High-dose fibrinogen versus a clinically recommended dose of fresh frozen plasma for reversal of dilutional coagulopathy in an in vitro model of severe hemodilution.

BACKGROUND: Volume substitution using colloids and crystalloids dose-dependently induces dilutional coagulopathy. For treatment, fibrinogen concentrate and fresh frozen plasma are options, though the effective dosage of either agent is unclear. The objective of this study was to evaluate, whether high-dose fibrinogen or recommended doses of fresh frozen plasma are equally effective in reversing profound dilutional coagulopathy in vitro. METHODS: Blood samples of ten healthy volunteers were diluted by 60% with normal saline, balanced 4% gelatin, or balanced 6% hydroxyethyl starch 130/0.42, and supplemented with either 85mg/kg fibrinogen concentrate or 20mL/kg fresh frozen plasma. Conventional coagulation assays (prothrombin time, activated partial thromboplastin time, plasma fibrinogen, factors V and VIII), and activated rotational thromboelastometry (EXTEM: clotting time, clot formation time, FIBTEM: maximum clot firmness) were performed in all samples. RESULTS: For saline and gelatin dilutions, plasma fibrinogen and thromboelastometry parameters normalized by fibrinogen concentrate, while conventional coagulation assays and factors V and VIII remained unaffectedly impaired. Fresh frozen plasma improved both conventional coagulation assays, coagulation factors, and thromboelastometry parameters in saline and gelatin dilutions. For hydroxyethyl starch dilutions, plasma fibrinogen increased by fresh frozen plasma, and even normalized by fibrinogen concentrate. Conventional coagulation assays and factors V and VIII improved by fresh frozen plasma only. Thromboelastometry parameters remained mainly unaffected impaired by both fibrinogen concentrate and fresh frozen plasma. CONCLUSION: High-dose fibrinogen concentrate and clinically recommended doses of fresh frozen plasma are equally effective and can partially restore viscoelastic coagulation assays in profound saline and gelatin dilutions, but only fresh frozen plasma improves conventional coagulation assays. Hydroxyethyl starch-induced disturbance of fibrin polymerization is neither restored by fibrinogen concentrate nor fresh frozen plasma.

[Patients with oral anticoagulation--bridging anticoagulation in the perioperative phase]. / Patienten unter oraler Antikoagulation--Perioperatives Bridging.

Oral anticoagulation with a vitamin K-antagonist requires special consideration when surgery or interventional procedures are planned. This is mainly due to the half life of vitamin K-antagonists and to the need for safe and effective anticoagulation prior to and during surgery as well as in the postoperative period. So far, the continuous infusion of unfractionated heparin (UFH) has been the medication of choice to "bridge" patients to surgery. The use of low molecular weight heparins (LMWH) has been prospectively investigated in this setting and represents a safe alternative. The advantages of LMWH are the better dose-response relationship and reduced need for monitoring. This facilitates the bridging procedure to be started out of hospital, which may reduce hospital stay and associated costs. Furthermore, the so-called bridging of patients with oral anticoagulation prior to and during surgery reduces bleeding complications and maintains a safe anticoagulation for patients at risk.

[Established anticoagulants in secondary haemostasis--Vitamin K antagonists, heparins]. / Etablierte Antikoagulanzien der sekundären Hämostase--Vitamin-K-Antagonisten, Heparine.

In respect to the actual discussion of new anticoagulants in secondary haemostasis, we will give a short review on established oral anticoagulation with vitamin K antagonists and parenteral anticoagulation by use of heparin. The different coumarin derivatives phenprocoumon, warfarin, and acenocoumarol are compared concerning to the management and influence of pharmacogenetic and pharmacokinetic factors. Studies to improve the safety of oral anticoagulation by vitamin K supplementation will be briefly discussed. The therapy with heparins include until now some problems of dose-response control. It is necessary to pay attention to contra-indications even for well known anticoagulants. Examples for that will be given.

[Preoperative identification of patients with impaired (primary) haemostasis. A practical concept]. / Präoperative Identifikation von Patienten mit (primären) Hämostasestörungen. Ein praktisches Konzept.

