Postoperative bleeding in cardiac surgery: the role of tranexamic acid in patients homozygous for the 5G polymorphism of the plasminogen activator inhibitor-1 gene.
ABSTRACT Plasminogen activator inhibitor 1 (PAI-1) attenuates the conversion of plasminogen to plasmin. Polymorphisms of the PAI-1 gene are associated with varying PAI-1 levels and risk of prothrombotic events in nonsurgical patients. The purpose of this study, a secondary analysis of a clinical trial, was to investigate whether PAI-1 genotype affects the efficacy of tranexamic acid (TA) in reducing postoperative chest tube blood loss of patients undergoing cardiopulmonary bypass.
Fifty patients were classified according to PAI-1 genotype (4G/4G, 4G/5G, or 5G/5G). Twenty-four received 2 g TA before and after cardiopulmonary bypass, whereas 26 received placebo. The authors recorded data related to coagulation, fibrinolysis, and bleeding before surgery, at admission to the intensive care unit (0 h), and 4 and 24 h later.
In patients not receiving TA, those with the 5G/5G genotype had significantly higher chest tube blood loss and transfusion requirements compared with patients with the other genotypes at all time points. Patients with the 5G/5G genotype receiving TA showed significantly lower blood loss compared with the placebo group. There were no significant differences in blood loss or transfusion requirements between patients with the 4G/4G genotype when TA was used.
Plasminogen activator inhibitor-1 5G/5G homozygotes who did not receive TA showed significantly greater postoperative bleeding than patients with other PAI-1 genotypes. 5G/5G homozygotes who received TA showed the greatest blood-sparing benefit.
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ABSTRACT: BACKGROUND: Enhanced bleeding remains a serious problem after cardiac surgery, and fibrinolysis is often involved. We speculate that lower plasma concentrations of plasminogen activator inhibitor -- 1 (PAI-1) preoperatively and tissue plasminogen activator/PAI-1 (t-PA/PAI-1) complex postoperatively might predispose for enhanced fibrinolysis and increased postoperative bleeding. METHODS: Totally 88 adult patients (mean age 66 +/- 10 years) scheduled for cardiac surgery, were enrolled into a prospective study. Blood samples were collected pre-operatively, on admission to the recovery and at 6 and 24 hours postoperatively. Patients with a surgical bleeding that was diagnosed during reoperation were discarded from the study. The patients were allocated to two groups depending on the 24-hour postoperative chest tube drainage (CTD): Group I > 500ml, Group II <= 500ml. Associations between CTD, PAI-1, t-PA/PAI-1 complex and D-dimer were analyzed with SPSS. RESULTS: Nine patients were excluded because of surgical bleeding. Of the 79 remaining patients, 38 were allocated to Group I and 41 to Group II. The CTD volumes correlated with the preoperative plasma levels of PAI-1 (r = - 0.3, P = 0.009). Plasma concentrations of preoperative PAI-1 and postoperative t-PA/PAI-1 complex differed significantly between the groups (P < 0.001 and P = 0.012, respectively). Group I displayed significantly lower plasma concentrations of fibrinogen and higher levels of D-dimer from immediately after the operation and throughout the first 24 hours postoperatively. CONCLUSIONS: Lower plasma concentrations of PAI-1 preoperatively and t-PA/PAI-1 complex postoperatively leads to higher plasma levels of D-dimer in association with more postoperative bleeding after cardiac surgery.BMC Anesthesiology 10/2012; 12(1):27. · 1.19 Impact Factor
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ABSTRACT: BACKGROUND: Tranexamic acid (TXA) effectively reduces blood loss and transfusion requirements during craniofacial surgery. The pharmacokinetics of TXA have not been fully characterized in paediatric patients and dosing regimens remain diverse in practice. A mixed-effects population analysis would characterize patient variability and guide dosing practices. OBJECTIVE: The objective of this study was to conduct a population pharmacokinetic analysis and develop a model to predict an effective TXA dosing regimen for children with craniosynostosis undergoing cranial remodelling procedures. METHODS: The treatment arm of a previously reported placebo-controlled efficacy trial was analysed. Twenty-three patients with a mean age 23 ± 19 months received a TXA loading dose of 50 mg/kg over 15 min at a constant rate, followed by a 5 mg/kg/h maintenance infusion during surgery. TXA plasma concentrations were measured and modelled with a non-linear mixed-effects strategy using Monolix 4.1 and NONMEM(®) 7.2. RESULTS: TXA pharmacokinetics were adequately described by a two-compartment open model with systemic clearance (CL) depending on bodyweight (WT) and age. The apparent volume of distribution of the central compartment (V(1)) was also dependent on bodyweight. Both the inter-compartmental clearance (Q) and the apparent volume of distribution of the peripheral compartment (V(2)) were independent of any covariate. The final model may be summarized as: CL (L/h) = [2.3 × (WT/12)(1.59) × AGE(-0.0934)] × e(η1), V(1) (L) = [2.34 × (WT/12)(1.4)] × e(η2), Q (L/h) = 2.77 × e(η3) and V(2) (L) = 1.53 × e(η4), where each η corresponds to the inter-patient variability for each parameter. No significant correlation was found between blood volume loss and steady-state TXA concentrations. Based on this model and simulations, lower loading doses than used in the clinical study should produce significantly lower peak concentrations while maintaining similar steady-state concentrations. CONCLUSIONS: A two-compartment model with covariates bodyweight and age adequately characterized the disposition of TXA. A loading dose of 10 mg/kg over 15 min followed by a 5 mg/kg/h maintenance infusion was simulated to produce steady-state TXA plasma concentrations above the 16 μg/mL threshold. This dosing scheme reduces the initial high peaks observed with the larger dose of 50 mg/kg over 15 min used in our previous clinical study.Clinical Pharmacokinetics 02/2013; · 5.49 Impact Factor
- Pediatric Anesthesia 03/2013; 23(3):278-84. · 2.44 Impact Factor