French clinical practice guidelines on the management of patients on vitamin K antagonists in at-risk situations (overdose, risk of bleeding, and active bleeding)

[Proper use of apixaban: an outline for clinical practice]

Apixaban is a direct inhibitor of coagulation factor Xa. Superior efficacy over aspirin and antivitamin K has been shown in the prevention of stroke and systemic embolism during non-valvular atrial fibrillation with a more favorable safety profile, even though the risk of hemorrhage cannot be ignored, considering its mechanism of action. The recommended dose is 5mg twice daily which can be reduced to 2.5mg depending on the individual risk. Apixaban is also indicated for the treatment of venous thromboembolism but reimbursement has not yet been accepted in France for this indication. As with all direct oral anticoagulants, no routine biological monitoring is required, nevertheless their use may have an impact on all coagulation tests, eventually hampering interpretation. In particular clinical circumstances where a measure of anticoagulant efficacy is deemed necessary, specific assay of anti-Xa activity is appropriate, the result being expressed as concentration of the anticoagulant used. It is therefore necessary to state the name of the medicine for which the assay is requested. With these new anticoagulants, management of hemorrhagic events can be more difficult due to the lack of a specific antidote. Pro-hemostatic substances have exhibited efficacy in animal models but results are still insufficiently documented in clinical practice. Local or locoregional hemostasis measurements, when possible, are an essential factor in the treatment of hemorrhagic events.

Emergency admissions for major haemorrhage associated with antithrombotics: a cohort study

INTRODUCTION

to describe antithrombotic-related major haemorrhage, therapeutic management and outcomes in patients admitted to an emergency department of a teaching hospital.

MATERIAL AND METHOD

This prospective cohort included patients older than 16years with antithrombotic-related major haemorrhage identified by monthly diagnostic codes computerised requests. Major haemorrhage was defined by at least one the following criteria: unstable hemodynamic, haemorrhagic shock, uncontrollable bleeding, need for transfusion or haemostatic procedure, or a life threatening location.

RESULTS

between January 1, 2011 and December 31, 2012, 913 patients met the inclusion criteria (1.2 patients per day), median age 82. Oral anticoagulants alone or in combination were used by 429 patients, antiplatelet agents (alone or dual therapy) by 420 patients, and parenteral anticoagulants by 64 patients. Major haemorrhages were: gastrointestinal bleeding (37.5%), intracranial haemorrhage (34.4%), muscular hematoma (9.4%), external haemorrhage (16.9%) and internal haemorrhage (1.9%). At 1month, 179 patients (19.8%) died, mostly patients with intracranial haemorrhage (64.2%). Prognostic factors for death were age and Glasgow coma scale at admission for intracranial haemorrhage, age and mean arterial pressure at admission for other major haemorrhages. Oral anticoagulant therapy was a predictor for death in intracranial haemorrhages. Reversal therapy was initiated in only 50.5% of patients with vitamin K antagonists, without effect on the mortality rate.

CONCLUSION

This study shows the magnitude and the severity of antithrombotic-related major haemorrhage. The high mortality rate supports careful awareness in individual risk benefit assessment, especially for elderly.

Use of blood products in patients with anticoagulant-related major bleeding: an analysis of inhospital outcomes

PURPOSE

The impact of correcting elevated International Normalized Ratio (INR) values on inhospital mortality in patients with warfarin-associated major bleeding is presented.

METHODS

Using patient information from the database of a large U.S. health system, a retrospective analysis was conducted to (1) evaluate inpatient practice patterns in correcting INR elevations among patients hospitalized with warfarin-related intracranial hemorrhage (ICH) or non-ICH bleeding and (2) test the hypothesis that achieving INR correction, defined as an INR of ≤1.5, at any point during the hospital stay is correlated with lower inhospital mortality. Cox proportional hazards models were constructed to assess predictors of inhospital death.

RESULTS

Among the 354 patients who met the study selection criteria, INR correction was achieved in 87.9% overall (92.5% and 85.5% of patients with ICH and non-ICH bleeds, respectively). Patients whose elevated INR values were corrected had significantly lower inhospital death rates than those with uncorrected elevations: 15.3% versus 55.6% (p = 0.010) among patients with ICH and 2.0% versus 11.8% (p = 0.017) among those with non-ICH bleeds. After adjusting for baseline demographics and comorbidities, the correlation between failure to correct INR elevations and increased mortality risk was significant only for patients with ICH (hazard ratio, 8.04; 95% confidence interval, 2.07-31.18; p = 0.003).

