Prolonged continuous or intermittent vascular inflow occlusion during hemihepatectomy in pigs

Efficacy of high-intensity focused ultrasound-assisted hepatic resection (HIFU-AR) on blood loss reduction in patients with liver metastases requiring hepatectomy: study protocol for a randomized controlled trial

BACKGROUND

Liver resection is the only potentially curative treatment for colorectal liver metastases (LM). It is considered a safe procedure, but is often associated with blood loss during liver transection. Blood transfusions are frequently needed, but they are associated with increased morbidity and risk of recurrence. Many surgical devices have been developed to decrease blood loss. However, none of them has proven superior to the standard crushing technique. We developed a new, powerful intra-operative high-intensity focused ultrasound (HIFU) transducer which destroys tissue by coagulative necrosis. We aim to evaluate whether HIFU-assisted liver resection (HIFU-AR) results in reduced blood loss.

METHODS

This is a prospective, single-centre, randomized (1:1 ratio), comparative, open-label phase II study. Patients with LM requiring a hepatectomy for ≥ 2 segments will be included. Patients with cirrhosis or sinusoidal obstruction syndrome with portal hypertension will be excluded. The primary endpoint is normalized blood loss in millilitres per square centimetre of liver section plane. Secondary endpoints are: total blood loss, transection time, transection time per square centimetre of liver area, haemostasis time, clip density on the liver section area, rate and duration of the Pringle manœuvre, rate of patients needing a blood transfusion, length of hospital stay, morbidity, patients with positive resection margin, and local recurrence. Assuming a blood loss of 7.6 ± 3.7 mL/cm² among controls, the study will have 85% power to detect a twofold decrease of blood loss in the experimental arm, using a Wilcoxon (Mann-Whitney) rank-sum test with a 0.05 two-sided significance level. Twenty-one randomized patients per arm are required. Considering the risk of contraindications at surgery, up to eight patients may be enrolled in addition to the 42 planned, with an enrolment period of 24 months. Randomization will be stratified by surgeon.

DISCUSSION

We previously demonstrated the safety and efficacy of intra-operative HIFU in patients operated on for LM. We also demonstrated the efficacy of HIFU-AR in a preclinical study. Participants in the HIFU-AR group of this randomized trial can expect to benefit from reduced blood loss and decreased ischemia of liver parenchyma.

TRIAL REGISTRATION

Clinicaltrial.gov, NCT02728167 . Registered on 22 March 2016.

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.

Bradykinin Impairs and HOE 140 does not Protect Rat Hindlimb Skeletal Muscle Against Tourniquet-induced Reperfusion Injury

BACKGROUND

Bradykinin (BK) is used in different tissues. Dose-dependent studies have demonstrated that low doses protect against ischemia/reperfusion (I/R) injury while higher doses lead to adverse effects. Although the beneficial effects of BK infusion were observed in myocardium, its role on the I/R impact in skeletal muscle (SM) has not been fully clarified.

OBJECTIVE

This study was carried out to evaluate the effects of BK, administered in the hindlimbs of rats subjected to I/R.

METHODS

The study design included three experimental groups: Group 1 control (saline), Group 2 (bradykinin), and Group 3 (HOE 140, a BK2 receptor blocker). In all three groups, rats were subjected to hindlimb ischemia for a total of 2 h followed by continuous 4 h of reperfusion with pharmacological interventions. The methods include analysis of enzymes (lactate dehydrogenase-LDH and creatinine phosphokinase-CPK), cell membrane marker of injury (malondialdeyde-MDA), recruitment of neutrophils (myeloperoxidase-MPO), and apoptosis index (immunohistochemistry TUNEL in situ peroxidase dead end).

RESULTS

Except for the apoptotic index, all parameters studied were shown to be elevated in the reperfusion group intervened with BK. The blocking of BK2 receptors by HOE 140 did not affect the I/R injury.

CONCLUSION

After 2 h of total ischemia, infusion of bradykinin during 4 h of reperfusion, worsened the I/R injury in the hindlimb skeletal muscle.

Hydrogen sulfide improves resuscitation via non-hibernatory mechanisms in a porcine shock model

BACKGROUND

Hydrogen sulfide (H2S) has been demonstrated to induce a "suspended animation-like" state in rodent models by reversible inhibition of cellular respiration and marked metabolic suppression and has been proposed as a potential pharmacologic adjunct to resuscitation from shock states. There are few data currently available about the mechanisms and efficacy of H2S in larger animals or humans. We examined H2S as a pharmacologic adjunct to resuscitation in a porcine model of severe traumatic shock.

METHODS

Twenty-one adult swine were assigned to three study arms: sham, H2S, and saline vehicle controls (SC). All pigs underwent laparotomy and instrumentation, and the two study arms then underwent a 35% controlled hemorrhage followed by 50 min of truncal ischemia via aortic cross-clamp. H2S (5 mg/kg) or saline was administered immediately before reperfusion, followed by 6 h of resuscitation. Resuscitation requirements, laboratory parameters, end-organ histology, and inflammatory product gene expression (by reverse transcription-polymerase chain reaction) were measured and compared between groups.

RESULTS

All animals survived to the 6-h postresuscitation time point. Both treatment arms demonstrated severe shock characterized by fluid and vasopressor requirements, metabolic acidosis, and hypotension compared with sham animals. Animals treated with H2S demonstrated significantly lower resuscitative requirements (total epinephrine 727 versus 3052 μg; P < 0.05), decreased fluid requirements, and lower serum lactate levels (7 versus 10 mmol/L) versus SC. Cardiac output was slightly decreased with H2S treatment but all other hemodynamic and metabolic parameters were equivalent between H2S and C groups. Serum liver and kidney biomarkers were unchanged, but administration of H2S was associated with a significant improvement in histopathologic liver and kidney injury scores compared with SC (both P < 0.05). Both study groups demonstrated significantly increased gene expression of hypoxia-inducible factor 1α and nitric oxide synthase (endogenous nitric oxide synthase, inducible nitric oxide synthase [iNOS]2, iNOS3) relative to sham animals. However, H2S was associated with increased expression of hypoxia-inducible factor 1α and decreased iNOS2 levels compared with SC.

CONCLUSIONS

Administration of H2S in a large-animal model of severe traumatic shock resulted in a significant decrease in resuscitative requirements, decreased metabolic acidosis, and less end-organ histologic injury compared with standard resuscitation. H2S did not induce profound metabolic suppression as seen in rodents, and appears to have alternative mechanisms of action in large animals.

Flutamide fails to reduce resuscitation requirements in a porcine ischemia-reperfusion model

BACKGROUND

Hemorrhagic shock and subsequent resuscitation can lead to ischemia-reperfusion injury, followed by multiorgan failure and death. Flutamide, a vasoactive nonsteroidal antiandrogen compound, is thought to improve tissue and organ perfusion. We tested whether administration of flutamide-cyclodextrin (FLU-CYD) alters physiologic parameters or resuscitation requirements in a porcine model of severe acidosis and shock secondary to combined hemorrhage + ischemia-reperfusion injury.

METHODS AND MATERIALS

Fifteen male pigs underwent a 35% blood-volume hemorrhage. Ischemia was induced by cross-clamping the supraceliac aorta for 50 min followed by reperfusion and resuscitation. FLU-CYD complex was administered during aortic clamping. Fluid resuscitation and epinephrine were titrated by protocol to maintain mean arterial pressure ≥40 mm Hg for 6 h. Sequential laboratory results were obtained and serum levels of FLU and 2-hydroxy-flutamide (FLUOH) were measured by mass spectrometry.

