Wolfgang Schobersberger

The Effect of Fibrinogen Substitution on Reversal of Dilutional Coagulopathy: An In Vitro Model

Colloids and crystalloids are usually administered as treatment for hypovolemia in severely injured patients. However, dilution of clotting factors and platelets together with impaired fibrinogen polymerization are associated with fluid therapy and may aggravate hemorrhage, thus worsening final outcome of these patients. We investigated, in an in vitro model, whether the addition of fibrinogen to diluted blood samples can reverse dilutional coagulopathy. Blood from 5 healthy male volunteers was diluted by 60% using lactated Ringers solution, 4% modified gelatin solution, or 6% hydroxyethyl starch 130/0.4, as well as the combination of lactated Ringers solution with either of the 2 colloid solutions. Thereafter, aliquots of diluted blood samples were incubated with 3 different concentrations of fibrinogen (0.75, 1.5, and 3.0 mg/mL). Measurements were performed by modified thrombelastography (ROTEM®; Pentapharm, Munich, Germany). After 60% dilution, clotting times increased, whereas clot firmness and fibrin polymerization decreased significantly. After administration of fibrinogen, clotting times decreased and clot firmness, as well as fibrin polymerization, increased in all diluted blood samples. The effect of in vitro fibrinogen substitution on ROTEM® variables was dependent on the fibrinogen dosage and the type of solution used to dilute the blood samples.

The effect of the combined administration of colloids and lactated Ringer's solution on the coagulation system: an in vitro study using thrombelastograph coagulation analysis (ROTEG.

Gelatin solutions are often given in clinical practice once the maximal dose of a median-weight hydroxyethyl starch (HES) has been reached. Colloids are usually combined with lactated Ringer’s solution (RL). Whether the combined administration of colloids and/or crystalloids affects blood coagulation is not known. We diluted blood by 20%, 40%, and 60% with RL, gelatin (Gelofusin®), 6% HES 130/0.4 (Voluven®), and 6% HES 200/0.5 (Iso-Hes®), as well as with combinations of these solutions at a ratio of 1:1 (gelatin/RL, 6% HES 130/0.4:RL, 6% HES 200/0.5:RL, 6% HES 130/0.4:gelatin, 6% HES 200/0.5:gelatin). Thereafter, blood was analyzed by using modified thrombelastograph® coagulation analysis (ROTEG®) and clotting time, clot formation time, and maximal clot firmness were determined. RL had the least effect on hemostasis. Gelatin administered alone impaired the coagulation system significantly less than each median-weight HES administered alone. We conclude that gelatin combined with 6% HES 200/0.5 or 6% HES 130/0.4 decreases hemostasis <6% HES 200/0.5 or 6% HES 130/0.4 administered alone.

Time for changing coagulation management in trauma-related massive bleeding.

Purpose of review New insights into the pathophysiology of trauma-induced coagulopathy, the increasing availability of point-of-care devices and awareness of side effects of intravenous fluids and traditional fresh frozen plasma therapy has encouraged new concepts for managing massive blood loss. Recent findings Trauma-induced coagulopathy primarily results from blood loss, hypovolemia-induced activation of the protein C system and consequent increase of the fibrinolytic potential, whereas hemodilution, localized consumption of clotting factors and platelets, hypothermia, acidosis, anemia and hypocalcemia further decrease the hemostatic potential. The widespread use of viscoelastic devices highlighted the importance of the contribution of fibrinogen to clot firmness, a precondition for cessation of bleeding. The evidence is growing that targeted therapy using coagulation factor concentrates guided by viscoelastic measurements enables effective correction of severe coagulopathy. Summary During massive blood loss, viscoelastic measurements should guide aggressive treatment of deficiency or hyperfibrinolysis or both. In addition, the impact of contributing factors should be considered and as far as possible corrected. New data underscore the importance of avoiding hypoperfusion, and the use of coagulation factor concentrates should enable more effective correction of coagulopathy.

Blunted erythropoietic response to anemia in multiply traumatized patients.

