Anaesthesiologic Considerations for Intraoperative ECMO Anticoagulation During Lung Transplantation: A Single-Centre, Retrospective, Observational Study

Background: Extracorporeal membrane oxygenation (ECMO) is frequently used during lung transplantation. Unfractionated heparin (UFH) is mainly used as part of ECMO support for anticoagulation. One of the most common perioperative complications is bleeding, which high-dose UFH can aggravate. Methods: We retrospectively analyzed (n = 141) patients who underwent lung transplantation between 2020 and 2022. All subjects (n = 109) underwent central cannulated VA ECMO with successful intraoperative ECMO weaning. Patients on ECMO bridge, postoperative ECMO, heart-lung transplants and transplants without ECMO were excluded. The dose of UFH for the entire surgical procedure, blood loss and consumption of blood derivatives intraoperatively and 48 h after ICU admission were recorded. Surgical revision for postoperative bleeding were analyzed. Thrombotic complications, mortality and long-term survival were evaluated. Results: Lower doses of UFH administered for intraoperative ECMO anticoagulation contribute to a reduction in intraoperative blood derivates consumption and blood loss with no thrombotic complications related to the patient or the ECMO circuit. Lower doses of UFH may lead to a decreased incidence of surgical revision for hemothorax. Conclusion: Lower doses of UFH as part of intraoperative ECMO anticoagulation might reduce the incidence of complications and lead to better postoperative outcomes.

Pharmacokinetic Modeling Using Real-World Data to Optimize Unfractionated Heparin Dosing in Pediatric Patients on Extracorporeal Membrane Oxygenation and Evaluate Target Achievement-Clinical Outcomes Relationship

Unfractionated heparin (UFH) is a commonly used anticoagulant for pediatric patients undergoing extracorporeal membrane oxygenation (ECMO), but evidence is lacking on the ideal dosing. We aimed to (1) develop a population pharmacokinetic (PK) model for UFH, measured through anti-factor Xa assay; (2) optimize UFH starting infusions and dose titrations through simulations; and (3) explore UFH exposure-clinical outcomes relationship. Data from 218 patients admitted to Utah's Primary Children's Hospital were retrospectively collected. A 1-compartment PK model with time-varying clearance (CL) adequately described UFH PK. Weight on CL and volume of distribution and ECMO circuit change on CL were significant covariates. The typical estimates for initial CL and first-order rate constant to reach steady-state CL were 0.57 L/(h·10 kg) and 0.02/h. Comparable to non-ECMO patients, the typical steady-state CL was 0.81 L/(h·10 kg). Simulations showed that a 75 IU/kg UFH bolus dose followed by starting infusions of 25 and 20 IU/h/kg for patients aged younger than 6 years and 6 years or older, respectively, achieved the therapeutic target in 56.6% of all patients, whereas only 3.1% exceeded the target. The proposed UFH titration schemes achieved the target in more than 90% of patients while less than 0.63% were above the target after 24 and 48 hours of treatment. The median intensive care unit survival time in patients within and below the target at 24 hours was 136 and 66 hours, respectively. In conclusion, PK model of UFH was developed for pediatric patients on ECMO. The proposed UFH dosing scheme attained the anti-factor Xa target rapidly and safely.

Anticoagulants in adult extracorporeal membrane oxygenation: alternatives to standardized anticoagulation with unfractionated heparin

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a vital technique for severe respiratory or heart failure patients. Bleeding and thrombotic events are common during ECMO and negatively impact patient outcomes. Unfractionated heparin is the primary anticoagulant, but its adverse effects limit its use, necessitating alternative anticoagulants.

OBJECTIVE

Review available alternative anticoagulants for adult ECMO patients. Explore potential novel anticoagulants for future ECMO use. Aim to reduce complications (bleeding and thrombosis) and improve safety and efficacy for critically ill ECMO patients.

METHODS

Comprehensive literature review of existing and emerging anticoagulants for ECMO.

RESULTS

Identified a range of alternative anticoagulants beyond unfractionated heparin. Evaluated their potential utility in mitigating ECMO-related complications.

