Inflammation
Massive injury leads to activation of the immune system
and the initial inflammatory immune response and has been
defined as systemic inflammatory response syndrome
(SIRS). This initial response is usually compounded by secondary
insults like infections, ischemia/reperfusion or surgeries.
10 Inflammation shifts the hemostatic mechanisms in
favor of thrombosis. Multiple mechanisms are at play
including upregulation of tissue factor leading to the initiation
of clotting, amplification of the clotting process by
augmenting exposure of cellular coagulant phospholipids,
inhibition of fibrinolysis by elevating plasminogen activator
inhibitor1 and decreases in natural anticoagulant pathways,
leading to downregulation of the protein C anticoagulant
pathway. The decreased function of the natural anticoagulant
pathways may be particularly problematic becausethese appear to play a role in dampening the inflammatory
responses.11
Activation of serine proteases can cause inflammation
through cell surface receptors and activation of the complement
system.
Detection of acute traumatic coagulopathy
Routine tests for coagulation
Routine practice to detect trauma induced coagulopathy has
been by various parameters like INR (International Normalized
Ratio), APTT (Activated Partial Thromboplastin Time),
platelet counts and fibrinogen levels.
APTT and INR >1.5 times are considered as indicators of
coagulopathy as it is often assumed that the conventional
coagulation screens (INR and APTT) monitor coagulation;
however, these tests monitor only the initial phase of blood
coagulation and represent only the first 4% of thrombin production.
12 It is therefore possible that the conventional coagulation
screen appears normal, while the overall state of blood
coagulation is abnormal. Another important short coming of
the standard coagulation tests is that these tests are time
consuming. Median turnaround time of 78e88 min has been
reported in various studies.13,14
Thromboelastography (TEG)
Described by Hartert in 1948, thromboelastography is now
widely used as a point of care tool to detect acute coagulopathy
of trauma. It gives a rapid overview of the main players in
the coagulation system like initiation factors, fibrinogen,
platelet function and fibrinolytic components.15
A small volume of blood (0.3 ml) is incubated in an oscillating
cup at 37 _C or patients body temperature. A pin is
suspended in the cup from a torsion wire with an electrical
transducer. In the early phase when, there is no clot the
oscillatorymovements of the cuff do not affect the suspended
pin. When a clot is formed, the fibrin which is formed between
the cup and pin transmits the movements which can be
detected at the pin and a trace is generated. (The various interpretations
are described in Fig. 1 and Table 1).
Though thromboelastography has emerged as a point of
care device in identifying coagulopathy in acute trauma, it
has important limitations. Studies have found that
thromboelastography was unable to distinguish coagulopathies
caused by hemodilution from that caused by thrombocytopenia
thereby leading to unwarranted platelet transfusions. This limitation
is overcome by the advent of thromboelastometry.
Another significant limitation of viscoelastic tests is the lack of
sensitivity to detect and monitor platelet dysfunction due to
antiplatelet drugs. The view that the effect of hypothermia will
not be recognized if the temperature of the blood sample
analyzed is not adjusted to patient’s body temperature is no
longer supported.