[Evolution of thromboprophylaxis after hip and knee arthroplasties]. / Évolution de la thromboprophylaxie après prothèses de hanche et de genou.

Venous thrombotic events frequently complicate major elective arthroplasties such as hip and knee replacements. The risk of proximal deep vein thrombosis and pulmonary embolism is estimated at 5 %. For decades, the use of low-dose heparins for up to 5 weeks post-surgery has helped to reduce the risk of thrombotic complications. In this narrative review, we describe the evidence supporting the use of direct oral anticoagulants (in Switzerland - rivaroxaban and apixaban), whose risk-benefit ratios appears superior to that of heparins, at a lower cost. Hybrid strategies combining a short-term anticoagulant followed by low-dose aspirin are also recommended for patients deemed at low thrombotic risk.

Les thromboses veineuses profondes proximales et les embolies pulmonaires sont des complications redoutées après des interventions électives majeures en chirurgie orthopédique (prothèses totales de la hanche et du genou), avec une incidence cumulée estimée à 5 %. Depuis des décennies, ce risque est réduit par l'utilisation d'héparine à dose préventive jusqu'à 5 semaines postopératoires. Dans cette revue narrative, nous décrivons les évidences motivant l'utilisation des anticoagulants oraux directs (rivaroxaban et apixaban en Suisse) qui semblent présenter un rapport bénéfice-risque supérieur aux héparines, à un coût moindre. Des stratégies hybrides comprenant un anticoagulant puis l'aspirine sont désormais également recommandées chez des patients considérés à bas risque thrombotique.

Thrombin generation and fibrin clot structure after vitamin D supplementation.

OBJECTIVE: Vitamin D deficiency is associated with increased risks of arterial and venous cardiovascular events. Hypothetically, supplementation with vitamin D may lead to a less prothrombotic phenotype, as measured by global coagulation assays and fibrin clot structure. METHODS: In this prospective cohort study, we enrolled adult outpatients attending the Primary Care Division of the Geneva University Hospitals with a severe vitamin D deficiency (25-hydroxyvitamin-D3 (25-OHD) <25 nmol/L), excluding obese patients or with a recent acute medical event. We evaluated changes in coagulation times, thrombin generation assay, clot formation and clot lysis time, 25-OHD and parathormone before and 1-3 months after cholecalciferol oral supplementation with one-time 300,000 IU then 800 IU daily. Paired t-tests with a two-sided alpha of 0.05 compared absolute mean differences. RESULTS: The 48 participants had a mean age of 43.8 ± 13.8 years. After supplementation, 25-OHD levels increased from 17.9 ± 4.6 nmol/L to 62.5 ± 20.7 nmol/L 6.4 ± 3.0 weeks after inclusion. Endogenous thrombin potential and thrombin generation peak values both decreased significantly (-95.4 nM × min (95%CI -127.9 to -62.8), P < 0.001; -15.1 nM (-23.3 to -6.8), P < 0.001). The maximum absorbance by turbidimetry decreased significantly (P = 0.001) after supplementation. There was no change in clot lysis time, coagulation times or plasminogen activator inhibitor-1 and homocysteine levels. CONCLUSIONS: In severe vitamin D deficiency, a high-dose cholecalciferol supplementation was associated with a reduction in thrombin generation and an average decreased number of fibrin protofibrils per fibers and fibrin fiber size measured by turbidimetry. This suggests that severe vitamin D deficiency may be associated with a potentially reversible prothrombotic profile.

The effect of calcium plus vitamin D supplementation on the risk of venous thromboembolism. From the Women's Health Initiative Randomized Controlled Trial.

Experimental and epidemiological studies suggest that vitamin D may be implicated in haemostatic regulations and influence the risk of venous thromboembolism (VTE). The aim of this study was to investigate whether oral supplementation of vitamin D3 combined with calcium reduces the risk of VTE. In the randomised, double-blind, placebo-controlled Women's Health Initiative Calcium Plus Vitamin D trial, 36,282 postmenopausal women aged 50-79 years were randomised to receive 1,000 mg of calcium carbonate and 400 IU of vitamin D3 per day (n=18,176) or a matching placebo (n=18,106) during an average of seven years. This secondary analysis of the trial compared the incidence of VTE by treatment group using an intention-to-treat Cox regression analysis. The incidence of VTE did not differ between women randomised to calcium plus vitamin D and women randomised to placebo (320 vs 348 VTE events, respectively; hazard ratio (HR) 0.92, 95 % confidence interval (CI) 0.79-1.07). Results were not modified in an analysis using inverse-probability weights to take non-adherence into account (HR 0.94, 95 %CI 0.73-1.22) or in multiple subgroups. Whereas the risk of a non-idiopathic VTE was similar between groups, the risk of idiopathic VTE was lower in women randomised to calcium plus vitamin D (40 vs 65 events; HR 0.62, 95 %CI 0.42-0.92). In conclusion, daily supplementation with 1,000 mg of calcium and 400 IU of vitamin D did not reduce the overall incidence of VTE in generally healthy postmenopausal women. However, the observed reduced risk of idiopathic VTE in women randomised to calcium and vitamin D warrants further investigations.