CONCLUSION

Diverse anticoagulant options are available and under investigation for ECMO. These alternatives may enhance patient safety and outcomes during ECMO support. Further research and clinical studies are warranted to determine their effectiveness and safety profiles.

Differential Neutralization of Unfractionated Heparin and Enoxaparin by Andexanet Alfa

INTRODUCTION

Andexanet alfa (andexanet) is an approved antidote used to reverse the bleeding effects of Direct Oral Anticoagulant (Direct-Xa agents) agents because it reverses anti-Xa activity. Unfractionated heparin (UFH) and low molecular weight heparins (LMWHs) exhibit anti-Xa activity. The purpose is to investigate the neutralization of UFH and LMWH by andexanet in activated clotting time (ACT), thrombelastography (TEG), and anti-Xa due to the protamine sulfate shortage.

METHODS

UFH and LMWH were studied with andexanet, PS, or saline as potential reversal agents/controls at varying concentrations in ACT, TEG, and anti-Xa and compared to each other.

RESULTS

Andexanet partially neutralized both drugs several TEG parameters at high andexanet concentrations, but it was not as effective as protamine sulfate in any of the assays used. Most TEG parameters were correlated with andexanet concentration. In ACT, significant neutralization was demonstrated at many andexanet concentrations for UFH, but not LMWH. UFH was completely neutralized by PS in ACT, while LMWH was partially neutralized by PS in ACT. Andexanet alfa was a less effective neutralization agent than the protamine sulfate as it only partially neutralized UFH in ACT and was ineffective at neutralizing LMWH when tested at the same concentration as PS (10 ug/mL).

CONCLUSION

Andexanet partially neutralized UFH and LMWH with variability between assays, necessitating investigation into assay-dependent differences.

Reassessing the Pediatric Dosing Recommendations for Unfractionated Heparin Using Real-World Data: a Pharmacokinetic-Pharmacodynamic Modeling Approach

Optimal pediatric dosing of unfractionated heparin (UFH) is challenging due to paucity of clinical outcome and pharmacokinetic-pharmacodynamic (PK/PD) studies in pediatrics. This study aimed to: (i) develop a PK/PD model for UFH, quantified by anti-factor Xa assay and the UFH effect measured by activated partial thromboplastin time (aPTT) (ii) evaluate pediatric UFH infusions in achieving anti-factor Xa (0.3 - 0.7 IU/mL) therapeutic target by simulations. Electronic health record data were retrospectively collected from 633 patients < 19 years old admitted to Texas Children's Hospital. The PK/PD model was developed using a 70% (training)-30% (test) data split approach. A one-compartment PK model with linear elimination adequately described the UFH PK. An allometrically scaled body weight on clearance (CL) and volume of distribution (Vd) with an age-dependent maturation function of extracellular water on Vd were the covariates identified. Comparable with literature, the typical values for CL and Vd were 3.28 L/(hr·50 kg) and 8.83 L/50 kg, respectively. A linear model adequately described the UFH-aPTT relationship with an estimated slope of 150. Simulations of the currently recommended starting infusions (28 IU/hr/kg for pediatrics < 1 year old or 20 IU/hr/kg for pediatrics > 1 year old) showed that anti-factor Xa therapeutic target was achieved only in 15.3%, 14.6%, 36.9% and 45.11% of subjects in the age groups of < 1 year, 1-6 years, 6-12 years, and 12-19 years, respectively. In conclusion, the UFH anti-factor Xa target is not achieved initially especially in young pediatrics, suggesting the need to optimize UFH dosing to achieve higher therapeutic success. This article is protected by copyright. All rights reserved.

Systematic review of machine learning models for personalised dosing of heparin

AIM

To identify and critically appraise studies of prediction models, developed using machine learning (ML) methods, for determining the optimal dosing of unfractionated heparin (UFH).

METHODS

Embase, PubMed, CINAHL, Web of Science, International Pharmaceutical Abstracts and IEEE Xplore databases were searched from inception to 31 January 2020 to identify relevant studies using key search terms synonymous with artificial intelligence or ML, 'prediction', 'dose', 'activated partial thromboplastin time (aPTT)' and 'UFH.' Studies had to have used ML methods for developing models that predicted optimal dose of UFH or target therapeutic aPTT levels in the hospital setting. The CHARMS Checklist was used to assess quality and risk of bias of included studies.

