Heparin Reversal Research Articles

Case Report: Post transcatheter aortic valve replacement shock: Value of multimodal imaging

Complications resulting from the delayed clinical presentation of a left main coronary artery obstruction can be catastrophic. This case report presents a 73-year-old woman with severe aortic stenosis who underwent transcatheter aortic valve replacement with a core valve who, approximately 20 minutes after heparin reversal with protamine, became hypotensive and was unresponsive to vasopressor and inotropic therapy. Transesophageal echocardiography demonstrated global hypokinesis, which was highly consistent with the occlusion of the left main coronary artery. Angiography confirmed this diagnosis and demonstrated that valve positioning had not changed compared to post-placement examination. Here we report the partial covering of the ostium of the left main coronary artery by a core valve skirt that converted into a total occlusion following the initiation of heparin reversal with protamine and the value of multimodal imaging in the management of this case.

Effects of circuit albumin coating on coagulation and inflammatory response for patients receiving aortic arch replacement: a randomized controlled trial.

To investigate whether human serum albumin coating before cardiopulmonary bypass (CPB) could improve platelet function and hemostasis and mitigate the inflammatory response among patients receiving aortic arch replacement with deep hypothermic circulatory arrest (DHCA). Sixty patients were included and randomized into two groups: the Control Group (CG, receiving 40 g human albumin 5 minutes after the initiation of CPB) and the Study Group (SG, circulating the prime with 40 g albumin for 5 minutes before CPB). Rapid thromboelastography, complete blood count, coagulation tests and cytokines (IL-1, IL-6, IL-10, TNF-α and PAF) were measured at two intervals: after anesthesia induction and before CPB (T1) and 10 minutes after heparin reversal before any blood product transfusion (T2). Compared with T1, the fibrinogen and MA levels in both groups reduced significantly after heparin reversal and fell within the normal range for most patients. The platelet count reduction (ΔPLT) in the Study Group was significantly less than in the Control Group (p=0.031). Despite the inflammatory factor levels increasing after CPB (p<0.001), no differences were found between the Control Group and the Study Group. Fewer red blood cells were given in the Study Group, but this was not significant (p=0.05). Most patients receiving aortic arch replacement with DHCA have normal platelet function and fibrinogen levels after heparin reversal. Albumin coating before CPB may mitigate the platelet count reduction, but not platelet dysfunction. There is a trend that the patients treated with albumin coating received less red blood cell transfusions.

Half dose protamine sulphate, does it work in valvular replacement cardiac surgery? A prospective, double-blinded randomized study

IntroductionCardiac surgery of valvular replacement carries multiple complications, the commonest of which is bleeding. Effective anti-coagulation during valvular replacement is necessary to prevent excessive activation of the hemostatic system; protamine sulfate is used to neutralize the effect of circulating heparin. The Aim of the work was to determine the effectiveness of half dose Protamine in reversing the action of heparin in valvular replacement cardiac surgery without the appearance the side effect of protamine.Method40 patients undergoing valvular replacement divided into two groups. Group A: received 1mg of protamine per 100 unit heparin (common ratio 1:1, protamine: heparin). Group B: received 0.5 mg of protamine per100 unit of heparin (our ratio 1:2, protamine: heparin). Following data were detected in each patients (1) blood loss, 2 Activated clotting Time, (3) Hemoglobin, (4) unites of FFP requirements, (5) Clotting Time, and Maximum Clot Firmness (MCF) test.ResultsWe found that the administration of half (1/2) of Total Calculated Dose of protamine sulphate was always able to reverse the anticoagulant effect of heparin .with insignificant difference in hemodynamic parameters, and in the amount of blood loss and insignificant difference in unites of FFP requirement, on other hand there was mild significant results in MCF test between both groups.DiscussionOur present study suggests that the commonly applied ratio equal to 1:1 (ratio of protamine to heparin) could be higher than needed with potential and hazardous impacts and lowering it to be 1:2 ratio is similarly effective. Our results are in line with the findings obtained by Salvatore et al., who observed that reversal of heparin administered in patients undergoing cardiac surgery could be effectively achieved with 2/3 of the usual dose of Protamine and that the additional administration of protamine seems to induce an elongation of the clotting time with no impact on clot firmness. (1) While the impact of a high protamine to heparin ratio was even studied by Kahn et al., who studied blood samples of 46 patients undergoing cardiac surgery using CABG and found a significant worsening of the coagulation parameters using protamine to heparin ratio of more than 2:12.

Optimizing Thrombin Generation with 4-Factor Prothrombin Complex Concentrates in Neonatal Plasma After Cardiopulmonary Bypass.

