- Email: [email protected]
Development of a Standardized Model for Liver Failure in Pigs: Anatomopathophysiologic Findings After Extended Liver Resection
Development of a Standardized Model for Liver Failure in Pigs: Anatomopathophysiologic Findings After Extended Liver Resection D. Pagano, F. di Francesco, G.J. Echeverri, M. de Martino, C. Ricotta, G. Occhipinti, V. Pagano, E. Oliva, M.I. Minervini, B.G. Gridelli, and M. Spada ABSTRACT Eighteen pigs weighing a mean 19 ⫾ 4 kg, were divided into group 1 (n ⫽ 2), that underwent resection of the left lateral lobe, group 2 (n ⫽ 2), resection of the left median and right median lobes; and group 3 (n ⫽ 18), resection of the left lateral, left median, right median, and right lateral lobes. All animals were followed for 5 days. Liver failure (n ⫽ 8) leading to animal death within 3 days after surgery was observed in 65% of group 3, whereas no group 1 or 2 animal experienced liver insufficiency. Multivariate analysis revealed that the extent of liver resection expressed as a percentage of total body weight ⬍2.3%, international normalized ratio ⬎ 1.6 as postoperative day 2, serum bilirubin ⬎ 4.2 on postoperative day 2, and serum lactates ⬎ 9 mmol/L after resection were independent predictors of liver failure (P ⬍ .05). The number of resected liver lobes was not a good predictor of liver failure in swine, whereas the extent of resection expressed as a percentage of total body weight was an independent predictor of early liver failure. A resected liver-to-body weight ratio ⬎2.3% was associated with a 65% probability of developing liver insufficiency. This parameter may be useful when developing a model of liver failure after extended liver resection in swine. xtended hepatic resection is the ideal treatment for a wide range of liver lesions. This surgical proceduce has been progressively improved by developing devices for parenchymal transection and strategies to increase the remnant liver volume after extended resection, such as portal vein embolization.1,2 Morbidity and mortality increase according to the degree of reduction of remnant liver volume, at least in part related to hemodynamic changes.3,4 Portal vein flow and pressure are the main triggers for hepatic regeneration; but portal overflow produce portal hypertension and liver damage.4,5 Moreover, many perioperative indicators have been proposed as simple standardized ways to predict outcomes after liver resection.6 In swine, the extension of liver resection can be expressed according to the resected liver lobes or segments, but this does not necessarily correlate with the development of liver failure.7 The aim of the present study was to create a large animal model of early liver impairment after extended hepatic resection to facilitate development of surgical, pharmacologic, and cellular treatments and to identify preoperative, intraoperative, and early postoperative predictors of liver failure.
E
MATERIALS AND METHODS Eighteen large white female Landrace pigs weighing 19 ⫾ 4 kg received care procedures in accordance with The Principles of Laboratory Animal Care and The Guide for the Care and Use of Laboratory Animals. The hosts were divided into 3 groups according to the amount of resected parenchyma: group 1, left lobe (n ⫽ 2); group 2, left and laft median lobes (n ⫽ 2); and group 3, left, median, and 50% of the right lobe (n ⫽ 14). Anesthesia was induced by propofol (6 mg/kg) and fentanyl (3 g/kg) administraFrom the Department of Abdominal and Transplantation Surgery, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (D.P., F.d.F., G.J.E., M.d.M., C.R., G.O., B.G.G., M.S.), University of Pittsburgh Medical Center in Italy, Palermo, Italy; Research and Development in the Mediterranean Basin Foundation (E.O.), Palermo, Italy; and Division of Transplantation, Department of Pathology (M.I.M.), and Department of Surgery (B.G.G, M.S.), University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. Address reprint requests to Macro Spada, MD, PhD, Instituto Mediterraneo per i Trapianti e Terapie ad Alta Specializzazione, University of Pittsburgh Medical Center in Italy, Via E. Tricomi N. 1, 90127 Palermo, Italy. Tel: ⫹390912192111; Fax: ⫹390912192400. E-mail: [email protected]
© 2012 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/–see front matter http://dx.doi.org/10.1016/j.transproceed.2012.06.009
Transplantation Proceedings, 44, 2029 –2032 (2012)
2029
2030
