肝脏血流阻断方法及评价

Hepatectomy is the main option of treatment for liver cancer,and how to control the blood loss is an important issue for the recovery of patients.Continuous hepatic vascular occlusion(Pringle maneuver)is the oldest and simplest way for vascular occlusion and still used in clinical practice.But continuous hepatic vascular occlusion often gives rise to postischemic reperfusion injury due to clamping the portal vein and the hepatic artery in the hepatic pedicle.So intermittent clamping or hemihepatic vascular occlusion is recommended in complex liver resections or for patients with liver cirrhosis.Total hepatic vascular exclusion has the advantages of occlusion of vascular inflow and outflow of the liver,and is mainly used for patients with tumors invading the caval veins.Major hepatic veins and limited inferior vena cava reconstruction has been also achieved under inflow occlusion with extraparenchymal control of major hepatic veins.It is crucial to know how to select the optimal methods of hepatic vascular occlusion according to the specific conditions.Focusing on this issue,we have reviewed and evaluated various methods and relevant researches in this paper.     

肝下下腔静脉阻断在肝切除术中控制出血的临床应用

如何有效地控制肝切除术中出血一直是肝胆外科领域研究的热点。肝脏有流人道和流出道两套血管系统,对肝脏的血流控制包括对流人道和流出道血流的控制。控制流人道出血有许多简单而有效的方法,而如何有效地控制流出道出血一直是个难题。学者们创立了许多方法,包括全肝血流阻断、选择性全肝血流阻断等,但是这些方法都存在一定的弊端,只在特定的患者中被采用。有学者发现通过降低中心静脉压可减少肝切除术中肝静脉系统的出血,但是对其有效性仍存在争议。近年来,有文献报道在第一肝门阻断的同时,阻断肝下下腔静脉即可有效减少肝切除时来自肝静脉系统的出血。此方法相对于其他控制肝脏流出道出血的方法都简单易行,在肝切除术中有很高的应用价值。本文对肝下下腔静脉阻断在肝切除术中应用的现状进行讨论,对其减少肝切除术中出血的有效性及安全性进行总结和评价。     

Hepatic Vascular Exclusion With Preservation of the Caval Flow for Liver Resections

OBJECTIVE: To report the technique and results of an alternative method of vascular clamping during liver resections. BACKGROUND: Most liver resections require vascular clamping to avoid excessive blood loss. Portal triad clamping is often sufficient, but it does not suppress backflow bleeding, which can be prevented only by hepatic vascular exclusion. The latter method adds clamping of the inferior vena cava, which results in hypotension, requiring invasive anesthetic management. There is growing evidence that intermittent clamping is better tolerated than continuous clamping, especially in the presence of underlying liver disease. METHODS: Hepatic vascular exclusion with preservation of the caval flow (HVEPC) involved conventional inflow clamping associated with outflow control by clamping the major hepatic veins, thus avoiding caval occlusion. HVEPC was used in 40 patients undergoing major or complex liver resection, including 16 with underlying liver disease. HVEPC was total (clamping of the porta hepatis and all major hepatic veins) in 20 cases and partial (clamping of the porta hepatis and the hepatic veins of the resected territory) in 20. Clamping was continuous in 22 cases and intermittent in 18. Resections included 12 hemihepatectomies, 12 extended hepatectomies, 3 central hepatectomies, and 13 uni- or bisegmentectomies. RESULTS: Hemodynamic tolerance of clamping was excellent in all cases, without the need for therapeutic adjustment. Median red cell transfusion requirements were 0 units, and 28 patients (70%) did not receive any transfusions during the hospital stay. There were no deaths, and the morbidity rate was 17.5%. Median hospital stay was 10 days. CONCLUSION: HVEPC is a safe and effective procedure applicable to liver tumors without invasion to the inferior vena cava. It offers the advantages of conventional hepatic vascular exclusion without its hemodynamic drawbacks, and it can be applied intermittently or partially.     

