Serum S-100 protein concentration after cardiac surgery: a randomized trial of arterial line filtration

Embolization of gaseous and particulate matter is incriminated in the neuropsychological morbidity of CPB and can be reduced by membrane oxygenators and arterial line filtration. It is not known if the use of arterial line filtration in conjunction with membrane oxygenators might have an additive effect in reducing cerebral injury.

Forty patients undergoing elective coronary artery surgery were prospectively randomized to a 43 microns heparin coated arterial line filter (Cobe Sentry) or to no filtration (control group). All operations were performed by one surgeon (DPT) using intermittent ischaemia with nonpulsatile CPB, a COBE CML membrane oxygenator and alpha-stat paCO2 management. Flow rates were maintained between 2.0 and 2.4 l-1 m2 per min with a perfusion pressure of 50-80 mmHg and a systemic temperature of 34 degrees C. Cerebral injury was defined by careful neurological examination and serial measurement of the serum concentration of S-100 protein (a highly specific astroglial cell derivative, elevated serum levels of which correlate with proven cerebral injury).

There was no difference [mean (S.D.)] in the control and filter groups with respect to age [61(9) vs. 62(9) years], ejection fraction, number of grafts [2.8(0.6) vs. 2.6(0.7)] or CPB times [55(19) vs. 57(18) min]. Preoperatively, no patient had detectable S-100. In the postoperative period 23 of 40 patients (58%) showed elevated S-100 levels. At 1, 5 and 24 h the respective number of patients in the control and filter groups with elevated S-100 was (14 vs. 9), (4 vs. 0), (4 vs. 0)) (P < 0.05). No patient had overt cerebral injury.

This study suggests that (i) subclinical cerebral injury is common (58% of patients in this study) even after apparently uncomplicated surgery with short CPB times; (ii) serum S-100 protein is a valuable marker for investigating potentially cerebral protective innovations during CPB; and (iii) arterial line filtration significantly reduces but does not eliminate cerebral injury.