Methods. A hybrid liver support system has been developed consisting of plasma perfusion through a ..... Kent, UK: Pitman Medical, 1974, pp 148-. 152. 13.
ANNALS OF SURGERY Vol. 217, No. 5, 502-511 © 1993 J. B. Lippincott Company
Development of a Hybrid Bioartificial Liver Jacek Rozga, M.D., Ph.D.,* Michael D. Holzman, M.D.,t Man-Soo Ro, M.D., Ph.D.,t Donald W. Griffin, M.D.,t Daniel F. Neuzil, M.D.,t Todd Giorgio, Ph.D.,4 Albert D. Moscioni, Ph.D.,* and Achilles A. Demetriou, M.D., Ph.D.* From the Department of Surgery and the Liver Support Unit,* Cedars-Sinai Medical Center, Los Angeles, Califomia, and the Departments of Surgeryt and Engineering,4 Vanderbilt University, Nashville, Tennessee
Objective The authors developed an extracorporeal liver support system and tested its efficacy in experimental animals with liver failure. The first clinical use of this system to treat'a patient with liver failure is reported.
Summary Background Data Multiple attempts have been made, ranging from plasma exchange to use of charcoal columns, to develop liver support systems for treating patients with acute severe liver failure. None of these systems has achieved wide clinical use. There is a need for providing liver support as a "bridge" to transplantation and for treating patients with potentially reversible liver dysfunction.
Methods A hybrid liver support system has been developed consisting of plasma perfusion through a charcoal column and a porous hollow fiber module inoculated with 5 X 109 matrix-attached hepatocytes. The system was tested in dogs with ischemic liver failure (n = 7) who underwent plasmapheresis; a control group (n = 6) underwent charcoal perfusion alone. A patient with liver failure was treated with this hybrid system.
Results After 6 hours of hybrid liver support treatment, animals had significantly decreased serum ammonia and lactate levels, increased glucose level, normal prothrombin time, and increased systolic blood pressure compared with controls treated with charcoal perfusion alone. Use of the system to treat a patient was well tolerated with evidence of clinical improvement.
Conclusions Plasma perfusion through a system consisting of a charcoal column and matrix-attached porcine hepatocytes had significant beneficial effects in animals with liver failure and was well tolerated by a patient with liver failure.
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Despite recent therapeutic advances, fulminant liver failure due to multiple causes continues to be associated with significant morbidity and mortality.' Investigators have attempted to support animals and patients with liver insufficiency, using various extracorporeal support systems: cross-circulation,2'3 whole liver perfusion,4'5 hemadsorption,3'6'7 hemodialysis,8'9 plasma exchange,'0 total body washout," use ofmicrosomal enzymes bound to artificial carriers,'2 and other.'3-'7 However, none of these therapeutic modalities succeeded in gaining wide clinical acceptance. Of all the various extracorporeal support methods of treating severe liver failure, charcoal hemoperfusion has been most extensively studied both in animals and humans.6' 8-21 This study determined the efficacy of a novel hybrid system combining charcoal plasma perfusion with perfusion through a hollow-fiber module inoculated with normal hepatocytes in treating animals with irreversible severe liver failure and compare it to that of charcoal plasma perfusion alone. We are also reporting the first clinical use of this hybrid extracorporeal liver support system to treat a patient with severe hepatic failure.
