Perfluorocarbons cause thrombocytopenia, changes in RBC morphology and death in a baboon model of systemic inflammation.

A perfluorocarbon (PFC) investigated for treatment of traumatic brain injury (TBI) delivers oxygen to support brain function, but causes transient thrombocytopenia. TBI can cause acute inflammation with resulting thrombocytopenia; an interaction between the PFC effects and TBI inflammation might exacerbate thrombocytopenia. Therefore, PFC effects on platelet (PLT) function and hemostasis in a lipopolysaccharide (LPS) model of inflammation in the baboon were studied. Animals were randomized to receive saline ±LPS, and ± one of two doses of PFC. PLT count, transmission electron microscopy, and microparticle populations were quantified at baseline (BL) and at 2, 24, 48, 72, and 96 hours; hemostatic parameters for aggregometry and for blood clotting were measured at baseline (BL) and days 3 and 4. Injection of vehicle and LPS caused thrombocytopenia within hours; PFCs caused delayed thrombocytopenia beginning 48 hours post-infusion. LPS+PFC produced a more prolonged PLT decline and decreased clot strength. LPS+PFC increased ADP-stimulated aggregation, but PFC alone did not. Microparticle abundance was greatest in the LPS+PFC groups. LPS+PFC caused diffuse microvascular hemorrhage and death in 2 of 5 baboons in the low dose LPS-PFC group and 2 of 2 in the high dose LPS-PFC group. Necropsy and histology suggested death was caused by shock associated with hemorrhage in multiple organs. Abnormal morphology of platelets and red blood cells were notable for PFC inclusions. In summary, PFC infusion caused clinically significant thrombocytopenia and exacerbated LPS-induced platelet activation. The interaction between these effects resulted in decreased hemostatic capacity, diffuse bleeding, shock and death.

Similar hemostatic responses to hypovolemia induced by hemorrhage and lower body negative pressure reveal a hyperfibrinolytic subset of non-human primates.

BACKGROUND: To study central hypovolemia in humans, lower body negative pressure (LBNP) is a recognized alternative to blood removal (HEM). While LBNP mimics the cardiovascular responses of HEM in baboons, similarities in hemostatic responses to LBNP and HEM remain unknown in this species. METHODS: Thirteen anesthetized baboons were exposed to progressive hypovolemia by HEM and, four weeks later, by LBNP. Hemostatic activity was evaluated by plasma markers, thromboelastography (TEG), flow cytometry, and platelet aggregometry at baseline (BL), during and after hypovolemia. RESULTS: BL values were indistinguishable for most parameters although platelet count, maximal clot strength (MA), protein C, thrombin anti-thrombin complex (TAT), thrombin activatable fibrinolysis inhibitor (TAFI) activity significantly differed between HEM and LBNP. Central hypovolemia induced by either method activated coagulation; TEG R-time decreased and MA increased during and after hypovolemia compared to BL. Platelets displayed activation by flow cytometry; platelet count and functional aggregometry were unchanged. TAFI activity and protein, Factors V and VIII, vWF, Proteins C and S all demonstrated hemodilution during HEM and hemoconcentration during LBNP, whereas tissue plasminogen activator (tPA), plasmin/anti-plasmin complex, and plasminogen activator inhibitor-1 did not. Fibrinolysis (TEG LY30) was unchanged by either method; however, at BL, fibrinolysis varied greatly. Post-hoc analysis separated baboons into low-lysis (LY30 <2%) or high-lysis (LY30 >2%) whose fibrinolytic state matched at both HEM and LBNP BL. In high-lysis, BL tPA and LY30 correlated strongly (r = 0.95; P<0.001), but this was absent in low-lysis. In low-lysis, BL TAFI activity and tPA correlated (r = 0.88; P<0.050), but this was absent in high-lysis. CONCLUSIONS: Central hypovolemia induced by either LBNP or HEM resulted in activation of coagulation; thus, LBNP is an adjunct to study hemorrhage-induced pro-coagulation in baboons. Furthermore, this study revealed a subset of baboons with baseline hyperfibrinolysis, which was strongly coupled to tPA and uncoupled from TAFI activity.

