Uremic Bleeding: Closing the Circle After 30 Years of Controversies?

Prevalence and associations for abnormal bleeding times in patients with renal insufficiency

Platelet dysfunction and associated hemorrhagic complications are often encountered in patients with chronic kidney disease. This study aimed to evaluate the prevalence and associations for abnormal bleeding time (BT) in patients with renal dysfunction. Hemoglobin, hematocrit, platelet, blood urea nitrogen, creatinine, and parathyroid hormone levels were determined in 1716 patients (55.18 ± 17.19 years, men 50.8%). For these patients, BTs were estimated using a platelet function analyzer-100. Glomerular filtration rates (GFRs) were estimated using the Chronic Kidney Disease Epidemiology Collaboration equation. The study population was divided into six groups according to the estimated GFR (eGRF): group I, eGFR ≥ 90 ml/min/1.73 m(2); group II, 60 ≤ eGFR < 90 ml/min/1.73 m(2); group III, 30 ≤ eGFR < 60 ml/min/1.73 m(2); group IV, 15 ≤ eGFR < 30 ml/min/1.73 m(2); group V, eGFR < 15 ml/min/1.73 m(2); and group VI, undergoing regular hemodialysis. Renal insufficiency was defined as eGFR < 60 ml/min/1.73 m(2). To further investigate the role of inflammatory cytokines, nitric oxide (NO) and tumor necrosis factor alpha (TNF-α) were measured in a 327-patient subset of the total patient population (52.82 ± 18.3 years, men 60.9%). Abnormal BT occurred in 11.8% of group I, 15.3% of group II, 29.1% of group III, 37.5% of group IV, 35.0% of group V, and 32.1% of group VI. By Pearson correlation coefficient, eGFR (r = -0.089), hemoglobin (r = -0.127), platelet (r = -0.054) were correlated with BT. Multivariate analysis revealed that age [odds ratio (OR), 1.013; 95% CI, 1.004-1.022], renal insufficiency (eGFR < 60 ml/min/1.73 m(2); OR, 2.271; 95% CI, 1.672-3.083), anemia (hemoglobin < 120 g/l; OR, 1.486; 95% CI, 1.089-2.027), and thrombocytopenia (platelet < 150 × 10(9)/l; OR, 1.445; 95% CI, 1.089-1.918) were independently associated with prolonged BT. Plasma levels of NO and TNF-α were increased in patients with renal insufficiency (eGFR < 60 ml/min/1.73 m(2)). Plasma levels of NO in renal insufficiency group were higher in prolonged BT than those in normal BT. A significant positive correlation was noted between BTs and NO levels (r = 0.152, p = 0.009) but not with TNF-α levels. The prevalence of abnormal BTs was higher as eGFR declined. Old age, renal insufficiency, anemia, and thrombocytopenia were independent associations for abnormal BT.

Anticoagulation in intermittent hemodialysis: pathways, protocols, and pitfalls

Several methods to prevent extracorporeal circuit clotting during hemodialysis have been used in human medicine. Unfractionated (UF) heparin remains the mainstay of anticoagulant therapy in both human and veterinary intermittent hemodialysis. Different UF heparin regimes may be used depending on the bleeding risk of the patient. In patients with active bleeding or with a recent history of surgery or hemorrhagic episodes, hemodialysis may be performed without any anticoagulation or with regional anticoagulation.

Clinical Interaction between Brain and Kidney in Small Vessel Disease

Patients with chronic kidney disease (CKD) are well known to have a higher prevalence of cardiovascular disease from epidemiological studies. Recently, CKD has also been shown to be related to neurological disorders, not only ischemic brain injury but also cognitive impairment. This cerebrorenal connection is considered to involve small vessel disease in both the kidney and brain, based on their hemodynamic similarities. Clinical studies suggest that markers for CKD such as estimated glomerular filtration rate (eGFR), proteinuria, and albuminuria may be helpful to predict brain small vessel disease, white matter lesions (WMLs), silent brain ischemia (SBI), and microhemorrhages. Recently, changes in the vascular system of the brain have been shown to contribute to the onset and progression of cognitive impairment, not only vascular dementia but also Alzheimer's disease. Patients with CKD are also reported to have higher risk of impaired cognitive function in the future compared with non-CKD subjects. These results indicate that CKD markers may be helpful to predict the future risk of neuronal disease.

Association of albuminuria and reduced estimated glomerular filtration rate with incident stroke and coronary artery disease in patients with type 2 diabetes

It is unclear whether albuminuria and reduced glomerular filtration rate (GFR) independently increase the risk of incident stroke and coronary artery disease (CAD) in Japanese patients with diabetes. We investigated the independent effects of albuminuria and estimated GFR (eGFR) on the first occurrence of stroke and CAD in patients with type 2 diabetes mellitus (T2DM). We studied 1002 T2DM patients with eGFR (ml min⁻¹ per 1.73 m²) ≥15 and had no previous cardiovascular disease (CVD) history. GFR was estimated using the modified three-variable equation for the Japanese. Patients were divided into four eGFR categories: ≥90, 60-89, 30-59 and 15-29. The end point was an incident stroke and CAD events. The Cox proportional hazard model was used to calculate hazard ratio and 95% confidence interval. During a mean follow-up period of 5.2±2.1 years, 72 episodes of stroke and 90 of CAD were observed. Multivariate Cox analysis revealed no significant association between the eGFR category and incident stroke. The stroke hazard ratio (95% confidence interval) in reference to patients with an eGFR ≥90 was 0.78 (0.40-1.56) for patients with an eGFR of 60-89, 1.47 (0.70-3.10) for patients with an eGFR of 30-59 and 1.14 (0.39-3.35) for patients with an eGFR of 15-29. Reduced eGFR was a significant risk factor for CAD, with hazard ratios (95% confidence interval) for patients with an eGFRs of 60-89, 30-59 and 15-29 at 1.81 (1.01-3.57), 2.03 (1.04-4.40) and 3.01 (1.13-8.02), respectively. Reduced eGFR is independently associated with incident CAD but not stroke in Japanese patients with T2DM.

