Platelet depletion, platelet activation and coagulation during treatment with hemodialysis

Thromboelastography and Traditional Coagulation Testing in Non-ICU-Admitted Patients with Acute Kidney Injury: An Observational Cohort Study

INTRODUCTION

This study aimed to elucidate the coagulation disorders in non-ICU patients with acute kidney injury (AKI) and their contribution to clotting-related outcomes of intermittent kidney replacement therapy (KRT).

METHODS

We included non-ICU-admitted patients with AKI requiring intermittent KRT, clinically having a risk of bleeding and against systemic anticoagulant use during KRT between April and December 2018. The premature termination of treatment due to circuit clotting was considered a poor outcome. We analyzed the characteristics of thromboelastography (TEG)-derived and traditional coagulation parameters and explored the potential-affecting factors.

RESULTS

In total, 64 patients were enrolled. Hypocoagulability was detected in 4.7%-15.6% of patients by a combination of the traditional parameters, i.e., prothrombin time (PT)/international normalized ratio, activated partial PT, and fibrinogen. No patient had hypocoagulability observed on TEG-derived reaction time; only 2.1%, 3.1%, and 10.9% of patients had hypocoagulability on TEG-derived kinetic time (K-time), α-angle, and maximum amplitude (MA), respectively, which were also platelet-related coagulation parameters, despite 37.5% of the cohort having thrombocytopenia. In contrast, hypercoagulability was more prevalent, involving 12.5%, 43.8%, 21.9%, and 48.4% of patients on TEG K-time, α-angle, MA, and coagulation index (CI), respectively, although thrombocytosis was only in 1.5% of the cohort. Patients with thrombocytopenia showed lower fibrinogen level (2.6 vs. 4.0 g/L, p = 0.00), α-angle (63.5° vs. 73.3°, p = 0.00), MA (53.5 vs. 66.1 mm, p = 0.00), and CI (1.8 vs. 3.6, p = 0.00) but higher thrombin time (17.8 vs. 16.2 s, p = 0.00) and K-time (2.0 vs. 1.2 min, p = 0.00) than those with a platelet count over 100 × 109/L. 41 patients were treated with heparin-free protocol, and 23 were treated with regional citrate anticoagulation (RCA). The premature termination rate was 41.5% on heparin-free patients, while 8.7% of patients underwent an RCA protocol (p = 0.006). Heparin-free protocol was the strongest adverse factor to poor outcomes. A heparin-free subgroup analysis found that the circuit clotting risk was increased by 61.7% with a 10 × 109/L elevation in platelet count (odds ratio [OR] = 1.617, p = 0.049) and decreased by 67.5% following a second increase of PT (OR = 0.325, p = 0.041). No significant correlation was found between TEG parameters and premature circuit clotting.

CONCLUSIONS

Most non-ICU-admitted patients with AKI had normal-to-enhanced hemostasis and activated platelet function based on TEG results, as well as a high rate of premature circuit clotting when receiving heparin-free protocol despite thrombocytopenia. Further studies are needed to better determine the use of TEG in respect to management of anticoagulation and bleeding complications in AKI patients with KRT.

Hidden risks associated with conventional short intermittent hemodialysis: A call for action to mitigate cardiovascular risk and morbidity

The development of maintenance hemodialysis (HD) for end stage kidney disease patients is a success story that continues to save many lives. Nevertheless, intermittent renal replacement therapy is also a source of recurrent stress for patients. Conventional thrice weekly short HD is an imperfect treatment that only partially corrects uremic abnormalities, increases cardiovascular risk, and exacerbates disease burden. Altering cycles of fluid loading associated with cardiac stretching (interdialytic phase) and then fluid unloading (intradialytic phase) likely contribute to cardiac and vascular damage. This unphysiologic treatment profile combined with cyclic disturbances including osmotic and electrolytic shifts may contribute to morbidity in dialysis patients and augment the health burden of treatment. As such, HD patients are exposed to multiple stressors including cardiocirculatory, inflammatory, biologic, hypoxemic, and nutritional. This cascade of events can be termed the dialysis stress storm and sickness syndrome. Mitigating cardiovascular risk and morbidity associated with conventional intermittent HD appears to be a priority for improving patient experience and reducing disease burden. In this in-depth review, we summarize the hidden effects of intermittent HD therapy, and call for action to improve delivered HD and develop treatment schedules that are better tolerated and associated with fewer adverse effects.

