Effects of desmopressin on platelet membrane glycoproteins and platelet aggregation in volunteers on clopidogrel

PURPOSE

The use of clopidogrel is standard in interventional cardiology. Haemorrhage occurs in some patients, which implies a need for a non-transfusional therapy. Desmopressin showed its efficacy as an antidote of acetylsalicylic acid. In this trial the effects of desmopressin on platelet glycoproteins and the platelet's ability to aggregate under the influence of clopidogrel are studied.

METHODS

The trial was conducted as an open, prospective, single-centre, randomised pilot study with n=17 healthy volunteers in a parallel-group design. 1 h after an oral loading dose of 375 mg clopidogrel the effects of a single-dose of 300 mug of Octostim nasal spray (n=9) on platelet aggregation, activity of platelets on the density of membrane-bound receptors are measured.

RESULTS

Ristocetin cofactor and platelet reactivity rose significantly after the administration of Octostim nasal spray with 31.9% and 5.3%, respectively (p=0.0329; p=0.0414). The ADP-induced platelet aggregation increased after the administration of Octostim nasal spray by approximately 20% (p=0.0564). The fraction of CD62- and CD63-positive platelets did not change after clopidogrel nor after desmopressin (p=0.4203; p=0.6774). The density of GPIIb/IIIa receptors per platelet did not change after desmopressin (p=0.9652). The density of GPIb/IX receptors per platelet rose after desmopressin without reaching the level of significance (p=0.0802). In the desmopressin group alone the receptor density rose by 5.5% (p=0.0783).

CONCLUSION

The administration of desmopressin improved the primary haemostasis when given in addition to a clopidogrel therapy. Patients undergoing a heart catheter procedure with clopidogrel might benefit from the use of desmopressin when having a bleeding episode.

The impact of a medium molecular weight, low molar substitution hydroxyethyl starch dissolved in a physiologically balanced electrolyte solution on blood coagulation and platelet function in vitro

BACKGROUND AND OBJECTIVES

Hydroxyethyl starches (HES) may have the potential to impact negatively on haemostasis. Recent findings suggest that side-effects on haemostasis stem not only from the physicochemical differences between HES, but also from the composition of the solvent. We compared the effects of a newly developed medium molecular weight (MW) and low molar substitution (MS) HES dissolved in a physiologically balanced electrolyte solution (MW 130, MS 0.42; B-HES) with a commercially available non-balanced HES (MW 130, MS 0.4; NB-HES), and with Ringer's lactate (RL) solution in vitro.

MATERIALS AND METHODS

Activated partial thromboplastin time (APTT), factor VIII clotting activity (F VIII:C) and von Willebrand factor (vWF) activity were investigated in 48 healthy individuals. Platelet function as measured by turbidimetric platelet aggregometry and whole blood impedance aggregometry induced by adenosine diphosphate (ADP), collagen and thrombin receptor activating peptide (TRAP), and by ADP and TRAP-induced expression of activated platelet fibrinogen receptor glycoprotein (GP) IIb/IIIa was determined in 24 participants. Haemodilution (25% and 50%, v/v for blood coagulation analyses and 20% and 40%, v/v for platelet function studies) was performed using the two HES preparations and RL.

RESULTS

APTT was significantly longer and F VIII and vWF significantly lower at 25% and 50% dilutions with NB-HES compared to B-HES and RL. At 20% and 40% dilutions, ADP and TRAP-induced expression of activated platelet surface GP IIb/IIIa was significantly increased by B-HES compared to NB-HES and RL. Percentages of platelet GP IIb/IIIa expression were also significantly greater in samples diluted with B-HES than in undiluted blood. Neither the diluent (B-HES, NB-HES and RL) nor the degree of dilution (undiluted, 20% and 40% dilution) had any significant influence on ADP, collagen or TRAP-induced turbidimetric platelet aggregation or impedance platelet aggregation.

CONCLUSIONS

In contrast to a non-balanced 130 kDa, MS 0.4 HES (NB-HES), a 130 kDa, MS 0.42 HES preparation dissolved in a physiologically balanced electrolyte solution (B-HES) does not affect APTT, F VIII:C and vWF in vitro. Both types of HES do not affect platelet aggregation induced by ADP, collagen or TRAP. B-HES but not NB-HES increases the expression of activated platelet GP IIb/IIIa induced by ADP or TRAP.

Preservation of in vitro function of platelets stored in the presence of a synthetic dual inhibitor of factor Xa and thrombin

BACKGROUND

The use of citrate anticoagulant limits the clinical significance of platelet function tests. Thrombin inhibitors cannot prevent thrombin-induced platelet activation completely. We examined the influence of benzylsulfonyl-d-Arg-Pro-4-amidinobenzylamide (BAPA), a dual inhibitor of Factor Xa (FXa) and thrombin, on platelet responsiveness to agonists when measured between 2 and 24 h after venipuncture.

METHODS

Blood samples from 36 individuals were anticoagulated with citrate and BAPA, respectively. Turbidimetric platelet aggregometry (TPA) and impedance platelet aggregometry (IPA), a whole blood platelet counting assay for measuring platelet aggregation (PCA), and Platelet Function Anlayzer-100 (PFA-100 closure times (CTs) were determined after whole blood storage between 2 and 24 h after venipuncture. Native whole blood was studied over 48 h to determine the inhibition of thrombin generation by BAPA, hirudin and melagatran.

