Risk of hearing impairment in pediatric liver transplant recipients: a single center study

As survival rates following liver transplantation have increased, health care providers must assess the impact of transplantation on dimensions other than traditional medical measures. Hearing impairment may adversely impact social, emotional, cognitive, academic, and speech and language development. We hypothesized that children who undergo liver transplantation are at risk for hearing impairment due to exposure to ototoxic drugs. We conducted a review of 74 children who had undergone liver transplantation between December 1996 and September 2000 at Cincinnati Children's Hospital Medical Center. Hearing was assessed at discharge by an audiologist using age and developmentally appropriate techniques. The principal outcome measure was sensorineural hearing impairment. Independent variables were age at transplantation, United Network for Organ Sharing (UNOS) status at transplantation, primary diagnosis, post-transplant length of hospital stay, days of treatment with aminoglycosides, and days of treatment with loop diuretics. Eleven of 74 children (15%) had sensorineural hearing loss, of whom four had severe to profound hearing loss. Multivariate analyses showed that the adjusted relative risk for hearing loss in patients with hepatoblastoma was 66 and that there was a 5% increase risk for hearing loss for each additional day of hospitalization. Age at transplantation, UNOS status, and days of treatment with loop diuretics or aminoglycosides did not achieve significance in the model. Sensorineural hearing impairment occurs in a subset of pediatric patients following liver transplantation. Patients with hepatoblastoma or those who experience prolonged hospitalization after transplantation are at increased risk. Our observations are of particular importance for pediatric liver transplant recipients since the median age at transplantation is 12-18 months, a critical period for language acquisition.     

Growth of liver allografts over time in pediatric transplant recipients

The liver's capacity to grow in response to metabolic need is well known. However, long‐term growth of liver allografts in pediatric recipients has not been characterized. A retrospective review of pediatric recipients at a single institution identified patients who had cross‐sectional imaging at 1, 5, and 10 years post‐transplant. Using volumetric calculations, liver allograft size was calculated and percent SLV were compared across the different time points; 18 patients ranging from 0.3 to 17.7 years old were identified that had imaging at 2 or more time points. Measured liver volumes increased by 59% after 5 years and 170% after 10 years. The measured liver volumes compared to calculated %SLV for these patients were 123 ± 37%, 97 ± 19%, and 118 ± 27% at 1, 5, and 10 years after transplant, respectively. Our data suggest that liver allografts in pediatric recipients increase along with overall growth, and reach SLVs for height and weight by 5 years post‐transplantation. Additionally, as pediatric recipients grow, the livers appear to maintain appropriate SLV.     

Lipid profile and cardiovascular risk factors in pediatric liver transplant recipients

Cardiovascular diseases induce long‐term morbidity and mortality of adult LT recipients. The aim of this retrospective study was to assess CVRF, lipid abnormalities, and atherosclerosis (appraised by c‐IMT), more than 10 yr after pediatric LT. Thirty‐one children who underwent LT between December 1990 and December 2000 were included. Median age at LT was 14 months (range 4–64), and median follow‐up after LT was 11.9 yr (range 9.0–17.3). In our cohort, obesity (9.7%) and treated hypertension (9.7%) were rare. None of the patients was smoker or diabetic. High TC and TG were both observed in 6.5% of the patients. The mean c‐IMT for male patients was 1.22 ± 1.55 and 1.58 ± 1.23 mm in female patients. Seven patients (22%) had a mean c‐IMT above +2 s.d. Values below the 5th percentile were noted for LDL‐cholesterol (58.1%), HDL‐cholesterol (25.8%), apolipoprotein B (40%), and apolipoprotein A1 (20%). LDL‐cholesterol and apolipoprotein B levels were significantly lower in patients treated by tacrolimus in comparison with CsA (p < 0.05). In conclusion, our results suggest that pediatric LT patients do not present significant CVRF; moreover, instead of hyperlipidemia, hypocholesterolemia (LDL‐C) is frequent and immunosuppressive therapy is probably the cause.     

