Renal Assist Device

I reviewed a paper in our Renal Journal Club today--Tumlin et al, Efficacy and Safety of Renal Tubule Cell Therapy for Acute Renal Failure in a recent 2008 issue of JASN--which tests a novel device termed the "Renal Tubular Assist Device ", or RAD. It is shown on the left by one of its inventors, Dr. David Humes.

The device consists of a regular CVVH hemofilter which is then hooked up to a separate cartridge containing many thousand microfibers lined with human renal tubular epithelial cells. After filtrate is produced in the CVVH cartridge, a portion (about half) of the filtrate goes into the RAD cartridge, where the filtrate undergoes reabsorption. Blood bathes the extralumenal space of the RAD cartridge so that it can take back the stuff reabsorbed by the tubule cells before it is returned to the body. The idea here is that the RAD should provide a more physiologic means of renal replacement therapy, since instead of just solute removal and volume regulation, additional renal functions (e.g., endocrinologic, tubular reabsorption, ammoniagenesis, etc) are also achieved.

The randomized control trial compared CVVH alone versus CVVH + RAD for a period of up to 72 hours. The published results suggest a mortality benefit in the CVVH + RAD group; however, the p-value of the study was non-significant, and furthermore a follow-up Stage IIb trial failed to show a beneficial (and possibly even showed a detrimental) effect of the RAD. In my opinion, this was an underpowered and thus inconclusive RCT which doesn't give a clear answer to whether or not it is a successful trial, but that the authors are to be commended for their vision in creating a new device for an illness which has a high mortality rate with few therapeutic options.