The findings of a large prospective study designed to identify primary and/or secondary haemostatic disorders before surgical interventions are presented. A total of 5649 unselected adult patients were enrolled to identify impaired haemostasis before surgical interventions. Each patient was asked to answer a standardized questionnaire concerning bleeding history. Activated partial thromboplastin time (aPTT), prothrombin time (PT), and platelet counts (PC) including PFA-100 (platelet function analyzer): collagen-epinephrine (C/E), and collagen-ADP (C/ADP) were routinely done in all patients. Additional tests, bleeding time (BT), von Willebrand factor (VWF:Ag, VWF:Rcof) and a further haemostaseological diagnostic was performed only in patients with a positive bleeding history and/or evidence of impaired haemostasis; e.g., drug ingestion. The bleeding history was negative in 5021 patients (88.8%) but positive in the remaining 628 (11.2%). Impaired haemostasis could be verified only in 256 (40.8%) of these patients. The vast majority was identified with PFA-100: C/E (n = 250; 97.7%). The sensitivity of the PFA-100: collagen-epinephrine was the highest (90.8%) in comparison to the other screening tests (BT, aPTT, PT, VWF : Ag). The positive predictive value (to detection of impaired haemostasis) of the PFA-100: collagen-epinephrine with the standardized questionnaire was high (82%), but the negative predictive value was higher (93%). The use of a standardized questionnaire and, if indicated, the PFA-100: C/E and/or other specific tests not only ensure the detection of impaired haemostasis in almost every case but also a significant reduction of the costs. Based on these data, national regards are formulated or under construction.

Peri-operative decreased cAMP levels in long-term alcoholic patients.

Long-term alcoholic patients have a five-fold higher risk of post-operative bleeding complications compared with nonalcoholic individuals. Serotonin increases and cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) decrease platelet aggregation. We examined the platelet-rich plasma levels of these substances and agonist-induced platelet aggregation in long-term alcoholic patients before and after surgery. Thirty-three consecutive patients (13 long-term alcoholics and 20 non-alcoholics) scheduled for tumour resections of the upper digestive tract were included in the study. The levels of cAMP were significantly decreased before and after surgery in long-term alcoholic patients, but there were no significant differences in cGMP and serotonin levels in alcoholic compared with non-alcoholic patients. In contrast to previous studies, no significantly altered aggregation responses in long-term alcoholics were found. A possible explanation is decreased inhibition through diminished cAMP levels; cGMP and serotonin do not seem to influence peri-operative haemostasis.

Fibrinolytic capacity in peritoneal fluid after laparoscopic and conventional colorectal resection: data from a randomized controlled trial.

BACKGROUND: A reduced peritoneal fibrinolytic capacity after surgery is currently accepted to be the main cause for postoperative adhesions. The aim of this prospective randomized trial was to determine the fibrinolytic activity in peritoneal fluid after laparoscopic as compared to conventional colorectal resection. METHODS: A randomized controlled trial in parallel with the multicenter trial Lapkon II was conducted. Peritoneal fluid was sampled via drain at 2, 8, and 24 h after elective laparoscopic (n=14; LAP) and conventional (n=16; CON) colorectal resections. Activities and concentrations of tissue plasminogen activator (t-PA), plasminogen activator inhibitor type-1 (PAI-1) and t-PA/PAI complex were determined in all specimen by ELISA kits. RESULTS: There was no difference in age, sex or body mass index between both groups. Postoperatively, t-PA activity decreased in both groups and was lower 2 h after closing the abdomen in the laparoscopic group (p<0.05). PAI-1 activity and concentration increased in both groups. Difference between the groups was measured for PAI-1 concentration after 24 h (p<0.05). There were no differences between the groups regarding t-PA concentrations, PAI-1 activity and t-PA/PAI complex. CONCLUSIONS: After closing the abdominal cavity, postoperative changes in fibrinolytic capacity of peritoneal fluid can be determined in samples collected by a drain. However, there were no major differences in the postoperative course of fibrinolytic capacity in peritoneal fluid after laparoscopic and conventional colorectal resections.

