Agathi Pafiti

Development of a Porcine Model of Post-Hepatectomy Liver Failure

BACKGROUND The aim of this study was to develop a porcine model of post-operative liver failure (POLF) that could accurately reproduce all the neurological and metabolic parameters of the corresponding clinical syndrome that may develop after extensive liver resections. METHODS In our model, we induced POLF by combining extended left hepatectomy and ischemia of the small liver remnant of 150 min duration. Subsequently, the remnant liver parenchyma was reperfused and the animals were closely monitored for 24 h. MATERIALS Twelve Landrace pigs (weight 25-30 kg) were randomly assigned in two groups; eight of them constituted the experimental group, in which POLF was induced (POLF group, n = 8), whereas the rest of them (n = 4) were included in the control group (sham laparotomy without establishment of POLF). RESULTS (MEANS ± SD): All POLF animals gradually developed neurological and biochemical signs of liver failure including, among many other parameters, elevated intracranial pressure (24.00 ± 4.69 versus 10.17 ± 0.75, P = 0.004) and ammonia levels (633.00 ± 252.21 versus 51.50 ± 9.49, P = 0.004) compared with controls. Histopathologic evaluation of the liver at the end of the experiment demonstrated diffuse coagulative necrosis and severe architectural distortion of the hepatic parenchyma in all POLF animals. CONCLUSION Our surgical technique creates a reproducible porcine model of POLF which can be used to study the pathophysiology and possible therapeutic interventions in this serious complication of extensive hepatectomies.

Reversal of Experimental Posthepatectomy Liver Failure in Pigs: A New Application of Hepatocyte Bioreactors

Postoperative liver failure remains a major cause of morbidity and mortality after extensive hepatectomies. This study aims to evaluate the effectiveness of a hepatocyte bioreactor in the treatment of experimental post-hepatectomy liver failure. Our experimental model included a combination of a side-to-side portacaval shunt, occlusion of the hepatoduodenal ligament for 150 min, 70% hepatectomy, and reperfusion. Following the development of liver failure, 12 pigs were randomized into a control group (n = 6) and a treatment group (n = 6). Both groups underwent extracorporeal perfusion through a plasma separation device, a membrane oxygenator, and two parallel bioreactors. In the latter group, the bioreactors were loaded with 10 billion fresh hepatocytes, isolated from a donor pig. Following hepatocyte treatment, all animals were maintained for 24 h under mechanical ventilation, with intravenous fluid and glucose supplementation. Hemodynamic parameters, intracranial pressure, and biochemical parameters were measured. Liver biopsies were obtained during the 24-h autopsy. The extracorporeal circuit was well-tolerated hemodynamically. Treated animals had lower intracranial pressure compared with controls (at 24 h, 15 ± 3.1 vs. 22 ± 3.5 mm Hg, P = 0.006). Plasma ammonia in treated animals was lower compared with controls at 12 h (100 ± 29 vs. 244 ± 131 µmol, P = 0.026). Liver histological study showed decreased necrosis and increased regeneration activity in treated animals compared with controls. Treatment through an extracorporeal hepatocyte bioreactor attenuates brain edema and improves histological and functional parameters of the liver remnant of pigs with posthepatectomy liver failure.

Early myocardial injury is an integral component of experimental acute liver failure – a study in two porcine models

Introduction There is accumulating clinical evidence that acute liver failure may be regularly associated with myocardial injury. To test this hypothesis in a standardized experimental setting, we used two porcine models of ALF. Material and methods In 14 domestic pigs ALF was induced by either a) surgical devascularization of the liver (DV group, n = 7), or b) partial (70-75%) hepatectomy and ischaemia/reperfusion of the liver remnant for 150 min (I/R group, n = 7). Four additional animals constituted the sham operation group. All animals were monitored for a 12-h period, at the end of which their hearts were harvested. Plasma troponin I (cTnI) and malondialdehyde (MDA) were measured before the operation (baseline) and at 6 h and 12 h postoperatively. The harvested hearts were histologically analysed, appointing a score from 0 (no injury) to 3 (maximum injury) to selected injury indicators. Results In the sham group, all cTnI measurements and total myocardial injury score were zero in all animals. In both ALF groups, plasma cTnI levels increased by the 6th and remained elevated up to the 12th postoperative hour (p < 0.01 vs. sham animals). Total myocardial injury score and total histological score revealed some extent of myocardial injury. The rise of MDA levels suggests an underlying oxidative mechanism. Conclusions Our study provides direct evidence of early myocardial injury in the setting of acute liver failure in pigs. The mechanism of injury remains to be elucidated.

Peritoneal Albumin Dialysis as a Novel Approach for Liver Support: Study in a Porcine Model of Acute Hepatic Failure

Artificial liver support gained considerable interest in recent years due to the development of various albumin dialysis systems, which prolong survival of some patients with acute liver failure (ALF). Τhis study aims to examine the role of peritoneal albumin dialysis in a postoperative ALF model. ALF was induced in 14 female Landrace pigs by a combination of major liver resection (70-75% of total parenchyma) and ischemic-reperfusion injury on the liver remnant. Animals were randomly divided in two groups (n = 7 each). Both were monitored for 12 h of reperfusion and received peritoneal dialysis for 6 h, beginning 6 h after reperfusion. The albumin group received an albumin-rich solution and the control group received albumin-free solution. The control group gradually developed intracranial hypertension, whereas, in the albumin group, rise in the intracranial pressure was substantially attenuated (P < 0.01, t = 12 h). Albumin-treated animals had significantly lower levels of ammonia (P < 0.01), total bile acids (P < 0.01), free fatty acids (P < 0.05), lactate (P < 0.01), and total bilirubin (P < 0.05). Liver malondialdehyde and protein carbonyl were significantly reduced (P = 0.007 and P = 0.001 at t = 12 h) after albumin dialysis. Results suggest that this method may become a useful adjunct in the management of ALF, thus, justifying further study.