Rebalanced hemostasis in patients with liver disease: evidence and clinical consequences

Patients with liver disease frequently acquire a complex disorder of hemostasis secondary to their disease. Routine laboratory tests such as the prothrombin time and the platelet count are frequently abnormal and point to a hypocoagulable state. With more sophisticated laboratory tests it has been shown that patients with liver disease may be in hemostatic balance as a result of concomitant changes in both pro- and antihemostatic pathways. Clinically, this rebalanced hemostatic system is reflected by the large proportion of patients with liver disease who can undergo major surgery without any requirement for blood product transfusion. However, the hemostatic balance in the patient with liver disease is relatively unstable as evidenced by the occurrence of both bleeding and thrombotic complications in a significant proportion of patients. Although it is still common practice to prophylactically correct hemostatic abnormalities in patients with liver disease before invasive procedures by administration of blood products guided by the prothrombin time and platelet count, we believe that this policy is not evidence-based. In this article, we will provide arguments against the traditional concept that patients with liver failure have a hemostasis-related bleeding tendency. Consequences of these new insights for hemostatic management will be discussed.

Fibrinogen, Hematocrit, Platelets in Mild Kidney Dysfunction and the Role of Uric Acid: An Italian Male Population Study

Aim: To examine the relationship between some blood parameters and mild kidney dysfunction. Participants and Methods: A total of 719 Italian men aged 42 to 74 years from a population-based survey carried out in the town of Bollate (Milan). General linear models were used to examine the variations in plasma fibrinogen, hematocrit, platelet counts, mean platelet volume, and uric acid across levels of kidney function (estimated on the basis of glomerular filtration rate [GFR]), adjusting for age, education, smoking, alcohol consumption, physical activity (evaluated as TV watching, engaging in sport practice, and walking/cycling), waist circumference, arm muscle area, high-density lipoprotein (HDL)-cholesterol, triglycerides, hypertension, diabetes, cardiovascular disease history, and nonsteroid anti-inflammatory, diuretic, and antihypertensive drug use. Results: Plasma fibrinogen and hematocrit levels increased, and platelet counts and mean platelet volume significantly decreased as GFR fell to <80 or <70 mL/min per 1.73 m2; stratified analysis revealed an association with serum uric acid levels. Alterations compatible with an increased cardiovascular risk were particularly evident among the participants with higher uric acid levels, whereas those indicative of platelet dysfunction were found among participants with lower levels. Conclusions: Parameters affecting hemostasis and blood viscosity are altered when kidney function is only slightly reduced, and the patterns of these relationships seem to be influenced by the levels of serum uric acid, whose easy and inexpensive measurement could have prognostic value.

Treatment of bleeding in dialysis patients

Bleeding is a common and potentially serious complication of acute and chronic renal failure. The pathogenesis of bleeding in uremia is multifactorial; however, the major role is played by abnormalities in platelet-platelet and platelet-vessel wall interaction. Platelet dysfunction is partially due to uremic toxins present in circulating blood. Despite decreased platelet function, abnormalities of blood coagulation and fibrinolysis predispose the uremic patients to a hypercoagulable state carrying the risk of cardiovascular and thrombotic complications. Dialysis improves platelet abnormalities and reduces, but does not eliminate, the risk of hemorrhage. Hemodialysis can even contribute to the bleeding through the continuous platelet activation induced by the interaction between blood and artificial surfaces and the use of anticoagulants. Correction of anemia improves hemostasis in uremic patients. Therapeutic management of bleeding in patients with uremia is discussed.

Oral anticoagulant therapy in hemodialysis patients: do the benefits outweigh the risks?

Managing oral anticoagulation may be difficult in hemodialysis patients because the antithrombotic effect can be counterbalanced by an increased risk of hemorrhagic complications. There is insufficient evidence to recommend the routine use of warfarin for thrombosis prophylaxis of the vascular access in all patients. If a decision for anticoagulation is made, dosing warfarin to a "therapeutic" level is suggested, although the most appropriate target INR range remains unclear. Many hemodialysis patients with atrial fibrillation have multiple risk factors for stroke and generally benefit from warfarin, with careful and frequent laboratory monitoring. Treatment with standard dose warfarin is also recommended in patients with venous thromboembolism provided that patients do not have contraindications to anticoagulation. For those with such contraindications, placement of an inferior vena cava filter is suggested. These recommendations are limited by the almost complete lack of data in dialysis patients. Sound randomized evidence of efficacy and harm for anticoagulation in these patients will likely never be available. Knowledge of the risk of bleeding and thrombosis in anticoagulated and nonanticoagulated dialysis patients could be provided by feasible, well-designed cohort studies.

Pharmacokinetics and dosage adjustment in patients with renal dysfunction

INTRODUCTION

Chronic kidney disease is a common, progressive illness that is becoming a global public health problem. In patients with kidney dysfunction, the renal excretion of parent drug and/or its metabolites will be impaired, leading to their excessive accumulation in the body. In addition, the plasma protein binding of drugs may be significantly reduced, which in turn could influence the pharmacokinetic processes of distribution and elimination. The activity of several drug-metabolizing enzymes and drug transporters has been shown to be impaired in chronic renal failure. In patients with end-stage renal disease, dialysis techniques such as hemodialysis and continuous ambulatory peritoneal dialysis may remove drugs from the body, necessitating dosage adjustment.