RESULTS

Mean requirements for injured control swine were 14.6 (± 1.21 standard error of the mean [SEM]) L crystalloid saline and 0.59 (± 0.29 SEM) g epinephrine, compared with 16.30 (± 1.33 SEM) L and 0.54 (± 0.16 SEM) g, respectively, in the FLU-CYD group (both P > 0.05). There were no significant differences in central hemodynamics between control and experimental groups. No significant differences for pH, bicarbonate, fibrinogen, or international normalized ratio were evident. FLU-CYD resuscitation was associated with a significant increase in lactate levels compared with controls (10.1 versus 5.7 mmol/L, P < 0.05). Histologic injury was significantly increased in the livers of FLU-CYD compared with sham (P = 0.022). High serum levels of FLU and the active metabolite FLUOH were measurable throughout the resuscitation period.

CONCLUSIONS

Flutamide failed to show any benefit to resuscitation in a model of severe injury and was associated with increased acidosis, hemodilution, and liver injury compared with standard crystalloid resuscitation.

Intermittent clamping is superior to ischemic preconditioning and its effect is more marked with shorter clamping cycles in the rat liver

BACKGROUND

Intermittent clamping (IC) and ischemic preconditioning (PC) reportedly protect the liver against the ischemia/reperfusion (I/R) injury induced by inflow occlusion during hepatectomy. While IC cycles consisting of 15 min of clamping with 5 min of reperfusion are used empirically, the optimal IC cycle has not been established. We compared the effects of various cycles of IC and PC in the rat liver.

METHODS

Rats subjected to 60 min of inflow occlusion were assigned to the following five groups (n = 8 each): 60 min of continuous ischemia; 4 cycles comprising 15 min of ischemia/5 min of reperfusion; 6 cycles comprising 10 min of ischemia/3.3 min of reperfusion; 12 cycles comprising 5 min of ischemia/1.7 min of reperfusion (the time ratio of ischemia to reperfusion in the IC groups was 3:1); and PC (10/10 min of ischemia/reperfusion) prior to 60 min of ischemia. The severity of liver injury was assessed by determining the serum alanine aminotransferase (ALT) level, bile flow, tissue glutathione content, and induction of apoptosis (terminal deoxynucleotidyl transferase-mediated biotin nick end-labeling [TUNEL] staining and DNA laddering), and by histological examination of areas of severe necrosis.

RESULTS

All the parameters indicated that liver injury was attenuated in the three IC groups compared with the continuous group; furthermore, this effect became increasingly marked with shorter cycles of IC. PC did not exert a protective effect under the present experimental conditions.

CONCLUSION

Various cycles of IC consistently conferred protection against I/R injury, and IC with shorter cycles of ischemia and reperfusion was more effective. No protective effect of PC was evident. IC is a more robust strategy than the PC protocol for liver protection.

Anesthetic Considerations in Hepatectomies under Hepatic Vascular Control

Background. Hazards of liver surgery have been attenuated by the evolution in methods of hepatic vascular control and the anesthetic management. In this paper, the anesthetic considerations during hepatic vascular occlusion techniques were reviewed. Methods. A Medline literature search using the terms "anesthetic," "anesthesia," "liver," "hepatectomy," "inflow," "outflow occlusion," "Pringle," "hemodynamic," "air embolism," "blood loss," "transfusion," "ischemia-reperfusion," "preconditioning," was performed. Results. Task-orientated anesthetic management, according to the performed method of hepatic vascular occlusion, ameliorates the surgical outcome and improves the morbidity and mortality rates, following liver surgery. Conclusions. Hepatic vascular occlusion techniques share common anesthetic considerations in terms of preoperative assessment, monitoring, induction, and maintenance of anesthesia. On the other hand, the hemodynamic management, the prevention of vascular air embolism, blood transfusion, and liver injury are plausible when the anesthetic plan is scheduled according to the method of hepatic vascular occlusion performed.

High-intensity focused ultrasound (HIFU)-assisted hepatic resection in an animal model

BACKGROUND

Bleeding is the main cause of postoperative complications of hepatic surgery. To minimize intraoperative bleeding during hepatectomy, resections are generally carried out under hepatic vascular control despite the risk of liver dysfunction in patients with chronic liver disease. This study evaluates the feasibility and safety of high-intensity focused ultrasound (HIFU)-assisted hepatic resection during an open procedure in an animal model.

METHODS

Three groups of 12-14-week-old Landrace pigs (n = 7/group) were used to evaluate HIFU-assisted liver resection (group A) vs liver resection with or without portal triad clamping (groups B and C). In each pig, liver resection was performed on the right and left paramedian lobes. The following were evaluated and compared in the 3 groups: total blood loss, blood loss/cm(2) of resection area, clip density, procedure duration, morbidity, and mortality.

RESULTS

Median blood loss was significantly lower in group A than in group B (P = .02), and group C (P = .007). Median blood loss/cm(2) of resection area was 4.77 mL/cm² in group A, 11.35 mL/cm² in group B, 12.22 mL/cm² in Group C. Precoagulation resulted in sealing blood vessels <5 mm; therefore, median clip density during liver transection was 0.78 clip/cm² in group A, 1.61 clip/cm(2) in group B, and 1.57 clip/cm(2) in group C. Median duration of the surgical procedure was 12 min in group A, 21 min in group B, and 19 min in group C.

CONCLUSIONS

HIFU-assisted hepatic resection during an open procedure in an animal model is safe, reduces bleeding, and allows real-time ultrasound guidance.

Comparison of major hepatectomy performed under intermittent Pringle maneuver versus continuous Pringle maneuver coupled with in situ hypothermic perfusion

BACKGROUND

The Pringle maneuver (hepatic inflow occlusion), applied intermittently or continuously, carries the risk of inducing ischemic and reperfusion injury. The risk of damage is higher in the latter procedure. Studies have shown that continuous Pringle maneuver coupled with in situ hypothermic perfusion (CPM-HP) circumvents such adversity. However, reports comparing this technique with the intermittent Pringle maneuver (IPM) are lacking. We therefore report our experience with the use of CPM-HP and compare its outcome with that of IPM.

METHODS

We evaluated the outcome of similar sets of patients who had major hepatic resections performed under IPM and CPM-HP. Variables including short-term survival rate (>90 days), complications, operative time, transection time, intraoperative blood loss, postoperative liver functions, and postoperative hospital stay were used to compare the two groups.

RESULTS

Eighteen major hepatectomies were performed with CPM-HP and 16 with IPM. CPM-HP was safely performed in patients with chronic liver disease. Lowering the liver's temperature extends the clamping period to 140 min. Perioperative outcomes including operative time (383.9 ± 89.4 vs. 351.9 ± 70.3 min, p = 0.252), blood loss (225.6 ± 48.4 vs. 351.9 ± 70.3 ml, p = 0.057), postoperative hospital stay, morbidity rate, and the rate of liver functions following resections were comparable for the CPM-HP and IPM groups. There was no mortality. Parenchymal transection time was significantly longer in the CPM-HP group (104.1 ± 20.2 vs. 85.0 ± 15.4 min, p = 0.004)

CONCLUSION

Our findings did not show there to be a significant advantage of CPM-HP over IPM.

Protective effect of intermittent clamping of the portal triad in the rat liver on liver ischemia-reperfusion injury

BACKGROUND

Intermittent clamping (IC) of the portal triad is an effective method of protecting the liver from ischemia-reperfusion injury (IR). In clinical practice, this method is employed during a resection, but its mechanism is still not clear.

OBJECTIVES

To evaluate the effect of IC on rat liver and determine its mechanisms.

