[COVID-19-induced coagulopathy and thrombosis manifestations]. / COVID-19-induzierte Koagulopathien und thromboembolische Manifestationen.

CLINICAL ISSUE: Clinically, COVID-19 (coronavirus disease 2019) is increasingly seen as a systemic disease associated with multiorgan involvement through a hypercoagulatory condition in the sense of vasculopathy. STANDARD TREATMENT: Treatment with antiplatelet drugs or heparins appears to be indicated. The current evidence, at least for acetylsalicylic acid (ASA), is lacking. DIAGNOSTIC WORK-UP: Corresponding to the significant proportion of primarily microstructural vascular changes, the radiological diagnosis showed not only macrovascular pathologies, but also diffuse perfusion disorders. PERFORMANCE: Regional hypoperfusion in the lungs can be detected with and without pulmonary arterial embolism. Similar findings can be found in almost all organ systems. PRACTICAL RECOMMENDATIONS: A therapeutic intervention using low molecular weight heparins in hospitalized patients in situation-adapted dosage is indicated and is discussed in detail. In the detection of micro- and macrovascular thrombosis in the context of COVID-19, extended radiological diagnostics play a central role and are the basis of adapted therapy and secondary prevention.

[Prophylaxis of venous thromboembolic events in head and neck surgery]. / Die Prophylaxe venöser Thromboembolien bei Kopf­Hals­Operationen.

BACKGROUND: Application of perioperative thrombosis prophylaxis in head and neck surgery lacks consistent standards in Germany. Due to sparse data, the latest German S3 guideline concerning prophylaxis of thromboembolic events recommends a restrictive handling of anticoagulants in head and neck surgery, with few specific recommendations. OBJECTIVE: The aim of this paper is to provide concrete clinical recommendations based on a systematic literature review and the S3 guidelines. MATERIALS AND METHODS: A keyword-based literature search was performed and the German S3 guideline "Prophylaxis of Venous Thromboembolic Events" was used to state the current level of evidence and provide a clinical algorithm. RESULTS: Eight additional cohort studies dealing with the incidence of thromboembolic events in head and neck surgery were identified. There were no randomized controlled trials. In the proposed algorithm, a classification of dispositional (patient history) and expositional (operation time) risk into three groups enables preoperative risk evaluation indicating the individual demand for prophylaxis. In short operations without major tissue traumatization, routine drug-based thrombosis prophylaxis is not necessary, provided no third-grade risk factors (earlier thromboembolic event, coagulopathy, or malignant disease) are present. Low molecular weight heparins should be used as anticoagulants for drug-based prophylaxis. CONCLUSION: Prophylaxis of thromboembolic events in head and neck surgery is of high clinical relevance but there is currently limited evidence regarding its implementation. This paper is based on a systematic literature review and provides a clinical algorithm for head and neck surgeons.

[Pharmacology of the new oral anticoagulants]. / Pharmakologie der neuen oralen Antikoagulanzien.

New oral anticoagulants, such as dabigatran, rivaroxaban, apixaban, and edoxaban display pharmacologic and pharmacodynamic data similar to low molecular weight heparins. Peak levels are found 2-4 h after oral ingestion and elimination half-lives are in the range of 7-14 h. The drugs differ primarily concerning renal elimination. Dose adjustment is only performed in patients with impaired renal function, high risk of bleeding and patients with co-medications which influence the metabolism or anticoagulant effect of the drugs. Due to the short half-life, perioperative bridging is not necessary. Currently, no specific antidotes are available: however, assay systems are available for measuring the plasma concentration of dabigatran and rivaroxaban. In emergency cases a normal thrombin time excludes relevant levels of dabigatran, whereas a normal anti-factor Xa assay result excludes relevant levels of factor Xa inhibitors.The new anticoagulants are being used for prophylaxis of venous thrombosis in elective hip and knee surgery, as well as for treatment of venous thrombosis and for prevention of stroke and systemic embolism in patients with atrial fibrillation. Additional indications are to follow. Dabigatran is given at a dose of 110 mg initially 1-4 h after surgery followed by 220 mg once daily for prophylaxis of thrombosis and at doses of 110 mg or 150 mg twice daily for therapeutic anticoagulation. The prophylactic and therapeutic doses of rivaroxaban are 10 and 20 mg and, of apixaban 2.5 mg and 5 mg twice daily, respectively.

