PubMed Health⌕ Search

Biomedical subjects

F Brosstad

Publications and source records attributed to F Brosstad.

At least 37 records · Page 2Linked to original sources
PubMed2000

Persistently elevated levels of von Willebrand factor antigen in HIV infection. Downregulation during highly active antiretroviral therapy.

Levels of circulating von Willebrand factor (vWf) antigen are thought to reflect endothelial involvement in various disorders. In the present study we found markedly elevated plasma levels of vWf in HIV-infected patients demonstrated on both cross-sectional and longitudinal testing. Notably, we found that a persistent rise in vWf antigen was associated with progression of HIV-related disease. This elevation of vWf antigen represented functionally normal vWf as evaluated by plasma FVIII, ristocetin cofactor assay and vWf multimer analyses. While HIV-infected patients showed enhanced platelet activation, platelets did not contribute substantially to the increased vWf levels. The high vWf levels were significantly correlated with high viral load, and during HAART, the pronounced decline in HIV RNA levels was accompanied by a corresponding decrease in vWf. The persistent elevation of functionally normal vWf during HIV infection, most probably reflecting a persistent endothelial cell activation, may have an important role in the pathogenesis of HIV infection.

Adult↗
PubMed1999

Assessment of heparin anticoagulation: comparison of two commercially available methods.

BACKGROUND: The activated clotting time is a bedside method routinely used to monitor heparin anticoagulation during operations requiring cardiopulmonary bypass. The thrombolytic assessment system heparin management test is a new bedside method for monitoring heparin effect. We compared these methods with respect to their ability to reflect the actual heparin concentration in plasma determined by an anti-FXa method. METHODS: Two studies were done, an ex vivo study on ten patients who had coronary artery bypass using non-heparin-coated cardiopulmonary bypass circuits and full systemic heparinization and an in vitro study on single donor plasma spiked with heparin 0 to 10 IU/mL. RESULTS: Ex vivo study correlation coefficients of activated clotting time and the thrombolytic assessment system heparin management test clotting times versus anti-FXa-based heparin assay were low (r = 0.53, p = 0.002/r = 0.64, p<0.001) in contrast with the corresponding correlation coefficients for the in vitro study (r = 0.98, p<0.001/r = 0.99, p<0.001). A substantial variability in duplicate activated clotting time determinations was noted, which was less pronounced with the thrombolytic assessment system heparin management test. CONCLUSIONS: The thrombolytic assessment system method does not correlate better to the actual amount of heparin during cardiopulmonary bypass procedures than the activated clotting time method, which should be performed in duplicate.

Anticoagulants↗
PubMed1999

Autotransfusion in coronary artery bypass grafting: disparity in laboratory tests and clinical performance.

OBJECTIVE: Autotransfusion during and after cardiac surgery is widely performed, but its effects on coagulation, fibrinolysis, and inflammatory response have not been known in detail. METHODS: Hemostatic and inflammatory markers were extensively studied in 40 coronary artery bypass patients undergoing a consistent intraoperative and postoperative autotransfusion protocol. An identical autotransfusion protocol was applied to 4916 consecutive coronary patients and the overall clinical results were evaluated in this large patient population. RESULTS: The autologous blood pooled before bypass remained nearly inactivated after storage. A slight elevation of thrombin-antithrombin complex and prothrombin fragment 1.2, as well as plasmin/alpha(2)-antiplasmin complex was found in the content of the extracorporeal circuit after surgery, indicating thrombin formation and fibrinolytic activity. Also some increase of beta-thromboglobulin was present. In the mediastinal shed blood, complete coagulation, as evidenced by the absence of fibrinogen, had taken place and all parameters described above were extremely elevated. However, no thrombin activity was detected. As for the inflammatory response, moderately increased levels of complement activation products, terminal complement complex, and interleukin-6 traced in the extracorporeal circuit reached very high levels in mediastinal shed blood. Autotransfusion of the residual extracorporeal circuit blood and the mediastinal drainage was followed by elevation of most of these markers in circulating plasma. On the other hand, no correlating harmful effects were recorded in the study patients or in the consecutive 4916 patients. Coagulation disturbances were rare and allogeneic transfusions were required in fewer than 4% of all patients. CONCLUSIONS: The hemostatic and immunologic systems were moderately activated in the autologous blood remaining in the extracorporeal circuit, whereas the mediastinal shed blood was highly activated in all aspects. However, autotransfusion had no correlating clinical side-effects and the subsequent exposure to allogeneic blood products was minimal.

