Haemostasis in cirrhosis: Understanding destabilising factors during acute decompensation

Hospitalised patients with decompensated cirrhosis are in a rebalanced haemostatic state due to a parallel decline in both pro- and anti-haemostatic pathways. However, this rebalanced haemostatic state is highly susceptible to perturbations and may easily tilt towards hypocoagulability and bleeding. Acute kidney injury, bacterial infections and sepsis, and progression from acute decompensation to acute-on-chronic liver failure are associated with additional alterations of specific haemostatic pathways and a higher risk of bleeding. Unfortunately, there is no single laboratory method that can accurately stratify an individual patient's bleeding risk and guide pre-procedural prophylaxis. A better understanding of haemostatic alterations during acute illness would lead to more rational and individualised management of hospitalised patients with decompensated cirrhosis. This review will outline the latest findings on haemostatic alterations driven by acute kidney injury, bacterial infections/sepsis, and acute-on-chronic liver failure in these difficult-to-treat patients and provide evidence supporting more tailored management of bleeding risk.

The use of a low-flux hemo-dialyzer is associated with impaired platelet aggregation in patients undergoing chronic hemodialysis

In patients with chronic hemodialysis (HD), both abnormal thrombotic and bleeding events are commonly observed. Uremic platelet dysfunction is one of the important attributing factors. Moreover, HD may also result in aggregation dysfunction of platelets during the therapeutic procedure. However, how the HD process affects platelet and coagulation function is unknown and dialyzer membrane flux could have an impact on it. We aimed to compare the impacts of low-flux and high-flux HD on the platelet function of patients undergoing chronic HD. This was a cross-sectional study conducted in the HD unit of E-Da hospital in Taiwan. A total of 78 patients with maintenance HD three times per week for more than one year, including 40 with high- and 38 with low-flux hemodialysis, were recruited. Their platelet functions were evaluated using an in vitro platelet function analyzer (PFA-100) before and after the HD session. Of the 78 patients undergoing HD, 60 (76%) had prolonged pre-dialysis collagen/epinephrine (CEPI) and collagen/adenosine diphosphate closure times. Those receiving low-flux dialyzer had a significant increase in CEPI closure time (pre-dialysis 212.3 ± 62.1 seconds. post-dialysis 241.5 ± 64.3 seconds, P = .01), but not collagen/adenosine diphosphate closure time, after HD. After adjusting confounding factors, only the low-flux dialyzer demonstrated an independent association with the prolonged CEPI closure time after HD therapy (odds ratio = 23.31, 95% CI: 1.94-280.61, P = .01). We observed that impaired platelet aggregation is prevalent in patients undergoing chronic HD. Therefore, the use of low-flux dialyzers may further worsen platelet aggregation after dialysis. Patients with uremic bleeding diathesis should take precautions. We suggest that further studies using flow cytometry should be conducted to explore the mechanism of dialysis flux and platelet activity during HD.

Sex-Related Differences in Platelet Aggregation: A Literature Review Supplemented with Local Data from a Group of Generally Healthy Individuals

The process of platelet aggregation is often influenced by several factors including sex and age. A literature review confirmed the existence of sex-related differences in platelet aggregation. Although 68 out of 78 papers found such differences, there are still some controversies regarding these differences, which can be due to multiple factors (age, trigger, concomitant disease, sample handling, etc.). These outcomes are discussed in line with novel results obtained from a local study, in which blood samples from a total of 53 overall healthy women and men with ages ranging from 20 to 66 years were collected. Aggregation was induced with seven different triggers (ristocetin, thrombin receptor activating peptide 6 [TRAP-6], arachidonic acid [AA], platelet-activating factor 16 [PAF-16], ADP, collagen, or thromboxane A₂ analog U-46619) ex vivo. In addition, three FDA-approved antiplatelet drugs (vorapaxar, ticagrelor, or acetylsalicylic acid [ASA]) were also tested. In general, women had higher aggregation responses to some agonists (ADP, TRAP), as well as lower benefit from inhibitors (ASA, vorapaxar). The aggregatory responses to AA and TRAP decreased with age in both sexes, while responses to ADP, U-46619, and PAF were affected by age only in women. In conclusion, more studies are needed to decipher the biological importance of sex-related differences in platelet aggregation in part to enable personalized antiplatelet treatment.

