Fariba Baghaei

Effects of the oral, direct factor Xa inhibitor rivaroxaban on commonly used coagulation assays.

Summary.  Introduction: Rivaroxaban is an oral direct factor Xa inhibitor developed for prophylaxis and treatment of thromboembolic disorders. Laboratory monitoring is not necessary but the dose‐dependent effects on common reagents and assay procedures are largely unknown. Objectives: To investigate the effect of rivaroxaban on commonly used coagulation assays. Materials and Methods: Rivaroxaban was added to plasma from healthy subjects in the concentration range 0–1000 μg L−1 and analyzed using different reagents for activated partial thromboplastin time (APTT), prothrombin time (PT), antithrombin, fibrinogen and activated protein C (APC) resistance assays. Results: At an expected peak concentration of rivaroxaban in clinical use, the APTTs were almost invariably prolonged but at lower concentrations the effect was weak. The concentration needed to double the APTT varied between 389 ± 106 and 617 ± 149 μg L−1 for different reagents. The PT assays showed a marked degree of difference. In general, the Quick PT type assays were more sensitive compared with the Owren type PT assays. The results from antithrombin assays were dependent on the type of reagent, with the Xa‐based assay being sensitive for rivaroxaban with an estimated increase of 0.09 IU mL−1 per 100 μg L−1 rivaroxaban. There were only minor effects on fibrinogen assays based on thrombin reagents. The APTT‐based assay for APC resistance is affected in a dose‐dependent manner whereas an assay based on the activation of coagulation at the prothrombinase level was unaffected. Conclusions: Different assays, and even different reagents within an assay group, display variable effects by therapeutic concentrations of rivaroxaban.

Effects of the oral, direct thrombin inhibitor dabigatran on five common coagulation assays

Dabigatran is an oral, reversible thrombin inhibitor that has shown promising results in large clinical trials. Laboratory monitoring is not needed but the effects on common coagulation assays are incompletely known. Dabigatran was added to plasma from healthy subjects in the concentration range 0-1,000 μg/l and analysed using several reagents for activated thromboplastin time (APTT), prothrombin time (PT), fibrinogen, antithrombin, and activated protein C resistance. Typical trough concentrations are about 50 μg/l, peak concentrations 100-300 μg/l. At 100 μg/l all APTT-results were prolonged. The concentration required to double APTT ranged between 227 and 286 μg/l, the responses for all five reagents were similar. PT-reagents were much less affected with almost no samples above INR 1.2 at 100 μg/l. The effect was sample dilution dependent with PT Quick type more sensitive than PT Owren type methods. If a patient on dabigatran has prolonged APTT, >90 seconds, and Quick PT INR>2 or Owren PT INR>1.5 over-dosing or accumulation of dabigatran should be considered. Two of four fibrinogen reagents underestimated the fibrinogen concentration considerably at expected peak concentration. Methods based on inhibition of thrombin over-estimated the antithrombin concentration, but not Xa-based. The APC-resistance methods over-estimated the APC-ratio, which may lead to miss-classification of factor V Leiden patients as being normal. Different coagulation assays, and even different reagents within an assay group, display variable effects at therapeutic concentrations of dabigatran. Some of these assay variations are of clinical importance, thus knowledge is needed for a correct interpretation of results.

Prophylactic fibrinogen infusion reduces bleeding after coronary artery bypass surgery - A prospective randomised pilot study

It has been suggested that preoperative fibrinogen plasma concentration is independently associated to postoperative blood loss after cardiac surgery. Theoretically, prophylactic infusion of fibrinogen concentrate may thus reduce postoperative bleeding, but this has not previously been investigated. Twenty elective coronary artery bypass graft (CABG) patients with preoperative plasma fibrinogen levels <3.8 g/l were included in a prospective randomised pilot study. Patients were randomised to receive an infusion of 2 g fibrinogen concentrate (FIB group) or no infusion before surgery (control group). Primary endpoint was safety with clinical adverse events and graft occlusion assessed by multi-slice computed tomography. Predefined secondary endpoints were postoperative blood loss, blood transfusions, haemoglobin levels 24 hours (h) after surgery, and global haemostasis assessed with thromboelastometry, 2 and 24 hours after surgery. Infusion of 2 g fibrinogen concentrate increased plasma levels of fibrinogen by 0.6 +/- 0.2 g/l. There were no clinically detectable adverse events of fibrinogen infusion. Computed tomography revealed one subclinical vein graft occlusion in the FIB group. Fibrinogen concentrate infusion reduced postoperative blood loss by 32% (565 +/- 150 vs. 830 +/- 268 ml/12 h, p=0.010). Haemoglobin concentration was significantly higher 24 h after surgery in the FIB group (110 +/- 12 vs. 98 +/- 8 g/l, p=0.018). Prophylactic fibrinogen concentrate infusion did not influence global postoperative haemostasis as assessed by thromboelastometry. In conclusion, in this pilot study preoperative fibrinogen concentrate infusion reduced bleeding after CABG without evidence of postoperative hypercoagulability. Larger studies are necessary to ensure safety and confirm efficacy of prophylactic fibrinogen treatment in cardiac surgery.

