- Email: [email protected]
Adenosine Increases Hepatic Artery Flow in Liver Transplant Recipients: A Pilot Study
Adenosine Increases Hepatic Artery Flow in Liver Transplant Recipients: A Pilot Study X. Zhua,b,*, H. Shibaa, Y. Zhub, C. Quintinia, B. Eghtesada, C. Millera, J.J. Funga, and D.M. Kellya a Department of General Surgery, Cleveland Clinic, Cleveland, Ohio, USA; and bDepartment of General Surgery, The Affiliated Hospital of Xuzhou Medical College, Jiangsu, China
ABSTRACT Background. The aim of this study was to assess the effect of low-dose adenosine on hepatic artery flow (HAF) when administered intraoperatively by continuous infusion. Materials and Methods. Between January 2009 and August 2009, 74 patients underwent orthotopic liver transplantation (OLT). Ten patients were enrolled for adenosine treatment, and 64 non-study patients served as controls. After arterial reperfusion, a 16-G central venous catheter was placed in the gastroduodenal artery, and adenosine was continuously infused at doses ranging from 0.7 to 2.8 mg/kg/min for 30 min. HAF and portal vein flow were measured using a transit time flow meter before adenosine infusion, during infusion, and 10 min after infusion. Liver function tests were monitored routinely, duplex ultrasonography was performed on postoperative day 1, and the hepatic artery resistive index measured. The patients were followed for 1 year. Results. Adenosine significantly increased HAF at doses from 0.7 to 2.8 mg/kg/min. The smallest increase in HAF was 24% above the baseline; in 80% of patients, the increase in HAF was >50% of the baseline values. In 2 patients, HAF was increased by >300%. The dosing started at 0.7 mg/kg/min, and 6 of 10 patients responded. Three patients required an increase to 1.4 mg/kg/min. Doses >2.8 mg/kg/min did not further increase HAF. One patient showed a minimal response regardless of the dose. There were no differences between the adenosine group and control group with respect to liver function (aspartate aminotransferase, alanine aminotransferase, total bilirubin, and International Normalized Ratio), platelet count on POD2, hepatic artery resistive index, and post-transplant length of stay, intensive care days, or 1-year patient survival rates. Conclusions. This pilot study established that adenosine administered directly into the hepatic artery produces a similar effect on HAF in cadaveric liver transplant recipients to that found in the laboratory without producing systemic side effects.
L
IVER TRANSPLANTATION (OLT) is the treatment of choice for selected groups of patients with end-stage liver disease or liver failure. In the pretransplant era, liver failure was nearly universally fatal, with a mortality from fulminant hepatic failure of 80%e90% and a 1-year mortality in decompensated cirrhosis of >50%. By contrast, after liver transplantation, patient survival was >85% at 1 year and >70% at 5 years [1]. Thus, liver transplantation has become the standard of care for either acute or chronic liver failure. Small-for-size syndrome (SFSS) is a clinical syndrome described after OLT and extended hepatectomy. Many mechanisms are involved in its occurrence; however, 0041-1345/16 http://dx.doi.org/10.1016/j.transproceed.2016.01.005
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in the recent past, hepatic artery (HA) vasospasm has taken a central role. Therefore, several techniques of vascular modulation have been attempted in cases of HA flow This study was supported by the American Liver Foundation (Liver Scholar Award 2003), the American Society of Transplantation (Council Faculty Grant 2003e2004) and the American Society of Transplant Surgeons (ASTS-Wyeth Mid-Level Faculty Grant 2008). *Address correspondence to Xiaocheng Zhu, Department of General Surgery, The Affiliated Hospital of Xuzhou Medical College, Jiangsu 221006, China. E-mail: [email protected] ª 2016 Published by Elsevier Inc. 360 Park Avenue South, New York, NY 10010-1710
Transplantation Proceedings, 48, 116e119 (2016)
ADENOSINE INCREASES HAF
(HAF) first in OLT [2,3]. Our recent studies have suggested that the restoration of HAF has a significant impact on the outcome and improved survival in healthy pigs after OLT [4]. Adenosine, a nucleoside produced by cells and tissues in response to various physical and metabolic stresses, mediates physiologic activities that include sedation, inhibition of platelet aggregation, and vasodilatation. The effects of adenosine are mediated by a family of four G-proteine coupled receptors, namely, A1, A2A, A2B, and A3 [5e7]. Adenosine has been demonstrated to effectively reverse HA vasospasms in the porcine small-for-size liver graft. However, application of adenosine to improve liver blood flow in clinical liver transplantations is unknown. The aim of this study was to assess the effect of low-dose adenosine on HAF when administered intraoperatively by continuous infusion.
