The non-selective inflow occlusion via pedicle clamping is the classical form of vascular control during hepatic resections. The Pringle maneuver is the oldest form of vascular control [3] and also the fastest and easiest to perform, if immediate control of parenchymal bleeding is necessary. The hepatoduodenal ligament is freed from adhesions, in order to avoid injury to the inferior vena cava (IVC) or the duodenum when placing a vascular clamp. Afterwards, the hepatoduodenal ligament is encircled as a whole and a strong vessel loop is placed as a tourniquet, which is kept in place and can be closed permanently or intermittently during phases of parenchymal dissection. The tourniquet (or a vascular clamp) is tightened up to the point where the distal pulse of the hepatic artery disappears. If an aberrant left hepatic artery originates from the gastric artery, it will not be occluded by the pedicle clamping and needs to be occluded separately, if necessary. Pedicle clamping results in a modest cardiac index decrease (due to decreased venous return) and an increase in systemic vascular resistance and mean arterial pressure. In general, the Pringle maneuver is well tolerated, as caval flow is not impaired. After the lowering of the hilar plate maneuver, the pedicle clamping can also be performed separately for the left and right pedicle (Fig. 12.1) and also selectively for the right anterior or posterior pedicle (Fig. 12.2). The Pringle maneuver can be used continuously or intermittently, and also after a short phase of ischemic pre-conditioning to the liver. Numerous randomized controlled trials and meta-analyses have looked at the outcome and best implementation of the Pringle maneuver [25–27]. A recent meta-analysis including eight randomized controlled trials has investigated overall morbidity and mortality, cardiopulmonary and hepatic morbidity, blood loss, transfusion rates, and alanine aminotransferase (ALT) levels in patients undergoing liver resections with or without portal triad clamping. No differences between intermittent portal triad clamping and no clamping were found with regard to all endpoints. In accordance with these findings, an analysis of patients receiving continuous portal triad clamping with- or without ischemic preconditioning did not reveal any differences with respect to the above mentioned endpoints, except for ALT levels, which were lower in the ischemic preconditioning group [26]. As a conclusion from these analyses, routine use of portal triad clamping cannot be recommended, as it does not alter the intraoperative blood loss or outcome (morbidity and mortality) after liver surgery. Nonetheless, it has its place in liver surgery for individual select cases and/or resection techniques. For example, routine use of the Pringle maneuver can be beneficial during parenchymal resection, using a stapler device, as mean resection time is less than 10 min. No ischemic injury to the liver will occur during this short time, and blood loss can be decreased [19]. With regard to clamping time, it appears safe to use total clamping times of up to 60–90 min, whereas intermittent reperfusion is probably helpful in avoiding ischemic reperfusion injury, at least for a clamping time of more than 20 min: An intermittent portal triad clamping of up to 60 min is probably also safe in patients with compensated cirrhosis, although cirrhosis is known to increase the sensitivity for ischemia reperfusion injury [28–33].

Total- and selective hepatic vascular exclusion should not be routinely recommended for liver resection procedures. Recent meta-analyses have shown no benefit of hepatic vascular exclusion for perioperative outcome in liver resections [26, 27]. In addition to liver inflow control using portal triad clamping, hepatic vascular exclusion has been proposed to further decrease hemorrhage in major hepatic resections originating from the hepatic veins. Total vascular occlusion for liver surgery combines portal triad clamping with supra- and infrahepatic clamping of the IVC. Selective vascular occlusion is a combination of portal triad clamping with selective hepatic venous clamping, which preserves caval flow and causes less hemodynamic instability. A recent meta-analysis including four randomized controlled trials has compared total- and selective hepatic vascular occlusion with conventional portal triad clamping for liver resections. No differences with regard to outcome, defined as morbidity and mortality, were observed between the portal triad clamping group and hepatic vascular occlusion. However, total hepatic vascular occlusion increased morbidity compared to portal triad clamping alone. Significant differences in reported blood loss were not observed, either [27]. In summary, hepatic vascular occlusion achieved by the above mentioned techniques should be reserved for extended central resections, such as resections involving the vena cava and/or main hepatic veins.