Clopidogrel-related refractory bleeding after coronary artery bypass graft surgery: a rationale for the use of coagulation factor concentrates?

Clopidogrel, an irreversible ADP-receptor antagonist, inhibits platelet aggregation mediated by reduced activation of glycoprotein receptor IIb/IIIa. Clopidogrel in combination with aspirin has been shown to be superior to aspirin alone for treating unstable angina, but clopidogrel recipients have shown increases in blood loss, transfusion requirements, and rate of reoperation after cardiac surgery. We describe a patient who had taken clopidogrel 75 mg daily until the day prior to coronary artery bypass graft surgery. Severe postoperative bleeding developed and was refractory to conventional hemostatic therapy consisting of 19 units of packed red blood cell concentrates, 16 of fresh frozen plasma, 8 of platelet apheresis concentrates plus high-dose treatment with aprotinin (500.000 kallikrein-inhibiting units/h) and administration of 0.3 microg/kg 1-deamino-8-D-arginine vasopressin (DDAVP). Two reoperations were performed, but surgical hemostasis was not achieved, so 100 microg/kg recombinant activated factor VII was applied to generate sufficient thrombin to stop the bleeding. This treatment approach reduced the bleeding. Then, to promote clot formation and firmness, 2 g of fibrinogen and 1250 IU of factor XIII were administered, and the bleeding finally stopped. No further transfusions were required, and the patient was discharged from the hospital on day 10 after the operation. This case suggests that in clopidogrel-related bleeding refractory to conventional hemostatic therapy, hemostasis may be achieved by a stepwise administration of coagulation factor concentrates.

[Adenocarcinoma-associated nonbacterial thrombotic endocarditis as the cause of recurrent strokes]. / Adenokarzinom-assoziierte nichtbakterielle thrombotische Endokarditis als Ursache rezidivierender Schlaganfälle.

We describe a 60-year-old female patient without vascular risk factors diagnosed with cardioembolic ischemic stroke due to an atrial septal aneurysm with a right-to-left shunt. However, further investigation after recurrent strokes revealed a nonbacterial thrombotic endocarditis (NBTE) caused by a metastatic adenocarcinoma. The presented case illustrates the difficulties in establishing the diagnosis of NBTE premortally and points out the importance of repeated echocardiographic evaluations of cardiac valves and serological examination of tumor markers in patients with recurrent strokes of unknown origin.

Prospective randomized trial to determine the influence of laparoscopic and conventional colorectal resection on intravasal fibrinolytic capacity.

BACKGROUND: Although the pneumoperitoneum decreases venous reflux from the lower extremities, the rate of thromboembolic complcations seems to be lower after laparoscopic than after conventional procedures. Therefore, it has been assumed that laparoscopic surgery better preserves the intravasal fibrinolytic capacity. The aim of this study was to determine the influence of the operative technique on intravasal fibrinolytic capacity in colorectal resection. METHODS: Randomized controlled trial conducted in parallel with the multicenter trial LAPKON II comparing the long-term effects of elective laparoscopic (group I) and conventional (group II) resections for colorectal cancer. Blood samples were taken from 30 patients preoperatively, at the beginning and end of surgery as well as 2, 8, and 24 hr postoperatively. Activities and concentrations of tissue plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1), tPA/PAI complex, fibrinogen, and D-dimers were determined in all specimen with ELISA tests. Area under the curve values (AUC) were calculated for all parameters. RESULTS: Patient characteristics and indication for surgery were not different between both groups. Preoperative values of fibrinolytic parameters were similar in both groups. Postoperatively, tPA activity decreased significantly in both groups, but AUC values for tPA and PAI-1 activity (p = 0.23; p = 0.68); concentration of tPA, PAI-1, and tPA/PAI complex (p = 0.52; p = 0.78; p = 0.95); and concentration of fibrinogen and D-dimers (p = 0.67; p = 0.71) did not differ between the groups. CONCLUSIONS: An intravasal fibrinolytic "shutdown" occurs not only after conventional but also after laparoscopic colorectal resection. Both operative techniques had similar effects on postoperative intravasal fibrinolytic capacity. Therefore, the lower incidence of thromboembolic complications after laparoscopic colorectal resections does not seem to be caused by a lesser depression of the intravasal fibrinolytic capacity.