Significance of mild thrombocytopenia in maintenance hemodialysis patients; a retrospective cohort study

Platelet activation in the hemodialysis (HD) circuit often causes thrombocytopenia. However, its clinical and pathophysiological significance has rarely been explored. Herein, we investigated the predictive value of thrombocytopenia for cardiovascular events (CVE) in maintenance HD patients and attempted to explore its mechanistic background considering recent knowledge of platelet dynamics. We conducted a retrospective cohort study on HD patients with the composite primary endpoint of predicting CVE, i.e., myocardial infarction, ischemic stroke, and cardiovascular death. Baseline clinical data were analyzed and explored. Multivariate Cox regression analysis showed that platelet decrease was independently associated with CVE. Thrombocytopenia was correlated with the disuse of antiplatelet therapy (APT) and macrocytosis. These findings are possibly associated with platelet activation and senescent hematopoiesis. The prognostic significance of thrombocytopenia was more prominent in patients undergoing APT, implying the presence of APT-resistant platelets in such patients. To fully explain these results, we hypothesized that HD-activated platelets induce the biological aging of hematopoiesis, which is presumably extramedullary in the lung, where activated platelets could deliver massive amounts of inflammatory cytokines and reactive oxidative species. This results in the production of qualitatively altered and hyper-reactive platelets, a process that could form a vicious cycle that induces CVE-associated thrombocytopenia. Further investigations focusing on the dynamics of the biological aging of platelets in HD patients are warranted.

Hypothermia causes platelet activation in the human spleen

BACKGROUND

Accidental hypothermia results in various dysfunctions in the human body. Additionally, coagulation disorder can lead to a life-threatening condition. We previously demonstrated that platelets stored in the spleen were activated and thus triggered coagulation disorder in a mouse model of hypothermia. In the present study, we wanted to investigate if this phenomenon in mice also occurs in humans as a reaction to hypothermia.

METHODS

We analyzed splenic tissue collected from 22 deceased subjects who have died from hypothermia. These samples were compared with 22 control cases not exposed to cold environment. We performed immunohistochemical staining for CD61 (a marker of all platelets) and CD62P (a marker of activated platelets). We also evaluated the morphology of platelets in the spleen with scanning electron microscopy.

RESULTS

Immunohistochemical analysis revealed no significant changes in the amounts of CD61-positive platelets between the hypothermia and control cases. However, the hypothermia cases contained abundant CD62P-positive platelets compared with those of the control cases. Immunohistochemical analysis also revealed that the activated platelets formed aggregates and adhered to splenic sinusoidal endothelial cells in the hypothermia cases. However, we observed no significant fibrin formation around the activated platelets.

CONCLUSIONS

Hypothermia resulted in splenic platelet activation, which may be used as a postmortem marker of hypothermia. The release of activated platelets from the spleen into to circulation upon rewarming may promote coagulation disturbances.

Platelet Distribution Width and Mortality in Hemodialysis Patients

Objectives

The association between platelet distribution width (PDW) and mortality in hemodialysis (HD) patients has received little attention.

Methods

We retrospectively enrolled HD patients in a single center from January 1, 2008, to December 30, 2011. The primary and secondary endpoints were all-cause and cardiovascular mortality, respectively. The association between PDW and mortality was estimated by Cox regression model.

Results

Of 496 patients, the mean age was 52.5 ± 16.6 years, and the Charlson comorbidity index was 4.39 ± 1.71. During the follow-up period of 48.8 ± 6.7 months, 145 patients (29.2%) died, including 74 (14.9%) cardiovascular deaths. 258 (52.0%) with PDW < 16.31% were in the low group and 238 (48.0%) in those with PDW ≥ 16.31% according to cut-off for all-cause mortality by receiving-operator characteristics. After adjusting for confounding factors, high PDW values were independently associated with higher risk of all-cause (hazards ratio (HR) = 1.49, 95% confidence interval (CI) 1.15-6.82) and cardiovascular deaths (HR = 2.26, 95% CI 1.44-3.63) in HD patients. When comparing with quartile 1 of PDW, quartile 4 of PDW was independently associated with a higher risk of all-cause (HR = 1.59, 95% CI 1.18-5.30) and cardiovascular deaths (HR = 2.71, 95% CI 1.49-3.76) in HD patients.

