Arterial perfusion with t-PA in donation after cardiac death (DCD) to reduce the incidence of non-anastomotic biliary strictures after orthotopic liver transplantation

The incidence of biliary complications such as non-anastomtotic biliary
strictures (NAS), also called ischemic type biliary lesions (ITBL), may be as
high as 25% in DCD donors. NAS are associated with an increased risk of
infection of the biliary tree, frequent admissions to the hospital, endoscopic
treatment and retransplantation. NAS are most likely the result of a complex
mechanism involving ischemic, immunologic and toxic processes which all affect
the the vascular system of the biliary tree. The microvascular supply of the
biliary tree, the peribiliary plexus, stems from the hepatic artery branches
and flows into the hepatic sinusoids. Recent literature has shown that a
decreased blood flow in the peri-biliary plexus after orthotopic liver
transplantation is involved in the development of NAS. The reduction of blood
flow in the peri-biliary plexus is most likely the result of microthrombi which
develop during the cold ischemic time (CIT) and WIT.
The mechanisms which might be involved in the development of NAS are of great
importance since they may provide new insights to develop strategies in order
to prevent this complication. First of all, research has shown that flushing
donor livers with the abovementioned preservation fluids at an increased
pressure reduces the incidence of NAS. Secondly, not properly controlled
studies suggest that adding a thrombolytic agent such as t-PA to the
preservation fluid also seems to reduce the incidence of NAS, probably by
dissolving the microthrombi in the micro-vascular system of the biliary tree.
The most important thrombolytic agents are streptokinase, urokinase and
recombinant tissue-type plasminogen activator. These agents have been widely
used in the clinic and are considered safe. Several studies have been performed
by using thrombolytic agents in order to prevent NAS, which in some cases
showed drastic reductions in NAS. These studies have also shown that the risk
of intra-operative bleeding is not increased.

Prevention of NAS will result in less retransplantations due to NAS. This in
turn will result in a shorter waiting list with less morbidity and more
important less mortality while waiting for a donor liver. Patients will also be
less often hospitalized after OLT for the treatment of NAS which also will
reduce the morbidity and mortality rate after OLT. This will also have an
impact on cost-effectivity of OLT since fewer investigations and interventions
(abdominal ultrasounds, magnetic resonance cholangiography (MRCP), endoscopic
treatments such as endoscopic retrograde cholangio- en pancreaticography (ERCP)
and percutaneous transhepatic cholangiography (PTC)) will have to be performed
to diagnose and treat NAS.

The primary objective of the current study is to perform a prospective
double-blinded randomized controlled trial, investigating the effect of adding
t-PA to the UW preservation fluid, injected under high pressure during the
procedure of donation after cardiac death (DCD), on the incidence of NAS.
Secondary objectives are impact on ASAT and ALAT peak in the first week after
OLT, side effects, remnants of t-PA or its activity after OLT, patient and
graft survival, and cost-effectiveness (including admissions and interventions)
All three liver transplantation units (LUMC, UMCG, EMCR) in the Netherlands
will participate in this prospective study, as well as all Dutch centers where
procurement of donors takes place.
Tissue-type plasminogen activator (t-PA or PLAT) is a protein involved in the
breakdown of blood clots, also known as thrombolysis. Tissue plasminogen
activator is a naturally-occurring enzyme, manufactured with DNA recombinant
technology. The enzyme binds to fibrin-bound plasminogen at the site of a clot,
thus converting plasminogen to plasmin. Plasmin digests the fibrin strands of
the clot and restores perfusion to the occluded artery. t-PA is widely used in
clinical setting for the treatment of various indications such as pulmonary
embolism, myocardial infarction, and stroke. Clot lysis often occurs within
60-90 minutes and the effective duration is * hour (80% cleared in 10 minutes).
In the current study we hypothesize that t-PA will help dissolve microthrombi
in the microcirculation of the peri-biliary plexus. This helps to preserve
bile duct integrity. t-PA may also reduce ischemia-reperfusion injury to the
liver in general by preserving sinusoidal flow.

Intervention group:

Procurement procedures will be performed according to protocol. The abdominal
cavity will be opened by a midline laparotomy followed by an open cannulation
of the aorta. A human liver weighs approximately 1.5 kg and approximately 1.5
mg of t-PA will be flushed per 100 mg of human liver. This means that a total
of 23 mg is needed for sufficiently flushing the liver. However, it is
estimated that approximately 50% of the fluids will be lost in the abdominal
cavity through the aorta. This would mean that 46 mg of t-PA would be needed
for the procedure.
A pressure bag containing 46mg of t-PA solved in 2 liters of UW preservation
fluid will be flushed through the aorta under a pressure of 200 mmHG (=2.7 m
H20). After procurement the donor liver will be stored on ice and sent to the
recipient transplantation hospital according to the normal procedure.

Risks:

t-PA is known for its fibrinolytic properties. One of the endpoints is
monitoring the amount of blood loss per-operatively.Previous research has shown
that there is no significant difference in clotting times and bleeding in use
of t-PA in liver transplants.
In clinical practice, t-PA used in Cerebro Vascular Disorders (CVA) and cardiac
ischemia. The quantities which are used in these clinical settings are much
higher than the amount used in this study. In addition, t-PA directly
administered systemically for the above mentioned disorders, the risk of
hemorrhage appears to be very low. However, theoretically, the use of t-PA
might induce a prolonged bleeding time. For this the total blood loss will be
registered during transplantation.To monitor the amount of blood loss due to an
increased activity of fibrinolysis, thrombo-elastography (TEG) will be used.
TEG is used to evaluate the viscoelastic properties of clot formation. In the
case of a(n) (excess), bleeding due to increased fibrinolytic activity
per-operatively, measurements such as administration of transexamic acid
(Cyklokapron) 1000mg/50ml NaCl 0.9% in 15 minutes can be taken.

Burdens:

In the current setting of post-transplantation care, patients are often seen in
the outpatient clinic of the Gastroenterology and Hepatology department for
frequent evaluation of the liver function. According to standard protocol blood
is drawn from patients at each visit to the outpatient clinic in order to
evaluate liver function. In the current study additional tubes of blood will be
drawn from patients during these moments at which blood is drawn for protocol.
One of the major advantages is that no additional venepuncture procedure will
be necessary. Another advantage is that patients will not be requested for
extra visits to the outpatient clinic.
Since not all NAS cause symptoms such as fever or abdominal pain, a MRCP will
be performed at one year follow-up. Patients will be requested to visit the
hospital one time for this diagnostic procedure. MRCP is a non-invasive
diagnostic procedure. The procedure will take approximatley 45 minutes.