Hypothermic ante-situm or ex-situ resections with total vascular exclusion can be the only possible options to resect central liver lesions with caval involvement [15]. Infiltration of the hepatocaval confluence has been considered a contraindication for liver resections, as achieving tumor-free margins in this area was regarded as technically impossible (Fig. 12.3a, b). However, several techniques, including ante-situm and ex-situ resection techniques, have been introduced to overcome this technical problem, and are discussed in detail elsewhere in this book. These techniques use a total vascular exclusion of the liver, combined with cold perfusion with organ preservation fluid, similar to the back-table preparation of liver transplantation as a common concept [15, 34, 35]. The hypothermic methods allow safer time frames for resection and better access, in comparison to total vascular occlusion without cold-perfusion resulting in warm ischemia and ischemia reperfusion injury, which is not well tolerated by the liver if it exceeds 60 min [36–39]. In general, these types of surgeries should only be performed in experienced high-volume centers and for selected patients, as reported morbidity is high, with mortality rates reported between 9 and 33%, especially for ex-situ resections [15, 37]. It is noteworthy that 5-year survival rates after extended liver resections including caval resections have been reported as high as 33% [37, 40].

Bleeding from the hepatic venous system and the sinusoids during parenchymal dissection is directly related to the pressure within the sinusoids in the liver parenchyma. This pressure is directly related to the hepatic venous pressure, which in turn is dependent on the central venous pressure. While clamping the hepatic pedicle for bleeding control during parenchymal transection (Pringle maneuver), bleeding from the sinusoidal system will persist, as the hepatic venous system remains open and patent. A low central venous pressure (CVP) during parenchymal transection phase will result in a low hepatic venous pressure and subsequently less intraoperative bleeding. Achieving a low central venous pressure is not always possible by anesthesiological interventions (fluid restriction, reverse Trendelenburg position, etc.; also see next paragraph), and thus clamping of the IVC has been suggested and evaluated as an alternative approach to reduce hepatic venous pressure and intraoperative bleeding during parenchymal transection (Fig. 12.4). A recent randomized controlled trial has evaluated the effectiveness and safety of IVC clamping for reduction of central venous pressure and bleeding control during elective hepatic resections. Patients were compared to the standard regime for lowering the CVP, namely anesthesiological means such as fluid restriction. IVC clamping resulted in reduced total intraoperative blood loss, mainly because it significantly lowered the blood loss during the parenchymal transection phase [41]. Mortality and morbidity rates were similar compared to the control group, while there was a significantly increased risk of pulmonary air embolism in the IVC clamping group. Due to hemodynamic instability, IVC clamping, as well as lowering the CVP with anesthesiological means, such as fluid restriction and/or reverse Trendelenburg position, is not possible in 10–20% of the patients [24, 41]. Close monitoring and interaction with the anesthesiological team is mandatory for both techniques.

The group of Jones et al. has shown that a central venous pressure of less than 5 cm H₂O during liver transection results in a significantly decreased blood loss and transfusion requirement in liver surgery [42]. Certain non-invasive techniques, such as peri- and intraoperative fluid restriction, can lower the CVP during elective liver surgery. CVP lowering increases the risk for air emboli, and experienced anesthesiological care is necessary in order to maintain the central venous pressure between 2 and 5 cm H₂O during the critical surgical phase. Additional options of lowering the central venous pressure, such as IVC clamping or table positioning (reverse Trendelenburg position), can be used and are discussed above [41].

Further anesthesiological and pharmacological methods to decrease the intraoperative blood loss have been evaluated intensely, such as preoperative haemodilution, autologous blood donation, and transfusion and the use of several drugs or anesthesiological regimes (volatile narcotics) in order to prevent ischemia reperfusion injury [22, 43–45]. At this point of time, these methods/techniques are clinically not important. Further trials are necessary for evaluation of these interventions, as there is no current evidence strong enough to support the routine use of any pharmacological or peri-operative intervention in order to reduce intraoperative blood loss during liver surgery.

In theory, most techniques of vascular control can technically be achieved using minimally invasive surgery. Currently, open surgery is considered to be the safest choice for major hepatic and extended resections. The general advantages of laparoscopic surgery have been widely evaluated in the past. These include smaller incisions, faster recovery, less pain, shorter in-hospital stay, less postoperative hernia, less wound infections, and less intraoperative blood loss (due to intra-abdominal pressure and higher magnification) [46–49]. Recently, the second international consensus conference for laparoscopic liver surgery has defined laparoscopic liver resections for minor resections as standard of care, while major laparoscopic liver resections were regarded as innovative procedures, which are still in the experimental phase [50]. Therefore, these procedures should only be performed at high-volume, specialized liver surgery centers, ideally as part of clinical trials.