Scanning electron microscopic analysis of arterial line filters used in cardiopulmonary bypass

The clinical value of arterial line filters is still a controversial issue. Proponents of arterial line filtration argue that filters remove particula te matter and undissolved gas from circulation while opponents argue the ab sence of conclusive clinical data. We conducted scanning electron microscop e (SEM) studies of arterial line filters used clinically in the cardiopulmo nary bypass circuits during adult cardiac surgery and analyzed the types an d characteristics of materials entrapped in the arterial line filters. Twel ve arterial line filters were obtained during routine hypothermic cardiopul monary bypass in 12 adult cardiac patients. The arterial line filter was a screen type with a pore size of 40 mum (Baxter Health Care Corporation, Ben tley Division, Irvine, CA, U.S.A.). After opening the housing, the woven po lyester strands were examined with SEM. All segments examined (120 segments , each 2.5 x 2.5 cm) contained no embolic particles larger in their cross-s ectional area than the pore size of the filter (40 mum). The origins of emb olic particulates were mostly from environmental foreign bodies. This may s uggest a possible need for more aggressive filtration of smaller particulat es than is generally carried out at the present time.