CONCLUSION

Results of this study indicated that correction of elevated INR values was associated with a lower likelihood of inhospital death among warfarin-treated patients hospitalized for ICH or non-ICH major bleeding.

New oral anticoagulant-induced bleeding: clinical presentation and management

Bleeding is a significant complication of anticoagulant therapy. With the emergence of new oral anticoagulants (NOACs; ie, direct factor IIa or Xa inhibitors), this risk is further compounded by the lack of validated reversal strategies for these agents. Emerging postmarketing evidence suggests that the bleeding risks are in line with results observed in head-to-head clinical trials of NOACs versus traditional anticoagulants. Several guidelines have recommended the use of hemostatic agents for NOAC reversal in patients with life-threatening bleeding. Ultimately, adequately powered studies will be crucial for full assessment of the effectiveness and safety of any proposed reversal strategies.

Guideline-concordant administration of prothrombin complex concentrate and vitamin K is associated with decreased mortality in patients with severe bleeding under vitamin K antagonist treatment (EPAHK study)

Introduction

In vitamin K antagonist (VKA)-treated patients with severe hemorrhage, guidelines recommend prompt VKA reversal with prothrombin complex concentrate (PCC) and vitamin K. The aim of this observational cohort study was to evaluate the impact of guideline concordant administration of PCC and vitamin K on seven-day mortality.

Methods

Data from consecutive patients treated with PCC were prospectively collected in 44 emergency departments. Type of hemorrhage, coagulation parameters, type of treatment and seven-day mortality mortality were recorded. Guideline-concordant administration of PCC and vitamin K (GC-PCC-K) were defined by at least 20 IU/kg factor IX equivalent PCC and at least 5 mg of vitamin K performed within a predefined time frame of eight hours after admission. Multivariate analysis was used to assess the effect of appropriate reversal on seven-day mortality in all patients and in those with intracranial hemorrhage (ICH).

Results

Data from 822 VKA-treated patients with severe hemorrhage were collected over 14 months. Bleeding was gastrointestinal (32%), intracranial (32%), muscular (13%), and “other” (23%). In the whole cohort, seven-day mortality was 13% and 33% in patients with ICH. GC-PCC-K was performed in 38% of all patients and 44% of ICH patients. Multivariate analysis showed a two-fold decrease in seven-day mortality in patients with GC-PCC-K (odds ratio (OR) = 2.15 (1.20 to 3.88); P = 0.011); this mortality reduction was also observed when only ICH was considered (OR = 3.23 (1.53 to 6.79); P = 0.002).

Conclusions

Guideline-concordant VKA reversal with PCC and vitamin K within eight hours after admission was associated with a significant decrease in seven-day mortality.

Compliance with guidelines for the perioperative management of vitamin K antagonists

INTRODUCTION

Perioperative vitamin K antagonist management is an issue of concern in many countries. The availability of best practice guidelines meets health professionals' needs, but compliance is uncertain and should be assessed.

MATERIALS AND METHODS

Our aim was to assess practitioner compliance with the guidelines on perioperative VKA management issued by the French National Authority for Health through a national register set up in partnership with the French College of Anaesthetists and Intensivists. Seven sections of data entry were focused on perioperative management of VKAs for elective or emergency procedures. High-risk patients were identified. Compliance with guidelines was calculated per item

RESULTS

932 charts were completed between October 2009 and December 2010. VKA therapy was interrupted in 74% (622/837) of elective procedures and bridged in 69% cases (428/622) mainly with LMWH. According to guidelines, bridging was strongly recommended in 39% high-risk patients (175/394) but 13% of these (23/175) received no bridging. Bridging was overused in 60% of low risk patients (242/406). Other compliance rates were as follows: (i) administration of therapeutic enoxaparin doses (=200IU/kg/day): only 18% of high-risk patients (18/98), (ii) INR measurement on evening prior to the procedure 65% (525/803), (iii) concomitant prothrombin complex concentrate and vitamin K administration in emergency surgery 24% (21/87), (iv) postoperative therapeutic enoxaparin doses: only 20% despite widespread prescription. The incidence rate of bleeding and thrombotic events was 7.1% and 0.96% respectively.

CONCLUSIONS

These poor compliance rates with guidelines suggest that the knowledge-to-action transfer plan was inadequate and that further interventions are required.

Reversing the new oral anticoagulants with prothrombin complex concentrates (PCCs): what is the evidence?