RESULTS

Of 8393 retrieved abstracts, 61 underwent full text review and eight studies met inclusion criteria. Four studies described models for predicting aPTT, three studies described models predicting optimal dose of heparin during dialysis and one study described a model that used surrogate outcomes of clotting and bleeding to predict a therapeutic aPTT. Studies varied widely in reporting of study participants, feature characterisation and selection, handling of missing data, sample size calculations and the intended clinical application of the model. Only one study conducted an external validation and no studies evaluated model impacts in clinical practice.

CONCLUSION

Studies of ML models for UFH dosing are few and none report a model ready for routine clinical use. Existing studies are limited by low methodological quality, inadequate reporting of study factors and absence of external validation and impact analysis.

Unfractionated heparin inhibits live wild type SARS-CoV-2 cell infectivity at therapeutically relevant concentrations

BACKGROUND AND PURPOSE

Currently, there are no licensed vaccines and limited antivirals for the treatment of COVID-19. Heparin (delivered systemically) is currently used to treat anticoagulant anomalies in COVID-19 patients. Additionally, in the United Kingdom, Brazil and Australia, nebulised unfractionated heparin (UFH) is being trialled in COVID-19 patients as a potential treatment. A systematic comparison of the potential antiviral effect of various heparin preparations on live wild type SARS-CoV-2, in vitro, is needed.

EXPERIMENTAL APPROACH

Seven different heparin preparations including UFH and low MW heparins (LMWH) of porcine or bovine origin were screened for antiviral activity against live SARS-CoV-2 (Australia/VIC01/2020) using a plaque inhibition assay with Vero E6 cells. Interaction of heparin with spike protein RBD was studied using differential scanning fluorimetry and the inhibition of RBD binding to human ACE2 protein using elisa assays was examined.

KEY RESULTS

All the UFH preparations had potent antiviral effects, with IC₅₀ values ranging between 25 and 41 μg·ml^-1 , whereas LMWHs were less inhibitory by ~150-fold (IC₅₀ range 3.4-7.8 mg·ml^-1 ). Mechanistically, we observed that heparin binds and destabilizes the RBD protein and furthermore, we show heparin directly inhibits the binding of RBD to the human ACE2 protein receptor.

CONCLUSION AND IMPLICATIONS

This comparison of clinically relevant heparins shows that UFH has significantly stronger SARS-CoV-2 antiviral activity compared to LMWHs. UFH acts to directly inhibit binding of spike protein to the human ACE2 protein receptor. Overall, the data strongly support further clinical investigation of UFH as a potential treatment for patients with COVID-19.

Unfractionated heparin inhibits live wild type SARS-CoV-2 cell infectivity at therapeutically relevant concentrations

BACKGROUND AND PURPOSE

Currently, there are no licensed vaccines and limited antivirals for the treatment of COVID-19. Heparin (delivered systemically) is currently used to treat anticoagulant anomalies in COVID-19 patients. Additionally, in the United Kingdom, Brazil and Australia, nebulised unfractionated heparin (UFH) is being trialled in COVID-19 patients as a potential treatment. A systematic comparison of the potential antiviral effect of various heparin preparations on live wild type SARS-CoV-2, in vitro, is needed.

EXPERIMENTAL APPROACH

Seven different heparin preparations including UFH and low MW heparins (LMWH) of porcine or bovine origin were screened for antiviral activity against live SARS-CoV-2 (Australia/VIC01/2020) using a plaque inhibition assay with Vero E6 cells. Interaction of heparin with spike protein RBD was studied using differential scanning fluorimetry and the inhibition of RBD binding to human ACE2 protein using elisa assays was examined.

KEY RESULTS

All the UFH preparations had potent antiviral effects, with IC₅₀ values ranging between 25 and 41 μg·ml^-1 , whereas LMWHs were less inhibitory by ~150-fold (IC₅₀ range 3.4-7.8 mg·ml^-1 ). Mechanistically, we observed that heparin binds and destabilizes the RBD protein and furthermore, we show heparin directly inhibits the binding of RBD to the human ACE2 protein receptor.