MATERIALS AND METHODS

Wistar rats were submitted to 60-min IC (cycles of 12-min clamping followed by 4-min reperfusion), and the samples were collected after 1, 6, and 72 hrs of reperfusion. We determined the serum activity of alanine aminotransferase (ALT), and measured the concentration of TNF-α, malondialdehyde (MDA) and myeloperoxidase (MPO) in liver homogenates. The apoptosis of hepatocytes was evaluated immunohistochemically.

RESULTS

When compared to the IR rats, the activity of ALT decreased in the IC group in all periods of observation (the highest decrease of ~48% after 1 hr of reperfusion). When compared to the IR group, a statistically significant decrease (p < 0.05) in the TNF-α concentration (~33%) in the IC rats occurred only after 1 hr of reperfusion, and it was accompanied by a decrease in the MPO concentration after 1 and 6 hrs of reperfusion. IC reduces the effects of reactive oxygen species (ROS) activity, which has been confirmed by a statistically significant decrease in MDA concentration by 25%-35% in all studied periods. The limitation of hepatocytes apoptosis due to IC occurs in the early (~26%; p < 0.05) and late (~45%; p < 0.01) phases of reperfusion.

CONCLUSIONS

The use of IC in early phase of reperfusion brings about a decrease in TNF-α release, which can be related to liver injury due to neutrophil infiltration and apoptotic cell reduction. It seems that the reduction of lipid peroxidation may also limit the liver injury.

Microarray and functional cluster analysis implicates transforming growth factor beta1 in endothelial cell dysfunction in a swine hemorrhagic shock model

BACKGROUND

Trauma leading to massive hemorrhage results in widespread tissue hypoxia, anaerobic metabolism, and production of inflammatory cytokines and oxidative molecules injurious to the vascular endothelium. Although trauma-related endothelial cell pathophysiology has been extensively studied, very little is known regarding gene transcriptional changes that occur during the event, particularly in endothelia. Thus, we employed fluorescent microarray analysis of gene transcription to elucidate critical pathways and gene products involved in endothelial dysfunction.

MATERIALS AND METHODS

A trauma-hemorrhage/shock (T-H/S) model mimicking the physiologic changes seen in human trauma was performed on 10 Yorkshire swine, consisting of 35% blood volume hemorrhage followed by 6 h of full resuscitation. Aortic endothelium was analyzed by microarray and functional clusters were identified through the use of Database for Annotation, Visualization, and Integrated Discovery (DAVID) software.

RESULTS

Injured swine developed profound acidosis, coagulopathy, massive resuscitative fluid requirements, and microscopic changes of ischemia/reperfusion injury. While 1007 transcripts were down-regulated, 529 transcripts were up-regulated. DAVID functional clustering analysis revealed 21 significantly altered biological processes that were grouped into 12 distinct functional categories. The transforming growth factor beta (TGFβ) family of genes was the most interrelated. In addition, vascular endothelial growth factor (VEGF) signaling members and leukocyte chemoattractants were also altered.

CONCLUSIONS

Our model identified two major signaling pathways, TGFβ and VEGF, which undergo early transcriptional changes in injured endothelial cells. Our results suggest that TGFβ and VEGF may play a crucial role in the development of endothelial cell injury leading to increased vascular permeability during shock-trauma.

Hepatic ischaemia-reperfusion injury from bench to bedside

BACKGROUND

Vascular occlusion to prevent haemorrhage during liver resection causes ischaemia-reperfusion (IR) injury. Insights into the mechanisms of IR injury gathered from experimental models have contributed to the development of therapeutic approaches, some of which have already been tested in randomized clinical trials.

METHODS

The review was based on a PubMed search using the terms 'ischemia AND hepatectomy', 'ischemia AND liver', 'hepatectomy AND drug treatment', 'liver AND intermittent clamping' and 'liver AND ischemic preconditioning'; only randomized controlled trials (RCTs) were included.

RESULTS

Twelve RCTs reported on ischaemic preconditioning and intermittent clamping. Both strategies seem to confer protection and allow extension of ischaemia time. Fourteen RCTs evaluating pharmacological interventions, including antioxidants, anti-inflammatory drugs, vasodilators, pharmacological preconditioning and glucose infusion, were identified.

CONCLUSION

Several strategies to prevent hepatic IR have been developed, but few have been incorporated into clinical practice. Although some pharmacological strategies showed promising results with improved clinical outcome there is not sufficient evidence to recommend them.

Ischemic preconditioning-induced hyperperfusion correlates with hepatoprotection after liver resection

AIM: To characterize the impact of the Pringle maneuver (PM) and ischemic preconditioning (IP) on total blood supply to the liver following hepatectomies.

METHODS: Sixty one consecutive patients who underwent hepatic resection under inflow occlusion were randomized either to receive PM alone (n = 31) or IP (10 min of ischemia followed by 10 min of reperfusion) prior to PM (n = 30). Quantification of liver perfusion was measured by Doppler probes at the hepatic artery and portal vein at various time points after reperfusion of remnant livers.

RESULTS: Occlusion times of 33 ± 12 min (mean ± SD) and 34 ± 14 min and the extent of resected liver tissue (2.7 segments) were similar in both groups. In controls (PM), on reperfusion of liver remnants for 15 min, portal perfusion markedly decreased by 29% while there was a slight increase of 8% in the arterial blood flow. In contrast, following IP + PM the portal vein flow remained unchanged during reperfusion and a significantly increased arterial blood flow (+56% vs baseline) was observed. In accordance with a better postischemic blood supply of the liver, hepatocellular injury, as measured by alanine aminotransferase (ALT) levels on day 1 was considerably lower in group B compared to group A (247 ± 210 U/I vs 550 ± 650 U/I, P < 0.05). Additionally, ALT levels were significantly correlated to the hepatic artery inflow.

CONCLUSION: IP prevents postischemic flow reduction of the portal vein and simultaneously increases arterial perfusion, suggesting that improved hepatic macrocirculation is a protective mechanism following hepatectomy.

Indocyanine green R15 ratio depends directly on liver perfusion flow rate

BACKGROUND

Indocyanine green (ICG) is a synthetic dye that is widely used to evaluate liver function in critically ill patients, before liver resection or after liver transplantation. Controversy still exists about the impact exerted on the ICG ratio after 15 min (ICG R15) by differences in liver perfusion rates, hyperdynamic states, or patient cardiac output. We studied the role of different liver perfusion rates on the ICG R15 ratio in a normothermic extracorporeal liver perfusion system under standardized conditions.

METHODS

Livers from landrace pigs (40-50 kg) were perfused with fresh porcine blood. Normal and high perfusion rates were defined as 1 ml and 2 ml/g liver/min, respectively. Perfusate pressure of the hepatic artery and portal vein were within the physiological range in both groups. According to manufacturer's instructions, 0.5 mg of ICG per kg was applied and the ICG R15 was calculated. Calculations were based on fifteen experiments in five liver perfusions. Bile production, liver function and histology were analyzed.

RESULTS

All perfusions were characterized by physiological bile production, lack of hepatocellular damage and normal histology. ICG R15 ratio in group I, perfused with 1 ml/g liver, was 18.9 +/- 6%. In group II, perfused with 2 ml/g liver, the ICG R15 ratio was 7.2 +/- 3%. The difference between groups 1 and 2 was statistically significant (p < 0.05).

CONCLUSION

ICG R15 is reliable within one group at defined perfusion rates. Doubled perfusion rates contribute to higher ICG clearance. For clinical application we would like to suggest considering cardiac output of the patient for interpretation of ICG ratios.