Newer oral anticoagulants offer several advantages over traditional agents (e.g. warfarin), but they are still associated with a bleeding risk and currently there is no validated reversal treatment for them. While there is little support for the use of fresh frozen plasma, and limited data available on the effects of activated recombinant factor VII, preclinical data suggest that prothrombin complex concentrates (PCCs) may have potential in this setting. PCCs are currently used to successfully reverse warfarin-induced anticoagulation; however, clinical evidence for their use with new oral anticoagulants is lacking, with most of the available data coming from preclinical animal studies. Furthermore, there appears to be variation in the ability of different PCCs to reverse the coagulopathy induced by the new anticoagulants, and a lack of correlation between the reversal of laboratory test results and the reversal of anticoagulant-induced bleeding. Although there have been encouraging results, care must be taken in generalising findings from animal models and nonbleeding human subjects to the situation in bleeding patients. Ultimately, more evidence supporting anticoagulation reversal for new anticoagulants is needed, particularly regarding the treatment of bleeding in human patients in a clinical setting. According to the current evidence, use of PCCs may be considered a reasonable approach in dire clinical situations; however, a consensus has not yet been reached regarding PCC use or dosing, due to lack of clinical data.

Rapid reversal of warfarin-associated hemorrhage in the emergency department by prothrombin complex concentrates

Life-threatening warfarin-associated hemorrhage is common, with a high mortality. In the United States, the most commonly used therapies--fresh frozen plasma and vitamin K--are slow and unpredictable and can result in volume overload. Outside of the United States, prothrombin complex concentrates are often used instead; these pooled plasma products reverse warfarin anticoagulation in minutes rather than hours. This article reviews the literature relating to warfarin reversal with fresh frozen plasma, prothrombin complex concentrates, and recombinant factor VIIa and provides elements for a management protocol based on this literature.

Management of major bleeding complications and emergency surgery in patients on long-term treatment with direct oral anticoagulants, thrombin or factor-Xa inhibitors: proposals of the working group on perioperative haemostasis (GIHP) - March 2013

Direct new oral anticoagulants (NOACs) - inhibitors of thrombin or factor Xa - are intended to be used largely in the treatment of venous thromboembolic disease or the prevention of systematic embolism in atrial fibrillation, instead of vitamin K antagonists. Like any anticoagulant treatment, they are associated with spontaneous or provoked haemorrhagic risk. Furthermore, a significant proportion of treated patients are likely to be exposed to emergency surgery or invasive procedures. Given the absence of a specific antidote, the action to be taken in these situations must be defined. The lack of data means that it is only possible to issue proposals rather than recommendations, which will evolve according to accumulated experience. The proposals presented here apply to dabigatran (Pradaxa(®)) and rivaroxaban (Xarelto(®)); data for apixaban and edoxaban are still scarce. For urgent surgery with haemorrhagic risk, the drug plasma concentration should be less or equal to 30ng/mL for dabigatran and rivaroxaban should enable surgery associated with a high bleeding risk. Beyond that, if possible, the intervention should be postponed by monitoring the drug concentration. The course to follow is then defined according to the NOAC and its concentration. If the anticoagulant dosage is not immediately available, worse propositions, based on the usual tests (prothrombin time and activated partial thromboplastin time), are presented. However, these tests do not really assess drug concentration or the risk of bleeding that depends on it. In case of serious bleeding in a critical organ, the effect of anticoagulant therapy should be reduced using a non-specific procoagulant drug as a first-line approach: activated prothrombin complex concentrate (aPCC) (FEIBA(®) 30-50U/kg) or non-activated PCC (50U/kg). In addition, for any other type of severe haemorrhage, the administration of a procoagulant drug, which is potentially thrombogenic in these patients, is discussed according to the NOAC concentration and the possibilities of mechanical haemostasis.

Reversal of Vitamin K Antagonist (VKA) effect in patients with severe bleeding: a French multicenter observational study (Optiplex) assessing the use of Prothrombin Complex Concentrate (PCC) in current clinical practice

Introduction

Prothrombin Complex Concentrate (PCC) is a key treatment in the management of bleeding related to Vitamin K antagonists (VKA). This study aimed to evaluate prospectively PCC use in patients with VKA-related bleeding in view of the French guidelines published in 2008.

Methods

All consecutive patients with VKA-related bleeding treated with a 4-factor PCC (Octaplex^®) were selected in 33 French hospitals. Collected data included demographics, site and severity of bleeding, modalities of PCC administration, International Normalized Ratio (INR) values before and after PCC administration, outcomes and survival rate 15 days after infusion.