Bleeding is a serious complication after pediatric cardiopulmonary bypass (CPB) that is associated with an increase in perioperative morbidity and mortality. Four-factor prothrombin complex concentrates (4F-PCCs) have been used off-label to supplement transfusion protocols for bleeding after CPB in adults; however, data on their use in neonates are limited. In this study, we hypothesized that 4F-PCCs administered ex vivo to neonatal plasma after CPB will increase thrombin generation. Fifteen neonates undergoing complex cardiac repairs requiring CPB were enrolled in this prospective study. Arterial blood was obtained after anesthesia induction but before CPB (baseline), after CPB following heparin reversal, and after our standardized transfusion of a quarter of a platelet apheresis unit (approximately 20 mL·kg) and 3 units of cryoprecipitate. Kcentra (CSL Behring), a 4F-PCC with nonactivated factor VII (FVII), and factor 8 inhibitor bypassing activity (FEIBA; Baxter Healthcare Corporation), a 4F-PCC with activated FVII, were added ex vivo to plasma obtained after CPB to yield concentrations of 0.1 and 0.3 IU·mL. Calibrated automated thrombography was used to determine thrombin generation for each sample. The addition of Kcentra to plasma obtained after CPB resulted in a dose-dependent increase in the median (99% confidence interval) peak amount of thrombin generation (42.0 [28.7-50.7] nM for Kcentra 0.1 IU·mL and 113.9 [99.0-142.1] nM for Kcentra 0.3 IU·mL). The rate of thrombin generation was also increased (15.4 [6.5-24.6] nM·min for Kcentra 0.1 IU·mL and 48.6 [29.9-66.6] nM·min for Kcentra 0.3 IU·mL). The same was true for FEIBA (increase in peak: 39.8 [27.5-49.2] nM for FEIBA 0.1 IU·mL and 104.6 [92.7-124.4] nM for FEIBA 0.3 IU·mL; increase in rate: 17.4 [7.4-28.8] nM·min FEIBA 0.1 IU·mL and 50.5 [26.7- 63.1] nM·min FEIBA 0.3 IU·mL). In the posttransfusion samples, there was a significant increase with Kcentra in the median (99% confidence interval) peak amount (41.1 [21.0-59.7] nM for Kcentra 0.1 IU·mL and 126.8 [106.6- 137.9] nM for Kcentra 0.3 IU·mL) and rate (18.1 [-6.2 to 29.2] nM·min for Kcentra 0.1 IU·mL and 53.2 [28.2-83.1] nM·min for Kcentra 0.3 IU·mL) of thrombin generation. Again, the results were similar for FEIBA (increase in peak: 43.0 [36.4-56.7] nM for FEIBA 0.1 IU·mL and 109.2 [90.3-136.1] nM for FEIBA 0.3 IU·mL; increase in rate: 25.0 [9.1-32.6] nM·min for FEIBA 0.1 IU·mL and 59.7 [38.5-68.7] nM·min for FEIBA 0.3 IU·mL). However, FEIBA produced in a greater median reduction in lag time of thrombin generation versus Kcentra in samples obtained after CPB (P = 0.003 and P = 0.0002 for FEIBA versus Kcentra at 0.1 and 0.3 IU·mL, respectively) and in samples obtained after transfusion (P < 0.0001 for FEIBA versus Kcentra at 0.1 and 0.3 IU·mL). After CPB, thrombin generation in neonatal plasma was augmented by the addition of 4F-PCCs. The peak amount and rate of thrombin generation were enhanced in all conditions, whereas the lag time was shortened more with FEIBA. Our findings suggest that the use of 4F-PCCs containing activated FVII may be an effective adjunct to the initial transfusion of platelets and cryoprecipitate to augment coagulation and control bleeding in neonates after CPB.

Heparin Reversal After Cardiopulmonary Bypass: Are Point-of-Care Coagulation Tests Interchangeable?

