Background The transcriptional repressor positive regulatory domain I–binding factor 1 (PRDM1) is expressed in adult mouse dorsal root ganglion and regulates the formation and function of peripheral sensory neurons. The authors hypothesized that PRDM1 in the dorsal root ganglion may contribute to peripheral nerve injury–induced nociception regulation and that its mechanism may involve Kv4.3 channel transcriptional repression. Methods Nociception was induced in C57BL/6 mice by applying chronic constriction injury, complete Freund’s adjuvant, or capsaicin plantar injection. Nociceptive response was evaluated by mechanical allodynia, thermal hyperalgesia, cold hyperalgesia, or gait analysis. The role of PRDM1 was evaluated by injection of Prdm1 knockdown and overexpression adeno-associated viruses. The interaction of PRDM1 at the Kv4.3 ( Kcnd3 ) promoter was evaluated by chromatin immunoprecipitation assay. Excitability of dorsal root ganglion neurons was evaluated by whole cell patch clamp recordings, and calcium signaling in spinal dorsal horn neurons was evaluated by in vivo two-photon imaging. Results Peripheral nerve injury increased PRDM1 expression in the dorsal root ganglion, which reduced the activity of the Kv4.3 promoter and repressed Kv4.3 channel expression (injured vs. uninjured; all P < 0.001). Knockdown of PRDM1 rescued Kv4.3 expression, reduced the high excitability of injured dorsal root ganglion neurons, and alleviated peripheral nerve injury–induced nociception (short hairpin RNA vs. Scram; all P < 0.05). In contrast, PRDM1 overexpression in naive mouse dorsal root ganglion neurons diminished Kv4.3 channel expression and induced hyperalgesia (PRDM1 overexpression vs. control, mean ± SD; n = 13; all P < 0.0001) as evaluated by mechanical allodynia (0.6 ± 0.3 vs. 1.2 ± 0.2 g), thermal hyperalgesia (5.2 ± 1.3 vs . 9.8 ± 1.7 s), and cold hyperalgesia (3.4 ± 0.5 vs. 5.3 ± 0.6 s). Finally, PRDM1 downregulation in naive mice reduced the calcium signaling response of spinal dorsal horn neurons to thermal stimulation. Conclusions PRDM1 contributes to peripheral nerve injury–induced nociception by repressing Kv4.3 channel expression in injured dorsal root ganglion neurons. Editor’s Perspective What We Already Know about This Topic The hyperexcitability of sensory neurons contributes to chronic pain after nerve injury The diminished expression of membrane-stabilizing potassium ion channels contributes to this hyperexcitability What This Article Tells Us That Is New After nerve injury in mice, the enhanced expression of the positive regulatory domain I–binding factor 1 (PRDM1) reduced the expression of the Kv4.3 potassium ion channel The reduced expression of Kv4.3 caused nociceptive sensitization in male and female mice Conversely, maneuvers that enhanced Kv4.3 expression reduced nociceptive sensitivity in mice, suggesting that this regulatory pathway may have central importance in pain after nerve injury

Background Recent studies suggest that adult-specific treatment options for fibrinogen replacement during bleeding may be less effective in neonates. This is likely due to structural and functional differences found in the fibrin network between adults and neonates. In this investigation, the authors performed a comparative laboratory-based study between immature and adult human and porcine plasma samples in order to determine if piglets are an appropriate animal model of neonatal coagulopathy. Methods Adult and neonatal human and porcine plasma samples were collected from the Children’s Hospital of Atlanta and North Carolina State University College of Veterinary Medicine, respectively. Clots were formed for analysis and fibrinogen concentration was quantified. Structure was examined through confocal microscopy and cryogenic scanning electron microscopy. Function was assessed through atomic force microscopy nanoindentation and clotting and fibrinolysis assays. Lastly, novel hemostatic therapies were applied to neonatal porcine samples to simulate treatment. Results All sample groups had similar plasma fibrinogen concentrations. Neonatal porcine and human plasma clots were less branched with lower fiber densities than the dense and highly branched networks seen in adult human and porcine clots. Neonatal porcine and human clots had faster degradation rates and lower clot stiffness values than adult clots (stiffness [mmHg] mean ± SD: neonatal human, 12.15 ± 1.35 mmHg vs. adult human, 32.25 ± 7.13 mmHg; P = 0.016; neonatal pig, 10.5 ± 8.25 mmHg vs. adult pigs, 32.55 ± 7.20 mmHg; P = 0.015). The addition of hemostatic therapies to neonatal porcine samples enhanced clot formation. Conclusions The authors identified similar age-related patterns in structure, mechanical, and degradation properties between adults and neonates in porcine and human samples. These findings suggest that piglets are an appropriate preclinical model of neonatal coagulopathy. The authors also show the feasibility of in vitro model application through analysis of novel hemostatic therapies as applied to dilute neonatal porcine plasma. Editor’s Perspective What We Already Know about This Topic Neonatal fibrinogen exists in a fetal form until maturation and is structurally and functionally distinct from adult fibrinogen Replacement of neonatal fibrinogen with adult fibrinogen after cardiopulmonary bypass may lead to inconsistent efficacy in treating postcardiopulmonary bypass bleeding The hemostatic system of pigs is similar to that of humans What This Article Tells Us That Is New Fibrinogen concentration and functionality in plasma collected from piglets paralleled those observed in plasma collected from human neonates Fibrin network structure was highly aligned in both neonatal species and highly branched in adults of both species Fibrin network stiffness and degradation patterns in both neonatal species were substantially similar as they were in adults of both species The ex vivo addition of several procoagulant therapies augmented fibrin network properties of diluted piglet plasma