ObjectivesTo assess the relations between anemia, serum erythropoietin (EPO), iron status, and inflammatory mediators in multiply traumatized patients. DesignProspective observational study. SettingIntensive care unit. PatientsTwenty-three patients suffering from severe trauma (injury severity score ≥30). InterventionsNone. Measurements and Main Results Blood samples were collected within 12 hrs after the accident (day 1) and in the morning on days 2, 4, 6, and 9 to determine blood cell status, serum EPO, tumor necrosis factor-&agr; (TNF-&agr;), soluble tumor necrosis factor-receptor I (sTNF-rI), interleukin-1 receptor antagonist (IL1-ra), interleukin-6 (IL-6), neopterin, and iron status, respectively. Hemoglobin concentration was low at admission (mean, 10.0 g/dL; range, 6.8–12.9 g/dL) and did not increase during the observation time. Serum EPO concentration was 49.8 U/L (mean value) on day 1 and did not show significant increases thereafter. No correlation was found between EPO and hemoglobin concentrations. TNF-&agr; remained within the normal range. sTNF-rI was high at admission and increased further. IL1-ra was above the normal range. IL-6 was very high at admission and did not decrease thereafter. The initial neopterin concentration was normal, but increased until day 9. Serum iron was significantly decreased on day 2 posttrauma and remained low during the study. Serum ferritin increased steadily from day 2, reaching its maximum on day 9. In contrast, concentrations of transferrin were low from admission onward. ConclusionsMultiply traumatized patients exhibit an inadequate EPO response to low hemoglobin concentrations. Thus, anemia in severe trauma is the result of a complex network of bleeding, blunted EPO response to low hemoglobin concentrations, inflammatory mediators, and a hypoferremic state.

Tachyarrhythmias in a surgical intensive care unit: a case-controlled epidemiologic study.

Objective: Incidence, types, and factors associated with new onset tachyarrhythmias (TA) in surgical intensive care patients.¶Design: Pairwise-matched case-controlled study. Setting: Surgical intensive care unit (ICU) with nine intensive care beds. Patients: During a 1-year period, all TA patients (n = 89) were included in the study. Control patients (n = 82) without TA were matched according to age, sex, and surgical region. Methods: TA workup included: 12-lead ECG, arterial blood gas, serum electrolyte (K+, Mg2+), and serum CK/CKMB isoenzyme analysis. Pre-existing cardiovascular and pulmonary disease, cardiovascular risk factors, preoperative regular medication, and admission SAPS were recorded in all patients. A multiple organ dysfunction syndrome (MODS) score, the presence or absence of SIRS or sepsis, and hemodynamics (MAP and CVP) before onset of TA were evaluated in TA patients, while in control patients highest MODSscore, the presence or absence of SIRS or sepsis, mean hemodynamic and laboratory values calculated from highest and lowest readings during ICU stay were used for statistical comparison. Logistic regression analysis was performed to identify variables multivariately associated with TA. Results: Eighty-nine (14.8 %) of 596 patients developed TA. Atrial fibrillation was most frequent (60.7 %). Presence of SIRS or sepsis (adj. OR = 36.45; 95 % CI: 11.5–115.5), high admission SAPS (adj. OR = 1.25/point; 95 % CI: 1.08–1.44), high CVP (adj. OR = 1.27/mmHg; 95 % CI: 1.09–1.48), and low arterial oxygen tension (adj. OR = 0.97/mmHg); 95 % CI: 0.95–0.99) were found to be significant predictors for development of TA. Conclusions: In surgical patients hypoxia, high cardiac filling pressures, a greater degree of physiologic derangement at admission, and the presence of SIRS and sepsis are independent risk factors for the development of TA.

Transfusion of buffy coat-depleted blood components and risk of postoperative infection in orthopedic patients.

BACKGROUND: Allogeneic blood transfusions have been reported to increase susceptibility to postoperative infection, but the findings were inconclusive. This study was designed to investigate the effect of buffy coat‐depleted allogeneic and autologous transfusion on postoperative infection in patients undergoing orthopedic surgery.