RESULTS

BAPA inhibited thrombin generation completely for 48 h, while hirudin and melagatran did not. The use of citrate resulted in significantly reduced TPA induced by arachidonic acid (AA) or adenosine 5'-diphosphate (ADP), and significantly reduced IPA regardless of agonist when measured 10 and 24 h after blood collection. PCA ratios in citrated blood also dropped significantly 10 and 24 h after venipuncture. The length of storage of BAPA-anticoagulated blood samples over 24 h had no significant influence on any platelet response. The reproducibility of platelet function assay results obtained from BAPA-anticoagulated samples was significantly better than corresponding data from citrated blood.

CONCLUSION

TPA, IPA, PCA or PFA-100 CTs remain stable for 24 h when whole blood is anticoagulated with a dual inhibitor of FXa and thrombin. This would greatly simplify the shipment of samples for platelet function testing.

Haemocompatibility of polymer-coated stainless steel stents as compared to uncoated stents

Acute and subacute stent thrombosis still represent an unsolved problem in connection with endovascular stents. For this reason coatings are tested now with the intention to reduce thrombogenicity of stainless steel surfaces. This comparative study examined whether a polymeric stent coating affected the haemocompatibility of a stainless steel stent. For compatibility testing, coated and non-coated stents were implanted in a low-grade thrombogenic closed-loop system perfused with platelet rich plasma at shear rates far below the threshold value at which shear-rate-induced activation of thrombocytes occurs. After 21 circulations of the filling volume (exposure time: 6.2 min), the number of single circulating platelets in the perfusion system with uncoated stainless steel stents decreased almost twice as much as was the case with polymer-coated stents. This is thought to indicate that more thrombocytes had adhered to the uncoated stainless steel stent, or that the thrombocytes were clustered in circulating aggregates. Parallel to the platelet aggregation/adherence, a release reaction took place, as was evident from the TAT complexes indicating the generation of thrombin. In the case of the implantation of uncoated stainless steel stents, both the number of activated circulating thrombocytes and the level of platelet reactivity (number of thrombocytes circulating in the plasma as aggregates) were notably higher than in the system with polymer-coated stents. At the same time it should be noted that the activation or aggregation is almost wholly attributable to the exogenic surface of the implanted stent, since activation due to the tube system or to shear rate can be excluded (as shown by measurements of the system without a stent). In addition to activation of the thrombocytes, a notable increase in the number of receptors per platelet (significant only in the system with the uncoated stent) took place. This supports both the adherence of the thrombocytes and their readiness to aggregate, since more receptors (docking places for ligands) are available. The better haemocompatibility of the polymer-coated stents, as verified in the laboratory, was also evident under microscopic examination of the explanted stents following the perfusion tests.

Influence of the direct NO-donor SIN-1 on the interaction between platelets and stainless steel stents under dynamic conditions

It was investigated whether the NO-donor SIN-1, the active metabolite of molsidomine, influenced the activation of platelets, the formation of circulating platelet aggregates, the spontaneous aggregation of platelets and the activation of the clotting system triggered by a body foreign surface in an in vitro closed-loop perfusion model. With human platelet-rich plasma at micromolar concentrations SIN-1 exerted pronounced effects on the interaction between platelets and an exogenous surface. In the absence of SIN-1, the number of circulating single platelets decreased significantly, which could be due either to the formation of circulating platelet aggregates or to the adhesion of platelets to the stent. Both these processes were blocked by the addition of SIN-1. Moreover, the platelets exhibited hyperaggregability in the absence of SIN-1 whereas the NO-donor was able to completely inhibit spontaneous platelet aggregation. Similar results were obtained in flow cytometry experiments. Without SIN-1, high platelet surface densities of both the GPIb/IX and GPIIb/IIIa receptors were observed. In addition, the density of the fibrinogen receptor increased significantly with the number of perfusion cycles. SIN-1 was able to suppress the augmented GPIIb/IIIa receptor expression significantly. Molsidomine seemed to have the potential to reduce the incidence of thrombotic processes triggered by the exogenous surface of the stent.

[Haemostatic disorders in ENT patients. Part 2: Pathophysiology, diagnostics, clinical feature and therapy]

In the first part of the medical education article on haemostatic disorders in ENT patients the basic physiology of haemostasis and main diagnostic tools were presented and discussed. The second part presents disorders of the coagulation system,thrombocyte function and blood vessels with special emphasis on clinical practice in ENT surgery. In this context, haemophilia A and B, von Willebrand disease and different forms of thrombocytopenia are of main clinical importance. Some underlying diseases such as malignomas, renal and hepatic insufficiency in combination with drug therapy (e.g.anticoagulants and thrombocyte function inhibitors) play an important role in clinical practice as well. Sepsis and haemorrhage may lead to disseminated intravascular coagulation (DIC). Beside a systematic review, important haemostatic disorders are illustrated with case reports.