PAGANO, DI FRANCESCO, ECHEVERRI ET AL After a midline laparotomy, was performed, a collateral of the portal vein was cannulated to measure the portal vein pressure. Flow measurements were performed on the portal vein and hapatic artery after then isolation by dissection. The pedicle of each lobe was isolated via an extraparenchymal approach. The parenchymal transection was performed by a clamp-crush technique with concomitant hepatic vein identification, suture, and transection. The weighed resected liver parenchyma was notuse to calculated the liver-to-body weight (RWBW) ratio: liver resected weight (g) ⫻ 100/total body weight (g). Arterial blood pressure (ABP), mean arterial pressure (MAP), heart rate (HR), and central vein pressure (CVP) were monitored continuously, and portal vein pressure (PVP), hepatic artery, and portal vein flows were measured before and after the liver resection. Flow measurements performed using ultrasound transit time flow probes (Transonic Systems, Maastricht, The Netherlands) were recorded using a computer (Model 316T; Iworx/CB Sciences, Dover, NH, USA). The animals were followed for 5 days we killed them. Postoperatively, we monitored on a daily basis the clinical signs of liver impairment aspatate transaminase, (AST), alanine transaminase bilirubin (ALT), intenational normalized ratio (INR), and lactic acid. After killing the animals, we performed a complete examination of the major organs of the abdomen and thorax, measured the animal and remnant liver weights, and procured hepatic tissue samples for histologic studies (hematoxylin-eosin) satining. The significance of continuous metric differences was determined by Student t test. Categoric values were compared using chi-square (2) test. Logistic regression analysis was performed to determine the association of various factors with the onset of liver failure; P values ⬍.05 were considered to be significant.
Fig 1. (A) Liver resected weight expressed as a percentage of total body weight (RWBW). Group 1 (blue) and group 2 (red): 1.71 ⫾ 0.01% and 1.86 ⫾ 0.12% respectively, (P ⬎ .05); 2.25 ⫾ 0.22% in all Group 3 (green) pigs (P ⬎ 0.05) in 2.29 ⫾ 0.07% in the liver failure subgroup (lighter green) and 2.18 ⫾ 0.11% in animals who did not develop liver failure (intermediate green) without statistical significance when compared Group 3 subgroup (P ⬎ 0.05). (B) Remnant liver weight expressed as percentage of body weight (LWBW): was 0.9 ⫾ 0.08% in the liver failure subgroup and 1.70 ⫾ 0.24% in animals who did not develop liver failure, with statistical signicance (P ⬍ .05).
tion as intravenons (IV) boluses into marginal ear vein, followed by endotracheal intubation with maintenance using with positive pressure mechanical ventilation with oxygen and isoflurance. Continued neuromuscular block during surgery was obtained by administration of cisatracurium by IV bolus (0.2 mg/kg) followed by continuous IV infusion (0.06 mg/kg/h).
RESULTS
The survival rates were 100% in group 1, 100% in group 2, and 36% in group 3. Among the group 3, 14 animals survived to the end of the study (subgroup 3A) and 9 succumbed on postoperative day(POD) 1–3, owing to liver failure (subgroup 3B). Mean body weights of group 1 and 2 were 19 ⫾ 7 kg and 13 ⫾ 0.3 kg, respectively versus 20 ⫾ 3 kg in group 3. In this last group they were 19 ⫾ 4 kg in subgroup; B and 20 ⫾ 3 kg in subgroup A. RWBW was 1.71 ⫾ 0.01 and 1.86 ⫾ 0.12 in groups 1 and 2, respectively versus 2.25 ⫾ 0.22 in group 3, including 2.29 ⫾ 0.07 in subgroup 3A and 2.18 ⫾ 0.11 in subgroup 3B. Figure 1A shows differences in RWBW among the groups. No differences in MAP, HR, or CVP were observed among the groups. Table 1 shows actual and differential (PVPs) before and after liver resection as well as the potocaval pressure gradient (PCG). Group 3 showed hepatic artery flow
Table 1. Portal Vein Pressure (PVP) and Portocaval Gradient (PCG) Pressure Before and After Liver Resection PVP Before Resection (mm Hg)
Group 1 Group 2 Group 3 Subgroup 3A, no liver failure Subgroup 3B, liver failure
9,50 ⫾ 4.95 7,00 ⫾ 4,24 10,10 ⫾ 3,14 11,40 ⫾ 3,78 8,80 ⫾ 1,92
PVP After Resection (mm Hg)
⌬PVP (mm Hg)
PCG Before Resection (mm Hg)
PCG After Resection (mm Hg)
15,00 ⫾ 2,83 10,00 ⫾ 4,24 17,80 ⫾ 4,98 17,00 ⫾ 6,20 18,60 ⫾ 3,97
5,50 ⫾ 2,12 3,00 ⫾ 0,00 7,70 ⫾ 6,15 5,60 ⫾ 7,77 9,80 ⫾ 3,70
1,50 ⫾ 0,71 1,50 ⫾ 0,71 2,00 ⫾ 2,40 3,20 ⫾ 2,49 0,80 ⫾ 1,79
4,50 ⫾ 2,12 2,00 ⫾ 1,41 6,90 ⫾ 3,98 6,20 ⫾ 4,60 7,60 ⫾ 3,65
No statistical fast significance between all combinations and all groups.