Protective effect of Sivelestat in a porcine hepatectomy model prepared using an intermittent Pringle method

The effect of Sivelestat, a neutrophil elastase inhibitor, on hepatic ischemia-reperfusion injury was examined in a pig hepatectomy model. An internal jugular vein-splenic vein bypass was prepared in male pigs and about 40% hepatic resection (left lobe) was performed under 15-min liver ischemia and 5-min intermittent reperfusion. Six animals received Sivelestat (10 mg/kg/h) intravenously and six control animals received physiological saline (10 mg/kg/h) from commencement of laparotomy. Hemodynamics, blood chemistry, aspartate aminotransferase (AST), lactate dehydrogenase (LDH), lactic acid, hyaluronic acid, nitrite/nitrate (NOS), and tumor necrosis factor-alpha (TNF-alpha) were compared between the groups. The effects of Sivelestat on NOS generation and expression of iNOS mRNA and TNF-alpha mRNA were also assessed in J774 cells. Expression of TNF-alpha mRNA in hepatic tissues was examined using RT-PCR. The blood pressure of control animals was significantly lower immediately and 3 h after ischemia-reperfusion, compared with that at commencement of laparotomy, whereas there was no decrease of blood pressure in animals administered Sivelestat. Serum AST (P=0.0045), NOS (P=0.0098), and TNF-alpha (P=0.041) levels were significantly lower 3 h after hepatectomy in animals receiving Sivelestat. Sivelestat inhibited NOS production in J774 cells, but did not inhibit expression of iNOS mRNA or TNF-alpha mRNA. In hepatic tissues, Sivelestat showed a greater tendency to inhibit expression of TNF-alpha mRNA and fewer TUNEL-positive cells were present in the hepatic sinusoidal endothelium after Sivelestat treatment, although these differences were not statistically significant. We conclude that Sivelestat inhibits production of TNF-alpha and NO by inhibiting neutrophil elastase, and thus reduces hepatic injury and stabilizes hemodynamics after ischemia-reperfusion.

Effect of the portacaval shunt on reperfusion injury after 65% hepatectomy in pigs

BACKGROUND

Portal flow diversion by portacaval shunts (PCS) has been shown to prevent primary graft nonfunction in liver transplantation using small-for-size grafts. In this study, we examine whether PCS can improve reperfusion injury after major hepatectomy in pigs.

MATERIALS AND METHODS

In 14 pigs, a partial PCS was constructed following 65% hepatectomy and 1 h of inflow ischemia. During 24 h of reperfusion, the shunt was either closed (group A, n = 7) or left open (group B, n = 7).

RESULTS

24 h after reperfusion, group A had higher levels of alanine aminotransferase (70 +/- 12 IU/l vs. 51 +/- 5.9 IU/l; p < 0.05), alanine aminotransferase per gram of liver remnant (0.41 +/- 0.07 IU/l/g vs. 0.21 +/- 0.05 IU/l/g; p < 0.05), prothrombin time (24.1 +/- 2.4 s vs. 14.3 +/- 2.9 s; p < 0.05), international normalized ratio (2.11 +/- 0.15 vs. 1.29 +/- 0.28; p < 0.05), hepatocyte necrosis scores and percentages of nuclei stained for proliferating cell nuclear antigen (52.57 +/- 8.9% vs. 36.71 +/- 6%; p < 0.05) compared to group B.

CONCLUSIONS

Partial portal flow diversion appears to attenuate reperfusion injury in a porcine model of major hepatectomy.

Protective Effect of Ischemic Preconditioning against Liver Injury after Major Hepatectomy Using the Intermittent Pringle Maneuver in Swine

OBJECTIVE

To investigate whether ischemic preconditioning (IP) protects the liver against ischemia-reperfusion injury (I/R-I) after major hepatectomy through intermittent hepatic pedicle clamping (IC) in a swine liver resection model.

BACKGROUND

Although many studies have reported a protective effect of IP against continuous hepatic ischemia, it has not been elucidated whether IP protects the liver against I/R-I after hepatectomy using IC. This is the first study to evaluate the effect of IP in a swine major hepatectomy model using IC.

METHODS

Pigs (n = 12) were divided into 2 groups (IP or non-IP). In the IP group, livers were subjected to IP (10 min ischemia and 10 min reperfusion) before liver resection using IC (15 min ischemia and 5 min reperfusion). A left hemihepatectomy was then performed using IC in both groups. Hemodynamic changes and plasma concentrations of aspartate aminotransferase, lactate dehydrogenase, lactic acid and hyaluronic acid were measured at 60, 120 and 180 min after hepatectomy. Apoptosis (TUNEL staining and electron microscopy), plasma tumor necrosis factor-alpha (TNF-alpha) and NO(2)(-)/NO(3)(-) were evaluated for 180 min after hepatectomy.

RESULTS

There were no significant differences in body weight, blood loss, resected liver weight, Pringle time or hemodynamic changes between the 2 groups. IP significantly reduced plasma aspartate aminotransferase levels for 180 min after hepatectomy (IP: 135.8 +/- 13.5 vs. non-IP: 199 +/- 16.8 IU/l; p = 0.018). In the non-IP group, apoptotic changes in sinusoidal endothelial cells were observed with increased plasma TNF-alpha levels. IP protected liver injury from increase in plasma TNF-alpha (p = 0.042). Significantly fewer apoptotic cells were seen in the IP than in the non-IP group (p = 0.002). Plasma levels of lactate dehydrogenase, lactic acid and NO(2)(-)/NO(3)(-) in the IP group tended to be lower than those in the non-IP group.

CONCLUSIONS

IP prior to hepatectomy with IC resulted in less hepatic injury and apoptotic cell death than in livers not subjected to IP. IP with IC has the potential to improve the clinical postoperative course of patients undergoing hepatectomy.

Ischemic preconditioning versus intermittent vascular occlusion in liver resections performed under selective vascular exclusion: a prospective randomized study

BACKGROUND

The aim of this study was to compare ischemic preconditioning with the intermittent vascular occlusion technique in liver resections performed under inflow and outflow occlusion.

METHODS

Fifty-four patients with resectable liver tumors assigned were randomly to undergo surgery with either ischemic preconditioning (IP group, n = 27) or with intermittent vascular occlusion (IVO group, n = 27). Both groups were compared regarding surgical parameters, aspartate transaminase levels, and apoptosis.

RESULTS

For warm ischemic time less than 40 minutes, no significant difference was noticed between the 2 groups apart from caspase-3 activity, which was higher in the IVO group than in the IP group (17.2 +/- 3.4 vs. 10.3 +/- 5.2, P < .05). When warm ischemia exceeded 40 minutes, the IP group showed higher levels in blood aspartate transaminase levels on day 3 (442 +/- 178 IU/L vs. 305 +/- 104 IU/L, P < .05) and higher caspase-3 levels (26.5 +/- 5.7 count/high-power field [hpf] vs. 20.7 +/- 3.6 count/hpf, P < .05) and apoptotic activity (28.5 +/- 7.5 count/hpf vs. 20.2 +/- 4.1 count/hpf, P < .05), as compared with the IVO group.

CONCLUSIONS

Although both techniques showed comparable efficacy for short ischemic times, intermittent vascular occlusion provided better cytoprotection when ischemia exceeded 40 minutes.

Major hepatic trauma: warm ischemic tolerance of the liver after hemorrhagic shock

BACKGROUND

The management of severe hepatic trauma frequently involves exposing the liver to varying periods of warm ischemia. The ischemic tolerance of the liver, in the setting of hemorrhagic shock (HS) and trauma, is presently unknown. We tested the hypothesis that warm ischemic tolerance of the porcine liver will be decreased following resuscitation from HS.

