Established anticoagulants in secondary haemostasis

In respect to the actual discussion of new anticoagulants in secondary haemostasis, we will give a short review on established oral anti -coagulation with vitamin K antagonists and parenteral anticoagulation by use of heparin. The different cumarin 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.

Patients with oral anticoagulation

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.

Präoperative Identifikation von Patienten mit (primären) Hämostasestörungen

Wir präsentieren eine große prospektive Untersuchung, in der vor großen elektiven operativen Eingriffen nach Hämostasestörungen ein Screening erfolgte. 5649 erwachsene, nicht selektierte Patienten (2631 Frauen, 3018 Männer) wurden über ein Jahr im Universitätsklinikum Charité untersucht. Ein standardisierter Fragebogen mit 12 Fragen wurde benutzt. Des Weiteren wurden die plasmatischen Routinegerinnungstests (aPTT, PT) mit der Thrombozytenzählung und die In-vitro-Verschlusszeiten (PFA 100: Kollagen- Epinephrin, Kollagen-ADP) gemessen. Wenn die Blutungsanamnese positiv (eine Frage positiv beantwortet) war, wurden folgende Screening-Tests zusätzlich durchgeführt: In-vivo-Blutungszeit (Surgicutt), von-Willebrand- Faktor (VWF : Ag, VWF : Rcof) und weiterführende hämostaseologische Differenzialdiagnostik. Ergebnisse: Die Blutungsanamnese war negativ bei 5021 Patienten (88,8%) und positiv bzw. enthielt einen Hinweis auf Medikamente, die eine Hämostasestörung induzieren können, bei 628 Patienten (11,2%). Hämostasestörungen wurden bei 256 (40,8%) in dieser letzten Patientengruppe gefunden. Die meisten der Patienten mit Hämostasestörungen wurden mit dem PFA-100: C/E (n=250; 97,7%) identifiziert. Die Sensitivität des PFA-100: Kollagen-Epinephrin war am höchsten (90,8%) im Vergleich zu anderen Screeningtests (BT, aPTT, PT, VWF : Ag). Der positive Vorhersagewert (zu Erkennung von Hämostasestörungen) des PFA-100: Kollagen- Epinephrin mit der standardisierten Blutungsanamnese war hoch (82%), aber der negative war mit 93% höher. Schlussfolgerungen: Primäre Hämostasestörungen treten häufiger als plasmatische Hämostasestörungen auf. Ein standardisierter Fragebogen zur Blutungsanamnese und, sofern indiziert, der PFA-100: Kollagen-Epinephrin und/ oder weitere spezifische Tests können zu einer signifikanten Reduktion der Kosten bei einer hohen Identifikationssrate von vorwiegend primären Hämostasestörungen führen. Nationale Empfehlungen sind bereits formuliert.

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.

[Established anticoagulants in secondary haemostasis--Vitamin K antagonists, heparins]

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.

[Patients with oral anticoagulation--bridging anticoagulation in the perioperative phase]

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.

[Preoperative identification of patients with impaired (primary) haemostasis. A practical concept]

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.

[Adenocarcinoma-associated nonbacterial thrombotic endocarditis as the cause of recurrent strokes]

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.

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 3g/kg 1-deamino-8-D-arginine vasopressin (DDAVP). Two reoperations were performed, but surgical hemostasis was not achieved, so 100 3g/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.

Therapie der tiefen Beinvenenthrombose mit Dalteparin

Ziel: Untersuchung des Laborwertverlaufes und des individuellen Wirksamkeitsnachweises bei ambulanter Therapie tiefer Beinvenenthrombosen mit Dalteparin. Patienten, Material, Methoden: Wir behandelten ambulant 10 Patienten mit einer frischen TVT täglich mit 2 × 100 IE Dalteparin (Fragmin®)/kg Körpergewicht abweichend von den Leitlinien für die Dauer von 14 Tagen durch subkutane Selbstinjektion. Ergebnisse: Die HepZeit (Anti-FXa-Aktivität) lag bei 9/10 Patienten innerhalb und bei einem Patienten unterhalb des therapeutischen Bereichs. Die D-Dimere bildeten sich unter der Antikoagulationsbehandlung vollständig zurück. Die Thrombusgröße änderte sich im Beobachtungszeitraum nicht. Schlussfolgerung: Die ambulante Therapie ist eine sichere, wirksame und ökonomisch überlegene Alternative zur stationären Therapie. Die D-Dimere erwiesen sich als aussagefähiger Verlaufsparameter.