CONCLUSION AND IMPLICATIONS

This comparison of clinically relevant heparins shows that UFH has significantly stronger SARS-CoV-2 antiviral activity compared to LMWHs. UFH acts to directly inhibit binding of spike protein to the human ACE2 protein receptor. Overall, the data strongly support further clinical investigation of UFH as a potential treatment for patients with COVID-19.

Risk Prediction and New Prophylaxis Strategies for Thromboembolism in Cancer

In the general population, the incidence of thromboembolic events is 117 cases/100,000 inhabitants/year, while in cancer patient incidence, it is four-fold higher, especially in patients who receive chemotherapy and who are affected by pancreatic, lung or gastric cancer. At the basis of venous thromboembolism (VTE) there is the so-called Virchow triad, but tumor cells can activate coagulation pathway by various direct and indirect mechanisms, and chemotherapy can contribute to VTE onset. For these reasons, several studies were conducted in order to assess efficacy and safety of the use of anticoagulant therapy in cancer patients, both in prophylaxis setting and in therapy setting. With this review, we aim to record principal findings and current guidelines about thromboprophylaxis in cancer patients, with particular attention to subjects with additional risk factors such as patients receiving chemotherapy or undergoing surgery, hospitalized patients for acute medical intercurrent event and patients with central venous catheters. Nonetheless we added a brief insight about acute and maintenance therapy of manifested venous thromboembolism in cancer patients.

Vascular adhesion protein-1 in hemodialysis and hemodiafiltration patients: effect of single hemodialysis session on its level in regard to type of anticoagulant

PURPOSE

Traditional anticoagulants used in intermittent hemodialysis (HD) are unfractionated heparin (UFH) and increasingly low molecular weight heparins (LMWHs). Repeated and prolonged exposure to UFH and/or LMWHs may further disturb hemostasis in uremic patients. Vascular adhesion protein-1 (VAP-1) is secreted by vascular smooth muscle cells, adipocytes and endothelial cells with functional monoamine oxidase activity and is elevated in atherosclerosis, diabetes mellitus and obesity. The aim of this study was to assess the effects of UFH and LMWHs on VAP-1 concentration in HD patients. The effects on single HD session on VAP-1 were also evaluated as well as VAP-1 levels in regard to type of renal replacement therapy.

METHODS

We studied 82 hemodialyzed patients (mean age 63 years, dialysis vintage 59 months) and 17 patients treated by means of hemodiafiltration (HDF) (mean age 59 years, HD vintage 84 months, HDF 7 months). Patients were anticoagulated with enoxaparin (n = 46), dalteparin (n = 10), nadroparin (n = 6) or UFH (n = 20) during their HD sessions. VAP-1 was assessed using kits from BioVendor, Modrice, Czech Republic.

RESULTS

Patients on HDF had significantly lower VAP-1 when compared with HD patients. We found that VAP-1 concentration in patients dialyzed by using LMWH or UFH was similar. There was no effect on HD session on VAP-1 concentration. Diabetic patients had higher serum VAP-1 than non-diabetic.

CONCLUSIONS

HDF is associated with lower VAP-1 levels indicating less pronounced endothelial cell injury than hemodialysis. Type of heparin seems to have no effect on VAP-1 levels in hemodialyzed patients. However, the cross-sectional but not prospective design is a limitation of this study.

Heparin: Past, Present, and Future

Heparin, the most widely used anticoagulant drug in the world today, remains an animal-derived product with the attendant risks of adulteration and contamination. A contamination crisis in 2007-2008 increased the impetus to provide non-animal-derived sources of heparin, produced under cGMP conditions. In addition, recent studies suggest that heparin may have significant antineoplastic activity, separate and distinct from its anticoagulant activity, while other studies indicate a role for heparin in treating inflammation, infertility, and infectious disease. A variety of strategies have been proposed to produce a bioengineered heparin. In this review, we discuss several of these strategies including microbial production, mammalian cell production, and chemoenzymatic modification. We also propose strategies for creating "designer" heparins and heparan-sulfates with various biochemical and physiological properties.

