Plasma beta-thromboglobulin and platelet factor 4 in renal failure

A Clinical Study to Assess the Effect of Heparin in Dialyzer Rinsing Solutions

The solution usually recommended for rinsing the blood side, which is an indispensable step in preparing a dialyzer for hemodialysis (HD), contains saline and heparin. The heparin used for rinsing is said to reduce the thrombogenic properties of the dialysis membrane and, hence, also the need for systemic heparinization during the whole procedure. The aim of our study was to establish whether this postulate also applies to polysulphone steam-sterilized dialyzers. To do so, 16 patients on long-term dialysis were randomized into two groups of eight. One group was subsequently treated with polysulphone low-flux dialyzers (F6HPS), the other with polysulphone high-flux dialyzers (F60S). Both groups were examined, in a crossover manner during HD using a dialyzer previously rinsed with 1000 ml of saline plus 2,000 IU of heparin, and during HD using a dialyzer previously rinsed with 500 ml of saline without heparin. Except for the rinsing, HD conditions were completely identical. Blood obtained before HD, and at 15, 60 and 240 min of HD at the dialyzer inlet, was used to determine the activated partial thromboplastin time (to test heparinization control), the thrombin-antithrombin III complex (ELISA, to evaluate coagulation system activation), platelet factor 4 (ELISA, a substance with antiheparin activity), and platelet count. None of the above parameters showed, at any of the collecting intervals, a statistically significant difference between HD with and without heparin with a reduced volume of rinsing solution, or between HD using low- and high-flux dialyzers. It is concluded that heparin used to rinse polysulphone dialyzers before HD has no effect on blood coagulation or on the need for heparin during the procedure.

Some Hemostatic Changes During the Course of Hemodialysis in Patients with Erythropoietin Treatment

The recombinant human erythropoietin (rHuEPO), an effective agent in the treatment of renal anemia, can predispose chronic uremic patients to thrombotic events with regular hemodialysis (HD). It has been proposed that increased release of tissue plasminogen activator (t-PA) from endothelial cells, together with consumption of plasminogen activator inhibitor-1 (PAI- 1), is likely to be a leading cause of enhanced fibrinolytic activity (FA) during HD. In our study, rHuEPO-treated patients manifested PAI-1 Ag (antigen) plasma levels that were significantly augmented after HD, suggesting FA inhibition during the HD session. The elevated predialysis beta-thromboglobulin (BTG) and platelet factor-4 (PF-4) plasma levels were increased in rHuEPO-treated patients during HD; the platelet protein levels were simultaneously decreased in the control group. Both findings reflect decreased FA and greater activity of platelets in the course of HD with administration of rHuEPO and a possible correlation of these mechanisms with the questioned prothrombotic performance of rHuEPO. Key Words: Erythropoietin—Hentodiatysts—Fibrinotytic activity—Platelet proteins.

Anticoagulation intensity sufficient for haemodialysis does not prevent activation of coagulation and platelets

BACKGROUND

A single bolus of dalteparin at the start of haemodialysis (HD) may prevent clot formation, but subclinical activation of platelets and coagulation may still occur. Consequently, the relationship between clinical clotting events and activation markers of platelets and coagulation before and during HD is of interest.

METHODS

The effect of tapered doses of dalteparin during 84 HD sessions (4-4.5 h) was prospectively examined in 12 patients. Six of the patients were treated with warfarin. The initial dalteparin dose was reduced to 50% if no clotting was observed. Clinical clotting was evaluated by inspection of the air trap every hour and by inspection of the dialyser after each session. Anti-FXa activity was measured for assessment of dalteparin activity. Markers of activated plasma coagulation, (thrombin-antithrombin (TAT) and prothrombin fragment 1+2 (PF1+2)) and a marker of platelet activation (beta-thromboglobulin, beta-TG), were measured before the start of and after 3 and 4 h of dialysis. Ten pre-dialytic patients with chronic renal failure served as a control group. A total of 230 measurements of each parameter were performed.

RESULTS

An anti-FXa activity above 0.4 IU/ml at the end of HD inhibits overt clot formation for 4 h. This was obtained by an intravenous dalteparin dose of about 5000 IU. TAT and PF1+2 correlated to clinical clotting episodes (r=0.50 and 0.47, P<0.001). beta-TG was not significantly correlated to clinical clotting. All parameters increased during the sessions (TAT, PF1+2, beta-TG, P<0.001). When measurements during clinical clotting episodes were disregarded, all parameters were still markedly increased. Warfarin-treated patients had lower TAT and PF1+2. Dialysis patients had higher beta-TG values than pre-dialytic patients.

CONCLUSION

Despite clinically effective anticoagulation, obtained by dalteparin administration, platelets and coagulation are activated by HD, resulting in a potentially thrombophilic state. Warfarin treatment reduces clinical clot formation and subclinical activation of coagulation.