Effect of laparoscopic and conventional colorectal resection on peritoneal fibrinolytic capacity: a prospective randomized clinical trial.

BACKGROUND AND AIMS: Reduced fibrinolytic activity of the peritoneum seems to be the main cause of postoperative adhesions. This prospective randomized trial compared the peritoneal fibrinolytic activity between laparoscopic and conventional colorectal resection. METHODS: Parietal peritoneal biopsy specimens were taken in standardized elective laparoscopic ( n=14) and conventional ( n=16) colorectal resections at the beginning and at the end of surgery. Activities and concentrations of tissue-plasminogen activator (tPA), plasminogen activator (PAI) type 1, and tPA/PAI complex were determined by ELISA kits. RESULTS: There was no difference in age, sex, or body mass index between the two groups. Perioperative tPA activity decreased in both groups without differences between the groups. Concentrations and activities of tPA, PAI-1, and tPA/PAI complex did not differ between the groups at any time. CONCLUSION: Peritoneal concentrations and activities of tPA, PAI-1, and tPA/PAI complex are similar during laparoscopic and conventional colorectal resections. A capnoperitoneum of 12 mmHg over 3 h did not affect the peritoneal fibrinolytic activity

Shwartzman phenomenon in a patient with active systemic lupus erythematosus preceding fatal disseminated intravascular coagulation.

The recurrence of widespread and diverse vascular lesions is a hallmark of systemic lupus erythematosus (SLE). Inflammatory and thrombotic mechanisms almost invariably associated with circulating antiphospholipid antibodies play a role in the pathogenesis of SLE-related vascular disease. Both mechanisms can coexist in the same patient. Vasculitis is most commonly induced by the local deposition of immune complexes. However, some SLE patients have an inflammatory complement-mediated vascular injury in the absence of immune complex deposition. We report on a fatal case of disseminated intravascular coagulation (DIC) in a young woman with active SLE. Hemorrhagic lesions due to localized intravascular coagulation (Shwartzman phenomenon) preceded disseminated intravascular coagulation accompanied by disseminated cardiac necrosis. Immune complex 'independent' and other mechanisms of vascular injury and states of hypercoagulability will be discussed.

Influence of the sampling technique on the measurement of peritoneal fibrinolytic activity.

OBJECTIVE: To establish the influence of the peritoneal sampling technique on the measurement of fibrinolytic capacity. DESIGN: Clinical study. SETTING: University hospital, Germany. SUBJECTS: 40 peritoneal biopsy specimens were taken from 10 patients who were having elective colorectal resections. INTERVENTIONS: Peritoneal biopsy specimens were taken either with a biopsy punch (n = 20) or manually with forceps and scissors (n = 20). MAIN OUTCOME MEASURES: Extent of agreement in fibrinolytic activities between specimens taken with biopsy punch and manually. Major endpoint-peritoneal tissue plasminogen activator (t-PA) activity. Minor endpoints-peritoneal tissue plasminogen activator concentration, and concentration and activity of plasminogen activator inhibitior type 1 (PAT-1). RESULTS: Intra-assay agreement and the extent of agreement between the groups were evaluated by the method of Bland and Altman. Correlation of repeated measurements of t-PA and PAI-1 concentrations and activities from the same sample using the same ELISA kit was high (r = 0.93-0.99, p < 0.01). t-PA activities and concentrations between the groups correlated poorly (r= 0.60 and 0.66, p < 0.01) while no correlation at all was seen for PAI-1 concentration and activity between the groups (r = 0.6 and 0.1, p = 0.2 and 0.9). The mean differences between the groups ranged from -27% to -4.8%. CONCLUSION: The sampling technique considerably affects the measurement of peritoneal fibrinolytic activity.

