A service evaluation comparing CVVH an CVVHD in minimising circuit failure

A significant problem during continuous renal replacement therapy is premature circuit failure, affecting efficacy and molecular clearance. Techniques to improve circuit failure are anticoagulation, access site and modality. A modality change was introduced, moving from continuous veno-venous haemofiltration to continuous veno-venous haemodiafiltration as a result of existing issues with failing circuit times and failure rates.

The aim of this service evaluation was to ascertain if the use of continuous veno-venous haemodiafiltration compared to continuous veno-venous haemofiltration had affected failed circuit survival times and rates.

A service evaluation was chosen because the focus was to ascertain what effect a practice change had had on a particular service. The service evaluation was registered with the local trust's audit department and gained university ethical approval. It was anticipated that the data generated would be used to inform, question and improve practices. Patients who received renal replacement therapy (RRT) from May 2012 to January 2013 were retrospectively identified. Patients received continuous veno-venous haemofiltration for the duration of their treatment before September 2012 and continuous veno-venous haemodiafiltration after. A total of 78 patients were identified as receiving RRT; 41 of these patients had failed circuits.

A total of 182 failed circuits were analysed. The median duration of failed circuits during continuous veno-venous haemofiltration was shorter (2·75 h, standard deviation (SD) = 13·82) when compared to continuous veno-venous haemodiafiltration (11 h, SD = 15·26, p < 0·001, 95% confidence interval (CI) 2·5-10). Circuit failure rate in continuous veno-venous haemofiltration was 56% compared to 43% in continuous veno-venous haemodiafiltration. After performing a Cox regression analysis, continuous veno-venous haemofiltration appeared to have a 1·87 times (CI 1·18-2·82, p > 0·007) more likely chance of failure.

The use of continuous veno-venous haemodiafiltration has had an overall positive effect on the haemofiltration service by reducing the number of failed circuits and increasing circuit survival times, which may have improved the efficacy of the service. Continuous veno-venous haemodiafiltration may be a more appropriate modality of choice in non-septic patients requiring prolonged continuous RRT episodes.