Fifty-six hours and 108 hours after listing and subsequent bridging with MARSmini, liver transplantation was successfully performed. During two MARS cycles in each child, patient 1 remained haemodynamically stable, did not require haemofiltration between MARS sessions, and her PELD score dropped from 23 to 10. Patient 2 required markedly less vasopressor support (norepinephrine was decreased from 9 to 1 μg/kg/min and dobutamine from 10 to 5 μg/kg/min) and parenteral fluid (from 1000 ml to 100 ml per hour), accompanied by a drop in her PELD score from 24 to 19. Patient 2 was off haemofiltration 1 week after LTx, and both patients could be extubated after 1 to 3 days. Neurologic recovery was excellent on discharge after 3 weeks. Liver histology demonstrated end stage liver cirrhosis in both patients and raised liver copper (720 μg/g dry weight in patient 1).
Laboratory data revealed several trends that deserve clinical attention. Although the capacity of the albumin circuit to remove different substances varied intra- and inter-individually, the qualitative analysis of the removed factors was consistent (Table 1). As anticipated, considerable amounts of toxic metabolites, tissue-damaging nitrate and proinflammatory cytokines in the recirculating albumin circuit were transferred, with exception of hyaluronic acid, an extracellular marker associated with liver damage. On the other hand, albumin circuit and dialysate were also removing 9 of 10 growth factors (only excluding CBG) and essential precursors to glutathione synthesis. Binding to the absorbers was detected for amino acids, lactate and 6 of 10 examined hepatic growth factors.
Relative transfer from blood to albumin compartment was high for all metabolites, amino acids, copper and nitrate (median, 34-167%), and lower for cytokines (median, 3.7-10%) (Table 2). Among hepatic growth factors, 4 of 10 factors were consistently transferred at a proportion of greater than 20% (median): cortisol, TGF-β1, IGF-1 and angiogenin. However, transfer of major liver regeneration factors HGF and IL-6 was less than 10% (median), and albumin circuit levels of EGF and VEGF did not increase (Tables 2 and 3).
Notably, considerable removal of a substance was not necessarily accompanied by a decrease of the corresponding blood level (Fig. 1A, B). Whereas reduced blood copper levels of patient 1 were associated with an only moderate increase of albumin copper levels (Fig. 1A), substantially enhanced albumin copper levels (reaching a plateau after 3 hours MARS treatment) yielded no decline of corresponding blood levels in patient 2 (Fig. 1B), who required continuous haemofiltration. However, diuresis of patient 1 was maintained at 2400 mL/d, which contained 41-52 μmol/L urine copper. Consistently decreased blood levels after each MARS treatment were measured for 3 of 6 metabolites, 3 of 6 inflammatory mediators and 1 of 10 growth factors (Table 1).
Data on individual blood levels (Table 3) showed that MARS treatment can involve constantly high bilirubin levels (patient 1) or increasing ammonia and copper levels (patient 2). With regard to side-effects of extracorporeal membrane treatment, no general activation of the inflammatory or complement cascade was observed, and drop of platelets associated with extracorporeal treatment did not require substitution (patient 1: 67/nl to 46/nl platelets; patient 2: 124/nl to 106/nl platelets; the numbers were assessed before the first and after the second treatment with MARS in each patient). No additional substitution of fresh frozen plasma was required under ACT-directed heparinisation, and clotting factors II, V, VII, protein C and S remained stable under MARS therapy (data not shown). Composition of amino-acids changed, reflected by improvement of the Fischer ratio, a marker associated with hepatic encephalopathy (13). Interestingly, during MARS bridging, an increase of hepatic growth factors EGF, TGF-β1 and IGF-1 was detected in serum of both patients.
We have examined the capacity of an extracorporeal adsorption system (MARSmini) to remove candidate substances in two paediatric patients with fulminant hepatic failure of nearly identical aetiology and severity. Taking in consideration the limitations of only four procedures (i.e., dependence on variations in production, equilibration, and adsorbing capacity of the circuit), we believe that indices for important trends can be derived from this pilot study. The novel concept of using albumin as a circulating dialysate purified by adsorbents has been claimed to selectively remove protein-bound-toxins and water-soluble metabolites, being impermeable to valuable proteins, hormones and clotting factors (7). However, although MARSmini application as a bridging device appeared safe and neurologic outcome was excellent in these patients, we clearly demonstrated that not only metabolites and cytokines, but also essential hormones and growth factors are removed by MARS, the most selective form of ELS.
This may have important clinical implications for wider application in children. In a recent, systematic review of randomised trials with 483 patients, the Cochrane group concluded that ELS had no significant effect on mortality compared with standard medical therapy in patients with acute liver failure (6). Lack of efficacy on neurologic outcome or liver restoration was also reported in a series of 49 children with FHF treated with plasmapheresis, an unselective method of detoxification, concomitantly removing essential growth factors and hormones (14). Transfer of growth factors could affect mortality and restrain liver regeneration, as indicated by the vital role of HGF, IL-6, or TNF-α in animal models (5) and significance of adrenal insufficiency in patients with acute hepatic failure (15). The value of protective factors present in plasma from patients with FHF has been attributed to proliferation, cytochrome P450-activity, and reversal of oxidative stress in human liver cells (16). Candidate factors include hormones (4), hepatic growth factors (5), and anti-oxidant precursors (16) (i.e., all factors, which are removed by different ELS to various degree).
In our patients, however, reduction of growth factor blood levels appeared moderate, and some factors (CBG, EGF, TGF-β1, IGF-1) increased over treatment time. Our data agree with recent reports from adults that MARS is capable of removing substantial amounts of metabolites, toxins, cytokines and nitric oxide in FHF. Such removal has been correlated with haemodynamic and neurologic improvement (2,7,17). Safety of MARS has been demonstrated in more than 1500 adult patients (7,9), and mortality could be significantly reduced in patients with acute-on-chronic liver failure, hepatorenal syndrome and liver cirrhosis with progressive hyperbilirubinaemia in randomised, controlled trials (7,8). On the other hand, detection of persisting, high or even increasing levels of ammonia, bilirubin, copper and cytokines following individual courses of a 6-hour treatment in our children could indicate persisting liver damage and also a limitation in detoxification capacity. Saturation of albumin binding capacity and differences in renal elimination may account for divergent pattern of copper distribution in our patients and those reported by other investigators during MARS therapy (18).
The clinical importance of our findings can only be explored in larger series examining patterns of candidate parameters in blood and dialysate under controlled conditions. Collaboration among institutions using ELS on a regular basis would greatly advance the critical evaluation of this promising therapy in paediatric hepatology. The possibility of improving the outcome of liver transplantation and facilitating the induction of liver regeneration are the key issues which should foster application of ELS in children.
Acknowledgments: The kits for the treatment of the patients were kindly donated by Teraklin AG. The authors thank the contributing laboratories of the University of Essen: hygienics (Dr. H. Diederichs), coagulation (Dr. S. Schimanski), clinical chemistry (Dr. L. Volbracht); our paediatric gastroenterologists (A. Hinsberger), nephrologists (A. Wingen, R. Büscher, B. Kranz), and transplant surgeons (PD Dr. M. Malago, Dr. S. Nadalin), Ms. B.K. Gunson for kind review of the manuscript; and Prof. M. Sachs for review of medical history.
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Keywords:© 2005 Lippincott Williams & Wilkins, Inc.
Liver failure; Cytokines; Hepatic growth factors; Artificial liver; Children