Practice variation in the treatment of rheumatoid arthritis among German rheumatologists.

OBJECTIVE: To describe practice variation in the treatment of rheumatoid arthritis (RA) among German rheumatologists with regard to drug and non-drug therapy. METHODS: We used data of 7,326 patients with RA registered in a national German rheumatological database in 1998. In the database, every patient with an inflammatory rheumatic disease seen at one of the German Collaborative Arthritis Centres is registered once a year with a standard clinical data form and a patient questionnaire. We compared health care provided by 29 rheumatological outpatient units. For drug and non-drug treatment unit prescription rates, ranges and outliers were calculated. Logistic regression analysis was used for case mix adjustment and for the identification of practice patterns. RESULTS: We observed variation concerning the frequency of use of single disease modifying antirheumatic drugs (DMARD). The median of the prescription rates in the 29 units for methotrexate (MTX) was 55% in 1998 (1st quartile: 51%, 3rd quartile: 63%); sulfasalazine had a median of 15% (quartiles: 10%/19%), antimalarials a median of 8% (quartiles: 5%/21%). Combination DMARD therapy was used in 11% (quartiles: 6%/18%). Prescriptions of low dose steroids (< or = 7.5 mg) had a median of 45% (quartiles: 35%/55%), and nonsteroidal antiinflammatory drugs (NSAID) had a median prescription rate of 58% (quartiles: 50%/70%). High variation was also found concerning active physiotherapy (median: 41%; quartiles 34%/55%) and passive physical measures (median 14%, quartiles 9%/37%). Differences in case mix (age, sex, rheumatoid factor, disease duration, severity, disability) only explained a small proportion of the total variation. When the units were grouped according to the frequency of prescription of DMARD combination therapy, treatment patterns could be identified. Units with higher rates of DMARD combination therapy used more drugs for the prevention and treatment of osteoporosis, more active physiotherapy but fewer NSAID and fewer passive physical therapies. CONCLUSION: Variation in drug and non-drug treatment indicates significant differences in health care provision. Trends in the drug management of RA are adopted differentially by the members of the rheumatology community. The large variability in non-drug therapies may, apart from differences in availability, suggest a lack of agreement on therapeutic effectiveness.

Hirudin versus heparin for anticoagulation in continuous renal replacement therapy.

OBJECTIVE: To compare the efficacy and safety of hirudin and heparin for anticoagulation during continuous renal replacement therapy (CRRT) in critically ill patients. DESIGN: Prospective, randomized controlled pilot study. SETTING: Single centre; interdisciplinary intensive care unit at a university hospital. PATIENTS: Seventeen patients receiving CRRT. INTERVENTIONS: Patients were randomly allocated to two groups. Heparin group (nine patients): continuous administration of 250 IU/h heparin; dose was adjusted in 125 IU/h steps with a targeted activated clotting time (ACT) of 180-210 s. Hirudin group (eight patients): continuous infusion of 10 micrograms/kg/h hirudin, dose was adjusted in 2 micrograms/kg/h steps with a targeted ecarin clotting time (ECT) of 80-100 s. Observation time was 96 h. MEASUREMENTS AND MAIN RESULTS: Measured filter run patency and haemofiltration efficacy did not significantly differ between the two groups. Three bleeding complications were observed in the hirudin group, none in the heparin group (P < 0.01). At the onset of bleeding, which occurred 60 or more hours after the start of therapy, only one patient was still under continuous hirudin administration but levels were either in therapeutic range or below. CONCLUSIONS: Hirudin can be used efficiently for anticoagulation in CRRT. Late bleeding complications may have been caused by possible hirudin accumulation, but this was not evident from hirudin plasma and ECT levels. Since bleeding complications were observed only in the presence of documented coagulation disorders, not only adequate drug monitoring but also the plasmatic and cellular coagulation status of the patient should be taken into consideration for adjusting hirudin dosage.

