이 에피소드에 관해
Jeff: Welcome back to EMplify the podcast corollary to EB Medicine’s Emergency medicine Practice. I’m Jeff Nusbaum and I’m back with Nachi Gupta. This month, we are tackling a topic for which the literature continues to rapidly change - we’re talking about the ED management of patients taking direct oral anticoagulants or DOACs, previously called novel oral anticoagulants or NOACs.
Nachi: Specifically, we’ll be focusing on the use of DOACs for the indications of stroke prevention in atrial fibrillation and the treatment and prevention of recurrent venous thromboembolisms.
Jeff: This month’s article was authored by Dr. Patrick Maher and Dr. Emily Taub of the Icahn School of Medicine at Mount Sinai, and it was peer reviewed by Dr. Dowin Boatright from Yale, Dr. Natalie Kreitzer from the University of Cincinnati, and Dr. Isaac Tawil from the University of New Mexico.
Nachi: In their quest to update the last Emergency Medicine Practice issue on this topic which was published in 2013, they reviewed over 200 articles from 2000 to present in addition to 5 systematic reviews in the cochrane database, as well as guidelines from the American Heart Association, European society of cardiology, and the american college of cardiology.
Jeff: Thanks to a strong literature base, Dr’s Maher and Taub found good quality evidence regarding safety and efficacy of the DOACs in relation to warfarin and the heparin-based anticoagulants.
Nachi: But do note that the literature directly comparing the DOACs is far more limited and mostly of poor quality.
Show More vJeff: Fair enough, we’ll take what we can get.
Nachi: Well, I’m sure more of those studies are still coming.
Jeff: Agree. Let’s get started with some basics. Not surprisingly, DOACs now account for a similar proportion of office visits for anticoagulant use as warfarin.
Nachi: With huge benefits including reduced need for monitoring and a potential for reduced bleeding complications, this certainly isn’t surprising.
Jeff: Though those benefits are not without challenges - most notably the lack of an effective reversal agent and the risk of unintentional overdose in patients with altered drug metabolism.
Nachi: Like all things in medicine, it’s about balancing and finding an acceptable risk/benefit profile.
Jeff: True. Let’s talk pathophysiology for a minute - the control of coagulation in the human body is a balance between hemorrhage and thrombosis, mediated by an extensive number of procoagulant and anticoagulant proteins.
Nachi: Before the development of the DOACs, vitamin K antagonists controlled the brunt of the market. As their name suggests, they work by inhibiting the action of vitamin K, and thus reducing the production of clotting factors 2, 7, 9, and 10, and the anticoagulant proteins C and S.
Jeff: Unfortunately, these agents have a narrow therapeutic window and many drug-drug interactions, and they require frequent monitoring - making them less desirable to many.
Nachi: However, in 2010, the FDA approved the first DOAC, a real game-changer. The DOACs currently on the market work by one of two mechanisms - direct thrombin inhibition or factor Xa inhibition.
Jeff: DOACs are currently approved for stroke prevention in nonvalvular afib, treatment of VTE, VTE prophylaxis, and reduction of major cardiovascular events in stable cardiovascular disease. Studies are underway to test their safety and efficacy in arterial and venous thromboembolism, prevention of embolic stroke in afib, ACS, cancer-associated thrombosis, upper extremity DVT, and mesenteric thrombosis.
Nachi: Direct thrombin inhibitors like Dabigatran, tradename Pradaxa, was the first FDA approved DOAC. It works by directly inhibiting thrombin, or factor IIa, which is a serine protease that converts soluble fibrinogen into fibrin for clot formation.
Jeff: Dabigatran comes in doses of 75 and 150 mg. The dose depends on your renal function, and, with a half-life of 12-15 hours, is taken twice daily. Note the drastically reduced half-life as compared to warfarin, which has a half-life of up to 60 hours.
Nachi: The RE-LY trial for afib found that taking 150 mg of Dabigatran BID had a lower rate of stroke and systemic embolism than warfarin with a similar rate of major hemorrhage. Dabigatran also had lower rates of fatal and traumatic intracerebral hemorrhage than warfarin.
Jeff: A separate RCT found similar efficacy in treating acute VTE and preventing recurrence compared with warfarin, with reduced rates of hemorrhage!
Nachi: Less monitoring, less hemorrhage, similar efficacy, I’m sold!!!
Jeff: Slow down, there’s lots of other great agents out there, let’s get through them all first...