MATERIALS AND METHODS

Twenty-three Yorkshire pigs were divided into three groups: 1) hepatic ischemia alone (HI, n = 9); 2) hemorrhagic shock alone (HS, n = 3); and 3) hemorrhagic shock plus hepatic ischemia combined (HSHI, n = 11). Following reperfusion, a liver biopsy was obtained and serial blood chemistries were sampled.

RESULTS

Post-operative day 7 mortality was increased in the HSHI group (7/11) compared to the HI (0/9) group, P = 0.038. Notably, deaths did not result from acute liver failure, but rather from intra-operative hemodynamic collapse shortly following hepatic reperfusion. In addition, the HSHI group experienced significantly elevated lactic acid, serum creatinine and liver enzyme levels. Analysis of the liver biopsy samples is consistent with a more severe liver injury in the HSHI group.

CONCLUSIONS

The warm ischemic tolerance of the liver following resuscitation from HS is significantly decreased in this porcine model compared to HS or HI alone. Mortality was associated with acute intra-operative hemodynamic collapse occurring shortly after hepatic reperfusion.

Liver resective surgery: a multivariate analysis of postoperative outcome and complication

INTRODUCTION

Notwithstanding technical advances and high experience of liver resection of specialized centers, the rate of complications after surgical resection could be high. In this study, we analyzed causes and foreseeable risk factors linked to postoperative morbidity on the ground of data derived from a single center surgical population.

MATERIALS AND METHODS

From September 1989 to March 2005, 134 consecutive patients had liver resection for Hcc and 153 consecutive patients with liver metastasis (derived from either colorectal cancer or noncolorectal cancer) at our department. We performed 22 major hepatectomy, 20 left hepatectomy, 14 trisegmentectomy, 77 bisegmentectomy and/or left lobectomy, 74 segmentectomy, and 80 wedge resection.

RESULTS

In-hospital mortality rate was 4.5%, about 7% in Hcc cases and 2.6% in liver metastasis. Morbidity rate was 47.7%, caused by the rising of ascites (10%), temporary impairment liver function (19%), biliary fistula (6%), hepatic abscess (25%), hemoperitoneum (10%), and pleural effusion (30%) sometimes combined each other. Some variables, associated with the technical aspects of surgical procedure, are responsible of the rising of complication as: Pringle maneuver length of more than 20 minutes (p=0.001); the type of liver resection procedure [major hepatectomy (p=0.02), left hepatectomy (p=0.04), trisegmentectomy (p=0.04), bisegmentectomy and/or left lobectomy (p=0.04)]; and the request of an amount of blood transfusion of more than 600 cc (p=0.04). Also, both liver dysfunction, in particular Child A vs B and C (p=0.01), and histopathological grading (p=0.01) are associated with a high rate of postsurgical complication in Hcc cases.

CONCLUSION

We make the following recommendations: every liver resection should be planned after intraoperative ultrasonography, anatomical surgical procedure should be preferred instead of wedge resection, and modern devices should be used, like Argon Beam and Ligasure dissector, to reduce the incidence of both intraoperative and postoperative bleeding and biliary leakage.

Randomized clinical trial of hepatectomy using intermittent pedicle occlusion with ischaemic intervals of 15 versus 30 minutes

Background

The optimal ischaemic interval during hepatectomy with intermittent pedicle occlusion (IPO) remains to be established. The aim of the present randomized clinical trial was to compare the short-term outcome of hepatectomy using IPO with an ischaemic interval of 15 versus 30 min.

Methods

Between October 2002 and September 2004, 108 consecutive patients scheduled to undergo hepatectomy without bilioenterostomy were enrolled. During liver transection, IPO was performed with an ischaemic interval of either 15 min with 5 min of reperfusion (standard group, SG) or 30 min with 5 min of reperfusion (prolonged group, PG). After randomization and subsequent exclusion of certain patients, 44 patients in the SG and 48 in the PG were analysed.

Results

The mean(s.d.) bilirubin ratio (serum total bilirubin level on day 2 after operation divided by the preoperative level) was 1·6(0·8) in the SG and 1·7(0·8) in the PG (P = 0·874). The transection area per unit transection time was significantly greater in the latter group (median (range) 1·0 (0·4–2·1) versus 0·8 (0·0–1·5) cm2/min; P = 0·046).

Conclusion

There was no difference in the bilirubin ratio when IPO was carried out for 30 or 15 min. By extension of IPO to 30 min, a greater resection area per unit time was possible with preservation of remnant liver function.

Outcome using hemihepatic vascular occlusion versus the pringle maneuver in resections limited to one hepatic section or less

Consensus is lacking concerning how to manage afferent vessels during hepatectomy, particularly as to the Pringle maneuver vs. selective hemihepatic clamping. Data for 81 hepatocellular carcinoma patients with chronic hepatitis or liver cirrhosis whose liver resection was limited to one section or less, including intraoperative data and postoperative liver function data, were analyzed retrospectively to compare two strategies. No significant differences of intraoperative data or postoperative clinical course were seen between the two groups, even in patients with chronic hepatitis or liver cirrhosis whose postoperative deterioration of liver function could be expected to be more than patients with a normal liver. The difference was evident only in serum alanine aminotransferase level on postoperative day 10 (mean +/- SEM, 64.5 +/- 5.1 IU in the Pringle group vs. 51.6 +/- 4.4 IU in the selective clamping group; P < 0.05). During liver resection limited to one section or less, even with underlying chronic hepatitis or cirrhosis, intermittent use of the Pringle maneuver preserved liver function to the same extent as selective clamping.

Alkaline phosphatase reduces hepatic and pulmonary injury in liver ischaemia -- reperfusion combined with partial resection

BACKGROUND

Lipopolysaccharides mediate inflammation in liver ischaemia-reperfusion (I/R) and partial liver resection (PHX). Bovine intestinal alkaline phosphatase (BIAP) detoxifies lipopolysaccharides by dephosphorylation and reduces inflammation in models of sepsis. This study examined the protective effects of BIAP administration in models of partial (70 per cent) liver I/R with or without partial resection of all non-ischaemic lobes during ischaemia (30 per cent).

METHODS

Male Wistar rats were divided into six groups: I/R + BIAP, I/R + saline, I/R + PHX + BIAP and I/R + PHX + saline, PHX only or sham laparotomy only. A single dose of BIAP (0.5 units/g) or vehicle (saline) was administered 5 min before reperfusion. Inflammatory response, and hepatic and pulmonary injury were assessed during 24 h of reperfusion.

RESULTS

I/R, with or without PHX, increased all markers of inflammation, and hepatic and pulmonary damage (P < 0.050 versus sham operation). I/R + PHX significantly increased release of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and hepatic neutrophil influx compared with I/R only (P < 0.050). BIAP treatment decreased hepatic wet/dry ratios, neutrophil influx and histopathological damage after I/R with or without PHX (P < 0.050), and also AST, ALT and interleukin (IL)-6 production after I/R + PHX (P < 0.050). BIAP treatment reduced the neutrophil influx after I/R, and pulmonary histopathological injury was decreased after I/R with or without PHX.

CONCLUSION

BIAP attenuates hepatic and pulmonary injury after partial liver I/R and PHX.

Extended liver resection and hepatic ischemia in pigs: a new, potentially reversible model to induce acute liver failure and study artificial liver support systems

BACKGROUND

Extended hepatectomy is a valid model for the study of acute liver failure. Since the porcine liver is comparable in size, morphology and anatomy to the human liver, we describe a technique employing hepatic ischemia and extended liver resection to induce acute liver failure in a porcine model as a means of studying bioartificial liver support.

METHOD

A subtotal (75-80% resection) extended left hepatectomy was performed in 7 pigs after 60 min warm ischemia of the future remnant liver. After resection, the animals were given the best supportive care and observed until death.