Uptake of indocyanine green by hepatocytes under inflow occlusion of the liver

BACKGROUND: It is not clear that hepatic venous backflow actually contributes to hepatic tissue oxygenation under inflow occlusion of the liver. In order to prove that substances delivered via the hepatic vein can be utilized and/or metabolized in hepatocytes during inflow occlusion, hepatic uptake in bile and excretion of indocyanine green (ICG) were investigated in pigs. MATERIALS AND METHODS: Animals were divided into two groups: an inflow occlusion (IO) group (N = 6) and a total hepatic vascular exclusion (THVE) group (N = 3) using a bypass. One milligram of ICG per kilogram body weight was administered at the beginning of blood flow occlusion, the retention rate in the blood (ICG R) measured, and the ICG in the hepatic tissue measured by near-infrared (NIR) spectroscopy. Furthermore, the ICG concentration was measured in bile excreted by intermittent perfusion of the liver. RESULTS: ICG R declined with time in both groups; however, ICG R in the IO group decreased much faster than in the THVE group. There were significant differences between the two groups after 30 min of occlusion (P < 0.05). ICG in the hepatic tissue could be detected as a peak at 805 nm 10 min after ICG injection, and the peak became steeper with time. On the other hand, ICG was not detected at all in the hepatic tissue after 180 min in the THVE group. ICG was excreted in the bile after 60 min under IO and increased with time. On the contrary, ICG was not excreted in the bile at all under THVE. There were significant differences between the two groups after 90 min (P < 0.05). CONCLUSION: These results indicate that ICG can be extracted in hepatocytes and excreted in bile under IO of the liver. Consequently, substances such as oxygen and drugs, which are delivered via the hepatic vein, can be utilized and/or metabolized in hepatocytes under IO.     

Usefulness and problems of total hepatic vascular exclusion in liver surgery]

Total hepatic vascular exclusion (THVE) is an useful method enabling safe and sure hepatic resection in patients with liver tumors adjacent to the large hepatic veins or inferior vena cava (IVC), tumor thrombi, invasion of the IVC, etc. To avoid serious hypotension during THVE, test clamping of the IVC prior to the procedure is indispensable. Hemodynamics should be carefully maintained by blood transfusion and sufficient infusion of colloidal and electrolyte solutions during THVE. The veno-venous bypass method which shunts blood from the IVC and portal vein to the superior vena cava enables prolongation of the period of THVE and is useful to avoid postoperative renal dysfunction. In situ liver perfusion with cold solution during THVE is an additional modality by which the liver is protected from warm ischemic injury and the duration of THVE can be further prolonged. However, the maximum duration of THVE is still controversial, especially in patients with chronic liver damage. The most appropriate method for THVE should be carefully chosen in each case by considering the type of lesion, liver function, and the goal of the surgery.     

Complete versus selective portal triad clamping for minor liver resections: a prospective randomized trial

OBJECTIVE: To evaluate the feasibility, safety, efficacy, amount of hemorrhage, postoperative complications, and ischemic injury of selective clamping in patients undergoing minor liver resections. SUMMARY BACKGROUND DATA: Inflow occlusion can reduce blood loss during hepatectomy. However, Pringle maneuver produces ischemic injury to the remaining liver. Selective hemihepatic vascular occlusion technique can reduce the severity of visceral congestion and total liver ischemia. PATIENTS AND METHODS: Eighty patients undergoing minor hepatic resection were randomly assigned to complete clamping (CC) or selective clamping (SC). Hemodynamic parameters, including portal pressure and the hepatic venous pressure gradient (HVPG), were evaluated. The amount of blood loss, measurements of liver enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), and postoperative evolution were also recorded. RESULTS: No differences were observed in the amount of hemorrhage (671 +/- 533 mL versus 735 +/- 397 mL; P = 0.54) or the patients that required transfusion (10% versus 15%; P = 0.55). There were no differences on postoperative morbidity between groups (38% versus 29%; P = 0.38). Cirrhotic patients with CC had significantly higher ALT (7.7 +/- 4.6 versus 4.5 +/- 2.7 mukat/L, P = 0.01) and AST (10.2 +/- 8.7 versus 4.9 +/- 2.1 mukat/L; P = 0.03) values on the first postoperative day than SC. The multivariate analysis demonstrated that high central venous pressure, HVPG >10 mm Hg, and intraoperative blood loss were independent factors related to morbidity. CONCLUSIONS: Both techniques of clamping are equally effective and feasible for patients with normal liver and undergoing minor hepatectomies. However, in cirrhotic patients selective clamping induces less ischemic injury and should be recommended. Finally, even for minor hepatic resections, central venous pressure, HVPG, and intraoperative blood loss are factors related to morbidity and should be considered.     