Hepatic uptake of a modified low molecular weight heparin in rats.

Fractionated and unfractionated heparins are widely used as antithrombotic agents. Because of their heterogeneous composition, it is difficult to study the pharmacokinetics of these drugs. We now report on a new method for labeling low molecular weight heparins with 131I by binding tyramine to the anhydromannose end of the molecules. We examined the pharmacokinetics of the compound by intravenous injection of 131I-tyramine-heparin into Wistar rats. About 18% of the activity was found in the liver, whereas 33% was detected in urine. Biological activity in terms of Factor Xa inhibition was measurable. Since evidence from cell culture experiments implies that reticuloendothelial cell system receptors might be involved in heparin metabolism, maleylated BSA, a substance known to block scavenger receptors, was injected before the radiolabeled heparin compound. The liver uptake was reduced from 17.4 to 4.8%. Injection of unfractionated heparin before tracer application caused a considerable increase in urine excretion of the tracer substance. To our knowledge, this is the first report that liver uptake of heparins is linked to scavenger receptor mediated mechanisms in vivo. This interaction of heparins with scavenger receptors might play an important role in the biology of the vessel wall.

Changes in fibrinogen and fibrin induced by a peptide analog of fibrinogen gamma365-380.

BACKGROUND: The effects of synthetic peptides with sequences derived from the gamma-chain of fibrinogen on the functional properties of fibrinogen and fibrin were investigated. METHODS: Methods included thrombelastography, clot turbidity measurement, clot elasticity measurement, platelet aggregation, and scanning transmission electron microscopy (STEM). RESULTS: Peptide gamma369-380 (NH(2)-WATWKTRWYSMK-COOH) showed the greatest impact on fibrin structure, compared with the 76 other overlapping dodecapeptides. Addition of this peptide, or peptide gamma365-380 (NH(2)-NGIIWATKTREWYSMK-COOH) to a mixture of fibrinogen and thrombin resulted a shorter clotting time, higher clot turbidity, lower clot elastic modulus, a higher degree of D-trimer and D-tetramer formation, and impaired plasmin proteolysis of the clot. In STEM, fibrin formed in the presence of peptide gamma369-380 consisted of a more extensive array of linear fibrils typically consisting of 20 or more molecules. Fibrils were better organized than those from non-peptide containing mixtures. CONCLUSIONS: Replacement of the tryptophan residue gamma376 massively reduced the effect of the peptide on fibrin structure. Binding of the peptide to fibrinogen induces conformational changes, which result in accelerated clotting and increased lateral association of fibrin protofibrils. The results imply a relevant functional role of sites interacting with peptide gamma369-380 region in the fibrinogen molecule.

[The TAFI system. The new role of fibrinolysis]. / Das TAFI-System. Die neue Rolle der Fibrinolyse.

The primary focus of the blood coagulation system is the prevention of blood loss. The system is regulated by various inhibitors, and by the fibrinolytic system, which removes the final product of the blood coagulation system, the fibrin clot. The fibrinolytic system is activated in the course of coagulation activation. The thrombin-activated fibrinolysis inhibitor (TAFI) is an important regulator of fibrinolysis. TAFI is activated by thrombin, and activation is enhanced in the presence of thrombomodulin. TAFIa, the product of TAFI activation, removes lysine residues from fibrin, which are essential for the binding of t-PA, plasminogen, and plasmin to fibrin. The fibrin loses its cofactor activity in t-PA-induced plasminogen activation, resulting in less plasmin, and the remaining plasmin finds less binding sites on fibrin, resulting in an increased resistance of the clot towards plasmin proteolysis. High concentrations of thrombin result in high TAFIa-activity and consequently in highly resistant fibrin clots. Patients with hyperprothrombinaemia consequently display elevated TAFIa-levels, which may contribute to the risk for thrombosis. Treatment with recombinant factor VIIa also leads to high concentrations of thrombin, resulting in fibrin clots with enhanced resistance towards fibrinolysis. At low thrombin concentration, as observed in patients with bleeding disorders or patients treated with anticoagulant drugs, less TAFIa is produced in the course of coagulation activation, and the clots are less resistant towards fibrinolysis. TAFIa-inhibitors are currently being developed for the treatment of throboembolic disorders or hypofibrinolytic DIC. Enhancement of TAFIa-activity may be helpful in patients with bleeding.