Results

Of 825 patients who received PCC between August 2008 and December 2010, 646 had severe bleeding. The main haemorrhage sites were intracranial (43.7%) and abdominal (24.3%). Mean INR before PCC was 4.4 ± 1.9; INR was unavailable in 12.5% of patients. The proportions of patients who received a PCC dose according to guidelines were 15.8% in patients with initial INR 2-2.5, 41.5% in patients with INR 2.5-3, 40.8% in patients with INR 3-3.5, 26.9% in patients with INR > 3.5, and 63.5% of patients with unknown INR. Vitamin K was administered in 84.7% of patients. The infused dose of PCC did not vary with initial INR; the mean dose was 25.3 ± 9.8 IU/Kg. Rates of controlled bleeding and target INR achievement were similar, regardless of whether or not patients were receiving PCC doses as per the guidelines. No differences in INR after PCC treatment were observed, regardless of whether or not vitamin K was administered. INR was first monitored after a mean time frame of 4.5 ± 5.6 hours post PCC. The overall survival rate at 15 days after PCC infusion was 75.4% (65.1% in patients with intracranial haemorrhage). A better prognosis was observed in patients reaching the target INR.

Conclusions

Severe bleeding related to VKA needs to be better managed, particularly regarding the PCC infused dose, INR monitoring and administration of vitamin K. A dose of 25 IU/kg PCC appears to be efficacious in achieving a target INR of 1.5. Further studies are required to assess whether adjusting PCC dose and/or better management of INR would improve outcomes.

A reappraisal of plasma, prothrombin complex concentrates, and recombinant factor VIIa in patient blood management

Plasma therapy and plasma products such as prothrombin complex concentrates (PCCs), and recombinant activated factor VII (rFVIIa) are used in the setting of massive or refractory hemorrhage. Their roles have evolved because of newly emerging options, variable availability, and heterogeneity in guidelines. These factors can be attributable to lack of evidence-based support for a defined role for plasma therapy, variability in coagulation factor content among PCCs, and uncertainty regarding safety and efficacy of rFVIIa in these settings. This review summarizes these issues and provides insight regarding use of these options in management of refractory or massive bleeding.

New direct oral anticoagulants--current therapeutic options and treatment recommendations for bleeding complications

To date, clinical studies show that the incidence of spontaneous bleeding with new direct oral anticoagulants (DOAs) is comparable to that of established anticoagulants. However, unlike vitamin K antagonists, there are currently no clinically available antidotes or approved reversal agents for new DOAs. Restoring normal coagulation is important in many cases, such as emergency surgeries, serious bleedings, or anticoagulant overdosing. Attempts have been made to restore normal coagulation after treatment with new DOAs using compounds such as recombinant activated factor VII (rFVIIa), prothrombin complex concentrate (PCC), or FEIBA (factor eight inhibitor bypassing activity). Limited pre-clinical data and even less clinical evidence are available on the usefulness of these methods in restoring normal coagulation for the emergency management of critical bleeding episodes. Evaluating the utility of DOAs is further complicated by the fact that it is unknown how predictive established test systems are of the bleeding risks. Clinical practice requires further evaluation of the emergency management options for the new DOAs to define the agents and the doses that are most useful. Furthermore, patients receiving long-term treatment with a DOA are likely to undergo elective surgery at some point, and there is lack of evidence regarding perioperative treatment regimens under such conditions. This review summarises potential bleeding management options and available data on the new DOAs.

Failure to correct International Normalized Ratio and mortality among patients with warfarin-related major bleeding: an analysis of electronic health records

BACKGROUND

Delayed correction of blood clotting times as measured by the International Normalized Ratio (INR) is associated with adverse outcomes among certain patients with warfarin-related major bleeding. However, there are limited data on the association between INR correction and mortality.

OBJECTIVE

To assess factors associated with 30-day mortality and time to death in patients receiving fresh frozen plasma (FFP) for warfarin-associated major bleeding.

METHODS

A retrospective database analysis was undertaken with electronic health record data from a large integrated health system. Patients met the following criteria: major hemorrhage diagnosis; INR ≥ 2 on the day before or day of receipt of FFP; and prescription fill for warfarin within 90 days. INR correction (defined as INR ≤ 1.3) was evaluated at the last available test 1 day following the start of FFP administration. Kaplan-Meier curves and Cox proportional hazards models were constructed to assess mortality.

