Simon Horslen

Pediatric Transplantation in the United States, 1995–2004

Solid organ transplantation is accepted as a standard lifesaving therapy for end‐stage organ failure in children. This article reviews trends in pediatric transplantation from 1996 to 2005 using OPTN data analyzed by the Scientific Registry of Transplant Recipients. Over this period, children have contributed significantly to the donor pool, and although the number of pediatric donors has fallen from 1062 to 900, this still accounts for 12% of all deceased donors. In 2005, 2% of 89 884 candidates listed for transplantation were less than 18 years old; in 2005, 1955 children, or 7% of 28 105 recipients, received a transplant. Improvement in waiting list mortality is documented for most organs, but pretransplant mortality, especially among the youngest children, remains a concern. Posttransplant survival for both patients and allografts similarly has shown improvement throughout the period; in most cases, survival is as good as or better than that seen in adults. Examination of immunosuppressive practices shows an increasing tendency across organs toward tacrolimus‐based regimens. In addition, use of induction immunotherapy in the form of anti‐lymphocyte antibody preparations, especially the interleukin‐2 receptor antagonists, has increased steadily. Despite documented advances in care and outcomes for children undergoing transplantation, several considerations remain that require attention as we attempt to optimize transplant management.

Natural History of Pediatric Intestinal Failure: Initial Report from the Pediatric Intestinal Failure Consortium

OBJECTIVE To characterize the natural history of intestinal failure (IF) among 14 pediatric centers during the intestinal transplantation era. STUDY DESIGN The Pediatric Intestinal Failure Consortium performed a retrospective analysis of clinical and outcome data for a multicenter cohort of infants with IF. Entry criteria included infants <12 months receiving parenteral nutrition (PN) for >60 continuous days. Enteral autonomy was defined as discontinuation of PN for >3 consecutive months. Values are presented as median (25th, 75th percentiles) or as number (%). RESULTS 272 infants with a gestational age of 34 weeks (30, 36) and birth weight of 2.1 kg (1.2, 2.7) were followed for 25.7 months (11.2, 40.9). Residual small bowel length in 144 patients was 41 cm (25.0, 65.5). Diagnoses were necrotizing enterocolitis (71, 26%), gastroschisis (44, 16%), atresia (27, 10%), volvulus (24, 9%), combinations of these diagnoses (46, 17%), aganglionosis (11, 4%), and other single or multiple diagnoses (48, 18%). Prescribed medications included oral antibiotics (207, 76%), H2 blockers (187, 69%), and proton pump inhibitors (156, 57%). Enteral feeding approaches varied among centers; 19% of the cohort received human milk. The cohort experienced 8.9 new catheter-related blood stream infections per 1000 catheter days. The cumulative incidences for enteral autonomy, death, and intestinal transplantation were 47%, 27%, and 26%, respectively. Enteral autonomy continued into the fifth year after study entry. CONCLUSIONS Children with IF endure significant mortality and morbidity. Enteral autonomy may require years to achieve. Improved medical, nutritional, and surgical management may reduce time on PN, mortality, and need for transplantation.

Studies of Pediatric Liver Transplantation (SPLIT) : Year 2000 outcomes

Background. Initiated in 1995, the Studies of Pediatric Liver Transplantation (SPLIT) registry database is a cooperative research network of pediatric transplantation centers in the United States and Canada. The primary objectives are to characterize and follow trends in transplant indications, transplantation techniques, and outcomes (e.g., patient/graft survival, rejection, growth parameters, and immunosuppressive therapy.) Methods. As of June 15, 2000, 29 centers registered 1144 patients, 640 of whom received their first liver-only transplant while registered in SPLIT. Patients are followed every 6 months for 2 years and yearly thereafter. Data are submitted to a central coordinating center. Results. One/two-year patient survival and graft loss estimates are 0.85/0.82 and 0.77/0.72, respectively. Risk factors for death include: in ICU at transplant (relative risk (RR)=2.63, P <0.05) and height/weight deficits of two or more standard deviations (RR=1.67, P <0.05). Risk factors for graft loss include: in ICU at transplant (RR=1.77, P <0.05) and receiving a cadaveric split organ compared with a whole organ (RR=2.3, P <0.05). The percentage of patients diagnosed with hepatic a. and portal v. thrombosis were 9.7% and 7%, respectively; 15% had biliary complications within 30 days. At least one re-operation was required in 45%. One/two-year rejection probability estimates are 0.60/0.66. Tacrolimus, as primary therapy posttransplant, reduces first rejection risk (RR=0.70, P <0.05). Eighty-nine percent of school-aged children are in school full-time, 18 months posttransplant. Conclusions. This report provides one of the first descriptions of characteristics and clinical courses of a multicenter pediatric transplant population. Observations are subject to patient selection biases but are useful for generating hypothesis for future studies.