Editor’s Perspective What We Already Know about This Topic Prothrombin complex concentrates are increasingly used as part of bleeding management algorithms in surgery and trauma There are potential risks of thromboembolic complications and disseminated intravascular coagulopathy with prothrombin complex concentrate in this setting, despite the low risks in warfarin reversal What this Article Tells Us That Is New In this animal polytrauma model, 50 IU/kg prothrombin complex concentrate is associated with a risk of disseminated intravascular coagulopathy and thromboembolism The addition of antithrombin appears to balance the procoagulant effects of prothrombin complex concentrate, consequently reducing the risk of complications without impairing efficacy Background The risk of thromboembolic complications with prothrombin complex concentrates (PCCs) appears low when used for reversal of vitamin K antagonists but might be different in other indications ( e.g. , trauma). A difference in risk could arise from the plasma ratio of pro- versus anticoagulant proteins. This study used a porcine trauma model to investigate combined treatment with PCC and antithrombin. The hypothesis was that antithrombin can modulate prothrombotic effects and prevent adverse events of PCC. Methods Nine treatment groups (n = 7 per group) were included: control (placebo), PCC (50 IU/kg), PCC plus antithrombin (three groups, with antithrombin doses of 12.5, 25, or 50 IU/kg), fibrinogen concentrate (100 mg/kg) plus PCC, fibrinogen concentrate plus PCC plus antithrombin dose of 50 IU/kg, tranexamic acid (15 mg/kg) plus fibrinogen concentrate plus PCC, and tranexamic acid plus fibrinogen concentrate plus PCC plus antithrombin dose of 50 IU/kg. In each group, bilateral femur fractures and thorax contusion were followed 60 min later by blunt liver injury. Study treatment was then administered, and animals were subsequently observed for 210 min. Results Total blood loss (mean ± SD) was statistically significantly lower in all three PCC plus antithrombin groups (PCC plus antithrombin dose of 50 IU/kg, 672 ± 63 ml; PCC plus antithrombin dose of 25 IU/kg, 535 ± 72 ml; and PCC plus antithrombin dose of 12.5 IU/kg, 538 ± 50 ml) than in the PCC group (907 ± 132 ml), which in turn had statistically significantly reduced bleeding versus the control group (1,671 ± 409 ml). Signs of disseminated intravascular coagulation were apparent with PCC monotherapy, and early deaths occurred with fibrinogen concentrate plus PCC, attributable to pulmonary emboli. Antithrombin was protective against both of these effects: signs of disseminated intravascular coagulation were absent from the PCC plus antithrombin groups, and there were no early deaths in the group with fibrinogen concentrate plus PCC plus antithrombin dose of 50 IU/kg. Conclusions According to this trauma model, 50 IU/kg PCC increases the risk of disseminated intravascular coagulation and other thromboembolic complications, most notably when coadministered with fibrinogen concentrate. The addition of antithrombin appears to reduce this risk.

Background Although idarucizumab is the preferred treatment for urgent dabigatran reversal, it is not always available. Prothrombin complex concentrate (PCC) may be an alternative and, with bleeding in trauma, additional hemostatic therapy may be required. The authors investigated multimodal treatment in a preclinical polytrauma model. Methods Dabigatran etexilate (30 mg/kg twice daily) was given orally to 45 male pigs for 3 days. On day 4, animals received a dabigatran infusion before blunt liver injury and bilateral femur fractures. After injury, animals were randomized 1:1:1:1:1 to receive placebo (control), tranexamic acid (TXA; 20 mg/kg) plus human fibrinogen concentrate (FCH; 80 mg/kg) (TXA–FCH group), PCC (25 U/kg or 50 U/kg) plus TXA plus FCH (PCC25 and PCC50 groups), or 60 mg/kg idarucizumab (IDA) plus TXA plus FCH (IDA group). Animals were monitored for 240 min after trauma, or until death. Results The degree of injury was similar in all animals before intervention. Control and TXA–FCH animals had the highest total postinjury blood loss (3,652 ± 601 and 3,497 ± 418 ml) and 100% mortality (mean survival time 96 and 109 min). Blood loss was significantly lower in the PCC50 (1,367 ± 273 ml) and IDA (986 ± 144 ml) groups, with 100% survival. Thrombin–antithrombin levels and thrombin generation were significantly elevated in the PCC50 group. Conclusions Idarucizumab may be considered the optimal treatment for emergency reversal of dabigatran anticoagulation. However, this study suggests that PCC may be similarly effective as idarucizumab and could therefore be valuable when idarucizumab is unavailable. (Anesthesiology 2017; 127:852-61)