Plasma fibrinogen level, bleeding, and transfusion after on‐pump coronary artery bypass grafting surgery: a prospective observational study

BACKGROUND: Early identification of patients with increased risk of excessive bleeding and transfusion after cardiac surgery offers the possibility to initiate countermeasures. Fibrinogen is a key protein in the coagulation cascade and thus a potential biomarker for bleeding. We investigated the relationship between preoperative fibrinogen plasma concentration and postoperative bleeding and transfusion after coronary artery bypass grafting (CABG).

Plasma activity of individual coagulation factors, hemodilution and blood loss after cardiac surgery: A prospective observational study

BACKGROUND Hemodilution and consumption of coagulation factors during cardiopulmonary bypass has been suggested to contribute to bleeding complications after cardiac surgery. The aim was to describe the activity of individual coagulation factors after CABG in relation to hemodilution and postoperative bleeding. MATERIALS AND METHODS Plasma concentrations of fibrinogen and plasma activity of FII, FV, FVII, FVIII, FIX, FX, FXI and FXIII adjusted for hemodilution were analysed in 57 CABG patients before, and 2h and 24h after surgery. Postoperative bleeding was registered and correlations to coagulation factor activity were calculated. RESULTS Adjusted plasma concentration of fibrinogen (-14+/-6%), and plasma activity of FII (-9+/-6%), FV (-13+/-8%), FX (-13+/-7%) and FXIII (-9+/-14%) were reduced two hours after surgery compared to baseline (all p<0.001). FVII (+3+/-12%, p=0.34) and FXI (+1+/-19%, p=0.50) were unchanged, while FVIII (+23+/-44%, p=0.006) and FIX (+23+/-17%, p<0.001) increased. Twenty-four hours after surgery fibrinogen (+45+/-27%), FVIII (+93+/-66%) and FIX (+33+/-26%) were all increased (all p<0.001), while FVII (-37+/-14%, p<0.001), FXI (-4+/-18%, p=0.02) and FXIII (-6+/-15%, p=0.004) were decreased. Median postoperative blood loss was 380 ml/12h. There were significant inverse correlations between postoperative blood loss and fibrinogen concentration 2h after surgery (r=-0.33, p=0.019) and between postoperative blood loss and pre- and postoperative FXIII activity (r=-0.34, p=0.009 and r=-0.41, p=0.003, respectively), but not between blood loss and any of the other factors. CONCLUSIONS There is a marked dissociation in plasma activity of individual coagulation factors after CABG. Plasma concentration of fibrinogen and factor XIII activity correlates inversely to postoperative blood loss after CABG.

Intraoperative thromboelastometry is associated with reduced transfusion prevalence in pediatric cardiac surgery.

BACKGROUND:The majority of pediatric cardiac surgery patients receive blood transfusions. We hypothesized that the routine use of intraoperative thromboelastometry to guide transfusion decisions would reduce the overall proportion of patients receiving transfusions in pediatric cardiac surgery. METHODS:One hundred pediatric cardiac surgery patients were included in the study. Fifty patients (study group) were prospectively included and compared with 50 procedure- and age-matched control patients (control group). In the study group, thromboelastometry, performed during cardiopulmonary bypass, guided intraoperative transfusions. Intraoperative and postoperative transfusions of packed red blood cells, fresh frozen plasma, platelets, and fibrinogen concentrates, and postoperative blood loss and hemoglobin levels were compared between the 2 groups. RESULTS:The proportion of patients receiving any intraoperative or postoperative transfusion of packed red blood cells, fresh frozen plasma, platelets, or fibrinogen concentrates was significantly lower in the study group than in the control group (32 of 50 [64%] vs 46 of 50 [92%], respectively; P < 0.001). Significantly fewer patients in the study group received transfusions of packed red blood cells (58% vs 78%, P = 0.032) and plasma (14% vs 78%, P < 0.001), whereas more patients in the study group received transfusions of platelets (38% vs 12%, P = 0.002) and fibrinogen concentrates (16% vs 2%, P = 0.015). Neither postoperative blood loss nor postoperative hemoglobin levels differed significantly between the study group and the control group. CONCLUSIONS:The results suggest that routine use of intraoperative thromboelastometry in pediatric cardiac surgery to guide transfusions is associated with a reduced proportion of patients receiving transfusions and an altered transfusion pattern.

