Pharmacokinetics of oral valganciclovir solution and intravenous ganciclovir in pediatric renal and liver transplant recipients.

In an open-label, prospective, pharmacokinetic assessment, we evaluated total drug exposure (area under the curve [AUC]) of intravenous (IV) ganciclovir (GCV) and oral (p.o.) valganciclovir when normalized for body surface area (BSA) in pediatric liver (n=20) and renal (n=26) transplant patients Reference doses for IV GCV (200 mg/m(2)) and p.o. valganciclovir (520 mg/m(2)) were based on adult doses, and adjusted for BSA initially, and BSA and renal function (estimated via creatinine clearance [CrCL]) thereafter. Renal transplant patients received GCV on days 1-2, valganciclovir 260 mg/m(2) on day 3, and valganciclovir 520 mg/m(2) on day 4. Liver transplant patients received twice daily GCV from enrollment to day 12, and then valganciclovir twice daily on days 13-14. GCV pharmacokinetics were described using a population pharmacokinetic approach. Type of solid organ transplant (kidney or liver) had no effect on GCV pharmacokinetics. Median GCV exposure following valganciclovir 520 mg/m(2) was similar to that with IV GCV, and to that reported in adults. Patients <5 years of age had AUC values approximately 50% of those compared with older age ranges; dosing based on both BSA and CrCL increased drug exposure in younger patients. A dosing algorithm based on BSA and CrCL should be tested in future studies.

UGT genotype may contribute to adverse events following medication with mycophenolate mofetil in pediatric kidney transplant recipients.

Leukopenia and diarrhea are the predominant adverse events associated with mycophenolate mofetil (MMF), leading to dose reduction or discontinuation in children. Polymorphisms of the drug's main metabolizing enzyme, uridine diphosphate-glucuronosyl transferase (UGT), confer alteration in drug exposure. We studied the incidence of these polymorphisms in pediatric kidney transplant recipients experiencing MMF-associated leukopenia and diarrhea. UGT genotypes of 16 affected children who recovered after MMF dose reduction or discontinuation were compared with those of 22 children who tolerated the drug at standard doses. DNA was extracted and sequenced using standard procedures to detect polymorphisms associated with increased (e.g., UGT1A9 -331T>C) or decreased drug exposure. All three patients who were homozygous for UGT1A9 -331T>C developed leukopenia, and heterozygotes also had significantly more toxicity (P = 0.04). A weaker association (P = 0.08) existed in UGT2B7 -900G>A carriers. Our data implicate UGT polymorphisms associated with altered drug exposure as potential predictors of MMF adverse events.

Clustering of post-diarrheal (Shiga toxin-mediated) hemolytic uremic syndrome in families.

AIMS: 1. To study the epidemiological and clinical features of Shiga toxin (Stx)-mediated (post-diarrheal) hemolytic uremic syndrome (HUS) occurring in more than 1 family member. 2. To compare familial with non-familial episodes, and concurrent familial with non-concurrent familial cases. 3. To determine the likelihood of Stx HUS occurring in a second family member. METHODS: A retrospective review from January 1970 through September 2001 of families in whom Stx HUS occurred in more than 1 family member was conducted using a computerized HUS registry. It contains information on 373 episodes that occurred in 356 families from Utah and neighboring states. Cases were categorized as being either concurrent (i.e., occurring within a month of one another) or non-concurrent, and the study was limited to those with typical (post-diarrheal) episodes. RESULTS: HUS occurred in 2 or more family members in 17 (4.8%) of the families in our registry. In 12 (3.4%) of these families episodes occurred with days to weeks of each other; in 5 families (1.4%) episodes were separated by intervals of several years. There were no statistically significant differences in demographic, seasonal, laboratory, clinical, or outcome variables between familial subsets (concurrent versus non-concurrent) or between familial and non-familial cases. CONCLUSIONS: When a child is diagnosed with D+ HUS, there is an increased risk that a second family member will also develop HUS; most often within days to weeks (i.e., within a month), but in some cases episodes may be separated by intervals of years. Non-concurrent cases suggest common environmental risk factors, or perhaps a genetic predisposition. Concurrent cases suggest a common source of infection or person-to-person transmission; a genetic predisposition cannot be excluded. These observations suggest that siblings of an index case who develop diarrhea should be kept under close surveillance.

Indications, results, and complications of tacrolimus conversion in pediatric renal transplantation.