MATERIALS AND METHODS Preparation of Porcine Hepatocytes Hepatocytes were harvested aseptically. Unless otherwise noted, all chemical and tissue culture reagents were purchased from Sigma (Sigma Chemical Co., St. Louis, MO). Penicillin (20 U/ml) and streptomycin (20 mg/ml) were added to all perfusion media. Porcine hepatocytes were isolated from adult male and female pigs weighing 8-10 kg. Under ketamine anesthesia (20 mg/kg, IV), the abdomen was entered through a midline incision; the hepato-duodenal ligament was dissected and all its structures ligated and divided except for the portal vein, which was cannulated with silicone tubing (Silastic, Dow Corning, Midland, MI). Heparin was given (100 U/kg, IV) and intraportal administration of the perfusion solution (2 mmol/l EDTA, 140 mmol/l NaCl, 5 mmol/l KC1, 0.8 mmol/l MgSO4, 1.6 mmol/l Na2HPO4, 0.4 mmol/l KH2PO4, 25 mmol/l NaHCO3) was initiated.22
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The liver was perfused in situ at a rate of 200 ml/min using a roller pump (MasterFlex, Cole-Porter, Chicago, IL). Ten minutes later, the cannulated liver was resected and placed in a sterile basin containing a 0.1% collagenase type IV solution in Ca++-enriched buffer.23 The same solution was recirculated through the liver at 200 ml/min after passage through silicone tubing submerged in an oxygen-saturated waterbath at 38 C. After collagenase recirculation for 30 minutes, the liver capsule was disrupted and digested liver parenchyma suspended in a large volume of ice cold Dulbecco's Modified Eagle's Medium (DMEM). Suspended hepatocytes were then passed through a 100 q nylon mesh (Spectrum Laboratory Products, Los Angeles, CA) and hepatocyteenriched fractions were isolated by centrifugation (50g, 2 minutes). Hepatocyte viability was determined by trypan blue exclusion.
Porcine Hepatocyte Attachment to Microcarriers Isolated porcine hepatocytes were attached to collagen-coated dextran microcarriers (Cytodex 3, Pharmacia LKB Biotechnology, Piscataway, NJ) as previously described.24 Approximately 1.0 x I09 cells were added to 1.6 g (dry weight) of hydrated microcarriers. Cells and microcarriers were incubated overnight in 150 ml of DMEM and 10% fetal bovine serum (FBS) at 37 C in 95% air/5% CO2.
Hollow Fiber Module Microcarrier-attached porcine hepatocytes were inoculated into the extra-fiber compartment of hollow fiber modules. Each hollow fiber module (Z22M-060-0 1 X; Microgon, Inc., Laguna Hills, CA) consisted of a polycarbonate cylinder (29.1 mm ID, 31.2 mm OD) containing 670 cellulose nitrate/cellulose acetate fibers (635 , ID, 760 , OD, wall thickness 62.5 u; 510 mm overall length, 445 mm potted length), with an extra-fiber volume of 177 ml. Total fiber internal surface area was 5,850 cm , external surface area was 7,010 cm2 and the pore diameter in the semi-permeable fiber wall was 0.2 j.
Charcoal Perfusion Column Supported by NIH grant DK38763-07. Presented at the 104th Annual Session ofthe Southern Surgical Association, Aventura, Florida. Address reprint requests to A. A. Demetriou, Cedars-Sinai Medical Center, Room 8215, North Tower, 8700 Beverly Blvd, Los Angeles, CA 90048. Accepted for publication January 11, 1993.
A column containing 150 g of cellulose-coated charcoal was used (Adsorba 15OC; Gambro Dialysatoren GmbH & Co., KG, Germany). Before use, each column was saturated with glucose and washed with 2 1 of heparinized saline.
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Experimental Animal Model of Liver Failure
Animal Liver Support System Configuration
A large-animal experimental model of ischemic liver failure, previously validated and extensively studied in our laboratory,25 was used. Under pentobarbital (30 mg/ kg, IV) anesthesia and mechanical (room air) ventilation, adult, male or female, mongrel dogs weighing 2330 kg underwent end-to-side portocaval shunts with placement of sutures around the common hepatic and gastroduodenal arteries and their accessory branches. The sutures were exteriorized and placed in subcutaneous pockets. Animals were allowed to recover and 72 hours later were re-anesthetized with pentobarbital and placed on oxygen-enriched room-air mechanical ventilation. Femoral venous and arterial catheters were placed for plasmapheresis, fluid administration, blood sample collection, and arterial pressure monitoring. The exteriorized arterial ligatures were applied after collection of baseline blood samples, and the animals were placed on the extracorporeal liver support systems.
