Possible strategies to prolong circuit life during hemofiltration: three controlled studies

The prevention of filter clotting is an important goal in the management of continuous renal replacement therapy (CRRT). Anticoagulation is the mainstay of such prevention. However, other strategies might prolong filter life without increasing the risk of bleeding. We tested the effectiveness of three strategies (use of flat plate configuration, heparin administration into the air chamber and use of a larger membrane surface) aimed at prolonging circuit life without increasing the dose of anticoagulation.

Thirty-one critically ill patients with acute renal failure (ARF) managed with continuous venovenous hemofiltration (CVVH) were studied. Filters were randomized in a crossover design to three consecutive studies: (1) filtration with either hollow-fiber or flat-plate hemofilters, (2) administration of heparin dose pre-filter or divided into pre-filter and directly into the bubble trap chamber and (3) use of two different surface areas with Filtral 8 (surface area 0.75 m2) vs. Filtral 12 (surface area 1.30 m2) hemofilters.

Mean circuit life for flat-plate and hollow-fiber hemofilters (cohort 1) was 14.7 +/- 4.7 h and 17.1 +/- 2.8h respectively (NS). Mean circuit life for single heparin administration site vs. double site administration (cohort 2) was 17 +/- 3.2 h and 18 +/- 3.1 h respectively (NS). Mean circuit lifespan for 0.75 m2 and 1.30 m2 hemofilters was 16 +/- 12.2 h and 15.7 +/- 14.3 h respectively (NS) (cohort 3). Visible clot formation in the bubble trap chamber was a frequent cause of circuit failure.

Neither flat plate membrane configuration nor increasing membrane surface area, nor heparin administration in the air chamber prolong circuit life during CWH. The bubble trap chamber is a frequent site of circuit clotting.