MATERIALS AND METHODS Patients This study was approved by the Research Ethics Committee of the Cleveland Clinic. Written informed consent was obtained from all of the patients. All of the treatment measures were handled and made anonymous according to the ethical and legal standards. Between January 2009 and August 2009, 74 patients underwent OLT. Eighteen patients consented, and 10 patients (7 males, 3 females) were enrolled for adenosine treatment (IRB 08e786 with exemption from the US Food and Drug Administration for IND). Sixty-four nonstudy patients served as controls. There were no differences between the 2 groups in terms of sex, age, and race.
Operation After arterial reperfusion, a 16-G central venous catheter was placed in the gastroduodenal artery and tunneled subcutaneously to exit at the back of the neck. Adenosine was continuously infused at doses ranging from 0.7 to 2.8 mg/kg/min for 30 min. The starting dose of 0.7 mg/kg/min is based on our work in the laboratory. HAF and portal vein flow (PVF) were measured using a transit time flow meter before adenosine infusion as the baseline value and after portal vein transient clamping before adenosine infusion as an augmentation (aug). Next, HAF and PVF were measured again during infusion and 10 min after infusion, respectively. The mean artery pressure and heart rate were monitored continuously during the entire process.
Postoperative Care and Monitoring Liver function tests were monitored routinely, duplex ultrasonography was performed on postoperative day (POD) 1, and the HA resistive index was measured. Patients were followed up for 1 year.
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Fig 1. Changes in hepatic artery flow (HAF mL/100 g/min) at different adenosine infusion doses. HAF was increased significantly during clamping of the portal vein (augmentation [aug]). Adenosine increased HAF significantly at doses from 0.7 to 2.8 mg/kg/min. When adenosine infusion was stopped, HAF was still slightly higher than at the baseline but without a significant difference. *P < .05 compared with the baseline value.
RESULTS Adenosine Infusion Increases HAF
HAF (mL/100 g/min) was expressed as milliliters per 100 g of liver tissue per minute. The adenosine infusion dose was started at 0.7 mg/kg/min, was increased to 1.4 mg/kg/min, and then reached a maximum of 2.8 mg/kg/min. As shown in Fig 1, adenosine significantly increased HAF at doses from 0.7 to 2.8 mg/kg/min (P < .05). When the adenosine infusion was stopped, there was no difference between HAF and the baseline value (Fig 1). Adenosine Infusion and HAF Increase Rates
Between January 2009 and August 2009, 74 patients underwent OLT. Finally, 10 patients were enrolled for adenosine treatment, and 64 nonstudy patients served as controls. The smallest increase in HAF was 24.2% above baseline; in 8 of the 10 patients (80%), there was an increase in HAF of >50% over baseline values (Table 1). In 2 patients, HAF increased by >300%, 1 patient demonstrated increased HAF by 300% at doses of 0.7 mg/kg/min, and the other demonstrated increased HAF by 550%; the peak increase was at 2.1 mg/kg/ min. The dosing was started at 0.7 mg/kg/min, and 6 of the 10 patients responded. Three patients required an increase to 1.4 mg/kg/min. Doses >2.8 mg/kg/min did not further increase HAF. One patient had a minimal response regardless of the dose. Safety of Adenosine Infusion
Statistical Analysis The data were expressed as the median and interquartile range (25%e75%) or mean standard deviation. Univariate analysis was performed using the paired Student t test and the ManneWhitney U test. Survival analysis was performed using the log-rank test. Statistics were performed using SPSS, version 18.0, statistical software (SPSS, Inc., Chicago, IL), and P < .05 was considered significant.
Adenosine infusion had no effect on the mean artery pressure and heart rate in the 10 patients enrolled for adenosine infusion (Fig 2) and there were no systemic side effects. PVF showed no significant changes during adenosine infusion at doses from 0.7 to 2.8 mg/kg/min (Fig 3). Liver function was assessed using aspartate aminotransferase, alanine aminotransferase, total bilirubin, and International
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Table 1. Correlation Between the Adenosine Infusion Dose and HAF Increase Rates
Patient
Dose Ranges
Start Response Dose
Peak Response Dose
Peak HAF Increase Rates (%)
1 2 3 4 5 6 7 8 9 10
0.7e2.8 0.7e2.8 0.7e4.2 0.7e2.8 0.7e2.8 0.7e4.2 0.7e2.8 0.7e0.7 0.7e2.8 0.7e4.2
1.4 0.7 0.7 0.7 0.7 1.4 0.7 0.7 0.7 1.4
1.4 1.4 2.8 1.4 1.4 2.8 1.4 0.7 2.1 2.8
111.5 66.7 75.0 80.0 24.2 100.0 163.6 300.0 550.0 31.6
Abbreviation: HAF, hepatic artery flow.