METHODS

Inappropriate dosing in patients with renal dysfunction can cause toxicity or ineffective therapy. Therefore, the normal dosage regimen of a drug may have to be adjusted in a patient with renal dysfunction. Dosage adjustment is based on the remaining kidney function, most often estimated on the basis of the patient's glomerular filtration rate (GFR) estimated by the Cockroft-Gault formula. Net renal excretion of drug is a combination of three processes: glomerular filtration, tubular secretion and tubular reabsorption. Therefore, dosage adjustment based on GFR may not always be appropriate and a re-evaluation of markers of renal function may be required.

DISCUSSION

According to EMEA and FDA guidelines, a pharmacokinetic study should be carried out during the development phase of a new drug that is likely to be used in patients with renal dysfunction and whose pharmacokinetics are likely to be significantly altered in these patients. This study should be carried out in carefully selected subjects with varying degrees of renal dysfunction. In addition to this two-stage pharmacokinetic approach, a population PK/PD study in patients participating in phase II/phase III clinical trials can also be used to assess the impact of renal dysfunction on the drug's pharmacokinetics and pharmacodynamics.

CONCLUSION

In conclusion, renal dysfunction affects more that just the renal handling of drugs and/or active drug metabolites. Even when the dosage adjustment recommended for patients with renal dysfunction are carefully followed, adverse drug reactions remain common.

Superimposed coagulopathic conditions in cirrhosis: infection and endogenous heparinoids, renal failure, and endothelial dysfunction

In this article, the authors discuss three pathophysiologic mechanisms that influence the coagulation system in patients who have liver disease. First, bacterial infections may play an important role in the cause of variceal bleeding in patients who have liver cirrhosis, affecting coagulation through multiple pathways. One of the pathways through which this occurs is dependent on endogenous heparinoids, on which the authors focus in this article. Secondly, the authors discuss renal failure, a condition that is frequently encountered in patients who have liver cirrhosis. Finally, they review dysfunction of the endothelial system. The role of markers of endothelial function in cirrhotic patients, such as von Willebrand factor and endothelin-1, is discussed.

Complications of arteriovenous hemodialysis access: recognition and management

English language citations reporting complications of arteriovenous access for hemodialysis are critically reviewed and discussed. Venous hypertension, arterial steal syndrome, and high-output cardiac failure occur as a result of hemodynamic alterations potentiated by access flow. Uremic and diabetic neuropathies are common but may obfuscate recognition of potentially correctable problems such as compression or ischemic neuropathy. Mechanical complications include pseudoaneurysm, which may develop from a puncture hematoma, degeneration of the wall, or infection. Dysfunctional hemostasis, hemorrhage, noninfectious fluid collections, and access-related infections are, in part, manifestations of the adverse effects of uremia on the function of circulating hematologic elements. Impaired erythropoiesis is successfully managed with hormonal stimulation; perhaps, similar therapies can be devised to reverse platelet and leukocyte dysfunction and reduce bleeding and infectious complications.

Heparin-dependent platelet factor 4 antibodies and the impact of renal function on clinical outcomes: a retrospective study in hospitalized patients

Patients who develop thrombocytopenia and heparin-dependent platelet factor 4 antibodies while on or shortly after receiving a heparin product are often considered for alternative anticoagulation to minimize the occurrence of life and limb-threatening events. We retrospectively reviewed the hospital records of 97 patients with heparin-dependent platelet factor 4 antibodies (at least 65 of whom were felt by the primary team to have HIT) to determine the influence of renal performance on alternative anticoagulant selection and associated clinical events. For GFR > 30, approximately 30% of patients who did not receive alternative anticoagulation had documentation of concern for HIT versus 60% of patients in the GFR < 30 group. We found that a smaller proportion of patients with severe renal insufficiency, GFRs < 30 ml/min/1.73 m(2) were treated with an alternative anticoagulant-this despite their high incidence of thromboembolic events and comparable rates of HIT. Overall, rates of hemorrhage did not differ between patients when compared to those without renal insufficiency. However, there was a higher percentage of hemorrhagic events for patients with GFR < 30 ml/min/1.73 m(2) on alternative anticoagulants. This study demonstrates that patient's with GFRs < 30 ml/min/1.73 m(2) need to be assessed for overall hemorrhagic risk at the time of starting an alternative anticoagulant and need to be monitored closely to avoid hemorrhagic events.

The efficacy and safety of short- and long-term dual antiplatelet therapy in patients with mild or moderate chronic kidney disease: results from the Clopidogrel for the Reduction of Events During Observation (CREDO) trial

BACKGROUND

Mild and moderate chronic kidney disease (CKD) is associated with decreased survival and increased adverse events after a percutaneous coronary intervention (PCI). Therapy with clopidogrel decreases adverse events in large patient populations. Therefore, we sought to determine the efficacy and safety of long-term clopidogrel therapy in patients with CKD.

METHODS

Two thousand two patients from the CREDO trial in whom an elective PCI of a single or multiple vessels was planned were analyzed. Patients were randomly assigned to a 300-mg loading dose of clopidogrel before PCI followed by clopidogrel 75 mg/d for a year versus a placebo loading dose at the time of the PCI procedure and clopidogrel 75 mg/d for 28 days and placebo for the remainder of a year. Patients were categorized by their estimated creatinine clearance (>90 [normal, n = 999], 60-89 [mild CKD, n = 672], <60 mL/min [moderate CKD, n = 331]).

RESULTS

Diminished renal function was associated with worse outcomes. Patients with normal renal function who received 1 year of clopidogrel had a marked reduction in death, myocardial infarction, or stroke compared with those who received placebo (10.4% vs 4.4%, P < .001), whereas patients with mild and moderate CKD did not have a significant difference in outcomes with clopidogrel therapy versus placebo (mild: 12.8% vs 10.3%, P = .30; moderate: 13.1% vs 17.8%, P = .24). Clopidogrel use was associated with an increased relative risk of major or minor bleeding, but this increased risk was not different based on renal function (relative risk 1.2, 1.3, 1.1).

