Ex vivo clot lysis measurements in blood samples of healthy volunteers.

Thromboelastometry is a point of care testing device that determines the
viscoelastic properties of clot formation in whole blood. It is currently the
only clinically device that is able to measure clot lysis. A previous study by
our group investigated the incidence and severity of hyperfibrinolysis in
patients after out-of-hospital cardiac arrest. Using thromboelastometry, we
found that approximately 50% of these patients had hyperfibrinolysis. There is
however only limited research available using thromboelastometry for the
diagnosis of hyperfibrinolysis, and there is no consensus on witch parameter is
suitable to determine the degree of hyperfibrinolysis.
Schöchl et al. used a categorical scale dividing them into fulminant,
intermediate and late hyperfibrinolysis based on the time to reach complete
lysis. A previous study performed by Nielsen et al. investigated the relation
between thromboelastography parameters and increasing tPA concentrations in
blood from healthy volunteers, and they concluded that thromboelastography
could be an appropriate laboratory and clinical tool for quantifying
fibrinolysis.
Recent findings by our group showed that the lysis onset time (LOT) shows a
linear relation with markers of hypoperfusion in patients after out of hospital
cardiac arrest. Our findings suggested that the lysis onset time is a more
accurate marker for the severity of hyperfibrinolysis than the maximum lysis.
Whether the LOT is indeed a good measure of hyperfibrinolysis, and linearly
related to tPA concentrations, has however never been investigated. Moreover, A
recent study by Panes et al. suggested that platelets have a pro-fibrinolytic
function. They showed a faster clot lysis in platelet-rich clots compared to
platelet-poor clots after addition of tranexamic acid that was absent
platelet-free plasma.

In the present ex vivo study we aim to determine whether thromboelastometry
parameters, in particular the lysis onset time (LOT), are appropriate to
determine and quantify the degree of hyperfibrinolysis. Furthermore, we will
study the association of increasing tPA concentrations with the lysis onset
time and platelet function.

This is a prospective, single center, observational study in blood samples of
healthy volunteers and will be performed in the department of Anesthesiology of
the VUmc in Amsterdam.

The burden associated with participation is minimal being limited to 10 minutes
required for a single blood withdrawl. The risk is equal to the risk of venous
blood withdrawl and is limited to a hematoma at the site of puncture.