Conclusions

Baseline PDW was independently associated with all-cause and cardiovascular mortality in HD patients.

Hemodialysis Does Not Induce Detectable Activation of the Contact System of Coagulation

Introduction

Systemic anticoagulation is administered during hemodialysis to prevent clotting of the extracorporeal circuit. The role of contact system activation in thrombin generation during hemodialysis using current era dialyzer membranes is unknown.

Methods

We performed a single-center randomized crossover study. Ten patients treated with hemodialysis underwent 3 standardized hemodialysis sessions. For every patient, each session was performed with a different type of dialyzer membrane (polyphenylene [PP], polymethylmetacrylate [PMMA], polyethylenimine-coated polyacrylonitrile [AN69ST]). Blood samples were collected before and 5, 15, 30, 90, and 240 minutes after blood pump start to evaluate coagulation activation (thrombin–antithrombin complex [TAT], prothrombin fragment 1+2 [PF1+2], activated factor XII [FXIIa], kallikrein, activated factor XI [FXIa]). Plasma of healthy volunteers (n = 20) was used as a reference.

Results

Baseline TAT and PF1+2 levels were higher in hemodialysis patients compared to healthy controls (median [interquartile range] for TAT: 3.3 [2.9–4.2] vs. 2.4 [2.3–2.5] μg/l [P = 0.0002] and for PF1+2: 647 [478–737] vs. 138 [125–254] pmol/l [P < 0.0002]). Despite the use of systemic anticoagulation, TAT further increased during treatment, with the increase starting after 30 minutes (median TAT at t240: 9.0 μg/l (PP), 5.5 μg/l (PMMA), and 7.2 μg/l (AN69ST), all P < 0.05 vs. baseline). Contact system markers FXIIa and kallikrein did not differ significantly between dialysis patients and healthy controls, whereas baseline FXIa levels were significantly lower in dialysis patients compared to healthy controls (P = 0.001). Levels of all contact system markers remained unchanged during hemodialysis with all types of dialyzer membranes.

Conclusion

Routine hemodialysis using systemic heparin anticoagulation induces coagulation activation without measurable contact system activation.

Hypothermia-induced activation of the splenic platelet pool as a risk factor for thrombotic disease in a mouse model

BACKGROUND

Hypothermia, either therapeutically induced or accidental (ie, an involuntary decrease in core body temperature to <35°C), results in hemostatic disorders. However, it remains unclear whether hypothermia enhances or inhibits coagulation, especially in severe hypothermia. The present study evaluated the thrombocytic and hemostatic changes in hypothermic mice.

METHODS

C57Bl/6 mice were placed at an ambient temperature of -20°C under general anesthesia. When the rectal temperature decreased to 15°C, 10 mice were immediately euthanized, while another 10 mice were rewarmed, kept in normal conditions for 24 hours, and then euthanized. These treatments were also performed in 20 splenectomized mice.

RESULTS

The hypothermic mice had adhesion of CD62P-positive platelets with high expression of von Willebrand factor (vWF) in their spleens, while the status of the peripheral platelets was unchanged. Furthermore, the plasma levels of platelet factor 4 (PF4) and pro-platelet basic protein (PPBP), which are biomarkers for platelet degranulation, were significantly higher in hypothermic mice than in control mice, indicating that hypothermia activated the platelets in the splenic pool. Thus, we analyzed these biomarkers in asplenic mice. There was no increase in either PF4 or PPBP in splenectomized hypothermic mice. Additionally, the plasma D-dimer elevation and microthrombosis were caused in rewarmed mice, but not in asplenic rewarmed mice.

CONCLUSIONS

Our results indicate that hypothermia leads to platelet activation in the spleen via the upregulation of vWF, and this activation causes hypercoagulability after rewarming.