Evaluation of novel coagulation and platelet function assays in patients with chronic kidney disease

BACKGROUND

Hemostasis evaluation in chronic kidney disease (CKD) is critical for optimal management of thrombotic and bleeding events. Standard coagulation screens are inadequate for predicting coagulopathy in CKD.

OBJECTIVE

To evaluate hemostasis parameters in patients with different stages of CKD using novel coagulation assays.

PATIENTS/METHODS

Cross-sectional study of 30 healthy controls (HC) and 120 CKD patients (10 Stage 2, 20 Stage 3, 20 Stage 4, 20 Stage 5 not requiring renal replacement therapy, 20 transplant, 10 newly started on hemodialysis [HD], 20 established on HD). Standard laboratory tests were performed in addition to rotational thromboelastometry (ROTEM), multiple electrode aggregometry (MEA), thrombin generation assays, D-dimer, and markers of thrombogenesis (thrombin-antithrombin [TAT]), fibrinolysis, and endothelial activation (intercellular adhesion molecule-1 [ICAM-1]).

RESULTS

D-dimer, TAT, and ICAM-1 concentrations were significantly higher in patients with CKD than HC (P < .01). ROTEM maximum clot firmness was significantly higher in patients than in HC (P < .01). In CKD Stage 5 patients (pre-HD and started HD) adenosine diphosphate and thrombin receptor activating peptide MEA tests were significantly lower than HC indicating platelet aggregation defect (P < .05). Multivariate analysis confirmed the direct effect of estimated glomerular filtration rate (eGFR) in the variance of ROTEM and MEA tests. Endogenous thrombin potential and peak thrombin were not statistically different between groups, but Stage 5 CKD patients had prolonged lag time (7.91 vs. 6.33, P < .001) and time to thrombin peak (10.8 vs. 9.5, P < .05) compared to HC.

CONCLUSIONS

Patients with CKD exhibit features of concomitant hypercoagulability measured by ROTEM and platelet dysfunction measured with MEA. eGFR was an independent determinant of platelet dysfunction and hypercoagulability.

Role of Platelets in Chronic Kidney Disease

Platelet-dependent mechanisms for excessive clotting and bleeding in CKD remain undefined. Moreover, platelets' contribution to inflammation, and specifically to CKD, are equally elusive. To date, descriptions of changes in the functional properties of circulating platelets during CKD have provided confusing interpretations. Experimental approaches that can advance our understanding of platelet dysfunction in CKD are needed, and studies that provide mechanistic insights into the dynamic relationships between thrombosis, bleeding, and inflammation associated with CKD will be essential to improve clinical management and outcomes for this vulnerable population. This article summarizes existing literature characterizing platelets in CKD and identifies areas that need further investigation.

Thromboelastography versus bleeding time for risk of bleeding post native kidney biopsy

Introduction

The risk of bleeding has led to screening of the primary hemostasis before renal biopsy. A bleeding time test (BT) is considered standard practice, but reliance on this test is controversial and its benefits remain questionable. A possible alternative is thromboelastography (TEG). However, data regarding TEG in patients with renal dysfunction is limited.

Objectives

To determine TEG abnormalities and their consequences in patients who underwent a native kidney biopsy.

Methods

A retrospective study of 417 consecutive percutaneous native renal biopsies performed in our Center. If serum creatinine >1.5 mg/dL, the patient underwent either a BT test (period A, January 2015–31 December 2016) or TEG (period B, January 2017–August 2018). In patients with prolonged BT, or an abnormal low maximal amplitude (MA) parameter of TEG, or suspected clinical uremic thrombopathy, the use of desmopressin acetate (DDAVP) was considered.