RESULTS

All animals died within 18-48 h, none as a result of surgical complications. Gross appearance of the liver showed severe steatosis of the right lateral lobe, and histology revealed severe coagulative necrosis of the whole lobule.

CONCLUSION

This technique of extended liver resection after hepatic ischemia in the porcine model may be useful for studies of potentially reversible acute liver failure and experimental bioartificial support.

Precoagulation minimizes blood loss during standardized hepatic resection in an experimental model

BACKGROUND

Precoagulation of liver tissue before transection is a novel concept in hepatic surgery. Comparative data with conventional techniques are lacking. This study tested the hypothesis that precoagulation results in reduced blood loss during hepatic transection.

METHODS

Precoagulation was performed with two different devices, the TissueLink floating ball (group 1) and a dissecting sealer (group 2), and compared with ultrasonic dissection (group 3). For each technique 12 partial liver resections were performed in six pigs. Blood loss per dissection surface area was the main outcome parameter.

RESULTS

The transected surface area was similar in all groups. Animals in groups 1 and 2 had significantly less blood loss than those in group 3 (3.6 and 1.3 versus 11.9 ml/cm2 respectively; P = 0.009 and P = 0.002). One pig in group 1 died as a result of wound dehiscence. In one animal in group 2 a gastric perforation was observed after death. In group 3 bile leakage occurred in two animals, and a large haematoma was observed on the transection surface in one animal after death.

CONCLUSION

Precoagulation of liver tissue before transection is associated with less blood loss compared with ultrasonic dissection.

Ischemic preconditioning versus intermittent vascular inflow control during major liver resection in pigs

Ischemic preconditioning (IPC) and intermittent vascular control (IVC) have been shown to reduce the number of ischemia/reperfusion injuries during liver resections with the Pringle maneuver. Our study aimed to compare the beneficial effect of these two modalities in relation to the duration of normothermic liver ischemia. A group of 24 Landrace pigs with a mean body weight of 25 to 30 kg were subjected to extended liver resection of more than 65%. Although, 12 animals underwent IPC (10 minutes of ischemia and 10 minutes of reperfusion), and subsequently the Pringle maneuver was applied for 90 minutes (n= 6) or 120 minutes (n= 6). Another 12 animals underwent liver resection by IVC (20 minutes of ischemia alternated with 5 minutes of reperfusion) for 60 minutes (n = 6) or 120 minutes (n = 6) of inflow vascular control. At 90 minutes of liver ischemia, the IPC group demonstrated lower levels of asportate aminotransferase (AST) (173 +/- 53 vs. 265 +/- 106 IU; p =0.089) and malondialdehyde (MDA) (2.60 +/- 1.03 vs. 5.33 +/- 2.25 micromol/L; p =0.022) and higher liver tissue cAMP (200 +/- 42 vs. 146 +/- 40 pmol/g wet wt, p = 0.04) compared to the IVC group. However, no pathologic differences were observed between the two groups. By contrast, at 120 minutes of liver ischemia, IVC proved to be more beneficial, reflected by lower levels of AST (448 +/- 135 vs. 857 +/- 268 IU; p = 0.006) and MDA (8.33 +/- 1.75 vs. 12.7 +/- 4.31 micromol/L; (p = 0.045), a higher cAMP level (127 +/- 10 vs. 97 +/- 31 pmol/g wet wt p = 0.045), and eventually less cellular necrosis (necrosis score 1.66 +/- 0.51 vs. 2.85 +/- 1.16; p = 0.04) compared to the IPC group. It appears that IPC should be employed when liver ischemia is anticipated to last less than 90 minutes, followed by IVC when the liver ischemia is expected to last 120 minutes.

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.

Remnant liver injury after hepatectomy with the pringle maneuver and its inhibition by an iNOS inhibitor (ONO-1714) in a pig model

BACKGROUND

Although hepatectomy is often performed with the Pringle maneuver, the problem of remnant liver injury is not fully solved. We examined the remnant liver injury of hepatectomy under the Pringle maneuver and its relation to inducible nitric oxide synthase (iNOS) in a pig hepatectomy model.

MATERIALS AND METHODS

Pigs were subjected to a total of eight Pringle maneuvers followed by re-perfusion. The pigs were divided into the following three groups: Control group; only Pringle maneuver, liver resection (LR) group; hepatectomy under the Pringle maneuver, and ONO group; and hepatectomy under the Pringle maneuver with an iNOS inhibitor (ONO-1714). We investigated the changes in serum aminotransferase (AST), lactate dehydrogenase (LDH), NO(2)(-)+NO(3)(-) (NOx), the hepatic tissue blood flow (HTBF), the cellular distribution of endothelial and inducible nitric oxide synthase, nitrotyrosine, infiltration of neutrophils, and thrombocyte-thrombi by immunohistochemistry.

RESULTS

The serum AST, LDH, NOx levels in the LR group were significantly higher than those in the Control group. The formation of iNOS, nitrotyrosine, thrombocyte-thrombi, and infiltration of neutrophils were recognized in the LR group. These findings were inhibited in the ONO group.

CONCLUSIONS

These results indicate that remnant liver injury appeared after hepatectomy with the Pringle maneuver. iNOS was involved in these injuries and the iNOS inhibitor attenuated the injury.

Mild hypothermia protects liver against ischemia and reperfusion injury

AIM: To determine whether mild hypothermia could protect liver against ischemia and reperfusion injury in pigs.

METHODS: Twenty-four healthy pigs were randomly divided into normothermia, mild hypothermia and normal control groups. The experimental procedure consisted of temporary interruption of blood flow to total hepatic lobe for different lengths of time and subsequent reperfusion. Hepatic tissue oxygen pressure (P_tiO₂) and aspartate aminotransferase (AST) values were evaluated, and ultrastructural analysis was carried out for all samples.

RESULTS: Serum AST was significantly lower, and hepatic P_tiO₂ values were significantly higher in the mild hypothermia group than in the normothermia group during liver ischemia-reperfusion periods (P = 0.032, P = 0.028). Meanwhile, the histopathologic injury of liver induced by ischemia-reperfusion was significantly improved in the mild hypothermia group, compared with that in the normothermia group.

CONCLUSION: Mild hypothermia can protect the liver from ischemia-reperfusion injury in pigs.

Hepatic resections using a water-cooled, high-density, monopolar device: a new technology for safer surgery

Several techniques and devices have recently been developed in an effort to allow safer liver resections and avoid intraoperative blood loss. The aim of this study was to analyze our initial experience with hepatic resections using a new water-cooled, high-density, monopolar device--the Tissuelink Monopolar Floating Ball (Tissuelink Medical, Inc., Dover, NH)--in order to avoid bleeding during hepatic surgery. We analyzed patients who underwent hepatic surgery between January and June 2003. Sex, age, type of disease, and type of surgical procedure, in association with the duration of the surgical procedure, blood loss, use of vascular clamping of the liver, length of hospital stay, morbidity, and mortality were analyzed. Seven minor liver resections, two major liver resections, and one total cystopericystectomy were performed with the use of this new device. Average blood loss was 150 ml (range 50 to 300 ml). No vascular clamping was used with the exception of one patient. No deaths were recorded. Morbidity included ascites in one case and pleural effusion in another. In conclusion, the Tissuelink Monopolar Floating Ball permitted excellent coagulation of the cut liver surface, thus avoiding bleeding and vascular clamping. As a result, postoperative morbidity and mortality were low.

Decrease in core liver temperature with 10°C by in situ hypothermic perfusion under total hepatic vascular exclusion reduces liver ischemia and reperfusion injury during partial hepatectomy in pigs

OBJECTIVE

We attempted to assess liver ischemia/reperfusion injury under a mild decrease in core liver temperature of 10 degrees C by in situ hypothermic perfusion during ischemia.