Normalized Ratio as related factors. The levels of these parameters were similar between the adenosine group and control group on POD 2. Although the levels of aspartate aminotransferase (U/L) and alanine aminotransferase (U/L) on POD 2 were higher in the adenosine group than those in the control group (496.0 vs 341.0U/L and 286.0 vs 232.0U/L, respectively), no difference was achieved (Table 2). In terms of the platelet count on POD 2, the HA resistive index and posttransplant length of stay and intensive care days, there were no differences between the 2 groups (Table 2). The 1-year survival rate was 100% in the adenosine group compared with 91.4% in the control group (P > .05). DISCUSSION
In this study, we demonstrated for the first time that, in cadaveric liver transplant recipients of the human randomized double-blind trial, adenosine infusion administered directly into the HA increased HAF without producing significant systemic side effects. Adenosine infused continuously through the HA at doses from 0.7 to 2.8 mg/kg/min significantly increased HAF over the study period. This result was consistent with that of
Fig 2. Changes in the mean artery pressure (MAP) and heart rate (HR) during adenosine infusion. MAP and HR during adenosine infusion showed no significant difference compared with that during the baseline period (P > .05). Aug indicates that the portal vein was clamped.
Fig 3. Changes in portal vein flow (PVF; mL/100 g/min) at different adenosine infusion doses. There were no changes in PVF compared with the baseline value during adenosine infusion at doses from 0.7 to 2.8 mg/kg/min (P > .05). Aug indicates that the portal vein was clamped.
previous work from our animal experiments, which demonstrated that HA infusion of adenosine significantly improved HAF, reversed pathologic changes and significantly improved survival in small-for-size liver graft of pigs [4]. SFSS is a serious complication in partial liver transplantation and a major limiting factor in expanding the use of small partial liver grafts [8e10]. Demetris et al [11], in their pathologic study of SFSS, suggested that patients with clinical SFSS demonstrated histopathologic evidence of centrilobular microvesicular steatosis, ischemic cholangitis, bile duct necrosis, and parenchymal infarcts, which were accompanied by HA vasospasm; in effect, there was functional dearterialization of the liver. Work from our laboratory described HA Table 2. General Information and Clinical Outcome for the Control Group and Adenosine Group Characteristic
Control Group (n ¼ 64)
Adenosine Group (n ¼ 10)
P
Sex, n (%) 1.00 Female 19 (29.7) 3 (30) Male 45 (70.3) 7 (70) Race, n (%) 1.00 White 44 (68.8) 7 (70) Non-white 20 (31.2) 3 (30) Age 59.0 (50.0e63.0) 53.0 (50.0e58.0) .94 BMI 27.1 (23.6e32.9) 29.8 (24.6e34.5) .78 AST (U/L) 341.0 (183.5e738.5) 496.0 (376.5e735.5) .49 ALT (U/L) 232.0 (146.0e523.5) 286.0 (210.5e674.5) .79 TBIL (mg/dL) 2.0 (1.3e3.1) 1.2 (0.9e2.6) .36 INR 1.2 (1.1e1.3) 1.3 (1.2e1.3) .51 PLT (*109/L) 41.0 (31.5e57.5) 56.0 (38.5e57.5) .54 ICU days 4.0 (3.0e7.0) 3.0 (2.0e4.0) .09 LOS 13.0 (9.0e23.5) 10.0 (8.5e12.0) .09 HARI 0.81 (0.75e0.89) 0.77 (0.71e0.85) .98 1-year survival rate 91.4% 100.0% .55 The laboratory values are listed as medians (25%e75%) on postoperative day 2. Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; BMI, body mass index; HARI, hepatic artery resistive index; ICU, intensive care unit; INR, International Normalized Ratio; LOS, length of hospital stay; PLT, platelets; TBIL, total bilirubin.
ADENOSINE INCREASES HAF
vasospasm in the SFS graft, and subsequent works focused on reversing the vasospasm and increasing HAF [4,12]. Regulating hepatic blood flow is complex. HAF varies inversely with PVF; this relationship is known as the HA buffer response. An impaired HA buffer response is important in the pathophysiology of the SFSS. Adenosine infused directly into the HA of the SFS porcine liver graft increased HAF, decreased graft injury, and improved survival rates [13e15]. Adenosine infusion directly into the HA in small doses did not produce any systemic side effects. The heart rates and mean artery pressure were stable throughout the study period. Although adenosine significantly increased HAF and should improve the graft histologic condition regarding HA spasm and bile duct necrosis, liver function did not increase significantly in the adenosine group compared with that in the control group. This might be related to whole liver transplantation without SFSS. This is the first report of using adenosine as a therapeutic agent in human OLT. The infusion dosage of adenosine started from 0.7 mg/kg/ min and increased to 1.4 mg/kg/min, achieving HAF increases in 50% of patients. When the dosage was increased to 2.8 mg/kg/min, only a minor HAF increase was observed in the remaining patients; a further increase of the dosage did not produce a better response, but increased the adverse effects. These findings indicate that adenosine is a highefficiency agonist to the human HA; most patients respond well to it, making it a potent medication. Adenosine, a purine nucleoside, is a potent vasodilator that is found in all cells in the body. Adenosine has been shown to reverse the vasoconstrictor action of several agents, including