Is Skin the Most Allogenic Tissue in Vascularized Composite Allotransplantation and a Valid Monitor of the Deeper Tissues?

Since the 1960s, skin has been considered to be the most allogenic tissue in humans. This tenet has remained unquestioned in the reconstructive transplant arena, which has led to skin serving as the sole monitor for early rejection in vascularized composite allotransplantation. In this article, the authors question the validity of this belief. The authors' hypothesis is that skin is not always an accurate monitor of rejection in the deep tissues, thus questioning the positive and negative predictive value of the punch biopsy for suspected vascularized composite allotransplantation rejection. A search was carried out identifying vascularized composite allotransplantation publications where the allogenicity of transplanted skin was evaluated. Eighteen publications claimed skin was found to be the most allogenic tissue in humans, justifying its use as a superior monitor for rejection. Eight publications demonstrated skin to be a poor monitor of rejection deeper to the skin. Two vascularized composite allotransplantation animal studies reported skin rejecting simultaneously with the deeper tissues. Finally, three publications discussed a skin and kidney allograft, transplanted simultaneously, indicating skin allogenicity was equivalent to the that of the kidney allograft. Much of the literature in human vascularized composite allotransplantation claims skin to be an excellent monitor of the deep tissues. The conclusion from this study is that skin does not always function as a good monitor for what could be rejecting in the deep tissues. The authors believe continued research is necessary to focus on expanding novel monitoring techniques and technologies to accurately diagnose vascularized composite allotransplantation rejection without tissue destruction.

A Flow Dynamic Rationale for Accelerated Vascularized Composite Allotransplant Rejection.

BACKGROUND: From 1996 to 2000, Diefenbeck et al. carried out six knee vascularized composite allotransplants. The allotransplants were composed of bone, soft tissue, and femoral vascular pedicle (25 to 40 cm). All rejected between 14 and 56 months. Failures were attributed to chronic rejection. In 2008, the Louisville team lost their fourth patient's hand transplant at 8 months. During the rejection workup, intraoperative findings noted a thickened arterial pedicle attributed to intimal hyperplasia with significant fibrotic perivascular tissue and a near "no-flow phenomenon." No cutaneous rejection was appreciated and failure was attributed to chronic rejection. METHODS: Data were collected from two teams, one in Germany and the other in Louisville, Kentucky. The population under study consisted of the six knee and one hand transplants. The factor of interest was the long donor arterial pedicle. The outcome measurements were transplant survival time and histopathologic results. RESULTS: There are only seven published vascularized composite allotransplant cases where a donor artery longer than 25 cm was used. This cohort represents a 100 percent accelerated failure rate. The cause of these losses remains unexplained. The donor arteries suffered from T-cell-mediated rejection and ischemia-induced media/adventitial necrosis. CONCLUSIONS: We hypothesize that the donor artery rejected at an accelerated rate because of ischemia caused by disruption of the external vasa vasorum in conjunction with intimal hyperplasia induced by T-cell-mediated rejection that led to disruption of the Windkessel effect. Loss of this effect presented as intimal hyperplasia accelerated by ischemia causing an expedited transplant failure. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Platelet and coagulation function before and after burn and smoke inhalation injury in sheep.