Aged↗
PubMed1999

Selective venous thrombolysis with the nipple-balloon catheter: comparative evaluation in vivo.

PURPOSE: To compare in an animal model of deep vein thrombosis, an intramural drug delivery catheter, the nipple-balloon catheter, with an occlusion balloon-infusion guide wire system. MATERIALS AND METHODS: Ten juvenile pigs were used for the study. Deep vein thrombosis was induced in both hind limbs by using a previously described technique. Heparin was administered 30 minutes later (2,500 IU intravenously) and bilateral thrombolysis was attempted with use of 8 mg of alteplase as a 0.25 mg/mL solution containing heparin 50 IU/mL (n = 10) and sodium/meglumine ioxaglate 40 mgI2/mL (n = 5). In one limb, the external iliac vein was endoluminally occluded, and 0.8 mL of alteplase was administered every 3 minutes through a multisideport infusion wire placed coaxially through the balloon catheter. On the other side, a nipple-balloon catheter was used: alteplase was injected as two 0.4-mL aliquots every 3 minutes in overlapping segments of the vessel. Blood samples were taken at predetermined intervals to determine the partial thromboplastin time and plasma fibrinogen concentration. At autopsy, the thrombus mass in the iliofemoral veins was measured, and the extent of residual thrombosis in the venous tributaries was graded at four sites. The heart and the lungs were also examined for thromboemboli (n = 5). Venous specimens were then subjected to X-ray fluorescence spectrometry to determine iodine content (n = 5). RESULTS: Bilateral thrombolysis could be successfully completed in all animals. No procedural problem associated with the use of the nipple-balloon catheter was encountered. The mass of residual thrombus in the axial veins was significantly lower in this group (P = .005). The drug delivery system used did not appreciably influence thrombolysis in the tributaries. Signs of macroscopic damage to the veins were not observed in any animal. None of the venous specimens had detectable levels of iodine. Small thromboemboli were found in the pulmonary circulation in three of five animals. Fibrinogen levels did not decrease during the procedure. CONCLUSIONS: The significantly lower residual thrombus burden associated with use of the nipple-balloon catheter suggests that the device may have the potential to be an effective delivery system for selective thrombolysis in veins.

Animals↗
PubMed1999

A single dose of dalteparin effectively prevents clotting during haemodialysis.

BACKGROUND: A single bolus dose of LMW heparin at the start of haemodialysis effectively prevents clot formation in the dialyser and bubble trap. However, there are few studies on the appropriate dosage of LMW heparins in haemodialysis. Therefore we examined the relationship between the anticoagulant effect of dalteparin and clinical clotting during haemodialysis. METHODS: We performed an open, prospective study on the effect of decreasing doses of dalteparin in 12 haemodialysis patients during a total of 84 sessions (4-4.5 h). The normally applied dose of dalteparin in each patient was reduced by 25% for each session down to 50% of initial dose if no clotting was observed. Clinical clotting (grade 1-4) was evaluated by visual inspection after blood draining of the air trap every hour and by inspection of the dialyser after each session and compared to corresponding values for anti-FXa activity and dialysis time. Blood flow and ultrafiltration rate were kept within narrow limits throughout the study. RESULTS: No episodes of grade 4 clotting occurred, and no session was interrupted. Eighteen episodes of grade 3 clinical clotting (11%) were observed in patients without warfarin treatment, none with an anti-FXa activity >0.43 IU/ml. Oral warfarin treatment reduced the clinical clotting, and only one grade 3 episode was observed in patients on warfarin therapy. Anti-FXa activity and haemodialysis time were the only factors independently correlated to clotting in a logistic regression model. CONCLUSION: An anti-FXa activity above 0.4 IU/ml after 4 h of dialysis inhibits significant clotting during haemodialysis. A bolus dose of dalteparin of 70 IU/kg usually seems appropriate, but may be reduced in patients on warfarin treatment. Dialysis time is an independent risk factor for clinical clotting.