The system (Fig. 1) consisted of a plasma separator, a transmission reservoir, a charcoal column, a hollow fiber module inoculated with microcarrier-attached porcine hepatocytes, an oxygenated water bath maintained at 37 C, four roller pumps (MasterFlex, Cole-Palmer, Chicago, IL), and oxygen-permeable silicone tubing (Baxter Healthcare, McGaw Park, IL). The primary mechanism of solute transport in a hollow fiber module is fluid convection (Starling flow) driven across the membrane by a trans-fiber pressure drop. The faster the axial flow rate is, the faster the Starling flow. Because plasma could not be removed from the filtration column at a rate higher than 30 ml/min, a transmission reservoir was introduced from which plasma recirculated in the BAL circuit at 200 ml/min. After recirculation through the BAL, plasma and red blood cells were reconstituted and returned to the animal at 30 ml/min via the venous cannula.
Animal Plasma Separation After cannulation (by groin cutdown) of the femoral artery and vein, animals were heparinized (100 U/kg, IV), and blood was removed through the venous cannula. Plasma was separated using a filtration column (Plasmaflo AP-05H; Asahi Medical Co., Apheresis Technologies, Inc., Palm Harbor, FL); at a blood flow of 150 ml/min, approximately 25-30 ml/min of plasma could be removed continuously without inducing thrombocytopenia and hemolysis.
Animal Experimental Study Design Two groups of animals were studied. Group I animals (n = 7) were treated with a BAL system consisting of a charcoal plasma perfusion column and a hollow-fiber module inoculated with 5-6 x 109 viable microcarrierattached porcine hepatocytes. Group II animals (n = 6) were treated with charcoal plasma perfusion alone. The number of cells used in the BAL, represented at least 50-60 g of the liver, i.e., at least 10% of the total liver weight of the dog (dog weight: 23-30 kg). Perfusion of each anesthetized animal was carried out for 6 hours. Blood was collected before and at hourly intervals after hepatic devascularization for determination of glucose, electrolytes, ammonia, lactate, lactic acid dehydrogenase (LDH), aspartate aminotransferase (AST), haptoglobin, prothrombin time, fibrinogen, and platelet count. All assays were carried out at the hospital clinical laboratory using standard methods. Two hours after hepatic devascularization, 0.5 mg/kg of indocyanin green (ICG) was administered intravenously and blood samples were obtained at 5-minute intervals for 20 minutes to determine ICG clearance. Plasma ICG levels were determined spectrophotometrically (absorbance at 810 nm). At the completion of the perfusion period, animals were killed with intravenous pentobarbital overdose.
Statistical Methods Figure 1. Schematic representation of the bioartificial liver (BAL) support system.
Data were analyzed statistically using unpaired Student's t-test.
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CLINICAL REPORT Clinical Presentation A 45-year-old male patient with alcohol and post-hepatitic (B and C) cirrhosis was admitted to the hospital with progressively worsening ascites and renal failure. On initial evaluation, the patient was icteric, dyspneic, alert, and oriented with mild hand tremor. His blood pressure was 90/50 mm Hg and his abdomen was distended. Admission laboratory values included: serum urea nitrogen: 100 mg/dl; creatinine: 5.7 mg/dl; sodium: 114 meq/ L; total bilirubin: 5.6 mg/dl; prothrombin time: 16 sec; and partial thromboplastin time: 46 sec. Despite intensive, supportive medical treatment, the patient's condition deteriorated rapidly; he became comatose, unresponsive to painful stimuli (serum ammonia increased from 40 to 238 ,umol/l) and required endotracheal intubation and mechanical ventilatory support. His urine output became scanty (< 10 ml/hr), and coagulopathy developed. The patient had been evaluated for liver transplantation in the past and was considered to be an unsuitable candidate. After approval from the appropriate institutional committees and obtaining permission from the next of kin, it was decided to treat the patient with an experimental extracorporeal liver support system using porcine hepatocytes alone. Thirty hours later, BAL treatment was repeated, this time using a system consisting of a module loaded with matrix-attached hepatocytes and a charcoal column.