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.

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.

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

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.

[Hereditary thrombophilia with ischemiC stroke and sinus thrombosis. Diagnosis, therapy and meta-analysis]

Hereditary thrombophilias are a heterogenous group of genetic coagulation disorders which, particularly in combination with acquired prothrombotic factors, induce a predisposition to thrombosis. After characterization of frequent thrombophilic syndromes like factor V-Leiden or the prothrombin 20210GA mutation, a number of case-control studies screened for the prevalence of these mutations in ischemic stroke and cerebral venous thrombosis (CVT). Our meta-analysis shows that factor V-Leiden and prothrombin are frequent and significantly associated with CVT (16.4% vs. 4.9% or 4.3, P < 0.001, and 12.1% vs. 1.9% or 5.8, P < 0.001). In ischemic stroke, only factor V-Leiden and not prothrombin is a weak but significant risk factor (5.9% vs. 2.6% or 1.6, P < 0.001, and 4.1% vs. 3.3% or 1.4, P = 0.1). The C677T homozygous point mutation in the MTHFR, a homocysteine-degrading enzyme, was also associated with arterial stroke (16% vs. 15% or 1.5, P < 0.001). For CVT, sufficient data are lacking. We therefore recommend screening for thrombophilia in CVT. In ischemic stroke, atrial premature complex (APC) resistance should be considered. As long as controlled studies are lacking, individual anticoagulant therapy must take hereditary and precipitating factors into account to assess potential thrombotic risk.

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.

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.

Evaluation of erythropoietic activity on the basis of the red cell and reticulocyte distribution widths during epoetin beta therapy in patients undergoing cardiac surgery

The changes in the red cell and reticulocyte distribution widths during preoperative treatment with recombinant human erythropoietin (rhEPO) were evaluated in a double-blind, placebo-controlled trial in cardiac surgery patients. The increases in the reticulocyte count, in the hemoglobin and in all distribution widths are the expression of the marked preoperative stimulation of erythropoiesis in the patients treated with rhEPO. Only placebo patients with a hemoglobin < or = 7.5 mmol/l or a transferrin > 4.0 g/l at baseline showed an increase in the red cell distribution width or in the reticulocyte hemoglobin distribution width on oral iron therapy alone. While the reticulocyte count and the distribution widths of red cells in the rhEPO patients decreased postoperatively, only the increases in the distribution widths of reticulocytes after the second postoperative day indicate that stimulation oferythropoiesis had taken place. In patients with a low hemoglobin or a high transferrin the rhEPO therapy should be preceded by iron therapy in order to raise the hemoglobin level and reduce the cost of treatment.

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.

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.

Further evidence for oxidant-induced vascular endothelial growth factor up-regulation in the bronchoalveolar lavage fluid of lung cancer patients undergoing radio-chemotherapy

BACKGROUND

Vascular endothelial growth factor (VEGF) is a potent inducer of physiological and neoplastic blood vessel growth. Moreover, in vitro studies have demonstrated that VEGF can be up-regulated by conditions associated with the generation of free radicals and reactive oxygen species. In a previous study we reported on strongly increased VEGF concentrations in the bronchoalveolar lavage fluid (BALF) of patients with lung cancer under therapy. In this study we aimed to reveal whether this increase was due to the therapy-associated intrapulmonary oxidative burden.

PATIENTS AND METHODS

A total of 103 BALF samples from 94 patients with lung cancer (82 patients with non-small-cell lung cancer, 12 patients with small-cell lung cancer) were studied at different times before, during or after cancer treatment. VEGF levels in the lavage fluid and ratios of oxidised methionine in proteins of epithelial lining fluid (ELF) were determined.

