In the past decades, a better understanding of liver anatomy, improved surgical techniques, proper perioperative management and improved anesthesia have made hepatectomy safe and simple. However, some special sites of surgery, such as: tumors close to or infiltrating large blood vessels, or enlarged hepatectomy, may have fatal intraoperative hemorrhage. And bleeding accompanied by blood transfusion can increase the morbidity and mortality of postoperative complications, especially in patients with combined cirrhosis. poon et al. concluded that postoperative blood transfusion in patients with hepatocellular carcinoma can increase the chance of tumor recurrence after surgery, even if it is a small amount of blood transfusion . And patients with hepatocellular carcinoma may have increased incidence of rectal metastasis with either blood bank blood or autologous blood transfusion, suggesting that blood transfusion may lead to non-specific immune suppression related. Many clinical data show that more than 50% of hemihepatectomies and more than 90% of partial hepatectomies can be performed without blood transfusion . Therefore, it is necessary and possible to reduce blood transfusions during hepatectomy. The reduction of blood transfusion must be predicated on the reduction of intraoperative bleeding. For example: application of techniques such as CUSA (ultrasound suction knife) and thermal coagulation during hepatectomy; intraoperative reduction of central venous pressure (CVP); temporary blockade of incoming hepatic blood flow with or without control of outgoing hepatic blood flow, etc.
Although hepatectomy does not necessarily require blocking hepatic blood flow, effective control of hepatic blood flow maintains a relatively bloodless surgical environment, reduces bleeding, and shortens operative time. This article evaluates the currently used methods of hepatic blood flow blockade.
I. Pringle method
It has been nearly 100 years since Pringle began to apply temporary blockade of the incoming hepatic blood flow to cut the liver in 1908. It is one of the most widely used measures to control bleeding during hepatic resection. Man et al. compared the Pringle method with the non-blood flow blocking method, and the former was superior to the latter . In 3857 patients undergoing hepatectomy under Pringle block at Tongji Hospital of Huazhong University of Science and Technology, intraoperative bleeding ≥1000 ml was found in 6.0% of patients, and 14.1% of patients were not transfused. However, the biggest disadvantage of this method is the significant thermal ischemic damage to the liver, which is limited by time. It is generally considered that the safe time limit for continuous blockade by this method is 60 min . In their study, they demonstrated that even in cirrhosis, the total ischemic time was 90 min. without an increase in mortality and postoperative complication rates. On the other hand, the amount of blood transfusion directly affects the morbidity and mortality rate, especially in patients with cirrhosis. Blood transfusion increases the likelihood of postoperative liver failure [8].
On the other hand, intraoperative gas embolism or hepatic venous reflux bleeding should be noted because of the lack of blockage of blood flow out of the liver. Gas embolism can occur during hepatic parenchymal transection. It is especially likely to occur when the central venous pressure (CVP) is lowered to prevent hepatic vein bleeding. If there is gas diffusion into the circulatory system, the patient should be placed in the 15 degree trendelenburg position in order to minimize the consequences of air embolism. The Pringle method should be used with caution as it does not stop hepatic venous regurgitation bleeding. Reducing hepatic vein bleeding can be accomplished by reducing CVP or by completely blocking blood flow to the cut-off site before applying the method. smyrniotis et al. compared the continuous Pringle method with selective total hepatic flow blockade, and plasma IL-6 and IL-8 were significantly elevated in the Pringle group, which had a protective effect on the liver.
When Pringle method is used, continuous blockade or intermittent blockade can be performed. Continuous blockade has been performed for up to 127 min in normal livers and 100 min in livers with combined cirrhosis, without adverse effects. However, when Belghiti et al. studied the intermittent Pringle method (15/5, blocked for 15 min, then not blocked for 5 min, repeated) and the continuous Pringle method, they found no difference in total blood loss or transfusion volume between the two, but severe liver failure occurred in four cases after application of the continuous Pringle method. man et al. studied the intermittent Pringle method (20/5) compared with no flow blocking at all and found significantly less total bleeding, less blood transfusion, and shorter time to liver resection .Kang et al. similarly demonstrated the effectiveness of intermittent portal blocking in animal experiments. Petrowsky et al. retrospectively compared intermittent portal block to continuous portal block with ischemic preconditioning for major hepatectomy in a randomized controlled trial and concluded that both were equally effective in protecting against postoperative liver injury when major hepatectomy was performed in non-cirrhotic patients. However, continuous portal block with ischemic preconditioning is associated with minimal bleeding and shorter liver resection time.