Collaborative strategies to reduce mortality and morbidity in patients with chronic intestinal failure including those who are referred for small bowel transplantation.

Intestinal transplant wait-list mortality is higher than for other organ transplants. The objective of this workshop was to identify the main problems contributing to high mortality in adults and children candidates for intestinal transplantation and provide recommendations on how to correct them. Outcome. To facilitate this, 63 relevant articles identified from the medical literature from 1987 to 2007 were reviewed. Consensus was achieved on several important definitions relevant to this review. For children and adults on parenteral nutrition (PN) the main mortality risk factors were identified as were the main risks of mortality for those on the waiting list for intestinal transplants. Recommendations. (1) Primary care givers managing intestinal failure patients should establish a link with an intestinal failure programs early and collaboration with intestinal failure programs should be initiated for patients whose PN requirements are anticipated to be more than 50% 3 months after initiating PN; (2) intestinal failure programs should include both intestinal rehabilitation and intestinal transplantation or have active collaborative relationships with centers performing intestinal transplantation; (3) National registries for intestinal failure patients should be established and organizations that provide home PN solutions should be expected to participate. Conclusion. There are many unresolved issues in adults and children with PN dependent intestinal failure. To address these, a key recommendation of this group is to establish national intestinal failure databases that can support multicenter studies and lead to the adoption of universally accepted standards of patient care with the goal of improving outcomes in all long-term intestinal failure patients including those requiring intestinal transplantation.

A multidisciplinary approach to the treatment of intestinal failure

Intestinal failure is most commonly treated by the administration of total parenteral nutrition (TPN). In some patients, however, surgical therapy may increase the ability to use the intestine for nutrition and thereby decrease the complications of TPN therapy. A multidisciplinary comprehensive intestinal failure program was initiated at the University of Nebraska Medical Center in October 2000. Here we describe the surgical approaches to patients with short bowel syndrome and the subsequent impact on the need for TPN and on survival. Fifty patients (children = 30, adults = 20) underwent surgical procedures to restore intestinal continuity (n = 5), repair enterocutaneous fistulas (n = 5), resect dysmotile or strictured/obstructed bowel segments or mesenteric desmoid tumors (n = 7), stricturoplasty (n = 2), Bianchi tapering and lengthening (n = 20), serial transverse enteroplasty (n = 8), and other operations (n = 8). Of these 50 patients, three patients did not require TPN after surgical intervention and seven had remnant small bowel anatomy that precluded TPN weaning (e.g., end duodenostomy) and were listed for transplantation or continued on full TPN support. Of the 40 remaining patients, most received the majority of calories fromTPNat the time of referral, i.e., mean calories fromTPN _ 90%. Subsequent to the surgical and medical therapy, 26 (65%) have been completely weaned off TPN. In addition, 10 had substantial decreases in their TPN requirements (i.e., from 85% of calories from TPN at onset decreased to a median 35% of required calories at most recent follow-up). Four patients remained on the same amount of TPN support. Four of the seven patients listed for transplantation underwent successful transplantation. Despite the complications of short bowel syndrome, 86% (n = 43) of the patients are alive and well at a mean follow-up of 2 years. Patient deaths occurred primarily in those listed or eligible for transplantation and were related to advanced liver disease (n = 3), gastrointestinal hemorrhage (n = 1), or line sepsis (n = 1). Two other patients died, one from influenza A infection and one from unknown cause at home, months after complete discontinuation of TPN. In this series of patients with short bowel syndrome, surgical intervention led to weaning or discontinuation of TPN support in 85% of patients. An organized multidisciplinary approach to the patient with short bowel syndrome is recommended.

