Pentoxifylline (PTX) has been shown to have beneficial effects on microcirculatory blood flow. In this study we evaluate the potential hemodynamic and metabolic benefits of PTX during hepatic ischemia. We also test the hypothesis that portal PTX infusion can minimize the I/R injury when compared to systemic infusion.
Despite technical advances in liver surgery in the last decades, the consequences of liver ischemia/reperfusion injury remain a major concern for surgeons. Liver ischemia/reperfusion (I/R) injury is a complex cascade of events mediated by numerous inflammatory cells and molecular mediators, resulting in hepatocyte death and systemic inflammatory response. The degree of inflammatory response and organ dysfunction is dependent on duration of liver ischemia and underlying liver disease. In this setting, activation of hepatic macrophages plays an important role. Macrophages have been responsible for the release of various inflammatory mediators, including but not limited to tumor necrosis factor alpha (TNF-
Pentoxifylline (PTX) is a methylxanthine derivative that displays vasodilatory effects on peripheral blood vessels, particularly on the liver [
Previously, we and others have shown the cardiovascular benefits of PTX infusion in a canine model of hemorrhagic shock [
The experimental protocol was approved by the Institutional Review Board, in adherence with the “Principles of Laboratory Animal Care” formulated by the National Society for Medical Research and the “Guide for the Care and Use of Animals” by the National Institutes of Health.
Twenty-four male mongrel dogs, weighing
A polyethylene cannula (P240) was placed in the right carotid artery to measure mean arterial pressure and to collect arterial blood samples for blood gas, pH, bicarbonate, base deficit, hematocrite and hemoglobin analyses. A 7.5 Fr flow-directed thermodilution fiberoptic pulmonary artery catheter with thermal filament (CCOmbo 744H7.5F, Edwards Swan-Ganz, Baxter Edwards Critical Care, Irvine, CA, USA) was introduced through the right external jugular vein with its tip placed in the pulmonary artery, guided by the pressure wave tracings. This catheter was connected to a cardiac computer (Vigilance, Baxter Edwards Critical Care, Irvine, CA, USA) to measure cardiac output using 3-mL bolus injections of isotonic saline at 20°C every fifteen minutes. The same catheter was also used to collect mixed venous blood samples for gas analysis. All pressure-measuring catheters were connected to disposable pressure transducers (Transpac Transducer, Abbott, Chicago, IL, USA) and then to a Biopac Data Acquisition System (Model MP100, Biopac Systems, Goleta, CA, USA) for continuous recording of systemic and pulmonary artery pressures.
The abdomen was opened through a median celiotomy. The gastroduodenal and right gastric arteries were isolated and ligated. The portal vein and common hepatic artery were dissected, and transit time ultrasonic flow probes were placed around these vessels and connected to a flowmeter (T206 Transonic Volume Flowmeter, Transonic Systems, Inc, Ithaca, NY, USA). A fluid-filled polyethylene catheter was placed in the portal vein, through the pancreatoduodenal vein, to collect blood samples.
During hepatic ischemia, a portosystemic venous-venous bypass was used to decompress the splanchnic bed. Initially, a splenectomy was performed, and a polyethylene cannula was placed in the splenic vein for continuous drainage of the splanchnic territory. Another polyethylene cannula was introduced in the left femoral vein for venous drainage. The tube was primed with heparin-containing saline solution and connected to a centrifugal pump. Pump flow was adjusted to maintain the baseline portal vein blood flow. Immediately before reperfusion, mannitol 20% (50 mL) and calcium gluconate (400 mg) were injected intravenously, and a continuous infusion of dopamine (5
After completion of the surgical preparation, 45 minutes were allowed for stabilization and baseline measurements (BL) readings. Prior to performing Pringle’s maneuver the animals were randomly assigned in three experimental groups: CT (control, portal triad clamping,
Mean systemic and pulmonary arterial pressures (MAP and MPAP, resp.) and hepatic artery and portal vein blood flows (HABF and PVBF, resp.) were continuously recorded. Cardiac output was determined every 15 minutes, using 3-mL bolus injections of isotonic saline at 20°C. Each determination was the arithmetic mean of three consecutive measurements when their differences did not exceed 10%. Arterial, portal, and mixed venous base deficits, pH, pCO2, pO2, oxygen saturation, hemoglobin, bicarbonate levels, and ALT and DHL were measured at baseline (BL), at the end of hepatic ischemia (P45) and 15, 60, and 120 after reperfusion (R15, R60, and R120, resp.). All blood samples were analyzed, immediately after their collection, by a Stat Profile Ultra Analyzer (Nova Biomedical, Waltham, MA, USA). Systemic and splanchnic oxygen delivery, consumption, and extraction (DO2syst, VO2syst, O2ERsyst, DO2splanch, VO2splanch, and O2ERsplanch, resp.) were calculated using standard formulae.
