[Proper use of oral anticoagulants in the elderly patient]

Direct oral anticoagulants (DOACs) are tending to supplant antivitamin K inhibitors (VKAs) in their common indications, dominated in elderly patients by atrial fibrillation and venous thromboembolism. Nevertheless, it remains necessary to know how best to use VKAs for which there are still indications. It is also important not to assume that AODs can be prescribed without risk, while ignoring certain particularities in their handling, particularly in the most fragile patients with co-morbidities and multiple medications.

Is antivitamin K reversal required in patients with cirrhosis undergoing liver transplantation?

BACKGROUND

Antivitamin K agent (AVK) reversal in patients with cirrhosis awaiting liver transplantation (LT) is not defined in guidelines. We investigated the effect of reversion with prothrombin complex concentrate (PCC) on intraoperative transfusion, bleeding, and safety in LT patients on AVK.

STUDY DESIGN AND METHODS

In 511 patients undergoing LT, we identified 25 patients treated with AVK (AVK group) and 13 patients with incidental portal vein thrombosis (PVT) without AVK (incidental PVT group). Fifty patients who underwent LT without PVT or AVK matched by age, model for end stage of liver disease (MELD), body mass index (BMI), and cirrhosis etiology were selected as the control group.

RESULTS

There were no significant differences between the three groups in intraoperative blood loss, transfusion, and postoperative bleeding. In the AVK group, there were no differences between patients who received PCC and those who did not in intraoperative blood loss, red blood cells, fibrinogen, and platelet transfusion, or postoperative bleeding. PCC use had no effect on RBC transfusion in patients who had international normalized ratio or clotting time above versus below median values of the two parameters at baseline (2.3 and 103 s, respectively). No thrombotic events were detected in patients who received PCC.

DISCUSSION

These data suggest that systematic administration of PCC to revert AVK prior to LT should be reconsidered.

[Quality and determinants of anticoagulation therapy by AVK in elderly subjects: study of a continuous series of 155 patients hospitalized in geriatric medicine]

AVK could be prescribed in elderly patients over 75 years for the prevention of thromboembolic complications of atrial fibrillation (AF). The objective of this study was to study the quality of the anticoagulation balance by AVK and its determinants. Inclusion of all patients ≥ 75 years of age treated with AVK for an AF hospitalized in the acute geriatric department of the University hospital of Dijon. The balance of the AVK treatment was determined by the input INR and the calculation of the TTR. The last four INRs prior to admission were retrospectively collected for its calculation. Each patient had a standardized geriatric evaluation (EGS): lifestyle, MMSE, nutritional status (albumin), polypathology (Charlson), level of dependence (ADL-IADL). Bleeding complication were collected. 155 patients aged over 75 years (87±5.6 years, 88 women and 67 men) were included. The mean TTR was 55.4±31.2%. Only 46% of patients had a correct TTR (≥ 75%). The balance was significantly worse in women than in men (49.3±29.5 vs 60.1±31.8%; p=0.0326), and in case of haematological pathology (41.7±27.1 vs 57.2± 9.8; p=0.047) but better with high BMI (r=0.416, p=0.001). No EGS parameters were associated with the quality of anticoagulation. The control of AVK therapy is insufficient in geriatric elderly subjects. No modifiable explicative geriatric factor has been identified. If AVK remains a therapeutic option, direct oral anticoaulants should be considered as the first choice.

Study of the efficiency of anticoagulant rodenticides to control Mus musculus domesticus introgressed with Mus spretus Vkorc1

BACKGROUND

Antivitamin K anticoagulant (AVK) rodenticides are commonly used to control rodent pests worldwide. They specifically inhibit the VKORC1 enzyme essential for the recycling of vitamin K, and thus prevent blood clotting and cause death by haemorrhage. Numerous mutations or polymorphisms of the Vkorc1 gene were reported in rodents, and some led to resistance to rodenticides. In house mice (Mus musculus domesticus), adaptive introgression of the Vkorc1 gene from the Algerian mouse (Mus spretus) was reported. This adaptive introgression causes the substitution of four amino acids in M. musculus domesticus.

RESULTS

The consequences of introgression were assessed by (i) the characterisation of the in vivo resistant phenotype of adaptive Vkorc1^spr -introgressed mice, (ii) the characterisation of the ex vivo resistance phenotype of the liver VKOR activity and (iii) the comparison of these results with the properties of recombinant VKORC1^spr protein expressed in yeast. The resistance factor (from 1 to 120) induced by the four introgressed polymorphisms obtained using these three approaches was dependent on the AVKs used but were highly correlated among the three approaches.

CONCLUSION

The four introgressed polymorphisms were clearly the cause of the strong resistant phenotype observed in the field. In the context of strong selection pressure due to the extensive use of AVKs, this resistant phenotype may explain the widespread distribution of this genotype from Spain to Germany. © 2016 Society of Chemical Industry.

Evidence of a target resistance to antivitamin K rodenticides in the roof rat Rattus rattus: identification and characterisation of a novel Y25F mutation in the Vkorc1 gene

BACKGROUND

In spite of intensive use of bromadiolone, rodent control was inefficient on a farm infested by rats in Zaragoza, Spain. While metabolic resistance was previously described in this rodent species, the observation of a target resistance to antivitamin K rodenticides had been poorly documented in Rattus rattus.

RESULTS

From rats trapped on the farm, cytochrome b and Vkorc1 genes were amplified by PCR and sequenced in order to identify species and detect potential Vkorc1 mutations. VKORC1-deduced amino acid sequences were thus expressed in Pichia pastoris, and inhibition constants towards various rodenticides were determined. The ten rats trapped on the farm were all identified as R. rattus. They were found to be homozygous for the g.74A>T nucleotide replacement in exon 1 of the Vkorc1 gene, leading to p.Y25F mutation. This mutation led to increased apparent inhibition constants towards various rodenticides, probably caused by a partial loss of helical structure of TM4.

CONCLUSION

The p.Y25F mutation detected in the Vkorc1 gene in R. rattus trapped on the Spanish farm is associated with the resistance phenotype to bromadiolone that has been observed. It is the first evidence of target resistance to antivitamin K anticoagulants in R. rattus.