It is the practice of many pediatric renal transplant programs to 'convert' children taking cyclosporin A (CsA) to tacrolimus, although the indications for, outcome, and complications of this practice remain obscure. To better understand these aspects of tacrolimus 'conversion', a fax survey was sent to 119 North American pediatric renal transplant centers. Analyzable responses were received from 52 centers (44%), and included data from approximately 1,815 pediatric renal transplants performed between 1991 and 98. Strong indications for tacrolimus conversion were: antibody-resistant rejection, CsA-resistant rejection, and CsA intolerance (strong indication in 72%, 65%, and 52% of centers, respectively). Steroid-resistant rejection and cosmetic side-effects were considered strong indications less often. Initial anti-rejection therapy was usually increased corticosteroid dose (47/52 centers). Antibody therapy was most commonly used for steroid-resistant rejection (44 centers). For steroid- and antibody-resistant rejection, tacrolimus conversion was most common (33 centers). Tacrolimus conversion for antibody-resistant rejection led to improvement of serum creatinine (SCr) in 27% of patients, stabilization of SCr in 46%, worsening of SCr in 11%, and graft loss in 16%. Reported complications after tacrolimus conversion included hyperglycemia, hyperkalemia, lymphoproliferative disorder, infection, and neurologic problems. We conclude that the major indication for tacrolimus conversion in pediatric transplant programs appears to be rejection. Outcome after tacrolimus conversion appears good, with the majority of patients experiencing stable or improved allograft function. These data provide direction for further study, including timing of tacrolimus conversion and interaction with other therapies.

Hemolytic uremic syndrome associated with Denys-Drash syndrome.

The Denys-Drash syndrome is defined by the occurrence of combinations of pseudohermaphroditism, nephrotic syndrome with diffuse mesangial sclerosis, Wilms' tumor, and constitutional mutations in the WT1 suppressor gene. Most patients develop end-stage renal failure. Atypical hemolytic uremic syndrome (HUS) is defined by onset of acute hemolytic anemia with fragmented erythrocytes, thrombocytopenia, and renal failure in the absence of a gastrointestinal prodromal illness of bloody diarrhea. The purpose of this report is to describe the occurrence of features of atypical HUS and Denys-Drash syndrome in two African-American boys aged 13 and 16 months. Each had nephrotic syndrome, diffuse mesangial sclerosis, and WT1 point mutations. Both had grade III hypospadias and undescended testes. They had normal serum creatinine concentrations and hematology a month before presenting with HUS. Stool cultures for Escherichia coli O157:H7 were negative. Each patient has been transplanted with cadaver kidneys without recurrence of HUS.

Determinants of survival in pediatric continuous hemofiltration.

Continuous hemofiltration (CH) is being used in increasing numbers of pediatric intensive care unit patients. Experience with 114 CH treatments in 98 critically ill children from March 1988 to March 1993 is presented in this study. Ages ranged from 1 day to 23 yr (mean +/- SE = 7.1 +/- 0.7 yr), and 54% of patients were male. Seventeen percent of all treatments were performed in neonates under 1 month of age. The most common primary diagnoses were sepsis and adult respiratory distress syndrome (11 patients each), liver transplantation and hypoplastic left heart syndrome (10 patients each), and hemolytic uremic syndrome (9 patients). The most frequent indications for CH were fluid overload and acute renal failure (42% each). Choices for CH included: continuous arteriovenous hemofiltration (CAVH, 50%), continuous arteriovenous hemodiafiltration (CAVH, 23%), continuous venovenous hemofiltration (CVVH, 18%), and continuous venovenous hemodiafiltration (CVVH-D, 9%). Choices for anticoagulation included: none (47%), regional (49%), and systemic (4%). Treatment duration ranged from 1 to 25 days (mean = 5.3 +/- 0.4 days). Mean filter life span for 363 filters was 0.94 +/- 0.1 filters/patient per day. Despite an overall survival rate of 43%, survival to discharge varied greatly (0 to 100%) among the 24 diagnostic groups: tumor lysis syndrome and systemic lupus erythematosus (3/3 patients each, 100%), hemolytic uremic syndrome (8/9 patients, 89%). This compares with: bone marrow transplantation (0/6 patients, 0%), hypoplastic left heart syndrome (2/10 patients, 20%), and leukemia (1/4 patients, 25%). Survival to hospital discharge was better in patients who did not receive pressors (P < 0.005) and in patients treated with combined ultrafiltration and dialysis (CAVH-D, CVVH-D) compared with ultrafiltration alone (CAVH, CVVH) (P < 0.005), but was not notably affected by patient age, sex, use of anticoagulation, filter life span, blood pump-assisted versus spontaneous CH, or duration of therapy. Filter life span was not affected by use of anticoagulation, but was remarkably longer in patients with arteriovenous versus venovenous CH (P < 0.004). It was concluded that: (1) empirical anticoagulation of patients treated with CH is not necessary; (2) children with a minority of underlying diseases and those requiring pressor support at initiation of CH appear to have relatively poor survival rates despite the technically effective use of CH; and (3) the addition of countercurrent dialysis to routine CH may enhance patient survival to hospital discharge.