RESULTS

As reported previously, strongly increased VEGF levels in the ELF were observed in patients undergoing chemotherapy when radiotherapy had been administered before. Increased levels of oxidised methionine indicated that these patients suffered from severe pulmonary oxidative stress that was significantly less in patients undergoing only chemotherapy. Similarly, VEGF concentrations in the ELF were significantly elevated in cancer patients at the time of diagnosis, but the oxidised methionine levels did not reveal significant oxidant/antioxidant imbalances in these patients.

CONCLUSION

Systemic chemotherapy is associated with oxidative stress in vivo, which is more pronounced if patients are additionally treated with radiation. VEGF levels in the ELF are increased by this condition as well as by the activity of the tumour itself.

Elevated serum leptin in patients with coronary artery disease: no association with the Trp64Arg polymorphism of the beta3-adrenergic receptor

BACKGROUND

Serum leptin is associated with the occurrence of cardiovascular risk factors but it is unknown whether leptin is also associated with cardiovascular disease. Another open question is whether the Trp64Arg polymorphism of the beta3-adrenergic receptor (beta3-AR) is a determinant of circulating leptin.

OBJECTIVES

We measured serum leptin concentrations in a large group of patients with angiographically assessed coronary artery disease (CAD) and investigated the relationship between the Trp64Arg polymorphism of the beta3-adrenergic receptor (AR) and serum leptin.

PATIENTS AND METHODS

Leptin was measured in the fasting state in 1000 consecutive patients with angiographically confirmed CAD by radioimmunoassay. The codon 64 T/C polymorphism of the beta3-AR gene was analysed by the polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) technique. Controls were 1000 age-, gender- and weight-matched subjects without clinical signs of CAD.

RESULTS

Serum leptin concentrations were significantly higher in patients with CAD than in those without CAD (median: 6.8 vs 6.1 ng/ml, P < 0.001). In a multiple regression analysis leptin was found to be a determinant of CAD (P = 0.005) along with established risk factors. No differences in serum leptin were observed between wild-type and heterozygous carriers of the Trp64Arg mutation of the beta3-AR gene, whereas the small group of homozygous carriers had higher leptin due to their higher BMI. In a multiple linear regression analysis, body mass index, gender and fasting insulin were the main significant determinants of serum leptin, whereas the beta3-AR polymorphism had no effect.

CONCLUSIONS

Patients with coronary artery disease exhibit higher serum leptin concentrations than age- and gender-matched controls of comparable BMI, indicating that leptin could contribute to the development of cardiovascular disease, possibly via activation of the sympathetic nervous system. The Trp64Arg variant of the beta3-adrenoceptor did not influence serum leptin.

Bleeding after intermittent or continuous r-hirudin during CVVH

OBJECTIVE

To demonstrate bleeding complications encountered in patients after cardiac surgery on continuous venovenous haemofiltration (CVVH) treated with continuous versus intermittent r-hirudin for heparin-induced thrombocytopenia (HIT) type II.

DESIGN

Case description.

SETTING

Cardiothoracic intensive care unit at a university hospital.

PATIENTS

5 consecutive patients with proven HIT type II on CVVH after major cardiac surgery.

INTERVENTIONS

Recombinant hirudin (r-hirudin) was given continuously at a dose of 0.01 mg/kg per h in three patients or in repeated bolus administration of 0.05 mg/kg in two patients.

MEASUREMENTS AND RESULTS

Since the ecarin clotting time assay was not available at that time to monitor hirudin effects on coagulation, the activated partial thromboplastin time (normal range 26-38 s, target range 50-60 s) was used. The continuously treated patients suffered from major bleeding complications. Therefore, the regimen was changed to repeated bolus administration, reducing the incidence of bleeding complications probably due to a threefold diminished cumulative hirudin dose per day in comparison to continuous administration.

