S . P . Butt et al .: J Extra Corpor Technol 2024 , 56 , 77 – 81 79
Figure 3 . Illustration of jugular ( a ) and femoral ( b ) percutaneous cannulation .
the procedures . Temperature regulation is managed through the Sorin CSC 14 Cardioplegia heat exchanger set ( Livanova , London , United Kingdom ). The access and return cannulas utilized are also coated with Bioline ( HLS ), with the preferred choice being 15 Fr femoral aortic for access and return , as the required flow typically falls between 1.8 and 2.2 L / min .
Moreover , while a hemoconcentrator can be incorporated into the VV bypass circuit if necessary , we opt not to include any additional devices in the circuit to minimize the risk of circuit air embolism . Instead , if required , we utilize continuous renal replacement therapy ( CRRT ) intraoperatively as a separate measure .
In terms of anticoagulation , our protocol entails administering a standard pre-VV bypass dose of 3000 units of heparin for all patients . Additionally , we prepare two bags of 500 mL of normal saline , with a concentration of 2 units per mL . These bags are connected to both the access and return cannulas , with infusion rates maintained at 1 – 2 mL per minute .
Cannulation
Cannulation plays a pivotal role in the establishment of VVB . An 18G cannula is placed in the femoral vein for access by Anaesthesiologist . The drainage cannula is then inserted into the femoral vein by the surgeon , facilitating the drainage of blood below the infrahepatic inferior vena cava ( IVC ). The blood is returned to a 15Fr cannula placed in the internal jugular vein percutaneously by the Anesthesiologist via the bypass circuit as illustrated in Figure 3 . If a portal bypass is necessary , a second drainage cannula is inserted into the portal vein and connected to the main VVB circuit through a dedicated drainage line . To ensure optimal functionality , it ’ s important to use high-volume , low-pressure inflow and outflow cannulas .
Catheter access can be achieved either percutaneously or , on rare occasions , through surgical cutdown . Surgeon performs the femoral or Portal cannulation and Anesthesiologists typically perform percutaneous internal jugular venous cannulation [ 5 , 6 ].
Discussion
Several studies have evaluated the use of the venovenous / portal ( VVP ) bypass technique in LT and found positive outcomes . The studies demonstrated that VVP bypass can offer benefits such as hemodynamic stability , prolonged surgical time , and improved outcomes for patients with renal disease . These findings support the reconsideration of the extracorporeal VVP bypass as a means to minimize complications and improve patient outcomes in LT procedures [ 2 , 3 ].
VVB provides numerous advantages , such as sustaining stable hemodynamics during the transplant procedure and lessening the likelihood of complications like cardiac arrhythmias , pulmonary hypertension , and right ventricular dysfunction . Additionally , it enhances recipient safety by lowering the chances of surgical complications .
The efficacy of the venovenous / portal ( VVP ) bypass technique in LT was assessed through an analysis of 163 consecutive LTs conducted at a center since the inception of its liver transplant program in 2010 . The average operative time was 269 min with a warm ischemic time of 43 min . Median transfusion requirements for packed cells and plasma were 7 and 14 units , respectively . No intraoperative deaths were reported , and 30-day mortality stood at 3 %, with no severe bypassinduced complications observed . The discussion emphasizes the significance of stringent safety measures during the establishment of new LT programs , highlighting the precise control offered by the VVP bypass device over surgical and anesthesiological management , particularly beneficial when utilizing marginal grafts . This approach aims to minimize volume overload , reduce vasopressor usage , mitigate myocardial injury , and improve peripheral blood circulation . Consequently , based on the findings , there ’ s a suggestion for a reconsideration of the extracorporeal VVP bypass in LT [ 7 ].
In a comparative study , researchers investigated the impact of VVB during liver resections with prolonged hepatic vascular exclusion and hypothermic liver perfusion . They found that VVB use led to significantly reduced intraoperative blood loss ( p = 0.010 ) and fewer postoperative respiratory complications ( 15 % in patients with venovenous bypass VVB + vs . 64 % in patients without venovenous bypass VVB� , p = 0.012 ). Despite VVB + patients experiencing longer operative times ( 460 vs . 375 min , p = 0.023 ), there were no significant differences in postoperative mortality or major morbidity rates between the VVB + and VVB� groups . These results underscore the potential benefits of VVB in enhancing surgical outcomes during complex liver resections with prolonged hepatic vascular exclusion and hypothermic liver perfusion , emphasizing its recommendation in such cases [ 8 ].