[Perioperative therapy of von Willebrand disease. Demonstration of pathophysiology, clinical problems and therapy options using two case reports]

Von Willebrand disease (vWD) is the most widespread inherited bleeding disorder caused by quantitative or qualitative abnormalities of von Willebrand factor (vWF), an adhesive glycoprotein found in blood plasma and platelets and participating in primary and secondary/endothelium haemostasis as well. Although bleeding symptoms are often mild or moderate, patients with vWD represent a very heterogenous group with different phenotypes and a wide variability of the clinical pattern. In accordance with different defects of vWF, vWD is classified into various types and subtypes. This is illustrated by two case reports of patients with different types of vWD. Two main therapeutic options are available for the prevention and treatment of bleeding: desmopressin (DDAVP) and replacement therapy with plasma concentrates containing both factor VIII and vWF. DDAVP is the treatment of choice for most patients with type 1, representing about 80% of all patients with vWD. In patients with most types of type 2 and in all patients of type 3, DDAVP alone is ineffective or even contraindicated, and it is usually necessary to switch to plasma concentrates. Although treatment of vWD seems to be relatively simple in most cases, the exact diagnosis and phenotype characterization requires specialized or expert laboratory facilities. Furthermore, no reliable screening method for the diagnosis of vWD exists. Acquired vWD has similar clinical features and laboratory findings to the congenital forms and is mostly associated with lymphoproliferative or autoimmune disorders or neoplasia.

Evaluation of the haemocompatibility of titanium based biomaterials

The increased use of metallic biomaterials in contact with blood e.g. for the application as coronary stents leads to the development of new biomaterials. The main requirements for stents are high flexibility, high cold deformability and sufficient mechanical strength (static and dynamic), which can be obtained by strain hardening, radio-opacity and haemocompatibility. In order to investigate the properties of the metallic biomaterials in contact with blood, a comparison of the haemocompatibility of newly developed materials with established materials has been performed. To evaluate haemocompatibility without the influence of the geometry of the material, spherical powders produced by rotating electrode process (REP) were used in a dynamic test system with full human blood under two different stress conditions. The high shear stress simulates the arterial and the low shear stress simulates the venous situation. The use of a dimensionless score point (SP) system where the parameters of the haemocompatibility are determined with and without a material exposition allows an objective comparison of the materials used.

The polysaccharide fucoidan inhibits microvascular thrombus formation independently from P- and L-selectin function in vivo

BACKGROUND

Adhesion molecules of the selectin family (mainly P- and L-selectin) have been suggested to mediate interactions between platelets, leukocytes and endothelial cells in thrombus formation. The polysaccharide fucoidan has anticoagulative properties, but is also able to bind and block the function of the selectins. Here, we investigated in vivo (i) if fucoidan can prevent microvascular thrombus formation, and (ii) whether this is potentially mediated by the inhibition of P-and/or L-selectin.

MATERIALS AND METHODS

For this purpose, we used intravital microscopy in the mouse cremaster microcirculation in which thrombosis was induced photochemically by light exposure to individual arterioles and venules after intravenous (i.v.) injection of FITC-dextran.

RESULTS

We found that intravenous administration of fucoidan significantly prolonged the time required for complete occlusion in arterioles and venules by almost seven- and nine-fold, respectively. In contrast, treatment with monoclonal antibodies against P- and L-selectin had no effect on the development of microvascular thrombosis. Fucoidan and also the anti-P-selectin antibody completely inhibited baseline venular leukocyte rolling in the cremaster muscle, indicating that these treatment regimes abolished P-selectin function. Importantly, fucoidan and the anti-P-selectin antibody had no effect on systemic platelet and leukocyte counts. On the other hand, we found that fucoidan treatment significantly altered coagulation parameters, including prothrombin time (Quick percentage), activated partial thromboplastin time (APTT) and thrombin clotting time (TCT), which may explain the potent in vivo anticoagulative effect of fucoidan observed here.

CONCLUSIONS

Taken together, our novel findings suggest that fucoidan effectively prevents microvascular thrombus formation induced by endothelial damage in arterioles and venules in vivo. This protective effect of fucoidan is not attributable to inhibition of P- and L-selectin function but may instead be related to the anticoagulative capacity of fucoidan.

Coexisting Anti-I/i Plus Anti Pr Cold Agglutinins in Individual Sera

Background: Sera with high-titer cold agglutinins (CAs) of unclear or even of apparently definite specificity may contain mixtures of CAs with different specificities. The combination of anti-I plus anti-Sia-b1 CAs in sera of patients with Mycoplasma pneumoniae infections is well documented. No systematic studies on CA mixtures in sera of patients with other diagnoses are available. Material and Methods: Sera of 322 patients with high-titer CAs were exhaustively absorbed with sialidase-treated red blood cells (RBCs). By absorption, CAs against the sialidase-resistant I/i antigens are removed. If CAs reacting with untreated RBCs are left after absorption, they are directed against the sialidase- and protease-sensitive Pr(1,2,3) antigens or against the sialidase-labile but protease-resistant antigens of the Sia-I/b/Ib complex. If CA mixtures were found, specificities and isotypes of the CAs obtained by cold adsorption and warm elution were determined. Results: Three patients had mixtures of anti-i plus anti-Pr CAs, 2 patients had mixtures of anti-I plus anti-Pr CAs. Conclusion: The occurrence of CAs directed against biochemically different antigens in individual sera proves two autoimmune processes against the same cells (erythrocytes) in the same patient. One explanation for this constellation would be a postinfection cold agglutination in a patient with chronic CA disease. Copyright 2000 S. Karger GmbH, Freiburg

[The effect of aprotinin and tranexamic acid on fibrinolysis and thrombin generation during cardiopulmonary bypass]

OBJECTIVE

Antifibrinolytic drug therapy has proved to be effective in reducing blood loss associated with cardiac surgery and cardiopulmonary bypass (CPB). Concerns remain regarding the risk of enhancing thrombosis. In the present study we investigated the effect of aprotinin (AP) and tranexamic acid (TA) on fibrinolysis and thrombin generation during CPB.