PIG MODEL OF LIVER FAILURE
2031
RWBW (P ⫽ .03). Multivariate analysis using logistic regression for all variables associated with the onset of liver failure revealed the significant independent variables predicting the onset of liver failure after extended hepatic resection to be RWBW (P ⫽ .005), serum INR on POD 2 (P ⫽ .01), serum total bilirubin on POD 1 (P ⫽ .01), and serum lactate at the end of the resection (P ⫽ .02); (Table 2), none of which had a robust 95% confidence interval. DISCUSSION
Fig 2. Postoperative liver function tests. (A) INR, bilirubin (BIL), lactates (LAC); (B) aspartate transmin (AST), and alanine transmine (ALT). In group 3B, the onset of liver failure was associated with a significant increase of INR on POD 2 (P ⫽ .04), total BIL on POD 1–3 (P ⫽ .02), AST on POD 2 and 3 (P ⫽ .05), and LAC at the end of liver resection (P ⫽ .04).
of 156 ⫾ 32 mL/min before and 5.3 ⫾ 2.2 mL/min after resection (P ⫽ .004) and portal vein flow of 360 ⫾ 80 mL/min before and 170 ⫾ 50 mL/min at the end of the resection. Laboratory tests in group 3, subgroup 3A and 3B, are depicted in Fig. 2. Remnant liver weight expressed as percentage of body weight (LWBW) at the time of necropsy is showed in Fig 1B. The light-microscopic findings of the liver before and after liver resection were similar among all the groups with exception of significant more severe portal and septal edema, endothelial cell detachment, necrosis, and mitosis in subgroup 3A versus subgroup 3B. Upon univariate analysis, variables associated with the onset of liver failure were serum INR on POD 2 (P ⫽ .04), serum total bilirubin on POD, 1 (P ⫽ .02), 2 (P ⫽ .02), and 3 (P ⫽ .02), serum AST on POD, 3 (P ⫽ .02) and 3 (P ⫽ .05), serum lactic acid at the end of liver resection (P ⫽ .04), and
Previously developed large animal models to study hepatic damage after liver resection have shown poor, correlations with the extent of resection. In the rescent study, we sought study, we sought to created an easy to reproducible model of early liver impairment after extended liver resection. Liver failure developed only among group 3 animals, which underwent extended resection of the left, median, and 50% of the right lobes, leaving only the remaining right lateral and caudate lobes surrounding the inferior vena cava. We found that an RWBW ⬎2.3% (P ⬍ .005), a persistently high bilirubin level ⬎4.6 mg/dL in POD 2 (P ⬍ .05), a high INR ⬎1.64 on POD 2 (P ⬍ .005), and a lactate level ⬎8.9 mmol/L after surgery (P ⬍ .005) tended to be independent predictive factors for the developing recent of liver failure after extended hepatectomy. Although PVP, after surgery and differences between PVP after and before resection and PCG were increased among hosts displaying liver failure, they were not significant predictors of liver impairment (P ⬎ .05). The subgroup that developed liver failure showed histologic significantly greater scores in endothelial cell detachment, portal and septal edema, as well as necrosis (P ⬍ .05), which may have related to increased portal vein flow causing periportal sinusoidal endothelial injury. There was a significant reduction in hepatic artery blood flow, but not in portal venous flow. After 95% liver resection in group 3, 8 pigs died, clearly showing the difficulties associated with this procedure, results that were similar to previous earlier reports. In our experience, the technique of resection of ⱕ80% was simple and relatively bloodless owing to control of the portal vein and hepatic artery vessels before the resection, but it did not produce liver failure. In the present series, 5 pigs never developed liver failure, and 8 animals developed liver failure; thus 13/18 pigs (72.2%) displayed a major metabolic imbalance that caused irreversible liver malfunction and/or immediate death. In conclusion, the extended hepatectomy we performed caused rapid onset of liver failure, that was easy to repro-