METHODS

Liver ischemia was induced in pigs by total hepatic vascular exclusion with concomitant in situ perfusion with hypothermic (4 degrees C) Ringer-glucose (cold perfused group, core liver temperature maintained at 28 degrees C), with normothermic (38 degrees C) Ringer-glucose (warm perfused group) or without in situ perfusion (control group).

RESULTS

In the cold perfused, warm perfused, and control groups, 24-hour survival was 5/5, 0/5, and 3/5, respectively. Hemodynamic parameters in the cold perfused group remained stable, whereas pigs in both other groups required circulatory support. Plasma AST and interleukin-6 levels were lower in the cold perfused group than in both other groups. Hepatocellular function was best preserved in the cold perfused group as indicated by complete recovery of bile production during reperfusion and no loss of indocyanine green clearance capacity. In both other groups, bile production and indocyanine green clearance capacity were reduced significantly. The hyaluronic acid uptake capacity of pigs in the cold perfused group or control group did not differ, indicating preserved sinusoidal endothelial cell function. Histopathologic injury scores during reperfusion were significantly lower in the cold perfused group when compared to both other groups.

CONCLUSIONS

A mild decrease in core liver temperature of 10 degrees C by in situ hypothermic liver perfusion during ischemia protects the liver from ischemia/reperfusion injury. This protection appears to be related to cooling of the liver rather than to the washout of blood during perfusion.

Endothelin-A receptor antagonist reduces microcirculatory disturbances and transplant dysfunction after partial liver transplantation

Endothelin-1 can induce microcirculatory disorders by mediating sinusoidal vasoconstriction, lowering the perfusion rate and promoting leukocyte adhesion, all of which may play a role in the pathogenesis of the damage sustained by partial liver transplants. In this pilot study, we investigated a selective endothelin-A receptor antagonist (Darusentan; Knoll GmbH, Ludwigshafen, Germany) for its potential influence on the microcirculation in the setting of partial liver transplantation. One hundred and forty isogeneic Lewis rats were divided into four groups: 1. partial liver transplantation (30% of the initial liver volume); 2. partial liver transplantation treated with Darusentan (1 mg/kg bodyweight intravenously) immediately before reperfusion; 3. full-size liver transplantation; and 4. sham operation. Subsequently, the liver microcirculation was evaluated by intravital microscopy, and survival, liver function, and morphology were followed up to the fourteenth day. Compared with full-size transplanted animals, rats subjected to partial liver transplantation without Darusentan (group I) displayed severe microcirculatory lesions characterized by a significantly decreased perfusion rate, increased leukocyte velocity, and increased leukocyte adhesion. Disintegration of endothelium and increased recruitment of Kupffer cells were frequent morphologic findings. The Darusentan-treated group II showed improved parameters of microcirculatory function and morphology as well as improved liver function. Microcirculatory disturbances play a key role in the pathogenesis of partial liver transplant dysfunction. Treatment with selective endothelin-A receptor antagonists represent a new therapeutic approach to improve the function of partial liver transplants by reducing microcirculatory lesions and their sequelae affecting sinusoidal endothelium and hepatocytes.

Hepatic ischemia-reperfusion syndrome after partial liver resection (LR): hepatic venous oxygen saturation, enzyme pattern, reduced and oxidized glutathione, procalcitonin and interleukin-6

The hepatic ischemia-reperfusion syndrome was investigated in 28 patients undergoing elective partial liver resection with intraoperative occlusion of hepatic inflow (Pringle maneuver) using the technique of liver vein catheterization. Hepatic venous oxygen saturation (ShvO2) was monitored continuously up to 24 hours after surgery. Aspartate aminotransferase, glutamate dehydrogenase, gamma-glutamyl transpeptidase, pseudocholinesterase, alpha-glutathione S-transferase, reduced and oxidized glutathione, procalcitonine, and interleukin-6 were serially measured both before and after Pringle maneuver during the resection and postoperatively in arterial and/or hepatic venous blood. ShvO2 measurement demonstrated that peri- and postoperative management was suitable to maintain an optimal hepatic oxygen supply. As expected, we were able to demonstrate a typical enzyme pattern of postischemic liver injury. There was a distinct decrease of reduced glutathione levels both in arterial and hepatic venous plasma after LR accompanied by a strong increase in oxidized glutathione concentration during the phase of reperfusion. We observed increases in procalcitonin and interleukin-6 levels both in arterial and hepatic venous blood after declamping. Our data support the view that liver resection in man under conditions of inflow occlusion resulted in ischemic lesion of the liver (loss of glutathione synthesizing capacity with disturbance of protection against oxidative stress) and an additional impairment during reperfusion (liberation of reactive oxygen species, local and systemic inflammation reaction with cytokine production). Additionally, we found some evidence for the assumption that the liver has an export function for reduced glutathione into plasma in man.

Impact of endothelin-1 on microcirculatory disturbance after partial hepatectomy under ischemia/reperfusion in thioacetamide-induced cirrhotic rats

BACKGROUND

Endothelin (ET)-1 contributes to hepatic ischemia and reperfusion (HIR) injury in normal liver. This study was conducted to clarify the role of ET-1 in HIR injury in cirrhotic state.

MATERIALS AND METHODS

Using thioacetamide-induced cirrhotic rats with spontaneous portosystemic shunt, we determined the changes in plasma aspartate aminotransferase (AST) levels, plasma and hepatic ET-1 values, 7-day survival rates, and hepatic oxygen saturation (SO(2)) by time-resolved spectroscopy as an indicator of hepatic microcirculation under intermittent or continuous total hepatic ischemia with subsequent partial hepatectomy.

RESULTS

Hepatic ET-1 levels in cirrhotic rats were significantly higher than those in noncirrhotic rats. Plasma and hepatic ET-1 levels at 1, 3 and 6 h of reperfusion after intermittent hepatic ischemia were significantly lower than those after continuous hepatic ischemia. In cirrhotic animals subjected to intermittent hepatic ischemia, the elevation of plasma AST levels at 1, 3 and 6 h of reperfusion and the decline in hepatic SO(2) at the end of 60-min hepatic ischemia and after reperfusion were significantly suppressed when compared with those subjected to continuous hepatic ischemia. Pretreatment with a nonselective endothelin receptor antagonist in continuous hepatic ischemia significantly ameliorated plasma AST levels and hepatic SO(2) values with less hepatic sinusoidal congestion, resulting in an improvement in the 7-day survival rate.

CONCLUSIONS

Continuous hepatic ischemia in the cirrhotic liver has disadvantages relating to microcirculatory derangement with more ET-1 production in partial hepatectomy. In liver surgery, pharmacological regulation of ET-1 production may lead to attenuation of reperfusion injuries for ischemically damaged cirrhotic liver.