METHODS

60 patients undergoing coronary artery bypass graft surgery were randomised in 3 groups. They received either aprotinin ("high-dose-scheme"), tranexamic acid (2 g/h) or no antifibrinolytic therapy (control group). Collection of blood was performed at 7 pre-, intra- and postoperatively predetermined intervals. Fibrinolytic activity was determined by measuring concentrations of D-dimer, thrombin generation by the measurement of thrombin-antithrombin III complex (TAT).

RESULTS

There was no significant increase of D-dimers in the AP or TA group. D-dimer concentration in the control group increased significantly after starting CPB. Comparing with the control group, thrombin generation in the AP group was significant less, while TA group produced significantly higher values.

CONCLUSION

After the administration of AP for cardiac surgery we observed reductions in both intraoperative fibrinolysis and thrombin generation. In case of TA suppression of fibrinolytic activity in the absence of concomitant reduction in thrombin generation occurred. These results suggest that TA could potentiate a hypercoagulable state with the risk of thrombosis in the perioperative setting.

[Heparin-induced thrombocytopenia (HIT). Importance for anesthesia and intensive care]

For many decades, heparins have been used successfully for prophylaxis and treatment of thromboembolic complications world-wide. Although heparin-induced thrombocytopenia (HIT Type II) is a well-known adverse effect of heparin therapy, thromboembolic complications during heparin therapy are rarely diagnosed exactly to be related to HIT. At present an immunologic etiology of HIT by generation of multimodal immune complexes against a neo antigen of heparin and platelet factor 4 is equivocally accepted. The incidence of HIT seems to be related to the type of heparin (unfractioned/low molecular weight) or other underlying risks such as peripheral occlusive vessel disease. Mortality and complications resulting from HIT is reported to be about 20-30% each. For diagnosis of HIT Type II, clinical observation and simultaneous laboratory testing are essential. Discontinuation of heparin is a simple and essential manoeuvre, and anticoagulation has to be continued by alternative drugs. The heparinoid danaparoid-sodium and the thrombin inhibitor recombinant hirudin have been used successfully world-wide for treatment in many patients with HIT Type II including cardiopulmonary bypass surgery or renal replacement procedures. Furthermore, other therapeutical alternatives (e.g. immunoglobulins, prostaglandines) exist. Randomised controlled studies have to evaluate which drug has to be preferred in the future including risk/benefit ratio. The need of supplementary surgical procedures (e.g. embolectomy) depends on the individual clinical status. The patients have to be informed in detail about their underlying disease and further deleterious consequences of re-exposition with heparin. HIT should be recorded in an emergency certificate and the national Committee on Drugs should be informed about this severe side effect of heparin therapy.

Diagnostic value of procalcitonin: the influence of cardiopulmonary bypass, aprotinin, SIRS, and sepsis

BACKGROUND

The reasons for a systemic inflammatory response syndrome (SIRS) following ECC are not yet fully understood. Procalcitonin (PCT) blood levels may distinguish between bacterial infections and a non-bacterial systemic inflammation. We investigated the influence of ECC, ECC modified by application of aprotinin, systemic inflammation, and bacterial infection on the PCT values.

METHODS

20 CABG patients were randomized and divided in two groups. Group A served as the control group, while group B perioperatively received a high dose of aprotinin. Blood samples for measurement of PCT were taken 6 times perioperatively. Furthermore, blood samples were taken from 20 preoperatively comparable patients who suffered from bacterial infection (n = 10) (group C) or a SIRS (n = 10) (group D) after ECC; in these groups PCT was determined daily after the onset of inflammation.

RESULTS

There was no significant elevation of PCT in group A or B at any time. In sepsis patients a significant elevation of PCT was seen, with the peak level of 18.6+/-6.3 ng/ml on the second day after diagnosis; the PCT level of SIRS patients remained constantly low (<0.9 ng/ml).

CONCLUSIONS

In this study it was demonstrated that ECC and the use of aprotinin did not have any influence on the secretion of PCT. A systemic bacterial infection caused a significant increase of PCT, whereas PCT values remained normal in case of a SIRS. So it seems to be possible to distinguish between a primary SIRS and a bacterial sepsis by means of PCT.

[A delayed hemolytic transfusion reaction due to irregular antibodies with an anti-Kidd(a) specificity]

HISTORY AND CLINICAL FINDINGS

A 56-year-old woman was admitted for replacement of a previously implanted right hip prosthesis which had become loose (no infection). She limped painfully on a shortened leg whose mobility was markedly impaired. At the site of the previous operation the pelvis was lower by about 2 cm; the scar looked well healed.

INVESTIGATIONS

Routine laboratory tests were normal except for moderately raised erythrocyte sedimentation rate (18/ 27 mm). There was complete loosening of the prosthesis on X-ray.

TREATMENT AND COURSE

Intraoperative bleeding from a branch of the inferior gluteal artery required blood transfusion and further erythrocyte infusions became necessary. Jaundice developed on the 4th postoperative day and 7 days later the direct Coombs test was positive with demonstrable agglutination. Free irregular erythrocytic anti-Kidd(a) (anti-jk[a]) antibodies were found in the serum. To counteract the delayed haemolytic transfusion reaction, exclusively jk(a)-negative erythrocytes were infused. The jaundice gradually disappeared and the bilirubin values became normal.

CONCLUSION

Jaundice and signs of haemolysis after erythrocyte transfusion may be due to delayed transfusion reaction and should be investigated with the direct Coombs test.