Results are presented as
Portal triad occlusion promoted a slight reduction in MAP in all animals (Table
Mean arterial and pulmonary artery pressures (MAP and MPAP, mmHg), arterial hemoglobin (g/dL), arterial pH in CT (control, portal triad clamping,
Group | BL | P45 | R15 | R60 | R120 | |
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MAP mmHg | CT |
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MPAP mmHg | CT |
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PTX-syst |
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Hemoglobin g/dL | CT |
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PTX-syst |
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Arterial pH | CT |
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PTX-syst |
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PTX-pv |
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Legends: BL: baseline; P45: 45 min after Pringle’s maneuver; R15, R60, and R120: 15, 60, and 120 min after reperfusion. Data are shown as mean ± SEM. aIndicates
Baseline cardiac output was similar in all three groups. However, animals treated with PTX presented significantly higher CO in the first hour after reperfusion, when compared to the control group (Figure
(a) Cardiac output (L/min), (b) and (c) portal vein and hepatic artery blood flows (mL/min) during the experimental protocol. The animals were randomly assigned into three groups: CT (control, portal triad clamping,
Systemic and intraportal infusionS of PTX promoted a significant improvement in portal vein blood flow during reperfusion when compared to CT animals. In all groups a rapid but not sustained restoration of PVBF was observed after portal triad declamping. However, animals in the control group demonstrated a progressive reduction in portal blood flow during the reperfusion phase when compared to PTX-treated animals. Moreover, 30 minutes after reperfusion, until the end of the observation, animals which received systemic PTX presented significantly higher PVBF when compared with baseline values and to the CT group (Figure
All animals presented a sustained recovery of hepatic artery blood flow during reperfusion, with no differences between groups (Figure
Systemic (syst) and splanchnic (splanc) oxygen delivery, consumption and extraction (DO2, VO2, and O2 ER, resp.) in CT (control, portal triad clamping,
Group | BL | P45 | R15 | R60 | R120 | |
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DO2 syst mL/min | CT |
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PTX-syst |
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VO2 syst mL/min | CT |
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PTX-syst |
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O2 ERsyst% | CT |
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PTX-syst |
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DO2 splanc mL/min | CT |
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— |
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PTX-syst |
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— |
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PTX-pv |
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— |
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VO2 splanc mL/min | CT |
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— |
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PTX-syst |
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— |
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PTX-pv |
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— |
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O2 ERsplanc% | CT |
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— |
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PTX-syst |
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— |
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PTX-pv |
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— |
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Legends: BL: baseline; P45: 45 min after Pringle’s maneuver; R15, R60, and R120: 15, 60, and 120 min after reperfusion. Data are shown as mean ± SEM. aIndicates
Pentoxifylline exerted a protective effect against ischemia/reperfusion injury. Serum markers of liver injury remained stable throughout the experiment in animals treated with both systemic PTX and intraportal PTX. However, a progressive increase of serum ALT and LDH was observed in CT group after reperfusion (Figures
(a) Alanine transaminase (ALT, U/L) and (b) lactate dehydrogenase (LDH, U/L) during the experimental protocol. BL: baseline; P45: 45 min after Pringle’s maneuver; R15, R60, and R120: 15, 60, and 120 min after reperfusion. Groups are the same as in Figure
This study confirms that intravenous systemic infusion of PTX is an effective strategy to prevent liver damage after normothermic I/R. Locoregional PTX infusion (
In this study, no differences between the groups were observed regarding systemic arterial pressure and pulmonary arterial pressure. However, during reperfusion cardiac output was significantly higher in animals treated with PTX. The precise mechanism responsible for the improvement in cardiac function observed after PTX administration remains unknown. A combination of factors may have contributed to this beneficial effect of PTX on CO, including, but not limited to: (1) the improvement in systemic blood flow secondary to pentoxifylline’s ability to enhance red blood cell deformability, leading to vasodilatation and decreased afterload, and (2) the downregulation of tumor necrosis factor-
Plasma ALT, AST, and LDH levels are widely used as markers of liver cell damage in animal models and in the clinical setting. In this study, infusion of PTX promoted a protective effect in the liver against I/R injury, with no differences between the two routes of administration. On the other hand, animals that did not receive PTX demonstrated a progressive increase in ALT and LDH levels during reperfusion.
Downregulation of TNF-
The short period of observation is an important limitation of our study. Because of our study design, we could not correlate the data presented herein with mortality or development of multiple organ dysfunction, issues that must be addressed in a future study. Also, the use of a venous by-pass is not routine in liver surgery; however, we decided to use an extrahepatic shunt during portal triad clamping to avoid the deleterious effects of intestinal congestion. Small bowel congestion can lead to intestinal mucosal injury, bacterial translocation, and systemic inflammatory response affecting the hemodynamic and metabolic responses during and after normothermic isolated liver I/R [
We believe that systemic PTX infusion right after reperfusion during liver transplantation could be a useful strategy to improve portal vein blood flow and minimize the deleterious effects of I/R injury. However further investigation is required, in order to evaluate safety and the potential benefits of continuous PTX infusion in short- and long-term graft function and survival.
Despite these limitations, we were able to demonstrate the systemic and hepatosplanchnic hemodynamic benefits of PTX infusion during normothermic hepatic ischemia/reperfusion. We also have shown that pentoxifylline administration could minimize liver damage. However, local PTX infusion was not associated with any significant advantage over systemic route.
This study was supported by Fundação de Amparo a Pesquisa do Estado de São Paulo-FAPESP, São Paulo, Brazil.
The authors are grateful to Natalie A. Iacovoni for her assistance and helpful suggestions.