catecholamines and angiotensin, without altering PVF, making it the agent of choice to establish the isolated effect of increasing HAF [16]. Its half-life is very short, approximately 9 s, because it is rapidly taken up by endothelial cells, red blood cells, and myocardial cells before being metabolized [17]. The effects of adenosine are mediated by a family of 4 G-proteinecoupled receptors, namely, A1, A2A, A2B, and A3 [5e7]. Although all 4 receptors are expressed in hepatocytes, most of its vasodilator actions are through the stimulation of A1, A2A, and A2B receptors [18,19]. The vasodilatory action of adenosine occurs through direct action on vascular smooth muscle cells and by modulation of vascular endothelial cells, which synthesize and secrete vasodilators, such as nitric oxide and prostacyclin, and vasoconstrictors, including endothelin and thromboxane A2. The current study was subject to some limitations. First, this is a pilot study without a randomized controlled trial; thus, there is bias for the data. However, this study still shows that adenosine used in human liver transplantation is effective and feasible. Second, adenosine was administered via a 16-G cannula, which was secured in the stump of the gastroduodenal artery of the recipient, and it is difficult to keep the cannula in the body for several days. The optimal way of maintaining the cannula in the body might be to place a pump that connects the cannula to the gastroduodenal artery, a method that is commonly applied in oncologic therapy for hepatic cancer. Finally, because the number of patients in the present study is
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small, and the follow-up time is relatively short, the effects and safety of adenosine should be further demonstrated in a study with a large sample size and a longer duration. In conclusion, this pilot study established that adenosine administered directly into the HA produced a similar effect on HAF in cadaveric liver transplant recipients to that found in the laboratory without producing systemic side effects. The optimum dose range is 0.7e2.8 mg/kg/min. REFERENCES [1] Riordan SM, Williams R. Perspectives on liver failure: past and future. Semin Liver Dis 2008;28:137e41. [2] Tucker ON, Heaton N. The ‘small for size’ liver syndrome. Curr Opin Crit Care 2005;11:150e5. [3] Serenari M, Cescon M, Cucchetti A, et al. Liver function impairment in liver transplantation and after extended hepatectomy. World J Gastroenterol 2013;19:7922e9. [4] Kelly DM, Zhu X, Shiba H, et al. Adenosine restores the hepatic artery buffer response and improves survival in a porcine model of small-for-size syndrome. Liver Transpl 2009;15:1448e57. [5] Chan ES, Cronstein BN. Molecular action of methotrexate in inflammatory diseases. Arthritis Res 2002;4:266e73. [6] Chan ES, Montesinos MC, Fernandez P, et al. Adenosine A(2A) receptors play a role in the pathogenesis of hepatic cirrhosis. Br J Pharmacol 2006;148:1144e55. [7] de Brito MT, Canto A, Correia JH, et al. Adenosine A(2A) receptors in portal hypertension: their role in the abnormal response to adenosine of the cranial mesenteric artery in rabbits. Br J Pharmacol 2002;135:1324e30. [8] Dahm F, Georgiev P, Clavien PA. Small-for-size syndrome after partial liver transplantation: definition, mechanisms of disease and clinical implications. Am J Transplant 2005;5:2605e10. [9] Man K, Fan ST, Lo CM, et al. Graft injury in relation to graft size in right lobe live donor liver transplantation: a study of hepatic sinusoidal injury in correlation with portal hemodynamics and intragraft gene expression. Ann Surg 2003;237:256e64. [10] Busuttil RW, Goss JA. Split liver transplantation. Ann Surg 1999;229:313e21. [11] Demetris AJ, Kelly DM, Eghtesad B, et al. Pathophysiologic observations and histopathologic recognition of the portal hyperperfusion or small-for-size syndrome. Am J Surg Pathol 2006;30: 986e93. [12] Zhu X, Fung JJ, Nakagawa S, et al. Elevated catecholamines and hepatic artery vasospasm in porcine small-for-size liver graft. J Surg Res 2012;174:157e65. [13] Ho H, Sorrell K, Bartlett A, et al. Modeling the hepatic arterial buffer response in the liver. Med Eng Phys 2013;35:1053e8. [14] Smyrniotis V, Kostopanagiotou G, Kondi A, et al. Hemodynamic interaction between portal vein and hepatic artery flow in smallfor-size split liver transplantation. Transplant Int 2002;15:355e60. [15] Marcos A, Olzinski AT, Ham JM, et al. The interrelationship between portal and arterial blood flow after adult to adult living donor liver transplantation. Transplantation 2000;70:1697e703. [16] Lautt WW, Legare DJ. Adenosine modulation of hepatic arterial but not portal venous constriction induced by sympathetic nerves, norepinephrine, angiotensin, and vasopressin in the cat. Can J Physiol Pharmacol 1986;64:449e54. [17] Feng JD, Yeung PK. A simple high-performance liquid chromatography assay for simultaneous measurement of adenosine, guanosine, and the oxypurine metabolites in plasma. Ther Drug Monit 2000;22:177e83. [18] Dixon AK, Gubitz AK, Sirinathsinghji DJ, et al. Tissue distribution of adenosine receptor mRNAs in the rat. Br J Pharmacol 1996;118:1461e8. [19] Collis MG, Hourani SM. Adenosine receptor subtypes. Trends Pharmacol Sci 1993;14:360e6.
