Wolfram Ehrenthal

Influence of blood sampling from venipunctures and catheter systems on serial determinations of prothrombin activation fragment 1 + 2 and thrombin-antithrombin III complex.

SummaryTo evaluate the influence of different blood sampling techniques on test results of thrombin-antithrombin III complex (TAT) and prothrombin fragment 1+2 (F1+2) serial determinations were performed. In six groups of nonrandomized patients (ten patients each) the concentrations of the coagulation markers of blood samples from central catheters (internal jugular, caval, Shaldon, pulmonary artery) and peripheral cannulas (17G and 18G) were compared with those of blood samples obtained simultaneously from direct venipunctures of the contralateral arm. Medians and 25th–75th percentiles of TAT and Fl+2 concentrations of plasmas obtained from central catheters were not different from those taken from venipunctures. When Δ mean values (catheter — venipuncture) were calculated negative results were obtained, indicating lower concentrations measured from blood sampled through central catheters with the exception of blood that taken from Shaldon catheters. Only for TAT concentrations significantly were lower values measured in blood samples taken from internal jugular catheters when compared with blood samples obtained from direct venipunctures. Significantly higher TAT concentrations were determined in blood samples obtained from Shaldon catheters. For both coagulation markers correlations were found between concentrations in blood samples from central catheters and venipunctures. In blood samples taken from peripheral venous cannulas only F1+2 concentrations correlated with the concentrations found in samples from direct venipuncture. In contrast to F1+2, TAT concentrations measured from blood samples via peripheral cannulas were determined significantly higher than those taken from direct venipunctures. Blood drawn from peripheral catheters is not suited for the determination of TAT and F1+2 due to frequently encountered activation of coagulation, while blood sampling with central catheters can be regarded as an alternative to venipuncture.

Evaluation of an automated chromogenic substrate assay for the rapid determination of hirudin in plasma

A fully mechanized chromogenic substrate assay method for the rapid and specific determination of recombinant hirudin (r-hirudin) in citrated plasma on clinical chemistry analyzers (Hitachi 911 and Cobas Mira) is described. In a first step, 12 microliters sample volume is mixed with the chromogenic substrate. Due to the almost immediate action of hirudin the inhibitory reaction and the cleavage of the substrate is started simultaneously when bovine thrombin is added in excess. This excludes interferences by antithrombin III or heparin cofactor II. The change in absorbance/min is recorded at 405 nm. The measuring range is about 0.2-4.0 mg/l r-hirudin on both analyzers. Precision is characterized by intraassay coefficients of variation between 0.63% and 2.78% on the Hitachi 911 and 1.51% and 7.84% on the Cobas Mira, respectively and interassay coefficients of variation of 3.57% to 9.15% (Hitachi 911) and 3.72% to 12.99% (Cobas Mira) for the same r-hirudin plasma concentrations. The described determination of r-hirudin correlates well with an enzyme linked immunosorbent assay method for r-hirudin (Hitachi 911: r = 0.964, y = 0.978x + 0.038, n = 323; Cobas Mira: r = 0.964, y = 0.959x-0.003, n = 323).

Monitoring prothrombin fragment 1+2 during initiation of oral anticoagulant therapy after intracoronary stenting

SummaryPatients with intracoronary stent implantation are treated with aggressive anticoagulant and antiplatelet therapy consisting of high-dose heparin, phenprocoumon, acetylsalicylic acid, dipyridamole, and the infusion of dextran to prevent a subacute thrombotic occlusion of the stented segment. In an effort to optimize this treatment by reducing both imminent bleeding complications and subacute thrombotic occlusion, the concentrations of prothrombin fragment 1+2 (F1+2) were determined after intracoronary Palmaz-Schatz stent implantation in 19 consecutive patients. The F1+2 concentrations after stent implantation and before the initiation of oral anticoagulant therapy (OAT) were 0.35 nm/l and 0.25–0.53 nm/l (median and 25th–75th percentile), versus 0.74 nm/l and 0.52–0.78 nm/l, in healthy subjects and 0.61 nm/l and 0.30–1.02 nm/l in 15 patients with ongoing proximal DVT. Nine days after initiation of OAT, F1+2 concentrations in both patient groups had not yet reached levels observed in patients with OAT in the stable state (0.16 nm/l, 0.12–0.26 nm/l;n=76;P<0.0001 compared with healthy subjects; INR 2.0–4.5). Despite an INR greater than 2.0, accompanying heparinization was terminated on day 9. In two stented patients a minor bleeding complication arose after the removal of the arterial catheter. Subacute thrombotic occlusions were not observed. Since F1+2 concentrations did not exceed the upper limit of normal range (1.11 nm/l) in any of the 19 patients, the therapeutic regimen was not changed. Monitoring F1+2 may thus be helpful in introducing a more individual treatment if aggressive anticoagulation has to be performed.

