A European consensus statement on the use of four-factor prothrombin complex concentrate for cardiac and non-cardiac surgical patients.

Modern four-factor prothrombin complex concentrate was designed originally for rapid targeted replacement of the coagulation factors II, VII, IX and X. Dosing strategies for the approved indication of vitamin K antagonist-related bleeding vary greatly. They include INR and bodyweight-related protocols as well as fixed dose regimens. Particularly in the massively bleeding trauma and cardiac surgery patient, four-factor prothrombin complex concentrate is used increasingly for haemostatic resuscitation. Members of the Transfusion and Haemostasis Subcommittee of the European Association of Cardiothoracic Anaesthesiology performed a systematic literature review on four-factor prothrombin complex concentrate. The available evidence has been summarised for dosing, efficacy, drug safety and monitoring strategies in different scenarios. Whereas there is evidence for the efficacy of four-factor prothrombin concentrate for a variety of bleeding scenarios, convincing safety data are clearly missing. In the massively bleeding patient with coagulopathy, our group recommends the administration of an initial bolus of 25 IU.kg-1 . This applies for: the acute reversal of vitamin K antagonist therapy; haemostatic resuscitation, particularly in trauma; and the reversal of direct oral anticoagulants when no specific antidote is available. In patients with a high risk for thromboembolic complications, e.g. cardiac surgery, the administration of an initial half-dose bolus (12.5 IU.kg-1 ) should be considered. A second bolus may be indicated if coagulopathy and microvascular bleeding persists and other reasons for bleeding are largely ruled out. Tissue-factor-activated, factor VII-dependent and heparin insensitive point-of-care tests may be used for peri-operative monitoring and guiding of prothrombin complex concentrate therapy.

The role of fibrinogen and fibrinogen concentrate in cardiac surgery: an international consensus statement from the Haemostasis and Transfusion Scientific Subcommittee of the European Association of Cardiothoracic Anaesthesiology.

To date, data regarding the efficacy and safety of administering fibrinogen concentrate in cardiac surgery are limited. Studies are limited by their low sample size and large heterogeneity with regard to the patient population, by the timing of fibrinogen concentrate administration, and by the definition of transfusion trigger and target levels. Assessment of fibrinogen activity using viscoelastic point-of-care testing shortly before or after weaning from cardiopulmonary bypass in patients and procedures with a high risk of bleeding appears to be a rational strategy. In contrast, the use of Clauss fibrinogen test for determination of plasma fibrinogen level can no longer be recommended without restrictions due to its long turnaround time, high inter-assay variability and interference with high heparin levels and fibrin degradation products. Administration of fibrinogen concentrate for maintaining physiological fibrinogen activity in the case of microvascular post-cardiopulmonary bypass bleeding appears to be indicated. The available evidence does not suggest aiming for supranormal levels, however. Use of cryoprecipitate as an alternative to fibrinogen concentrate might be considered to increase plasma fibrinogen levels. Although conclusive evidence is lacking, fibrinogen concentrate does not seem to increase adverse outcomes (i.e., thromboembolic events). Large prospective multi-centre studies are needed to better define the optimal perioperative monitoring tool, transfusion trigger and target levels for fibrinogen replacement in cardiac surgery.

Fibrinogen supplementation after cardiac surgery: insights from the Zero-Plasma trial (ZEPLAST).