β-Thromboglobulin may not reflect platelet activation during haemodialysis with the HeprAN membrane

BACKGROUND

When blood passes through the extracorporeal circuit during haemodialysis (HD) undesirable effects including platelet degranulation and coagulation activation take place. β-thromboglobulin (β-TG) is a sensitive marker of platelet activation. The aim of this study was to investigate platelet degranulation and coagulation activation during HD with the heparin-coated dialysis membrane HeprAN.

METHODS

Four HD sessions were evaluated in each of 12 chronic HD patients. None of the patients used oral warfarin, other anticoagulants or antiplatelet drugs. In the first session the HeprAN membrane or a conventional polyflux membrane was used in a randomized manner and thereafter alternately in a cross-over design, and 50% of the conventional dalteparin dose was given at start of HD. Prothrombin fragment 1 + 2 (PF1 + 2), β-TG and anti-factor Xa activity were measured repeatedly.

RESULTS

No dialysis sessions were terminated early due to clotting of the extracorporeal system. Activation of intravascular coagulation as assessed by change in PF1 + 2 during 4 hours of HD was the same with the two membranes. β-TG concentration decreased significantly during 4 hours of HD with the HeprAN membrane but remained stable with the polyflux membrane.

CONCLUSION

There were no differences in clotting scores or coagulation activation with the two membranes. The decrease in β-TG during HD with the HeprAN membrane suggests β-TG to be an inferior marker of platelet degranulation when using a heparin-coated dialysis membrane. A possible mechanism for the decline in β-TG concentration may be adherence of this heparin-binding protein to the heparin-coated dialysis membrane.

Cardiovascular disease in haemodialysis: role of the intravascular innate immune system

Haemodialysis is a life-saving renal replacement modality for end-stage renal disease, but this therapy also represents a major challenge to the intravascular innate immune system, which is comprised of the complement, contact and coagulation systems. Chronic inflammation is strongly associated with cardiovascular disease (CVD) in patients on haemodialysis. Biomaterial-induced contact activation of proteins within the plasma cascade systems occurs during haemodialysis and initially leads to local generation of inflammatory mediators on the biomaterial surface. The inflammation is spread by soluble activation products and mediators that are generated during haemodialysis and transported in the extracorporeal circuit back into the patient together with activated leukocytes and platelets. The combined effect is activation of the endothelium of the cardiovascular system, which loses its anti-thrombotic and anti-inflammatory properties, leading to atherogenesis and arteriosclerosis. This concept suggests that maximum suppression of the intravascular innate immune system is needed to minimize the risk of CVD in patients on haemodialysis. A potential approach to achieve this goal is to treat patients with broad-specificity systemic drugs that target more than one of the intravascular cascade systems. Alternatively, 'stealth' biomaterials that cause minimal cascade system activation could be used in haemodialysis circuits.

In vitro shear stress-induced platelet activation: sensitivity of human and bovine blood

As platelet activation plays a critical role in physiological hemostasis and pathological thrombosis, it is important in the overall hemocompatibility evaluation of new medical devices and biomaterials to assess their effects on platelet function. However, there are currently no widely accepted in vitro test methods to perform this assessment. In an effort to develop effective platelet tests for potential use in medical device evaluation, this study compared the sensitivity of platelet responses to shear stress stimulation of human and bovine blood using multiple platelet activation markers. Fresh whole blood samples anticoagulated with heparin or anticoagulant citrate dextrose, solution A (ACDA) were exposed to shear stresses up to 40 Pa for 2 min using a cone-and-plate rheometer model. Platelet activation was characterized by platelet counts, platelet surface P-selectin expression, and serotonin release into blood plasma. The results indicated that exposure to shear stresses above 20 Pa caused significant changes in all three of the platelet markers for human blood and that the changes were usually greater with ACDA anticoagulation than with heparin. In contrast, for bovine blood, the markers did not change with shear stress stimulation except for plasma serotonin in heparin anticoagulated blood. The differences observed between human and bovine platelet responses suggest that the value of using bovine blood for in vitro platelet testing to evaluate devices may be limited.

