Comparison of haemodialysis and peritoneal dialysis in babies

INTERVENTION: Babies weighing up to 8 kg that need dialysis for acute renal failure and who would normally be treated with peritoneal dialysis (PD), will be studied for 4 days. During that time they will have 2 days of PD, and 2 days of haemodialysis (HD) with a new infant haemodialysis machine. The different treatments will be given on alternate days, and the starting modality will be randomised. Comparisons will be made within patients ? a crossover design. The only extra interventions they will undergo will be a total of 4ml blood being drawn at times that blood was being sampled for clinical reasons (to test for plasma haemoglobin concentrations), and chemical analysis of waste dialysis fluid to allow clearances to be measured. CONDITION: Acute kidney failure in babies weighing <8 kg ; Urological and Genital Diseases ; Congenital renal failure PRIMARY OUTCOME: Our primary question is whether the Newcastle HD machine will provide better clearance of the kidney marker creatinine than PD does in small babies. Creatinine clearance will be measured twice daily throughout the 4 days of the study by comparing the creatinine concentrations measured in blood samples taken for clinical reasons with the concentrations in waste dialysis fluid taken at the same time.; ; The log10 geometric mean of the clearances on HD will be subtracted from the equivalent values on PD, producing a ratio of HD/PD clearances. SECONDARY OUTCOME: 1. Whether the Newcastle HD machine will provide better clearance of the waste chemicals urea and phosphate than PD does in small babies. These clearances will be measured in parallel to the creatinine clearances. ; 2. Whether the Newcastle HD machine will provide greater and more precise control of fluid removal than PD does in small babies. This will be measured by comparing how closely the volumes removed each day compare to the prescribed clinical target.; 3. Whether the Newcastle HD machine will be equally safe, and that it will be less time consuming and more convenient for the nursing staff to operate than PD. These will be assessed by recording all possible adverse events, and by a questionnaire to the medical and nursing staff on convenience of use and user preference. INCLUSION CRITERIA: 1. Being treated in Freeman Hospital Paediatric Intensive Care Unit 2. Weighing =8 kg 3. Being judged by the consultants in the clinical teams responsible for their care to require either dialysis or ultrafiltration, or both. This decision may be made on biochemical or other pathophysiological criteria, which will be documented.