Adult↗
PubMed1999

Soluble, thrombin-related material in arterial thrombi and plasma studied during catheter-directed intra-arterial thrombolysis.

We investigated soluble, thrombin-related material in arterial thrombi and venous plasma during catheter-directed thrombolysis with alteplase. Arteriography was performed before thrombolysis and 0.5, 3, 10 and 24 h after the onset of treatment in six patients with (sub)acute lower extremity ischaemia caused by native artery or bypass occlusion. Samples were collected simultaneously from the thrombus and venous blood. After adding inhibitors of thrombin and plasmin, the centrifuged samples were assayed for prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT) and fibrinopeptide A (FPA). Levels of F1+2, TAT and FPA were extremely elevated in the thrombus-related samples before the blood flow was re-established (at 0 and 0.5 h) in all five successfully treated patients. In comparison, venous plasma levels of F1+2, TAT and FPA were moderately elevated, and reached a maximum at 3 h. In conclusion, material aspirated from lysing human thrombi formed in vivo contains large amounts of F1+2, TAT and FPA, but our methods prevented us from detecting enzymatically active thrombin.

Aged↗
PubMed1999

Fibrinogen, fibrin and its degradation products in drained blood after major orthopaedic surgery.

The aim of this study was to evaluate the fibrinogen enzymatic conversion in blood collected postoperatively from a surgical wound. Ten otherwise healthy patients (aged 11-28 years) in need of surgical treatment for thoracic scoliosis were included in the study. Arterial blood preoperatively and at wound closure were compared with samples of drained blood from the wound at closure and from a collection system for autologous transfusion 2.8 +/- 1.1 h later. There was a decrease in the fibrinogen content in arterial blood from 2.17 +/- 0.35 g/l to 1.23 +/- 0.42 g/l, which followed a 40% haemodilution estimated from the blood loss of 1.6 +/- 0.9 l during the operation. Drained blood contained high concentrations of D-dimer (85 +/- 53 mg/l from the wound and 121 +/- 47 mg/l from the collection system), but no clottable fibrinogen. The Western immunoblots all visualized the same patterns; in drained blood there were split-products mainly from cross-linked fibrin, in contrast to arterial blood which contained only normal fibrinogen. This indicates a strong fibrinolysis in the surgical wound after closure, with concentrations of fibrin degradation products that may impair local coagulation, and if infused, might interfere with general haemostasis.

Adolescent↗
PubMed1999

The activation of platelet function, coagulation, and fibrinolysis during radiofrequency catheter ablation in heparinized patients.

INTRODUCTION: Catheter ablation may be complicated by clinical thromboembolism in about 1% of patients. METHODS AND RESULTS: We studied the activation of coagulation (prothrombin fragment 1+2 [PF1+2]), platelets (beta-thromboglobulin [beta-TG])) and fibrinolysis (plasmin-antiplasmin complexes [PAP] and D-dimer) during radiofrequency (RF) ablation in 13 patients. They received heparin 100 U/kg intravenously after the initial electrophysiologic study, prior to the delivery of RF current; thereafter 1,000 U/hour throughout the procedure. PF1+2 increased fourfold (P < 0.001) during the diagnostic study, but gradually declined to upper reference value during heparin administration. There was a strong correlation between procedure duration prior to heparin bolus (range 39 to 173 min); and (a) the maximal rise of PF1+2 (r = 0.83, P < 0.001) and (b) the increase of PF1+2 from baseline to end of the procedure (r = 0.74, P = 0.004). There was no correlation between postheparin changes of PF1+2 and (a) postheparin procedure duration (range 40 to 317 min), (b) number of RF pulses (range 1 to 16), or (c) RF current duration (range 46 to 687 sec). Plasma beta-TG concentration showed similar trends. Fibrinolytic activity increased moderately from baseline until heparin administration; then remained around the upper reference values. PAP at the end of procedure and D-dimer at the time of heparin administration both correlated with preheparin procedure duration (r = 0.70, P = 0.007 and r = 0.69, P = 0.01, respectively). All parameters were normal the next morning. CONCLUSION: Procedure duration prior to heparin administration, and not the delivery of RF current per se, determines activation of hemostasis and fibrinolysis during RF ablation.