BACKGROUND: Smoke inhalation and burn injury remain a major source of morbidity and mortality. There is known dysregulation of hemostasis in burn patients, but either hypercoagulation or hypocoagulation states are reported. Sheep are an established animal model for studying burn pathology and provide robust data on hemostatic function at baseline and after injury. METHODS: After an IACUC-approved protocol, 15 sheep were anesthetized and subjected to a 40% full thickness burn with smoke inhalation. Blood was sampled at baseline, 1 day postinjury (early effects) and days 2, 3, and 4 (late effects) after injury. Assays at each timepoint assessed: hemostatic function by thromboelastography (TEG), platelet counts and function by flow cytometry and aggregometry, coagulation protein levels, and free hemoglobin. Data were analyzed by the Wilcoxon paired test (nonparametric) with significance set at less than 0.05. RESULTS: By 24 hours postinjury, platelet counts had dropped, whereas the percent activated platelets increased. Absolute platelet functional response to the agonist adenosine diphosphate (ADP) decreased, whereas response to collagen showed no significant difference. On a per platelet basis, ADP response was unchanged, whereas the collagen response was elevated. Prothrombin time and activated partial thromboplastin time were prolonged. TEG parameters decreased significantly from baseline. Fibrinogen and factor V were trending up; coagulation proteins ATIII, factors IX and X were decreased.Late effects were followed in six animals. At day 4, platelet counts remained depressed compared with baseline with a nadir at day 2; responses to agonist on a per platelet basis remained the same for ADP and stayed elevated for collagen. Platelets continued to have elevated activation levels. Fibrinogen and factor V remained significantly elevated, whereas TEG parameters and prothrombin time, factors IX and X returned to near baseline levels. CONCLUSION: Coagulation parameters and hemostasis are dysregulated in sheep after smoke inhalation and burn. By 24 hours, sheep were hypocoagulable and subsequently became hypercoagulable by day 4. These results suggest a three-stage coagulopathy in burn injuries with a known early consumptive hypercoagulable state which is followed by a relatively hypocoagulable state with increased bleeding risk and then a return to a relatively unknown hypercoagulability with increased susceptibility to thrombotic disorders.

Traumatic Hemothorax Blood Contains Elevated Levels of Microparticles that are Prothrombotic but Inhibit Platelet Aggregation.

OBJECTIVES: Autotransfusion of shed blood from traumatic hemothorax is an attractive option for resuscitation of trauma patients in austere environments. However, previous analyses revealed that shed hemothorax (HX) blood is defibrinated, thrombocytopenic, and contains elevated levels of D-dimer. Mixing studies with normal pooled plasma demonstrated hypercoagulability, evoking concern for potentiation of acute traumatic coagulopathy. We hypothesized that induction of coagulopathic changes by shed HX blood may be due to increases in cellular microparticles (MP) and that these may also affect recipient platelet function. METHODS: Shed HX blood was obtained from 17 adult trauma patients under an Institutional Review Board approved prospective observational protocol. Blood samples were collected every hour up to 4 h after thoracostomy tube placement. The corresponding plasma was isolated and frozen for analysis. The effects of shed HX frozen plasma (HFP) and isolated HX microparticles (HMP) on coagulation and platelet function were assessed through mixing studies with platelet-rich plasma at various dilutions followed by analysis with thromboelastometry (ROTEM), platelet aggregometry (Multiplate), enzyme-linked immunosorbent assays, and flow cytometry. Furthermore, HFP was assessed for von Willebrand factor antigen levels and multimer content, and plasma-free hemoglobin. RESULTS: ROTEM analysis demonstrated that diluted HFP and isolated HMP samples decreased clotting time, clotting formation time, and increased α angle, irrespective of sample concentrations, when compared with diluted control plasma. Isolated HMP inhibited platelet aggregation in response to adenosine diphosphate, arachidonic acid, and collagen. HFP contained elevated levels of fibrin-degradation products and tissue factor compared with control fresh frozen plasma samples. MP concentrations in HFP were significantly increased and enriched in events positive for phosphatidylserine, tissue factor, CD235, CD45, CD41a, and CD14. von Willebrand factor (vWF) multimer analysis revealed significant loss of high molecular weight multimers in HFP samples. Plasma-free hemoglobin levels were 8-fold higher in HFP compared with fresh frozen plasma. CONCLUSION: HFP induces plasma hypercoagulability that is likely related to increased tissue factor and phosphatidylserine expression originating from cell-derived MP. In contrast, platelet dysfunction is induced by HMP, potentially aggravated by depletion of high molecular weight multimers of vWF. Thus, autologous transfusion of shed traumatic hemothorax blood may induce a range of undesirable effects in patients with acute traumatic coagulopathy.