Hepatocyte Processing Porcine hepatocytes were harvested and attached to microcarriers as described earlier. They were cryopreserved in DMEM with 10% fetal bovine serum and 5% dimethylsulfoxide at -70 C. Microcarrier-attached hepatocytes were thawed, washed three times with DMEM, and suspended in serum-free DMEM without glutamine. Cell viability was assessed using the trypan blue exclusion test.
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nected to the patient through a double lumen catheter inserted into the superficial femoral vein. Blood was removed, and the separated plasma was circulated through the hepatocyte-loaded hollow fiber module at a flow rate of 90-105 ml/min; subsequently, plasma was reconstituted with the patient's own blood cells and returned to him. No heparin was used. After a 6-hour treatment period, plasmapheresis was discontinued and the catheter was left in place. Thirty hours later, the patient was treated again for another 5 hours, this time using a coated charcoal column and a hepatocyte-inoculated module as described earlier.
RESULTS Animal Studies Hepatocyte viability after harvesting with EDTA/collagenase portal vein perfusion was consistently greater than 95%. The yield of viable hepatocytes from a single porcine liver perfusion was always greater than 2 x 1010. Isolated cells were incubated with microcarriers overnight. Hepatocyte viability remained unchanged after the incubation period and most cells (> 75%) were attached to the microcarriers (Fig. 2). Cells were used immediately after the attachment period. No technical problems were encountered during either BAL or charcoal treatment. There was no hemolysis in both groups of animals; at the end of the 6-hour perfusion period, haptoglobin levels remained normal (< 150 mg/dl). However, thrombocytopenia (platelet count less than 100,000 but greater than 50,000/cm3) was seen in 3 of the 13 animals (one in Group I and two in Group II). In both groups of animals, as expected, there was a progressive, significant increase in the activity of serum
Charcoal Column The charcoal column used was Adsorba 300C
(Gambro).
Construction of BAL/Plasmapheresis Approximately 6 x 109 viable microcarrier-attached porcine hepatocytes were inoculated into the extra-fiber chamber of a hollow fiber module as described above. A plasmapheresis unit (Cobe, Lakewood, CO) was con-
Figure 2. Isolated porcine hepatocytes depicted after overnight attachment to collagen-coated dextran microcarriers.
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Rozga and Others
506
-
m
Base
1 hr
2 hr
3 hr
4 hr
5 hr
6 hr
99 ± 7 100 ± 6
109 ± 7 88 ± 10
97 ± 10* 53 ± 12
75 ± 10* 27 ± 14
69 ± 13* 17 ± 10
60 ± 13* 9 ± 4
50 ± 12* 4 ± 1
95 ± 8 105 ± 9
124 ± 11 297 ± 89
170 ± 17* 286 ± 43
168 ± 21* 293 ± 57
170 ± 20* 377 ± 102
172 ± 17* 461 ± 140
164 ± 16* 440 ± 110
Group Glucose (mg/dL) BAL Charcoal Ammonia (,umol/L) BAL Charcoal Lactate (mmol/L) BAL Charcoal Prothrombin time (sec) BAL Charcoal Fibrinogen (mg/dL) BAL Charcoal *
1.8 ± 0.2 1.5 ± 0.1
3.4 ± 0.5 4.3 ± 0.5
4.9 ± 1.0 5.9 ± 0.5
5.1 ± 1.1 7.7 ± 0.5
5.2 ± 9.7 ±
1.2* 0.5
5.3 ± 11.6 ±
0.4
5.4 ± 10.7 ±
1.0 0.9
11.3± 0.5 13.3 ± 1.1
10.6± 0.3 11.0 ± 0.4
10.4± 0.2 10.5 ± 0.3
10.7 ± 0.3
11.1 ± 11.6 ±
0.6 0.6
11.6± 13.4 ±
0.7 1.3
12.0± 17.0 ±
0.6* 2.3
194 ± 18 155 ± 14
159 ± 26 115 ±20
140 ±26 99 ± 17
11.2 ± 0.4
126 ± 22 81 ± 19
130 ± 26 77 ± 17
1.2*
110 ± 15 67 ± 14
91 ± 16 63 ± 14
p < 0.05 or less (unpaired Student's t-test).