Nachi: Ok, so next up we have the Factor Xa inhibitors, Rivaroxaban, apixaban, edoxaban, and betrixaban.As the name suggests, these medications work by directly inhibiting the clotting of factor Xa, which works in the clotting cascade to convert prothrombin to thrombin.
Jeff: Rivaroxaban, trade name Xarelto, the second FDA approved DOAC, is used for stroke prevention in those with nonvalvular afib and VTE treatment. After taking 15 mg BID for the first 21 days, rivaroxaban is typically dosed at 20 mg daily with adjustments for reduced renal function.
Nachi: The Rocket AF trial found that rivaroxaban is noninferior to warfarin for stroke and systemic embolism prevention without a significant difference in risk of major bleeding. Interestingly, GI bleeding may be higher in the rivaroxaban group, though the overall incidence was very low in both groups at about 0.4% of patients per year.
Jeff: In the Einstein trial, patients with VTE were randomized to rivaroxaban or standard therapy. In the end, they reported similar rates of recurrence and bleeding outcomes for acute treatment. Continuing therapy beyond the acute period resulted in similar rates of VTE recurrence and bleeding episodes to treatment with aspirin alone.
Nachi: Next we have apixaban, tradename Eliquis. Apixaban is approved for afib and the treatment of venous thromboembolism. It’s typically dosed as 10 mg BID for 7 days followed by 5 mg BID with dose reductions for the elderly and those with renal failure.
Jeff: In the Aristotle trial, when compared to warfarin, apixaban was superior in preventing stroke and systemic embolism with lower mortality and bleeding. Rates of major hemorrhage-related mortality were also nearly cut in half at 30 days when compared to warfarin.
Nachi: For the treatment of venous thromboembolism, the literature shows that apixaban has a similar efficacy to warfarin in preventing recurrence with less bleeding complications.
Jeff: Unfortunately, with polypharmacy, there is increased risk of thromboembolic and hemorrhage risks, but this risk is similar to what is seen with warfarin.
Nachi: And as compared to low molecular weight heparin, apixaban had higher bleeding rates without reducing venous thromboembolism events when used for thromboprophylaxis. It’s also been studied in acute ACS, with increased bleeding and no decrease in ischemic events.
Jeff: Edoxaban is up next, approved by the FDA in 2015 for similar indications as the other Factor Xa inhibitors. It’s recommended that edoxaban be given parenterally for 5-10 days prior to starting oral treatment for VTE, which is actually similar to dabigatran. It has similar levels of VTE recurrence with fewer major bleeding episodes compared to warfarin. It has also been used with similar effects and less major bleeding for stroke prevention in afib. In the setting of cancer related DVTs specifically, as compared to low molecular weight heparin, one RCT showed lower rates of VTE but higher rates of major bleeding when compared to dalteparin.
Nachi: Next we have Betrixaban, the latest Factor Xa inhibitor to be approved, back in 2017. Because it’s utility is limited to venous thromboembolism prophylaxis in mostly medically ill inpatients, it’s unlikely to be encountered by emergency physicians very frequently.
Jeff: As a one sentence FYI though - note that in recent trials, betrixaban reduced the rate of VTE with equivalent rates of bleeding and reduced the rate of stroke with an increased rate of major and clinically relevant non-major bleeding as compared to enoxaparin.
Nachi: Well that was a ton of information and background on the DOACs. Let’s move on to your favorite section - prehospital medicine.
Jeff: Not a ton to add here this month. Perhaps, most importantly, prehospital providers should specifically ask about DOAC usage, especially in trauma, given increased rates of complications and potential need for surgery. This can help with destination selection when relevant. Interestingly, one retrospective study found limited agreement between EMS records and hospital documentation on current DOAC usage.
Nachi: Extremely important to identify DOAC use early. Once the patient arrives in the ED, you can begin your focused history and physical. Make sure to get the name, dose, and time of last administration of any DOAC. Pay particular attention to the med list and the presence of CKD which could point to altered DOAC metabolism.
Jeff: In terms of the physical and initial work up - let the sites of bleeding or potential sites of bleeding guide your work up. And don’t forget about the rectal exam, which potentially has some added value here - since DOACs increase the risk of GI bleeding.
Nachi: Pretty straight forward history and physical, let’s talk diagnostic studies.
Jeff: First up is CT. There are no clear cut guidel...