BACKGROUND: Fibrinogen supplementation has been proposed both to prevent and treat postoperative bleeding in cardiac surgery. The optimal fibrinogen concentration trigger and target values and the fibrinogen concentrate dose required remain uncertain. This subanalysis of data from the Zero-Plasma Trial (ZEPLAST) assessed target fibrinogen values and the corresponding fibrinogen concentrate dose for supplementation. METHODS: We performed a post hoc analysis of 116 subjects included in the randomized, placebo-controlled ZEPLAST trail. Data considered were fibrin-based thromboelastometry (FIBTEM) maximum clot firmness (MCF) determined by whole-blood thromboelastometry (ROTEM) before and after placebo or fibrinogen concentrate, Clauss fibrinogen concentration after placebo or fibrinogen concentrate, postoperative bleeding and severe bleeding (SB). The association between FIBTEM MCF and Clauss fibrinogen concentration was tested with linear regression analyses. The predictive value for SB of FIBTEM MCF and Clauss fibrinogen concentration was tested with receiver operating characteristic analyses. RESULTS: There was a good association between FIBTEM MCF and Clauss fibrinogen concentration in the baseline study population (r(2) = 0.66), which worsened in fibrinogen-supplemented subjects. Both FIBTEM MCF and Clauss fibrinogen concentration yielded a good discriminative power for SB (area under the curve 0.721 and 0.767, respectively). The negative predictive value for SB was 100% for a Clauss fibrinogen concentration of 287 mg dl(-1) and 98% for an FIBTEM MCF of 14 mm. Based on these newly defined target values, the dose of fibrinogen concentrate needed would be 3 g lower than the dose used in ZEPLAST. CONCLUSIONS: A dose of fibrinogen concentrate rarely exceeding 2 g might be sufficient to prevent bleeding in cardiac surgery.

Microcirculatory changes in children undergoing cardiac surgery: a prospective observational study.

BACKGROUND: The effects of cardiac surgery on the microcirculation of children are unknown. The aim of this study was to assess the microcirculatory changes in children undergoing surgery for correction of congenital heart disease. METHODS: We used a videomicroscope (Sidestream Dark Field, SDF) in a convenience sample of 24 children

Desmopressin after cardiac surgery in bleeding patients. A multicenter randomized trial.

BACKGROUND: Previous studies showed that desmopressin decreases post-operative blood loss in patients undergoing cardiac surgery. These studies were small and never studied the effect of desmopressin in patients with active bleeding. Objective of the study was to determine whether desmopressin reduces red blood cells transfusion requirements in patients with active bleeding after cardiac surgery who had been pre-treated with tranexamic acid. METHODS: This multicenter, randomized, double-blind, placebo-controlled, parallel-group study randomized elective patients with bleeding after cardiac surgery despite pre-treatment with tranexamic acid, to receive placebo (saline solution) or a single administration of desmopressin (0.3 µg/kg in saline solution). The primary endpoint was the number of patients requiring red blood cells transfusion after randomization and during hospital stay. Secondary end points were: blood loss from chest tubes during the first 24 h after study drug administration, hours of mechanical ventilation, intensive care unit stay, and in-hospital mortality. RESULTS: The study was interrupted after inclusion of 67% of the planned patients for futility. The number of patients requiring red blood cells transfusion after randomization was 37/68 (54%) in desmopressin group and 33/67 (49%) in placebo group (P = 0.34) with no difference in blood loss: 575 (interquartile 422-770) ml in desmopressin group and 590 (476-1013) ml in placebo group (P = 0.42), mechanical ventilation, intensive care unit stay or mortality. CONCLUSIONS: This multicenter randomized trial demonstrated that, in patients pre-treated with tranexamic acid, desmopressin should not be expected to improve treatment of patients who experience bleeding after cardiac surgery.

Pre-operative fibrinogen supplementation in cardiac surgery patients: an evaluation of different trigger values.