Point-of-care PT and aPTT in patients with suspected deficiencies of coagulation factors.

INTRODUCTION: There are several clinical settings and patient conditions especially in intensive care units, emergency departments, and operating theaters, where the coagulation status of a patient must be known immediately and point-of-care (POC) systems are beneficial due to low time to result. METHODS: This noninterventional, single-blinded, multicenter study with prospectively collected whole blood samples was performed to evaluate the diagnostic accuracy of the CoaguChek PT Test (POC PT) and CoaguChek aPTT Test (POC aPTT) compared to standard laboratory testing in patients with suspected deficiencies of coagulation factors. RESULTS: In total, 390 subjects were included. Both POC PT and POC aPTT showed concordance with the laboratory PT and aPTT. Lot-to-lot variation was below 2% both for POC PT and for POC aPTT. The mean relative difference of capillary blood compared to venous blood was 0.2 % with POC PT and 8.4% with POC aPTT. The coefficients of variation for repeatability of POC PT using whole blood were found to be between 2% and 3.6%. CONCLUSION: Our findings suggest reliable quantitative results with this POC system to support on-site decision-making for patients with suspected deficiencies of coagulation factors in acute and intensive care.

[Sepsis-associated coagulation disorders]. / Gerinnungsstörungen bei Sepsis.

Coagulation activation with intravascular fibrin formation is a general finding in patients with sepsis. Low coagulation factors may be caused by disseminated intravascular coagulation, as well as by loss of plasma and impaired hepatic synthesis in the course of sepsis. The leading clinical symptom in consumption coagulopathy is bleeding. Therefore, treatment mainly consists of substitution of coagulation factors and platelets. Meningococcal and pneumococcal, as well as some other infections may lead to sepsis-induced purpura fulminans, a condition associated with microvascular thrombosis, necrosis, and haemorrhage. A typical laboratory sign is a very low plasma protein C level. Treatment with protein C concentrate or recombinant activated protein C (Drotrecogin alfa, activated) has been shown to be beneficial in sepsis-induced purpura fulminans. Unfractionated heparin or low molecular weight heparin has been recommended for prophylaxis of venous thrombosis, but there are no clinical studies specifically on patients with sepsis. Antithrombin concentrate is used in patients with antithrombin deficiency treated with heparin for acute venous thrombosis or embolism, extracorporeal circulation procedures or other invasive procedures. There is no indication for general use of antithrombin concentrate in patients with sepsis even in patients with low plasma antithrombin levels. Drotrecogin alfa, activated, is used for treatment of patients with severe sepsis. Its use is not limited to patients with sepsis-induced disseminated intravascular coagulation, although these patients appear to benefit especially from this therapy.

Fibrinogen Mannheim II: a novel gamma307 His-->Tyr substitution in the gammaD domain causes hypofibrinogenemia.

