Heparinization for routine hemodialysis

Synthesis of bioengineered heparin chemically and biologically similar to porcine-derived products and convertible to low MW heparin

Heparins have been invaluable therapeutic anticoagulant polysaccharides for over a century, whether used as unfractionated heparin or as low molecular weight heparin (LMWH) derivatives. However, heparin production by extraction from animal tissues presents multiple challenges, including the risk of adulteration, contamination, prion and viral impurities, limited supply, insecure supply chain, and significant batch-to-batch variability. The use of animal-derived heparin also raises ethical and religious concerns, as well as carries the risk of transmitting zoonotic diseases. Chemoenzymatic synthesis of animal-free heparin products would offer several advantages, including reliable and scalable production processes, improved purity and consistency, and the ability to produce heparin polysaccharides with molecular weight, structural, and functional properties equivalent to those of the United States Pharmacopeia (USP) heparin, currently only sourced from porcine intestinal mucosa. We report a scalable process for the production of bioengineered heparin that is biologically and compositionally similar to USP heparin. This process relies on enzymes from the heparin biosynthetic pathway, immobilized on an inert support and requires a tailored N-sulfoheparosan with N-sulfo levels similar to those of porcine heparins. We also report the conversion of our bioengineered heparin into a LMWH that is biologically and compositionally similar to USP enoxaparin. Ultimately, we demonstrate major advances to a process to provide a potential clinical and sustainable alternative to porcine-derived heparin products.

The effects of medium cut-off and high-flux membranes on activated clotting time of patients on hemodialysis

Introduction

The interaction between blood and dialysis membrane increases the risk of clot formation. Membrane properties can interfere with coagulation activation during dialysis. Heparin is usually used to ensure anticoagulation, which can be monitored by the Activated Clotting Time (ACT) test. The purpose of this study was to compare the ACT of patients with chronic kidney disease (CKD) undergoing hemodialysis with high-flux (HF) and medium cut-off (MCO) membranes.

Methods

This is a prospective, randomized, crossover study in which 32 CKD patients were dialyzed for 12 weeks with each membrane. Blood clotting measured by ACT was evaluated at the beginning, 2nd, and 4th hour of the dialysis session. Throughout the study, there were no changes in the dose or administration method of heparin.

Results

Patients mainly were middle-aged, non-black males on hemodialysis for eight years. Before randomization, ACT values were 132 ± 56, 195 ± 60, and 128 ± 32 seconds at pre-heparinization, 2nd and 4th hour, respectively. After 12 weeks, ACT values in HF and MCO groups were 129 ± 17, 205 ± 65 and 139 ± 38 seconds, and 143 ± 54, 219 ± 68 and 142 ± 45 seconds, respectively. An ANOVA model adjusted and unadjusted for repeated measures showed a significant time but no treatment or interaction effects. In an additional paired-sample analysis, no difference between ACT values of HF and MCO Groups was observed.

Discussion and Conclusion

There was no difference regarding the ACT test during dialysis therapy using HF or MCO membranes. This data suggests that no adjustment in the dose or administration method of heparin is necessary with the use of MCO dialysis membranes.

Clinical outcomes of COVID-19 in hemodialysis patients in the city of Zonguldak, Turkey

Purpose

Patients on maintenance hemodialysis are vulnerable to viral infections like COVID-19 because of the low chance of obedience and complying with rules besides the need for transfer to distant dialysis facilities. We investigated the impact and clinical effect of treatment of COVID-19 in dialysis patients.

Methods

We included patients on maintenance hemodialysis at different healthcare facilities in Zonguldak city. With the diagnosis of the first infected HD case, all other patients who shared the same session were screened. Hospitalized and clinically confirmed cases were included. COVID-19 diagnosis was made based on clinical, biochemical along radiologic findings.