Nonradical oxidants of the phagocyte type induce the activation of plasmatic single chain- urokinase

Single chain- urokinase (scu-PA) is the proenzyme of the plasminogen activator urokinase (tcu-PA). In human blood scu-PA is of great stability. Activated phagocytes generate large amounts of single chain- urokinase and of reactive oxidants (chloramines and HOCl). Since these cells participate in physiologic fibrinolysis, we were interested in the interaction between plasmatic scu-PA and chloramines. The oxidants dose dependently induce the activation of plasmatic scu-PA. Optimal activation of scu-PA occurs at about 3-5 mmol/l of chloramine-T. The findings suggest a control mechanism of scu-PA stability/activity by oxidatively modifiable plasma proteins, such as alpha-2-antiplasmin. The oxidation mechanism seems to be mediated by singlet molecular oxygen, an excited oxygen species. Basing on this scu-PA/oxidant synergism a sensitive and fast functional assay of scu-PA in human plasma is presented. Plasmatic inhibitors normally interfering with functional scu-PA measurements are inactivated by addition of chloramine-T, imitating the physiological oxidants generated by activated phagocytes. The scu-PA concentration in plasma of n = 36 healthy individuals has been determined to be 5.8 +/- 1.6 ng/ml. The lower detection limit of plasma scu-PA by the procedure described is about 1.5 ng/ml of plasma. By means of this technique scu-PA concentration during thrombolytic therapy can be measured within minutes in undiluted (direct) plasma samples, allowing adjustments of the scu-PA dosage. The present study gives further credence for a role of singlet molecular oxygen, possibly a new type of locally acting hormones (autacoid), in the regulation of the fibrinolytic pathway.

Acute dialysis: PMN-elastase as a new parameter for controlling individual anticoagulation with low molecular weight heparin (Fragmin).

Despite the improvements in the development of dialyzer membranes with greater hemocompatibility, an activation of the coagulation system occurs when blood comes into contact with exogenous surfaces. The large number of heparin dosage regimens demonstrate the difficulty to adapt general therapeutic guidelines. Low molecular weight heparin (Fragmin®) was administered as a single bolus dose for anticoagulation during 58 acute dialyses. Anti-Xa-activity, the plasma levels of the lysosomal elastase of the polymorphnuclear granulocytes (“PMN-elastase”) and of the thrombin-antithrombin III-complex (TAT) were measured at hourly intervals. Therapeutic anti-Xa-levels did not show evidence of sufficient inhibition of thrombin formation. The PMN-elastase increased by 180 ng/ml 3 h after administration of the bolus dose, with no further increase occurring (plateau phase). This was considered to reflect adequate anticoagulative activity. Where anticoagulation was inadequate, the elastase values rose consistently. After 2 h the increase of the PMN-elastase showed that — and to what extent — coagulation had been activated. The determination of PMN-elastase, using the IMAC-principle, is a method which can be performed quickly with any conventional autoanalyzer. It makes it possible to monitor adequate anticoagulation, but PMN-elastase results must be proven during routine use before recommendation as a routine test.

Biochemical bone markers compared with bone density measurement by dual energy X-ray absorptiometry.

In contrast to medical imaging, the biochemical markers allow a more frequent determination and are not as invasive as histomorphometric methods. We investigated biochemical markers of type I collagen compared with bone density measurements in 85 females between 41 and 89 years of age (median: 57 years). The bone density measurements were performed by dual-energy X-ray absorptiometry (DXA) on the lumbar spine (L1–4). The bone density measurements were stated as percentage of the norm. All patients were divided into three groups: I=<80%; II=80–120%; III=>120%. Based on this classification the median concentration of the I-carboxyterminal propeptide of type I procollagen in serum (S-PICP) as an anabolic marker of type I collagen increased significantly with rising bone density: I 65.0* μg/liter (interquartile range: 52.1–78.0 μg/liter); II 85.9* μg/liter (52.1–115.5 μg/liter); III 81.4 μg/liter (62.0–101.0 μg/liter); *P<0.05. The concentration of urinary pyridinolines (U-PYR) as a marker for degradation of type I collagen decreased. The I-carboxyterminal telopeptide (S-ICTP) and osteocalcin (S-BGP) did not change. The multivariate regression analysis showed no relationship between bone density measurement and biochemical bone markers. Only the age significantly correlated negatively with bone density measurement. For a better assessment of type I collagen metabolism we created a “b-quotient” by dividing the sum of S-PICP and S-BGP by U-PYR. The median b-quotient increased significantly: I 1.55*+ (0.97–2.04); II 2.09* (1.57–2.86); III 2.46+ (1.58–3.22);*+P<0.05. Changes in bone metabolism cannot be identified by the determination of a single marker. However, the improved biochemical diagnostic measurement using the b-quotient may provide early information about the progression of a metabolic disorder within the interval of imaging.

Immunonephelometric determination of the C4B-binding protein

A fully mechanised immunonephelometric method for the rapid and specific determination of C4b-binding protein (C4b-BP) in citrated plasma is described. The method utilizes commercially available rabbit antiserum against human C4b-BP and a nephelometer analyser. A single determination can be performed within 6 min, requiring 80 microliters sample volume. The measuring range is about 10 to 200% of normal C4b-BP. Precision is characterized by intraassay coefficients of variation between 1.5% and 2.8%, and interassay coefficients of variation between 4.0% and 4.6% for the same C4b-BP concentrations. The nephelometry of C4b-BP was correlated with electroimmunodiffusion (Laurell technique; r = 0.863, y = 0.909x+7.091, n = 79). C4b-BP concentrations (143%, 96-223%; median and 2.5th-97.5th percentile) from 83 subjects with increased inflammation markers C-reactive protein (> 10 mg/l), and fibrinogen (> 4.5 g/l) showing significantly higher C4b-BP concentrations compared to 151 obviously healthy subjects (97%, 68-141%; p < 0.001). In contrast to 81 patients with therapeutic heparinisation (90%, 60-131%) significant decreased concentrations were found in 90 subjects under oral anticoagulant therapy (OAT) in the stable state (78%, 44-125%; p < 0.001). Depending on different INR levels (< 2.5, n = 40: 71%, 63-85%; > 2.5, n = 50: 81%, 68-92%; median and 25th-75th percentile) no significant differences of C4b-BP concentrations could be measured.