BACKGROUND: In recent years it has become clear that the molecular investigation of hypofibrinogenemia provides unique insight into regions of the fibrinogen molecule that are important in molecular assembly, secretion and stability. OBJECTIVES: To investigate a case of hypofibrinogenemia at the molecular level. PATIENTS AND METHODS: The study was conducted on a 37-year-old woman from Mannheim, Germany, who had an antigenic plasma fibrinogen concentration of 0.86 g L(-1). Mutation screening was performed by DNA sequencing and the effect of the identified mutation was investigated at the protein level. RESULTS: Analysis of exon 8 of the fibrinogen gamma gene identified a heterozygous CAT-->TAT transition at codon 307. This novel His-->Tyr substitution was not detected when plasma fibrinogen was analyzed by electrospray ionization mass spectrometry. The mutation predicts a mass increase of 26 Da in the gamma chain, but purified gamma chains had a normal mass, indicating non-expression of the gamma(Tyr307) chain in plasma fibrinogen. CONCLUSIONS: This work reports a novel gamma307 His-->Tyr mutation (fibrinogen Mannheim II) that causes hypofibrinogenemia. Crystal structures show that His307 is located immediately adjacent to three residues that have been implicated in fibrin polymerization at the D:D interface. However, the histidine residue appears critical in maintaining structure of the fibrinogen gammaD domain, rather than in determining function.

The use of soluble fibrin in evaluating the acute and chronic hypercoagulable state.

Soluble fibrin detected in clinical plasma samples includes a variety of complexes consisting of fibrin monomer units, fibrinogen, and various proteolytic derivatives of fibrinogen and fibrin. The advantage of measuring soluble fibrin over fibrinopeptide A to detect thrombin action on fibrinogen is the considerably longer half-life of soluble fibrin in the circulation. Soluble fibrin can be detected by a variety of methods, including paracoagulation and precipitation assays, adsorption of fibrin monomer to insolubilized fibrinogen, functional assays based on the cofactor activity of some soluble fibrin compounds in t-PA-induced plasminogen activation, and by using fibrin-specific antibodies. Fibrin-specific antibodies may react with epitopes generated directly by fibrinopeptide A or B release or with epitopes generated by fibrin polymerization. Epitopes dependent on fibrinopeptide A release are often not accessible in native fibrin complexes and require the disaggregation of fibrin compounds to be reactive, whereas epitopes dependent on fibrinopeptide B release or fibrin polymerization are accessible to the monoclonal antibodies in nondenatured fibrin. Since soluble fibrin assays detect different structural or functional properties of soluble fibrin, no common calibrator for all soluble fibrin assays and, often, little correlation between different assay systems in clinical evaluations exist. Clinical applications of soluble fibrin assays include diagnosis and treatment monitoring of intravascular coagulation processes and prethrombotic states, monitoring anticoagulant treatment, and biocompatibility investigations. Some soluble fibrin assays have been demonstrated to be extremely sensitive indicators of acute fibrin formation. For the exclusion of venous thrombosis, D-dimer assays appear to be more sensitive than current soluble fibrin assays, since D-dimer assays detect freshly formed fibrin and proteolytic fragments of particulate clots. Further clinical studies are needed to establish the clinical utility of specific, soluble fibrin assays. The development of rapid, quantitative soluble fibrin assays for clinical routine use should be encouraged.

Predictive value of coagulation markers concerning clinical outcome 90 days after anterior myocardial infarction.

To study the predictive value of coagulation markers concerning clinical outcome, prothrombin fragment F1.2 (F1.2), fibrin monomer antigen (FM), D-Dimer (DD), and fibrinogen were measured in plasma samples drawn 2 and 7 days after acute myocardial infarction (AMI) in 314 consecutive patients randomized in a clinical trial of low molecular weight heparin (Dalteparin) (the FRAMI trial). Placebo-treated patients suffering death or new AMI within 90 days had significantly higher levels at day 2 of FM (Enzymun-Test FM), and DD (TINAquant D-dimer) (p = 0.001 and 0.02, respectively), but not F1.2 (Enzygnost F1.2 micro), relative to those without serious clinical events. At day 7 all three coagulation activation markers were significantly higher in patients with subsequent adverse clinical outcome. The Dalteparin group had significantly lower levels of these markers as compared to the placebo group. Left ventricular (LV) thrombus formation was not associated with changes in coagulation activation. However, patients with thrombus had significantly higher fibrinogen levels than those without thrombus (p = 0.004 day 2), independent of treatment group. Thus, markers of coagulation activation may be useful in stratification of patients when estimating risk for adverse clinical outcome after AMI. Furthermore, elevated fibrinogen levels are associated with increased risk of LV thrombus formation.