Hypogammaglobulinemia in pediatric liver transplant recipients

Hypogammaglobulinemia has been reported after solid organ transplantation in adults, however immunoglobulin replacement [intravenous immunoglobulins (IVIG)] is only necessary in a minority of affected patients. We here present three pediatric patients with severe post-transplant hypogammaglobulinemia following liver transplantation (LTx) receiving a cyclosporine-based standard immunosuppression. Patient 1 was transplanted at the age of 10 months for biliary atresia. Eight weeks post-Ltx the serum IgG was 1.7 g/L. Patient 2 was transplanted at the age of 12 yr for acute liver failure. Four weeks post-Ltx the IgG dropped to 2.6 g/L. Patient 3 was transplanted at the age of 4 months for biliary atresia. Ten weeks post-Ltx severe hypogammaglobulinemia (IgG < 1.48 g/L) was diagnosed during a severe infectious complication. Patients 1 and 3 received a steroid bolus therapy for acute graft rejection. All patients had normal IgG concentrations prior to Ltx and lymphocyte subsets were post-operatively in the normal range. There was no extensive loss of protein by ascites. IGIV were replaced in the three patients monthly without further complications. In two of the patients (1 and 3) IVIG therapy was discontinued 8 and 10 months after Ltx when the immunosuppression has been reduced and serum IgG concentrations were found in the normal range without further immunoglobulin replacement. Severe hypogammaglobulinemia is a rare phenomenon following pediatric LTx and seems to be mainly caused by immunosuppressive drugs, however, the exact underlying mechanisms are unclear. A screening for hypogammaglobulinemia is useful after pediatric LTx, especially in patients with an intensified immunosuppression. Moreover, further immunologic research in affected patients is necessary.     

Assessing allocation of responsibility for health management in pediatric liver transplant recipients

Given the increased risk for non‐adherence and poor health outcomes in late adolescence, there is a need for better methods to evaluate and improve the transition process as adolescent patients are prepared to be independent adults. This study assessed the psychometrics and concurrent validity of a newly developed measure of AoR for health management in pediatric liver transplant patients. A total of 48 patients and 37 parents completed a 13‐item measure of AoR. We performed an exploratory PCA on survey results and used component scores to assess the relationship between AoR and age, age at transplant, adherence, and health outcomes. Two primary components were identified: communication with the healthcare system and self‐management tasks. Parent perception of adolescent responsibility for tasks related to communicating with the healthcare system was correlated, in younger patients, with increased non‐adherence while responsibility for tasks related to self‐management was correlated, in older patients, with decreased non‐adherence. These results support AoR as a two‐domain construct, and they provide targets for monitoring and intervention as adolescent patients advance toward transfer.     

The use of transient elastography and non‐invasive serum markers of fibrosis in pediatric liver transplant recipients

The use of non‐invasive markers to diagnose liver allograft fibrosis is not well established in children after LTx. TE, FT, and ELF score were performed in 117 liver‐transplanted children (60M, 8.9 [0.5–18.5] yr) and 336 healthy controls. Liver biopsy was available in 36 children. Results of histology and non‐invasive markers were compared using correlation coefficient or Mann–Whitney U‐test as appropriate. TE correlated best with histological degree of fibrosis (r = 0.85 vs. r = 0.04 [FT] or r = ?0.38 [ELF]). Liver stiffness values for transplanted children without fibrosis were significantly higher than those of healthy controls (7.55 [5.4–20.4] kPa vs. 4.5 [2.5–8.9] kPa). Presence of rejection was a potent confounder for the performance of TE. Both TE and FT reflected clinical changes (acute rejection, cholestasis, increasing fibrosis) in a total of 16 patients who underwent serial measurements. TE correlates better with histological degree of fibrosis in liver‐transplanted children than FT or ELF, but an individual baseline value needs to be determined for each patient. Normal or cutoff values for pathological degrees of fibrosis cannot be transferred from non‐transplanted children. Follow‐up studies, preferably with protocol biopsies, might help to improve the diagnostic quality of TE.     

Neurocognitive outcome in pediatric liver transplant recipients

Studies have shown that children with liver transplants demonstrate deficits on intellectual, academic, and language measures. However, limited information is known about the long-term cognitive development of these children. In this study, 15 children who were at least 2 yr post-liver transplantation (LT) were compared on cognitive measures to an equated group of 15 children with cystic fibrosis (CF). Children with CF were selected as a clinical control given similarities in disease onset and chronicity, as well as physical growth and development. Results indicated that children with LT tended to have lower verbal intelligence quotient scores and performed significantly lower than CF children on language measures, particularly on receptive language tasks. No significant differences were obtained on measures of academic achievement or visual-spatial performance. In the LT group, days in the intensive care unit, total number of days spent in the hospital during the first year following the transplant, and elevated pretransplant bilirubin levels significantly predicted the speech and language delays.     

