro and one was in vivo. Most in-vitro studies stimulated fibrinolysis with tissue plasminogen activator and measured fibrinolysis using viscoelastic, optical density, or immunological assays. TXA concentrations between 10 and 15 mg/l resulted in substantial inhibition of fibrinolysis, although concentrations between 5 and 10 mg/l were partly inhibitory.TXA concentrations of 10-15 mg/l may be suitable targets for pharmacokinetic studies, although TXA concentrations above 5 mg/l may also be effective.

Contractile forces in platelet aggregates under microfluidic shear gradients reflect platelet inhibition and bleeding risk

Platelets contract forcefully after their activation, contributing to the strength and stability of platelet aggregates and fibrin clots during blood coagulation. Viscoelastic approaches can be used to assess platelet-induced clot strengthening, but they require thrombin and fibrin generation and are unable to measure platelet forces directly. Here, we report a rapid, microfluidic approach for measuring the contractile force of platelet aggregates for the detection of platelet dysfunction. We find that platelet forces are significantly reduced when blood samples are treated with inhibitors of myosin, GPIb-IX-V, integrin α_IIbβ_3, P2Y₁₂, or thromboxane generation. Clinically, we find that platelet forces are measurably lower in cardiology patients taking aspirin. We also find that measuring platelet forces can identify Emergency Department trauma patients who subsequently require blood transfusions. Together, these findings indicate that microfluidic quantification of platelet forces may be a rapid and useful approach for monitoring both antiplatelet therapy and traumatic bleeding risk.

Platelet aggregates generate contractile forces that contribute to their cohesion and adhesion. Here, Ting et al. develop a microfluidic device to measure contractile forces generated by platelet aggregates, and find it can detect the response of platelets to pharmacological agents and predict bleeding risk in trauma patients.

Thromboelastography-Guided Therapy of Hemorrhagic Complications after Craniopharyngioma Resection: Case-Based Update

PURPOSE

Thromboelastography (TEG) is a point-of-care test that evaluates the entire hemostatic process. The use of TEG is expanding in multiple pediatric surgical disciplines. However, there is very little literature regarding its application in pediatric neurosurgical patients.

METHODS

The authors provide a case-based update and literature review regarding potential applications of TEG to pediatric neurosurgical patients.

RESULTS

The authors describe a 12-year-old female who experienced a number of complications after a craniopharyngioma resection. The patient suffered multiple new intraventricular hemorrhages with removal of external ventricular drains. Standard coagulopathy tests did not reveal any abnormalities. However, an abnormal TEG value suggested primary hyperfibrinolysis, which led to a change in medical management. The patient did not suffer any further bleeding episodes after the change in treatment.

CONCLUSIONS

The authors discuss a case where TEG influenced patient management and identified a problem despite normal values of standard laboratory tests. Neurosurgeons should be aware of the potential benefits for TEG testing in pediatric patients.

Fibrinolysis in trauma: a review

Fibrinolytic dysregulation is an important mechanism in traumatic coagulopathy. It is an incompletely understood process that consists of a spectrum ranging from excessive breakdown (hyperfibrinolysis) and the shutdown of fibrinolysis. Both hyperfibrinolysis and shutdown are associated with excess mortality and post-traumatic organ failure. The pathophysiology appears to relate to endothelial injury and hypoperfusion, with several molecular markers identified in playing a role. Although there are no universally accepted diagnostic tests, viscoelastic studies appear to offer the greatest potential for timely identification of patients presenting with fibrinolytic dysregulation. Treatment is multimodal, involving prompt hemorrhage control and resuscitation, with controversy surrounding the use of antifibrinolytic drug therapy. This review presents the current evidence on the pathophysiology, diagnostic challenges, as well as the management of this hemostatic dysfunction.

LEVEL OF EVIDENCE

Level III.

Rationale for the selective administration of tranexamic acid to inhibit fibrinolysis in the severely injured patient