Protamine is used to neutralize heparin after patient separation from cardiopulmonary bypass (CPB). Different bedside tests are used to monitor the adequacy of heparin neutralization. For this study, the interchangeability of the activated coagulation time (ACT) and thromboelastometry (ROTEM; Tem Innovations GmbH, Basel, Switzerland) clotting time (CT) ratios in children undergoing cardiac surgery was assessed. Single-center, retrospective, cohort study between September 2010 and January 2012. University children's hospital. The study comprised children 0 to 16 years old undergoing elective cardiac surgery with CPB. Exclusion criteria were preoperative coagulopathy, Jehovah's witnesses, and children in a moribund condition (American Society of Anesthesiologists score 5). None. After heparin neutralization with protamine, the ratio between ACT, with and without heparinase, and the CT measured with INTEM/HEPTEM (intrinsic test activated with ellagic acid was performed without heparinase [INTEM] and with heparinase [HEPTEM]) using tests of ROTEM were calculated. Agreement was evaluated using Cohen's kappa statistics, Passing-Bablok regression, and Bland-Altman analysis. Among the 173 patients included for analysis, agreement between both tests showed a Cohen's kappa statistic of 0.06 (95% CI: -0.02 to 0.14; p = 0.22). Bland-Altman analysis showed a bias of 0.01, with a standard deviation of 0.13, and limits of agreement between -0.24 and 0.26. Passing-Bablok regression showed a systematic difference of 0.40 (95% CI: 0.16-0.59) and a proportional difference of 0.61 (95% CI: 0.42-0.86). The residual standard deviation was 0.11 (95% CI: -0.22 to 0.22), and the test for linearity showed p = 0.10. ACT, with or without heparinase, and the INTEM/HEPTEM CT ratios are not interchangeable to evaluate heparin reversal after pediatric patient separation from CPB. Therefore, the results of these tests should be corroborated with the absence/presence of bleeding and integrated into center-specific treatment algorithms.

Use of Protamine for Anticoagulation During Carotid Endarterectomy: A Meta-analysis.

Protamine sulfate can be administered at the conclusion of carotid endarterectomy (CEA) to reverse the anticoagulant effects of heparin and to limit the risk for postoperative bleeding. Protamine use remains controversial owing to concern for increased thrombotic complications with its use. To review the evidence for and against protamine use, both in its association with increased thrombotic complications and with decreased bleeding. We searched Medline (1946-2014), EMBASE (1966-2014), Cochrane Library (1972-2014), clinical trial registries (World Health Organization International Clinical Trials Registry and clinicaltrials.gov), and abstracts from conferences of the Society of Vascular Surgery (2002-2014) and American Heart Association Scientific Sessions (1980-2014) in November 2014. No language restrictions were applied. We included clinical trials and observational studies comparing reversal of heparin with protamine sulfate vs no reversal in patients undergoing carotid revascularization and reporting stroke during hospitalization. Of 360 records screened, 12 studies (3%) of CEA were eligible for data pooling. Two reviewers extracted data and assessed quality. Random-effects models were used to summarize relative risks (RRs). Stroke after CEA. We included 12 observational studies involving 10,621 patients in the meta-analysis. Event rates did not differ significantly between patients who received protamine vs those who did not for the following outcomes: stroke (RR, 0.84; 95% CI, 0.55-1.29; I(2) = 15%; 9 studies), myocardial infarction (RR, 0.89; 95% CI, 0.53-1.51; I(2) = 0%; 3 studies), or mortality (RR, 0.9, 95% CI, 0.62-1.29; I(2) = 0%; 7 studies). The use of protamine was associated with a significant decrease in major bleeding complications requiring reoperation (RR, 0.57; 95% CI, 0.39-0.84; I(2) = 32%; 10 studies). Based on available evidence, the use of protamine following CEA is associated with a reduction in bleeding complications, without increasing major thrombotic outcomes, including stroke, myocardial infarction, or death.

The Benefit of Heparin Reversal With Protamine During Carotid Endarterectomy.

The Benefit of Heparin Reversal With Protamine During Carotid Endarterectomy.

The effects on coagulation of the reinfusion of unprocessed residual blood from the cardiopulmonary bypass.

Background Autologous blood transfusion is a common technique in cardiac surgery to directly re-infuse residual blood from the cardiopulmonary bypass (CPB) circuit to the patient. The objective of this study was to evaluate the effects of reinfusion of unprocessed residual pump blood on the coagulation system after separation from the CPB circuit and reversal of systemic heparin with protamine. Measurements and main results After ethics approval, 40 participants undergoing cardiac surgery were recruited in a prospective single center cohort study. Changes in coagulation were assessed with standard plasma based laboratory assays and thromboelastography. After the reinfusion of unprocessed residual pump blood there were decreases in the mean aPTT (effect size 6 s; SD: 6.05; p < 0.0001) and thrombin time (effect size 4.08 s; SD: 9.7; p = 0.01). There were no significant changes in PT, INR and D-dimer. Post reinfusion there were increases in fibrinogen, hemoglobin and platelet counts. There were improvements in the R-time (effect size 9.1 s; SD: 16.9; p = 0.0023), K-time (effect size 1.5 s; SD: 3.6 s; p = 0.0017), alpha angle (6.9°; SD: 15.8; p = 0.012), and maximum amplitude (3.0 mm; SD: 5.6, p = 0.002) on thromboelastography.ConclusionThe reinfusion of unprocessed residual CPB blood resulted in no deleterious effects on the coagulation system measured by both the common laboratory plasma based measurements of coagulation and thromboelastography.