CONCLUSIONS

If ecarin clotting time, the most suitable monitor for hirudin activation, is not available, we would prefer to give r-hirudin in repeated boluses to avoid major bleeding complications in cardiac surgery patients on CVVH.

Intravenous administration of recombinant adenoviruses causes thrombocytopenia, anemia and erythroblastosis in rabbits

BACKGROUND

Recombinant adenoviruses are highly efficient gene transfer vehicles but their administration to mammals is accompanied by a strong inflammatory response. The present study reports additional side effects observed during adenoviral gene transfer studies in rabbits.

METHODS

Hematological and serological parameters, the course of viremia and the organ distribution were analyzed after in vivo administration of E1-deleted adenoviruses in rabbits.

RESULTS

The systemic administration of a therapeutic dose of 5 x 10(11) infectious particles/kg (infusion time 20 min) led to an average reduction of 80-90% in the platelet count within 48 h. Full recovery took 10-14 days. Virus administration induced a strong but transient erythroblastosis (peaking 24 h after administration) which settled 48 h later. Normochromic anemia occurred over the next 10 days with hemoglobin levels dropping by about 40% to reach the lowest level 10 days after administration and taking two months for full recovery. Dose-dependent thrombocytopenia was also found in mice, but neither erythroblastosis nor anemia was observed (in equivalent doses). The hematological findings did not improve after local injection via the portal vein. Local and systemic administration led to a comparable course of viremia. Only minor differences were found in the biodistribution of viruses between local and systemic administration. Large amounts of viral DNA and transgene expression were found in the lungs, the kidneys and the ovaries, even after local administration via the portal vein.

CONCLUSIONS

Local intravenous injection via the portal vein does not prevent systemic spread of viral vectors and the occurrence of vector-related side effects. The hematological changes observed in rabbits suggest the need for careful monitoring of hematological and rheological parameters in clinical trials.

Increased levels of vascular endothelial growth factor in bronchoalveolar lavage of patients with bronchial carcinoma effect of tumour activity and oxidative stress due to radio-chemotherapy?

BACKGROUND

Vascular endothelial growth factor (VEGF) plays a crucial role in physiological and neoplastic angiogenesis. Moreover, VEGF has been found to be upregulated by conditions associated with the generation of free radicals and reactive oxygen intermediates. In patients with cancer, studies to evaluate VEGF as a measure of tumour activity were carried out. We tested the hypothesis that VEGF is additionally affected by oxidative stress due to anticancer therapy. Moreover, the suitability of epidermal growth factor (EGF) to estimate tumour activity was studied.

PATIENTS AND METHODS

60 patients with non-small cell lung cancer (NSCLC) covering different therapy progress and modalities underwent bronchoalveolar lavage. VEGF-, EGF-, albumin- and total protein-concentrations in bronchoalveolar lavage fluid (BALF) and VEGF-levels in blood plasma were studied.

RESULTS

BALF VEGF-levels were increased in patients with advanced NSCLC before and in anticancer therapy. In patients who had received radiotherapy to the lung prior to chemotherapy, VEGF concentrations were noticeably higher than under sole chemotherapy. Pulmonary endothelial hyperpermeability was found in patients with recently diagnosed tumours and patients undergoing anti-cancer therapy. Evaluation of EGF-levels in BALF revealed no significant influence of tumour activity or cancer therapy on this parameter.

CONCLUSION

BALF-levels of VEGF are affected by tumour activity and oxidative stress due to anticancer therapy.

Fibrinogen breakdown, long-lasting systemic fibrinolysis, and procoagulant activation during alteplase double-bolus regimen in acute myocardial infarction