Results

Most biopsies (90.6%) were done by the same dedicated radiologist. Fifty-one patients had a BT test, which was normal in all tested patients. Seventy-one patients underwent TEG, and it was abnormal in 34 of them, most patients had combined abnormalities. The only parameter related to abnormal TEG was older age (Odds Ratio 1.21 [95% CI 1.09–2.38] p = 0.04 for abnormal Kinetics; OR 1.37 (1.05–1.96) p = 0.037 for abnormal MA). Twenty-six patients (6.23%) had bleeding complications. Risk of bleeding was significantly related to age (1.4 [1.11–7.48] p = 0.04), systolic blood pressure (1.85 [1.258–9.65] p = 0.02), and serum creatinine (1.21 [1.06–3.134] p = 0.048).

Conclusions

TEG abnormalities in patients with renal dysfunction are variable and fail to predict bleeding during kidney biopsy. The decision to administer DDAVP as a preventive measure during these procedures should be based on clinical judgment only.

Primary hemostatic function in dogs with acute kidney injury

BACKGROUND

Bleeding tendencies can occur with uremia.

OBJECTIVES

To characterize primary hemostatic function in dogs with acute kidney injury (AKI).

ANIMALS

Ten dogs with International Renal Interest Society AKI grade III or above and 10 healthy controls.

METHODS

Prospective study comparing PCV, platelet count, platelet aggregometry (Multiplate), and von Willebrand factor antigen to collagen binding activity ratio (vWF:Ag:vWF:CBA) in 2 groups of dogs (AKI group versus controls). Buccal mucosal bleeding time was measured in the AKI group only. Data are presented as median [25th, 75th percentile] unless otherwise stated. Significance was set at P < .05.

RESULTS

Mean PCV was significantly lower in the AKI (34.7%; ±SD, 8.8) than in the control (46.1%; ±SD, 3.6; P < .001) group. Platelet count was significantly higher in the AKI (350.5 × 10³ /μL [301, 516]) than in the control (241 × 10³ /μL [227, 251]; P = .01) group. Collagen-activated platelet aggregometry measured as area under the curve was significantly lower in the AKI (36.9 ± 17.7) than in the control (54.9 ± 11.2; P = .05) group. vWF:Ag:vWF:CBA was significantly higher in the AKI (2.2 [1.9, 2.6]) than in the control (1.1 [1.1, 1.2]; P = .01) group. There was a strong correlation between vWF:Ag:vWF:CBA and creatinine (r = 0.859; P < .001), but no other variables.

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with AKI had decreased collagen-activated platelet aggregation and appear to have a type II von Willebrand disease-like phenotype as indicated by the high vWF:Ag:vWF:CBA.

Structure⁻Activity Relationship Study of Newly Synthesized Iridium-III Complexes as Potential Series for Treating Thrombotic Diseases

Platelets play a major role in hemostatic events and are associated with various pathological events, such as arterial thrombosis and atherosclerosis. Iridium (Ir) compounds are potential alternatives to platinum compounds, since they exert promising anticancer effects without cellular toxicity. Our recent studies found that Ir compounds show potent antiplatelet properties. In this study, we evaluated the in vitro antiplatelet, in vivo antithrombotic and structure⁻activity relationship (SAR) of newly synthesized Ir complexes, Ir-1, Ir-2 and Ir-4, in agonists-induced human platelets. Among the tested compounds, Ir-1 was active in inhibiting platelet aggregation induced by collagen; however, Ir-2 and Ir-4 had no effects even at their maximum concentrations of 50 μM against collagen and 500 μM against U46619-induced aggregation. Similarly, Ir-1 was potently inhibiting of adenosine triphosphate (ATP) release, calcium mobilization ([Ca²⁺]i) and P-selectin expression induced by collagen-induced without cytotoxicity. Likewise, Ir-1 expressively suppressed collagen-induced Akt, PKC, p38MAPKs and JNK phosphorylation. Interestingly, Ir-2 and Ir-4 had no effect on platelet function analyzer (PFA-100) collagen-adenosine diphosphate (C-ADP) and collagen-epinephrine (C-EPI) induced closure times in mice, but Ir-1 caused a significant increase when using C-ADP stimulation. Other in vivo studies revealed that Ir-1 significantly prolonged the platelet plug formation, increased tail bleeding times and reduced the mortality of adenosine diphosphate (ADP)-induced acute pulmonary thromboembolism in mice. Ir-1 has no substitution on its phenyl group, a water molecule (like cisplatin) can replace its chloride ion and, hence, the rate of hydrolysis might be tuned by the substituent on the ligand system. These features might have played a role for the observed effects of Ir-1. These results indicate that Ir-1 may be a lead compound to design new antiplatelet drugs for the treatment of thromboembolic diseases.