Adolescent↗
PubMed1999

Leucocyte filtration during cardiopulmonary reperfusion in coronary artery bypass surgery.

Postoperative organ dysfunction after cardiac operations has been related to the damaging effects of cardiopulmonary bypass (CPB). These complications are considered to be mediated partly by complement activation and subsequent activation of leucocytes due to the contact between blood and the large nonendothelial surfaces in the bypass circuit. Removal of leucocytes by filtration during the reperfusion period may potentially reduce the postoperative morbidity after CPB. Forty patients undergoing elective, primary coronary artery bypass grafting were randomized to initial identical bypass circuits until the aortic crossclamp was released. Then, the ordinary arterial line filter was closed and either a leucocyte depletion filter (n = 20), or a control filter (n = 20) was incorporated in the circuits during the reperfusion period of CPB. Blood samples were drawn at fixed intervals and analysed for white blood cell and platelet counts, plasma concentration of myeloperoxidase, C3-complement activation products, the terminal complement complex, and interleukins (IL)-6 and -8. The numbers of circulating white blood cells in the leucocyte-depleted group decreased during the reperfusion period from 5.5 (4.8-6.8) to 5.3 (4.4-6.2) x 10(9)/l, and increased in the control group from 6.5 (5.1-8.0) to 7.4 (5.7-9.0) x 10(9)/l. Two hours postoperatively the total white blood cell count in the leucocyte-depleted group was 14.7 (12.1-17.2) x 10(9)/l, and in the control group 17.6 (14.5-20.7) x 10(9)/l. The differences between the groups were statistical significant (p = 0.05). There were no statistically significant differences between the groups with regard to other test parameters or clinical data. We conclude that the use of leucocyte filters during the reperfusion period in elective coronary artery bypass surgery significantly reduced the number of circulating leucocytes, whereas no effects were seen for granulocyte activation measured as myeloperoxidase release, platelet counts, complement activation, or IL-6 and -8 release. The clinical benefit of leucocyte filters in routine or high risk patients remains to be demonstrated and is suggested to be dependent on both the efficacy and the biocompatibility of the filters.

Aged↗
PubMed1999

Comparison of three oxygenator-coated and one total-circuit-coated extracorporeal devices.