Pregnancy Outcome in Women with Mechanical Prosthetic Heart Valves Treated with Unfractionated Heparin (UFH) or Enoxaparin

OBJECTIVE

This study was carried out to determine the maternal (including thromboembolic and hemorrhagic complications) and fetal outcomes (including miscarriage, stillbirth, baby death, and live birth) in women with mechanical heart valves managed with therapeutic doses of unfractionated heparin (UFH) versus enoxaparin during pregnancy.

METHODS

This is a prospective comparative, nonrandomized study. Pregnant women with mechanical heart valves presenting to high-risk pregnancy unit of Benha University Hospital, Egypt were treated with UFH 15,000 U/12 h versus enoxaparin (Clexane) 1 mg/kg SC/12 h during pregnancy and the results were analyzed.

RESULTS

40 pregnant women were included in the study. In 20 pregnant women, anticoagulation was with UFH, and 20 pregnant women received enoxaparin. One (3 %) thrombotic complication occurred with enoxaparin treatment. Noncompliance or subtherapeutic levels contributed to this outcome in this case. Antenatal hemorrhage occurred in 4 (10 %) and postpartum hemorrhagic complications in 5 (12.5 %) pregnancies. Of the 32 pregnant women who continued after 20 weeks' gestation, 100 % (17/17) of the women taking predominantly UFH had a surviving infant compared with 93 % (14/15) of the women taking primarily enoxaparin (p = 0.25). One intrauterine fetal death occurred in the enoxaparin group. There was no significant difference in the live birth rates between the two groups (p = 0.31).

CONCLUSIONS

Compliance with therapeutic dose of UFH during pregnancy in women with mechanical heart valves is associated with a low risk of valve thrombosis and good fetal outcomes, but meticulous monitoring is essential.

Perioperative venous thromboembolism in patients with gynecological malignancies: a lesson from four years of recent clinical experience

AIM

To analyze clinical characteristics of venous thromboembolisms (VTE) in gynecological malignancies, and to find a cost-effective prophylaxis procedure for post-operative VTE.

PATIENTS AND METHODS

We analyzed clinical characteristics of 751 patients who underwent definitive surgery for gynecologic malignancies, and cost-effectiveness of VTE prophylaxis.

RESULTS

VTE was diagnosed preoperatively in 4.5% of ovarian cancer cases, more frequently than any other type (p<0.005). Older age and greater length of operation were independent risk factors for postoperative VTE. To prevent eight VTEs in 738 malignant cases, which occurred during day 2 to 10, $617,783, $726,185, or $994,222 were necessary for continuous VTE prophylaxis, using either unfractionated heparin (UFH), low-molecular weight heparin or fondaparinux, respectively.

CONCLUSION

A strategy which might be cost-effective for post-surgical management of gynecological malignances is use of UFH three times combined with graduated compression stockings and intermittent pneumatic compression, thorough SpO2 monitoring, and perioperative measurements of the circumference of both sides of thighs and calves.

Effects of unfractionated heparin on renal osteodystrophy and vascular calcification in chronic kidney disease rats

Unfractionated heparin (UFH) is the most widely used anticoagulant in hemodialysis for chronic kidney disease (CKD) patients. Many studies have verified that UFH can induce bone loss in subjects with normal bone, but few have focused on its effect on renal osteodystrophy. We therefore investigated this issue in adenine-induced CKD rats. As CKD also impairs mineral metabolism systemically, we also studied the impacts of UFH on serum markers of CKD-mineral and bone disorder (CKD-MBD) and vascular calcification. We administered low and high doses of UFH (1U/g and 2U/g body weight, respectively) to CKD rats and compared them with CKD controls. At sacrifice, the serum markers of CKD-MBD did not significantly differ among the two UFH CKD groups and the CKD control group. The mean bone mineral densities (BMDs) of the total femur and a region of interest (ROI) constituted of trabecular and cortical bone were lower in the high-dose UFH (H-UFH) CKD group than in the CKD control group (P<0.05 and P<0.01, respectively). The BMD of the femoral ROI constituted of cortical bone did not differ between the H-UFH CKD group and the CKD control group. Histomorphometrical changes in the CKD rats indicated secondary hyperparathyroidism, and the femoral trabecular bone volume, but not cortical bone volume, significantly decreased with increasing UFH dose. The same decreasing trend was found in osteoblast parameters, and an increasing trend was found in osteoclast parameters; however, most differences were not significant. Moreover, no distinct statistical differences were found in the comparison of vascular calcium or phosphorus content among the CKD control group and the two UFH CKD groups. Therefore, we concluded that UFH could induce bone loss in CKD rats with secondary hyperparathyroidism, mainly by reducing the trabecular volume and had little effect on cortical bone volume. The underlying mechanism might involve inhibition of osteoblast activity and promotion of osteoclast activity by UFH. We did not find any effect of UFH on vascular calcification in CKD rats with secondary hyperparathyroidism.