BACKGROUND: Pre-operative fibrinogen levels are negatively associated with postoperative bleeding in cardiac surgery patients. The guidelines of the European Society of Anaesthesiology consider the possibility of a prophylactic pre-operative supplementation in patients with fibrinogen levels<`3.8 g/l. The present study is a reanalysis of published data aimed to define the diagnostic accuracy of different values of pre-operative fibrinogen levels in predicting severe post-operative bleeding. METHODS: Data were retrieved for 2154 patients in four different studies. Severe bleeding (SB) was defined as a post-operative chest drain output>1 l/12 h. Diagnostic accuracy for prediction of SB was tested at three cutoff values of pre-operative fibrinogen (2.5 g/l, 3.0 g/l, and 3.8 g/l). RESULTS: At all the three cutoff values, pre-operative fibrinogen levels had an excellent negative predictive value, ranging from 86% to 100%. Conversely, the positive predictive value was poor at all the cutoff levels: 12% (3.8 g/l), 14% (3.0 g/l), and 19% (2.5 g/l). Overall, the accuracy of pre-operative fibrinogen levels for the prediction of SB was poor. A strategy based on pre-operative fibrinogen supplementation would lead to inappropriate treatment in > 80% of the treated patients. Overall, a trigger value of 3.8 g/l would result in an inappropriate treatment in 52% of the patients, of 3.0 g/l in 20% of the patients, and of 2.5 g/l in 4% of the patients. CONCLUSION: Correction of pre-operative fibrinogen levels below 3.8 g/l would lead to an excessive rate of inappropriate interventions. Values below 2.5 g/l could be considered.

Effect of preoperative P2Y12 and thrombin platelet receptor inhibition on bleeding after cardiac surgery.

BACKGROUND: Drugs that act on the platelet P2Y12 receptor are responsible for postoperative bleeding in cardiac surgery. However, protease-activated receptor (PAR) that reacts to thrombin stimulation might still be active in patients treated with P2Y12 inhibitors. Preoperative platelet function testing could possibly guide the timing of surgery. We investigated the association between P2Y12 receptor and PAR inhibition and bleeding after cardiac surgery. METHODS: A retrospective cohort study of 361 patients undergoing cardiac surgery and treated with P2Y12 anti-platelet agents was undertaken. All patients received a preoperative multiplate electrode aggregometry testing of platelet P2Y12 receptor activity (ADPtest) and PAR reactivity with thrombin receptor-activating peptide (TRAP) stimulation. ADPtest and TRAPtest data measured before surgery were analysed for association with postoperative bleeding (ml per 12 h) and severe postoperative bleeding. RESULTS: Both the ADPtest and the TRAPtest were significantly (P=0.001) associated with postoperative bleeding. A threshold of 22 U for the ADPtest yielded a negative predictive value (NPV) of 94% and a positive predictive value (PPV) of 20%, and a threshold of 75 U for the TRAPtest yielded an NPV of 95% and a PPV of 23%. In the subgroup of patients with ADPtest <22 U, TRAPtest ≥75 U was not associated with severe bleeding (NPV of 100% and PPV of 37%). CONCLUSIONS: In patients taking P2Y12 receptor inhibitors, residual platelet reactivity to thrombin stimulation limits the risk of severe postoperative bleeding.

Transfusions during cardiopulmonary bypass: better when triggered by venous oxygen saturation and oxygen extraction rate.

During cardiopulmonary bypass (CPB), red blood cell transfusions may be required to correct dilutional anemia. The decision-making process for transfusions is usually based on the level of hemoglobin.This study investigates the hypothesis that oxygen-derived variables (mixed venous oxygen saturation, SvO(2), and oxygen extraction rate, O(2)ER) may be more reliable predictors of the efficacy of the transfusion. Thirty-six patients for 41 transfusion episodes during CPB were retrospectively analyzed. For each patient, oxygen-derived variables, including SvO(2) and O(2)ER, were measured before and after the transfusion. No changes in pump flow were allowed between the two measurements. The efficacy of transfusion was defined as an increase in SvO(2) of at least 5%. We identified 11 transfusion episodes leading to an efficacious SvO (2) increase. Factors associated with the efficacy of the transfusion were a low SvO(2) and a high O(2)ER. No association was found with hemoglobin values, unless for a trend for efficacy of transfusion in patients with very low (<6 g/dL) hemoglobin values. Cut-off values of 68% for SvO(2) and 39% for O(2)ER were predictive for the efficacy of red blood cell transfusions, with a high accuracy (c-statistics 0.856 and 0.848, respectively) and negative and positive predictive values exceeding 82%. In conclusion, SvO(2) and O(2)ER are better than the hemoglobin value for guiding the decision-making process of red blood cell transfusions to correct hemodilutional anemia during CPB.