The present study was designed to compare the biocompatibility of three cardiopulmonary bypass setups with different surface coatings, and to determine if coating of the whole circuit with one of the coatings was more beneficial than coating of the oxygenator only. Extracorporeal devices entirely coated with synthetic polymers (Avecor, n = 6) were compared to oxygenators coated with synthetic polymers (Avecor, n = 6), end-point, covalently attached heparin (CBAS, n = 6) or absorbed heparin (Duraflo 2, n = 6) in an in vitro model of a heart lung machine. The circuits were primed with fresh human whole blood and Ringer's acetate and recirculated at 4 l/min at 30 degrees C for 2 h. Test samples were obtained at regular intervals and analysed for myeloperoxidase (MPO), platelet counts, beta-thromboglobulin, heparin, prothrombin fragment 1+2, plasmin anti-plasmin complexes, and complement activation products. The mean MPO concentrations increased in the Avecor-coated oxygenator group (AV) from 247 at the start to 671 microg/l at the termination of the experiments, in the Avecor-coated total circuit group (AV-T) from 116 to 288 microg/l, in the Duraflo 2 coated oxygenator group (DU) from 160 to 332 microg/l, and in the CBAS-coated oxygenator (CA) group from 172 to 311 microg/l. The MPO concentrations increased significantly in all groups (p < 0.03). The increase in group A was significantly higher than in the other three groups (p = 0.007). The mean platelet counts decreased in the Avecor-coated total circuit group from 117 at start to 99 x 10(9)/l at termination of the experiments, in the Avecor-coated oxygenator group from 119 to 103 x 10(9)/l, in the Duraflo 2 group from 96 to 86 x 10(9)/l, and in the CBAS group from 132 to 123 x 10(9)/l. The platelet counts decreased significantly in all groups (p < 0.01), but the intergroup differences were not significant (p = 0.15). The mean beta-thromboglobulin concentrations increased in the Avecor-coated total circuit group from 193 at the start to 754 ng/ml at the termination of the experiments, in the Avecor-coated oxygenator group from 474 to 1654 ng/l, in the Duraflo 2 group from 496 to 1280 ng/l, and in the CBAS group from 418 to 747 ng/l. The beta-thromboglobulin increase was significant in each group (p < 0.01), but not between the groups (p = 0.49). The mean heparin concentrations in the Duraflo 2 group increased from 2460 at the start to 2897 IU/l at termination of the experiments, in the CBAS group from 2468 to 2518 IU/l. In the Avecor-coated oxygenator group heparin concentrations decreased from 2010 to 1968 IU/l, and in the Avecor-coated total circuit group from 2002 to 1927 IU/l. The differences in heparin concentrations were significant between the Duraflo 2 group and the other groups (p < 0.05). The mean prothrombin fragment 1+2 concentrations increased in the CBAS group from 0.4 at the start to 2.1 nmol/l at the end of the experiments, in the Avecor-coated oxygenator group from 0.4 to 0.6 nmol/l, in the Avecor-coated total circuit group from 0.3 to 0.4 nmol/l, and in the Duraflo 2 group from 1.2 to 1.3 nmol/l. The prothrombin fragment 1+2 increase was significant in all groups (p < 0.05), but there were no significant intergroup differences (p = 0.54). There were no significant differences at the termination of the experiments among the four groups regarding complement activation as measured by C3 activation products and the terminal complement complex. In the present in vitro model of a heart-lung machine, none of the three specific setups with different coatings was superior with regard to all test parameters. The CBAS group generated the highest levels of prothrombin fragment 1+2 formation, but least complement activation. The increasing plasma heparin concentrations in the Duraflo 2 group indicated more unstable heparin bonding. The Avecor-coated total circuit group were superior to the Avecor-coated oxygenator group regarding plasma concentrations of MPO, but not compa

Antifibrinolytic Agents↗
PubMed1999

Is a prolonged bleeding time associated with an increased risk of hemorrhage after liver biopsy?

Bleeding time determination is not advised as a general preoperative hemostasis screening test, but it might be useful in some patient groups. Patients referred for liver biopsy frequently have coagulation disturbances and are at risk of hemorrhage. In this prospective study 219 liver biopsies were carried out regardless of a prolonged bleeding time, but with minimum requirements for hemoglobin concentration, platelet count, and tests of the internal and external coagulation pathways. The bleeding time was prolonged in the case of 48 (22%) of the biopsies. Significant bleeding as defined by a hemoglobin decrease of > or =2.0 g/dl occurred in nine patients. Three of these patients were bone marrow transplanted. Patients with a prolonged bleeding time carried a five times higher risk of bleeding (odds ratio = 5.0; confidence interval = 1.1-21.8; p = 0.019). We conclude that the bleeding time may give additional information on the risk of bleeding in some patient groups undergoing liver biopsy.

Adolescent↗
PubMed1999

Catheter-directed intra-arterial thrombolysis: size of soluble fibrin(ogen) degradation products studied by electrophoresis and immunoblotting.