Postinjury fibrinolysis can manifest as three distinguishable phenotypes: 1) hyperfibrinolysis, 2) physiologic, and 3) hypofibrinolysis (shutdown). Hyperfibrinolysis is associated with uncontrolled bleeding due to clot dissolution; whereas, fibrinolysis shutdown is associated with organ dysfunction due to microvascular occlusion. The incidence of fibrinolysis phenotypes at hospital arrival in severely injured patients is: 1) hyperfibrinolysis 18%, physiologic 18%, and shutdown 64%. The mechanisms responsible for dysregulated fibrinolysis following injury remain uncertain. Animal work suggests hypoperfusion promotes fibrinolysis, while tissue injury inhibits fibrinolysis. Clinical experience is consistent with these observations. The predominant mediator of postinjury hyperfibrinolysis appears to be tissue plasminogen activator (tPA) released from ischemic endothelium. The effects of tPA are accentuated by impaired hepatic clearance. Fibrinolysis shutdown, on the other hand, may occur from inhibition of circulating tPA, enhanced clot strength impairing the binding of tPA and plasminogen to fibrin, or the inhibition of plasmin. Plasminogen activator inhibitor -1 (PAI-1) binding of circulating tPA appears to be a major mechanism for postinjury shutdown. The sources of PAI-1 include endothelium, platelets, and organ parenchyma. The laboratory identification of fibrinolysis phenotype, at this moment, is best determined with viscoelastic hemostatic assays (TEG, ROTEM). While D-dimer and plasmin antiplasmin (PAP) levels corroborate fibrinolysis, they do not provide real-time assessment of the circulating blood capacity. Our clinical studies indicate that fibrinolysis is a very dynamic process and our experimental work suggests plasma first resuscitation reverses hyperfibrinolysis. Collectively, we believe recent clinical and experimental work suggest antifibrinolytic therapy should be employed selectively in the acutely injured patient, and optimally guided by TEG or ROTEM.

Hemoglobin-based oxygen carriers promote systemic hyperfibrinolysis that is both dependent and independent of plasmin

BACKGROUND

Hyperfibrinolysis plays an integral role in the genesis of trauma-induced coagulopathy. Recent data demonstrate that red blood cell lysis promotes fibrinolysis; however, the mechanism is unclear. Hemoglobin-based oxygen carriers (HBOCs) have been developed for resuscitation and have been associated with coagulopathy. We hypothesize that replacement of whole blood (WB) using an HBOC results in a coagulopathy because of the presence of free hemoglobin.

MATERIALS AND METHODS

WB was sampled from healthy donors (n = 6). The clotting profile of each citrated sample was evaluated using native thromboelastography. Serial titrations were performed using both HBOC (PolyHeme) and normal saline (NS; 5%, 25%, and 50%) and evaluated both with and without a 75-ng/mL tissue plasminogen activator (tPA) challenge. Tranexamic acid (TXA) was added to inhibit plasmin-dependent fibrinolysis. Fibrinolysis was measured and recorded as lysis at 30 min (LY30), the percentage of clot LY30 after maximal clot strength. Dilution of WB with NS or HBOC was correlated using LY30 via Spearman rho coefficients. Groups were also compared using a Friedman test and post hoc analysis with a Bonferroni adjustment.

RESULTS

tPA-provoked fibrinolysis was enhanced by both HBOC (median LY30 at 5%, 25%, and 50% titrations: 11%, 21%, and 44%, respectively; Spearman = 0.94; P < 0.001) and NS (11%, 28%, and 58%, respectively; Spearman = 0.790; P < 0.001). However, HBOC also enhanced fibrinolysis without the addition of tPA (1%, 4%, 5%; Spearman = 0.735; P = 0.001) and NS did not (1%, 2%, 1%; r = 0.300; P = 0.186. Moreover, addition of TXA did not alter or inhibit this fibrinolysis (WB versus 50% HBOC: 1.8% versus 5.7%, P = 0.04). There was no significant difference in fibrinolysis of HBOC with or without TXA (50% HBOC versus 50% HBOC + TXA: 5.6% versus 5.7%, P = 0.92). In addition, the increased fibrinolysis seen with NS was reversed when TXA was present (WB versus 50% NS: 1.8% versus 1.7%, P = 1.0).

CONCLUSIONS

HBOCs enhance fibrinolysis both with and without addition of tPA; moreover, this mechanism is independent of plasmin as the phenomenon persists in the presence of TXA. Our findings indicate the hemoglobin molecule or its components stimulate fibrinolysis by both tPA-dependent and innate mechanisms.

Freeze-dried plasma enhances clot formation and inhibits fibrinolysis in the presence of tissue plasminogen activator similar to pooled liquid plasma

BACKGROUND

Systemic hyperfibrinolysis is an integral part of trauma-induced coagulopathy associated with uncontrolled bleeding. Recent data suggest that plasma-first resuscitation attenuates hyperfibrinolysis; however, the availability, transport, storage, and administration of plasma in austere environments remain challenging and have limited its use. Freeze-dried plasma (FDP) is a potential alternative due to ease of storage, longer shelf life, and efficient reconstitution. FDP potentially enhances clot formation and resists breakdown better than normal saline (NS) and albumin and similar to liquid plasma.