Vascular occlusion to decrease blood loss during hepatic resection

BACKGROUND: Historically, the primary hazard with liver surgery has been intraoperative blood loss. This led to the refinement of inflow and outflow occlusive techniques. The utility of the different methods of inflow and outflow techniques for hepatic surgery were reviewed. METHODS: A search of the English literature (Medline, Embase, Cochrane library, Cochrane clinical trials registry, hand searches, and bibliographic reviews) using the terms "liver," "hepatic," "Pringle," "total vascular exclusion," "ischemia," "reperfusion," "inflow," and "outflow occlusion" was performed. RESULTS: A multitude of techniques to minimize blood loss during hepatic resection have been studied. The evidence suggests that inflow occlusion techniques are generally well tolerated. These should be used with caution in patients with cirrhosis, fibrosis, steatosis, cholestasis, and recent chemotherapy, and for prolonged time intervals. CONCLUSIONS: Harmful effects of intraoperative blood loss and transfusion occur during hepatic resection. Portal triad clamping (PTC) is associated with less blood loss compared with no clamping. In procedures with ischemic times <1 hour in length, PTC-C (continuous) is likely equal to PTC-I (intermittent). In patients with chronic liver disease or undergoing lengthy operations, PTC-I is likely superior to PTC-C. PTC is superior to total vascular exclusion except in patients with tumors that are large and deep seated, hypervascular, and/or abutting the hepatic veins or vena cava and in patients with increased right-sided heart pressures.     

Comparison of ischemic preconditioning and intermittent and continuous inflow occlusion in the murine liver

OBJECTIVE: To compare protection of the liver by ischemic preconditioning and intermittent inflow occlusion in a mouse model of prolonged periods of ischemia. SUMMARY BACKGROUND DATA: Preconditioning (short ischemic stress prior to a prolonged period of ischemia) and intermittent inflow occlusion protect the liver against reperfusion injury. This is the first study comparing these two modalities with continuous inflow occlusion (control). METHODS: Mice were subjected to 75 or 120 minutes of 70% hepatic ischemia and 3 hours of reperfusion. Each ischemic period was evaluated using three different protocols: continuous ischemia (control), preconditioning (10 minutes ischemia and 15 minutes reperfusion) prior to the prolonged ischemic insult, and intermittent clamping (cycles of 15 minutes ischemia and 5 minutes reperfusion). Organ injury was evaluated using serum levels of aspartate aminotransferase (AST), hematoxylin and eosin staining, and specific markers of apoptosis (cytochrome C release, caspase 3 activity, and TUNEL staining). Animal survival was determined using a model of total hepatic ischemia. RESULTS: Intermittent inflow occlusion and ischemic preconditioning were both protective against ischemic insults of 75 and 120 minutes compared with controls (continuous ischemia only). Protection against 75 minutes of ischemia was comparable in the intermittent clamping and the ischemic preconditioning group, whereas intermittent clamping was superior at 120 minutes of ischemia. One hundred percent animal survival was observed after 75 minutes of total hepatic ischemia using both protective protocols, whereas all animals subjected to continuous ischemia died after surgery. After 120 minutes of ischemia, intermittent inflow occlusion was associated with better animal survival (71%) compared with preconditioning (14%). CONCLUSIONS: Preconditioning and intermittent clamping are both protective against prolonged periods of ischemia. In the clinical setting, preconditioning is superior for ischemic periods of up to 75 minutes because it is not associated with blood loss during transection of the liver. However, for prolonged ischemic insults exceeding 75 minutes, intermittent clamping is superior to preconditioning.     

