Hepatic and Systemic Hemodynamic Modeling During Liver Surgery

"The surgical management of liver cancer is becoming increasingly complex, with resections often extensive, iterative and on pathological liver (cirrhosis or multi-chemotherapies). This attitude is made possible by a better selection and perioperative management of patients, as well as by the regenerative capacity of the liver. However, even if extensive resections are routinely performed, the limitation remains the risk of postoperative liver failure (PLF), especially in patients with chronic liver disease. Despite numerous known risk factors, some of which are avoidable, PLF and/or postoperative liver decompensation (ascites) remain frequent complications (incidence > 5%) and PLF remains one of the main causes of postoperative death.

The difficulty lies finally in the choice of a treatment adapted to the carcinological needs, with the balance between what is technically feasible and what will be tolerated on the functional and metabolic level. This balance is founded on a surgical evaluation based on objective elements (volumetry and biological tests in particular) and on the surgeon's experience. This estimate is imperfect, the proof being the mortality at 3 months after hepatectomies which is still high, 5 to 7% if considering all types of hepatectomies. It is obviously possible to further improve these results and the computer tool must find its place in the medical-surgical algorithm. It is already known that virtual (preoperative) 3D hepatic reconstructions are an important aid and lead to a decrease in postoperative morbidity and mortality but hemodynamic simulation could also be used as a decision-making tool.

After hepatectomy, the imperative to maintain a satisfactory liver function is to preserve a sufficient residual parenchymal volume associated with an intrahepatic blood supply (inflow) adapted to the volume of the liver and to the splanchnic flow, and a sufficient effluent (outflow) to avoid any intrahepatic congestion. The post-resection portocaval gradient is one of the most relevant reflections of the hemodynamic conditions of a liver and the risk of PLF but it is only available intraoperatively, after the surgical procedure has been performed, and therefore cannot be used as a tool for selecting candidates for surgery. Currently, there are several decision algorithms to guide the surgical management of a patient, based on preoperative clinical or biological data (platelets, bilirubin, indocyanine green clearance, ascites, esophageal varices...). The pre-resection portocaval gradient ≥10 mmHg, measured or estimated non-invasively, allows selection of high-risk patients, but remains not very sensitive and specific, and does not prevent the occurrence of any PLF.

It therefore remains very difficult for a given patient (especially cirrhotic) to accurately predict the risk of postoperative decompensation and some patients may sometimes be undertreated for fear of decompensation. In these patients, it is therefore a loss of chance.

In liver transplantation, the same need for adequacy between the vascular bed and the portal flow is necessary, especially in case of a small graft or partial liver. In case of mismatch, a small for size syndrome, i.e. portal hypertension (PHT) and organ failure (PLF equivalent) may occur, thus endangering the graft and the patient. As with partial hepatectomies, prediction of the post-transplant portocaval gradient would help avoid small-for-size syndrome by fine-tuning the maximum mass portal flow not to be exceeded. Thus, a better matching of the donor/recipient pair could be proposed, especially for living donor or auxiliary transplants.