Andexanet alfa for reversal of factor Xa inhibitors induced-anticoagulation in nonclinical and clinical studies

Andexanet alfa for reversal of factor Xa inhibitors induced-anticoagulation in nonclinical and clinical studies

A synthetic heparin antidote with negligible effect on fibrin(ogen), clotting and clot morphology

Event Abstract Back to Event A synthetic heparin antidote with negligible effect on fibrin(ogen), clotting and clot morphology Manu Thomas Kalathottukaren1*, Benjamin F. Lai1*, Libin Abraham2*, Fredrico Rosell1*, Edward L. Pryzdial1, Charles A. Haynes3* and Jayachandran N. Kizhakkedathu1, 4* 1 University of British Columbia, Pathology and laboratory Medicine, Canada 2 University of British Columbia, Department of Immunolgy and Microbiology, Canada 3 University of British Columbia, Department of Chemical and Biological Engineering, Canada 4 University of British Columbia, Chemistry, Canada Background and Objective: Heparin anticoagulants are used to treat thrombosis; the leading cause of deaths worldwide. However, anticoagulation associated haemorrhage is a major concern. Hence, antidote is required to counteract anticoagulation and to restore hemostasis. Protamine sulphate (PS), a cationic polypeptide is the only clinically approved antidote for unfractionated heparin. PS is unable to completely reverse low molecular weight heparins and fondaparinux due to its low binding affinity to these drugs. In addition, PS exhibits non-specific interaction with clotting proteins such as fibrinogen to form aggregates and alters fibrin clot morphology. This often leads to hematological complications. To address these challenges, we developed a synthetic universal heparin reversal agent (UHRA) with high binding affinity to heparins, thereby completely reversing the activity of all clinically available parenteral anticoagulants1.This study aims to demonstrate and corroborate the nontoxic nature of UHRA by assessing its influence on fibrinogen, clotting, fibrin/blood clot architecture and stability. Methods: UHRA was developed by incorporating tertiary amine based heparin binding groups on a dendritic hyperbranched polyglycerol scaffold and capping it with methoxy polyethylene glycol chains. Recalcification and tissue factor (TF) initiated plasma clotting assays was performed to understand the impact of UHRA on clotting system. The interaction of UHRA on fibrinogen was investigated by fibrin polymerization assay and by spectroscopic analysis (fluorescence and circular dichroism (CD)). The influence of UHRA on fibrin/blood clot architecture was evaluated by scanning electron microscopy (SEM). Confocal microscopy was used to investigate the incorporation of Alexa-488 tagged UHRA into fibrin clots. The lysis of TF-induced plasma clot containing UHRA or PS exposed to exogenous tissue plasminogen activator (t-PA) was studied by turbidimetric assay. Results and discussion: Clotting assays revealed that UHRA did not alter clotting parameters (lag time and maximum absorbance) compared to PS. This suggests that UHRA has no effect on clotting cascade. Unlike protamine, the fibrinogen aggregation and fibrin polymerization assay was not influenced by UHRA over a broad range of concentrations from 0.05 mg/mL to 1 mg/mL. Tryptophan fluorescence quenching and fibrinogen secondary structure measurements, corroborates that UHRA is not interacting with fibrinogen. However, PS and other synthetic cationic polymers interact with fibrinogen, eliciting aggregation and conformational changes. Fibrin clots generated in presence of UHRA (even at 0.5 mg/mL) showed similar structure and fiber size remains same as normal fibrin clot (control vs UHRA 0.5 mg/mL clot, p= 0.12) (Figure 1). On the other hand, fibrin clots formed in the presence of 0.05mg/mL PS (clinical dose) increased the fiber size and changed the clot structure dramatically (control vs PS 0.05mg/mL clot, p< 0.0001). Confocal images of fibrin clots show no incorporation of UHRA into clots, compared to PS (Figure 2). Clot lysis studies in the presence of exogenous t-PA demonstrate that UHRA did not enhance clot degradation. Conclusion and significance: Studies demonstrate that, UHRA, has negligible impact on fibrinogen, fibrin polymerization, clot structure, clot degradation, coagulation system and shows no binding to clot structures, revealing their excellent hemocompatibility compared to protamine. Our results support the fact that UHRA could be an ideal antidote to restore hemostasis following invasive surgical procedures and to address bleeding complications by heparin based anticoagulants. [1] Canadian Institutes of Health Research (CIHR); Natural Science and Engineering Research Council (NSERC)

Unravelling the binding energetics of a synthetic polymeric heparin antidote with heparin using isothermal titration calorimetry

Unravelling the binding energetics of a synthetic polymeric heparin antidote with heparin using isothermal titration calorimetry

Reversal of Heparin-Induced Anticoagulation By Andexanet Alfa, a Universal Antidote for Factor Xa Inhibitors