LDH (Group I: 585 ± 24; Group II: 492 ± 109 mlU/ml) and AST (Group I: 348 ± 74; Group II: 317 ± 106 mU/ ml) after 6 hours of treatment. The differences in enzyme values between the two groups were not statistically significant, suggesting similar degree ofliver injury. At 4, 5, and 6 hours of treatment, serum ammonia and lactate levels were significantly decreased and serum glucose was significantly increased in Group I compared with Group II (Table 1). Importantly, in Group I animals, after an initial rise in ammonia levels, there was no further increase and four of seven animals remained normoglycemic throughout the 6-hour treatment period (Ta-
2.4
2.2
ble 1). In contrast, Group II dogs became hypoglycemic early and had a progressive rise in serum ammonia levels (Table 1). Similarly, Group I dogs had a normal prothrombin time at 6 hours, whereas Group II dogs had a significantly prolonged prothrombin time throughout the study period. The difference in plasma fibrinogen levels between the two groups was not statistically significant. ICG clearance was more than 20% at 15 minutes and more than 40% at 20 minutes in Group I dogs, whereas Group II animals showed near-total dye retention (Figure 3). Group I animals remained hemodynamically stable throughout the treatment period with a mean systolic blood pressure of 105 ± 11 mm Hg at 6 hours compared to Group II dogs (52 ± 8 mm Hg; P < 0.020). Hepatocyte viability in the liver support module at the end of the 6-hour treatment period, was greater than 90%.
Clinical Report
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The patient remained stable throughout both treatment periods. There was no evidence ofbleeding or oozing from any sites during both treatments. After the first treatment, the patient's mental status did not change, in spite of a reduction in serum ammonia from 238 to 114 mg/dl; in addition, the patient became more stable hemodynamically and his urine output increased from 425 ml for the 24-hour period before treatment, to 2,650 ml for the 24-hour period after treatment. The patient continued to improve for another 12 hours after treatment and then his condition began to deteriorate again; his urine
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output decreased to less than 10 ml/hr, he remained unresponsive, and he required mechanical ventilatory support.
At 30 hours after the first treatment, a second BAL treatment was initiated, this time using plasmapheresis
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and combined charcoal and hepatocyte perfusion for 5 hours. The patient tolerated the treatment well. This time, a dramatic change in the patient's mental status was noted which was accompanied by a decrease in serum ammonia to 58 mg/dl. The patient woke up, his ventilatory status improved, and his urine output increased (2,880 during the following 24-hour period). Within 24 hours after the second treatment, the patient was alert and responsive with continuously improving hemodynamic, renal, and respiratory functions. He was extubated in the subsequent days and was discharged from the intensive care unit. After the second BAL treatment, there was a decrease in serum creatinine from 6.4 to 4.0 mg/dl, and the serum urea nitrogen remained stable at 100 mg/dl. The patient's total bilirubin decreased from 8.0 to 3.8 mg/dl. No other biochemical changes were noted during both treatment periods. There were no changes in plasma clotting factors (V, VII, VIII, IX, X), fibrinogen, PT, PTT, glucose, lactic acid, and transaminases. Several changes in plasma amino acid levels, after each treatment period, were noted. These are summarized in Figure 4. There was a group of amino acids in which a very substantial increase (100%-400% greater than normal) was noted before initiation of treatment; after BAL treatment, the plasma levels of these amino acids decreased (Fig. 4A). The plasma levels of the aromatic amino acids phenylalanine and tyrosine were increased and their levels decreased after BAL treatment (Fig. 4B). Tyrosine decreased after the first treatment and continued to decrease with the second treatment; phenylalanine decreased after the first treatment, there was a transient increase in the interval between treatments, followed by lowering of the plasma level again after the second treatment. After the first BAL treatment, there was slight decrease in the levels of the branched chain amino acids (Fig. 4C); however, during the second treatment, there was a transient (3 hr) increase in the levels of both valine and leucine. No changes in the levels of other amino acids were noted. Approximately 3 weeks after he was treated with the BAL system, the patient developed pneumonia, another episode of acute respiratory distress and re-accumulation of ascites with hepatic decompensation. At this time, it was decided not to continue supportive measures and the patient died several days later.
