During membrane plasma fractionation therapy there are reported incidences of membrane plugging requiring the corrective actions of either filter replacement or backwashing (BW) in order to continue the treatment. In this preliminary study, a simple BW procedure to allow for on-line reuse of the filter (Asahi AP06M) during the treatment was evaluated to assess its efficacy and safety in cryofiltration (CF).
Evaluations were carried out on two patients treated for rheumatoid arthritis. Seven tests, each using 1 L or 2 L warmed saline as a BW solution were performed to evaluate the decrease of the transmembrane pressure (TMP) between just before and after backwashing and TMP change during cryofiltration procedures between before and after backwashing. Sieving coefficients of total protein, albumin, immunoglobulins (G, M, A). fibrinogen. and rheumatoid factor were also calculated at 1,000 ml plasma volume processed.
Results showed statistically significant decreases of TMP from 300 mm Hg to 70 mm Hg between just before and after both backwashing procedures, and that there were no significant changes in the TMP increase during the cryofiltration procedure between pre-and post-BW. The protein sievings were not significantly affected by BW. The use of a second liter for rinsing did not reduce the inlet pressure further suggesting that I L BW was adequate. The accumulated solutes did not affect significantly the effective mean pore size. The BW procedure did not affect the overall patient safety during therapy.
In conclusion, this simple BW procedure using 1 L of normal saline and accomplished in approximately 1 1 minutes by a manual procedure proved reliable to rinse the filter and to prolong its clinical use. This procedure obviated the need for filter replacement.