A haemodialysis system for the treatment of acute renal failure and metabolic disorders in neonates

A prototype dialysis system for the treatment of premature babies has been designed, built and successfully tested. It can be used to treat babies who are suffering from renal failure or metabolic disorders. These patients are difficult or impossible to treat conventionally, due to their very small total blood volume (typically 40 ml) and their intolerance to donated blood. There was a strong case for developing a dialysis system specifically designed for the treatment of such patients.The system is based on a manually operated device that had been previously developed. The method differs from conventional dialysis in several ways. Blood access to the patient is via a single venous catheter. Only a very small amount of blood is needed to prime the extracorporeal circuit—this can be as little as 6.8 ml in the smallest patients. This compares very favourably with the volumes needed in conventional circuits, which are in the range of 15–40 ml. This small priming volume means that donated blood is not needed to prime the circuit, which reduces the risks and complexity of the treatment. The clearance and ultrafiltration rates that can be achieved are independent of the rate that blood can be accessed from the patient, since the same blood passes back and forth through the dialyser several times.In vitro testing covered several areas of operation. The accuracy of the ultrafiltration process was established. The clearance rates that could be achieved were determined. The clearances that have been obtained experimentally with the new system are consistently above 40% of the mean blood flow rate through the system. The largest mean blood flow rate available is 5 ml/min, so the maximum clearance is approximately 2 ml/min. The maximum ultrafiltration rate that can be obtained is 50 ml/h. The amount of damage caused to the blood by the system was found to be well within acceptable clinical limits. In vivo testing established the feasibility of using a computer algorithm to control the withdrawal of blood from the patient. The system has been used successfully to treat seven patients at the time of publication.