Recent clinical studies comparing accelerated versus bolus administration of alteplase tissue plasminogen activator (t-PA) suggest similar thrombolytic efficacy, but reveal higher bleeding complications among older patients during the double-bolus regimen. The objective of the present study was to characterize the hemostatic profile of t-PA administered as double-bolus doses of 50 mg, at intervals of 30 minutes. Among 50 patients with acute myocardial infarction treated by double-bolus t-PA thrombolysis, coagulation and fibrinolysis parameters, as well as t-PA levels, were monitored. Monitored t-PA levels peaked at 5 and 35 minutes and were detectable within the therapeutic range even after 90 minutes. Marked systemic fibrinolytic activation was indicated by 75% depletion of both plasminogen and fibrinogen, as well as by 19-fold and 300-fold increases of fibrin degradation and fibrinogen degradation products. Plasminogen-activator inhibitor activity was completely suppressed. Pronounced procoagulant activation was reflected by a 3.4-fold increase of both factor XIIa and prothrombin fragment 1+2, and by a threefold increase of thrombin-antithrombin complex. Independent of t-PA weight dosage, fibrinolytic activation was more pronounced among older patients (> or = 63 years). We conclude that t-PA after bolus administration has a long half-life. Double-bolus regimen leads to a long-lasting systemic fibrinolytic state, which is even more remarkable among older patients--a fact that may explain the higher bleeding complications reported for this age group.

Increased rate of factor V Leiden mutation in patients with cerebral venous thrombosis

We investigated the association between cerebral venous thrombosis and hereditary resistance to activated protein C (APC) in 12 consecutive German patients with non-fatal cerebral venous thrombosis and in 187 controls without a history of thrombotic disorder. Three patients (25%) had a mutation in the factor V Leiden gene against only one subject in the control group. This difference was significant (P < 0.05), with an odds ratio of 11.7 (1.5-87; 95% confidence interval). Two patients carrying the mutation had additional common risk factors for thrombosis, and 2 had a positive family history of thromboembolism. We conclude that inherited APC resistance by a mutation in factor V Leiden is an important risk factor in non-fatal cerebral venous thrombosis. We recommend testing for APC resistance and, if abnormal for factor V Leiden mutation in patients with cerebral venous thrombosis.

Paediatric thrombo-embolism: the influence of non-genetic factors and the role of activated protein C resistance and protein C deficiency

In many children, the pathogenesis of thrombo-embolism remains unexplained. This study examines the role of non-genetic risk factors in 37 children with venous or arterial thrombosis. Included were 17 patients with portal vein thrombosis following umbilical vein catheterisation, 6 with portal vein thrombosis and an uneventful neonatal period, 4 with deep vein thrombosis, 4 with renal vein thrombosis after kidney transplantation, 1 haemodialysis patient with thromboses of arteriovenous shunts, and 5 with arterial thromboses at various sites. In 25 of these 37 patients (68%) exogenic risk factors and particularly vascular manipulations (24/37) were related to the thrombotic event. Resistance to activated protein C was identified in 5 patients and protein C deficiency in 2 (7/37; 19%). This prevalence was significantly higher than that of the control group (14/243; 5.8%; chi 2, P < 0.008).

CONCLUSION

Our data show that non-genetic and particular iatrogenic risk factors can often be identified in children with thrombosis, but activated protein C resistance and protein C deficiency are significant genetic risk factors in this age group.

The effect of preoperative recombinant human erythropoietin therapy on platelets and hemostasis in patients undergoing cardiac surgery

In a double-blind, randomized, placebo-controlled trial we evaluated the effects of the administration of recombinant human erythropoietin (5 x 500 U epoetin beta/kg body weight intravenously over a 14-day period before surgery) in patients undergoing cardiac surgery and in whom autologous blood donation was contraindicated on platelet count, platelet distribution width, mean platelet volume (MPV), and certain hemostaseologic parameters. All patients received 3 x 70 IU heparin/kg per day s.c. from 2 days before operation. No thromboembolic events were associated with epoetin beta therapy during the study period. The thrombocytic parameters showed no significant changes in the placebo group before surgery, and the preoperative hematocrit increase in the epoetin beta group was accompanied with an MPV drop (in contrast to the known MPV rise in recombinant human erythropoietin-treated patients with uremia) by a mean of 0.85 fl and a platelet distribution width rise by 3.3% without a significant change in platelet count. In the epoetin beta group the coagulation time (K) of thromboelastogram (TEG) showed an increase from 4.8 to 5.4 minutes by the seventh study day and after the initiation of heparin therapy a further increase to 7.5 minutes. The higher preoperative K increase in the epoetin beta group may partly be a result of the MPV reduction, because smaller platelets are less reactive, a fact underlined by the negative correlation between the preoperative changes of MPV and reaction time of TEG (r = -0.58, p = 0.0148). In contrast, in the placebo group the K of TEG increased only after the start of heparin therapy (from 5.1 to 6.4 minutes). The significant drop in MPV in the epoetin beta group and the higher increase in K of TEG and the other investigated hemostatic parameters do not suggest any increased thromboembolic risk during the preoperative epoetin beta therapy. Therefore this treatment seems to be a safe way for increasing mean hematocrit by approximately 0.06 within the normal range and reducing the homologous blood requirement in patients undergoing elective cardiac surgery.