Background: Unfractionated heparin is used in the management of venous thromboembolism, stroke prevention in atrial fibrillation as well as in cardiac surgeries (e.g., valve replacement and other procedures requiring cardiopulmonary bypass). Bleeding is the major complication that may result from these therapies. Although protamine sulfate can be used to neutralize heparin, its administration can cause severe hypotensive and anaphylactic reactions. Andexanet alfa (AnXa) is a recombinant modified human fXa under development for the reversal of both direct and antithrombin III (ATIII)-dependent indirect fXa inhibitors. We previously reported nonclinical and Phase 2 clinical data in healthy subjects with enoxaparin, a low molecular weight heparin (LMWH). Here we report new in vitro data demonstrating that AnXa can also effectively reverse anticoagulation of unfractionated heparin.Methods: Inhibition of human fXa or thrombin (IIa) by ATIII in the presence of heparin was studied in an enzymatic assay in buffered solution. The reaction mixture contained fXa or IIa (20 nM), ATIII (200 nM), different amounts of unfractionated heparin and AnXa. At different time points, a small aliquot of the reaction mixture was taken and quenched into a 96-well assay plate containing protamine (50 µg/mL) and a chromogenic substrate (100 µM) for fXa (Spectrozyme-Xa) or IIa (S2238). Residual fXa or IIa activity was measured in a plate reader by monitoring the initial rate of substrate cleavage at 405 nm. Reversal of heparin anti-fXa and anti-IIa activities by AnXa in human plasma was evaluated using modified anti-fXa and anti-IIa chromogenic assays. Reversal of heparin-induced clotting prolongation of human plasma was measured by a 96-well format turbidity assay using an aPTT reagent and Ca2+. The reversal effect of AnXa on heparin anticoagulation and clot formation was further characterized by thromboelastography (TEG) in human plasma or whole blood. Reversal of heparin was compared to enoxaparin. Protamine sulfate was included as a control. Di-arginine piperazine (PER977), a positively charged small molecule, was also tested for comparison.Results: AnXa dose-dependently reversed the anti-fXa activity of heparin in the enzymatic assay and in human plasma. Interestingly, AnXa was also able to reverse the heparin anti-IIa activity in the same assays. In the enzymatic assay with IIa and ATIII, heparin accelerated the reaction of IIa inhibition by ~1000-fold. AnXa dose-dependently reversed the IIa inhibition to its basal level seen without heparin. The reversal effect of AnXa on IIa inhibition could be blocked by addition of a small molecule direct fXa inhibitor (e.g. rivaroxaban) in the same enzymatic assay. This suggests that interaction of AnXa with the primary binding site on the surface of heparin-activated ATIII (i.e., the reactive center loop (RCL)) might play a major role in the anti-IIa reversal as binding to the RCL was the minimal requirement for the inhibition of both fXa and IIa by ATIII. In human plasma, AnXa reversed the anti-IIa activity of heparin (0.8 IU/mL) with an estimated EC50 comparable to anti-fXa reversal (anti-fXa:126 nM; anti-IIa: 131nM). These results indicate that AnXa was able to compete with not only fXa, but also IIa, for binding to heparinized-ATIII and reverse both the anti-fXa and anti-IIa activities of heparin. In addition, AnXa dose-dependently and completely reversed prolongation of clotting by heparin (0.8 IU/mL) in human plasma as measured by the turbidity assay as well as parameters of heparin (1.0 IU/mL) anticoagulation as measured by TEG in either plasma or whole blood. As expected, protamine sulfate (5-10 µg/mL) neutralized heparin (1.0 IU/mL) anticoagulation in plasma in the TEG assay. At higher concentrations, protamine prevented clot formation, consistent with protamine's known anticoagulant effect when overdosed. No reversal activity was observed by PER977 in the same TEG assays using either plasma or whole blood.Conclusions: The current and previously reported data demonstrate that AnXa could be a universal fXa inhibitor antidote to reverse a broad range of newer direct oral fXa inhibitors, ATIII-dependent indirect inhibitors, such as fondaparinux and enoxaparin, as well as unfractionated heparin. The mechanism for reversal of ATIII-dependent inhibitors by AnXa is distinct from other positively charged molecules that bind directly to heparin. DisclosuresLu:Portola Pharmaceuticals, Inc.: Employment. Lin:Portola Pharmaceuticals, Inc.: Employment. Curnutte:Sea Lane Biotechnologies: Consultancy; 3-V Biosciences: Equity Ownership; Portola Pharmaceuticals, Inc.: Employment. Conley:Portola Pharmaceuticals, Inc.: Employment.