Bw lh
Figure 4. Plasma amino acid changes (AM) before and after each BAL treatment. A: Plasma levels of threonine (Thr), arginine (Arg), methionine (Meth), tryptophan (Trp) and lysine (Lys); normal values represent plasma amino acid levels in normal volunteers. B: Plasma levels of the aromatic amino acids phenylalanine (Phe) and tyrosine (Tyr). C: Plasma levels of the branched chain amino acids valine (Val), leucine (Leu) and isoleucine (Iso). (B1 and B2 -baseline values before treatment).
DISCUSSION Charcoal hemoperfusion has been used to treat severe acute liver failure with mixed results. 18,20,21,26 Although the technique has some beneficial effects,18'19'27 a con-
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Rozga and Others
trolled prospective clinical study has not demonstrated significant clinical advantages of the technique.2" Other methods that relied primarily upon blood detoxification showed limited success as well. Due to the complexity and vast number of metabolic and other physiologic functions provided by the liver and the need for broad metabolic support in acute liver failure, construction of an extracorporeal liver support system may require utilization of viable isolated hepatocytes rather than either specific cell components or enzymes.
We have previously demonstrated that attachment of hollow fiber module inoculated with normal hepatocytes to Gunn rats (which are unable to conjugate bilirubin) via arterial and venous cannulas, resulted in the appearance of bilirubin conjugates in their bile.28 In subsequent experiments, using dogs with severe irreversible acute ischemic liver failure, we demonstrated that treatment with a hollow fiber module inoculated with cryopreserved matrix-attached allogeneic and xenogeneic (porcine) hepatocytes, resulted in significant beneficial effects. These effects included decreased serum ammonia, lactate and pH levels and increased serum glucose levels and systolic blood pressure in hepatocyte-treated animals compared with controls.25 This experiment compared the efficacy of a hybrid (charcoal column and hepatocyte module) liver support system with that of a system using charcoal alone. Normal porcine hepatocytes were used because they will be the most likely xenogeneic cells to be used in future clinical trials. To optimize their function and maintain differentiation, cells were anchored to a collagen monolayer on the surface of microcarriers. In addition, we hypothesized that by placing the charcoal column before the hepatocyte module in the circuit, we would not only enhance the detoxifying capability of BAL, but also protect the normal porcine hepatocytes from the possible toxic effects of hepatic failure plasma.29'30 To avoid hemolysis and platelet depletion associated with whole blood perfusion, a plasmapheresis system was used which allowed perfusion of the hepatocytes with plasma only. In addition, it eliminated direct cell-cell interactions between host blood cells and xenogeneic liver cells. Our results demonstrated that dogs with acute ischemic liver failure treated with charcoal plasma perfusion alone, developed progressive hyperammonemia, hypoglycemia, acidosis and hypotension; in addition, they had a prolonged prothrombin time and a near-total retention of ICG. In contrast, hybrid BAL-treated dogs showed, after an initial rise (1 and 2 hr), no further increase in blood ammonia and 4 of 7 animals remained normoglycemic throughout the treatment period. In addition, only a modest increase in lactate levels was oba
Ann. Surg. * May 1993