Age-dependent regeneration of plasma proteins after donor plasmapheresis

To analyze age-dependent effects of a plasma donation on the regeneration of plasma proteins two groups of first time plasma donors were selected (less than 25 years, greater than 50 years). By measurements of hematological and biochemical parameter, immunoglobulins, procoagulators and inhibitors of coagulation before and after a plasma donation the kinetic of regeneration until three weeks was followed up. It can be concluded that a single plasma donation affects the generation in younger and older donors in a different way. Procoagulators and inhibitors show the same behavior, except the donation related elevation of fibrinogen in young donors. Especially the retarded regeneration of cholinesterase and immunoglobulins in the male young group should be taken into consideration for frequent plasma donations and autologous preoperative plasma donations.

False-negative prenatal exclusion of Wiskott-Aldrich syndrome by measurement of fetal platelet count and size

The study of the fetal platelet count and size can, according to the literature, be used for the prenatal diagnosis of the Wiskott-Aldrich syndrome (WAS). So far, no affected fetuses have been identified by this method. All pregnancies in which this method had been applied to resulted, as correctly predicted, in the birth of normal children. Here we report on a familial case of WAS where the haematological parameters failed to reveal the affected second child. Hence we assume that the platelet count and size of platelets remain normal in fetuses with WAS to the gestational age of 22 weeks and cannot be used for prenatal diagnosis.

[Percutaneous removal of kidney calculi and extracorporeal shockwave lithotripsy in patients with hemorrhagic diatheses]

Hemorrhage is the main complication of percutaneous kidney stone removal. Shock-wave lithotripsy also may causes bleeding complications. It seems that both procedures are contraindicated on patients with coagulation disorders. On the base of two cases the specification of treatment by patients with hemorrhagic diatheses is demonstrated. Modern treatment modalities of urinary stone disease are also applicable to those patients, when attention is paid to some conditions and attentive measures are taken.

Electrorotation--a new method for investigating membrane events during thrombocyte activation. Influence of drugs and osmotic pressure

The measurement of the spin of cells in rotating high-frequency electric fields ('electrorotation') make possible the investigation of dielectric membrane properties of single cells. This method was applied to membrane permeability changes accompanying thrombocyte activation and compared with light-scattering data. Describing the dielectric behavior of platelets by a single-shell model and assuming a sufficiently low membrane conductivity of 1 X 10(-7) S/m we found for nonactivated platelets a membrane capacity of 5.5 mF/m2 and the conductivity of the internal medium was estimated to be 0.12 S/m. Upon activation, the electrorotation decreased continuously, with half-times in the range of few minutes. This could be explained assuming a 500-fold increase in membrane conductivity. The application of both local anesthetics and virostatics inhibited the decrease of electrorotation, as did hypertonic osmotic pressure. In all cases this was accompanied by inhibition of platelet aggregation. Hypotonic solutions induced self-aggregation and spontaneous loss of electrorotation. It was concluded that the increase in permeability of the granule membrane is a crucial step in the release reaction and that the electrorotation method is able to detect the incorporation of the granule membranes into the plasma membrane during activation. The advantage of this electrorotation method is that it enables measurements on a single-cell level, thus avoiding interactions between platelets.