Safety and Immunogenicity of Varicella-Zoster Virus Vaccine in Pediatric Liver and Intestine Transplant Recipients

Primary varicella‐zoster virus (VZV) infections following organ transplantation may cause significant morbidity. We examined the safety and immunogenicity of Varivax® after transplantation as a potential prophylactic tool. Pediatric liver and intestine transplant recipients without history of chickenpox received one dose of Varivax®. VZV humoral and cellular immunity were assessed before and ≥12 weeks after vaccination. Adverse events (AE) and management of exposure to wild type VZV were monitored. Sixteen VZV‐naïve subjects, 13–76 months of age, at 257–2045 days after transplantation were immunized. Five children developed mild local AE of short duration. Four subjects developed fever and four developed non‐injection site rashes, three of whom received acyclovir. Liver enzymes did not increase during the month after vaccination. Eighty‐seven percent and 86% of children developed humoral and cellular immunity, respectively. There were five reported exposures to varicella in four children, none of which resulted in chickenpox. One subject received VZV‐immunoglobulin and another subject with liver enzyme elevations after exposure received acyclovir; all remained asymptomatic. Varivax® was safe and immunogenic in pediatric liver and intestine transplant recipients. Larger studies are needed to establish the efficacy and role of varicella vaccination after transplantation.

Intestine transplantation in the United States, 1999-2008.

Improving short‐term results with intestine transplantation have allowed more patients to benefit with nearly 700 patients alive in the United States with a functioning allograft at the end of 2007. This success has led to an increase in demand. Time to transplant and waiting list mortality have significantly improved over the decade, but mortality remains high, especially for infants and adults with concomitant liver failure. The approximately 200 intestines recovered annually from deceased donors represent less than 3% of donors who have at least one organ recovered. Consent practice varies widely by OPTN region. Opportunities for improving intestine recovery and utilization include improving consent rates and standardizing donor selection criteria. One‐year patient and intestine graft survival is 89% and 79% for intestine‐only recipients and 72% and 69% for liver‐intestine recipients, respectively. By 10 years, patient and intestine survival falls to 46% and 29% for intestine‐only recipients, and 42% and 39% for liver‐intestine, respectively. Immunosuppression practice employs peri‐operative antibody induction therapy in 60% of cases; acute rejection is reported in 30%–40% of recipients at one year. Data on long‐term nutritional outcomes and morbidities are limited, while the cause and therapy for late graft loss from chronic rejection are areas of ongoing investigation.

Extracorporeal liver perfusion using human and pig livers for acute liver failure.

Background. Patients with fulminant hepatic failure (FHF) often die awaiting liver transplantation.Extracorporeal liver perfusion (ECLP) has been proposed as a method of “bridging” such patients to transplantation. We report the largest experience to date of ECLP using human and porcine livers in patients with acute liver failure. Methods. Patients with FHF unlikely to survive without liver transplantation were identified. ECLP was performed with human or porcine livers. Patients underwent continuous perfusion until liver transplantation or withdrawal of support. Two perfusion circuits were used: direct perfusion of patient blood through the extracorporeal liver and indirect perfusion with a plasma filter between the patient and the liver. Findings. Fourteen patients were treated with 16 livers in 18 perfusion circuits. Nine patients were successfully “bridged” to transplantation. ECLP stabilized intracranial pressure (ICP) and cerebral perfusion pressure (CPP). Arterial ammonia levels fell from a median of 146 to 83 &mgr;mol/liter within 12 hr and this reduction was maintained at least 48 hr. Pig and human ECLP lowered ammonia levels equally. Serum bilirubin levels also fell from a median of 385 to 198 &mgr;mol/liter over the first 12 hr but the response was not sustained as well with porcine livers. There was no immunological benefit to using the the filtered perfusion circuit. Interpretation. These data demonstrate that ECLP is safe and can provide metabolic support for comatose patients with fulminant hepatic failure for up to 5 days. While labor and resource intensive, this technology is available to centers caring for patients with acute liver failure and deserves wider evaluation and application.