RESULTS

Four hundred and five patients met the selection criteria (mean age of 75 years, 54% male), and 67% remained uncorrected at 1 day following the start of FFP administration. Among all patients, 11% died within 30 days of hospital admission. An uncorrected INR was not associated with a higher risk of 30-day mortality for patients overall, but was statistically significant for the subgroup with intracranial hemorrhage (ICH) (adjusted odds ratio 2.55; 95% confidence interval 1.04-6.28).

CONCLUSIONS

Among the subgroup of major bleeding patients with warfarin-associated ICH, those not correcting to either INR ≤ 1.3 or INR ≤ 1.5 with the use of FFP have an increased rate of mortality at 30 days.

Management dilemmas in patients with mechanical heart valves and warfarin-induced major bleeding

Management of warfarin-induced major bleeding in patients with mechanical heart valves is challenging. There is vast controversy and confusion in the type of treatment required to reverse anticoagulation and stop bleeding as well as the ideal time to restart warfarin therapy safely without recurrence of bleeding and/or thromboembolism. Presently, the treatments available to reverse warfarin-induced bleeding are vitamin K, fresh frozen plasma, prothrombin complex concentrates and recombinant activated factor VIIa. Currently, vitamin K and fresh frozen plasma are the recommended treatments in patients with mechanical heart valves and warfarin-induced major bleeding. The safe use of prothrombin complex concentrates and recombinant activated factor VIIa in patients with mechanical heart valves is controversial and needs well-designed clinical studies. With regard to restarting anticoagulation in patients with warfarin-induced major bleeding and mechanical heart valves, the safe period varies from 7-14 d after the onset of bleeding for patients with intracranial bleed and 48-72 h for patients with extra-cranial bleed. In this review article, we present relevant literature about these controversies and suggest recommendations for management of patients with warfarin-induced bleeding and a mechanical heart valve. Furthermore, there is an urgent need for separate specific guidelines from major associations/ professional societies with regard to mechanical heart valves and warfarin-induced bleeding.

Management of bleeding complications in the anticoagulated patient

As new anticoagulants become available, and the number of anticoagulated patients continues to rise, it is necessary to know how to deal with associated bleeding complications. In this review, reversal strategies for traditional anticoagulants (warfarin and heparin) as well as newer anticoagulants are described. Prothrombin complex concentrates (PPCs) can be used to reverse vitamin K antagonists (VKA), and plasma may be used where they are not available. Recombinant activated factor VII (rFVIIa) may be useful to reverse pentasaccharide anticoagulants. 1-Desamino-8-D-arginine vasopressin (DDAVP), cryoprecipitate, PCCs, and dialysis may help to reverse direct thrombin inhibitors, while rFVIIa seems to be ineffective. The effect of direct factor Xa inhibitors may be reversed by PCCs, FVIIa, or factor Xa concentrates.

Factors associated with failure to correct the international normalised ratio following fresh frozen plasma administration among patients treated for warfarin-related major bleeding. An analysis of electronic health records

This study assessed the frequency and factors associated with failure to correct international normalised ratio (INR) in patients administered fresh frozen plasma (FFP) for warfarin-related major bleeding. This retrospective database analysis used electronic health records from an integrated health system. Patients who received FFP between 01/01/2004 and 01/31/2010, and who met the following criteria were selected: major haemorrhage diagnosis the day before to the day after initial FFP administration; INR ≥2 on the day before or the day of FFP and another INR result available; warfarin prescription within 90 days. INR correction (defined as INR ≤1.3) was evaluated at the last available test up to one day following FFP. A total of 414 patients met selection criteria (mean age 75 years, 53% male, mean Charlson score 2.5). Patients presented with gastrointestinal bleeding (58%), intracranial haemorrhage (38%) and other bleed types (4%). The INR of 67% of patients remained uncorrected at the last available test up to one day following receipt of FFP. In logistic regression analysis, the INR of patients who were older, those with a Charlson score of 4 or greater, and those with non-ICH bleeds (odds ratio vs. intracranial bleeding 0.48; 95% confidence interval 0.31-0.76) were more likely to remain uncorrected within one day following FFP administration. In an alternative definition of correction, (INR ≤1.5), 39% of patients' INRs remained uncorrected. For a substantial proportion of patients, the INRs remain inadequately or uncorrected following FFP administration, with estimates varying depending on the INR threshold used.