Towards minimizing immunosuppression in pediatric liver transplant recipients

Abstract:  Immunosuppression regimens after liver transplantation focus mainly on preventing rejection and subsequent graft loss. However, in children, morbidity and mortality rates from infections exceed those from rejection after transplant, and immunosuppression can hinder growth, renal function, and graft tolerance. We hypothesized that early steroid withdrawal, with a primary aim of TAC monotherapy would yield no penalty in terms of rejection and graft loss, while reducing risks of infection and maximizing growth. We prospectively evaluated 64 consecutive pediatric liver transplant recipients. One yr patient/graft survival was 93/90%, respectively. At one yr post-transplant, 75.4% of patients were on TAC monotherapy. No deaths or graft losses were caused by infection. Sixty-one percent of patients had at least one episode of rejection, most within three months following transplant and 3.8% were treated for chronic rejection. One non-compliant adolescent died from chronic rejection. CMV, EBV, and lymphoproliferative disease rates were 3.1%, 5.3%, 1.8%, respectively. Pretransplant and one yr post-transplant glomerular filtration rates were unchanged. One yr improved catch-up growth was observed. We conclude that immunosuppression minimization after pediatric liver transplant yields no serious complications from rejection, and might confer advantages with respect to infection, renal function, growth, and is deserving of wider application and study.     

Analysis of clinical variables associated with tolerance in pediatric liver transplant recipients

Tolerance has been defined as stable graft function off IMS. We reviewed the data of 369 pediatric liver transplant patients to examine demographic differences that may have a PV of pediatric LT tolerance. Of the 369 patients, 280 patients were stable with detectable blood levels of IMS agents and with good graft function without biopsy proven REJ > 1 yr posttransplantation, 18 patients were noted to be TOL off IMS, 27 patients were taking MIS with drug levels below detectable range by standard laboratory parameters, and 44 patients developed one or more episodes of biopsy proven acute or chronic REJ > 1 yr post-transplantation. Variables, including percentage of biliary atresia, type of transplanted organ, history of EBV infection, patient and donor gender, and ABO blood type mismatch between recipient and donor did not have PV of tolerance. Average age in years was 1.37 ± 1.53 (0.3-4.9) for TOL, 1.14 ± 0.89 (0.4-3.1) for MIS and 3.35 ± 4.45 (0.3-16) for REJ. Age difference of TOL/MIS vs. REJ was significant (p =0.002) and TOL vs. REJ was significant (0.01). Age at the time of transplantation is an important predictor in the development of pediatric LT tolerance.     

Transient elastography assessment of liver allograft fibrosis in pediatric transplant recipients

TE measures liver stiffness to assess fibrosis. Its use in post‐transplant patients was reported in few small pediatric studies. We evaluated TE ability to predict liver graft fibrosis in a large cohort while comparing it to the performance of APRI and FIB‐4. We also investigated the effect of graft type on LSMs. Patients at Boston Children's Hospital who underwent LT and LSM ≤ 1 year from biopsy (2007‐2018) were eligible. Ninety‐four patients (45%M) aged 1‐21 years (89% < 18 years; 13% < 2 years) were eligible. Median time between transplant/biopsy and LSM was 5.1 years and 52 days, respectively. Thirty‐nine percent received whole‐liver grafts, 54% TV grafts, and 6% as part of MV. At LSM, median ALT was 25 [IQR 16‐33] IU/L. Twenty‐one percent had METAVIR ≥ F2. LSM was statistically higher among those with significant fibrosis (METAVIR ≥ F2) compared to those with METAVIR F0/F1 (median [IQR] 7.5 [4.6, 13.6] vs 5.1 [4.0, 6.4] kPa, respectively) (P = .005 by Wilcoxon rank‐sum test). APRI and FIB‐4 distributions were not different across METAVIR stages. The AUROC for LSM was 0.71 (95% CI 0.56‐0.85) with an optimal cut‐point of 6.5 kPa. Graft type had no influence on the AUROC for LSM. TE is useful for assessing significant graft fibrosis in children and young adult LT recipients and performs better than APRI and FIB‐4. TV grafts demonstrate similar correlation with histology as whole‐liver grafts.     

