However, clinicians who are required to treat life-threatening blood loss may be unfamiliar with the rapid and substantial progress that has been made and is still ongoing concerning this aspect of resuscitation. There are several potential explanations for this uncertainty regarding the management of severe hemorrhage. The definition of MT and the manner by which MT is integrated into DCR strategies can be arbitrary and inexact. By one typically used definition (≥10 units of packed red blood cells within a 24-hour period), a patient may be considered massively transfused after receiving blood at a deliberate rate of one unit every 2 h over the course of 20 h. This is, of course, a distinctly different clinical scenario than a patient receiving the same amount of blood within 2 h or even less. Moreover, resuscitations for massive blood loss are rare events. For example, in our hospital DCR is initiated most frequently by the trauma service although no more than 5% of seriously injured patients require resuscitation of this magnitude ; and, DCR may be required even less frequently to manage, bleeding complications on other services. Furthermore, a major tenet of current DCR strategies involves administration of blood components (plasma and platelets) in a predefined ratio relative to the number of units of RBC's transfused. However, the optimal ratios of these components (and others such as cryoprecipitate) that maximize survival and minimize blood component waste have been difficult to determine and are incompletely defined. Complicating matters still further, newer DCR strategies are based on goal-directed hemostatic resuscitation with rapid point-of-care (POC) viscoelastic assessment of coagulation. Though promising with respect to outcomes, goal-directed DCR presents additional layers of complexity in that a viscoelastic coagulation test requires trained personnel to perform the assay and experienced clinicians to accurately interpret the results. Lastly, whereas the fundamental precepts of hemorrhagic shock should vary little from one location to another, conclusions regarding many pathophysiologic mechanisms of the host response to massive blood loss and opinions on resuscitation strategies for catastrophic bleeding have differed substantially in different parts of the world. For clinicians attempting to discern the concepts and best practices of DCR, these disparities likely intensified uncertainties regarding the process more than any other factor. However, consensus is now emerging on several aspects of DCR as a result of recent international collaborations among experts in shock and resuscitation