The aim of this study was to investigate the proteolytic degradation of fibrin(ogen), with special emphasis on the size of soluble fibrin(ogen) derivatives identified before, during and after intra-arterial catheter-directed thrombolysis with alteplase. Arteriography was performed before thrombolysis and after 0.5, 3, 10 and 24 h in six patients with peripheral native artery or bypass occlusions. Samples collected simultaneously intra-arterially from the thrombus and from venous blood were studied by immunoblotting patterns obtained after polyacrylamide and agarose gel electrophoresis. Supernatant from centrifuged material aspirated from the thrombus before thrombolysis contained soluble fibrin(ogen) derivatives with molecular weights of several thousand kDa. Two types of soluble fibrin(ogen)-related material were visualized during treatment: high molecular weight species (500-1000 kDa) displaying an almost continuous spectrum of molecular weights, suggesting gradual proteolytic degradation of cross-linked fibrin into X-oligomeric material; and X, Y, DD, D and E fragments. The amount and distribution of fragments strongly indicated that preferential fibrinolysis had taken place. The finding of a sustained level of fragments in post-thrombolytic plasma might indicate that insoluble fragments embolize peripherally and subsequently lyse. A close association between angiographical and molecular findings during both successful and failing thrombolysis was demonstrated.

Aged↗
PubMed1998

Quantitative evaluation of selective thrombolysis techniques: influence of catheter characteristics and delivery parameters.

Here, we evaluate in vitro the site-specific delivery ability of thrombolysis catheters and compare continuous infusion (CI) and periodic injection (PI) protocols with reference to this parameter. Thrombotic occlusion was simulated by placing a porcine blood clot proximal to an eccentric stenosis in a flow phantom. Iodinated contrast agent was used as the marker. Part I-Evaluation of thrombolysis catheters: four CI and three PI catheters were tested. The marker was delivered as an infusion at 1 ml/min for 1 min (CI), or as two 0.25 ml boluses 30 sec apart (PI). Iodine content of the clot was then estimated with x-ray fluorescence spectrometry. This value as a ratio of the delivered dose was defined as the targeting efficiency. Part II-Evaluation of thrombolysis protocols: CI and PI were compared. The marker was delivered for 3 or 5 min using one of seven protocols. The iodine content of both clot and effluent were estimated. Among PI catheters, the Jet-Lysis catheter proved to be the best (P = 0.02). The EDM catheter had the lowest targeting efficiency in the CI group (P = 0.01). With CI, median iodine recovery dropped from 0.21 (95% confidence interval: 0.08, 0.25) for 1 min to 0.13 (0.05, 0.16) for 3 min and 0.07 (0.03, 0.10) for 5 min; for PI the values remained unchanged. The fraction lost in the effluent increased with the duration of regimen with both CI (P = 0.014) and PI (P = 0.004). Reducing the rate of infusion or the bolus frequency resulted in major improvements with respect to this parameter (P = 0.005). For CI, the targeting efficiency increased as well (P = 0.03). We conclude that currently used thrombolysis protocols do not fully exploit the delivery advantage offered by CI or PI. Fortunately, simple modifications offer the possibility of overcoming these drawbacks.

Animals↗
PubMed1998

Enhanced activation of platelets with abnormal release of RANTES in human immunodeficiency virus type 1 infection.

Besides their role in hemostasis, platelets are involved in inflammatory and immunological processes, and we hypothesize that platelet activation may play an immunopathogenetic role in HIV-1 infection. Blood was drawn from 15 controls and 20 HIV-1-infected patients with normal platelet counts, classified into groups of non-AIDS and AIDS. Platelet activation was detected using flow cytometry with mAbs against the release markers P-selectin and CD63, mAb against GPIb, and the probe annexin V detecting surface exposure of aminophospholipids. The amount of microvesicles was measured using mAb against GPIIIa. Compared to controls, blood samples from HIV-1-infected patients showed significantly enhanced levels of microvesicles and activated platelets as detected by their exposure of P-selectin, CD63, and aminophospholipids, as well as reduction in GPIb expression. Increased expression of P-selectin and amounts of microvesicles were most pronounced in advanced clinical and immunological disease. When studying the effect of HIV-1 protease inhibitor therapy (indinavir) on platelet activation, we found that concomitant with a profound decrease in plasma viral load, there was a near normalization of several of the parameters reflecting enhanced platelet activation. Finally, we demonstrated that platelets may be an important source of the chemokine RANTES in HIV-1-infected patients. Although both unstimulated and SFLLRN-stimulated platelets from asymptomatic patients had enhanced release of RANTES, platelets from AIDS patients were characterized by markedly enhanced spontaneous, but decreased SFLLRN-stimulated release of this chemokine. Taken together, these results, which demonstrate for the first time increased platelet activation in HIV-1-infected patients with normal platelet counts, may represent a previously unrecognized immunopathogenic factor in HIV-1 infection.