CONCLUSIONS

Clopidogrel in mild or moderate CKD patients may not have the same beneficial effect as it does in patients with normal renal function, but was not associated with a greater relative risk of bleeding based on renal function. Further studies are needed to define the role of clopidogrel therapy in patients with CKD.

Risk management of renal biopsy: 1387 cases over 30 years in a single centre

BACKGROUND

Although renal biopsy is largely employed, even in old patients with systemic diseases, few clinical studies have addressed its risk management. We aimed to obtain a comprehensive assessment of safety/utility ratio of percutaneous renal biopsy.

PATIENTS AND METHODS

Retrospective review of all the 1387 patients who consecutively underwent renal biopsy in a single centre over three decades (1973-2002) was made, with calculation of complications, multivariate logistical analyses to evaluate risk factors of complications, and rate of alteration of clinical hypotheses by pathological diagnosis.

RESULTS

There were no deaths and five major complications, (0.36%). One nephrectomy (0.07%), two surgical revisions (0.1%) and two arterial-venous fistulae (0.1%). There were also 337 minor bleeding complications (24.2%) (16.4% gross haematuria and 7.8% clinically relevant haematomas needing at least prolonged bed rest). Multivariate analyses demonstrated that the risk for complications was significantly increased by systemic autoimmune diseases with odds ratio (OR) 2.06, 95% confidence interval (CI)=1.40-3.01, end-stage kidney/acute-tubular necrosis (OR 2.96, 95% CI=1.19-7.30), and prolonged bleeding time test (BTT) (OR 1.87, 95% CI=1.17-2.83). Among the 1288 cases in which a clinical hypothesis before renal biopsy was recorded, renal pathology changed previous diagnoses in 423/1,288 (32.8%) of cases.

CONCLUSIONS

Risk assessment demonstrates that renal biopsy is a useful procedure with a low incidence of serious complications. Platelet function is the only modifiable factor significantly related to bleeding complications, suggesting the need for a more standardized alternative to the BTT. Platelet function should be evaluated to select low-risk patients for renal biopsy as 'a day case procedure', in order to build adequate risk management strategies.

Decreased glomerular filtration rate is a risk factor for hemorrhagic but not for ischemic stroke: the Rotterdam Study

BACKGROUND AND PURPOSE

Persons with early stages of chronic kidney disease, defined by a decreased glomerular filtration rate (GFR), have an increased risk of cardiovascular disease. It is unclear whether decreased GFR is a risk factor for stroke. We assessed the association between GFR and stroke in a prospective population-based cohort study.

METHODS

The study was based on 4937 participants of the Rotterdam Study who at baseline (1990 to 1993) were aged 55 years or over, free from stroke, and had serum creatinine assessment. GFR was estimated with the Cockcroft-Gault equation. Follow-up for incident cerebrovascular disease was complete until January 1, 2005. Data were analyzed with Cox proportional hazards models with adjustment for relevant confounders and results were expressed as hazard ratios with 95% CIs.

RESULTS

During an average follow-up of 10.2 years, 586 strokes (338 ischemic, 44 hemorrhagic, and 204 unspecified strokes) occurred. We found no association between GFR and risk of overall stroke or risk of ischemic stroke. In contrast, with decreasing GFR, the risk of hemorrhagic stroke strongly increased; the age- and sex-adjusted hazard ratio for hemorrhagic stroke was 4.10 (95% CI, 1.25 to 13.42) for lowest versus highest quartile of GFR, and there was a clear and highly significant dose-effect relationship. Adjustment for other vascular risk factors only slightly attenuated this association.

CONCLUSIONS

Decreased GFR is a strong risk factor for hemorrhagic, but not ischemic stroke.

Use of newer anticoagulants in patients with chronic kidney disease

PURPOSE

The current indications, dosing, and practical considerations for use of newer anticoagulants in patients with various degrees of renal impairment who do not require dialysis are reviewed.

SUMMARY

Kidney function should generally be evaluated in all patients commencing anticoagulant therapy. As in the general population, hospitalized patients with impaired renal function most often have impairment that is mild to moderate in severity. Drug dosing in patients with chronic kidney disease may require that adjustment be made to the usual loading or maintenance dose of a drug. Newer anticoagulants with labeling approved by the Food and Drug Administration for venous thromboembolism (VTE) prophylaxis, treatment, or both include the low-molecular-weight heparins (LMWHs) and the factor Xa inhibitor fondaparinux. Some LMWHs are also indicated for the management of patients with acute coronary syndrome (ACS). All of the newer anticoagulants currently available for the management of VTE and ACS have approved labeling for use in patients with mild-to-moderate renal impairment. Currently available LMWHs, factor Xa inhibitors, and direct thrombin inhibitors (excluding argatroban) are eliminated primarily by the kidneys, so dosing in patients with severe renal impairment may require cautious dosage reduction or increased monitoring for bleeding and thromboembolic complications or both. Unfractionated heparin is the preferred anticoagulant for use in most of these patients.

CONCLUSION

Newer anticoagulants should be used with caution in patients with mild-to-moderate renal impairment. Unfractionated heparin remains the preferred anticoagulant in most patients with severe renal impairment even though its use is associated with increased bleeding in this population. Dosing of newer anticoagulants, except argatroban, requires cautious dosage reduction and increased monitoring for complications.

Review article: the prothrombin time test as a measure of bleeding risk and prognosis in liver disease

BACKGROUND

Prothrombin time (PT)-derived international normalized ratio (INR) is used to assess bleeding risk and prognosis in cirrhosis, and to guide management of associated coagulation disturbances. Recent studies cast doubt on the validity of the assumptions that form the basis for these applications.

AIMS

To review and critique the use of the PT-INR in cirrhosis.

METHODS

Search of the literature.