ABSTRACT Background. The aim of this study was to assess the effect of low-dose adenosine on hepatic artery flow (HAF) when administered intraoperatively by continuous infusion. Materials and Methods. Between January 2009 and August 2009, 74 patients underwent orthotopic liver transplantation (OLT). Ten patients were enrolled for adenosine treatment, and 64 non-study patients served as controls. After arterial reperfusion, a 16-G central venous catheter was placed in the gastroduodenal artery, and adenosine was continuously infused at doses ranging from 0.7 to 2.8 mg/kg/min for 30 min. HAF and portal vein flow were measured using a transit time flow meter before adenosine infusion, during infusion, and 10 min after infusion. Liver function tests were monitored routinely, duplex ultrasonography was performed on postoperative day 1, and the hepatic artery resistive index measured. The patients were followed for 1 year. Results. Adenosine significantly increased HAF at doses from 0.7 to 2.8 mg/kg/min. The smallest increase in HAF was 24% above the baseline; in 80% of patients, the increase in HAF was >50% of the baseline values. In 2 patients, HAF was increased by >300%. The dosing started at 0.7 mg/kg/min, and 6 of 10 patients responded. Three patients required an increase to 1.4 mg/kg/min. Doses >2.8 mg/kg/min did not further increase HAF. One patient showed a minimal response regardless of the dose. There were no differences between the adenosine group and control group with respect to liver function (aspartate aminotransferase, alanine aminotransferase, total bilirubin, and International Normalized Ratio), platelet count on POD2, hepatic artery resistive index, and post-transplant length of stay, intensive care days, or 1-year patient survival rates. Conclusions. This pilot study established that adenosine administered directly into the hepatic artery produces a similar effect on HAF in cadaveric liver transplant recipients to that found in the laboratory without producing systemic side effects.
L
IVER TRANSPLANTATION (OLT) is the treatment of choice for selected groups of patients with end-stage liver disease or liver failure. In the pretransplant era, liver failure was nearly universally fatal, with a mortality from fulminant hepatic failure of 80%e90% and a 1-year mortality in decompensated cirrhosis of >50%. By contrast, after liver transplantation, patient survival was >85% at 1 year and >70% at 5 years [1]. Thus, liver transplantation has become the standard of care for either acute or chronic liver failure. Small-for-size syndrome (SFSS) is a clinical syndrome described after OLT and extended hepatectomy. Many mechanisms are involved in its occurrence; however, 0041-1345/16 http://dx.doi.org/10.1016/j.transproceed.2016.01.005
116
in the recent past, hepatic artery (HA) vasospasm has taken a central role. Therefore, several techniques of vascular modulation have been attempted in cases of HA flow This study was supported by the American Liver Foundation (Liver Scholar Award 2003), the American Society of Transplantation (Council Faculty Grant 2003e2004) and the American Society of Transplant Surgeons (ASTS-Wyeth Mid-Level Faculty Grant 2008). *Address correspondence to Xiaocheng Zhu, Department of General Surgery, The Affiliated Hospital of Xuzhou Medical College, Jiangsu 221006, China. E-mail: [email protected] ª 2016 Published by Elsevier Inc. 360 Park Avenue South, New York, NY 10010-1710
Transplantation Proceedings, 48, 116e119 (2016)
ADENOSINE INCREASES HAF
(HAF) first in OLT [2,3]. Our recent studies have suggested that the restoration of HAF has a significant impact on the outcome and improved survival in healthy pigs after OLT [4]. Adenosine, a nucleoside produced by cells and tissues in response to various physical and metabolic stresses, mediates physiologic activities that include sedation, inhibition of platelet aggregation, and vasodilatation. The effects of adenosine are mediated by a family of four G-proteine coupled receptors, namely, A1, A2A, A2B, and A3 [5e7]. Adenosine has been demonstrated to effectively reverse HA vasospasms in the porcine small-for-size liver graft. However, application of adenosine to improve liver blood flow in clinical liver transplantations is unknown. The aim of this study was to assess the effect of low-dose adenosine on HAF when administered intraoperatively by continuous infusion.
MATERIALS AND METHODS Patients This study was approved by the Research Ethics Committee of the Cleveland Clinic. Written informed consent was obtained from all of the patients. All of the treatment measures were handled and made anonymous according to the ethical and legal standards. Between January 2009 and August 2009, 74 patients underwent OLT. Eighteen patients consented, and 10 patients (7 males, 3 females) were enrolled for adenosine treatment (IRB 08e786 with exemption from the US Food and Drug Administration for IND). Sixty-four nonstudy patients served as controls. There were no differences between the 2 groups in terms of sex, age, and race.