第3代小儿死亡危险评分和小儿危重病例评分的应用

第3代小儿死亡危险评分(pediatric risk of mortalityⅢ,PRISMⅢscore)和小儿危重病例评分(pediatric critical illnessscore,PCIS)均为生理学危重评分法。前者发表于1996年,由原PRISM评分发展而来,有17个生理参数,26个生理参数范围,是世界上应用最广泛的儿科评估病情和预后的工具。后者公布于1995年,有10项生理指标,其简便、有效、适合国情,是国内应用最广泛、有效的儿科危重评分法。二者均经过大规模临床应用验证。除评估病情和预后,还可评估ICU工作质量和效益,对比不同ICU患者状况、资源利用和管理,进行危重症临床研究。本研究对PRISMⅢ的应用及其与PCIS的进行对比研究。     

Psychosocial functioning of pediatric renal and liver transplant recipients

Abstract:  The current study examined child- and parent-reported child psychosocial functioning in a large sample of children who received solid organ transplantation. Participants included 64 children who received kidney or liver transplantation and 64 parents who completed a standardized measure of children's psychosocial functioning (BASC; Reynolds & Kamphaus, 1992). Although post-transplant children reported significantly fewer psychosocial difficulties than the normative average, parents reported that children had some psychosocial difficulties, particularly internalizing problems. There were no differences in psychosocial functioning between deceased donor organ and living donor organ recipients. Given the discrepancy between parent and child report, the results suggest that children may underreport psychosocial difficulties following transplantation or parents may over-report children's difficulties. Clinicians and researchers are encouraged to obtain assessment information from multiple reporters when assessing psychosocial functioning in this population.     

Renal function outcome in pediatric liver transplant recipients

The orthotopic liver transplantation (OLT) allows survival of children followed for severe hepatic injury, provided that the immunosuppressive treatment is prolonged. The nephrotoxicity of cyclosporine predicts the long-term outcome of the adult patients receiving a liver transplant. The aim of this study was to determine the long-term outcome of renal function in children receiving OLT. This study included 12 children, with a median for age of 7.1 yr (2-15 yr) at the time of OLT. The duration of follow-up was at least 4 yr, being 7 yr in 10 patients and more than 10 yr in seven. Renal function was evaluated with the serum level of creatinine, calculated glomerular filtration rate (cGFR), and measurement of glomerular filtration rate using chrome 51 ethylenediaminetetraacetate ((51)Cr EDTA) clearance performed at least once during follow-up. The doses and the serum concentrations (C(0)) of cyclosporine were reported at each study time. The cGFR decreased significantly 2 yr after the OLT [median (range): 106 mL/min/1.73 m(2) (71-150) at the time of OLT vs. 85 mL/min/1.73 m(2) (57-128) 2 yr after the OLT, p = 0.03], and decreased again between 7 and 10 yr after OLT [median (range): 99 mL/min/1.73 m(2) (76-125) 7 yr after OLT vs. 81 mL/min/1.73 m(2) (66-140) 10 yr after OLT, p = 0.04]. Six patients developed chronic renal failure (cGFR from 57 to 80 mL/min/1.73 m(2)) 2 yr after OLT associated with high doses of cyclosporine [median (range): 8.8 mg/kg/day (3.5-13)]. The cGFR overestimated renal function by 16% compared with the isotopic measurement of GFR (p = 0.03). Using the (51)Cr EDTA measurement, six of seven patients followed up more than 10 yr after OLT presented mild (n = 3) or moderate (n = 3) chronic renal failure. In our study, the majority of OLT recipients developed a chronic renal failure 10 yr after transplantation. Cyclosporine seems to be the most important factor responsible for the impairment of renal function. The use of the mycophenolate mofetil, a new immunosuppressive agent, allowing a reduction in the dose of cyclosporine, could minimize renal dysfunction. While awaiting the results of a prospective long-term study, close drug monitoring is advised.     