Low-Dose Heparin Anticoagulation During Extracorporeal Life Support for Acute Respiratory Distress Syndrome in Conscious Sheep.

BACKGROUND: Over 32% of burned battlefield causalities develop trauma-induced hypoxic respiratory failure, also known as acute respiratory distress syndrome (ARDS). Recently, 9 out of 10 US combat soldiers' survived life-threatening trauma-induced ARDS supported with extracorporeal membrane oxygenation (ECMO), a portable form of cardiopulmonary bypass. Unfortunately, the size, incidence of coagulation complications, and the need for systematic anticoagulation for traditional ECMO devices have prevented widespread use of this lifesaving technology. Therefore, a compact, mobile, ECMO system using minimal anticoagulation may be the solution to reduce ARDS in critically ill military and civilian patients. METHODS: We conducted a prospective cohort laboratory investigation to evaluate the coagulation function in an ovine model of oleic acid induced ARDS supported with veno-venous ECMO. The experimental design approximated the time needed to transport from a battlefield setting to an advanced facility and compared bolus versus standard heparin anticoagulation therapy. RESULTS: Comprehensive coagulation and hemostasis assays did not show any difference because of ECMO support over 10 h between the two groups but did show changes because of injury. Platelet count and function did decrease with support on ECMO, but there was no significant bleeding or clot formation during the entire experiment. CONCLUSIONS: A bolus heparin injection is sufficient to maintain ECMO support for up to 10 h in an ovine model of ARDS. With a reduced need for systematic anticoagulation, ECMO use for battlefield trauma could reduce significant morbidity and mortality from ventilator-induced lung injury and ARDS. Future studies will investigate the mechanisms and therapies to support patients for longer periods on ECMO without coagulation complications. LEVEL OF EVIDENCE: V--therapeutic animal experiment.

Severe Acinetobacter baumannii sepsis is associated with elevation of pentraxin 3.

Multidrug-resistant Acinetobacter baumannii is among the most prevalent bacterial pathogens associated with trauma-related wound and bloodstream infections. Although septic shock and disseminated intravascular coagulation have been reported following fulminant A. baumannii sepsis, little is known about the protective host immune response to this pathogen. In this study, we examined the role of PTX3, a soluble pattern recognition receptor with reported antimicrobial properties and stored within neutrophil granules. PTX3 production by murine J774a.1 macrophages was assessed following challenge with A. baumannii strains ATCC 19606 and clinical isolates (CI) 77, 78, 79, 80, and 86. Interestingly, only CI strains 79, 80, and 86 induced PTX3 synthesis in murine J774a.1 macrophages, with greatest production observed following CI 79 and 86 challenge. Subsequently, C57BL/6 mice were challenged intraperitoneally with CI 77 and 79 to assess the role of PTX3 in vivo. A. baumannii strain CI 79 exhibited significantly (P < 0.0005) increased mortality, with an approximate 50% lethal dose (LD50) of 10(5) CFU, while an equivalent dose of CI 77 exhibited no mortality. Plasma leukocyte chemokines (KC, MCP-1, and RANTES) and myeloperoxidase activity were also significantly elevated following challenge with CI 79, indicating neutrophil recruitment/activation associated with significant elevation in serum PTX3 levels. Furthermore, 10-fold-greater PTX3 levels were observed in mouse serum 12 h postchallenge, comparing CI 79 to CI 77 (1,561 ng/ml versus 145 ng/ml), with concomitant severe pathology (liver and spleen) and coagulopathy. Together, these results suggest that elevation of PTX3 is associated with fulminant disease during A. baumannii sepsis.

Primary hemostatic capacity of whole blood: a comprehensive analysis of pathogen reduction and refrigeration effects over time.