Effects of hepatovenous back flow on ischemic- reperfusion injuries in liver resections with the pringle maneuver

BACKGROUND: Experimental findings have demonstrated a beneficial role of retrograde blood flow from hepatic veins that takes place during the Pringle maneuver in liver resections. The cytoprotective effect of hepatovenous back-perfusion has not been evaluated in humans. A randomized prospective study was designed to compare the response of liver cells to ischemic-reperfusion injury during the application of two different ischemic procedures: inflow versus inflow plus outflow vascular occlusion of the liver. STUDY DESIGN: Forty patients were randomly allocated to undergo liver resection using the continuous Pringle maneuver (n = 20) or inflow plus outflow vascular occlusion of the liver by selective hepatic vascular exclusion (n = 20). Liver function was assessed on postoperative days 1 to 6. Response of liver cells to I/R injury was evaluated by measuring interleukins IL-6 and IL-8 at 3, 12, 24, and 48 hours after reperfusion. Oxidative stress was assessed by measuring malondialdehyde levels. RESULTS: Both groups were comparable regarding ischemic time, operative time, and extent of liver resection. Patients in whom retrograde blood flow to the liver took place during the Pringle maneuver showed better liver function postoperatively and less severe hepatic I/R injuries compared with those undergoing liver resection using both inflow and outflow vascular occlusion. Oxidative stress was significantly lower in the Pringle maneuver group compared with the inflow plus outflow vascular occlusion group (mean [+/- SD] malondialdehyde 8 +/- 2.1 micromol/L in the Pringle group versus 14.7 +/- 1.8 micromol/L in the selective hepatic vascular exclusion group 30 min after reperfusion, p < 0.01). CONCLUSIONS: Back perfusion via hepatic veins contributes to attenuation of I/R damage during the Pringle maneuver and should be preferred if possible during liver resection.     

入肝血流阻断对肝切除术后血乳酸水平的影响

目的 分析肝切除术中入肝血流阻断对术后动脉血乳酸水平及pH值的影响.方法 回顾性分析我科2006年1月至2008年12月行肝切除术的68例患者,根据术中是否行人肝血流阻断分为肝门阻断组(20例)、规则半肝切除组(22例)和未阻断肝门组(26例).比较3组患者术后动脉血气、乳酸浓度及肝、肾功能等指标.结果 肝门阻断组和规则半肝切除组患者术后动脉血乳酸浓度明显升高[(5.53±2.31)mmoL/L,(5.62±2.52)mmol/L),与术中未阻断肝门组[(3.37±1.56)mmol/L]比较差异均有统计学意义(P<0.05);半肝切除组HCO3-水平较肝门不阻断组明显降低[(19.68±3.82)mmoL/L vs(21.65±2.48)mmol/L,P<0.05];3组患者术后的pH、肝肾功能等改变无统计学意义.结论 人肝血流阻断可导致肝切除术后动脉血乳酸水平明显增高,术后密切监测乳酸浓度并及时处理,可避免术后高乳酸血症及代谢性酸中毒.     

The comparative effects of total hepatic vascular isolation techniques performed at different durations in rat

BACKGROUND: Total hepatic vascular exclusion (THVE) leads to massive venous congestion below the level of diaphragm and may promote undesirable hemodynamic disturbances in some patients. Supraceliac aortic clamping during THVE may achieve hemodynamic stability at the price of arterial ischemia. However, the parenchymal injury of venous congestion has been a greater concern than of arterial ischemia in various settings. We hypothesized that supraceliac aortic occlusion during THVE may attenuate the reperfusion injury and improve the outcome that would be acquired after THVE alone. MATERIAL AND METHODS: Rats were randomly assigned to (1) THVE alone, (2) THVE plus aortic occlusion, (3) THVE plus celio-mesenteric arterial occlusion or (4) sham during 30, 45, or 60 min followed by 180 min reperfusion period. Serum enzymes (alanine aminotransferase, lactate dehydrogenase) and creatinine as well as tissue "thiobarbituric acid reactive substances" (TBARS) and histopathology were evaluated. Seven animals per group were followed for survival up to 7 d. RESULTS: After 30 min, no difference was found in serum enzyme, creatinine and tissue TBARS measures among the isolation methods used. In these, all rats survived to 7 d. However, after 45 and 60 min isolation, aortic occlusion resulted in significant rise in serum enzyme and tissue TBARS measures as well as poor survival (14% and 0%, respectively). In contrast, all rats survived even after 60 min of THVE. CONCLUSIONS: THVE was tolerated up to 60 min with less reperfusion injury and better survival than celio-mesenteric arterial occlusion and supraceliac aortic occlusion in the rat, if needed, aortic clamping should not exceed 30 min. Beyond that, selective celio-mesenteric arterial occlusion may be considered.     