Desferrioxamine Attenuates Pancreatic Injury after Major Hepatectomy under Vascular Control of the Liver: Experimental Study in Pigs

Introduction. Pancreatic injury can manifest after major hepatectomy under vascular control. The main mechanism involved seems to be remote oxidative injury due to “spillage” of reactive oxygen species and cytokines from the liver. The aim of this study is to evaluate the role of desferrioxamine in the prevention of pancreatic injury following major hepatectomy. Methods. Twelve Landrace pigs were subjected to a combination of major hepatectomy (70–75%), using the Pringle maneuver for 150 minutes, after constructing a porta-caval side-to-side anastomosis. The duration of reperfusion was 24 hours. Animals were randomly divided into a control group (n = 6) and a desferrioxamine group (DFX, n = 6). DFX animals were treated with continuous IV infusion of desferrioxamine 100 mg/kg. Pancreatic tissue injury, c-peptide and amylase concentrations, and pancreatic tissue oxidative markers were evaluated. Results. Desferrioxamine-treated animals showed decreased c-peptide levels, decreased acinar cell necrosis, and decreased tissue malondialdehyde levels 24 hours after reperfusion compared with the control group. There was no difference in portal pressure or serum amylase levels between the groups. Conclusions. Desferrioxamine seems to attenuate pancreatic injury after major hepatectomy under vascular control possibly by preventing and reversing production and circulation of oxidative products.

Insulin Metabolism and Assessment of Hepatic Insulin Extraction During Liver Regeneration. A Study in a Rat Model

ABSTRACT Background: Liver regeneration is a complex procedure in which insulin metabolism has been implicated. The aim of this experimental study was to evaluate the role of insulin in rat hepatic regeneration following major hepatectomy (70%), employing an isolated perfused rat liver (IPRL) model to assess the extraction of insulin from the regenerating liver. Methods: Eighty-six male rats were randomized in 9 groups. A group of rats was studied at postoperative day (POD) 1 having a sham operation while control rats had no operation. All other animals were subjected to 70% hepatectomy. In phase B, at POD 1, 2, 3, 5, 7, and 14, the IPRL was applied. The regenerating liver was perfused with insulin (450 mu/ml) at a flow of 1.4 ml/gr liver/min for 20 min. Animal weight, liver weight, glucose, lactate, aspartate transferase (AST), alanine transferase (ALT), total bilirubin, albumin, prothrombin time (PT), insulin clearance, and tissue proliferating cell nuclear antigen (PCNA) expression were recorded. Results: We observed reduction of the livers biochemical activities resulting in increase of AST (684%), ALT (532%), PT (27.7%), international normalized ratio (72%), and total bilirubin (82.8%) at first POD, while a normalization of the essential livers functions occurs at fifth POD. Endogenous insulin concentration increased, while insulin extraction by the liver was reduced at the first POD in animals who underwent hepatectomy (13.94 ± 0.8 vs 7.97 ± 1.80 u/ml, p = 0.0005 and 71 ± 9.9 vs 165.88 µU/gr liver/min, respectively, p = 0.0005). Conclusions: Insulin seems to take part in hepatic regeneration, as the pancreas increases insulin production and the liver absorbs less despite the reduced hepatic mass and function.

N-Acetylcysteine and Desferoxamine Reduce Pulmonary Oxidative Stress Caused by Hemorrhagic Shock in a Porcine Model

ABSTRACT Aim of the study: To investigate the pulmonary oxidative stress and possible protective effect of N-Acetylcysteine (NAC) and Desferoxamine (DFX)in a porcine model subjected to hemorrhagic shock. Materials and Methods: Twenty-one pigs were randomly allocated to Group-A (sham, n = 5), Group-B (fluid resuscitation, n = 8) and Group-C (fluid, NAC and DFX resuscitation, n = 8). Groups B and C were subjected to a 40-min shock period induced by liver trauma, followed by a 60-min resuscitation period. During shock, the mean arterial pressure (MAP) was maintained at 30–40 mmHg. Resuscitation consisted of crystalloids (35 mL/kg) and colloids (18 mL/kg) targeting to MAP normalization (baseline values ± 10%). In addition, Group-C received pretreatment with NAC 200 mg/kg plus DFX 2 g as intravenous infusions. Thiobarbituric Acid Reactive Substances (TBARS), protein carbonyls and glutathione peroxidase (GPx) activity were determined in lung tissue homogenates. Also, histological examination of pulmonary tissue specimens was performed. Results: TBARS were higher in Group-B than in Group-A or Group-C: 2.90 ± 0.47, 0.57 ± 0.10, 1.78 ± 0.47 pmol/μg protein, respectively (p < 0.05). Protein carbonyls content was higher in Group-B than in Group-A or Group-C: 3.22 ± 0.68, 0.89 ± 0.30, 1.95 ± 0.54 nmol/mg protein, respectively (p > 0.05). GPx activity did not differ significantly between the three groups (p > 0.05). Lung histology was improved in Group-C versus Group-B, with less alveolar collapse, interstitial edema and inflammation. Conclusion: NAC plus DFX prevented the increase of pulmonary oxidative stress markers and protein damage after resuscitated hemorrhagic shock and had beneficial effect on lung histology. NAC/DFX combination may be used in the multimodal treatment of hemorrhagic shock, since it may significantly prevent free radical injury in the lung.