Point-of-Care Hemoglobin/Hematocrit Testing: Comparison of Methodology and Technology

Point-of-care (POC) testing allows rapid assessment of hemoglobin (Hgb) and hematocrit (Hct) values. This study compared 3 POC testing devices--the Radical-7 pulse oximeter (Radical-7, Neuchȃtel, Switzerland), the i-STAT (Abbott Point of Care, Princeton, NJ), and the GEM 4000 (Instrumentation Laboratory, Bedford, MA)--to the hospital reference device, the UniCel DxH 800 (Beckman Coulter, Brea, CA) in cardiac surgery patients. Prospective study. Tertiary care cardiovascular center. Twenty-four consecutive elective adult cardiac surgery patients. Hgb and Hct values were measured using 3 POC devices (the Radical-7, i-STAT, and GEM 4000) and a reference laboratory device (UniCel DxH 800). Data were collected simultaneously before surgery, after heparin administration, after heparin reversal with protamine, and after sternal closure. Data were analyzed using bias analyses. POC testing data were compared with that of the reference laboratory device. Hgb levels ranged from 6.8 to 15.1 g/dL, and Hct levels ranged from 20.1% to 43.8%. The overall mean bias was lowest with the i-STAT (Hct, 0.22%; Hgb 0.05 g/dL) compared with the GEM 4000 (Hct, 2.15%; Hgb, 0.63 g/dL) and the Radical-7 (Hgb 1.16 g/dL). The range of data for the i-STAT and Radical-7 was larger than that with the GEM 4000, and the pattern or slopes changed significantly with the i-STAT and Radical-7, whereas that of the GEM 4000 remained relatively stable. The GEM 4000 demonstrated a consistent overestimation of laboratory data, which tended to improve after bypass and at lower Hct/Hgb levels. The i-STAT bias changed from overestimation to underestimation, the latter in the post-cardiopulmonary bypass period and at lower Hct/Hgb levels. By contrast, the Radical-7 biases increased during the surgical procedure and in the lower ranges of Hgb. Important clinical differences and limitations were found among the 3 POC testing devices that should caution clinicians from relying on these data as sole determinants of when or when not to perform transfusion in patients. Even though a low bias might support the use of POC data, further analysis of the bias plots demonstrates pattern changes during the surgical procedure and across the range of Hct/Hgb data.

Protamine reduces whole blood platelet aggregation after cardiopulmonary bypass

Objectives: Platelet dysfunction is an important cause of postoperative bleeding after cardiac surgery. Protamine is routinely used for reversal of heparin after cardiopulmonary bypass (CBP), but may affect platelet aggregation. We assessed changes in platelet function in relation to protamine administration. Design: Platelet aggregation was analyzed by impedance aggregometry before and after protamine administration in 25 adult cardiac surgery patients. Aggregation was also studied after in vitro addition of heparin and protamine. The activators adenosine diphosphate (ADP), thrombin receptor activating peptide-6 (TRAP), arachidonic acid (AA) and collagen (COL) were used.Results: Platelet aggregation was reduced by approximately 50% after in vivo protamine administration; ADP 640 ± 230 (AU*min, mean ± SD) to 250 ± 160, TRAP 939 ± 293 to 472 ± 260, AA 307 ± 238 to 159 ± 143 and COL 1022 ± 350 to 506 ± 238 (all p < 0.001). Aggregation was also reduced after in vitro addition of protamine alone with activators ADP from 518 ± 173 to 384 ± 157 AU*min p < 0.001, and AA 449 ± 311 to 340 ± 285 (p < 0.01) and protamine combined with heparin (1:1 ratio) with activators ADP to 349 ± 160 and AA to 308 ± 260 (both p < 0.001); and COL from 586 ± 180 to 455 ± 172 (p < 0.05). Conclusions: Protamine given after CPB markedly reduces platelet aggregation. Protamine added in vitro also reduces platelet aggregation, by itself or in combination with heparin.

New synthetic peptide with efficacy for heparin reversal and low toxicity and immunogenicity in comparison to protamine sulfate

Protamine sulfate (PS), the only clinically approved antidote to unfractionated heparin (UFH), is widely used for cardiopulmonary surgery or other extracorporeal circulation situations. However, the applications of PS have accompanied various severe side-effects. In this study, we presented a novel synthesized peptide compound (RRRRR-RRRRR-RRRRR-sulfate, R15S) served as a safer UFH antidote. Comparison studies were conducted between PS and R15S on efficacy and safety, aided by heparin neutralization studies, drug toxicity studies and anaphylactic analysis. Our research demonstrated that R15S contained comparable UFH neutralization activity in vitro and in rats in vivo as to active partial thromboplastin time (APTT) and anti-FXa assays. There was no cytotoxicity for R15S at 60 μg mg−1 or below and the median lethal dose (LD50) of R15S in mice was 35.4 mg kg−1, both of which were similar to that of PS. Furthermore, R15S exhibited no immunogenicity while it was obvious in guinea pigs immunized with PS. The level of cross-reactivity to anti-PS antibodies of R15S was about 30%. Both of which indicated much safer properties of R15S than PS. In conclusion, we presented a promising candidate R15S for UFH reversal, which is effective in neutralizing UFH and potentially safer in use.