The beta3-adrenergic receptor Trp64Arg mutation is not associated with coronary artery disease.

There is some evidence that the Trp64Arg polymorphism of the beta3-adrenergic receptor (beta3-AR) is associated with atherogenic risk factors that include weight gain, insulin resistance, and diabetes. The objective of this cross-sectional study was to investigate the relationship between the Trp64Arg polymorphism and coronary artery disease (CAD). A total of 1,000 consecutive patients with angiographically confirmed CAD and 1,000 controls, carefully matched for age and sex, were genotyped for the Trp64Arg polymorphism by polymerase chain restriction and subsequent restriction fragment length polymorphism analysis. Among cases with CAD, 83.3% were wild-type Trp/Trp, 15.8% were heterozygotes, and 0.9% were homozygous Arg/Arg compared with 82.3%, 17.3%, and 0.4%, respectively, among controls (P = .27). The odds ratios for the presence of Trp/Arg and Arg/Arg in cases and controls were 0.90 (95% confidence interval [CI] 0.7 to 1.2; P = .40) and 2.2 (95% CI 0.7 to 7.2; P = .17), respectively. There was no effect modification by gender and atherogenic risk factors, including diabetes, hypercholesterolemia, hypertension, and smoking. Furthermore, there was no evidence of an association with premature disease onset (< 40 years) or extent of disease. In conclusion, the results of this study in a large sample of clinically well-characterized patients indicate that neither the Trp/Arg nor the Arg/Arg genotype represents a major risk factor for angiographically confirmed coronary artery disease.

Arterial thrombosis associated with anticardiolipin and anti-beta2-glycoprotein-I antibodies in patients with non-Hodgkin's lymphoma: a report of two cases.

Autoimmune phenomena in lymphoid malignancies are often observed. However, clinical manifestations such as a secondary antiphospholipid syndrome in the presence of antiphospholipid antibodies are rarely reported. Furthermore, in the few cases of lymphomas so far reported with thrombosis associated with elevated antiphospholipid antibodies, the anti-beta2-glycoprotein-I antibodies have not been studied. We report on two cases of arterial thrombosis occuring in patients with B-cell lymphoma who presented with positive anticardiolipin and anti-beta2-glycoprotein-I antibodies. Our observation suggests that patients with non-Hodgkin's lymphoma and both anticardiolipin and anti-beta2-glycoprotein-I antibodies may be, similar to lupus patients, at considerable risk towards thrombosis, especially towards arterial thrombosis.

Reduced procedural risk for coronary catheter interventions in carriers of the coagulation factor VII-Gln353 gene.

OBJECTIVES: We have focused on the role of coagulation factor VII (FVII) Arg353Gln polymorphism as a risk predictor of complications following percutaneous transluminal coronary angioplasty (PTCA), directional coronary atherectomy (DCA), and stenting. BACKGROUND: The FVII Arg353Gln mutation decreases FVII activity, and presence of the Gln353 allele could be protective against thrombus formation during catheter interventions. METHODS: A total of 666 consecutive patients with coronary artery disease who had undergone PTCA (n = 280), DCA (n = 104), or stenting (n = 282) were followed up for a 30-day composite end point, which included need for target vessel revascularization, myocardial infarction, and death. The Arg353Gln polymorphism of FVII was determined by PCR/RFLP assay. RESULTS: Carriers of the Gln353 allele had significantly lower levels of total FVII activity (FVIIc, -20.7%, p < 0.001) and of activated circulating FVII (FVIIa, -32.7%, p = 0.03) compared with Arg353/Arg353. The composite end point occurred in 43 patients: 4 were heterozygous Arg353/Gln353, and 39 were homozygous Arg353/Arg353. The incidence of the composite end point was 2.5% in carriers of the Gln353 allele and 7.7% in Arg353/Arg353 homozygotes (p = 0.013). This corresponds to a 72% risk reduction in carriers of the Gln353 allele (relative risk: 0.28; 95% confidence interval: 0.09-0.81; p = 0.02). CONCLUSIONS: The Gln353 allele of FVII is associated with substantial risk reduction in adverse events that complicate coronary catheter interventions. With the perspective of active site-blocked activated FVII (FVIIai) as conjunctive medication, the results suggest that the FVII genotype should be taken into due consideration in assessment of FVIIai medication and of its dosage.