Thrombelastography Suggests Hypercoagulability in Patients with Renal Dysfunction and Intracerebral Hemorrhage

BACKGROUND

The objective of this study was to quantify coagulopathy using thrombelastography (TEG) in patients with renal dysfunction and intracerebral hemorrhage (ICH).

METHODS

We reviewed patients admitted with spontaneous ICH between November 2009 and May 2015. TEG was performed at the time of admission. Creatinine clearance (CCr) was calculated using the Cockroft-Gault equation. Patients were divided into 2 groups based on normal (CCr ≥ 90) or reduced renal function (CCr < 90). Multivariable regression models were conducted to compare the differences of TEG components.

RESULTS

A total of 120 patients were included in the analysis. The normal CCr group was younger (56.1 versus 62.3 years, P < .01), was more often male (73.6% versus 53.7%, P = .03), and had higher mean admission hemoglobin (14.2 versus 13.2 mEq/L, P < .01) than the reduced renal function group. The 2 groups were similar with respect to antiplatelet or anticoagulant use, coagulation studies, and baseline ICH volume. Following multivariate analysis, the reduced renal function group was found to have shorter K (1.5 versus 2.2 min, P = 004), increased angle (66 versus 62.2 degrees, P = .04), increased MA (67.3 versus 62.3, P = .02), and increased G (11.3 versus 9.9 dynes/cm², P = .04) compared with the normal group. Mortality, poor functional outcome (modified Rankin Scale score 4-6), hematoma enlargement, hospital length of stay, and surgical interventions were not different between the 2 groups.

CONCLUSIONS

Patients with ICH and reduced CCr display faster clotting rate and increased clot strength, suggesting that patients with renal dysfunction present with a relatively hypercoagulable state based on TEG parameters thought to reflect platelet activity.

Routine haemostasis testing before transplanted kidney biopsy: a cohort study

Kidney biopsy can result in bleeding complications. Prebiopsy testing using bleeding time (BT) is controversial. New whole blood haemostasis tests, such as platelet function analyser-100 (PFA-100) and multiple electrode aggregometry (MEA), might perform better. We postulated that PFA-100 would be suitable to replace BT prebiopsy. In 154 patients, transplanted kidney biopsies were performed after measurement of bleeding time, PFA-100, MEA and mean platelet volume (MPV). Bleeding outcome (haemoglobin (Hb) drop, haematuria (±bladder catheterization), ultrasound finding of a bleeding, need for (non)surgical intervention and/or transfusion) after the biopsy was correlated to each test. Male-female ratio was 2:1. 50% had a surveillance biopsy at either three or 12 months. Around 17% (had) used acetylsalicylic acid (ASA) prebiopsy. Of 17 bleeding events, one subject needed a transfusion. Most bleeding events were Hb reductions over 1 mmol/l and all resolved uneventful. BT, PFA-100, MEA and MPV did not predict a bleeding outcome; prior ASA use however could (odds ratio 3.19; 95%-CI 1.06 to 9.61). Diagnostic performance data and Bland-Altman analysis showed that BT could not be substituted by PFA-100. ASA use was the best determinant of bleeding after kidney biopsy. Routine haemostasis testing prebiopsy has no added value.

Platelet aggregometry cannot identify uremic platelet dysfunction in heart failure patients prior to cardiac surgery

BACKGROUND

Patients with heart failure often have concomitant renal disease which can result in uremic platelet dysfunction. Determining whether uremia has affected platelets by platelet aggregometry can be challenging in these patients since they are often on antiplatelet medications. This study was undertaken to determine if platelet aggregation studies could identify heart failure patients at risk for uremic bleeding prior to cardiac surgery.