Background Major trauma is a leading cause of morbidity and mortality worldwide with hemorrhage accounting for 40% of deaths. Acute traumatic coagulopathy exacerbates bleeding, but controversy remains over the degree to which inhibition of procoagulant pathways (anticoagulation), fibrinogen loss, and fibrinolysis drive the pathologic process. Through a combination of experimental study in a murine model of trauma hemorrhage and human observation, the authors’ objective was to determine the predominant pathophysiology of acute traumatic coagulopathy. Methods First, a prospective cohort study of 300 trauma patients admitted to a single level 1 trauma center with blood samples collected on arrival was performed. Second, a murine model of acute traumatic coagulopathy with suppressed protein C activation via genetic mutation of thrombomodulin was used. In both studies, analysis for coagulation screen, activated protein C levels, and rotational thromboelastometry (ROTEM) was performed. Results In patients with acute traumatic coagulopathy, the authors have demonstrated elevated activated protein C levels with profound fibrinolytic activity and early depletion of fibrinogen. Procoagulant pathways were only minimally inhibited with preservation of capacity to generate thrombin. Compared to factors V and VIII, proteases that do not undergo activated protein C–mediated cleavage were reduced but maintained within normal levels. In transgenic mice with reduced capacity to activate protein C, both fibrinolysis and fibrinogen depletion were significantly attenuated. Other recognized drivers of coagulopathy were associated with less significant perturbations of coagulation. Conclusions Activated protein C–associated fibrinolysis and fibrinogenolysis, rather than inhibition of procoagulant pathways, predominate in acute traumatic coagulopathy. In combination, these findings suggest a central role for the protein C pathway in acute traumatic coagulopathy and provide new translational opportunities for management of major trauma hemorrhage.

Background: Fibrinogen concentrate may reduce blood loss after trauma. However, its effect on endogenous fibrinogen synthesis is unknown. The authors investigated the effect of exogenous human fibrinogen on endogenous fibrinogen metabolism in a 24-h porcine trauma model. Methods: Coagulopathy was induced in 20 German Landrace pigs by hemodilution and blunt liver injury. Animals were randomized to receive fibrinogen concentrate (100 mg/kg; infusion beginning 20 min postinjury and lasting approximately 10 min) or saline. Fibrinogen concentration, thromboelastometry, and quantitative reverse transcriptase polymerase chain reaction of fibrinogen genes in liver tissue samples were recorded. Internal organs were examined histologically for emboli. Results: Coagulation parameters were impaired and plasma fibrinogen concentrations were reduced before starting infusion of fibrinogen concentrate/saline. Twenty minutes after starting infusion, exogenous fibrinogen supplementation had increased plasma fibrinogen concentration versus controls (171 ± 19 vs. 63 ± 10 mg/dl [mean ± SD for Multifibren U]; 185 ± 30 vs. 41 ± 4 mg/dl [Thrombin reagent]; P < 0.05 for both comparisons). The between-group difference in plasma fibrinogen concentration diminished thereafter, with maximum concentrations in both groups observed at approximately 24 h, that is, during the acute-phase reaction after trauma. Fibrinogen supplementation did not down-regulate endogenous fibrinogen synthesis (no between-group differences in fibrinogen messenger RNA). Total postinjury blood loss was significantly lower in the fibrinogen group (1,062 ± 216 vs. 1,643 ± 244 ml; P < 0.001). No signs of thromboembolism were observed. Conclusions: Administration of human fibrinogen concentrate did not down-regulate endogenous porcine fibrinogen synthesis. The effect on plasma fibrinogen concentration was most pronounced at 20 min but nonsignificant at approximately 24 h.