A study of platelet functions, some hemostatic and fibrinolytic parameters in relation to serotonin in hemodialyzed patients under erythropoietin therapy

Erythropoietin corrects anemia and improves hemostasis, but on the other hand bears a risk of thrombotic complications. Therefore in the present study an attempt has been made to evaluate bleeding time, platelet functions and some hemostatic and fibrinolytic parameters in relation to blood and platelet serotonin before and after 1, 2, 4, 8 and 12 weeks of treatment. 22 chronically hemodialyzed patients were administered with human recombinant erythropoietin (rHuEPO) in a dose of 2000 IU s.c. 3 times a week. Bleeding time was shortened significantly as early as after 1 week of the therapy, whereas hematocrit and hemoglobin increased after 2 weeks. These changes lasted throughout the study. Only a transient rise in platelet count, collagen-induced platelet aggregation, beta-thromboglobulin and VIII:C activity were observed during therapy relative to baseline values. ADP- and arachidonic acid-induced platelet aggregation seemed to be unaffected by rHuEPO treatment, whereas a gradual and progressive enhancement in platelet aggregation in response to ristocetin was found, starting from the 2nd week of the therapy. It lasted throughout the study and correlated inversely with the bleeding time and positively with a rise in both blood and platelet serotonin. rHuEPO did not alter plasminogen, fibrinogen, platelet factor 4, alpha 2 macroglobulin levels, protein C activity and euglobulin clot lysis time. A decline in protein C and S concentrations and antithrombin III activity observed during the therapy were counterbalanced by a fall in the activity of alpha 2 antiplasmin, C1 esterase inhibitor and plasminogen activator inhibitor. It is concluded that rHuEPO may improve platelet/vessel wall interactions possibly by means of serotonergic mechanisms. A lowered activity of inhibitors of fibrinolysis may be regarded as a protection against a general tendency to thrombosis during rHuEPO therapy.

Effect of a new anticoagulant (MD 805) on platelet activation in the hemodialysis circuit

MD 805 ((2R, 4R) 4-methyl-1-[N alpha-(3-methyl-1,2,3,4-tetra-hydro-8-quinoline-sulfonyl)L- arginyl]-2-piperidine carboxylic acid monohydrate), an anticoagulant, was used in patients with chronic renal failure undergoing maintenance hemodialysis, and the results were compared with those of heparin. MD 805 produced no significant increase in PF-4 which was observed on hemodialysis with heparin. Moreover, the arterio-venous difference in beta-TG during hemodialysis with MD 805 was significantly lower than that during hemodialysis with heparin. MD 805, even at the small amount of 15 mg/hr, exhibited a stable antithrombin effect without marked interindividual differences in coagulation time as monitored by aPTT. Consequently, it caused no increase in the proteins released as a result of platelet activation in the hemodialysis circuit. MD 805 thus proved very useful in maintenance anticoagulation therapy for patients on hemodialysis.

Platelets and antithrombin III in uraemia: the acute effect of haemodialysis

In 14 haemodialysis patients, platelet count, secondary platelet aggregation rate, immunological antithrombin III and antithrombin III activity were lower and plasma beta-thromboglobulin higher than in 14 age- and sex-matched controls. In contrast, primary platelet aggregation, the degree of secondary aggregation and circulating platelet aggregates did not differ. Haemodialysis was associated with signs of platelet damage reflected by increase in plasma beta-thromboglobulin, extraction of platelets in the dialyser and decline in platelet count. Platelets in the dialyser effluent line were less aggregable than platelets in arterial blood. Circulating platelet aggregates and immunological antithrombin III were unchanged during dialysis whereas antithrombin III activity showed a minor rise. In conclusion, uraemics show a decreased rate of secondary platelet aggregation, and haemodialysis confers further platelet injury due to blood/surface interactions during extracorporeal circulation. The defective platelet function and low antithrombin III activity may help to explain the paradoxical occurrence of both haemorrhagic and thrombotic complications in uraemia.

The significance of fibrinogen derivatives in plasma in human renal failure

The concentrations in plasma of fibrinogen derivatives fibrinopeptide A (FPA), beta 15-42 antigen and fragment E (FgE) antigen have been determined in patients with renal failure and compared to the concentrations of the platelet release products, beta-thromboglobulin (beta TG) and platelet factor 4 (PF4). In 'partial renal failure' (51Cr-EDTA clearance rate 4-60 ml/min) FPA, beta 15-42 antigen, FgE antigen and beta TG levels were significantly raised above a normal laboratory control group. These levels were further raised in a group of patients whose disease required regular maintenance haemodialysis (51Cr-EDTA clearance rate less than 4 ml/min). PF4 levels were not significantly raised in either group. A statistical analysis of all patient results revealed that FPA, beta 15-42 antigen and FgE antigen levels all correlated with beta TG levels but not with PF4 levels. It is known that beta TG is catabolized by the kidney but PF4 is not and that elevated beta TG levels in renal failure are caused by impaired elimination rather than increased production. These results suggest that the plasma levels of these three fibrinogen derivatives are elevated in renal disease at least in part by decreased elimination rather than by increased thrombin and plasmin activities alone.