Increased sinusoidal pressure is associated with early liver weight gain in ischemia-reperfusion injury in isolated perfused rat liver

BACKGROUND: Hepatic ischemia-reperfusion (I/R) is accompanied by liver weight gain and ascites formation. This could be caused by an increase in sinusoidal pressure, a determinant of hepatic transvascular fluid movement. We determined the role of sinusoidal pressure, assessed by triple vascular occlusion pressure (P(to)), in the I/R injury in isolated rat livers perfused with leukocyte-free diluted blood bivascularly via the portal vein and hepatic artery. MATERIALS AND METHODS: Ischemia was induced at room temperature by occlusion of either the inflow lines of the hepatic artery and portal vein (the open outflow group, n = 10) or both the inflow and the outflow (hepatic venous) lines (the closed outflow group, n = 10) for 1 h, followed by 1-h reperfusion in a recirculating manner. RESULTS: Liver weight in both groups increased biphasically after reperfusion; the initial peak occurred at 3 min and the second peak at 60 min. Immediately after reperfusion, P(to) peaked, followed by a gradual decline. The initial weight increase in groups combined was significantly and positively correlated with an increase in P(to) (r = 0.716, P = 0.0002), but the second peak was independent of P(to). Liver injury, assessed by perfusate levels of hepatic enzymes and reduced bile flow rate, was observed at 60 min after reperfusion in both groups. CONCLUSIONS: These findings suggest that increased sinusoidal pressure contributes to only the early liver weight gain after reperfusion in isolated perfused rat livers. The late weight gain may be presumably due to liver injury.     

Optimal cycle of intermittent portal triad clamping during liver resection in the murine liver.

We designed this experimental study to determine the optimal cycle for intermittent inflow occlusion during liver resection. A cycle of intermittent clamping (IC) for 15 minutes of ischemia followed by reperfusion for 5 minutes during liver resection is currently the most popular protocol used by experienced liver centers. As each period of reperfusion is associated with bleeding, longer periods of clamping would be advantageous. However, the longest safe duration of successive ischemia is unknown. Three groups of mice were subjected to a total liver ischemic period for 90 minutes; 2 groups underwent IC for 15 or 30 minutes, respectively, followed by 5 minutes of reperfusion, while the control group was subjected to continuous inflow occlusion only. The degree of tissue injury was assessed using biochemical and histological markers, as well as animal survival. While serious injury was observed in the continuous clamping group, both IC groups were associated with minimal injury, including lesser degrees of apoptosis and necrosis. All animals survived in the IC groups, while all animals died following 90 minutes of continuous inflow occlusion. In conclusion, intermittent portal pedicle clamping with 15- or 30-minute cycles is highly protective. A period of 30 minutes clamping should be preferred, since this would decrease the amount of blood loss associated with each cycle. This data should be confirmed in humans, and may represent a change in the current practice of hepatic surgery.     

Severe juxtahepatic venous injury: survival after prolonged hepatic vascular isolation without shunting

Survival following major juxtahepatic venous injury is rare in blunt liver trauma despite the use of intracaval shunting. Prolonged liver arterial inflow control, total hepatic venous isolation and lobectomy without shunting was used in a patient to repair a combined vena caval and hepatic venous injury after blunt liver injury. An extended period of normothermic hepatic ischemia was tolerated. Early recognition of retrohepatic venous injury and temporary liver packing to control bleeding and correct hypovolemia are essential before caval occlusion. Hepatic vascular isolation without shunting is an effective simple alternative technique allowing major venous repair in complex liver trauma.     

Occlusion of hepatic blood inflow for complex central liver resections in cirrhotic patients: a randomized comparison of hemihepatic and total hepatic occlusion techniques