served, prothrombin time remained normal throughout the treatment period and animals were able to maintain increased systolic blood pressure. The hybrid BAL provided a significant level of detoxifying, metabolic, and hemodynamic support. After 6 hours on the BAL system, hepatocyte viability and attachment to microcarriers remained high, suggesting that microcarrier-attached hepatocytes were effectively perfused with oxygenated plasma. Animals tolerated BAL treatment well and no hypersensitivity or other acute immunologic reaction was noted. This could be due to the immunosuppressive effect of severe liver failure. However, after repeated BAL plasma perfusions, xenogeneic hepatocytes may either have a detrimental effect on the treated animals or could be destroyed by circulating antibodies in the plasma. If that is the case, techniques would have to be used (i.e., binding ofcirculating antibodies, immunosuppression, use of hollow-fibers with molecular weight cutoff less than 100,000) to neutralize the antibodies. In this report, we used two extracorporeal liver support system treatments. Initially, the patient was treated with a system using porcine hepatocytes alone. There was no adverse effect from the treatment and there was some evidence of improvement in renal function. The second treatment was initiated using a combined hepatocyte/charcoal BAL system. A very dramatic change in mental status was noted after the second treatment period. There was some concern about the patient developing a hypersensitivity reaction during the second treatment with porcine hepatocytes, but no adverse effects were noted. Some interesting, and possibly beneficial, clinical and biochemical effects occurred after BAL treatment of this patient. However, it is difficult to draw any conclusions as to the efficacy of this treatment. A prospective study is now in progress using BAL hepatocyte modules and charcoal filters, either alone or in combination, to treat patients with severe liver failure. In summary, we have developed a novel hybrid extracorporeal liver support system, using plasma separation, high-performance sequential perfusion through a column loaded with activated cellulose-coated charcoal particles and through a hollow-fiber module with viable matrix-anchored xenogeneic hepatocytes. Our animal data suggest that such a hybrid system can provide both detoxifying and synthetic liver functions and is superior to charcoal plasma perfusion alone. A single clinical case report is presented; adverse effects from the BAL treatment did not occur in the patient, and the data generated suggest that there was a beneficial effect. Further work is in progress both in the laboratory to further define and improve the BAL system and clinically to prospectively examine the efficacy of the hybrid BAL system in treating patients with severe hepatic failure.
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Discussion DR. WILLIAM C. MEYERS (Durham, North Carolina): What we've heard by Dr. Demetriou seems a very simple and straightforward experiment and those are usually the best types of experiments. Dr. Demetriou studied this problem for over 10 years before publishing a paper and is reaping in the literature the benefits of that, and now we're seeing the practical consequences of his tremendous research. He is to be considered the leader in the bioartificial liver in this country and the world, and is setting forth the example for us all in attempting other methods of liver dialysis. Recently, really 2 weeks ago, in our institution, myself, Dr. McCann, who's in the audience, and a number of others at Duke had a patient admitted with fulminant hepatitis B. He was 20 years old and promptly over about a 6-hour period developed a Grade V coma. He was areflexic except for a gag, a corneal and cough reflex. He remained that way for 24 hours and was on the liver transplant list and no liver came up. So we started a sequence of pig liver dialysis performed ex vivo using pigs harvested from the vivarium by Dr. Chari and the use of a veno-venous bypass circuit, two catheters, one in the femoral vein, one in the jugular vein, an ECMO, and a heat exchanger. After a series offive livers, the last one being two livers in parallel because of the small size of the livers, the patient began to wake up over about a 5-day period. And then the past week we were able to put a human liver in him and he seems to be normal. I think that this is really