Introduction Blood transfusion is associated with increased morbidity and mortality. We developed and implemented an algorithm for coagulation management in cardiovascular surgery based on first-line administration of coagulation factor concentrates combined with point-of-care thromboelastometry/impedance aggregometry. Methods In a retrospective cohort study including 3,865 patients, we analyzed the incidence of intraoperative allogeneic blood transfusions (primary endpoints) before and after algorithm implementation. Results Following algorithm implementation, the incidence of any allogeneic blood transfusion (52.5 vs. 42.2%; P < 0.0001), packed red blood cells (49.7 vs. 40.4%; P < 0.0001), and fresh frozen plasma (19.4 vs. 1.1%; P < 0.0001) decreased, whereas platelet transfusion increased (10.1 vs. 13.0%; P = 0.0041). Yearly transfusion of packed red blood cells (3,276 vs. 2,959 units; P < 0.0001) and fresh frozen plasma (1986 vs. 102 units; P < 0.0001) decreased, as did the median number of packed red blood cells and fresh frozen plasma per patient. The incidence of fibrinogen concentrate (3.73 vs. 10.01%; P < 0.0001) and prothrombin complex concentrate administration (4.42 vs. 8.9%; P < 0.0001) increased, as did their amount administered per year (179 vs. 702 g; P = 0.0008 and 162 × 10³ U vs. 388 × 10³ U; P = 0.0184, respectively). Despite a switch from aprotinin to tranexamic acid, an increase in use of dual antiplatelet therapy (2.7 vs. 13.7%; P < 0.0001), patients' age, proportion of females, emergency cases, and more complex surgery, the incidence of massive transfusion [(≥10 units packed red blood cells), (2.5 vs. 1.26%; P = 0.0057)] and unplanned reexploration (4.19 vs. 2.24%; P = 0.0007) decreased. Composite thrombotic/thromboembolic events (3.19 vs. 1.77%; P = 0.0115) decreased, but in-hospital mortality did not change (5.24 vs. 5.22%; P = 0.98). Conclusions First-line administration of coagulation factor concentrates combined with point-of-care testing was associated with decreased incidence of blood transfusion and thrombotic/thromboembolic events.

Fluid resuscitation after massive hemorrhage in major surgery and trauma may result in extensive hemodilution and coagulopathy, which is of a multifactorial nature. Although coagulopathy is often perceived as hemorrhagic, extensive hemodilution affects procoagulants as well as anticoagulant, profibrinolytic, and antifibrinolytic elements, leading to a complex coagulation disorder. Reduced thrombin activation is partially compensated by lower inhibitory activities of antithrombin and other protease inhibitors, whereas plasma fibrinogen is rapidly decreased proportional to the extent of hemodilution. Adequate fibrinogen levels are essential in managing dilutional coagulopathy. After extensive hemodilution, fibrin clots are more prone to fibrinolysis because major antifibrinolytic proteins are decreased.Fresh frozen plasma, platelet concentrate, and cryoprecipitate are considered the mainstay hemostatic therapies. Purified factor concentrates of plasma origin and from recombinant synthesis are increasingly used for a rapid restoration of targeted factors. Future clinical studies are necessary to establish the specific indication, dosing, and safety of novel hemostatic interventions.

Background A clinical bleeding diathesis is associated with hypothermia. Inhibition of platelet reactivity is the purported cause of this coagulopathy despite inconsistent evidence to support this hypothesis. To clarify the effect of temperature on intrinsic platelet function, platelet GPllb-IIIa activation and P-selectin expression were assessed under normothermic and hypothermic conditions in vitro. Methods Blood was obtained by venipuncture from healthy volunteers. Platelet activation was assessed by aggregometry and by cytometric analysis of platelet binding of fibrinogen, PAC-1, and P-selectin antibodies. Measurements were made at normothermia (37 degrees C), moderate hypothermia (33 degrees C), and profound hypothermia (22 degrees C) after stimulating samples with adenosine diphosphate (ADP), collagen, or thrombin receptor activating peptide. Results Agonist-induced platelet aggregation and fibrinogen binding were significantly greater at 22 degrees C and 33 degrees C than at 37 degrees C. Platelet fibrinogen binding values to 20 micro M ADP were 23,400, 14,300, and 9,700 molecules/platelet at 22 degrees C, 33 degrees C, and 37 degrees C, respectively. The aggregation responses of platelets that were cooled and rewarmed were indistinguishable from those of platelets maintained at 37 degrees C throughout the study. Platelet binding of PAC-1 and P-selectin antibodies was greater under hypothermic conditions. Conclusions Aggregation, fibrinogen binding, PAC-1 binding, and P-selectin antibody binding studies showed that platelet GPIIb-IIIa activation and alpha-granule release were enhanced at hypothermic temperatures. Thus hypothermia appears to increase the ability of platelets to respond to activating stimuli. The coagulopathy associated with hypothermia is not likely to be the result of an intrinsic defect in platelet function.