My Patience Is Running Thin, But So Is Your Blood (Anticoagulants)

When there’s a traumatic injury to the body, hemostasis is the body’s way of minimizing blood loss. Hemostasis is a two-step process: (1) platelet aggregation which results in an initial platelet plug and (2) the coagulation cascade that creates a fibrin mesh to stabilize the clot. Blood clots (thrombi and emboli) can also form pathologically and cause multiple problems (such as acute coronary syndrome, ischemic stroke, and pulmonary embolism). When we want to reduce the rate of clot formation, blood thinners (more formally known as antithrombotics) are used. Antithrombotics are agents that block the clot formation during either of the two aforementioned steps of the hemostasis process.

There are two main classes of antithrombotics – antiplatelets and anticoagulants. Antiplatelets are medications that inhibit the formation of the initial platelet plug, and anticoagulants are medications that block a step in the coagulation cascade. Multiple biochemical processes are required to create the initial platelet plug (figure 1), and hence multiple classes of antiplatelet drugs exist to inhibit platelet aggregation (table 1).  

Figure 1

(from: Kumar, et al, 2009)

Table 1

In a similar fashion, the coagulation cascade (figure 2) comprises multiple steps that may be inhibited to help reduce thrombus formation. The various anticoagulants, including the newer class of direct oral anticoagulants (DOACs) are listed (table 2).  

Figure 2 

(from: Ilesanmi, 2010)

Table 2

Generally, these antithrombotics help reduce the incidence of disease states caused by thombi and emboli, including processes such as ACS, TIA, stroke, DVT, and PE.³ The precipitants of these clots can be understood through Virchow’s triad of hemostasis, endothelial injury, and hypercoagulability. Antithrombotics help reduce the rate of clots which may be due to hemostasis (i.e. atrial fibrillation, immobilization), endothelial injury (i.e. after PCI), or hypercoagulability (i.e. antiphospholipid syndrome).

The DOACs are an important class of anticoagulants that are becoming more prevalent as well.  They were created as an easier alternative to LMWH and warfarin for patients requiring chronic anticoagulation.⁴ Although they offer several benefits, including quick onset and decreased blood test monitoring, these medications are more difficult to reverse when patients are bleeding.

Antithrombotics have a significant role in management of patients in the ED. For example, in patients with active bleeding or the potential to bleed, e.g. GI bleed or trauma, the presence of antithrombotics in the patient will influence care. Although obtaining labs such as CBC and coags can be helpful, the effect of many of the medications such as the newer DOACs, aren’t adequately reflected on routine labs.⁵ Obtaining a patient’s antithrombotic regimen can help direct you in choosing the proper reversal agent.^3,6

In addition, different antithrombotics at different doses are frequently started in the ED for diseases ranging from myocardial infarction to pulmonary embolism. A familiarity with them can mean life-saving results. Lastly, be on the lookout for these antithrombotics on a patient’s medication list. The medication and the dosage can help clarify a patient’s medical history when not readily available to help create a more accurate clinical picture. The information may also offer insight into severity of their underlying medical condition, which may help you to risk stratify and deliver better care.