[Hemocompatibility of various synthetic granulates]

The adherence of platelets to different polymer granulates was examined in a perfusion chamber filled with platelet-rich plasma. The surface area of each of the granulates was of a standardised size. The results were compared with those found for a non-thrombogenic and a highly thrombogenic foreign-body surface. The three polymers examined-Cryolite, Styrolux and Zylar-must be considered non-thrombogenic. Platelet adherence to these substances is significantly less (3%) than that to a highly thrombogenic surface such as glass (95%). The three materials did not differ in terms of platelet adherence, and would appear to be suitable potential materials for use in cell separators.

Haemostatical and rheological aspects of dysfibrinogenemia

Congenital dysfibrinogenemia is based on different alterations in the structure of the fibrinogen molecule leading to a variety of disturbances in the clotting process. Clinical manifestations of the disorder are showing a wide range from asymptomatic states to mild bleeding diathesis as well as thrombotic complications. In this study two of the 14 patients with dysfibrinogenemia showed a history of mild bleeding while the others showed no clinical symptoms. As fibrinogen is also an important factor of the blood fluidity not only haemostatic but also rheological parameters were measured. Included in the study were 14 patients with ascertained dysfibrinogenemia in comparison to 11 non-affected relatives and a control group of 297 apparently healthy subjects. Plasma viscosity (p < 0.0001) and erythrocyte aggregation index (p < 0.00001) were significantly higher in the patients than in their healthy relatives and the control group. A pathologically increased erythrocyte aggregation was found in 10 of the 14 patients but only in 1 of the 10 relatives. The dysfunction of the fibrinogen molecule thus influences the aggregation process of the red blood cells to a greater extent than normal fibrinogen. Moreover, there seems to be a stronger influence of the dysfunctional fibrinogen molecule on the aggregation process than on plasma viscosity. To date the question if the enhanced erythrocyte aggregation in dysfibrinogenemic patients may be of any diagnostic interest and if there are significant differences between patients with bleeding diathesis and thrombophilia cannot be answered and remains to be cleared in further investigations.

Thrombolytische Therapie mit Urokinase bei hämolytisch-urämischem Syndrom

Vier Kleinkinder im Alter zwischen 1 7 Monaten und 3½ Jahren wurden unmittel-bar nach Sicherung der Diagnose eines post-gastroenteritischen hämolytischurämischen Syndromes fibrinolytisch mit niedrig dosierter Urokinase (Dauerinfusion von 1000 E/kg/h) und antikoagulatorisch mit Heparin (15-25 E/kg/h) be-handelt. Bei Kreatininwerten von 3,0 bis 5,9 mg/dl und Harnstoffkonzentrationen von 179 bis 269 mg/dl war in allen 4 Fällen noch eine Restdiurese vorhanden, die unter kontinuierlicher Furosemid-Infusion in Verbindung mit der Lysetherapie innerhalb weniger Stunden in eine Polyurie überging. Die Dauer der Lysetherapie betrug im Mittel 88 Stunden (64-108 h). Die Parameter der Hämolyse und der Nierenfunktion konnten in allen Fällen ohne Dialyseverfahren und Plasmapheresen normalisiert werden. In zwei Fällen entwickelte sich bei normaler Nierenfunktion ein behandlungsbedürftiger Hypertonus.

[Hypercoagulation caused by heparin-associated type II thrombocytopenia]

The immunological type of heparin-associated thrombocytopenia (HAT II) is a severe complication of heparin treatment and is associated with arterial and venous thrombosis. Only patients with absolute thrombocytopenia have prompted suspicion of HAT in clinical practice. We report on a 44-year-old male who developed thromboembolic episodes after coronary angiography such as reinfarction and thrombotic episodes of A. brachialis. Fibrinolytic therapy combined with i.v. unfractionated heparin treatment was the therapy of choice and was followed by severe further thromboembolic adverse effects. Besides an impaired fibrinolytic response and elevated antiphospholipid antibodies, we diagnosed HAT type II in HIPA and ELISA (Stago. Boehringer-Mannheim). This special patient had platelet counts within a normal range, when developing the thromboembolic episodes. It appears that the normal platelet count during the thromboembolic episodes reflect a relative thrombocytopenia. From a clinical point of view we recommend the use of a lab panel to exclude HAT type II in patients with thromboembolic episodes under therapy with fractionated or unfractionated heparin. Platelet counts within a normal range are not absolute exclusion criterion for HAT II.

Influence of low molecular weight hydroxyethyl starch (HES 40/0.5-0.55) on hemostasis and hemorheology

Hydroxyethyl starch (HES) with a high or medium molecular weight (MW) and a high degree of substitution is difficult to degrade and leads to an accumulation of large molecules. These molecules have a negative effect on hemostasiological parameters. In 10 patients with cerebrovascular diseases, a hemodilution therapy was carried out with low MW HES for 10 days. Due to the low MW of the HES used (56-61 kD), the rheological parameters erythrocyte aggregation and plasma viscosity were significantly lowered (p < 0.01). No coagulation parameters studied were affected beyond the dilution effect, which was measured using the decline in hematocrit. Low MW starch is a volume substitute that is well-suited for repeated infusion or hemodilution therapy, particularly for patients with increased hemorrhagic diathesis, because it does not affect hemostasis. The disadvantage of a relatively short volume effect can be compensated through a continuous infusion of a larger volume.