Anti-HIV Agents↗
PubMed1998

Bronchoscopy with transbronchial biopsies: measurement of bleeding volume and evaluation of the predictive value of coagulation tests.

The objectives of this study were to measure the bleeding volume associated with fibreoptic bronchoscopy with transbronchial biopsies (TBB), to correlate it with coagulation tests and to compare bleeding volume in patients with and without lung transplant. A total of 104 consecutive TBB in 51 different patients was evaluated prospectively. Before each procedure, haemoglobin, blood platelets, prothrombin time (PT), activated partial thromboplastin time (aPTT) and bleeding time were measured. During the procedure, lavage fluid and blood were collected by suction. The haemoglobin concentration of the mixture was measured and bleeding volume was calculated. Clinically significant bleeding was arbitrarily defined as >20 mL blood present in lavage fluid. The mean+/-SD bleeding volume was 7+/-10 mL with no statistically significant difference between transplanted and nontransplanted patients. In eight procedures (7.7%) the bleeding volume was >20 mL (range 22-61 mL). Prebiopsy values for blood platelet counts, PT and aPTT did not predict a bleeding tendency in any of the procedures in which significant bleeding occurred. No correlation was found between bleeding time and bleeding volume in the 17 procedures performed in patients with a prolonged bleeding time (> or =10 min). The bleeding associated with transbronchial biopsies was usually minor and quantitatively similar in patients with or without lung transplant. Coagulation tests could not predict clinically significant bleeding, which may occur in patients with normal coagulation test results.

Adult↗
PubMed1998

Microvesicles bind soluble fibrinogen, adhere to immobilized fibrinogen and coaggregate with platelets.

In the present study we have investigated whether platelet derived microvesicles can bind soluble fibrinogen, bind to immobilized fibrinogen, and coaggregate with platelets. Flow cytometry was used for studies on binding of soluble fibrinogen and coaggregation, whereas ELISA wells were used to study binding of microvesicles to immobilized fibrinogen. Biotinylated microvesicles produced by stimulation with A23187, thrombin or SFLLRN of platelets which had been surface-labelled with biotin, were used both for the coaggregation experiments and for the binding studies with immobilized fibrinogen. Unlabelled microvesicles and biotinylated fibrinogen were employed when studying binding of soluble fibrinogen to the microvesicles. For the flow cytometry, the biotinylated proteins were reacted with avidin or streptavidin which was PE-conjugated, whereas the same substances were conjugated with alkaline phosphatase for the ELISA studies. The microvesicles formed after stimulation of platelets by SFLLRN or A23187 clearly bound the soluble, biotinylated fibrinogen. Moreover, isolated biotinylated microvesicles added to washed platelets prior to activation, were associated to the microaggregates that formed after stimulation. A significant binding of biotinylated microvesicles to immobilized fibrinogen could also be detected. The binding of microvesicles to soluble and immobilized fibrinogen and association to platelets was clearly specific and at least partly dependent on the GPIIb-IIIa complex, as all of these phenomena could be prevented or reduced by addition of the c7E3 Fab which blocks the activated form of this receptor complex. From these in vitro results it is clear that microvesicles can bind to immobilized fibrinogen, bind soluble fibrinogen and are able to coaggregate with platelets. It may be speculated that these results also reflect a haemostatic role of microvesicles in vivo.

Blood Platelets↗