BACKGROUND: Intermittent occlusion of hepatic blood inflow by means of a hemihepatic or total hepatic occlusion technique is essential for reducing operative blood loss. Central liver resection to preserve more functioning liver parenchyma is mandatory for centrally located liver tumors in patients with cirrhosis, but it requires a longer overall hepatic ischemic time because of a wide transection plane. No controlled comparison has been performed for the 2 techniques in these operations. HYPOTHESIS: Hemihepatic inflow occlusion may be beneficial in cirrhotic patients who undergo complex central hepatectomy with a wide liver transection plane. DESIGN: A prospective, randomized study. SETTING: University hospital and tertiary referral center. PATIENTS: During liver parenchymal transection, 58 cirrhotic patients who underwent complex central liver resections with a wide transection plane were prospectively randomized into 2 groups. In the group undergoing total hepatic inflow clamping (group T; n = 28), occlusion of hepatic blood inflow was performed for 15 minutes with declamping for 5 minutes. In the group undergoing selective clamping of ipsilateral blood inflow (group H; n = 30), clamping was performed for 30 minutes with declamping for 5 minutes. INTERVENTION: Comparison of patient backgrounds, operative procedures, and early postoperative results. MAIN OUTCOME MEASURES: Operative blood loss, need for blood transfusion, and postoperative morbidity. RESULTS: The patients' backgrounds, operative procedures, and area of liver transection plane were not significantly different between the 2 groups. In all patients, the liver transection areas were greater than 60 cm(2) and overall liver ischemic times were greater than 60 minutes. The amount of operative blood loss and incidence of blood transfusion were significantly greater in group T because of greater blood loss during declamping. Overall liver ischemic and total operative times, postoperative morbidity, and postoperative changes in liver enzyme levels were not significantly different between groups. No in-hospital deaths occurred in either group. CONCLUSIONS: Intermittent hemihepatic and total occlusion of hepatic blood inflow are safe in cirrhotic patients with an overall ischemic time of greater than 60 minutes. However, for complex liver resections with an estimated liver transection plane of greater than 60 cm(2), hemihepatic occlusion of blood inflow, if feasible, may be recommended in cirrhotic patients to reduce operative blood loss and the incidence of blood transfusion under our defined occlusion time.     

Comparison of Two Methods of Selective Hepatic Vascular Exclusion for Liver Resection Involving the Roots of the Hepatic Veins

Background  Selective hepatic vascular exclusion (SHVE) is an effective hepatic vascular exclusion in controlling both inflow and outflow without interruption of caval flow, as it combines Pringle maneuver with extrahepatic selective occlusion of hepatic veins. But SHVE has not been widely used due to difficulty in extrahepatic dissection of hepatic veins. When the tumor is very close to the roots of the hepatic veins, dissecting the posterior wall of the hepatic vein may lead to rupture and massive bleeding of the hepatic vein. With our experience, clamping hepatic veins with Satinsky clamps is a safer and easier occlusion method by which the posterior wall of the hepatic veins does not need to be separated and encircled. In this report, we compared the results of selective hepatic vascular occlusion with tourniquet and Satinsky clamp for major liver resection involving the roots of the hepatic veins. Methods  Between January 2003 to June 2006, 180 patients who underwent major liver resection with SHVE were divided into two groups according to different methods of hepatic vascular occlusion: occlusion with tourniquet (tourniquet group, n = 95) and occlusion with Satinsky clamp (Satinsky clamp group, n = 85). In the tourniquet group, the hepatic veins were encircled and occluded with tourniquet. In the Satinsky clamp group, the hepatic veins were not encircled and clamped directly by Satinsky clamp. Results  Intraoperative and postoperative consequences of the patients were analyzed. The dissecting time for each hepatic vein was significantly shorter in the Satinsky group (6.2 ± 2.4 min vs 18.3 ± 6.2 min) than in the tourniquet group. In the tourniquet group, five hepatic veins (one right hepatic vein and four common trunk of left-middle hepatic veins) could not be dissected and encircled because the tumors involved the cava hepatic junction, and another common trunk of the left-middle hepatic vein had a small rupture during the dissection. These six patients then received successful occlusion with Satinsky clamp. There was no difference between the two groups regarding the operation duration, ischemia time, intraoperative blood loss, and postoperative complication rate. Conclusion  Both methods of the hepatic vein occlusion have the same effect on controlling hepatic vein bleeding, but occlusion with Satinsky clamp is safer, easier, and consumes less time in dissecting. Li Ai-Jun And Pan Ze-Ya contributed equally to this work.     