HES 200/0.5 is not HES 200/0.5. Influence of the C2/C6 hydroxyethylation ratio of hydroxyethyl starch (HES) on hemorheology, coagulation and elimination kinetics

The plasma clearance of hydroxyethyl starch (HES) depends on the initial molecular weight and the degree of substitution. So far, little attention has been paid to the clinical relevance of the C2/C6 substitution ratio of hydroxyethyl starch. 10 patients with cerebrovascular circulatory disturbance received hemodilution therapy for 10 days, consisting of 10% HES 200/0.5 (mean molecular weight 200 kD, degree of substitution 0.5) with a C2/C6 ratio of 13.4. A second group of 10 patients received a starch solution with identical initial molecular weight and degree of substitution but with a C2/C6 ratio of 5.7. After the administration of a single dose, no significant differences between the two groups were observed. After repeated administration, significant differences could be detected in hemorheology, coagulation and elimination (p < 0.01). The larger C2/C6 ratio led to a higher intravascular mean molecular weight (95 vs. 84 kD), which in turn led to a higher increase in serum concentration during the therapy (14.7 vs. 8.6 mg/ml). Hematocrit was lowered more (-30.5 vs. -23.5%) and plasma viscosity was increased more. There was also a more pronounced increase in partial thromboplastin time (+30% vs. +13%) and a factor of 2 larger decrease of factor VIII/von Willebrand factor-complex (p < 0.01), which exceeded the dilution effect. The higher C2/C6 ratio of HES 200/0.5/13.4 slows down enzymatic degradation. After repeated administration of this starch, large molecules accumulate which are inefficiently degraded. The same effect has been observed after therapy with highly-substituted HES. This accumulation of large molecules leads to a beneficial longer lasting volume effect. The disadvantages include an increase in plasma viscosity and coagulation disturbances, which cannot be explained with the respective dilution effect alone. For these reasons, the C2/C6 ratio is of clinical relevance and should be included in the product labeling in the future.

Effects of high-dose aprotinin on renal function in aortocoronary bypass grafting

BACKGROUND

To reduce blood consumption in cardiac surgery, aprotinin has been widely used for years. Because aprotinin is metabolized in the kidney, damage of the renal system has been discussed.

METHODS

To study these possibly unfavorable effects of aprotinin, a prospective, randomized, placebo-controlled study of 20 patients undergoing aortocoronary bypass operations was performed. A placebo group P was compared with group A, in which patients received high-dose aprotinin according to the "Hammersmith" regimen. Renal function was assessed for 5 postoperative days using sodium dodecyl sulfate gel electrophoresis and quantitative protein analysis of the urine.

RESULTS

During and after the operation, temporary renal dysfunction was found in all patients, with a substantial increase of all investigated indices. The alpha 1-microglobulin level in the urine was significantly increased in the aprotinin group for 5 days in comparison with the placebo group, with a maximum on the third postoperative day (64.8 +/- 13.7 versus 21.0 +/- 6.5 mg/L; p < 0.05). Similarly, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the bands of proteins filtrated in the renal tubular system were almost tripled in the aprotinin group 5 days postoperatively (5.0 +/- 0.8 versus 2.1 +/- 0.2; p < 0.05). Although urine production was significantly increased in group A (4789 +/- 580 versus 3653 +/- 492 mL/24 h postoperatively; p < 0.05), no relevant changes in serum or urine creatinine levels could be observed in either group.

CONCLUSIONS

Patients undergoing aortocoronary bypass operations demonstrate a temporary renal dysfunction. Aprotinin impairs renal function in addition by overloading the tubular reabsorption mechanisms. Patients with normal renal function preoperatively--as were included in this study--are able to compensate for both the perioperative renal dysfunction caused by the extracorporeal circulation and the additional tubular damage due to aprotinin.

Possible clinical effects of the interaction of hemodialysis membranes with adhesion proteins

In this study data obtained in an in vitro hemodialysis model are related to various parameters measured in patients' plasma during hemodialysis in a clinical crossover study. In vitro, blood from healthy volunteers was dialyzed under standardized conditions using the capillaries Fresenius MTS C (Cuprophane) and Hospal AN 69 (Polyacrylonitrile). Following dialysis, surface bound proteins were eluted with saline, 1 M Tris and 2% SDS, and analyzed by immunoblotting. Depending on the capillary, different protein patterns could be identified in the eluates. Intact forms of adhesion proteins were predominantly (fibrinogen) or exclusively (vitronectin) found in PA eluates. In contrast, low molecular weight products of fibrinogen as well as high molecular weight components containing antithrombin III (AT III) were present in CP eluates. Their presence may reflect fibrinolytic and procoagulatory activity during dialysis with CP capillaries. A microscopic investigation of CP membranes demonstrated fibrin lined platelet conglomerates. In the plasmas of patients dialyzed with CP capillaries high D-Dimer concentrations were found. We also noticed that during dialysis with PA membranes less heparin was consumed than during dialysis with CP membranes. Our study showed a good correlation of the observations in the vitro system and the measurements in patient samples.