METHODS

Platelet aggregation studies from three groups were studied and compared: 17 heart failure patients with mild to moderate renal impairment, 17 heart failure patients without renal abnormalities and 17 healthy volunteers.

RESULTS

Platelet aggregation was severely impaired in both heart failure groups with and without renal abnormalities compared to healthy controls, and there were no significant differences in platelet aggregation in response to any of the agonists. There was a pan-decrease in platelet aggregation to all agonists in all heart failure patients.

CONCLUSION

Platelet aggregometry does not appear to be useful in measuring platelet dysfunction in heart failure patients with mild to moderate renal impairment.

Differences in Whole Blood Platelet Aggregation at Baseline and in Response to Aspirin and Aspirin Plus Clopidogrel in Patients With Versus Without Chronic Kidney Disease

Thrombotic events while receiving antiplatelet agents (APAs) are more common in subjects with versus without chronic kidney disease (CKD). Data on antiplatelet effects of APA in CKD are scarce and limited by lack of baseline platelet function before APA treatment. We hypothesized subjects with stages 4 to 5 CKD versus no CKD have greater baseline platelet aggregability and respond poorly to aspirin and clopidogrel. In a prospective controlled study, we measured whole blood platelet aggregation (WBPA) in 28 CKD and 16 non-CKD asymptomatic stable outpatients not on APA, frequency-matched for age, gender, obesity, and diabetes mellitus. WBPA was remeasured after 2 weeks of each aspirin and aspirin plus clopidogrel. The primary outcome was percent inhibition of platelet aggregation (IPA) from baseline. The secondary outcome was residual platelet aggregability (RPA; proportion with <50% IPA). Baseline platelet aggregability was similar between groups except adenosine diphosphate-induced WBPA, which was higher in CKD versus non-CKD; median (interquartile range) = 13.5 (9.5 to 16.0) versus 9.0 (6.0 to 12.0) Ω, p = 0.007. CKD versus non-CKD participants had lower clopidogrel-induced IPA, 38% versus 72%, p = 0.04. A greater proportion of CKD versus non-CKD participants had RPA after clopidogrel treatment (56% vs 8.3%, p = 0.01). There were no significant interactions between CKD and the presence of cytochrome P450 2C19 polymorphisms for platelet aggregability in clopidogrel-treated participants. In conclusion, CKD versus non-CKD subjects exhibited similar platelet aggregation at baseline, similar aspirin effects and greater RPA on clopidogrel, which was independent of cytochrome P450 2C19 polymorphisms.

Platelet-Related Hemostasis before and after Hemodialysis with Five Different Anticoagulation Methods

Purpose

To evaluate platelet-related hemostasis during hemodialysis performed with five different anticoagulation methods.

Methods

31 chronic hemodialysis patients, 71% men, aged 57.5 ∓ 17.4 years, participated in our prospective study. Platelet function analyzer PFA -100 closure time (collagen/epinephrine -CEPI, collagen/adenosine diphosphate -CADP) was measured before and after hemodialysis, which was performed consecutively with five different anticoagulation methods: full-dose unfractionated heparin (UFH) and low-molecular weight heparin (LMWH): 31 patients, regional citrate anticoagulation (RCA): 28 patients, low-dose heparin: 25 patients and “heparin-free” dialysis: 9 patients. The degree of clotting in the dialysis system was graded on a 5 point scale.

Results

CEPI (mean ∓ SD, reference range 80-160 sec) before vs. after hemodialysis: UFH: 171.7 ∓ 62.1 vs. 170.8 ∓ 67.3; LMWH: 167.4 ∓ 56.9 vs. 159.4 ∓ 56.4; low-dose heparin: 175.3 ∓ 69.0 vs. 183.1 ∓ 60.5; RCA: 172.6 ∓ 57.4 vs. 161.6 ∓ 57.0; “heparin-free”: 181.7 ∓ 56.8 vs. 209.0 ∓ 66.5; all differences nonsignificant. CADP (mean ∓ SD, reference range: 68-121 sec) before vs. after hemodialysis: UFH: 132.0 ∓ 56.6 vs.146.3 ∓ 68.4; LMWH: 132.4 ∓ 57,0 vs. 123.1 ∓ 50.8; low-dose heparin: 137.2 ∓ 64.2 vs. 143.8 ∓ 55.5; RCA: 140.7 ∓ 48.2 vs. 132.9 ∓ 48.1; “heparin-free”: 137.1 ∓ 68.0 vs.139.2 ∓ 29.7; all differences nonsignificant. Before hemodialysis procedure CEPI was increased in 51.2% and CADP in 48.4% of the patients. The best dialysis system clotting score was found with UFH, LMWH and RCA.