Operation After arterial reperfusion, a 16-G central venous catheter was placed in the gastroduodenal artery and tunneled subcutaneously to exit at the back of the neck. Adenosine was continuously infused at doses ranging from 0.7 to 2.8 mg/kg/min for 30 min. The starting dose of 0.7 mg/kg/min is based on our work in the laboratory. HAF and portal vein flow (PVF) were measured using a transit time flow meter before adenosine infusion as the baseline value and after portal vein transient clamping before adenosine infusion as an augmentation (aug). Next, HAF and PVF were measured again during infusion and 10 min after infusion, respectively. The mean artery pressure and heart rate were monitored continuously during the entire process.
Postoperative Care and Monitoring Liver function tests were monitored routinely, duplex ultrasonography was performed on postoperative day (POD) 1, and the HA resistive index was measured. Patients were followed up for 1 year.
117
Fig 1. Changes in hepatic artery flow (HAF mL/100 g/min) at different adenosine infusion doses. HAF was increased significantly during clamping of the portal vein (augmentation [aug]). Adenosine increased HAF significantly at doses from 0.7 to 2.8 mg/kg/min. When adenosine infusion was stopped, HAF was still slightly higher than at the baseline but without a significant difference. *P < .05 compared with the baseline value.
RESULTS Adenosine Infusion Increases HAF
HAF (mL/100 g/min) was expressed as milliliters per 100 g of liver tissue per minute. The adenosine infusion dose was started at 0.7 mg/kg/min, was increased to 1.4 mg/kg/min, and then reached a maximum of 2.8 mg/kg/min. As shown in Fig 1, adenosine significantly increased HAF at doses from 0.7 to 2.8 mg/kg/min (P < .05). When the adenosine infusion was stopped, there was no difference between HAF and the baseline value (Fig 1). Adenosine Infusion and HAF Increase Rates
Between January 2009 and August 2009, 74 patients underwent OLT. Finally, 10 patients were enrolled for adenosine treatment, and 64 nonstudy patients served as controls. The smallest increase in HAF was 24.2% above baseline; in 8 of the 10 patients (80%), there was an increase in HAF of >50% over baseline values (Table 1). In 2 patients, HAF increased by >300%, 1 patient demonstrated increased HAF by 300% at doses of 0.7 mg/kg/min, and the other demonstrated increased HAF by 550%; the peak increase was at 2.1 mg/kg/ min. The dosing was started at 0.7 mg/kg/min, and 6 of the 10 patients responded. Three patients required an increase to 1.4 mg/kg/min. Doses >2.8 mg/kg/min did not further increase HAF. One patient had a minimal response regardless of the dose. Safety of Adenosine Infusion
Statistical Analysis The data were expressed as the median and interquartile range (25%e75%) or mean standard deviation. Univariate analysis was performed using the paired Student t test and the ManneWhitney U test. Survival analysis was performed using the log-rank test. Statistics were performed using SPSS, version 18.0, statistical software (SPSS, Inc., Chicago, IL), and P < .05 was considered significant.
Adenosine infusion had no effect on the mean artery pressure and heart rate in the 10 patients enrolled for adenosine infusion (Fig 2) and there were no systemic side effects. PVF showed no significant changes during adenosine infusion at doses from 0.7 to 2.8 mg/kg/min (Fig 3). Liver function was assessed using aspartate aminotransferase, alanine aminotransferase, total bilirubin, and International
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ZHU, SHIBA, ZHU ET AL
Table 1. Correlation Between the Adenosine Infusion Dose and HAF Increase Rates
Patient
Dose Ranges
Start Response Dose
Peak Response Dose
Peak HAF Increase Rates (%)
1 2 3 4 5 6 7 8 9 10
0.7e2.8 0.7e2.8 0.7e4.2 0.7e2.8 0.7e2.8 0.7e4.2 0.7e2.8 0.7e0.7 0.7e2.8 0.7e4.2
1.4 0.7 0.7 0.7 0.7 1.4 0.7 0.7 0.7 1.4
1.4 1.4 2.8 1.4 1.4 2.8 1.4 0.7 2.1 2.8
111.5 66.7 75.0 80.0 24.2 100.0 163.6 300.0 550.0 31.6
Abbreviation: HAF, hepatic artery flow.
Normalized Ratio as related factors. The levels of these parameters were similar between the adenosine group and control group on POD 2. Although the levels of aspartate aminotransferase (U/L) and alanine aminotransferase (U/L) on POD 2 were higher in the adenosine group than those in the control group (496.0 vs 341.0U/L and 286.0 vs 232.0U/L, respectively), no difference was achieved (Table 2). In terms of the platelet count on POD 2, the HA resistive index and posttransplant length of stay and intensive care days, there were no differences between the 2 groups (Table 2). The 1-year survival rate was 100% in the adenosine group compared with 91.4% in the control group (P > .05). DISCUSSION
In this study, we demonstrated for the first time that, in cadaveric liver transplant recipients of the human randomized double-blind trial, adenosine infusion administered directly into the HA increased HAF without producing significant systemic side effects. Adenosine infused continuously through the HA at doses from 0.7 to 2.8 mg/kg/min significantly increased HAF over the study period. This result was consistent with that of
Fig 2. Changes in the mean artery pressure (MAP) and heart rate (HR) during adenosine infusion. MAP and HR during adenosine infusion showed no significant difference compared with that during the baseline period (P > .05). Aug indicates that the portal vein was clamped.