Simultaneous or sequential gastrectomy in pediatric liver transplant recipients

The association between LT and gastrectomy is not common. Only two studies reported the gastrectomy/LT association in children. Here, we report three children who underwent LT who required a concomitant or sequential gastrectomy for different reasons. Patient 1, a 16‐yr‐old boy, during the LT, underwent a partial gastrectomy due to extensive injury to the duodenum. He had a previous and unusual portoenterostomy performed in the duodenum. Bowel reconstruction was performed using an intestinal loop that was first used for the bilio‐enteric anastomosis and then connected to the gastric stump. Patient 2, a 22‐month‐old female child, underwent a partial gastrectomy with a Roux‐en‐Y reconstruction during a retransplantation. She had a large perforated gastric ulcer blocked by the allograft liver. Patient 3, a 26‐month‐old male child, five yr after living donor LT, was submitted to a partial gastrectomy because of gastric outlet obstruction. The histopathology was compatible with eosinophilic gastritis. The association between LT and gastrectomy in the pediatric population is extremely rare. Appropriate knowledge of the previous transplantation technique is very important. Further studies are required to assess the outcomes of the different types of gastric reconstruction in pediatric recipients.     

Supra‐therapeutic tacrolimus concentrations associated with concomitant nicardipine in pediatric liver transplant recipients

Tacrolimus is prescribed to prevent allograft rejection in pediatric liver transplant recipients; however, its metabolism through the cytochrome P‐450 enzyme system presents a multitude of challenges in regard to drug interactions. Here, we describe four children (ages 1.4–8.7 yr) who acutely developed supra‐therapeutic serum tacrolimus trough concentrations, despite standard dosing, while on concomitant nicardipine therapy following liver transplantation. Even though tacrolimus regimens were altered (dosage reductions and held doses), serum tacrolimus concentrations remained elevated. Resolution of high tacrolimus concentrations was achieved only after the discontinuation of nicardipine. Following the termination of nicardipine, all children eventually required dosage increases in their tacrolimus regimens to re‐achieve target serum concentrations. We conclude that concomitant use of tacrolimus and nicardipine can result in high tacrolimus concentrations due to the inhibition of cytochrome p450 enzymes responsible for the metabolism of tacrolimus. We encourage clinicians to consider alternative antihypertensive options in children on tacrolimus therapy. If nicardipine therapy is necessary, we recommend a 50% reduction in tacrolimus dose and daily serum concentration monitoring.     

Liver allograft pathology in healthy pediatric liver transplant recipients

Liver transplantation offers excellent results for children with end‐stage liver disease, and efforts should be directed toward maintaining long‐term graft health. We evaluate graft pathology in healthy pediatric transplant recipients with low‐maintenance immunosuppressive medications to assess whether protocol biopsies are helpful for adapting immunosuppression and protecting long‐term graft function. Liver biopsies were performed on 60 healthy pediatric liver transplant recipients, and histological findings were correlated with laboratory, serological, and radiological results. Fourteen patients (23%) were diagnosed with acute or early chronic rejection, and immunosuppressive medications were increased in these children. Liver function tests did not correlate with histological findings. The incidence of fibrosis was 36% in transplant recipients five or more years after liver transplantation. We observed an unexpectedly high prevalence of rejection and fibrosis in children with no laboratory abnormalities, which led to changes in their immunosuppressive medications. Scheduled biopsies appear to be useful in pediatric transplant recipients with low immunosuppressive medications for early detection of morphological changes in liver transplants. Further studies are needed to evaluate whether adaption of immunosuppression helps to reduce tissue damage and the incidence of allograft dysfunction in the long term.     

Oral health of pediatric liver transplant recipients

To evaluate oral health conditions in pediatric liver transplant recipients, with special focus on caries, green staining of the teeth, gingival bleeding, and gingival overgrowth. 40 patients (mean age 11.6 years) were examined at a routine follow‐up visit, 6 months to 16 years after liver transplantation at the Swiss Center for Liver Disease in Children. After the medical examination, participants were further examined for the presence of dental caries, periodontal disease, GE, and GTC. The mean decay, missing, and filled teeth (dmft/DMFT) score was 3.8. 45% of the participants presented at least one carious lesion. Two‐third of the participants had more than 20% of sites with the presence of plaque and gingival inflammation. Signs of GE were found in 18% and GTC in 30% of the participants. A positive correlation was identified between GTC and peak serum bilirubin (P<.001) and primary diagnosis of cholestatic disease (P=.04). Gingival inflammation was associated with plaque (P<.001), use of immunosuppressive medication (P=.04), and was more pronounced in children with cholestatic disease (P=.007). Children and young adults with liver transplants presented a rather poor oral health status. Liver transplant physicians should counsel patients for regular dental follow‐up in order to avoid serious dental infections.     

