Reversing targeted oral anticoagulants

Factor VIII and Factor V Membrane Bound Complexes

The formation of membrane-bound complexes between specific coagulation factors at different cell surfaces is required for effective blood clotting. The most important of these complexes, the intrinsic Tenase and Prothrombinase complexes, are formed on the activated platelet surface during the propagation phase of coagulation. These two complexes are highly specific in their assembly mechanism and function modulated by anionic membranes, thus offering desirable targets for pharmaceutical interventions. Factor V (FV) and factor VIII (FVIII) are highly homologous non-enzymatic proteins. In their active state, FVa and FVIIIa serve as cofactors for the respective serine proteases factor Xa (FXa) and factor IXa (FIXa), significantly increasing their catalytic activity. This is achieved by forming well organized membrane-bound complexes at the phosphatidylserine rich activated platelet membrane in the presence of Ca²⁺ ions. The tenase (FVIIIa/FIXa) complex, catalyzes the proteolytic conversion of FX to FXa. Subsequently the prothrombinase (FVa/FXa) complex catalyzes the conversion of prothrombin to thrombin, required for efficient blood clotting. Although significant knowledge of FV and FVIII biochemistry and regulation has been achieved, the molecular mechanisms of their function are yet to be defined. Understanding the geometric assembly of the tenase and prothrombinase complexes is paramount in defining the structural basis of bleeding and thrombotic disorders. Such knowledge will enable the design of efficient pro- and anticoagulant therapies critical for regulating abnormal hemostasis. In this chapter, we will summarize the findings to date, showing our achievement in the field and outlining the future findings required to grasp the complexity of these proteins.

Geriatric trauma

PURPOSE OF REVIEW

The landscape of trauma is changing due to an aging population. Geriatric patients represent an increasing number and proportion of trauma admissions and deaths. This review explores recent literature on geriatric trauma, including triage criteria, assessment of frailty, fall-related injury, treatment of head injury complicated by coagulopathy, goals of care, and the need for ongoing education of all surgeons in the care of the elderly.

RECENT FINDINGS

Early identification of high-risk geriatric patients is imperative to initiate early resuscitative efforts. Geriatric patients are typically undertriaged because of their baseline frailty being underappreciated; however, centers that see more geriatric patients do better. Rapid reversal of anticoagulation is important in preventing progression of brain injury. Anticipation of difficult disposition necessitates early involvement of physical therapy for rehabilitation and case management for appropriate placement.

SUMMARY

Optimal care of geriatric trauma patients will be based on the well established tenets of trauma resuscitation and injury repair, but with distinct elements that address the physiological and anatomical challenges presented by geriatric patients.

Rivaroxaban-Induced Nontraumatic Spinal Subdural Hematoma: An Uncommon Yet Life-Threatening Complication

In the last decade, the desire for safer oral anticoagulants (OACs) led to the emergence of newer drugs. Available clinical trials demonstrated a lower risk of OACs-associated life-threatening bleeding events, including intracranial hemorrhage, compared to warfarin. Nontraumatic spinal hematoma is an uncommon yet life-threatening neurosurgical emergency that can be associated with the use of these agents. Rivaroxaban, one of the newly approved OACs, is a direct factor Xa inhibitor. To the best of our knowledge, to date, only two published cases report the incidence of rivaroxaban-induced nontraumatic spinal subdural hematoma (SSDH). Our case is the third one described and the first one to involve the cervicothoracic spine.