DISCUSSION
HP for FET is constantly evolving through the years ever since the first
device - ‘Essen I prosthesis’ (2005) (1). Given the success of
Evita-open-plus across the globe, researchers have developed the next
generation HP: Evita-open-NEO. The new generation prosthesis is
available in three variations, making it suitable to be implanted in
zone 0 to 3, and the supraaortic-arch-vessels can be reimplanted
individually or en-bloc. This provides a wide range of applicablity for
the surgeons emcomprising different pathological situations. The low
profile delivery system and a shapeable shaft, is atraumatic and helps
in precise deployment (2).
Evita-open-NEO prostheses are not impregnated with gelatin or collagen,
hence some discrete oozing through pores of the tightly woven polyester
during heparinization can be expected but easily controlled by sump
suction.
This oozing is self-limiting and stops once the protamine is
administered after weaning of cardiopulmonary bypass (CPB) supported by
packing the mediastinum with sponges and towels for 10-15 minutes. Blood
collected in mediastinum can be efficiently managed with cell saver. In
patients who undergo FET under prolonged deep hypothermic circulatory
arrest, coagulopathy has to be considered. In that case, graft oozing
through the pores may appear excessive but can be quickly fixed by TGCM
during and after CPB (Video 1).
Thromboelastometry provides important information about hemostasis,
particularly in regard to fibrin polymerization and platelet function,
and can already be initiated at crossclamp release. Accordingly,
cryoprecipitate can timely be prepared if fibrinogen concentrate is not
available. Adequate fibrin and platelet contribution to the clot
firmness are essential for the formation of an internal fibrin layer to
seal the prosthesis (3). In contrast, low fibrinogen levels
(<2-4 g/L) have been shown to be an independent risk-factor
for severe bleeding, 24-hour mortality, in-hospital mortality, and
neurological complications in patients with acute AD (3- 6).
The algorithm of TGCM for major aortic surgery is by using a trigger of
EXTEM A5 <40 mm and FIBTEM A5 <12 mm, and a target
of EXTEM A5 ≥40 mm and FIBTEM A5 ≥15 mm for fibrinogen substitution (3,
7). Notably, this can only be achieved by administering fibrinogen
concentrate (20 g /l) or cryoprecipitate (8-16 g/l) but not by FFP
containing only 2g fibrinogen/l) (8). Some patients require platelet
transfusion and/or prothrombin complex concentrate administration in
addition.
In contrast, Czerny and colleagues recently reported devastating oozing
and severe blood loss in 3 patients after implantation of E-vita open
NEO (9). Those patients, characterized by continuous acetylic acid
monotherapy preoperatively, obviously mandated differentiated
coagulation management during and after CPB. Here, FFP transfusion with
its low fibrinogen concentration is certainly not appropriate and may
cause pulmonary complications, right ventricular failure, and increased
RBC transfusion (10, 12).