RESULTS

In cirrhosis, there is a decrease in both pro- and anti-coagulants. The PT-INR measures only the activity of procoagulants and fails to capture changes in anticoagulants. It is therefore not surprising that the PT does not predict the bleeding risk. The PT-INR provides a robust measure of liver function but recent data showed INR inter-laboratory variability in this setting. This is not surprising as the INR was validated to normalize results for patients on vitamin-K antagonists, not for cirrhosis. This limitation was not appreciated, but the INR is used to construct the model for end-stage liver disease score to prioritize patients for liver transplantation. Reports showed that model for end-stage liver disease is modified by the thromboplastin used for testing.

CONCLUSIONS

Alternate tests to predict bleeding risk should be developed. The potential for misuse of the PT-INR should drive the development of alternate algorithms for organ allocation.

Essentials of anticoagulation in hemodialysis

Numerous acquired hemostatic abnormalities have been identified in renal insufficiency. Hemodialysis procedures add to these disturbances as they repetitively imply turbulent blood flow, high shear stress, and contact of blood to artificial surfaces. This nonphysiological environment leads to activation of platelets, leukocytes, and the coagulation cascade, resulting in fouling of the membrane and ultimately in clotting of fibers and the whole hemodialyzer. Anticoagulation in hemodialysis is targeted to prevent this activation of coagulation during the procedure. Most agents inhibit the plasmatic coagulation cascade. Still commonly used is unfractionated heparin, followed by low-molecular-weight heparin preparations with distinct advantages. Immune-mediated heparin-induced thrombocytopenia constitutes a potentially life-threatening complication of heparin therapy requiring immediate switch to nonheparin alternative anticoagulants. Danaparoid, lepirudin, and argatroban are currently being used for alternative anticoagulation, all of which possess both advantages and limitations. In the past, empirical strategies reducing or avoiding heparin were applied for patients at bleeding risk, whereas nowadays regional citrate anticoagulation is increasingly used to prevent bleeding by allowing procedures without any systemic anticoagulation. Avoidance of clotting within the whole hemodialyzer circuit is not granted. Specific knowledge of the mechanisms of coagulation, the targets of the anticoagulants in use, and their respective characteristics constitutes the basis for individualized anticoagulation aimed at achieving full patency of the circuit throughout the procedure. Patency of the circuit is an important prerequisite for optimal hemodialysis quality.

Evidence-based treatment recommendations for uremic bleeding

Uremic bleeding syndrome is a recognized consequence of renal failure and can result in clinically significant sequelae. Although the pathophysiology of the condition has yet to be fully elucidated, it is believed to be multifactorial. This article is a review of both the normal hemostatic and homeostatic mechanisms that operate within the body to prevent unnecessary bleeding, as well as an in-depth discussion of the dysfunctional components that contribute to the complications associated with uremic bleeding syndrome. As a result of the multifactorial nature of this syndrome, prevention and treatment options can include one or a combination of the following: dialysis, erythropoietin, cryoprecipitate, desmopressin, and conjugated estrogens. Here, these treatment options are compared with regard to their mechanism of action, and onset and duration of efficacy. An extensive review of the clinical trials that have evaluated each treatment is also presented. Lastly, we have created an evidence-based treatment algorithm to help guide clinicians through most clinical scenarios, and answered common questions related to the management of uremic bleeding.

Coagulation disorders and hemostasis in liver disease: pathophysiology and critical assessment of current management

Normal coagulation has classically been conceptualized as a Y-shaped pathway, with distinct "intrinsic" and "extrinsic" components initiated by factor XII or factor VIIa/tissue factor, respectively, and converging in a "common" pathway at the level of the FXa/FVa (prothrombinase) complex. Until recently, the lack of an established alternative concept of hemostasis has meant that most physicians view the "cascade" as a model of physiology. This view has been reinforced by the fact that screening coagulation tests (APTT, prothrombin time--INR) are often used as though they are generally predictive of clinical bleeding. The shortcomings of this older model of normal coagulation are nowhere more apparent than in its clinical application to the complex coagulation disorders of acute and chronic liver disease. In this condition, the clotting cascade is heavily influenced by numerous currents and counter-currents resulting in a mixture of pro- and anticoagulant forces that are themselves further subject to change with altered physiological stress such as super-imposed infection or renal failure. This report represents a summary of a recent multidisciplinary symposium held in Charlottesville, VA. We present an overview of the coagulation system in liver disease with emphasis on the limitations of the current clinical paradigm and the need for a critical re-evaluation of the current tenets governing clinical practice. With the realization that there is often limited or conflicting data, we have attempted to represent diverse opinion and experience from the perspectives of both hepatology and hematology beginning with a brief update on the physiology of normal coagulation.

[Thrombocytopathy and blood complications in uremia]

Bleeding diathesis and thrombotic tendencies are characteristic findings in patients with end-stage renal disease. The pathogenesis of uremic bleeding tendency is related to multiple dysfunctions of the platelets. The platelet numbers may be reduced slightly, while platelet turnover is increased. The reduced adhesion of platelets to the vascular subendothelial wall is due to reduction of GPIb and altered conformational changes of GPIIb/IIIa receptors. Alterations of platelet adhesion and aggregation are caused by uremic toxins, increased platelet production of NO, PGI(2), calcium and cAMP as well as renal anemia. Correction of uremic bleeding is caused by treatment of renal anemia with recombinant human erythropoietin or darbepoetin alpha, adequate dialysis, desmopressin, cryoprecipitate, tranexamic acid, or conjugated estrogens. Thrombotic complications in uremia are caused by increased platelet aggregation and hypercoagulability. Erythrocyte-platelet-aggregates, leukocyte-platelet-aggregates and platelet microparticles are found in higher percentage in uremic patients as compared to healthy individuals. The increased expression of platelet phosphatidylserine initiates phagocytosis and coagulation. Therapy with antiplatelet drugs does not reduce vascular access thrombosis but increases bleeding complications in endstage renal disease patients. Heparin-induced thrombocytopenia (HIT type II) may develop in 0-12 % of hemodialysis patients. HIT antibody positive uremic patients mostly develop only mild thrombocytopenia and only very few thrombotic complications. Substitution of heparin by hirudin, danaparoid or regional citrate anticoagulation should be decided based on each single case.