Design of a prospective neonatal cohort study of homozygous and double heterozygous factor V Leiden and factor II G20210A.

BACKGROUND: Factor V Leiden (FVL) and Factor II (FII) G20210A represent common risk factors for thromboembolic (TE) events. In children, both venous and arterial TE-events have been associated with the presence of FVL and FII G20210A. In most heterozygous children with TE-events other prothrombotic factors can usually be identified. Case reports of children with homozygous FVL, including 3 patients described here, suggest that this genotype may convey a particulary high risk. However, prospective data about the type and frequency of TE-events in such children are lacking. STUDY DESIGN: We have initiated a prospective neonatal cohort study for the homozygous and double heterozygous genotypes for FVL and FII G20210A. The probands and the heterozygous controls are identified by neonatal screening that involves > 98% of the children born in Berlin and are followed up in a special out-patient clinic to document details of the clinical history, developmental parameters and the occurrence of TE-events. CONCLUSIONS: This study will provide controlled and unbiased information about the clinical significance of the homozygous and double heterozygous genotypes of these mutations.

Influence of heparin and hirudin on endothelial binding of antithrombin in experimental thrombinemia.

OBJECTIVE: During the last decade, experimental and clinical evidence has accumulated that antithrombin (AT) exerts anti-inflammatory effects when given in high doses. Meanwhile, AT substitution has been shown to significantly increase prostacyclin release. However, the link between endothelial AT binding and anti-inflammatory AT effects remains to be established in vivo, although heparin has been shown to counteract anti-inflammatory AT effects. We hypothesized that the administration of heparin in endotoxin-challenged rats would decrease endothelial AT binding and systemic prostacyclin concentrations. DESIGN: Prospective, randomized, controlled experimental in vivo study. SETTING: Research laboratory of a university hospital. ANIMALS: Fifty-six Wistar rats. INTERVENTIONS: Baseline values of coagulation variables were measured in six animals. Forty of 50 Wistar rats in the study groups were given endotoxin (50 mg x kg(-1) iv) and were treated with saline (group LPS), AT (15 units x kg(-1) x hr(-1)) (LPS+AT), AT and heparin (80 IU x kg(-1) x hr(-1)), or AT and hirudin (0.12 mg x kg(-1) x hr(-1)); the other 10 received saline instead of endotoxin and were treated with AT alone. Before endotoxin application, a tracheostomy was performed, and venous and arterial catheters were inserted for blood sampling and infusion. MEASUREMENTS: Intravital endothelial AT binding was studied by using fluorescence isothiocyanate-marked antibodies during intravital microscopy of intestinal submucosal venules. Systemic prostacyclin, thrombin-AT complex, and fibrinogen concentrations were measured after 4 hrs. Intergroup differences were tested by Kruskal-Wallis analysis of variance on ranks. MAIN RESULTS: AT and AT + heparin were equally effective in inhibiting systemic procoagulant turnover as reflected by fibrinogen concentrations. Only the administration of AT + hirudin significantly prevented fibrinogen consumption (p < .05). In contrast with all other treatments, the administration of heparin significantly reduced intravital endothelial AT binding (p < .05). However, prostacyclin concentrations were similarly increased in all endotoxin-challenged study groups irrespective of the anticoagulatory treatment. CONCLUSIONS: There is evidence that heparin in contrast with hirudin prevents AT from being bound to the endothelial cell surface in this experimental model. Under low-dose AT substitution, systemic prostacyclin concentrations do not depend on whether heparin or hirudin is used for thrombin inhibition. These results support the view that heparin may counteract anti-inflammatory AT effects by keeping AT away from its endothelial binding sites; however, the results question the view that decreased endothelial prostacyclin release is solely responsible.