An Adjusted Calculation Model Allows for Reduced Protamine Doses without Increasing Blood Loss in Cardiac Surgery.

Background Heparin dosage for anticoagulation during cardiopulmonary bypass (CPB) is commonly calculated based on the patient's body weight. The protamine-heparin ratio used for heparin reversal varies widely among institutions (0.7-1.3 mg protamine/100 IU heparin). Excess protamine may impair coagulation. With an empirically developed algorithm, the HeProCalc program, heparin, and protamine doses are calculated during the procedure. The primary aim was to investigate whether HeProCalc-based dosage of heparin could reduce protamine use compared with traditional dosages. The secondary aim was to investigate whether HeProCalc-based dosage of protamine affected postoperative bleeding. Patients and Methods We consecutively randomized 40 patients into two groups. In the control group, traditional heparin and protamine doses, based on body weight alone, were given. In the treatment group, the HeProCalc program was used, which calculated the initial heparin bolus dose from weight, height, and baseline activated clotting time and the protamine dose at termination of CPB. Results We analyzed the results from 37 patients, after exclusion of three patients. Equal doses of heparin were given in both groups, whereas significantly lower mean doses of protamine were given in the treatment group versus control group (211 ± 56 vs. 330 ± 61 mg, p < 0.001). Postoperative bleeding was less in the HeProCalc group (280 ± 229 mL) as compared with the control group (649 ± 279 mL). However, this difference was not found statistically significant (p = 0.074). Conclusion HeProCalc-based dosage of heparin and protamine allowed for reduced protamine use after CPB compared with when conventional calculations were used. Furthermore, HeProCalc-based regimen for heparin reversal suggested less postoperative bleeding, although the difference between the groups was not statistically significant.

Validation of viscoelastic coagulation tests during cardiopulmonary bypass

Viscoelastic point-of-care tests such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are increasingly used to guide hemostatic therapy after cardiac surgery. The aim of this study was to assess their clinical utility during cardiopulmonary bypass to predict postbypass coagulation status and to guide therapy. In this prospective study, TEG and ROTEM tests were performed in 52 adult patients undergoing elective cardiac surgery at two time points: near the end of cardiopulmonary bypass and after heparin reversal with protamine. The 95% confidence intervals of the mean difference were compared with a prespecified clinically relevant limit of ±20% of the value after protamine. Both viscoelastic fibrinogen assays were well within the prespecified clinically relevant limit (≥79% of patients). The laboratory Clauss fibrinogen was much lower during cardiopulmonary bypass than after protamine (mean difference 1.2gL(-1) , 95% CI 1.03-1.4, which was outside a clinically acceptable difference. For intrinsically activated tests, clotting times (CT) were different and outside the prespecified limit on TEG (mean difference -1.2 min, 95% CI -1.8 to -0.6) but not on ROTEM (mean difference 2.3 sec, 95% CI -8.6 to 13.2), while clot strength was well within the clinical limit on both devices (≥94% of patients). For extrinsically activated tests, clot strength on both TEG and ROTEM was within the pre-specified limit in 98% of patients. Results from TEG and ROTEM tests performed toward the end of cardiopulmonary bypass are similar to results after reversal of heparin. Amplitudes indicating clot strength were the most stable parameters across all tests, whereas CT showed more variability. In contrast, laboratory testing of fibrinogen using the Clauss assay was essentially invalid during cardiopulmonary bypass.

Validation of viscoelastic coagulation tests with TEG and ROTEM during cardiopulmonary bypass