Effects of the oral, direct factor Xa inhibitor apixaban on routine coagulation assays and anti-FXa assays

Apixaban is an oral direct factor Xa inhibitor developed for the prophylaxis and treatment of thromboembolic disorders. Laboratory monitoring is not necessary, but the effects on common coagulation reagents and assays constitute clinically valuable information.

Angiotensin-related genes in patients with panic disorder.

Enhanced respiratory variability and decreased heart rate variability have repeatedly been observed in patients with panic disorder. Prompted by the notion that angiotensin may be involved in the control of respiration, heart rate variability, and anxiety‐like behavior, we investigated the putative association between polymorphisms in three angiotensin‐related genes and panic disorder—angiotensinogen (AGT), angiotensin converting enzyme (ACE), and angiotensin II (ANG II) receptor type 1 (ATr1) in 72 patients with panic disorder and 504 controls. Allele and genotype distribution of the ATr1 A1166C allele and the AGT M235T did not differ between patients and controls. With respect to the ACE I/D polymorphism, the I allele was found to be more frequent in male (χ2 = 8.042, df = 1, P = 0.005), but not female, panic disorder patients than in controls. The results of this investigation provide preliminary evidence for the suggestion that angiotensin‐related genes may be associated with panic disorder in men.

Association between a dinucleotide repeat polymorphism of the estrogen receptor alpha gene and personality traits in women.

Estrogens are known to play a key role in the regulation of various aspects of behavior. In order to study the potential contribution of genetic variation in the estrogen receptor (ER) alpha to specific personality traits, we investigated a repeat polymorphism in the ER alpha gene in 172 42-year-old women who had been assessed using the Karolinska Scales of Personality (KSP). Based on the hypothesis that there is a relationship between the length of a repeat polymorphism and gene function,1 the alleles were divided into two groups: short and long. In order to elucidate the possible influence of the ER alpha gene on the different aspects of personality measured by means of the KSP, the possible association between this gene and four different factors (‘neuroticism’, ‘psychoticism’, ‘non-conformity’, and ‘extraversion’) was analysed. ‘Neuroticism’, ‘psychoticism’, and ‘non-conformity’ all appeared to be associated with the ER alpha gene. After correction for multiple comparisons by means of permutation analysis, the associations with the factor ‘non-conformity’—including the subscales ‘indirect aggression’ and ‘irritability’—and the factor ‘psychoticism’—including the subscale ‘suspicion’—remained significant. The results suggest that the studied dinucleotide repeat polymorphism of the ER alpha gene may contribute to specific components of personality.

Coagulation and Fibrinolytic Disturbances in Women with Polycystic Ovary Syndrome

CONTEXT Studies of fibrinolysis/coagulation status in women with polycystic ovary syndrome (PCOS) are contradictory. OBJECTIVES The aim of the study was to investigate whether women with PCOS have disturbed circulating levels of fibrinolysis/coagulation markers and, if so, whether the disturbances are related to hemodynamics, metabolic variables, sex steroids, SHBG, lipids, and inflammatory variables in women with PCOS. DESIGN/MAIN OUTCOME MEASURES: Anthropometric variables, hemodynamics, circulating hemostatic and inflammatory markers, and serum lipid profile were measured in women with untreated PCOS (n = 74) and controls (n = 31). RESULTS After adjustments for age and body mass index (BMI), circulating plasminogen activator inhibitor 1 (PAI-1) activity and fibrinogen levels were higher in women with PCOS than controls; lipid profile, blood pressure, and levels of D-dimer, von Willebrand factor, factor VIII, tissue plasminogen activator, and inflammatory markers were comparable in the two groups. In multiple linear regression analyses including women with PCOS, low SHBG and high insulin predicted high PAI-1 activity (R(2) = 0.526; P < 0.001); elevated high-sensitivity C-reactive protein and soluble E-selectin in combination with heart rate predicted high fibrinogen (R(2) = 0.333; P < 0.001). Differences in PAI-1 activity were not significant after adjustments for age, BMI, SHBG, and insulin. CONCLUSIONS PCOS is characterized by a prothrombotic state, as reflected by increased PAI-1 activity and fibrinogen, without signs of dyslipidemia or a proinflammatory state. Low SHBG and high insulin may partly explain the BMI-independent difference in PAI-1 activity between women with PCOS and controls. High-sensitivity C-reactive protein and E-selectin may be involved in regulating fibrinogen in PCOS.