Table 2. Actual Values of Liver Resected Weight Expressed as a Percentage of Total Body Weight (RWBW), INR, Bilirubin (BIL), and Lactates (LAC), with Odds Ratios from Multivariate Analysis and 95% Confidence Intervals, Mean ⴞ SD
RWBW LAC INR BIL
Actual Values
Odds Ratios
Standard Error
2,29 ⫾ 0,12 5,20 ⫾ 2,08 1,64 ⫾ 0,34 4,67 ⫾ 2,87
18.4561 1.25084 2.80106 1.03222
11.54301 0.24992 6.17866 0.28181
95% Confidence Interval
0.98311 0.84554 0.37129 0.60448
6.53861 1.85043 2.10121 1.76263
2032
duce and useful to study liver damage in pigs. The main factor led to early liver failure was a resection of ⬎2.3% of the animal’s body weight and failure of recovery of liver function tests in the first days. ACKNOWLEDGEMENTS The authors thank Warren Blumberg for his critical review of the paper and Pietro Tagliareni for his technical support on histology specimens.
REFERENCES 1. Khan AZ, Bann SD, Pitsinis V, et al: Refining the technique of hepatic parenchymal transection: combined saline-linked radiofrequency precoagulation and ultrasonic aspiration. Hepatogastroenterology 54:1167, 2007
PAGANO, DI FRANCESCO, ECHEVERRI ET AL 2. Nagino M, Kamiya J, Nishio H, et al: Two hundred forty consecutive portal vein embolizations before extended hepatecomy for biliary cancer: surgical outcome and long-term follow-up. Ann Surg 243:364, 2006 3. Kubota K, Makuuchi M, Kusaka K, et al: Measurement of liver volume and hepatic functional reserve as a guide to decision making in resectional surgery for hepatic tumors. Hepatology 26:1176, 1997 4. Wang HS, Ohkohchi N, Enomoto Y, et al: Excessive portal flow causes graft failure in extremely small-for-size liver transplantation in pigs. World J Gastroenterol 28:11:6954, 2005 5. Lida T, Yagi S, Taniguchi K, et al: Improvement of morphological changes after 70% hepatectomy with portocaval shunt: preclinical study in porcine model. J Surg Res. 143:238, 2007 6. Mullin EJ, Metcalfe MS, Maddern GJ: How much resection is too much? Am J Surg 190:876, 2005 7. Court FG, Laws PE, Morrison CP, et al: Subtotal hepatectomy: a porcine model for the study of liver regeneration. J Surg Res 116:181, 2006
E
MATERIALS AND METHODS Eighteen large white female Landrace pigs weighing 19 ⫾ 4 kg received care procedures in accordance with The Principles of Laboratory Animal Care and The Guide for the Care and Use of Laboratory Animals. The hosts were divided into 3 groups according to the amount of resected parenchyma: group 1, left lobe (n ⫽ 2); group 2, left and laft median lobes (n ⫽ 2); and group 3, left, median, and 50% of the right lobe (n ⫽ 14). Anesthesia was induced by propofol (6 mg/kg) and fentanyl (3 g/kg) administraFrom the Department of Abdominal and Transplantation Surgery, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (D.P., F.d.F., G.J.E., M.d.M., C.R., G.O., B.G.G., M.S.), University of Pittsburgh Medical Center in Italy, Palermo, Italy; Research and Development in the Mediterranean Basin Foundation (E.O.), Palermo, Italy; and Division of Transplantation, Department of Pathology (M.I.M.), and Department of Surgery (B.G.G, M.S.), University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. Address reprint requests to Macro Spada, MD, PhD, Instituto Mediterraneo per i Trapianti e Terapie ad Alta Specializzazione, University of Pittsburgh Medical Center in Italy, Via E. Tricomi N. 1, 90127 Palermo, Italy. Tel: ⫹390912192111; Fax: ⫹390912192400. E-mail: [email protected]
