**3.2. Anesthetic considerations**

[22]. In this classification, the liver is divided into first, second and third order divisions based on internal anatomy rather than surface landmarks. First order division splits the liver into a right and left hemiliver along Cantlie's line, a plane extending from the middle of the gallbladder fossa to the center of the inferior vena cava. Second order divisions split the hemilivers into two respective sections or sectors, the medial and lateral sections/sectors on the left and anterior and posterior sections/sectors on the right. The third order division divides each section/sector into two segments, constituting the 9 individual hepatic segments defined by Couinaud. In general, each segment has a unique vascular inflow, outflow and biliary duct

The proper hepatic artery and portal vein bifurcate prior to the hilum of the liver and form the right and left hepatic artery and portal vein which supply the right and left hemiliver. Joined by the biliary duct, the portal triad generally runs centrally within hepatic segments. The right hepatic artery enters the parenchyma soon after branching while the left has a longer extrahepatic course. In contrast, the three hepatic veins run between section/sectors in three portal scissurae. The right hepatic vein drains directly into the inferior vena cava (IVC) while the middle and left hepatic veins often form a common trunk prior to entering the IVC.

**Figure 1.** Schematic of liver anatomy separating the parenchyma into 9 anatomic segments. Each segment has unique blood supply and biliary drainage. Source: Cho, Fong. Hepatic Resection. In: Ashley SW, editor. Scientific American

Surgery. Hamilton: Decker. 7th ed; 2014. pp. 1094–1114.

enabling segments to be removed without damage to other segments.

62 Liver Cancer

Some important perioperative anesthetic considerations should be accounted for to increase the safety of hepatectomy. To minimize the possibility of major intraoperative hemorrhage, the central venous pressure should be maintained at less than 5 mmHg to reduce the intrahepatic venous pressure. This is achieved using various anesthetic maneuvers and agents such as IVF restriction, and administration of isoflurane, fentanyl, mannitol, and cisatricurium. For open hepatectomy, the patient can be placed in slight reverse Trendelenburg position if pressures allow and switched to Trendelenburg position if there is significant hemorrhage with hemodynamic derangement to increase cardiac output and maintain end-organ perfusion. For laparoscopic/robotic hepatectomy, the patient is placed in reverse Trendelenburg position for a caudal approach which improves visualization of the vasculature, and the pneumoperitoneum creates a tamponade effect on the hepatic veins, which aids in limiting hemorrhage. Adequate vascular access should be obtained using large bore IVs, with appropriate invasive hemodynamic monitoring using A-line. Blood products should be readily available and resuscitation of operative blood loss should be with an appropriate combination of crystalloid, albumin and blood product as necessary. End-tidal CO<sup>2</sup> is measured to monitor for CO<sup>2</sup> embolism in the laparoscopic/robotic approach.