The effect of uremia on platelet contractile force, clot elastic modulus and bleeding time in hemodialysis patients

INTRODUCTION

Uremic bleeding frequently occurs in dialysis patients. Although its mechanism is not well characterized, acquired platelet dysfunction has been implicated in its pathogenesis. Skin bleeding time has been used to characterize platelet dysfunction in this population. However, the bleeding time is prone to error. The goal of this study was to compare the bleeding time to the novel platelet function parameters platelet contractile force and clot elastic modulus as well as platelet aggregation studies in controls and patients receiving maintenance hemodialysis.

MATERIALS AND METHODS

Forty-five subjects completed this study (25 controls, 20 dialysis). All subjects had the Ivy skin bleeding time procedure performed, as well as the collection of whole blood samples for the determination of platelet contractile force, clot elastic modulus, % von Willebrand Factor antigen, and platelet aggregation studies. Pearson's correlation determined the relationships between skin bleeding time and platelet function and clot structure parameters and markers of renal dysfunction.

RESULTS

Bleeding time was significantly prolonged in the dialysis group relative to controls. The platelet function parameters were not significantly different between groups. There was a significant relationship between bleeding time and creatinine concentration, however, no relationship existed between bleeding time and platelet function parameters.

CONCLUSIONS

Skin bleeding time poorly correlates with measurements of platelet function. There were no significant differences noted in platelet function between the groups despite the prolongations in bleeding time in the dialysis group. These data may suggest that the bleeding time reflects perturbations in platelet adhesion or secretion, and not aggregation. Further study is needed to characterize platelet function in dialysis patients.

Propyl gallate-induced platelet aggregation in patients with end-stage renal disease: The influence of the haemodialysis procedure

BACKGROUND

Platelet dysfunction is a well-established disturbance in haemodialysis (HD) patients. Propyl gallate is a synthetic platelet activator with the property to stimulate platelet aggregation. The aim of the present study was to evaluate the influence of a single haemodialysis session on propyl gallate-induced platelet aggregation.

METHODS

Thirty-nine HD patients were enrolled in the study and 20 healthy volunteers were studied as controls. Cellulose diacetate (CD) dialysers were used in 20 patients and polysulphone dialysers in 19. HD was performed via an A-V fistula in 27 patients and via an i.v. catheter in 12. Erythropoietin was administered in 37 patients (epoietin-alpha in 24 and darbepoietin in 13). Thirty-four were receiving the low-molecular-weight heparin tinzaparin. Propyl gallate slide aggregometry was used for evaluating platelet aggregation.

RESULTS

In HD patients, platelet aggregation was impaired before as well as after the HD session. No effect of the HD procedure, type of vascular access, adequacy of HD or type of erythropoietin on the propyl gallate-induced platelet aggregation was detected. Platelet aggregation was higher when CD dialyser was used. A negative correlation between the time needed for platelet aggregation to occur and tinzaparin dose was found.

CONCLUSION

Propyl gallate-induced platelet aggregation in HD patients is impaired. Platelet aggregation was higher in patients dialysed with CD membrane than in those dialysed with polysulphone membrane. The higher the dose of tinzaparin, the higher the platelet aggregation. The clinical significance of the above results needs further evaluation.

ACTIVATION OF l-ARGININE TRANSPORT IN UNDIALYSED CHRONIC RENAL FAILURE AND CONTINUOUS AMBULATORY PERITONEAL DIALYSIS PATIENTS

1. Treatment with haemodialysis and continuous ambulatory peritoneal dialysis (CAPD) presents different pathophysiological profiles and it has been suggested that clinical outcome in chronic renal failure may depend on the mode of dialysis. The transport of L-arginine, a precursor of nitric oxide, into blood cells is increased in uraemic patients on haemodialysis. The present study was designed to investigate L-arginine transport into red blood cells (RBC) in uraemic patients not yet on dialysis and on CAPD therapy. 2. Eleven uraemic patients not yet on dialysis and 17 on CAPD were included in the study. L-Arginine transport into RBC and plasma and RBC amino acid profiles were analysed in these sets of patients. 3. L-Arginine transport via system y(+), but not y(+)L, into RBC, was significantly increased in undialysed uraemic patients (459 +/- 40 micromol/L per cell per h) and CAPD patients (539 +/- 61 micromol/L per cell per h) compared with controls (251 +/- 39 micromol/L per cell per h). High-pressure liquid chromatography measurements demonstrated low levels of plasma L-arginine in uraemic patients both on CAPD (54 +/- 3 micromol/L) and not yet on dialysis (80 +/- 6 micromol/L) compared with control subjects (146 +/- 14 micromol/L). 4. Our findings provide the first evidence that uraemic patients not yet on dialysis and on CAPD present with an activation of L-arginine transport via system y(+) into RBC associated with reduced plasma levels of L-arginine.

Nitric oxide in chronic renal failure

Endothelium-derived nitric oxide (NO) is critically involved in the regulation of a wide variety of vascular functions. It had been hypothesized that a deficiency of vascular NO might be involved in the accelerated atherosclerosis and dramatic cardiovascular mortality observed in patients with chronic renal failure. At present it is difficult to measure authentic NO in vivo. An alternative is to study NO by its effect on vascular tone by using the forearm blood flow technique. In this way, studies demonstrated an unimpaired availability of NO under baseline conditions but a profound reduction of agonist-induced endothelium-dependent vasodilatation in uremic patients. Further investigation showed that the latter phenomenon is mainly attributable to a reduced availability of vascular NO upon agonist stimulation, while the NO-independent mechanism(s) appear(s) to be intact in this setting. Explanations for this finding include an uncoupling of NO synthase induced by cofactor deficiency, and/or a reduced NO availability caused by high levels of oxidative stress. Recent data suggest only a minor role for cytochrome-P450 2C9-dependent pathways in this context. Future studies have to show which mechanisms are most relevant, and whether they are sensitive to therapeutic intervention.

