Arterial line filtration during cardiopulmonary bypass. Neurologic, neuropsychologic, and hematologic studies

One hundred patients who underwent elective cardiac operations were randomized into two groups. Group 1 had a 20 micron nylon screen filter in the arterial line. In Group 2 no filter was used in the arterial line. Neurologic and neuropsychologic examination of the patients was performed with seven psychometric tests of the Wechsler Memory Scale and the Wechsler Adult Intelligence Scale. These tests were conducted before and a mean of 10 days after the operation. Platelet counts and hemoglobin and total protein levels were measured at the onset and at the end of cardiopulmonary bypass. Two patients died during their hospital stay. Neurologic damage with focal signs was found in the postoperative examination in six patients (three in each group). Twenty-eight patients (28.5%) exhibited signs of mild cerebral dysfunction as assessed by the presence of archaic (primitive) reflexes. Fifteen were in Group 1 and 13 in Group 2 (no significant difference). Sixty patients (61%) had decrements greater than one standard deviation in at least one of the three tests that showed most decreased postoperative scores. There were 32 in Group 1 and 28 in Group 2 (no significant difference). When each test was analyzed individually, there were no significant differences between the two groups. Platelet counts decreased, during cardiopulmonary bypass, a mean of 33% in Group 1 and 34.5% in Group 2 (no significant difference). Both hemoglobin and total protein levels remained virtually unchanged. These results indicate that the addition of a small-pore filter in the arterial line does not prevent the neurologic and neuropsychologic disturbances frequently encountered after cardiopulmonary bypass. The filter itself does not appear to have a direct effect on the blood components. Routine use of an arterial line filter remains questionable.