Emergency reversal of anticoagulation: from theory to real use of prothrombin complex concentrates. A retrospective Italian experience

BACKGROUND

Prothrombin Complex Concentrates (PCC) are administered to normalise blood coagulation in patients receiving oral anticoagulant therapy (OAT). Rapid reversal of OAT is essential in case of major bleeding, internal haemorrhage or surgery.The primary end-point was to evaluate whether PCC in our hospital were being used in compliance with international and national guidelines for the reversal of OAT on an emergency basis. The secondary end-point was to evaluate the efficacy and safety of PCC.

MATERIALS AND METHODS

All patients receiving OAT who required rapid reversal anticoagulation because they had to undergo emergency surgery or urgent invasive techniques following an overdose of oral anticoagulants were eligible for this retrospective observational study.

RESULTS

Forty-seven patients receiving OAT who needed rapid reverse of anticoagulation were enrolled in our study. The patients were divided in two groups: (i) group A (n=23), patients needed haemostatic treatment before neurosurgery after a head injury and (ii) group B (n=24), patients with critical haemorrhage because of an overdose of oral anticoagulants. The International Normalised Ratio (INR) was checked before and after infusion of the PCC. The mean INR in group A was 2.7 before and 1.43 after infusion of the PCC; in group B the mean INR of 6.58, before and 1.92 after drug infusion. The use of vitamin K, fresh-frozen plasma and red blood cells was also considered. During our study 22 patients died, but no adverse effects following PCC administration were recorded.

DISCUSSION

In our study three-factor-PCC was found to be effective and safe in rapidly reversing the effects of OAT, although it was not always administered in accordance with international or national guidelines. The dose, time of administration and monitoring often differed from those recommended. In the light of these findings, we advocate the use of single standard protocol to guide the correct use of PCC in each hospital ward.

Using Prothrombin Complex Concentrates to Rapidly Reverse Oral Anticoagulant Effects

Warfarin is a commonly prescribed anticoagulant that may, in selected situations, require rapid reversal of its effects. Several approaches to achieve reversal have been explored, including the administration of prothrombin complex concentrates (PCCs), Many factors can influence determination of an appropriate PCC dose and the resulting effects. Considerations on the use of PCC products to expedite the reversal of warfarin are described.

How I treat warfarin-associated coagulopathy in patients with intracerebral hemorrhage

Intracerebral hemorrhage in patients with warfarin-associated coagulopathy is an increasingly common life-threatening condition that requires emergent management. The evolution of therapeutic options in this setting, as well as recently published guidelines, has resulted in some heterogeneity in recommendations by professional societies. This heterogeneity can be attributed to lack of evidence-based support for plasma therapy; the variability in availability of prothrombin complex concentrates; the variability in the coagulation factor levels and contents of prothrombin complex concentrates; ambiguity about the optimal dose and route of administration of vitamin K; and the lack of standardized clinical care pathways, particularly in community hospitals, for the management of these critical care patients. In this review, we summarize the relevant literature about these controversies and present recommendations for management of patients with warfarin-associated coagulopathy and intracerebral hemorrhage.

[Serious hemorrhages related to vitamin K antagonist treated by prothrombic complexes: retrospective study conducted in 2008]

PURPOSE

Vitamin K antagonist are widely used and clearly useful in the prevention of thrombotic and embolic events. However, they expose to hemorrhagic risk. The aim of this retrospective study was to describe the serious hemorrhagic events that occurred in patients treated with vitamin K antagonist and that required administration of prothrombotic complexes concentrates.

METHODS

A comparative analysis of the file of the central pharmacy (that dispensed the prothrombotic complexes concentrates) and patient data of the department of medical information was perform to ascertain the population of patients having received some prothrombotic complexes concentrates. Then, hospitalization reports were consulted to select the patients having presented a severe bleeding while receveiving vitamin K antagonist. We collected patients' characteristics, bleeding location, INR values, emergency care, seriousness and medical issue. Imputability was determined with the French method of pharmacovigilance.

RESULTS

In 2008, in Caen University hospital, 80 patients received prothrombotic complexes concentrates in the context of a serious hemorrhage due to vitamin K antagonist. Their mean age was 75years and the most common presentation was a neurological hemorrhage (38,7%). For 63,8% of the patients, there was an overdose in vitamin K antagonist. Twenty-two patients died during their hospitalization and 10 others presented later sequelas. None of the patients included in this study had been spontaneously declared to the pharmacovigilance. High imputability scores were positively correlated with INR (P=0.0002).

CONCLUSION

Quality of emergency care of hemorrhagic events due to vitamin K antagonist could be improved with a better application of the professional recommendations and a spontaneous declaration to pharmacovigilance.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.