STUDY DESIGN AND METHODS

Healthy volunteers underwent citrated blood draw followed by 50% dilution with NS, albumin, pooled plasma (PP), or pooled freeze-dried plasma (pFDP). Citrated native and tissue plasminogen activator (t-PA)-challenge (75 ng/mL) thrombelastography were done. Proteins in PP, pFDP, and albumin were analyzed by mass spectroscopy.

RESULTS

pFDP and PP had superior clot-formation rates (angle) and clot strength (maximum amplitude) compared with NS and albumin in t-PA-challenge thrombelastographies (angle: pFDP, 67.9 degrees; PP, 67.8 degrees; NS, 40.6 degrees; albumin, 35.8 degrees; maximum amplitude: pFDP, 62.4 mm; PP, 63.5 mm; NS, 44.8 mm; albumin, 41.1 mm). NS and albumin dilution increased susceptibility to t-PA-induced hyperfibrinolysis compared with pFDP and PP (NS, 62.4%; albumin, 62.6%; PP, 8.5%; pFDP, 6.7%). pFDP was similar to PP in the attenuation of t-PA-induced fibrinolysis. Most proteins (97%) were conserved during the freeze-dry process, with higher levels in 12% of pFDP proteins compared with PP.

CONCLUSION

pFDP enhances clot formation and attenuates hyperfibrinolysis better than NS and albumin and is a potential alternative to plasma resuscitation in the treatment of hemorrhagic shock.

14-Day thawed plasma retains clot enhancing properties and inhibits tPA-induced fibrinolysis

BACKGROUND

Plasma-first resuscitation attenuates trauma-induced coagulopathy (TIC); however, the logistics of plasma-first resuscitation require thawed plasma (TP) be readily available due to the obligatory thawing time of fresh frozen plasma (FFP). The current standard is storage of TP for up to 5 days at 4°C, based on factor levels at outdate, for use in patients at risk for TIC, but there remains a 2.2% outdated wastage rate. However, the multitude of plasma proteins in attenuating TIC remains unknown. We hypothesize that TP retains the ability to enhance clotting and reduce tPA-induced fibrinolysis at 14-day storage.

METHODS

FFP was thawed and stored at 4°C at the following intervals: 14, 10, 7, 5, 3, and 1-day prior to the experiment. Healthy volunteers underwent blood draws followed by 50% dilution with TP stored at previously mentioned intervals as well as FFP, normal saline (NS), albumin, and whole blood (WB) control. Samples underwent tPA-modified (75 ng/mL) thrombelastography (TEG) with analysis of R-time, angle, maximum amplitude (MA), and LY30.

RESULTS

TEG properties did not change significantly over the thawed storage. 14-day TP retained the ability to inhibit tPA-induced hyperfibrinolysis (median LY30% 9.6%) similar to FFP (5.6%), WB (14.6%), and superior to albumin (59.3%) and NS (58.1%). 14-day TP also retained faster clot formation (median angle, 66.2°) and superior clot strength (MA, 61.5 mm) to albumin (34.8°, 21.6 mm) and NS (41.6°, 32.2 mm).

CONCLUSIONS

TP plasma stored for 14 days retains clot-enhancing ability and resistance to clot degradation similar to FFP. A clinical trial is needed to validate these in vitro results.

Performance of functional fibrinogen thromboelastography in children undergoing congenital heart surgery

BACKGROUND

Functional Fibrinogen assay of the Thromboelastography (FFTEG), a whole blood viscoelastic hemostatic assay, has been used to estimate fibrinogen levels in adult patients undergoing major surgery but its performance in pediatric patients undergoing cardiac surgery requires evaluation. In this study, we evaluate the correlation between FFTEG parameters and standard laboratory tests for fibrinogen and platelet counts before and after cardiopulmonary bypass in children undergoing repair for congenital heart disease.

METHODS

In this prospective observational study, whole blood samples were obtained from children less than 5 years of age undergoing congenital heart surgery with cardiopulmonary bypass before surgical incision and immediately after administration of protamine. Blood samples were analyzed for Thromboelastography, Functional Fibrinogen level measured by FFTEG (FLEV), complete blood counts with platelet count and plasma fibrinogen assay (LFib, Clauss). The primary outcome of this study was to assess the correlation between FFTEG parameters, LFib and platelet counts in neonates, infants, and small children less than 5 years old. Additionally, we studied if postbypass FFTEG parameters could predict critical thresholds of hypofibrinogenemia LFib ≤200 mg·dl^-1 .