In conclusion, Pringle method is simple and easy to perform, and is a relatively effective method of blood flow block. However, it is not suitable for surgery in which the tumor invades the hepatic portal or vena cava. It should be used with caution in patients with right heart failure or pulmonary hypertension causing elevated CVP, resulting in hepatic venous reflux bleeding; or patients with potential risk of gas embolism, or the whole liver flow blocking method can be used.
II. Semi-hepatic flow blocking method
Although the Pringle method is effective in most surgical procedures, according to the traditional view, the safe time limit for blocking blood flow to the liver at room temperature is 15-20 min, especially in combined hepatic resection with hepatic sclerosis, the time should be controlled within 15 min, such as exceeding this time limit may lead to hepatic necrosis and liver failure. In order to reduce the intraoperative ischemic damage to the non-cut liver tissue, Makuuchi proposed the hemihepatic blood flow block method in 1987. The hemihepatic block preserves the normal blood flow to the liver in the contralateral half of the liver, creating the conditions for a comfortable operation with less intraoperative bleeding and less postoperative liver function damage, which is beneficial for patients with hepatocellular carcinoma combined with cirrhosis .
The main advantage of this method is that it avoids ischemia in the healthy side of the liver, prevents stasis in the portal system, and maintains hemodynamic stability even when the liver is resected. This blood flow block can make the resection margins clearly defined and can be applied flexibly intraoperatively. For example, when the lesion straddles the left and right hepatic halves, the right vascular branch is blocked when the right side of the lesion is resected, and then the left branch is blocked when the left side is resected.
The main disadvantage is that bleeding in the hepatic section can sometimes be very severe due to the presence of a traffic branch between the unblocked hepatic half and the blocked side. Reducing bleeding can be accomplished by reducing the CVP or blocking the common hepatic artery while blocking the unilateral portal branch, or by using the Pringle method instead. On the other hand, this method is more difficult than the Pringle method, and requires the operator to be skilled in hepatic portal anatomy, otherwise the posterior wall of portal vein, middle hepatic vein branches, caudate lobe vessels and bile ducts are easily damaged.
Wu et al. concluded that this method can also be used for patients with cirrhosis of Child B and Child C grade.
In conclusion, hemihepatic blockade blood flow block is particularly suitable for patients with cirrhosis. However, it cannot be used in cases of tumor infiltration of the hepatic portal; severe adhesions around the hepatoduodenum (caused by surgery or chemoembolization); and anatomical variants of the portal vein or hepatic artery.
Hepatic segmental flow blockade
For hepatic segmental flow block, a balloon catheter is inserted into the portal vein of the hepatic segment where the cancer is located under ultrasound guidance, followed by filling the balloon with saline to make the balloon dilate and block the corresponding branch. The portal tract is injected with methylene blue to identify the segment more clearly against the background of stained liver parenchyma. Hepatic segmentation or combined hepatic segment resection can be performed precisely. Jinrui Au et al. concluded that this method is superior to hemihepatic block. Also this block can be continuous or intermittent.
Hepatic segmental flow block can be used for resection of small hepatocellular carcinoma in the periphery of the liver in combination with cirrhosis. It minimizes ischemic damage to the diseased liver and allows for precise resection of the segment to be removed. This approach allows resection of tumors growing along the branches of the portal vein, thus theoretically blocking tumor progression, as the portal route is the main route of hepatocellular carcinoma dissemination.