Fig 3. Changes in portal vein flow (PVF; mL/100 g/min) at different adenosine infusion doses. There were no changes in PVF compared with the baseline value during adenosine infusion at doses from 0.7 to 2.8 mg/kg/min (P > .05). Aug indicates that the portal vein was clamped.
previous work from our animal experiments, which demonstrated that HA infusion of adenosine significantly improved HAF, reversed pathologic changes and significantly improved survival in small-for-size liver graft of pigs [4]. SFSS is a serious complication in partial liver transplantation and a major limiting factor in expanding the use of small partial liver grafts [8e10]. Demetris et al [11], in their pathologic study of SFSS, suggested that patients with clinical SFSS demonstrated histopathologic evidence of centrilobular microvesicular steatosis, ischemic cholangitis, bile duct necrosis, and parenchymal infarcts, which were accompanied by HA vasospasm; in effect, there was functional dearterialization of the liver. Work from our laboratory described HA Table 2. General Information and Clinical Outcome for the Control Group and Adenosine Group Characteristic
Control Group (n ¼ 64)
Adenosine Group (n ¼ 10)
P
Sex, n (%) 1.00 Female 19 (29.7) 3 (30) Male 45 (70.3) 7 (70) Race, n (%) 1.00 White 44 (68.8) 7 (70) Non-white 20 (31.2) 3 (30) Age 59.0 (50.0e63.0) 53.0 (50.0e58.0) .94 BMI 27.1 (23.6e32.9) 29.8 (24.6e34.5) .78 AST (U/L) 341.0 (183.5e738.5) 496.0 (376.5e735.5) .49 ALT (U/L) 232.0 (146.0e523.5) 286.0 (210.5e674.5) .79 TBIL (mg/dL) 2.0 (1.3e3.1) 1.2 (0.9e2.6) .36 INR 1.2 (1.1e1.3) 1.3 (1.2e1.3) .51 PLT (*109/L) 41.0 (31.5e57.5) 56.0 (38.5e57.5) .54 ICU days 4.0 (3.0e7.0) 3.0 (2.0e4.0) .09 LOS 13.0 (9.0e23.5) 10.0 (8.5e12.0) .09 HARI 0.81 (0.75e0.89) 0.77 (0.71e0.85) .98 1-year survival rate 91.4% 100.0% .55 The laboratory values are listed as medians (25%e75%) on postoperative day 2. Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; BMI, body mass index; HARI, hepatic artery resistive index; ICU, intensive care unit; INR, International Normalized Ratio; LOS, length of hospital stay; PLT, platelets; TBIL, total bilirubin.
ADENOSINE INCREASES HAF
vasospasm in the SFS graft, and subsequent works focused on reversing the vasospasm and increasing HAF [4,12]. Regulating hepatic blood flow is complex. HAF varies inversely with PVF; this relationship is known as the HA buffer response. An impaired HA buffer response is important in the pathophysiology of the SFSS. Adenosine infused directly into the HA of the SFS porcine liver graft increased HAF, decreased graft injury, and improved survival rates [13e15]. Adenosine infusion directly into the HA in small doses did not produce any systemic side effects. The heart rates and mean artery pressure were stable throughout the study period. Although adenosine significantly increased HAF and should improve the graft histologic condition regarding HA spasm and bile duct necrosis, liver function did not increase significantly in the adenosine group compared with that in the control group. This might be related to whole liver transplantation without SFSS. This is the first report of using adenosine as a therapeutic agent in human OLT. The infusion dosage of adenosine started from 0.7 mg/kg/ min and increased to 1.4 mg/kg/min, achieving HAF increases in 50% of patients. When the dosage was increased to 2.8 mg/kg/min, only a minor HAF increase was observed in the remaining patients; a further increase of the dosage did not produce a better response, but increased the adverse effects. These findings indicate that adenosine is a highefficiency agonist to the human HA; most patients respond well to it, making it a potent medication. Adenosine, a purine nucleoside, is a potent vasodilator that is found in all cells in the body. Adenosine has been shown to reverse the vasoconstrictor action of several agents, including catecholamines and angiotensin, without altering PVF, making it the agent of choice to establish the isolated effect of increasing HAF [16]. Its half-life is very short, approximately 9 s, because it is rapidly taken up by endothelial cells, red blood cells, and myocardial cells before being metabolized [17]. The effects of adenosine are mediated by a family of 4 G-proteinecoupled receptors, namely, A1, A2A, A2B, and A3 [5e7]. Although all 4 receptors are expressed in hepatocytes, most of its vasodilator actions are through the stimulation of A1, A2A, and A2B receptors [18,19]. The vasodilatory action of adenosine occurs through direct action on vascular smooth muscle cells and by