Fibrin detected in plasma of patients with disseminated intravascular coagulation by fibrin-specific antibodies consists primarily of high molecular weight factor XIIIa-crosslinked and plasmin-modified complexes partially containing fibrinopeptide A.

Pooled plasma from 40 patients with severe disseminated intravascular coagulation (DIC) secondary to septic conditions was subjected to gel permeation chromatography on Sephacryl S-500 HR after sample pretreatment with KSCN for dissociation of non-covalent fibrin complexes. Fibrin antigen in eluates was detected by an array of ELISA tests, using two monoclonal antibodies against fibrin degradation product D-dimer, a monoclonal antibody against an epitope generated by plasmin cleavage of the D-domain, and an antibody against the neo-N-terminus of the alpha-chain of fibrin exposed by cleavage of fibrinopeptide A. Tag antibodies were a polyclonal antibody against the fibrinogen/ fibrin D-domain, a POD-conjugated version of the monoclonal antibody against fibrin alpha-chain neo-N-terminus, and a polyclonal antibody against fibrinopeptide A. Most fibrin-related material present in the pooled DIC plasma was of higher molecular mass than fibrinogen. Fibrin polymers were reactive with antibodies against D-dimer, plasmin cleaved D-domain, and fibrin alpha-chain neo-N-terminus. Part of the polymers reacted with antibodies against fibrinopeptide A, indicating presence of fibrinogen or desA-fibrin monomer within the covalently linked complex. In conclusion, the primary analytes detected by monoclonal antibodies for D-dimer, plasmin-specific epitopes of fibrin degradation products, as well as sites exposed by fibrinopeptide cleavage in plasma from patients with disseminated intravascular coagulation are high molecular weight factor XIIIa-crosslinked fibrin complexes, containing plasmin-cleaved D-domains, intact fibrin monomer units, and fibrinogen or desA-fibrin monomer.

A 96-well microfiltration assay for measurement of total clottable fibrinogen.

In clinical routine use, fibrinogen is measured by clotting-time methods, or by clot turbidity in photometric prothrombin time determination. For calibration of these assays measurement of total thrombin-clottable protein has been recommended. We have now developed a microfiltration assay for total thrombin-clottable protein. Plasma samples were mixed with thrombin in a 96-well microfiltration device. After clot formation, the fluid was extracted by vacuum suction, and fibrin adherent to the filter membranes washed with buffer. Membrane segments with adherent fibrin were recovered from the 96-well manifold with a punch and transferred to tubes containing denaturing buffer solution. After dissolution of fibrin, protein concentration was determined by optical absorption at 280 nm. The microfiltration assay displayed a high correlation with the total clottable protein method (R = 0.95), and fibrinogen antigen (r = 0.96). Correlation with clotting time assays, and PT-derived fibrinogen in 150 clinical plasma samples was in the range of r = 0.84 to r = 0.97. Intraassay and day-to-day variability of the assay was comparable to the conventional total clottable fibrinogen assay. The novel microfiltration assay appears to be well suited for measurement of large series of samples for calibration, screening purposes, and clinical trials.

The Fibrin Assay Comparison Trial (FACT): evaluation of 23 quantitative D-dimer assays as basis for the development of D-dimer calibrators. FACT study group.