Intravenous N-acetylcysteine in pediatric patients with nonacetaminophen acute liver failure: A placebo-controlled clinical trial

N‐acetylcysteine (NAC) was found to improve transplantation‐free survival in only those adults with nonacetaminophen (non‐APAP) acute liver failure (ALF) and grade 1‐2 hepatic encephalopathy (HE). Because non‐APAP ALF differs significantly between children and adults, the Pediatric Acute Liver Failure (PALF) Study Group evaluated NAC in non‐APAP PALF. Children from birth through age 17 years with non‐APAP ALF enrolled in the PALF registry were eligible to enter an adaptively allocated, doubly masked, placebo‐controlled trial using a continuous intravenous infusion of NAC (150 mg/kg/day in 5% dextrose in water [D5W]) or placebo (D5W) for up to 7 days. The primary outcome was 1‐year survival. Secondary outcomes included liver transplantation‐free survival, liver transplantation (LTx), length of intensive care unit (ICU) and hospital stays, organ system failure, and maximum HE score. A total of 184 participants were enrolled in the trial with 92 in each arm. The 1‐year survival did not differ significantly (P = 0.19) between the NAC (73%) and placebo (82%) treatment groups. The 1‐year LTx‐free survival was significantly lower (P = 0.03) in those who received NAC (35%) than those who received placebo (53%), particularly, but not significantly so, among those less than 2 years old with HE grade 0‐1 (NAC 25%; placebo 60%; P = 0.0493). There were no significant differences between treatment arms for hospital or ICU length of stay, organ systems failing, or highest recorded grade of HE. Conclusion: NAC did not improve 1‐year survival in non‐APAP PALF. One‐year LTx‐free survival was significantly lower with NAC, particularly among those <2 years old. These results do not support broad use of NAC in non‐APAP PALF and emphasizes the importance of conducting controlled pediatric drug trials, regardless of results in adults. (HEPATOLOGY 2013)

Detection of acetaminophen protein adducts in children with acute liver failure of indeterminate cause

OBJECTIVE. Acetaminophen cysteine protein adducts are a widely recognized correlate of acetaminophen-mediated hepatic injury in laboratory animals. The objective of this study was to use a new assay for the detection of acetaminophen cysteine protein adducts in children with acute liver failure to determine the role of acetaminophen toxicity in acute liver failure of unknown cause. METHODS. Serum samples from children with acute liver failure were measured for acetaminophen cysteine protein adducts using high-performance liquid chromatography with electrochemical detection. For comparison, samples from children with well-characterized acetaminophen toxicity and children with known other causes of acute liver failure also were measured for acetaminophen cysteine protein adducts. The analytical laboratory was blinded to patient diagnoses. RESULTS. Acetaminophen cysteine protein adduct was detected in 90% of samples from children with acute liver failure that was attributed to acetaminophen toxicity, 12.5% of samples from children with acute liver failure of indeterminate cause, and 9.6% of samples from children with acute liver failure that was attributed to other causes. Adduct-positive patients from the indeterminate cause subgroup had higher levels of serum aspartate aminotransferase and alanine aminotransferase and lower levels of bilirubin. Adduct-positive patients also had lower rates of transplantation and higher rates of spontaneous remission. CONCLUSIONS. A small but significant percentage of children with acute liver failure of indeterminate cause tested positive for acetaminophen cysteine protein adducts, strongly suggesting acetaminophen toxicity as the cause of acute liver failure. An assay for the detection of acetaminophen cysteine protein adducts can aid the diagnosis of acetaminophen-related liver injury in children.