IV. Incoming hepatic blood flow blocking method by preserving half of the hepatic artery blood supply
Since 70-75% of the normal liver blood supply comes from the portal vein, while 40-60% of the oxygen supply comes from arterial blood. Therefore, based on the different blood flow distribution characteristics between portal vein and hepatic artery and the difference in oxygen content, Dai Chao-Liu et al. proposed an inflow blocking method that preserves half of the hepatic artery blood supply. During the operation, the intrinsic hepatic artery was exposed, and the left and right hepatic arteries were freed upward. For the right hemihepatic block, the catheter is tightened around the portal vein, common bile duct and right hepatic artery. For left hepatic hemiblock, the catheter is tightened around the portal vein, common bile duct, and left hepatic artery. This preserves the arterial blood supply to the healthy hepatic hemisphere during surgery. This effectively reduces intraoperative bleeding and ensures the oxygen demand of the healthy side. It has been shown that the hepatic artery has a high pressure gradient and can adequately perfuse every corner of the hepatic vascular network, whereas the portal vein cannot supply oxygen to all parts of the liver. When the portal vein was clamped, the oxygen consumption of the liver remained at the pre-clamping level, indicating that the hepatic artery alone can provide sufficient oxygen demand to the liver. 2006, the author used this method to perform hepatic resection in 19 patients with hepatocellular carcinoma and hepatic hemangioma, and obtained good results with less intraoperative bleeding and mild postoperative damage to the patient’s liver function. Mu Zinguo et al. reported that this method is superior to whole liver into liver blood flow blockage, which is important for the prevention and treatment of postoperative liver failure. This method is a commendable method because of its simple surgical operation, better intraoperative bleeding control, and avoidance of ischemia and hypoxia in the healthy hemisphere.
V. Whole liver blood flow blocking method
The total hepatic blood flow blocking method is also known as bloodless hepatectomy. It is an effective method to control bleeding and gas embolism during liver resection and severe liver trauma. 1978 Huguet first reported the successful completion of 14 difficult hepatectomies using this method. The sequence of blocking vessels is: abdominal aorta (subdiaphragmatic position), hepatoduodenal ligament, inferior hepatic vena cava and inferior and superior hepatic vena cava. The order of opening is the opposite of blocking. It is important to note that blocking causes temporary hemodynamic changes that some patients cannot tolerate. Therefore, blocking and opening of the vessels should be done gradually. It has been suggested that to determine whether the body can adapt to total hepatic flow block, a short time (5 min) pre-block can be used to determine whether total hepatic flow block can be used by monitoring the kinetics. Michael et al. used total hepatic blockade to perform hepatectomy in 99 patients and concluded that this method could reduce intraoperative blood loss and maintain hemodynamic stability, but the mortality rate was higher in cirrhotic patients with portal hypertension. It is believed that blocking the abdominal aorta causes ischemia and hypoxia in the lower extremities and abdominal viscera, and even spinal cord ischemia, and the acidic metabolites and intestinal endotoxins produced after blocking the opening into the circulation can cause damage to the organism. At the same time, patients with combined cirrhosis often have varices in the posterior abdominal wall, and the free abdominal aorta is prone to bleeding. At present, this method is less applied.
Sixth, simplify the whole liver blood flow block method
Simplified total hepatic block method is also known as modified total hepatic block method. In other words, the hepatoduodenal ligament, the inferior and superior hepatic vena cava and the inferior hepatic vena cava are blocked intraoperatively, but the abdominal aorta is not blocked. This approach shortens the operative time because the abdominal aorta is not blocked. However, the systemic hemodynamic changes are greater without blocking the abdominal aorta. Therefore, high demands are placed on anesthesia techniques. Intraoperative flow blockade leads to a significant reduction in venous return and cardiac output (40-60% reduction), accompanied by an 80% increase in systemic vascular resistance and a 50% increase in heart rate. Patients are defined as intolerant to the method when their cardiac output decreases by more than 50% or their mean arterial pressure decreases by more than 30%. For intolerant patients, complete volume expansion followed by flow blockade is recommended. This is because the reflex of the adrenal cardiovascular system to increase cardiac output is lost in these patients when preload is decreased. The method was applied by Yu Zhengping et al. to 12 patients who underwent hepatectomy at room temperature, and all of them had successful resection of the tumor. intraoperative bleeding was significantly reduced with an average transfusion of 800 ml, and blood pressure fluctuated in the range of 142.5-82.5 mmHg systolic and 75-60 mmHg diastolic before and after blockade. postoperative ALT and AST were significantly increased and returned to normal about one week after surgery. It is believed that this method both simplifies the operation of total liver block and shortens the operation time.