Although D-dimer has gained widespread clinical use as a parameter for detection of in vivo fibrin formation, the issue of standardization of D-dimer assays remains to be resolved. The FACT study was performed to generate basic data for development of calibrators and standard preparations. A set of 86 samples, including plasma samples from patients with DIC, DVT. and other clinical conditions, serial dilutions of pooled plasma samples, and plasma samples containing fibrinogen- and fibrin derivatives, were distributed to 12 manufacturers of D-dimer assays. D-dimer assays differ concerning specificity for crosslinked fibrin, and preference for either high molecular weight fibrin complexes, or low molecular weight fibrin degradation products. Terminal plasmin digests of fibrin clots for calibration produce aberrant results in some assays, especially those with preference for high molecular weight crosslinked fibrin derivatives. The best conformity is achieved by the use of pooled plasma samples from patients with high levels of D-dimer antigen in plasma. In vitro preparations containing a comparable composition of fibrin derivatives to clinical plasma samples may also serve as reference material.

The fibrin assay comparison trial (FACT): correlation of soluble fibrin assays with D-dimer.

Soluble fibrin (SF) is regarded as an indicator of acute fibrin formation and a precursor of fibrin thrombi. Using a set of clinical plasma samples, and fibrin derivatives, five assays for measurement of SF, including two chromogenic assays, two ELISA systems, and one latex-enhanced photometric immunoassay were compared. Correlation between SF assays was moderate (Spearman's rho values between 0.344 and 0.805). Re-calibration with serial dilutions of desAABB-fibrin monomer resulted in adjustment of the numerical scale of the assays without improving correlation. All SF assays reacted with purified crosslinked fibrin derivatives. Using clinical plasma samples, Spearman's rho of SF assays with D-dimer consensus values based upon results of 23 quantitative D-dimer assays were between 0.491 and 0.911. Although all SF assays react with desAABB-fibrin monomer complexes, SF assays are heterogeneous concerning reactivity with fibrin compounds observed in clinical plasma samples. The prospect of a common calibrator for SF assays therefore seems to be remote. Since SF assays react with crosslinked fibrin derivatives, it is not possible to clearly distinguish between acute fibrin formation, and fibrin dissolution on the basis of the results of current SF assays.

Protamine neutralization of the release of tissue factor pathway inhibitor activity by heparins.

The present study was designed to investigate the action of protamine on the release of tissue factor pathway inhibitor (TFPI) activity by unfractionated (UF) and low molecular weight (LMW) heparin in healthy individuals. 5000 IU UF-heparin or 5000 IU LMW-heparin were given intravenously followed by saline, 5000 U protamine chloride or 5000 U protamine sulfate intravenously after the 10 min blood sample. Then serial blood samples for the measurement of TFPI activity and anti-factor Xa-activity were taken, in order to detect a possible relation between the remaining anti-factor Xa activity after neutralization of LMW-heparin with protamine and TFPI activity and to establish whether or not a rebound phenomenon of plasmatic TFPI occurs. There was no difference in the release and in the kinetics of TFPI by UF- and LMW-heparin with subsequent administration of saline. After administration of protamine TFPI activity decreased immediately and irreversibly to pretreatment values. There were no differences between protamine chloride and protamine sulfate on the effect of TFPI induced by UF- or LMW-heparin. No rebound phenomenon of TFPI activity occurred. In contrast anti-factor Xa- activity, as measured by the chromogenic S2222-assay, issued the known differences between UF- and LMW-heparin. The half-life of the aXa-effect of LMW-heparin was twice as long as of UF-heparin. Protamine antagonized UF-heparin completely and about 60% of the anti-factor Xa activity of LMW-heparin, using chromogenic S2222-method. No differences could be detected for protamine chloride and sulfate form of protamine. It is assumed that protamine displaces heparins from the binding sites of TFPI.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired fibrinolytic capacity and tissue plasminogen activator release in patients with restenosis after percutaneous transluminal coronary angioplasty (PTCA).