[Comparative characteristics of the biological properties of small ruminant lentiviruses].

The infections caused by small ruminant lentiviruses include diseases, such as Maedi-Visna (MV) and caprine arthritis-encephalitis (CAE). According to phylogenetic findings and their common origination, small ruminant lentiviruses were divided into Groups A, B, C, D, and E. Cultivation of the lentiviruses displayed the cytopathic effect of the CAE virus strain 75 G-63 in the primary culture of goatling synovial membrane cells, which was shown by monolayer destruction and polynuclear cell formation; this was uncharacteristic for M-88, K-796, and Tverskoy strains. A high homology was found for the Tverskoy strain with Group B small ruminant lentiviruses and the M-88 and K-796 strains with their Group A.

[On the role of some conserved and nonconserved amino acid residues in transition state and in intermediate of apomyoglobin folding].

The effect of some amino acid residues in A, B, G, and H helices on the folding nucleus and folding intermediate state formation was estimated. For four apomyoglobin mutant forms with point replacements of hydrophobic amino acid residues by Ala, the influence of the substitutions on the stability of native (N) protein and its folding intermediate state (I) was studied, as well as on the protein folding/unfolding rates. Equilibrium and kinetic studies on mutant proteins over a wide range of urea concentrations have shown that the protein native state was strongly destabilized in comparison with that of the wild type protein. At the same time, stability of the intermediate state changed insignificantly. It was shown that amino acid residues of A, G, and H helices make a small contribution to apomyoglobin folding nucleus stabilization in the rate-limiting I reversible N transition, which occurred after the intermediate state was formed. But the amino acid residue of B-helix was very important for the folding nucleus stabilization in the transition state upon the I reversible N transition.

[Equilibrium unfolding of mutant apomyoglobins with substitutions of conserved nonfunctional residues by alanine].

The problems of protein aggregation and protein misfolding in the cell are connected with the appearance of many genetic diseases. Both processes can be a consequence of substitutions of certain amino acid residues in proteins. The substitutions can influence the protein stability and protein folding rates in both the intermediate and the native states. We have studied equilibrium urea unfolding of mutant forms of apomyoglobin with substitutions of conserved nonfunctional residues by Ala to estimate their influence on protein stability. These residues include Val10, Trp14, Ilel11, Leu115, Met131 and Leu135. Conformational transitions were monitored by intrinsic Trp fluorescence and by circular dichroism spectra in the far UV region. Free energy changes upon the transition from the native to intermediate state and from the intermediate to unfolded state were determined. It was shown that all substitutions used lead to an appreciable decrease of the apomyoglobin native state stability, whereas the stability of the intermediate state is affected substantially smaller.

[Investigation of folding/unfolding kinetics of apomyoglobin].

Apomyoglobin kinetic and equilibrium unfolding and folding processes were studied at pH 6.2, 11 degrees C by stopped-flow tryptophan fluorescence. There are two distinct consecutive processes in apomyoglobin folding process, namely, the protein fast transition between the unfolded (U) and an intermediate (I) states (U <----> I) and slow transition between the intermediate and the native (N) states (I <----> N). Accumulation of the intermediate state was observed in the wide range of urea concentrations. The presence of the intermediate state was shown even beyond the middle transition on the unfolding limb. The dependence of observed folding/unfolding rates on urea concentration (chevron plot) was obtained. The shape of this dependence was compared with that of two-state proteins, folding from the U to N state.

[Investigation of apomyoglobin stability depending on urea and temperature at two different pH values].