Heparin-associated thrombocytopenia (HAT)--still a diagnostic and therapeutical problem in clinical practice

Type II of heparin-associated thrombocytopenia (HAT) is well known, but the cardinal symptom, thrombocytopenia, is rarely adequately considered. Serious and potential lethal complications such as pulmonary embolism, cerebral stroke, or limb gangrene are often falsely regarded as insufficient anticoagulation. Guided diagnosis and therapy are of vital importance for the patient's outcome. Based on the experience of patients with HAT Type II treated in the intensive care unit, a diagnostic and therapeutic approach to the cardinal symptom thrombocytopenia is presented. A recently developed heparin-induced platelet activation assay (HIPAA) seems to be a highly sensitive laboratory test. The first therapeutic principle in case of presumed and diagnosed HAT is the cessation of unfractioned or low-molecular-weight heparins. ORG 10172 (Orgaran), a low-sulfated heparinoid with a low cross-reactivity (10%) to heparins, can be regarded as the most effective anticoagulant in patients with HAT Type II.

Celite and kaolin produce differing activated clotting times during cardiopulmonary bypass under aprotinin therapy

Since the introduction of the proteinase inhibitor aprotinin in cardiac surgery, a strong increase of the activated clotting time (ACT) during the extracorporeal circulation phase (ECC) was reported in many clinical studies, but with a lack of correlation between ACT and heparin concentration. In searching for a cause of this inconsistency we investigated different surface activators of the ACT in a clinical study. During ECC ACT was measured in parallel, using a Hemochron device and corresponding tubes (nominally 12 mg celite activator) for celite ACT, and a HemoTec device with corresponding double tubes (nominally 0.1 ml kaolin activator) for kaolin ACT. Under the conditions of ECC, the kaolin ACT values (482 +/- 145 sec) were significantly lower than the celite ACT values (985 +/- 267 sec). These results were confirmed in ex-vivo experiments using an activated partial thromboplastin time (aPTT) model. With heparin alone, aPTT activated with celite and kaolin were similar. Including aprotinin in this model, the celite aPTT showed no correlation to the heparin concentration, whereas the kaolin aPTT remained well correlated to the heparin concentration and similar to the values without aprotinin. With aprotinin alone there were no changes of the aPTT times, whereas the celite ACT times were without any correlation. Our results indicate that using kaolin instead of celite the ACT measurements under aprotinin therapy stay in the same ranges as without application of aprotinin: aprotinin has no detectable influence on kaolin-activated ACT. In our opinion, kaolin should be used as the surface activator for ACT measurements under the conditions of ECC, heparinization, and aprotinin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of factor XIII activity by a new photometric assay in plasma and platelets of healthy blood donors

Crosslinking of fibrin monomers by activated factor XIII (F XIIIa) is a final event in blood coagulation. So the fibrin clot gains mechanical stability and resistance to plasmin degradation which is thought to be essential for normal blood clotting and wound healing (1-3). In addition, changes in plasma F XIII activity were found in several state of disease such as collagenoses, inflammatory bowel diseases, leukemias, subarachnoidal bleeding and delayed fracture healing (4-12). Because approximately 50% of the potential F XIII activity in plasma are present in platelets (1), the additional determination of F XIII activity in platelets is of clinical interest especially concerning platelet transfusions that may exert an additional benefit due to simultaneous substitution of platelet-bound F XIII. The latter differs from plasma F XIII as a dimer containing only a-chains (a2) compared to the plasmatic tetramer carrying additional b-chains (a2b2). We applied a recently described photometric assay suitable for the routine laboratory after adaption to an autoanalyser to determine F XIII activity in plasma and platelets of 64 healthy blood donors.

[Septic-toxic heart failure as a result of a heparin-induced thrombocytopenia with "white-clot-syndrome"]

A patient is presented who developed pulmonary artery embolism and thrombocytopenia with various arterial clots several days after an ankle joint osteosynthesis, which finally caused the amputation of the right arm. Unfractionated heparin was applied for the prevention of postoperative thrombosis. Obviously as a consequence of the liberation of toxic metabolites from the gangrenous lower arm, the patient developed septic shock which was exacerbated by a severe pneumonia caused by methicillin-resistant S. aureus bacteria (MRSA). Laboratory investigations showed an antibody (IgG) induced thrombopenia mediated by all low molecular weight and unfractionated heparins. By eliminating heparin and further treatment with a low molecular weight heparinoid (ORG 10,172), platelet count rose sufficiently and thrombotic process ceased completely. Septic shock was successfully treated by fluid replacement, antibiotics and inotropic substances.

[Indications for fresh frozen plasma: evaluation of virus inactivating preparations]

When no specific factor concentrate is available fresh-frozen plasma (FFP) is indicated in the treatment of clinically relevant hemorrhagic diathesis. These disorders include congenital factor V and XI deficiencies, multiple factor defects, as disseminated intravascular coagulation and severe liver disease, and patients receiving massive transfusions, when bleeding occurs and severe abnormalities on coagulation testing are evident. FFP is beneficial when used with plasma exchange in thrombotic thrombocytopenic purpura and related disorders. Various virucidal treatments including solvent-detergent (SD), photoactivated dyes (methylene blue) or pasteurization have been evolved to improve virus safety of human plasma. More extensive studies to demonstrate efficient virus inactivation in plasma have been performed with SD compared to other methods. On the other hand, the use of single-donor FFP in methylene blue treatment is possibly superior to pooled plasma which is processed according to the SD procedure. Pasteurization enables the inactivation not only of lipid-enveloped but also of non-lipid-enveloped viruses. Virucidal treatment of plasma may cause alterations in clotting factors, fibrinolysis and protease inhibitors; however, the currently achieved recovery of procoagulant activities is approximately comparable with that found in untreated FFP. The toxicity of virucidal additives is reported to be negligible since manufacturing includes a removal procedure (SD) or comparably low amounts (methylene blue) are used in inactivation treatment.