To assess the role of the fibrinolytic system in the pathogenesis of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we determined the components of this system in a retrospective study, including 16 patients with restenosis (gr. A) and 19 patients with long-term success (gr. B). In both groups at baseline fibrinolytic activity (FA) is unchanged, whereas tissue plasminogen activator antigen (tPA-Ag) is significantly increased (gr. A: 147.0%; gr. B: 139.8%; p less than 0.01). Fibrinolytic capacity (FC) and tPA-Ag release are significantly reduced in the restenosis group (FC: 46.5%, p less than 0.05; tPA-Ag release: 48.3%, p less than 0.01) compared to normal controls as well as to gr. B (FC: 84.3%, p less than 0.05; tPA-Ag release: 79.0%, p less than 0.05). Relating to the contact activation system, F XII (79.5%, p less than 0.05) is significantly, and F XI (82.3%) is clearly reduced in gr. A. Protein C (PC) is significantly elevated in gr. B (117.5%, p less than 0.05). There is a negative correlation between plasminogen activator inhibitor (PAI 1) and HDL-cholesterol (r = 0.37, p less than 0.05). It appears, that there is a typical pattern of defective fibrinolysis in patients with restenosis after PTCA and that this might be a pathogenetic factor in the development of restenosis.

Biological activity and safety of the subcutaneous administration of high doses of low molecular weight heparin for 8 days in human volunteers.

This study reports on the biological activity and safety of high dose low molecular weight (LMW) heparin therapy administered by two subcutaneous (s.c.) injections daily for 8 days in healthy human volunteers. Group 1 received 2 x 30 aPTT units LMW heparin/kg bodyweight, and group 2 received 2 x 50 aPTT units/kg per day. In group 1, activated partial thromboplastin time (aPTT) and thrombin clotting time (TCT) were uniformly prolonged by 3-5 sec 4 hrs after s.c. administration of heparin. Heptest coagulation time values were prolonged consistently as well by 57 sec on day 1 to 68 sec on day 8. Factor Xa inhibition measured by the S 2222 chromogenic substrate method continuously increased from 0.16 units/ml on day 1 to 0.28 units/ml on day 8. In group 2 prolongation of a aPTT and TCT values increased from 6 sec on day 1 to 15 sec on day 8 and of Heptest time from 70 sec on day 1 to 110 sec on day 8. S 2222 method showed factor Xa inhibitory activity which increased from 0.5 units/ml on day 1 to 0.75 units/ml on day 8. The clinical tolerance of the treatment was good. No changes in clinical chemistry parameters were detected, except for a reversible increase of serum transaminases. The coagulation studies demonstrate accumulation of LMW heparin when high doses are given twice daily. The half life of LMW heparin of factor Xa inhibition increases with increasing doses. Heptest coagulation values were prolonged to 4-6 times the normal values during administration of heparin.(ABSTRACT TRUNCATED AT 250 WORDS)

Monitoring of heparin and low molecular weight heparin with capillary and venous whole blood.

A method for determination of antifactor Xa-like activity in capillary whole blood obtained from the fingertip is described, which employs the Heptest coagulation assay. Values obtained with capillary whole blood are compared to values of corresponding plasma and venous whole blood samples. Normal values in plasma, venous whole blood, and capillary blood from the fingertip were 17.1 +/- 2.1, 10.0 +/- 1.3 and 10.4 +/- 1.3 sec, respectively. The intraindividual coefficients of variations range from 0.4 to 1.8% in all assays. The day to day coefficient of variation of normal values ranged between 0.8 and 2.0% for all assays. The within assay coefficients of variation ranged from 3.0 to 7.7% for whole blood samples and from 1.5 to 2.2% for plasma samples after addition of no, 0.2 or 1.0 units of normal or LMW heparin to the samples. After administration of heparin or LMW heparin in healthy persons the coagulation values of the different coagulation assay systems displayed coefficients of correlation between r = 0.87 and r = 0.95. Correlation coefficients between the coagulation tests and the S 2222 chromogenic substrate method ranged from r = 0.77 to r = 0.92. In patients, who received LMW heparin for prophylaxis of thromboembolism the coagulation assay correlated between r = 0.78 and 0.92. The coagulation assays and the S 2222 method displayed coefficients of correlation between r = 0.74 and r = 0.83. The data indicate that Heptest sensitively measures antifactor Xa-like activity in capillary whole blood as well as venous whole blood samples containing low quantities of heparin or LMW heparin.