© 2012 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/–see front matter http://dx.doi.org/10.1016/j.transproceed.2012.06.009
Transplantation Proceedings, 44, 2029 –2032 (2012)
2029
2030
PAGANO, DI FRANCESCO, ECHEVERRI ET AL After a midline laparotomy, was performed, a collateral of the portal vein was cannulated to measure the portal vein pressure. Flow measurements were performed on the portal vein and hapatic artery after then isolation by dissection. The pedicle of each lobe was isolated via an extraparenchymal approach. The parenchymal transection was performed by a clamp-crush technique with concomitant hepatic vein identification, suture, and transection. The weighed resected liver parenchyma was notuse to calculated the liver-to-body weight (RWBW) ratio: liver resected weight (g) ⫻ 100/total body weight (g). Arterial blood pressure (ABP), mean arterial pressure (MAP), heart rate (HR), and central vein pressure (CVP) were monitored continuously, and portal vein pressure (PVP), hepatic artery, and portal vein flows were measured before and after the liver resection. Flow measurements performed using ultrasound transit time flow probes (Transonic Systems, Maastricht, The Netherlands) were recorded using a computer (Model 316T; Iworx/CB Sciences, Dover, NH, USA). The animals were followed for 5 days we killed them. Postoperatively, we monitored on a daily basis the clinical signs of liver impairment aspatate transaminase, (AST), alanine transaminase bilirubin (ALT), intenational normalized ratio (INR), and lactic acid. After killing the animals, we performed a complete examination of the major organs of the abdomen and thorax, measured the animal and remnant liver weights, and procured hepatic tissue samples for histologic studies (hematoxylin-eosin) satining. The significance of continuous metric differences was determined by Student t test. Categoric values were compared using chi-square (2) test. Logistic regression analysis was performed to determine the association of various factors with the onset of liver failure; P values ⬍.05 were considered to be significant.
Fig 1. (A) Liver resected weight expressed as a percentage of total body weight (RWBW). Group 1 (blue) and group 2 (red): 1.71 ⫾ 0.01% and 1.86 ⫾ 0.12% respectively, (P ⬎ .05); 2.25 ⫾ 0.22% in all Group 3 (green) pigs (P ⬎ 0.05) in 2.29 ⫾ 0.07% in the liver failure subgroup (lighter green) and 2.18 ⫾ 0.11% in animals who did not develop liver failure (intermediate green) without statistical significance when compared Group 3 subgroup (P ⬎ 0.05). (B) Remnant liver weight expressed as percentage of body weight (LWBW): was 0.9 ⫾ 0.08% in the liver failure subgroup and 1.70 ⫾ 0.24% in animals who did not develop liver failure, with statistical signicance (P ⬍ .05).
tion as intravenons (IV) boluses into marginal ear vein, followed by endotracheal intubation with maintenance using with positive pressure mechanical ventilation with oxygen and isoflurance. Continued neuromuscular block during surgery was obtained by administration of cisatracurium by IV bolus (0.2 mg/kg) followed by continuous IV infusion (0.06 mg/kg/h).