Conclusions

Platelet dysfunction was demonstrated in approximately half of the chronic hemodialysis patients and was not improved after hemodialysis, regardless of the anticoagulation regimen used.

Whole blood platelet aggregation and release reaction testing in uremic patients

Background. Platelet function analysis utilizing platelet-rich plasma and optical density based aggregometry fails to identify patients at risk for uremia associated complications. Methods. We employed whole blood platelet aggregation analysis based on impedance as well as determination of ATP release from platelet granules detected by a chemiluminescence method. Ten chronic kidney disease (CKD) stage 4 or 5 predialysis patients underwent platelet evaluation. Our study aims to evaluate this platform in this patient population to determine if abnormalities could be detected. Results. Analysis revealed normal aggregation and ATP release to collagen, ADP, and high-dose ristocetin. ATP release had a low response to arachidonic acid (0.37 ± 0.26 nmoles, reference range: 0.6–1.4 nmoles). Platelet aggregation to low-dose ristocetin revealed an exaggerated response (20.9 ± 18.7 ohms, reference range: 0–5 ohms). Conclusions. Whole blood platelet analysis detected platelet dysfunction which may be associated with bleeding and thrombotic risks in uremia. Diminished ATP release to arachidonic acid (an aspirin-like defect) in uremic patients may result in platelet associated bleeding. An increased aggregation response to low-dose ristocetin (a type IIb von Willebrand disease-like defect) is associated with thrombus formation. This platelet hyperreactivity may be associated with a thrombotic diathesis as seen in some uremic patients.

Modulation of hyperthermia-induced platelet aggregation inhibition in the presence of urea

PURPOSE

This study has been conducted to evaluate the effect of urea on aggregation responses of heat-treated platelets.

MATERIALS AND METHODS

The urea was added to platelet-rich plasma (PRP) samples in final concentrations of 50 and 100 mM. PRP samples, with or without exogenous urea, were incubated at 37 °C, 39 °C and 41 °C for 90 min and then were stimulated with adenosine diphosphate (ADP) or epinephrine for measuring of platelet aggregation responses. The average reduction in aggregability of heat-treated samples with reference to mean value obtained for control samples treated at 37 °C was expressed as inhibition percentage.

RESULTS

Aggregation responses of the samples treated in the presence of 50 mM and 100 mM urea were significantly less inhibited by hyperthermia treatments compared with those treated without exogenous urea.

CONCLUSION

The results indicate that the inhibitory effect of hyperthermia on platelet aggregation responses could be significantly modulated by urea.

Monitoring of low molecular weight heparin anticoagulation during haemodialysis with a Sonoclot Analyzer

OBJECTIVES

Sonoclot was used in this study to monitor low molecular weight heparin (LMWH) during haemodialysis.

MATERIAL AND METHODS

Two different intravenous doses (standard / half-dose) of dalteparin were studied in eight patients. Blood was sampled for coagulation analyses with Sonoclot, thrombin-antithrombin (TAT) and anti-Xa. A visual fibrin deposition score (VFS) in the venous drip chamber was also evaluated.

RESULTS

All patients completed their dialysis. There was a progressive increase in TAT levels, which correlated to the dalteparin dose. Significant differences (p<0.05) were found for TAT, VFS and Sonoclot celite-activated clotting time (SonACT) between the different LMWH dosages. TAT and Sonoclot correlated to each other, but not to the VFS. SonACT was significantly increased at two hours, with the high dalteparin dose compared to the lower dose.

CONCLUSION

Both Sonoclot and TAT failed to predict the VFS. No patient had any clinical clotting events and all dialyses were completed successfully.