Antifactor Xa activity in intensive care patients receiving thromboembolic prophylaxis with standard doses of enoxaparin

BACKGROUND Low-molecular-weight heparins (LMWHs) have become increasingly used to prevent thromboembolic complications in intensive care patients. Unlike in medical and surgical patients, no data on the anticoagulant effectiveness of standard LMWH dosages exist in intensive care patients. Therefore, we prospectively investigated antifactor Xa (aFXa) levels after subcutaneous administration of 40 mg of enoxaparin in 89 intensive care patients over a 24-h period. METHODS AFXa levels were measured before, 4, 12 and 24 h after subcutaneous administration of enoxaparin. Laboratory parameters including prothrombin time, activated partial thromboplastin time, antithrombin III, fibrinogen as well as platelet count were collected at same intervals. Demographics included age, sex, height, weight, body mass index, admission diagnosis, a thromboembolic risk score and a modified Goris multiple organ dysfunction score. RESULTS At 4, 12 and 24 h, 56.5%, 39.3% and 12.6% of the study patients were within recommended antithrombotic aFXa levels (0.1-0.3 U ml(-1)). Presence of multiple organ dysfunction as well as high body weight were significantly correlated with low aFXa levels. CONCLUSION European standard dosages of 40 mg of enoxaparin once daily proved to be ineffective in achieving recommended antithrombotic aFXa levels in intensive care patients. This was most pronounced in patients with high body weight and presence of multiple organ dysfunction.

Induction of inducible nitric oxide synthase expression by neopterin in vascular smooth muscle cells

The pteridine compounds neopterin and 7,8‐dihydroneopterin serve as valuable indicators for the stimulation of the cellular immune system. Whether they exhibit distinct biochemical functions in the immunological process is at present under discussion. We show that neopterin, but not 7,8‐dihydroneopterin, is a stimulus for iNOS gene expression in rat vascular smooth muscle cells in vitro. At a concentration of 20 μM, neopterin leads to an iNOS mRNA expression of 2.5 amol iNOS cDNA/μg total RNA. When cells were coincubated with 20 μM neopterin and 5 μg/ml lipopolysaccharide derived from Escherichia coli, at least an additive effect on iNOS mRNA expression could be detected (iNOS cDNA concentration was 5.0 amol/μg total RNA). We speculate that neopterin enhances the macrophage‐induced extracellular toxicity. This might be of relevance in situations associated with excessive release of cytokines, neopterin, and nitric oxide, as observed in septic shock.

Migration of human monocytes in response to procalcitonin.

ObjectiveCirculating serum levels of procalcitonin rise significantly during bacterial infection. Because calcitonin is known to be a monocyte chemoattractant, we investigated whether procalcitonin, a prohormone of calcitonin, also affects leukocyte migration. DesignProspective, controlled in vitro study. SettingUniversity research laboratories. InterventionsForearm venous blood polymorphonuclear neutrophils and monocytes were isolated from healthy human donors. Cell migration was assessed in a blindwell chemotaxis chamber. The distance of migration into filter micropores was measured. To biochemically confirm functional data on cell migration, effects of procalcitonin on cellular levels of cyclic adenosine monophosphate were measured by high-performance liquid chromatography. Measurements and Main ResultsBoth procalcitonin and calcitonin elicited dose-dependent migration of monocytes at concentrations from the femtomolar to the micromolar range. Neutrophils did not migrate toward procalcitonin or calcitonin, nor was their oxygen free radical release affected as measured fluorimetrically. Checkerboard analysis of monocyte locomotion revealed procalcitonin-induced migration as true chemotaxis. Pretreatment of monocytes with procalcitonin or calcitonin rapidly deactivated their migratory response to formyl-Met-Leu-Phe, and both also induced homologous deactivation of migration. Procalcitonin elevated levels of cyclic adenosine monophosphate in monocytes. ConclusionsIn vitro procalcitonin is a monocyte chemoattractant that deactivates chemotaxis in the presence of additional inflammatory mediators. Procalcitonin stimulates cyclic adenosine monophosphate production in monocytes, suggesting that its action may be specific and comparable with calcitonin, which exerts similar functions.

Neopterin activates transcription factor nuclear factor-κB in vascular smooth muscle cells

We have previously shown that the pteridine compound neopterin stimulates inducible nitric oxide synthase (iNOS) gene expression in vascular smooth muscle cells in vitro. The mechanisms whereby neopterin exhibits these effects remained unclear. The present study demonstrates that neopterin induces the translocation of the transcription factor nuclear factor‐κB (NF‐κB) to the nucleus. Pretreatment of cells with the antioxidant pyrrolidine dithiocarbamate completely suppressed the effects of neopterin on NF‐κB activation, iNOS gene expression, and nitric oxide release. From these data we conclude that neopterin activates the translocation of NF‐κB subunits to the nucleus by modulating the intracellular redox state. This is one possible explanation for the impact of neopterin on iNOS gene expression.