RESULTS
The survival rates were 100% in group 1, 100% in group 2, and 36% in group 3. Among the group 3, 14 animals survived to the end of the study (subgroup 3A) and 9 succumbed on postoperative day(POD) 1–3, owing to liver failure (subgroup 3B). Mean body weights of group 1 and 2 were 19 ⫾ 7 kg and 13 ⫾ 0.3 kg, respectively versus 20 ⫾ 3 kg in group 3. In this last group they were 19 ⫾ 4 kg in subgroup; B and 20 ⫾ 3 kg in subgroup A. RWBW was 1.71 ⫾ 0.01 and 1.86 ⫾ 0.12 in groups 1 and 2, respectively versus 2.25 ⫾ 0.22 in group 3, including 2.29 ⫾ 0.07 in subgroup 3A and 2.18 ⫾ 0.11 in subgroup 3B. Figure 1A shows differences in RWBW among the groups. No differences in MAP, HR, or CVP were observed among the groups. Table 1 shows actual and differential (PVPs) before and after liver resection as well as the potocaval pressure gradient (PCG). Group 3 showed hepatic artery flow
Table 1. Portal Vein Pressure (PVP) and Portocaval Gradient (PCG) Pressure Before and After Liver Resection PVP Before Resection (mm Hg)
Group 1 Group 2 Group 3 Subgroup 3A, no liver failure Subgroup 3B, liver failure
9,50 ⫾ 4.95 7,00 ⫾ 4,24 10,10 ⫾ 3,14 11,40 ⫾ 3,78 8,80 ⫾ 1,92
PVP After Resection (mm Hg)
⌬PVP (mm Hg)
PCG Before Resection (mm Hg)
PCG After Resection (mm Hg)
15,00 ⫾ 2,83 10,00 ⫾ 4,24 17,80 ⫾ 4,98 17,00 ⫾ 6,20 18,60 ⫾ 3,97
5,50 ⫾ 2,12 3,00 ⫾ 0,00 7,70 ⫾ 6,15 5,60 ⫾ 7,77 9,80 ⫾ 3,70
1,50 ⫾ 0,71 1,50 ⫾ 0,71 2,00 ⫾ 2,40 3,20 ⫾ 2,49 0,80 ⫾ 1,79
4,50 ⫾ 2,12 2,00 ⫾ 1,41 6,90 ⫾ 3,98 6,20 ⫾ 4,60 7,60 ⫾ 3,65
No statistical fast significance between all combinations and all groups.
PIG MODEL OF LIVER FAILURE
2031
RWBW (P ⫽ .03). Multivariate analysis using logistic regression for all variables associated with the onset of liver failure revealed the significant independent variables predicting the onset of liver failure after extended hepatic resection to be RWBW (P ⫽ .005), serum INR on POD 2 (P ⫽ .01), serum total bilirubin on POD 1 (P ⫽ .01), and serum lactate at the end of the resection (P ⫽ .02); (Table 2), none of which had a robust 95% confidence interval. DISCUSSION
Fig 2. Postoperative liver function tests. (A) INR, bilirubin (BIL), lactates (LAC); (B) aspartate transmin (AST), and alanine transmine (ALT). In group 3B, the onset of liver failure was associated with a significant increase of INR on POD 2 (P ⫽ .04), total BIL on POD 1–3 (P ⫽ .02), AST on POD 2 and 3 (P ⫽ .05), and LAC at the end of liver resection (P ⫽ .04).
of 156 ⫾ 32 mL/min before and 5.3 ⫾ 2.2 mL/min after resection (P ⫽ .004) and portal vein flow of 360 ⫾ 80 mL/min before and 170 ⫾ 50 mL/min at the end of the resection. Laboratory tests in group 3, subgroup 3A and 3B, are depicted in Fig. 2. Remnant liver weight expressed as percentage of body weight (LWBW) at the time of necropsy is showed in Fig 1B. The light-microscopic findings of the liver before and after liver resection were similar among all the groups with exception of significant more severe portal and septal edema, endothelial cell detachment, necrosis, and mitosis in subgroup 3A versus subgroup 3B. Upon univariate analysis, variables associated with the onset of liver failure were serum INR on POD 2 (P ⫽ .04), serum total bilirubin on POD, 1 (P ⫽ .02), 2 (P ⫽ .02), and 3 (P ⫽ .02), serum AST on POD, 3 (P ⫽ .02) and 3 (P ⫽ .05), serum lactic acid at the end of liver resection (P ⫽ .04), and