Background & Aim. Visco-elastic point-of-care tests such as TEG and ROTEM are increasingly used to guide haemostatic therapy after cardiac surgery. Their use during cardiopulmonary bypass (CPB) has the potential advantage of earlier information about haemostasis allowing the preparation of blood products. However, testing during CPB might be affected by heparinization and its reversal with protamine and has not been validated (1). The aim of this study was to assess the clinical utility of visco-elastic coagulation tests during cardiopulmonary bypass to predict post-bypass coagulation status and to guide therapy. Methods. In this prospective study, TEG and ROTEM tests were performed in fifty-two adult patients undergoing elective cardiac surgery at two time points: near the end of cardiopulmonary bypass (on-CPB) and after heparin reversal with protamine (post-protamine). Clotting times (R-time, CT) and clot strength (MA, MCF) were compared between the two time points for each test assay. The 95% confidence intervals of the mean difference were compared to a pre-specified clinical important limit of þ/-20% of the post-protamine value. Correlation between TEG and ROTEM and visco-elastic and corresponding laboratory values (Clauss Fibrinogen, PT, aPTT) was also assessed. Results. Both visco-elastic fibrinogen assays were well within the pre-specified clinically important limit (Z79% of patients). Fibrinogen assays correlated well between the analysers (Pearson r1⁄40.69) but had a bias (Bland-Altman) of 5.4mm. The laboratory Clauss fibrinogen was much lower during cardiopulmonary bypass than after protamine (mean difference 1.2g/L, 95% CI 1.03 1.4, po0.01), which was well outside a clinically acceptable difference. For intrinsically activated tests, clotting times were different and outside the pre-specified limit on TEG (po0.01) but not on ROTEM (p1⁄40.67), while clot strength was well within the clinical limit on both devices (Z94% of patients). For extrinsically activated tests, clotting time was different on ROTEM (po0.01) but not on TEG (p1⁄40.24), but both were within the clinical limit. The clot strength was different on TEG (po0.01) but not on ROTEM (p1⁄40.57) while both were within the pre-specified limit in 98% of patients. Conclusion. Results from TEG and ROTEM tests performed towards the end of cardio-pulmonary-bypass are clinically comparable to results after reversal of heparin. Amplitudes indicating clot-strength were the most stable parameters across all tests whereas clotting times showed more variability. In contrast laboratory testing of fibrinogen using the Clauss assay was essentially invalid during cardiopulmonary bypass.

Safety and efficacy outcomes of protamine administration for heparin reversal following cryoballoon-based pulmonary vein isolation.

Anticoagulation with heparin is required during catheter ablation of atrial fibrillation (AF) to reduce systemic thromboembolism. In this study, we aim to compare safety and efficacy outcomes between patients who receive protamine administration for reversal of heparin and those who do not, following cryoballoon-based pulmonary vein isolation (PVI) for AF. Patients with symptomatic paroxysmal or persistent AF despite ≥1 antiarrhythmic drug(s) were scheduled for PVI per the recent consensus recommendations. Some patients were administered protamine at the end of the procedure depending on the operator's choice. Among 380 patients [48.2% male, 56 (20-86) years] that were enrolled, 188 patients received protamine at the end of the procedure. Baseline characteristics did not differ between groups (p > 0.05). Mean protamine dose was 39.1 ± 6.4 mg. Only 1 patient developed rash following protamine infusion. Hospital stay was significantly shorter in patients who were administered protamine (1 [1-5] vs. 2 [1-7] days, p < 0.001). Hematoma/pseudoaneurysm or femoral AV fistula requiring surgical or interventional repair in the femoral access site occurred in 2 (1.1 %) patients who received protamine and 12 (6.3%) patients who did not (p = 0.011). Deep vein thrombosis was seen in 1 patient in whom protamine was not administered (p = 0.499). To the best of our knowledge, this is one of the largest series showing that protamine administration for heparin reversal in patients undergoing cryoballoon-based PVI allows quicker sheath removal and minimizes the risk of potential vascular complications without causing an increase in thrombotic events.

Rotational thromboelastometry in prediction of bleeding after cardiac surgery.

Reexploration and its associated complications significantly affect hospital mortality and morbidity. Therefore, to prevent postoperative bleeding and its related complications, using an appropriate modality is essential during cardiac surgery. Four hundred patients (296 males and 104 females, mean age 60.8 ± 9 years) scheduled for first-time coronary artery bypass graft surgery were prospectively enrolled. Blood samples were obtained for ROTEM testing before surgery and 30 min after heparin reversal. The patients were divided into 2 groups: group 1 was patients with no abnormal postoperative bleeding and group 2 was patients who required reexploration for abnormal postoperative bleeding. Group 2 patients were divided into 2 subgroups: 2a was patients with surgical bleeding and group 2b was patients with nonsurgical bleeding. Variables were compared between groups. Among the 400 patients, 42 were reexplored. Hospital stay was significantly longer and hospital deaths more frequent in group 2 patients (p < 0.001 and p = 0.010, respectively). Ten (2.8%) patients had abnormal preoperative results of ROTEM in group 1 compared to 14 (33.3%) in group 2 (p < 0.001). After surgery, the number of patients with abnormal ROTEM results was significantly different between the 2 groups: 6 (1.7%) in group 1 vs. 14 (33.3%) in group 2 (p < 0.001). Four (12.5%) patients in group 2a had abnormal preoperative ROTEM results compared to 10 (100%) in group 2a (p < 0.001). Measuring coagulation factors by ROTEM both before surgery and after heparin reversal can identify patients at increased risk of postoperative bleeding.