RESULTS

One hundred and five children (22 neonates, 51 infants, and 32 small children) were included in the final analysis. FLEV estimated higher fibrinogen levels than LFib in all patients. Before bypass, FLEV was on average 133 mg·dl^-1 higher than LFib (95% confidence interval, CI, 116-150, P < 0.001) for all the patients; after bypass, FLEV was 48 mg·dl^-1 (95% CI: 37-59, P < 0.001) higher than LFib for all the patients. Linear correlation coefficients between FLEV and LFib in all patients were R = 0.41 (95% CI: 0.24-0.56, P < 0.001) before bypass and increased to R = 0.63 (95% CI: 0.51-0.74, P < 0.001) after bypass. Bland Altman analysis performed on postbypass values of FLEV and LFib showed a positive bias of FLEV in estimation of LFib. The magnitude and the variability of the bias for all the patients group was decreased with lower mean of the difference of FLEV and LFib when the average values of FLEV and LFib were <200 mg·dl^-1 . Low linear correlations were noticed between maximal amplitude of platelet contribution to FFTEG and platelet counts both before and after bypass. For predicting the clinical thresholds of postbypass hypofibrinogenemia at plasma fibrinogen levels ≤200 mg·dl^-1 , FLEV and maximal amplitude of the fibrinogen clot generated area under receiver operative curves at 0.90 (95% CI = 0.76-1.0) in neonates, 0.6 (95% CI- 0.42-0.78) in infants, and 0.97 (95% CI = 0.91-1.0) in small children. Based on the receiver operative curves, values of postbypass hypofibrinogenemia with LFib ≤200 g·dl^-1 corresponded to cutoffs of FLEV_POST ≤245 mg·dl^-1 and maximal amplitude of the fibrinogen clot ≤13.4 mm.

CONCLUSION

In pediatric patients undergoing cardiac surgery, FLEV derived from Functional Fibrinogen correlated linearly with plasma fibrinogen levels (Clauss) both before and after CPB. FLEV estimation of plasma fibrinogen was improved after CPB in neonates, infants, and small children. After CPB, FFTEG can be used to predict laboratory diagnosis of critical hypofibrinogenemia (≤200 mg·dl^-1 ) during pediatric cardiac surgery. Further studies are required to assess the impact of predictability of FFTEG on component transfusion during pediatric cardiac surgery.

A Fibrin Cross-linking Polymer Enhances Clot Formation Similar to Factor Concentrates and Tranexamic Acid in an in vitro Model of Coagulopathy

Transfusion of blood components and factor concentrates is clinically used to replenish clotting factors and treat coagulopathy after injury when bleeding is severe. Alternatively, direct manipulation of fibrin polymerization via synthetic cross-linking agents may also improve clot formation during coagulopathic conditions as a novel way to treat coagulopathy. We recently developed a synthetic hemostatic polymer, PolySTAT, that promotes clot formation and stabilizes fibrin network structure by cross-linking fibrin monomers. In this study, we used rotational thromboelastometry (ROTEM) to monitor the effect of PolySTAT on the mechanical strength of clots during clot formation and breakdown in comparison to replacement clotting factors and antifibrinolytics under conditions of simulated trauma-induced coagulopathy (sTIC). Human recombinant activated Factor VII (rFVIIa) shortened clotting onset time and accelerated clotting rate, while tranexamic acid (TXA) eliminated clot lysis and restored maximal clot firmness.In contrast, fibrinogen and PolySTAT were both able to speed up clot formation, increase maximal firmness, and inhibit clot lysis. Furthermore, PolySTAT acted synergistically with TXA and fibrinogen, enhancing their individual effects on clot formation. Thus, manipulating fibrin clot structure by physical cross-linking with a synthetic polymer has beneficial effects on clot formation and may be a viable transfusion strategy for treatment of coagulopathy.

Thromboelastography predictive of death in trauma patients

OBJECTIVES

To determine if thromboelastography (TEG) is predictive of patient outcomes following traumatic injury.

METHODS

A retrospective review of 131 patients with pelvic trauma admitted to a Level II trauma center was conducted over four years from 1 January 2009 to 31 December 2012. Patients were identified retrospectively from a prospectively collected database of acute pelvic trauma (n = 372). Eligible patients were identified from billing/coding data as having fractures of the acetabulum, iliac wing or sacral alae. Patients with incomplete TEG data were excluded (n = 241), as were patients with pathological fractures. TEG clotting variables and traditional clotting variables were recorded.

RESULTS

Evaluation of TEG data revealed 41 patients with abnormal clotting times (TEG R). TEG R > 6 was an independent risk factor for death (OR, 16; 95%CI 5.4-53; P = 0.0001). The death rate was 52% in patients with TEG R values ≥6 (n = 13/25). There was no significant association between traditional clotting markers and death rate.