BACKGROUND: Whole blood (WB) has been used in combat since World War I as it is readily available and replaces every element of shed blood. Component therapy has become standard; however, recent military successes with WB resuscitation have revived the debate regarding wider WB use. Characterization of optimal WB storage is needed. We hypothesized that refrigeration preserves WB function and that a pathogen reduction technology (PRT) based on riboflavin and ultraviolet light has no deleterious effect over 21 days of storage. STUDY DESIGN AND METHODS: WB units were stored for 21 days either at 4°C or 22°C. Half of each temperature group underwent PRT, yielding four final treatment groups (n = 8 each): CON 4 (WB at 4°C); CON 22 (WB at 22°C); PRT 4 (PRT WB at 4°C); and PRT 22 (PRT WB at 22°C). Testing was at baseline, Days 1-7, 10, 14, and 21. Assays included coagulation factors; platelet activation, aggregation, and adhesion; and thromboelastography (TEG). RESULTS: Prothrombin time (PT) and partial thromboplastin time increased over time; refrigeration attenuated the effects on PT (p ≤ 0.009). Aggregation decreased over time (p ≤ 0.001); losses were attenuated by refrigeration (p ≤ 0.001). Refrigeration preserved TEG parameters (p ≤ 0.001) and PRT 4 samples remained within normal limits throughout the study. Refrigeration in combination with PRT inhibited fibrinolysis (p ≤ 0.001) and microparticle formation (p ≤ 0.031). Cold storage increased shear-induced platelet aggregation and ristocetin-induced platelet agglutination (p ≥ 0.032), as well as GPIb-expressing platelets (p ≤ 0.009). CONCLUSION: The in vitro hemostatic function of WB is largely unaffected by PRT treatment and better preserved by cold storage over 21 days. Refrigerated PRT WB may be suitable for trauma resuscitation. Clinical studies are warranted.

TLR-dependent control of Francisella tularensis infection and host inflammatory responses.

BACKGROUND: Francisella tularensis is the causative agent of tularemia and is classified as a Category A select agent. Recent studies have implicated TLR2 as a critical element in the host protective response to F. tularensis infection, but questions remain about whether TLR2 signaling dominates the response in all circumstances and with all species of Francisella and whether F. tularensis PAMPs are predominantly recognized by TLR2/TLR1 or TLR2/TLR6. To address these questions, we have explored the role of Toll-like receptors (TLRs) in the host response to infections with F. tularensis Live Vaccine Strain (LVS) and F. tularensis subspecies (subsp.) novicida in vivo. METHODOLOGY/PRINCIPAL FINDINGS: C57BL/6 (B6) control mice and TLR- or MyD88-deficient mice were infected intranasally (i.n.) or intradermally (i.d.) with F. tularensis LVS or with F. tularensis subsp. novicida. B6 mice survived >21 days following infection with LVS by both routes and survival of TLR1(-/-), TLR4(-/-), and TLR6(-/-) mice infected i.n. with LVS was equivalent to controls. Survival of TLR2(-/-) and MyD88(-/-) mice, however, was significantly reduced compared to B6 mice, regardless of the route of infection or the subspecies of F. tularensis. TLR2(-/-) and MyD88(-/-) mice also showed increased bacterial burdens in lungs, liver, and spleen compared to controls following i.n. infection. Primary macrophages from MyD88(-/-) and TLR2(-/-) mice were significantly impaired in the ability to secrete TNF and other pro-inflammatory cytokines upon ex vivo infection with LVS. TNF expression was also impaired in vivo as demonstrated by analysis of bronchoalveolar lavage fluid and by in situ immunofluorescent staining. CONCLUSIONS/SIGNIFICANCE: We conclude from these studies that TLR2 and MyD88, but not TLR4, play critical roles in the innate immune response to F. tularensis infection regardless of the route of infection or the subspecies. Moreover, signaling through TLR2 does not depend exclusively on TLR1 or TLR6 during F. tularensis LVS infection.