4.1: Graft Oozing
It is worth emphasising that oozing from the graft portion of E-Vita Open NEO is not a phenomenon unique to Ho et al. Rather, it is a well-documented complication associated with use of the device that surgeons, as pointed out by Ho et al., should expect rather than simply be aware of.8,10 In their study detailing initial experiences with E-Vita Open NEO in the Asia-Pacific region, Jakob et al. highlight a case of graft oozing during FET surgery in a 54-year-old male with ascending aortic aneurysm and type B aortic dissection.10 Oozing from the polyester segment persisted following protamine administration and CPB weaning, and eventually required liberal amounts of Surgicel® FibrillarTM (Johnson and Johnson N.V., Belgium) with pressurised packing for several minutes to be controlled.10 Further, Czerny et al. also highlight three cases of profound graft oozing during E-Vita Open NEO implantation, following CPB weaning and protamine administration.9 Routine substitution of plasmatic and cellular coagulation, guided by thromboelastometry, was unsuccessful in controlling graft oozing. One patient required 23U of red blood cells, 28U of fresh frozen plasma, and 16U of thrombocytes within the first 24 hours postoperatively. All three patients had complicated postoperative courses, involving low cardiac output necessitating inotropes, haemodialysis, multi-organ failure, paraplegia, and death.9 A recent systematic review by Bashir et al. also concluded that reports on post-FET coagulopathy were associated with substantially higher heterogeneity in E-Vita Open NEO® and Cronus® compared to Thoraflex® and Frozenix®.12 It is possible that reports on perioperative coagulopathy associated with E-Vita Open NEO® would encompass cases wherein graft oozing lead to a need for increased blood product transfusion, or reintervention to correct bleeding.12
The risk of graft oozing in FET for TAR is likely governed by surgical and non-surgical factors. Modern surgical techniques, low graft porosity, advanced suture material, and anastomotic adjuncts used to support suture lines (e.g., BioGlue) all serve to greatly diminish the likelihood of graft oozing. In contrast, the lack of gelatine and collagen impregnation in E-Vita Open NEO has likely re-introduced the risk of graft oozing due to massively increased graft porosity.9 This is unsurprising considering there have hitherto been no reports of graft oozing from market equivalents (i.e. Thoraflex®, Frozenix®, and Cronus®) that do feature gelatine and collagen impregnation. Non-surgical factors, such as routine use of thromboelastometry, allow continued monitoring of the patient’s intraoperative thrombotic state and enables rapid intervention against aberrant haemodynamics or coagulopathy.9Interestingly, Ho et al. point out that graft oozing mostly occurred in patients presenting with abnormal TEM findings.8 It is unclear why E-Vita Open NEO® is not impregnated with collagen or gelatine, especially considering this seems to be a standard feature in similar commercially available devices, and that abnormal thrombotic states are not rare pre-operative characteristics in patients undergoing aortic surgery.