Equilibrium unfolding of apomyoglobin by urea was investigated in the temperature range from 5 to 25 degrees C at two pH values. The thermodynamic parameters of the apomyoglobin native-unfolded state transition were determined. Conformational changes in the protein structure were monitored by tryptophan fluorescence and far UV circular dichroism. Apomyoglobin preserves its native conformation at pH 5.7 and 6.2 in the temperature range used. It was shown that the apomyoglobin stability and its unfolding cooperativity are substantially lower at 5 degrees C than at other temperatures. This fact should be taken in account at the investigation of apomyoglobin.

Moderate-degree acidosis is an independent determinant of postoperative bleeding in cardiac surgery.

BACKGROUND: Acidosis is a well-known factor leading to coagulopathy. It has been widely explored as a risk factor for severe bleeding in trauma patients. However, no information with respect to acidosis as a determinant of postoperative bleeding in cardiac surgery patients exists. The aim of this study was to investigate the role of acidosis and hyperlactatemia (HL) in determining postoperative bleeding and need for surgical revision in cardiac surgery patients. METHODS: We carried out a retrospective analysis on 4521 patients receiving cardiac operations in two institutions. For each patient the preoperative data and operative profile was available. Arterial blood gas analysis data at the arrival in the intensive care unit were analyzed to investigate the association between acidosis (pH<7.35), HL (>4.0 mMol/L) and postoperative bleeding and surgical revision rate. RESULTS: After correction for the potential confounders, both acidosis (P=0.001) and HL (P=0.001) were significantly associated with the amount of postoperative bleeding. HL was an independent risk factor for postoperative bleeding even in absence of acidosis. Overall, surgical revision rate was 5.6% in patients with HL and no acidosis; 7.7% in patients with acidosis and HL, and 7.2% in patients with acidosis and no HL. All these values are significantly (P=0.001) higher than the ones in patients without acidosis/HL (2%). CONCLUSIONS: Even a moderate degree of postoperative acidosis is associated with a greater postoperative bleeding and surgical revision rate in cardiac surgery patients. Correction of acidosis with bicarbonate does not lead to an improvement of the postoperative bleeding asset.

[Synthesis of amphiphilic photochromic benzo-15(18)-crown-5(6)-ethers and their properties in monolayers]. / Sintez amfifil'nykh fotokhromnykh benzo-15(18)-kraun-5(6)-éfirov i ikh issledovaniie v monosloiakh.

New amphiphilic photochromic benzo-15(18)-crown-5(6) ethers (APC) differing in the position of the octadecyl substituent and the size of the crown cavity were synthesized. The compounds form stable monolayers in the air/water and air/alkaline metal salt solution interfaces. The results of the pressure isotherm measurements, atomic force microscopy (AFM), and electronic spectroscopy show that the structure of the monolayers formed depends on the structure of the parent APC and the nature of the cation in salt solutions. The area per molecule of APC in the monolayer (specific area) is the smallest on the water surface and increases by 20-40% on the aqueous subphase surface with an increasing concentration of salts therein to indicate the formation of APC complexes with the metal cations. When the hydrophobic aliphatic substituent is displaced from position 3 to position 5 of the benzothiazole ring, the specific area on the surface of water and subphases decreases twofold, which indicates the compactization of the monolayer on this modification. A reversible E-Z-photoisomerization of APC was found in the monolayers formed in the salt solution/air interface. The features of the reaction are defined by the specific organization of the amphiphilic molecules in the monolayer and by the nature of the cation.

Fibrinogen measurement in cardiac surgery with cardiopulmonary bypass: analysis of repeatability and agreement of Clauss method within and between six different laboratories.

