Management of fluid balance in CRRT: a technical approach

The possibility of making fluid balance errors during continuous renal replacement therapy has been identified since the beginning of this modality of treatment. The advent of automated machines has partially overcome this problem. Nevertheless, there are conditions and operation modes in which the potential for fluid balance errors is still present.

To analyse fluid balance management in CRRT therapies across a range of currently marketed machine.

The tests were conducted in vitro, utilizing saline solution for the blood circuit and regular dialysate/reinfusate for the dialysate/reinfusion circuit. The methodology used was based on the voluntary creation of a fluid balance error by altering the correct flow in the circuit of the different machines. Subsequently, the time for alarm occurrence and the threshold value for fluid balance error was evaluated. The alarm was overridden and the overall fluid error allowed by the machine was evaluated. Each machine was tested in conditions of different dialysate/filtrate flow rates and in different simulated treatment modalities.

Fluid balance errors can be easily avoided not only by a correct and careful adherence to the protocols of use of the current CRRT machines, but also by the compliance to prescriptions and programmed controls during therapy. Most importantly, if an alarm appears on the machine, one can try to override it without major problems; major problems may occur when multiple override commands are operated without identifying the problem and solving it adequately.

Machines seem to be designed with adequate safety features and accurate alarm systems. However, features and alarms can be manipulated by operators creating the opportunity for serious error. Physicians and nurses involved in prescription and delivery of CRRT should have precise protocols and defined procedures in relation to machine alarms to prevent major clinical problems.