Uremic bleeding: pathophysiology and clinical risk factors

Renal insufficiency appears clinically to be associated with a bleeding tendency. This has been documented in clinical settings including as a complication of medical interventions such as surgery and also in spontaneous bleeding events at gastrointestinal and intracranial sites. The pathophysiology that underlies this tendency appears to involve platelet dysfunction and an imbalance of mediators of normal endothelial function. It is also may be complicated by the co-morbidities in this population, such as vascular disease, hypertension and anemia, and the medical interventions required to treat such co-morbidities. This article reviews the evidence, the pathophysiology and the risk factors for increased bleeding in patients with chronic renal insufficiency.

Life-Threatening Hemorrhage After Dalteparin Therapy in a Patient with Impaired Renal Function

Dalteparin and other low-molecular-weight heparins are frequently used for the treatment of deep vein thrombosis and for other indications. Unlike unfractionated heparin (UFH), dalteparin is mainly cleared through the kidney; therefore, it can accumulate in patients with impaired renal function, increasing the risk of hemorrhage. An 84-year-old woman with chronic renal failure was hospitalized because of stenosis of a femorofibular bypass in her right leg. Peripheral transluminal angioplasty was performed successfully. Later the same day, Doppler sonography revealed deep vein thrombosis of the left lower leg. Treatment with dalteparin was started. The patient was discharged home 3 days later, with dalteparin to be continued at home. One day later, the patient was rehospitalized because of a pronounced hematoma on her flank. Her hemoglobin level had dropped to 5.5 g/dl. Treatment with dalteparin was stopped, and protamine 2500 U and two transfusions of packed red blood cells were administered. Treatment with UFH and oral anticoagulants were started because of a persistent risk for venous thrombosis. Thereafter, the patient's hemoglobin level remained stable, and no further bleeding episodes occurred. As long as systematic studies of the efficacy and safety of dalteparin in patients with severe renal impairment are lacking, dalteparin should be avoided or used only with close monitoring of antifactor Xa activity in these patients. As an alternative, UFH can be used because monitoring of UFH is well established and easier than it is with dalteparin. Renal impairment does not notably influence the short elimination half-life of UFH, which unlike that of dalteparin or other low-molecular-weight heparins allows for rapid dosage adjustments to prevent hemorrhage.

Plasma levels of plasminogen activator inhibitor type 1, factor VIII, prothrombin activation fragment 1+2, anticardiolipin, and antiprothrombin antibodies are risk factors for thrombosis in hemodialysis patients

Patients with end-stage renal disease are prone to hemorrhagic complications and simultaneously are at risk for a variety of thrombotic complications such as thrombosis of dialysis blood access, the subclavian vein, coronary arteries, cerebral vessel, and retinal veins, as well as priapism. The study was devised for the following purposes: (1) to identify the markers of thrombophilia in hemodialyzed patients, (2) to establish a role for antiphospholipid antibodies in thrombosis of the vascular access, (3) to characterize phospholipid antibodies in hemodialysis patients, and (4) to study the effects of dialysis on coagulation cascade. A group of 20 hemodialysis patients with no thrombotic complications (NTC) and 20 hemodialysis patients with thrombotic complications (TC) were studied along with 400 volunteer blood donors. Patients with systemic lupus erythematosus and those with nephrotic syndrome were excluded. All patients underwent a screening prothrombin time, activated partial thromboplastin time, fibrinogen (Fg), coagulation factors of the intrinsic and extrinsic pathways, antithrombin III (AT-III), protein C (PC), protein S (PS), resistance to activated protein C, prothrombin activation fragment 1+2 (F1+2), plasminogen, tissue type plasminogen activator (t-PA), plasminogen tissue activator inhibitor type-1 (PAI-1), anticardiolipin antibodies type M and G (ACA-IgM and ACA-IgG), lupus anticoagulant antibodies, and antiprothrombin antibodies type M and G (aPT-IgM and aPT-IgG). The study showed that PAI-1, F 1+2, factor VIII, ACA-IgM, and aPT-IgM levels were increased significantly over controls both in TC and NTC, however, they could distinguish patients with thrombotic complications from those without, being increased maximally in the former group. The novelty of the study is represented by the significant aPT increase that was observed in non-systemic lupus erythematosus hemodialysis patients, and particularly in those with thrombotic events. In addition, there was a reduction of factor XII during the treatment. It is possible to assume in the TC group and, to a lesser extent, also in the NTC group that endothelial cells liberate PAI-1 in the vascular lumen, which causes hypofibrinolysis. In addition, an excess of factor VIII is activated by endothelial dysfunction with subsequent activation of the coagulation cascade as shown by increased F1+2 and fibrinogen. ACA-IgM, in turn, is capable of interfering with the system of protein C, a potent anticoagulant factor that inactivates cofactors Va and VIIIa. They also induce the expression of procoagulant factors on the surface of the endothelial cells. In conclusion, the hypercoagulable state caused by alterations of coagulation and fibrinolytic factors is a cause of vascular access dysfunction and thrombosis of other vessels.

Case Report. Chronic subdural haematoma and autosomal polycystic kidney disease: Report of two new cases

Chronic subdural haematoma (SDH) was recently described in some patients who were suffering from autosomic dominant polycystic kidney disease (ADPKD). It results in various neurological symptoms mimicking those related to intracranial aneurysms, which are relatively frequent in such patients. The authors report two cases of chronic SDH observed in two patients known to have advanced renal failure attributed to ADPKD. Medical imaging failed to reveal features of associated intracranial abnormalities such as aneurysms or arachnoid cysts. Surgical drainage resulted in a good recovery without relapse during a long period of follow up that exceeded 10 years in the first case.