Plasma fibrinogen concentration is important for coagulopathy assessment, and is most commonly measured using the Clauss method. Several factors, including device type and reagent, have been shown to affect results. The study objective was to evaluate performance and repeatability of the Clauss method and to assess differences between measurements performed during and after cardiopulmonary bypass (CPB), by testing plasma samples from patients undergoing cardiac surgery with CPB. Samples were collected from 30 patients before surgery, approximately 20 minutes before weaning from CPB, and 5 minutes after CPB and protamine. Fibrinogen concentration was determined using the Clauss method at six quality-controlled specialised laboratories, according to accredited standard operating procedures. Regarding within-centre agreement for Clauss measurement, mean differences between duplicate measurements were between 0.00 g/l and 0.15 g/l, with intervals for 95% limits of agreement for mean Bland-Altman differences up to 1.3 g/l. Regarding between-centre agreement, some mean differences between pairs of centres were above 0.5 g/l. Differences of up to ~2 g/l were observed with individual samples. Increased variability was observed between centres, with inter-class correlation values below 0.5 suggesting only fair agreement. There were no significant differences in fibrinogen concentration before weaning from CPB and after CPB for most centres and methods. In conclusion, considerable differences exist between Clauss-based plasma fibrinogen measured using different detection methods. Nevertheless, the similarity between measurements shortly before weaning from CPB and after CPB within centres suggests that on-pump measurements could provide an early estimation of fibrinogen deficit after CPB and thus guidance for haemostatic therapy.

A prospective pilot study of platelet function and its relationship with postoperative bleeding in pediatric cardiac surgery.

BACKGROUND: Postoperative bleeding is a major problem in pediatric cardiac surgery with cardiopulmonary bypass (CPB). It recognizes a multifactorial cause, inclusive of coagulation factors consumption, hyperfibrinolysis, incomplete heparin reversal, and platelet consumption. Limited information on platelet function is available. This pilot study investigates platelet function changes in pediatric cardiac operations and their relationship with postoperative bleeding. METHODS: A cohort of 22 patients aged four years or less were prospectively analyzed. Besides the usual coagulation tests, they were studied for platelet function at four points in time: preoperative, arrival in the intensive care unit, first and second postoperative day. Platelet function was measured with multiple electrode aggregometry TRAP-test. RESULTS: After the cardiac operation there was a non-significant decrease in platelet function, with 36% of the patients demonstrating increased aggregability. Platelet count demonstrated a significant (P=0.001) decrease related to the CPB duration. The International Normalized Ratio (INR) was significantly (P=0.001) increased after the operation. Postoperative bleeding was associated with the degree of thrombocytopenia (P=0.014), the increase in INR (P=0.001), and the prolongation of the activated partial thromboplastin time (P=0.002). CONCLUSION: In this pilot study, platelet function in pediatric patients undergoing cardiac surgery demonstrates a variable pattern and no association with postoperative bleeding. Confounding factors like age and cyanosis should be addressed with larger patient populations.

pH-induced equilibrium unfolding of apomyoglobin: substitutions at conserved Trp14 and Met131 and non-conserved Val17 positions.

A number of residues in globins family are well conserved but are not directly involved in the primary oxygen-carrying function of these proteins. A possible role for these conserved, non-functional residues has been suggested in promoting a rapid and correct folding process to the native tertiary structure. To test this hypothesis, we have studied pH-induced equilibrium unfolding of mutant apomyoglobins with substitutions of the conserved residues Trp14 and Met131, which are not involved in the function of myoglobin, by various amino acids. This allowed estimating their impact on the stability of various conformational states of the proteins and selecting conditions for a folding kinetics study. The results obtained from circular dichroism, tryptophan fluorescence, and differential scanning microcalorimetry for these mutant proteins were compared with those for the wild type protein and for a mutant with the non-conserved Val17 substituted by Ala. In the native folded state, all of the mutant apoproteins have a compact globular structure, but are destabilized in comparison to the wild type protein. The pH-induced denaturation of the mutant proteins occurs through the formation of a molten globule-like intermediate similar to that of the wild type protein. Thermodynamic parameters for all of the proteins were calculated using the three state model. Stability of equilibrium intermediates at pH ~4.0 was shown to be slightly affected by the mutations. Thus, all of the above substitutions influence the stability of the native state of these proteins. The cooperativity of conformational transitions and the exposed to solvent protein surface were also changed, but not for the substitution at Val17.