CONCLUSIONS

TEG reaction time value, representing the time of initial clot formation, was the only hematologic marker predictive of mortality in patients with pelvic trauma. Delay in reaction time was associated with a significantly increased death rate, independent of injury severity. The death rate association was not observed with traditional markers of clotting. Future prospective studies may be warranted to determine the presentation and significance of TEG abnormalities when resuscitating patients with orthopaedic trauma.

Plasma is the physiologic buffer of tissue plasminogen activator-mediated fibrinolysis: rationale for plasma-first resuscitation after life-threatening hemorrhage

BACKGROUND

Prehospital resuscitation with crystalloid exacerbates fibrinolysis, which is associated with high mortality. We hypothesized that plasma compared with crystalloid resuscitation prevents hyperfibrinolysis in a tissue plasminogen activator (tPA)-rich environment via preservation of proteins essential for regulation of fibrinolysis.

STUDY DESIGN

Healthy individuals donated blood, which was assayed using a native (nonactivated) thrombelastography (TEG). Whole-blood was mixed with normal saline (NS) or platelet poor plasma (PPP) at progressive dilutions. Tissue plasminogen activator was added to promote a fibrinolytic environment. In a separate experiment, PPP was run through a 100 kDa filter and liquid remaining on top of the filter (TFP) and below the filter (BFP) was obtained. Whole blood was diluted by 50% with TFP, BFP, and NS and assayed with a tPA TEG challenge. The TFP and BFP were assayed for protein concentration and protein composition.

RESULTS

Normal saline and PPP dilution of whole blood without tPA did not affect clot lysis at 30 minutes (LY30) (NS Spearman's rho 0.300, p = 0.186 and PPP 0.294, p = 0.288). When tPA was added, NS dilution of whole blood increased LY30 in a percentage-dependent manner (0.844, p < 0.001), but did not significantly increase with PPP dilution (0.270, p = 0.202). The difference in LY30 from whole blood to diluted whole blood with PPP (mean change, -1.05, 95% CI, -9.42 to 7.33) was similar with TFP (1.23, 95% CI, -5.20 to 7.66, p = 0.992). However, both BFP (37.65, 95% CI 24.47 to 50.82, p = 0.001) and NS (47.36, 95% CI 34.3 to 60.45, p < 0.001) showed large increases in fibrinolysis compared with PPP.

CONCLUSIONS

Crystalloid and plasma dilution of whole blood does not increase fibrinolysis. However, NS dilution of whole blood increases susceptibility to tPA-mediated fibrinolysis. Plasma resuscitation, simulated by plasma dilution of whole blood, attenuates increased susceptibility to tPA-mediated fibrinolysis. The benefits of plasma resuscitation are mediated through preservation of plasma proteins.

Elevated tissue plasminogen activator and reduced plasminogen activator inhibitor promote hyperfibrinolysis in trauma patients

Severe hyperfibrinolysis after trauma is a poorly understood phenomenon associated with profound shock, serious anatomic injuries, increased transfusions, and high mortality rates. Molecular mechanisms driving hyperfibrinolysis in trauma have not been completely delineated. The authors aimed to determine the relationship between severe hyperfibrinolysis and outcomes in trauma patients and characterize the role of the plasminogen activator (PA) system in this condition. A prospective observational study was performed in 163 adult level I trauma patients admitted between April and August 2012. Blood was collected on admission, and fibrinolysis was determined by plasmin-α2 antiplasmin (PAP) levels. Tissue-derived and urokinase PA (tPA and uPA, respectively), PA inhibitor (PAI-1), fibrinogen, and antithrombin levels were also measured. Patient demographics, vital signs, laboratory values, mechanisms and severity of injuries, transfusions, and outcomes were collected at admission or from patient records. Moderate fibrinolysis was defined as PAP level 1,500 to 20,000 μg/L and severe hyperfibrinolysis as PAP level more than 20,000 μg/L. Severe hyperfibrinolysis was observed in 10% of patients and associated with increased injury severity, greater transfusions, fewer ventilator and hospital-free days, and higher mortality. Plasmin-α2 antiplasmin level was directly correlated with tPA level and inversely correlated with PAI-1 level. Patients with both elevated tPA and reduced PAI-1 were more severely injured, received more transfusions, and experienced fewer ventilator and hospital-free days. In conclusion, Severe hyperfibrinolysis is observed in a small percentage of trauma patients and is associated with severe injuries, greater transfusions, and worse outcomes. This condition is mediated, in part, by excessive upregulation of profibrinolytic tPA in the absence of concomitant increases in antifibrinolytic PAI-1.