Hemodialysis-associated acute systemic reactions and heparin-induced thrombocytopenia

Immunologic Effects of Heparin Associated With Hemodialysis: Focus on Heparin-Induced Thrombocytopenia

Intermittent hemodialysis (HD) is almost invariably performed with heparin, and thus HD patients are at risk of developing the immune-mediated adverse effect heparin-induced thrombocytopenia (HIT), caused by anti-platelet factor 4/heparin IgG, which strongly activates platelets. HIT patients develop hypercoagulability with greatly increased risk of thrombosis, both venous and arterial. Certain HIT-associated complications are more likely to develop among HD patients, including hemofilter thrombosis despite heparin, intravascular catheter and/or arteriovenous fistula-associated thrombosis, post-heparin bolus anaphylactoid/anaphylactic reactions, and thrombotic stroke and acute limb artery thrombosis (reflecting the high frequency of underlying arteriopathy in many patients with renal failure). Management of HIT in HD usually requires use of an alternative (non-heparin) anticoagulant; for example, danaparoid sodium (outside the USA) or argatroban (USA and elsewhere). Whether heparin-grafted hemodialyzers (without systemic heparin) can be used safely in acute HIT is unknown. The HIT immune response is remarkably transient and usually not retriggered by subsequent heparin administration. Accordingly, since renal failure patients often require long-term HD, there may be the opportunity-following seroreversion (loss of platelet-activating HIT antibodies)-to restart heparin for HD, a practice that appears to have a low likelihood of retriggering HIT.

Platelets in Renal Disease

Kidney disease is a major global health concern, affecting millions of people. Nephrologists have shown interest in platelets because of coagulation disorders caused by renal diseases. With a better understanding of platelets, it has been found that these anucleate and abundant blood cells not only play a role in hemostasis, but also have important functions in inflammation and immunity. Platelets are not only affected by kidney disease, but may also contribute to kidney disease progression by mediating inflammation and immune effects. This review summarizes the current evidence regarding platelet abnormalities in renal disease, and the multiple effects of platelets on kidney disease progression. The relationship between platelets and kidney disease is still being explored, and further research can provide mechanistic insights into the relationship between thrombosis, bleeding, and inflammation related to kidney disease, and elucidate targeted therapies for patients with kidney disease.

Heparin-Immobilized Polyethersulfone for Hemocompatibility Enhancement of Dialysis Membrane: In Situ Synchrotron Imaging, Experimental, and Ex Vivo Studies

The goal of the current study is to enhance the hemocompatibility of polyethersulfone (PES) membranes using heparin immobilization. Heparin was immobilized covalently and via electrostatic interaction with the positively charged PES surface (pseudo-zwitterionic (pZW) complex) to investigate the influence of each method on the membrane hemocompatibility. In situ synchrotron radiation micro-computed tomography (SR-µCT) imaging, available at the Canadian Light Source (CLS), was used to critically assess the fibrinogen adsorption to the newly synthesized membranes qualitatively and quantitatively using an innovative synchrotron-based X-ray tomography technique. The surface roughness of the synthesized membranes was tested using atomic force microscopy (AFM) analysis. The membrane hemocompatibility was examined through the ex vivo clinical interaction of the membranes with patients' blood to investigate the released inflammatory biomarkers (C5a, IL-1α, IL-1β, IL-6, vWF, and C5b-9). The presence and quantitative analysis of a stable hydration layer were assessed with DSC analysis. Surface modification resulted in reduced surface roughness of the heparin-PES membrane. Both types of heparin immobilization on the PES membrane surface resulted in a decrease in the absolute membrane surface charge from -60 mV (unmodified PES) to -13 mV for the pZW complex and -9.16 mV for the covalently attached heparin, respectively. The loss of human serum fibrinogen (FB) was investigated using UV analysis. The PES membrane modified with the heparin pseudo-ZW complex showed increased FB retention (90.5%), while the unmodified PES membrane and the heparin covalently attached PES membrane exhibited approximately the same level of FB retention (81.3% and 79.8%, respectively). A DSC analysis revealed an improvement in the content of the hydration layer (32% of non-freezable water) for the heparin-coated membranes compared to the unmodified PES membrane (2.84%). An SR-µCT analysis showed that the method of heparin immobilization significantly affects FB adsorption distribution across the membrane thickness. A quantitative analysis using SR-µCT showed that when heparin is attached covalently, FB tends to be deposited inside the membrane pores at the top (layer index 0-40) membrane regions, although its content peak distribution shifted to the membrane surface, whereas the unmodified PES membrane holds 90% of FB in the middle (layer index 40-60) of the membrane. The ex vivo hemocompatibility study indicates an improvement in reducing the von Willebrand factor (vWF) for the heparin pseudo-ZW PES membrane compared to the covalently attached heparin and the untreated PES.