The role of protein C as an inhibitor of blood clotting during extracorporeal circulation

The plasma levels of protein C, AT III, the perioperative administration of fresh frozen plasma (FFP) and AT III concentrate were compared under the use of various drugs in a randomized, prospective double-blind study in 40 patients in whom an aortocoronary bypass operation was carried out. We formed four groups of ten patients: group A served as a control group, group B received a prostacyclin (PGI2) infusion of 10 or 20 ng/kg/min, group C high-dose aprotinin substitution, and group D was treated with a combination of prostacyclin and aprotinin. After an initial short-term rise in the inhibitors protein C and AT III, there was a fall in all groups in the further course of extracorporeal circulation. The initial preoperative values were reached again on the morning of the first postoperative day. This indicates a raised turnover and in association with this a raised rate of elimination of these factors caused by an increased thrombin activation during the extracorporeal circulation which cannot be prevented by the usual heparinization. Whereas prostacyclin had no effect on our results mediated by thrombocytic mechanisms, use of aprotinin led to a significant saving in the requirement for perioperative fresh frozen plasma and AT III substitution therapy. A clinical advantage of prostacyclin and aprotinin combination was not observed. In view of our results (individual analyses were mainly in the normal range), we consider that AT III and fresh frozen plasma should not be substituted routinely during or after extracorporeal circulation.

Clinical relevance of biological incompatibility and role of a central register

Different aspects relevant for the assessment and characterization of biomaterials are presented. Quite a number of basic concepts that play an important role when detecting unwanted adverse effects of drugs have to be taken into consideration when registering and evaluating unwanted effects of biomaterials. The institutionalization of the Central Bioregister at the University of Saarland is described. This Bioregister is a so-called "spontaneous" ad hoc recording system whose efficiency depends largely on the collaboration of physicians. Thus, the efficiency and rationality of the use of biomaterials can certainly be improved. The possibility of registering even rarely occurring unwanted effects as well as new indications will result in and allow a more general and/or a more specific therapy, depending on the biomaterial.

Contributions to biorheology during hemodialysis

Thrombogenicity is the property of a foreign surface to induce clotting processes or formation of aggregates after contact with blood. Beside the sort of anticoagulation patient's prethrombotic state, rheological factors as well as physicochemical properties of foreign membranes decisively influence thrombogenicity. We examined the influence of chronic renal failure and different hemodialyzers and blood transfusion therapy during hemodialysis on hemorheological parameters. Different membranes cannot be discriminated by the used hemorheological parameters. We clearly could demonstrate the close relationship between the hemofiltration rate and an increase of viscosity. Blood transfusion therapy or elevated hematocrit in combination with increased hemofiltration rate have influence on the flow behaviour of blood, especially in disturbed microcirculation.

Comparison of blood biocompatibility during haemodialysis with cuprophane and polyacrylonitrile membranes

Clotting within the dialyser is one of the most significant clinical parameters of biocompatibility. A study was designed to evaluate the biocompatibility of two different dialysis membranes (cuprophane and polyacrylonitrile) during therapy with conventional heparin. Transient leukopenia during cuprophane but not during polyacrylonitrile haemodialysis was observed, and elastase release using polyacryonitrile membranes was reduced (P less than 0.001). An elevation in F VIII:C activity during cuprophane haemodialysis has to be taken as an indication of endothelial disturbances. There was a significant (P less than 0.001) platelet activation (beta-thromboglobulin) and combined thrombin/plasmin generation using cuprophane membranes. This new synthetic polyacrylonitrile membrane inactivates the clotting in an extracorporeal system to a sufficient degree and allows a reduction in dosages of heparin. Platelet activation, platelet turnover, disturbances of endothelium, fibrinolysis activation, and granulocyte activation are reproducible parameters of a described interaction model. They also permit a comparison of different haemodialysis membranes.

[Ultrasound study of the newborn hip: results and consequences]

From October 1985 to September 1988 3000 neonatal hips were controlled clinically and by ultrasound. 3% of those needed an immediate treatment. In 45 of these 90 hips there were no directing clinical signs or suspicious hints in the family history or during the course of pregnancy. This means, that these inconspicuous cases would not have got their necessary therapy without the ultrasound-screening. Thus the results of this investigation supports the call for the general ultrasound-screening of the neonatal hip.

The development of a central register for side effects of biomaterials

Examination of the interaction between biomaterials and tissues from a clinical realistic as well as scientific viewpoint to complement the highly advanced experimental and biochemical basis research is an undertaking that has suffered a considerable amount of neglect in the past. Attempts to realize internationally a Central Registry for documenting clinically relevant side effects will be reported in detail. Implementation of the registry involves the review of present literature (prospective clinical studies, retrospective studies and case reports). An "incompatibility incident report/questionnaire" has been developed according to the guidelines of the "Report on Pharmacological Side Effects" of the Pharmaceutical Commission of the German Medical Association. The aims of registering and evaluating these reports will be demonstrated and discussed in detail.

Interleukin-2 determinations for monitoring the renal allograft

Our results show that worsening of renal function dependent on cyclosporin, or caused by acute renal insufficiency of postrenal origin, can be distinguished from viral infection and rejection reactions by the determination of interleukin-2 (IL-2) in plasma, which functions as an early indicator or follow-up parameter. A definite differentiation between steroid-sensitive rejection reactions and virus infection does not yet seem to be possible by interleukin-2 determination.