Mortality rates and hemorrhagic complications in asian-pacific islanders during treatment of acute myocardial infarction

The management of acute myocardial infarction balances the benefits of antiplatelet and anticoagulant therapies against the risk for hemorrhage. The investigators report that Asian-Pacific islanders and patients with renal insufficiency have an increased rate of bleeding complications with hospitalized for acute myocardial infarction.

Utility of in vitro closure time test for evaluating platelet-related primary hemostasis in dialysis patients

BACKGROUND

The platelet aggregation and skin bleeding time (SBT) tests currently used for assessment of hemostasis impairment in dialysis patients have important disadvantages. The authors explored the utility of a novel in vitro closure time test (PFA-100, platelet function analyzer) in which the process of platelet adhesion and aggregation after vascular injury is simulated in vitro in dialysis patients.

METHODS

Thirty-four long-term dialysis patients were included in the study with 30 healthy volunteers as the control group. In vitro closure time was compared with results from the platelet aggregation and SBT tests.

RESULTS

In vitro closure time identified more patients and fewer controls with hemostasis impairment. In the patient group, 60%, 40%, and 20%, and in the control group, 0%, 10% and 3% of persons were found to have hemostasis impairment as determined by in vitro closure time, platelet aggregation, and SBT, respectively. In addition, values for patients and controls were significantly different for in vitro closure time (P < 0.05) but not for platelet aggregation or SBT. Thus, closure time appears to be more sensitive and specific than the other 2 tests. No correlation was found between the 3 tests, either in patients or in controls. However, a high correlation (r = 0.73; P < 0.0001) was found between the 2 types of in vitro closure time test (collagen/epinephrine [CEPI] and collagen/adenosine diphosphate [CADP]) in patients and controls.

CONCLUSION

These results indicate that in vitro closure time can be a useful test for detecting platelet-related primary hemostasis defects in dialysis patients.

Treating coagulopathy in trauma patients

Coagulopathy in patients with severe trauma is related to platelet and coagulation factor loss, consumption, and dysfunction. It is exacerbated by dilution, acidosis, and hypothermia. Hemorrhage control, warming, and appropriate blood product support are lifesaving. Further improvements in hemorrhage control will save additional lives and resources.

Physiologic inhibitors of coagulation in patients on chronic hemodialysis

Patients on hemodialysis are at increased risk for bleeding and thromboses. The intriguing balance between these risks is more complex than once thought, as endogenous clotting factors and their regulators come into contact with bioincompatible dialyzer membranes, in the setting of an extracorporeal circuit of blood flow, in the face of the uremic state. In this review, we summarize the current data on the interaction between the physiologic inhibitors of coagulation and hemodialysis. Data sources and study selection were obtained from research and review articles related to the endogenous anticoagulation pathway published in English on MEDLINE from 1972 to 2002. While protein C activity and protein S antigen concentrations are increased, there is no change in antithrombin III levels during hemodialysis in relation to predialysis levels. Plasma protein Z, which has only recently been studied in uremic subjects, is increased as well. In addition, hemodialysis leads to elevated tissue factor plasminogen inhibitor, thrombomodulin, tissue plasminogen activator, and plasminogen activator inhibitor-1 activities. The potential functional significance of these observations is discussed. Finally, as erythropoietin is commonly prescribed to uremic patients and is recognized to be prothrombotic, an appraisal of its interaction with the naturally occurring anticoagulants is presented. It is apparent that we are only beginning to realize the complexity of the interplay between this myriad of serum factors and hemodialysis. Further research is needed to shed light on this underexplored area of hemodialysis.

Thrombosis in end-stage renal disease

Although renal failure has classically been associated with a bleeding tendency, thrombotic events are common among patients with end-stage renal disease (ESRD). A variety of thrombosis-favoring hematologic alterations have been demonstrated in these patients. In addition, "nontraditional" risk factors for thrombosis, such as hyperhomocysteinemia, endothelial dysfunction, inflammation, and malnutrition, are present in a significant proportion of chronic dialysis patients. Hemodialysis (HD) vascular access thrombosis, ischemic heart disease, and renal allograft thrombosis are well-recognized complications in these patients. Deep venous thrombosis and pulmonary embolism are viewed as rare in chronic dialysis patients, but recent studies suggest that this perception should be reconsidered. Several ESRD treatment factors such as recombinant erythropoietin (EPO) administration, dialyzer bioincompatibility, and calcineurin inhibitor administration may have prothrombotic effects. In this article we review the pathogenesis and clinical manifestations of thrombosis in ESRD and evaluate the evidence that chronic renal failure or its management predisposes to thrombotic events.

Protective role of nitric oxide in mice with Shiga toxin-induced hemolytic uremic syndrome

BACKGROUND

Nitric oxide (NO) is an endogenous vasodilator and platelet inhibitor. An enhanced NO production has been detected in patients with hemolytic uremic syndrome (HUS), although its implication in HUS pathogenesis has not been clarified.

METHODS

A mouse model of Shiga toxin 2 (Stx2)-induced HUS was used to study the role of NO in the development of the disease. Modulation of l-arginine-NO pathway was achieved by oral administration of NO synthase (NOS) substrate or inhibitors, and renal damage, mortality and platelet activity were evaluated. The involvement of platelets was studied by means of a specific anti-platelet antibody.

RESULTS

Inhibition of NO generation by the NOS inhibitor L-NAME enhanced Stx2-mediated renal damage and lethality; this effect was prevented by the addition of l-arginine. The worsening effect of L-NAME involved enhanced Stx2-mediated platelet activation, and it was completely prevented by platelet depletion.

CONCLUSIONS

NO exerts a protective role in the early pathogenesis of HUS, and its inhibition potentiates renal damage and mortality through a mechanism involving enhanced platelet activation.