Prolonged continuous or intermittent vascular inflow occlusion during hemihepatectomy in pigs

OBJECTIVE: To assess ischemia and reperfusion (I/R) injury in a hemihepatectomy model in pigs after prolonged continuous or intermittent vascular inflow occlusion in the liver. SUMMARY BACKGROUND DATA: Massive intraoperative blood loss during liver resections can be prevented by temporary vascular inflow occlusion, consequently leading to ischemia and reperfusion injury in the remnant liver. Previously, in a pig liver resection model in which only limited I/R injury was induced during brief (90 min) vascular inflow occlusion, the authors demonstrated reduced I/R injury after continuous (CNT) occlusion, compared to intermittent (INT). This liver resection study on pigs was undertaken to assess I/R injury after prolonged (120 min) CNT or INT occlusion. METHODS: In pigs (37.0 +/- 1.5 kg), liver ischemia during 2 hours was CNT (n = 6) or INT (n = 6) (eight subsequent periods of 12 min ischemia and 3 min recirculation), followed by 6 hours of reperfusion. A left hemihepatectomy (45.5% +/- 1.4%) was performed within the first 12 minutes of ischemia. No hepatic pedicle clamping or liver resection was performed in control experiments (n = 6). Microvascular damage was assessed by hyaluronic acid (HA) uptake capacity of the liver (parameter of early sinusoidal endothelial cell damage) and restoration of intrahepatic tissue pO2 during reperfusion. Hepatocellular damage was tested by plasma concentrations of aspartate aminotransferase (AST), alanine aminotransferase, and lactate dehydrogenase (LDH). RESULTS: Hyaluronic acid uptake after 6 hours of reperfusion, compared to preischemic uptake, was unaltered in the control group, but was significantly reduced in both resection groups. However, more HA was taken up after INT occlusion, compared to CNT (60.4% +/- 5.6% and 39.5% +/- 3.7%, respectively; ANOVA: p = 0.001). Intrahepatic tissue pO2 distribution after 6 hours of reperfusion more closely returned to preischemic configuration in the INT group than in the CNT group, indicating reduced microcirculatory disturbances after INT occlusion. Release of AST and LDH after 6 hours of reperfusion was significantly increased in both CNT and INT groups. Lower AST levels, however, were found after INT occlusion than after CNT occlusion (267.0 +/- 74.7 U/l and 603.3 +/- 132.4 U/l, respectively; p = 0.06). CONCLUSIONS: Intermittent hepatic vascular inflow occlusion during prolonged liver ischemia in pigs resulted in less microcirculatory and hepatocellular injury, compared to continuous occlusion. Intermittent clamping is preferable when prolonged periods of vascular inflow occlusion are applied during liver resections.     

入肝血流阻断和全肝血流阻断对肝组织氧压影响

目的 研究兔常温下入肝血流阻断（portal triad clamp,PTC)及全肝血流阻断（total hepatic vascular exclusion,THVE)对肝组织氧压（tissue oxygen pressure,Ptio2)的影响。方法 24只兔均分二组即PTC和THVE组。分别测定二组缺血前、缺血30min及再灌注30min后肝Ptio2值及血清丙氨酸氨基转氨酶（ALT）值变化。结果 PTC和THVE组均表现为肝Ptio2下降，但THVE较PTC组肝Ptio2值下降更显著（P＜0．01）、血清ALT值也明显升高（P＜0．05）。结论 PTC组较THVE组对肝缺血的耐受性增加。     

How much ischemia can the liver tolerate during resection?

The use of vascular inflow occlusion (VIO, also known as the Pringle maneuver) during liver surgery prevents severe blood loss and the need for blood transfusion. The most commonly used technique for VIO entails clamping of the portal triad, which simultaneously occludes the proper hepatic artery and portal vein. Although VIO is an effective technique to reduce intraoperative blood loss, it also inevitably inflicts hepatic ischemia/reperfusion (I/R) injury as a side effect. I/R injury induces formation of reactive oxygen species that cause oxidative stress and cell death, ultimately leading to a sterile inflammatory response that causes hepatocellular damage and liver dysfunction that can result in acute liver failure in most severe cases. Since the duration of ischemia correlates positively with the severity of liver injury, there is a need to find the balance between preventing severe blood loss and inducing liver damage through the use of VIO. Although research on the maximum duration of hepatic ischemia has intensified since the beginning of the 1980s, there still is no consensus on the tolerable upper limit. Based on the available literature, it is concluded that intermittent and continuous VIO can both be used safely when ischemia times do not exceed 120 min. However, intermittent VIO should be the preferred technique in cases that require >120 min duration of ischemia.