Previously developed large animal models to study hepatic damage after liver resection have shown poor, correlations with the extent of resection. In the rescent study, we sought study, we sought to created an easy to reproducible model of early liver impairment after extended liver resection. Liver failure developed only among group 3 animals, which underwent extended resection of the left, median, and 50% of the right lobes, leaving only the remaining right lateral and caudate lobes surrounding the inferior vena cava. We found that an RWBW ⬎2.3% (P ⬍ .005), a persistently high bilirubin level ⬎4.6 mg/dL in POD 2 (P ⬍ .05), a high INR ⬎1.64 on POD 2 (P ⬍ .005), and a lactate level ⬎8.9 mmol/L after surgery (P ⬍ .005) tended to be independent predictive factors for the developing recent of liver failure after extended hepatectomy. Although PVP, after surgery and differences between PVP after and before resection and PCG were increased among hosts displaying liver failure, they were not significant predictors of liver impairment (P ⬎ .05). The subgroup that developed liver failure showed histologic significantly greater scores in endothelial cell detachment, portal and septal edema, as well as necrosis (P ⬍ .05), which may have related to increased portal vein flow causing periportal sinusoidal endothelial injury. There was a significant reduction in hepatic artery blood flow, but not in portal venous flow. After 95% liver resection in group 3, 8 pigs died, clearly showing the difficulties associated with this procedure, results that were similar to previous earlier reports. In our experience, the technique of resection of ⱕ80% was simple and relatively bloodless owing to control of the portal vein and hepatic artery vessels before the resection, but it did not produce liver failure. In the present series, 5 pigs never developed liver failure, and 8 animals developed liver failure; thus 13/18 pigs (72.2%) displayed a major metabolic imbalance that caused irreversible liver malfunction and/or immediate death. In conclusion, the extended hepatectomy we performed caused rapid onset of liver failure, that was easy to repro-
Table 2. Actual Values of Liver Resected Weight Expressed as a Percentage of Total Body Weight (RWBW), INR, Bilirubin (BIL), and Lactates (LAC), with Odds Ratios from Multivariate Analysis and 95% Confidence Intervals, Mean ⴞ SD
RWBW LAC INR BIL
Actual Values
Odds Ratios
Standard Error
2,29 ⫾ 0,12 5,20 ⫾ 2,08 1,64 ⫾ 0,34 4,67 ⫾ 2,87
18.4561 1.25084 2.80106 1.03222
11.54301 0.24992 6.17866 0.28181
95% Confidence Interval
0.98311 0.84554 0.37129 0.60448
6.53861 1.85043 2.10121 1.76263
2032
duce and useful to study liver damage in pigs. The main factor led to early liver failure was a resection of ⬎2.3% of the animal’s body weight and failure of recovery of liver function tests in the first days. ACKNOWLEDGEMENTS The authors thank Warren Blumberg for his critical review of the paper and Pietro Tagliareni for his technical support on histology specimens.
REFERENCES 1. Khan AZ, Bann SD, Pitsinis V, et al: Refining the technique of hepatic parenchymal transection: combined saline-linked radiofrequency precoagulation and ultrasonic aspiration. Hepatogastroenterology 54:1167, 2007
PAGANO, DI FRANCESCO, ECHEVERRI ET AL 2. Nagino M, Kamiya J, Nishio H, et al: Two hundred forty consecutive portal vein embolizations before extended hepatecomy for biliary cancer: surgical outcome and long-term follow-up. Ann Surg 243:364, 2006 3. Kubota K, Makuuchi M, Kusaka K, et al: Measurement of liver volume and hepatic functional reserve as a guide to decision making in resectional surgery for hepatic tumors. Hepatology 26:1176, 1997 4. Wang HS, Ohkohchi N, Enomoto Y, et al: Excessive portal flow causes graft failure in extremely small-for-size liver transplantation in pigs. World J Gastroenterol 28:11:6954, 2005 5. Lida T, Yagi S, Taniguchi K, et al: Improvement of morphological changes after 70% hepatectomy with portocaval shunt: preclinical study in porcine model. J Surg Res. 143:238, 2007 6. Mullin EJ, Metcalfe MS, Maddern GJ: How much resection is too much? Am J Surg 190:876, 2005 7. Court FG, Laws PE, Morrison CP, et al: Subtotal hepatectomy: a porcine model for the study of liver regeneration. J Surg Res 116:181, 2006