This method is mainly used when the tumor is close to or infiltrates the main hepatic vein or the inferior vena cava. It is also sometimes used when there is a tumor embolus in the inferior vena cava, and this method prevents intraoperative embolus movement. Simplified total hepatic block allows safe reconstruction of the main hepatic vein or inferior vena cava. While Wang Qian et al. performed liver resection by this method in eight patients, they concluded that this method has no advantage in reducing intraoperative bleeding and has a high rate of postoperative complications, and it is appropriate to apply it only selectively in cases where the tumor invades the main hepatic vein, the vena cava, or is accompanied by cancerous emboli in the vena cava [25].
VII. Total hepatic flow blocking method to preserve vena cava patency
In order to avoid the hemodynamic changes caused by blocking the inferior vena cava and abdominal aorta, a total hepatic flow block with preserving the patency of the vena cava is proposed. The advantage of this method is that gas embolism and regurgitant bleeding are avoided without disturbing the vena cava flow, so intraoperative hemodynamic changes are avoided. However, the operation is more complicated than the simplified total hepatic blockade method, and Cherqui et al. concluded that by blocking the first hepatic portal along with the hepatic vein flow, the purpose of controlling the total hepatic flow can be achieved, while avoiding the obstruction of the return blood flow and the decrease of blood pressure due to the inferior vena cava block. The amylase, bilirubin and AST were significantly increased in the total hepatic flow block group. In 10 cases of tumors located in the second hepatic hilar region, Zhou Wei et al. performed hepatectomy with first hepatic hilar + left, middle and right hepatic vein block to maintain inferior vena cava flow, and some patients also underwent short hepatic vein ligation. It is believed that total hepatic flow block hepatectomy without blocking the inferior vena cava can achieve the purpose of bloodless hepatectomy, while avoiding the systemic hemodynamic disturbance caused by inferior vena cava block, which is a more reasonable new technique [28].
VIII. Total hepatic flow blockade under extracorporeal venous diversion
For complex procedures in the portal region of the liver, the application of extracorporeal venous diversion technique has been started this year. The portal and inferior vena cava blood is diverted to the superior vena cava to avoid stasis of the lower part of the trunk and internal organs. Using a biological pump, a diversion catheter is placed in the superior mesenteric vein and the femoral vein, connected by a “Y” connection tube, and then placed in the axillary vein, while blocking the first hepatic portal and the superior and inferior hepatic vena cava. Huguet et al. suggested that this method is suitable for patients who cannot tolerate total hepatic flow blockade in patients with tumor infiltration of the inferior vena cava or major hepatic veins.
IX. Conclusion
The choice of hepatic flow blocking method in liver surgery should be based on the preoperative imaging findings, combined with the patient’s preoperative liver function, the degree of pathological changes and location of lesions in the liver during intraoperative exploration, whether the hepatic veins and inferior vena cava are invaded, the patient’s cardiovascular condition, and the experience and habits of the surgeon and anesthesiologist. For patients without cirrhosis or with mild cirrhosis, Grade A liver function, small tumor, and the patient’s estimated operation time is not long, the Pringle method or the entering hepatic blood flow blocking method that preserves half of the hepatic artery blood supply can be used, which has the advantages of easy operation. For patients with severe cirrhosis, Grade B liver function, large tumor, difficult surgery, and hepatectomy scope above the near half hepatectomy of the enlarged joint hepatic segment, half hepatic flow blocking method or hepatic artery blood supply preserving half hepatic flow blocking method can be chosen, which can ensure the normal blood supply of the healthy side of the liver and prolong the blocking time. For tumor invasion of hepatic vein trunk and vena cava, total hepatic block method, modified total hepatic block method and total hepatic block method with preservation of vena cava patency can be chosen.