modulation of vascular endothelial cells, which synthesize and secrete vasodilators, such as nitric oxide and prostacyclin, and vasoconstrictors, including endothelin and thromboxane A2. The current study was subject to some limitations. First, this is a pilot study without a randomized controlled trial; thus, there is bias for the data. However, this study still shows that adenosine used in human liver transplantation is effective and feasible. Second, adenosine was administered via a 16-G cannula, which was secured in the stump of the gastroduodenal artery of the recipient, and it is difficult to keep the cannula in the body for several days. The optimal way of maintaining the cannula in the body might be to place a pump that connects the cannula to the gastroduodenal artery, a method that is commonly applied in oncologic therapy for hepatic cancer. Finally, because the number of patients in the present study is
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small, and the follow-up time is relatively short, the effects and safety of adenosine should be further demonstrated in a study with a large sample size and a longer duration. In conclusion, this pilot study established that adenosine administered directly into the HA produced a similar effect on HAF in cadaveric liver transplant recipients to that found in the laboratory without producing systemic side effects. The optimum dose range is 0.7e2.8 mg/kg/min. REFERENCES [1] Riordan SM, Williams R. Perspectives on liver failure: past and future. Semin Liver Dis 2008;28:137e41. [2] Tucker ON, Heaton N. The ‘small for size’ liver syndrome. Curr Opin Crit Care 2005;11:150e5. [3] Serenari M, Cescon M, Cucchetti A, et al. Liver function impairment in liver transplantation and after extended hepatectomy. World J Gastroenterol 2013;19:7922e9. [4] Kelly DM, Zhu X, Shiba H, et al. Adenosine restores the hepatic artery buffer response and improves survival in a porcine model of small-for-size syndrome. Liver Transpl 2009;15:1448e57. [5] Chan ES, Cronstein BN. Molecular action of methotrexate in inflammatory diseases. Arthritis Res 2002;4:266e73. [6] Chan ES, Montesinos MC, Fernandez P, et al. Adenosine A(2A) receptors play a role in the pathogenesis of hepatic cirrhosis. Br J Pharmacol 2006;148:1144e55. [7] de Brito MT, Canto A, Correia JH, et al. Adenosine A(2A) receptors in portal hypertension: their role in the abnormal response to adenosine of the cranial mesenteric artery in rabbits. Br J Pharmacol 2002;135:1324e30. [8] Dahm F, Georgiev P, Clavien PA. Small-for-size syndrome after partial liver transplantation: definition, mechanisms of disease and clinical implications. Am J Transplant 2005;5:2605e10. [9] Man K, Fan ST, Lo CM, et al. Graft injury in relation to graft size in right lobe live donor liver transplantation: a study of hepatic sinusoidal injury in correlation with portal hemodynamics and intragraft gene expression. Ann Surg 2003;237:256e64. [10] Busuttil RW, Goss JA. Split liver transplantation. Ann Surg 1999;229:313e21. [11] Demetris AJ, Kelly DM, Eghtesad B, et al. Pathophysiologic observations and histopathologic recognition of the portal hyperperfusion or small-for-size syndrome. Am J Surg Pathol 2006;30: 986e93. [12] Zhu X, Fung JJ, Nakagawa S, et al. Elevated catecholamines and hepatic artery vasospasm in porcine small-for-size liver graft. J Surg Res 2012;174:157e65. [13] Ho H, Sorrell K, Bartlett A, et al. Modeling the hepatic arterial buffer response in the liver. Med Eng Phys 2013;35:1053e8. [14] Smyrniotis V, Kostopanagiotou G, Kondi A, et al. Hemodynamic interaction between portal vein and hepatic artery flow in smallfor-size split liver transplantation. Transplant Int 2002;15:355e60. [15] Marcos A, Olzinski AT, Ham JM, et al. The interrelationship between portal and arterial blood flow after adult to adult living donor liver transplantation. Transplantation 2000;70:1697e703. [16] Lautt WW, Legare DJ. Adenosine modulation of hepatic arterial but not portal venous constriction induced by sympathetic nerves, norepinephrine, angiotensin, and vasopressin in the cat. Can J Physiol Pharmacol 1986;64:449e54. [17] Feng JD, Yeung PK. A simple high-performance liquid chromatography assay for simultaneous measurement of adenosine, guanosine, and the oxypurine metabolites in plasma. Ther Drug Monit 2000;22:177e83. [18] Dixon AK, Gubitz AK, Sirinathsinghji DJ, et al. Tissue distribution of adenosine receptor mRNAs in the rat. Br J Pharmacol 1996;118:1461e8. [19] Collis MG, Hourani SM. Adenosine receptor subtypes. Trends Pharmacol Sci 1993;14:360e6.