Results

34 (F/M:19/15, mean age 62 ± 13.2 years, dialysis duration 66.9 ± 57.7 months, length of hospital stay 16.2 ± 7.9 days) were diagnosed with COVID-19 infection. The prevalence of COVID-19 was found to be 18.4% of our exposed population. 38.2% of our patients were initially diagnosed by CT screening while asymptomatic. 35.3% had a fever as the first presenting symptom. Lymphopenia was the most common laboratory finding. Except for one, all had at least one comorbidity. Out of 12 (35.3%) patients admitted to ICU 6(17.6%) died. The deceased patients were older, presented with lower serum albumin and lymphocyte count, and had higher CRP and fibrinogen levels. High CRP level on admission was the only significant predictor of mortality.

Conclusion

Early detection will lower mortality. In this study, with a low prevalence of COVID-19, the importance of early screening of both symptomatic and asymptomatic patients was shown to be highly important. Further studies are still needed to find out the most appropriate medical management.

Fibrin Matrices as (Injectable) Biomaterials: Formation, Clinical Use, and Molecular Engineering

This review focuses on fibrin, starting from biological mechanisms (its production from fibrinogen and its enzymatic degradation), through its use as a medical device and as a biomaterial, and finally discussing the techniques used to add biological functions and/or improve its mechanical performance through its molecular engineering. Fibrin is a material of biological (human, and even patient's own) origin, injectable, adhesive, and remodellable by cells; further, it is nature's most common choice for an in situ forming, provisional matrix. Its widespread use in the clinic and in research is therefore completely unsurprising. There are, however, areas where its biomedical performance can be improved, namely achieving a better control over mechanical properties (and possibly higher modulus), slowing down degradation or incorporating cell-instructive functions (e.g., controlled delivery of growth factors). The authors here specifically review the efforts made in the last 20 years to achieve these aims via biomimetic reactions or self-assembly, as much via formation of hybrid materials.

Effect of Heparin on Coagulation Tests: A Comparison of Continuous and Bolus Infusion in Haemodialysis Patients

INTRODUCTION

Haemodialysis is one of the most conventional treatments of chronic renal failure. The risk of clot formation is high during haemodialysis due to regular contact of blood with the surfaces of foreign objects such as catheters, dialyzers' membrane, and other materials used for dialysis. Therefore, to prevent clot formation during haemodialysis, the dialysis system requires anticoagulation; this is usually done by heparin.

AIM

The present study aimed to compare two heparinization methods and determine the proper impacts of these methods.

MATERIALS AND METHODS

In this quasi-experimental study, 80 haemodialysis patients covered by the dialysis center of Amir-al-momenin Hospital of Zabol were studied in two 40-member groups of heparin therapy methods of bolus injection and continuous infusion. PT and PTT were measured in blood samples collected from all patients before starting haemodialysis. The first group received 3000 units of heparin once the haemodialysis machine started to work and 2000 units of heparin two hours later as bolus injection. In the second group, 1500 units of heparin was injected at the start of dialysis after then, 5000 units of heparin (one mL) were mixed with 11 mL of distilled water and infused using a heparin injection pump up to half an hour before the end of dialysis. At 30 minutes after starting dialysis and at the end of 4 hours of haemodialysis, PT and PTT were measured and compared between the two groups.

RESULTS

According to the results, the mean partial thromboplastin time in the bolus and continuous heparin-receiving group was 41.75±6.29 and 37.90±4.77, respectively, which was statistically significant (p=0.036). But PT was 14.45±1.82 in the bolus heparin group and 13.95±1.39 in the continuous heparin group, which was not significant according to the results of independent t-test (p=0.336).

CONCLUSION

The results indicated a statistically significant difference between the bolus heparin injection and the continuous heparin infusion groups in terms of coagulation tests in haemodialysis patients (p=0.036). Therefore, given the effects of heparin on coagulation, it was more effective in the bolus heparin group than the continuous infusion group. It is recommended to use the bolus method for heparin therapy during haemodialysis.

