Introduction
Injury is the second leading cause of death worldwide,
and as much as 40% of injury-related mortality is
attributed to uncontrollable hemorrhage (1). In both
the civilian and military setting, uncontrolled hemorrhage
is the leading preventable cause of postinjury
mortality (2). This persists despite establishment of
regionalized trauma systems and advances in the
management of severely injured patients.
Hemostasis is the physiologic cessation of bleeding
achieved by the fluid and cellular phases of clotting.
In the critically injured patient, often in hemorrhagic
shock, coagulopathy results from a hemostatic system
that is challenged by physiologic extremis. This leads
to dysfunctional thrombus formation and ultimately
uncontrolled bleeding. Understanding the mechanisms
of hemostasis that lead to an effective control of
bleeding is key in order to reduce postinjury mortality.
The purpose of this review is to examine the current
knowledge gaps in trauma-induced coagulopathy
(TIC) and their relevance to management.
Methods
A review of the current literature was performed by
collecting PUBMED references related to TIC. Data
were then critically analyzed and summarized based
on the authors’ clinical and research perspective, as
well as that reported by other institutions and researchers
interested in TIC. A particular focus was placed on
those aspects of coagulopathy in which agreement
among clinical and basic scientists is currently lacking:
these include pathophysiology, goal-directed assessment
and management, and the role of blood components
and factor therapy.
Pathophysiology
In 1954, Mario Stefanini (3) addressed the New York
Academy of Medicine with a presentation reviewing the
state-of-the-art knowledge on the “Basic Mechanisms of
Hemostasis.”. He acknowledged how the preceding
number of theories on hemostatic mechanisms had
always exceeded and not always respected the confirmed
experimental facts. He then admitted that the
recent accumulation of new findings had almost been
too rapid for their orderly incorporation into a logically
working pattern, and stated that a state of “orderly ignorance”
had transitioned to one of “confused enlightenment.”
Stefanini concluded that the ponderous literature
on hemostasis may be a classic example of the human mind’s infinite ability for abstract speculation. Our current
understanding of coagulopathy may not be far
from what Stefanini concluded 60 years ago.
The physiological mechanisms of hemostasis are
complex, particularly in the dysregulated states of
coagulopathy and inflammation in response to severe
injury. Substantial knowledge has been gained by
characterizing the molecules and some of the pathways
that drive clot formation. However, the regulation
of the clotting system and its cross talk with other
adaptive mechanisms, particularly inflammation,
remains poorly understood. Our attempts to manage
coagulopathy have so far parted from our basic comprehension
of clot formation under homeostatic conditions,
expecting that extrapolating these mechanisms
to simply a more severe pathologic state will explain
what we observe clinically. However, the more we
learn about hemostasis and the physiology of shock, it
becomes evident that unique mechanisms such as certain
protein functions and cell signaling exist under
conditions of extremis.