Inhibition of calcium oxalate crystal growth in vitro by uropontin: another member of the aspartic acid-rich protein superfamily.

The majority of human urinary stones are primarily composed of calcium salts. Although normal urine is frequently supersaturated with respect to calcium oxalate, most humans do not form stones. Inhibitors are among the multiple factors that may influence the complex process of urinary stone formation. We have isolated an inhibitor of calcium oxalate crystal growth from human urine by monoclonal antibody immunoaffinity chromatography. The N-terminal amino acid sequence and acidic amino acid content of this aspartic acid-rich protein, uropontin, are similar to those of other pontin proteins from bone, plasma, breast milk, and cells. The inhibitory effect of uropontin on calcium oxalate crystal growth in vitro supports the concept that pontins may have a regulatory role. This function would be analogous to that of other members of the aspartic acid-rich protein superfamily, which stereospecifically regulate the mineralization fronts of calcium-containing crystals.

Management of urinary tract infections in children.

Urinary tract infection is common in children. The presentation varies with age. Younger children exhibit protean signs. Diagnosis is dependent on the demonstration of significant bacteriuria in a properly collected and handled urine sample. The approach to treatment depends on the degree of illness at presentation, the presence of structural urinary tract abnormalities, and the age of the patient. Pathophysiology of urinary tract infection is dependent on interactive factors of the host and of the invading microorganism. Urinary tract abnormalities have significant impact on the management of children with urinary tract infections, both medically and surgically. Of particular importance is the observation that renal damage usually occurs within the first 5 years of life, and treatment delay in some young patients may have significant consequences. The overall prognosis in children with urinary tract infection is favorable.

Continuous arteriovenous hemofiltration/dialysis improves pulmonary gas exchange in children with multiple organ system failure.

Continuous arteriovenous hemofiltration with or without countercurrent dialysis (CAVH[D]) improved pulmonary gas exchange in eight children with concomitant renal and respiratory failure. Fluid accumulation had increased patient weight to 65.2 +/- 18.4 (SD) kg before therapy. After 48 h of CAVH(D), weight was reduced to 60.3 +/- 15.5 kg (p less than .02). Similarly, PaO2/FIO2 improved from 137 +/- 99 to 207 +/- 83 (p = .009) with PEEP unchanged or decreased. In patients with net negative fluid balance, pulmonary artery wedge pressure decreased (from 21.3 +/- 3.8 to 14.8 +/- 5.4 mm Hg; p less than .05). Colloid osmotic pressure increased (15.2 +/- 4.6 vs. 21.4 +/- 4.7 mm Hg; p less than .001). BUN and serum creatinine were unchanged. Parenteral nutrition infused was 212 +/- 427 ml/day before CAVH(D), and 1928 +/- 567 ml/day during its use (p less than .0001). CAVH(D) in children with multiple organ failure allowed better caloric intake, and led to improvement in pulmonary gas exchange. We speculate that CAVH(D) improves pulmonary gas exchange by removal of body and lung water, or by enhancing clearance of mediators associated with pulmonary dysfunction.

Toxic shock syndrome with Staphylococcus aureus exit-site infection in a patient on peritoneal dialysis.

Toxic shock syndrome (TSS) associated with exit-site infection but without peritonitis has not been described. We report a case of TSS with an isolated Staphylococcus aureus exit-site infection in a boy on chronic peritoneal dialysis. The exit site had minimal erythema and no purulence. This report re-emphasizes the fact that mildly appearing cutaneous infections in patients with chronic renal failure may have significant consequences. Particular attention should be given to patients who present with constitutional symptoms that may be of short duration. The importance of culturing all sites in such cases is highlighted. The prevalence of TSS with exit-site infections is unknown, but TSS should be considered in patients presenting with similar features.

Pharmacology of diuretics in the newborn.

Diuretics are used in various conditions with fluid overload. Their efficacy in the management of congestive heart failure is well documented. In contrast, the indication of diuretics in chronic lung disease and central nervous system disorders of the newborn have not been clearly established. Substantial pharmacologic knowledge of diuretics in the young infant remains to be described. Most investigations on diuretics in the sick newborn infant have examined furosemide. In contrast, the pharmaco-dynamics, pharmacokinetics, clinical indications, and toxicity of other diuretics used in the newborn require considerable further evaluation. Future studies using a combination of diuretics, acting at different segments of the nephron, also may provide newer therapeutic modalities to overcome or prevent the development of frequently observed tolerance to diuretics, as well as to treat refractory edema.