Improved dialyzer reuse after use of a population pharmacodynamic model to determine heparin doses

Anticoagulation with heparin is performed to prevent clotting during dialysis. However, heparin doses are usually determined empirically, and dialyzer clotting is a common reason for discarding reused dialyzers. We hypothesized that using a population pharmacodynamic model to determine individual heparin doses would improve dialyzer reuse rates. A previously published model was used to determine the loading dose and infusion rate of heparin needed to increase the intradialytic whole-blood clotting time to 150% of the predialysis value. The effectiveness of the model was assessed by comparing dialyzer reuse rates and delivered Kt/V(urea) before and after implementation of the model in 22 chronic hemodialysis patients. As an additional control, a similar group of 22 patients were followed up during the same period without adjustment of their heparin doses. Implementation of the model resulted in no change in the average loading dose (2,382 +/- 628 versus 2,425 +/- 908 IU; P = not significant) or average infusion rate (1,398 +/- 367 versus 1,393 +/- 532 IU/h; P = not significant) of heparin. However, individual patients required changes in loading dose or infusion rate. Dialyzer reuse rates increased significantly over time in the treatment group but remained unchanged in the control group (P < 0.003). Kt/V(urea) remained unchanged throughout the study period in both patient groups. From these data, we conclude that the use of a heparin model can improve dialyzer reuse rates without compromising the delivered dose of dialysis.

Effect of anticoagulation on blood membrane interactions during hemodialysis

BACKGROUND

Adequate anticoagulation is a precondition to prevent extracorporeal blood clotting and to improve biocompatibility during hemodialysis. In this study, we performed a morphologic analysis by using scanning electron microscopy to compare three modes of anticoagulation-conventional unfractionated heparin (UFH), low molecular weight heparin (LMWH; dalteparin sodium), or sodium citrate during hemodialysis-on membrane-associated coagulation activation.

METHODS

Fifteen patients on regular hemodialysis therapy were investigated. Five patients received UFH, five patients LMWH, and five patients sodium citrate as an anticoagulant during a standardized hemodialysis protocol using a single-use polysulfone capillary dialyzer. Membrane-associated clotting was evaluated using a scanning electron microscope. A dialyzer clotting score was used for quantitative description of coagulation activation on membrane segments.

RESULTS

Using UFH as an anticoagulant revealed the most pronounced cell adhesion and thrombus formation and the highest dialyzer clotting score (11.5 +/- 1.3 of a maximal 20 points). LMWH had a lower dialyzer clotting score than UFH (10.4 +/- 1.2 of 20 points). During the use of sodium citrate, a negligible thrombus formation and the lowest dialyzer clotting score (1.6 +/- 0.6 of 20 points, P < 0.05) were observed.

CONCLUSION

The results of this investigation indicate that using sodium citrate as an anticoagulant during hemodialysis induces a lower activation of coagulation than both conventional and fractionated heparin, which might contribute to an improvement of biocompatibility of hemodialysis extracorporeal circulation.

Blood flow rate: an important determinant of urea clearance and delivered Kt/V

Implementation of the Dialysis Outcomes Quality Initiative (DOQI) Guidelines for hemodialysis adequacy will necessitate an increase in delivered Kt/V for many patients. Before increasing Kt/V by prolonging the patient's treatment time, it is important to verify that the prescribed dialyzer urea clearance is being achieved. The principal determinant of dialyzer urea clearance is blood flow rate. Actual blood flow rates are frequently less than the nominal blood flow rate displayed by the dialysis machine, particularly at higher flow rates, leading to lower than expected urea clearances. The major reason for the reduction in blood flow rate is a low pressure in the arterial blood line proximal to the blood pump. This effect can be mitigated by the use of large bore access needles. For quality assurance purposes, actual blood flow rates should be determined by correcting nominal blood flow rates for pressure effects using empirical relationships or by using an ultrasonic flow meter. Because a poorly functioning blood access may further reduce the effective blood flow rate, blood access performance should also be monitored regularly.