Postpartum wound and bleeding complications in women who received peripartum anticoagulation

INTRODUCTION

The objective of this study was to compare wound and bleeding complications between women who received anticoagulation after cesarean delivery due to history of prior venous thromboembolic disease, arterial disease, or being a thrombophilia carrier with adverse pregnancy outcome, to women not receiving anticoagulation.

METHODS

Women in the Duke Thrombosis Center Registry who underwent cesarean delivery during 2003-2011 and received postpartum anticoagulation (anticoagulation group, n=77), were compared with a subset of women who delivered during the same time period, but did not receive anticoagulation (no anticoagulation group, n=77). The no anticoagulation group comprised women who were matched to the anticoagulation group by age, body mass index, type of cesarean (no labor vs. labor), and date of delivery. Bleeding and wound complications were compared between the two groups. A multivariable logistic regression model was constructed to determine if anticoagulation was an independent predictor of wound complication.

RESULTS

Women who received anticoagulation during pregnancy had a greater incidence of wound complications compared to those who did not (30% vs. 8%, p<0.001). Using multivariable logistic regression, while controlling for race, diabetes, chorioamnionitis, and aspirin use, anticoagulation predicted the development of any wound complication (OR 5.8, 95% CI 2.2, 17.6), but there were no differences in the mean estimated blood loss at delivery (782 vs. 778 ml, p=0.91), change in postpartum hematocrit (5.4 vs. 5.2%, p=0.772), or percent of women receiving blood products (6.5 vs. 1.3%, p=0.209) between the two groups.

CONCLUSIONS

Anticoagulation following cesarean delivery is associated with an increased risk of post-cesarean wound complications, but not other postpartum bleeding complications.

Ultrasonic-assisted preparation of a low molecular weight heparin (LMWH) with anticoagulant activity

Low molecular weight heparin (LMWH) is currently used as an anticoagulant agent and constitutes an alternative to unfractionated heparin, which is the cause of serious adverse drug reaction such as heparin-induced thrombocytopenia (HIT). Commercially available LMWH is produced by enzymatic depolymerization that is costly or by chemical methods that are generally carried out under conditions that could imply side reactions that reduce final product efficiency and yields. In this work, we present the use of a physicochemical method for the production of LMWH. This method consists in the use of hydrogen peroxide-catalyzed radical hydrolysis assisted by ultrasonic waves. LMWH that are produced using this physicochemical method have an average molecular weight and anticoagulant properties (Anti-Xa and Anti-IIa) that are comparable to some of commercial LMWH that are currently used. Ultrasonic-assisted radical depolymerization of heparin leads to products with a remarkably low polydispersity index. Moreover, in comparison to other LMWH such as those produced by enzymatic β-elimination, this physicochemical depolymerization of heparin induces fewer oligosaccharides with less than five monosaccharide units. This contributes to the better preservation of the ATIII pentasaccharide binding sequence, which results in a high Anti-Xa/Anti-IIa ratio (1.86). However, LMWH obtained using this physicochemical method have a lower degree of sulfation than other LMWH, which seems to be the cause of a lower Anti-Xa and Anti-IIa activity (143.62±5.42 and 77.07±4.4, respectively).