Immediate tracheal extubation of pediatric liver transplant recipients in the operating room

Keeping patients on mechanical ventilation after orthotopic liver transplantation (OLT) has been a standard anesthetic approach since the first utilization of liver transplantation. Advances in anesthetic management, surgical techniques and patient preparation, in addition to improved postoperative care and the reported advantages of early postoperative tracheal extubation of liver recipients. encouraged us to extubate most recipients at the end of the operation. The aim of the present study is to evaluate the pediatric liver recipients who were extubated immediately at the end of transplantation, in terms of respiratory complications and allograft function during their stay in the ICU. We retrospectively reviewed the records of 40 pediatric recipients who had undergone OLT at the Ege University Organ Transplantation Center between December 1997 and July 2002. Twelve out of 40 patients who had consecutively undergone OLT were extubated immediately at the end of the operation and were included this study. Mean Child Pugh scores of the patients were 9 +/- 2.3 (range 6-12) and the mean PELD score was 23.1 +/- 12.3 (range 7-41). The mean age of the patients was 8.4 +/- 5.2 (range 0.8-16.8 yr). Five of the 12 extubated patients received a cadaveric and seven a living donor liver graft. The mean ICU stay of the patients was 49.1 +/- 24.2 h (6-120 h). No patients required reintubation or mechanical ventilation in the ICU. Respiratory complications diagnosed in the 12 extubated patients were hypercapnia without hypoxemia in three, atelectasis in one and pleural effusion in two. No primary non-function or delayed graft function was detected. The aspartate transaminase (AST), alanine transaminase (ALT) and protrombin time (PT) were normalized within a week. We believe that immediate tracheal extubation in the operating room is a safe procedure for selected cadaveric and living-related liver transplant recipients and will facilitate the patients' recovery and mobilization leading to reduction in complications and a reduced ICU stay.     

Invasive candidiasis in liver transplant patients: Incidence and risk factors in a pediatric cohort

Prolonged OR, re‐transplantation, and high‐volume intraoperative transfusion have been associated with increased risk for IC in adult LT recipients. Antifungal prophylaxis is recommended for adult patients with these risk factors. There are limited data on the incidence of and risk factors for IC in pediatric LT recipients. A retrospective cohort study of all pediatric LT patients at the CHOP between 2000 and 2012 and the CHP between 2004 and 2012 was performed to define the incidence of IC within 30 days of LT. A 3:1 matched case–control study with incidence density sampling was performed. Conditional logistic regression analyses were used to explore risk factors associated with IC. Among 397 recipients, the incidence of IC was 2.5%. Bivariate analyses showed that ICU admission prior to transplant, OR > 10 h, intraoperative volume infusion of >300 mL/kg, and broad‐spectrum antibiotics were significantly associated with IC. In a multivariate model, only ICU admission remained significantly associated with IC. Antifungal prophylaxis was not significantly protective against IC. The low incidence of IC and lack of an identified protective effect from antifungal prophylaxis suggest that prophylaxis in pediatric LT recipients should not be routinely recommended to prevent IC events in the first 30 days post‐transplant.     

Evaluating non-adherence to immunosuppressant medications in pediatric liver transplant recipients

Abstract:  Non-adherence with recommended immunosuppressant medications is common post-pediatric liver transplant and is the most important reason for organ rejection in long-term survivors. However, there is currently no validated, standard method to measure adherence, with a well-defined threshold, making it extremely difficult to evaluate interventions to improve adherence. Previous studies have suggested that the degree of fluctuation of medication blood levels over time can provide an idea about how regularly the medication is being taken. The present study, conducted at UCLA medical center, sought to identify a specific threshold value of the s.d. of individual tacrolimus blood levels in pediatric liver transplant recipients which would be associated with rejection episodes in these patients. A threshold of 3.0 has been identified in other studies, and was supported by the analysis of retrospective data from 96 subjects. However, further analysis found that a s.d. of 2.5 appeared to have a better fit with the data. These findings suggest the utility of monitoring the s.d. of routine tacrolimus blood levels in pediatric liver transplant recipients for detecting non-adherence to immunosuppressant medication prior to clinical rejection, allowing earlier interventions.