The liver is the biggest intestinal organ and plays a central role in the homeostasis of different physiological systems including nutrition and drug metabolism, the synthesis of plasma proteins and haemostatic factors, as well as the elimination of different endogenous and exogenous substances. Although the liver contributes with only 3% to total body weight, given its major role in homeostasis and high energy consumption, it receives 25% of total cardiac output (CO). Two vessels contribute to the perfusion of the liver. The majority (70%) of the hepatic perfusion is provided by the portal vein, which contributes 50% of the organ’s oxygen demand. The other 50% is provided by the hepatic artery, which makes up around 30% of total liver perfusion. Hepatic arterial blood flow is mainly dependent on the organ’s metabolic demands and controlled via autoregulatory mechanisms, whereas blood supply through the portal vein depends on the perfusion throughout the whole gastrointestinal tract and the spleen. This unique, dual perfusion system provides constant perfusion rates and oxygen supply, which is crucial for adequate liver function. These high oxygen demands are reflected in a hepatic vein saturation of almost 30%.
The liver is also unique in its ability of regeneration, which allows the performance of major surgery including, amongst others, extended resections of liver tumours, living donations and so on. Many patients have normal liver function parameters when they present for liver surgery, especially when the reason for resection is metastasis or a benign liver tumour. The most common causes of liver resections are the hepatocellular carcinoma (HCC) and the cholangiocellular carcinoma (CCC). Hepatocellular carcinoma (HCC) often develops in patients with underlying liver cirrhosis; many of these patients show signs of chronic liver dysfunction (CLD).
As explained previously, the liver plays a central role in a great deal of physiological systems. Therefore, in case of chronic liver dysfunction (CLD) or liver failure, several effects on other organ systems have to be expected. Consequently liver resections and bile duct surgery as having a high risk for perioperative cardiac events, with an estimated 30-day cardiac event rate (cardiac death and myocardial infarction) of more than 5%. Patients undergoing liver surgery pose a significant challenge to treating physicians in the perioperative period. Due to the improvement of surgical techniques, the “liver patient” is becoming more and more complex, confronting surgeons, anaesthetists and intensive care personnel with difficult intra- and postoperative courses, and considerable multiorgan disorders. The cornerstones of an optimal management are careful selection of the patients, appropriate monitoring and protection of the liver and other vital organs.