Isquemia hepática normotérmica em ratos: estudo da lesão celular através do uso de clampeamento pedicular contínuo e intermitente

OBJETIVO: Avaliar as alterações bioquímicas decorrentes da isquemia hepática normotérmica, seguida de reperfusão em duas modalidades de clampeamento da tríade portal em ratos. MÉTODO: Trinta ratos Wistar machos pesando entre 250 e 320 gramas foram divididos em três grupos de 10 animais cada. Induzimos 40 minutos de isquemia hepática por clampeamento pedicular contínuo (grupo I) ou intermitente (grupo II). No grupo controle não houve clampeamento. Como parâmetro de lesão hepatocelular adotamos a concentração plasmática de: transaminase glutâmico oxalacética (TGO), transaminase glutâmico pirúvica (TGP) e lactato desidrogenase (LDH). Colhemos as amostras de sangue no início (T1) e no final da cirurgia (T2). Todos os animais foram submetidos ao mesmo tempo operatório: 60 minutos. RESULTADOS: Não houve diferença estatística nos valores iniciais (T1) das três enzimas nos três grupos. Todos apresentaram aumento significativo das enzimas do momento 1 (T1) para o momento 2 (T2). Houve diferença estatística no aumento médio de TGO e TGP entre os três grupos, sendo o maior aumento encontrado no grupo I e o menor, no grupo controle. Não houve diferença significativa, em relação à LDH, entre o grupo II e o grupo controle. No grupo I, entretanto, houve aumento significativo em relação aos demais. Conclusão: Comparado ao clampeamento contínuo, para um período total de 40 minutos de isquemia, o clampeamento da tríade portal em ratos realizado de forma intermitente, com ciclos de 10 minutos de isquemia e 5 minutos de reperfusão, provoca menor dano hepatocelular, o que foi constatado pela menor alteração enzimática.

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.

Safe upper limit of intermittent hepatic inflow occlusion for liver resection in cirrhotic rats

AIM: To evaluate the effects of varying ischemic durations on cirrhotic liver and to determine the safe upper limit of repeated intermittent hepatic inflow occlusion.

METHODS: Hepatic ischemia in cirrhotic rats was induced by clamping the common pedicle of left and median lobes after non-ischemic lobes resection. The cirrhotic rats were divided into six groups according to the duration and form of vascular clamping: sham occlusion (SO), intermittent occlusion for 10 (IO-10), 15 (IO-15), 20 (IO-20) and 30 (IO-30) minutes with 5 minutes of reflow and continuous occlusion for 60 minutes (CO-60). All animals received a total duration of 60 minutes of hepatic inflow occlusion. Liver viability was investigated in relation of hepatic adenylate energy charge (EC). Triphenyltetrazollum chloride (TTC) reduction activities were assayed to qualitatively evaluate the degree of irreversible hepatocellular injury. The biochemical and morphological changes were also assessed and a 7-day mortality was observed.

RESULTS: At 60 min after reperfusion following a total of 60 min of hepatic inflow occlusion, EC values in IO-10 (0.749 ± 0.012) and IO-15 (0.699 ± 0.002) groups were rapidly restored to that in SO group (0.748 ± 0.016), TTC reduction activities remained in high levels (0.144 ± 0.002 mg/mg protein, 0.139 ± 0.003 mg/mg protein and 0.121 ± 0.003 mg/mg protein in SO, IO-10 and IO-15 groups, respectively). But in IO-20 and IO-30 groups, EC levels were partly restored (0.457 ± 0.023 and 0.534 ± 0.027) accompanying with a significantly decreased TTC reduction activities (0.070 ± 0.005 mg/mg protein and 0.061 ± 0.003 mg/mg protein). No recovery in EC values (0.228 ± 0.004) and a progressive decrease in TTC reduction activities (0.033 ± 0.002 mg/mg protein) were shown in CO-60 group. Although not significantly different, the activities of the serum aspartate aminotransferase (AST) on the third postoperative day (POD₃) and P OD₇ and of the serum alanine aminotransferase (ALT) on POD₃ in CO-60 group remained higher than that in intermittent occlusion groups. Moreover, a 60% animal mortality rate and more severe morphological alterations were also shown in CO-60 group.

CONCLUSION: Hepatic inflow occlusion during 60 min for liver resection in cirrhotic rats resulted in less hepatocellular injury when occlusion was intermittent rather than continuous. Each period of 15 minutes was the safe upper limit of repeated intermittent vascular occlusion that the cirrhotic liver could tolerate without undergoing irreversible hepatocellular injury.

Hepatic ischemia-reperfusion injury

BACKGROUND

The morbidity associated with liver transplantation and major hepatic resections is partly a result of ischemia-reperfusion injury.

DATA SOURCES

The entire world literature on the subject was searched via Medline. Keywords included reperfusion injury, transplantation, liver resection, nitric oxide, endothelin, cytokines, Kupffer cells, ischemic/ischaemic preconditioning, and nuclear factor-kappa B.

CONCLUSIONS

An imbalance between endothelin and nitric oxide levels results in failure of the hepatic microcirculation at the onset of reperfusion. Activation of nuclear factor-kappa B in the liver promotes proinflammatory cytokine and adhesion molecule synthesis. These result in oxygen-derived free radical production and neutrophil recruitment, further contributing to cellular injury. Various therapeutic modalities acting on the above mediators have been successfully used to attenuate reperfusion injury in animal models of hepatic transplantation and resection. Application of the knowledge gained from animal models of hepatic ischemia-reperfusion to the clinical setting will improve the outcome of hepatic surgery.

Tissue oxygen pressure during prolonged ischemia of the liver

BACKGROUND

The potential role of hepatovenous back-perfusion in maintaining organ viability of the inflow-occluded liver has been reported with respect to aspects of tissue perfusion and energy metabolism. In the present study, the physiological differences between liver ischemia induced by portal triad clamping (PTC) and that induced by total hepatic vascular exclusion (THVE) were investigated in a porcine disease model, with special reference to changes in tissue oxygen pressure (PtO(2)) of the liver.

MATERIALS AND METHODS

Twelve female pigs were used for induction of 60 min of normothermic liver ischemia. They were assigned to two groups: a PTC group (n = 6) and a THVE group (n = 6). PtO(2) was measured before, during, and after the ischemic period at two different points in the middle lobe: on the central side close to the hepatovenous confluence and on the peripheral side close to the gallbladder bed.

RESULTS

Although central PtO(2) decreased during ischemia in both groups, PTC group values at 40 and 60 min of ischemia remained significantly higher than THVE group values (60 +/- 28 and 42 +/- 21 mmHg vs 11 +/- 5 and 13 +/- 3 mmHg, respectively; means +/- SD). Peripheral PtO(2) in the PTC group during ischemia was low in comparison to corresponding central PtO(2) values.

CONCLUSION

Oxygen supply to the tissue via hepatovenous reflux may contribute to maintaining organ viability under prolonged inflow occlusion of the liver.

Hepatobiliary surgery

The transformation of liver and biliary tract surgery into a full speciality began with the application of functional anatomy to segmental surgery in the 1950's, reinforced by ultrasound and new imaging techniques. The spectrum of gall-stone disease encountered by the hepatobiliary surgeon has changed with the laparoscopic approach to cholecystectomy. There is increased need for conservation techniques to repair the bile duct injuries that arise more often in the laparoscopic approach to cholecystectomy. These and other surgical interventions on the bile ducts should be selected as a function of risk versus benefit in relation to the patient's requirements and the institutional expertise. Bile duct cancers, including hilar cholangiocarcinoma, and gallbladder cancers have a dismal reputation, but evidence is accumulating for better survivals from aggressive approaches performed by specialist hepatobiliary surgeons. Hepatic surgery has increased in safety and effectiveness, largely due to the segmental approach, but also to experience with techniques for vascular control and exclusion used in liver transplantation. Techniques such as portal vein embolisation, which induces hypertrophy of the future remnant liver, percutaneous local tumour destruction using cryotherapy or radiofrequency tumour coagulation and more effective chemotherapy are beginning to increase the number of patients who can undergo curative resection. In liver transplantation, segmental surgery has been applied to graft reduction and to split liver grafts, and is opening new perspectives for living donor transplantation. Today the limitation to survival in primary and metastatic liver cancer lies not in the surgical technique but in the difficulty of dealing with microscopic and extrahepatic disease. Progress in these fields will enable the hepatobiliary surgeon to further extend the possibilities for proposing curative resections.