Aspects of platelet disturbances in haemodialysis patients

Patients with mild-to-chronic kidney disease (CKD) exhibit a variety of haemostatic disorders, ranging from an increased clotting tendency and reductions in the levels of natural inhibitors of coagulation to defective fibrinolysis. In addition, platelet (PLT) abnormalities are common. In this minireview, we report on aspects of haemodialysis (HD)-induced PLT activation. It is demonstrated that PLTs from HD patients are exhausted due to repeated stimulation of HD treatment and recurrent release of PLT degranulation products. During HD, additional aberrations of the haemostatic process occur. Besides deviations of coagulation and fibrinolysis, PLT activation and a reduction in their granule content have been observed during HD treatment. As HD treatment is carried out three times per week, month after month, chronic HD patients may suffer persistently from coagulation defects and PLT disorders on top of the alterations induced by the uraemic state itself. PLT activation occurs together with thrombin and fibrin generation. However, macro fibrin depositions in clot devices are not demonstrated, microaggregates occur not only in the extracorporeal circuit (ECC) but are also present in the blood circulation. As vascular access thrombosis is a frequent complication in patients with HD treatment, it is believed that hypercoagulability could result from vascular changes combined with PLTs and activation of coagulation factors.

Coagulation activation, depletion of platelet granules and endothelial integrity in case of uraemia and haemodialysis treatment

Background

During haemodialysis (HD) treatment, increase of platelet (PLT) activation and induction of procoagulant activity is demonstrated. Although the role of the endothelium and its direct interaction with coagulation and homeostasis is known, it is not elucidated how PLT activation markers and activation of coagulation coincide with markers of endothelial integrity during HD treatment. In the present study uraemia and HD induced changes, with particular emphasis on PLT granules depletion, activation of coagulation and endothelial integrity were investigated.

Methods

To detect depletion of PLT granules, peripheral blood slide smears were screened by light microscopy for qualitative evaluation of PLT granule containing cytoplasm, as indicated by its granules staining density. Activation of coagulation was investigated by establishement of thrombin-antithrombin (TAT) and fibrinogen concentrations. To evaluate endothelial integrity proendothelin (proET-1) plasma concentrations were established.

Results

Results of our study demonstrate that proET-1 plasma concentrations were obviously increased in the subjects’ group with end-stage chronic kidney disease (CKD) and renal failure if compared with a group of apparently healthy subjects. The amount of depleted PLT granules was obviously increased in the subjects’ group with end-stage CKD if compared with the group with renal failure. Mean plasma concentrations of TAT and fibrinogen revealed results within the reference range.

Conclusions

It is demonstrated that uraemia is associated with endothelial damage and aberrations in PLT granules morphology in subjects with HD treatment. We hypothesize that increased proET-1 concentrations reflect ongoing stress on endothelial cells amongst others due to uraemia. Biomarkers like proET-1 and aberrations in PLT granules morphology assist in the early detection of procoagulant activity of the endothelium.

Electron microscopic observation in case of platelet activation in a chronic haemodialysis subject

During haemodialysis (HD), platelets (PLTs) are activated and release granule contents. As HD treatment occurs three times a week, it has been demonstrated that PLTs are exhausted due to the repetitive character of the treatment. To identify PLT depletion morphologically, PLT evaluation was performed by light microscopy and electron microscopy (EM) in a chronic HD subject and a healthy reference subject. Blood samples were taken before the start of HD treatment for measurement of PLT count, PLT volume and size parameters. Blood smears were screened by light microscopy for qualitative evaluation of PLT granule containing cytoplasm, as indicated by its staining density. Morphological PLT parameters of surface area and size of dense bodies were assessed by EM. Data were compared with results of a group of 20 chronic HD subjects and a group of 20 healthy reference subjects. With respect to the percentage of PLTs with appropriate staining density (>75%), light microscopic evaluation showed that this value (9%) was within the range of a group of chronic HD subjects, but considerably below the reference range (70%). EM evaluation revealed an average PLT surface area and dense bodies area of respectively 42% and 31%, if the healthy reference subject was set on 100%. PLTs from a chronic HD subject are considerably smaller and substantially less granular than PLTs from a healthy reference subject. These findings support the hypothesis of PLT depletion in chronic HD subjects due to frequent PLT activation and/or increased urea concentrations.