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

INTRODUCTION: Embolization of gaseous and particulate matter isincriminated in the neuropsychological morbidity of CPB and can be reducedby membrane oxygenators and arterial line filtration. It is not known ifthe use of arterial line filtration in conjunction with membraneoxygenators might have an additive effect in reducing cerebral injury.METHODS: Forty patients undergoing elective coronary artery surgery wereprospectively randomized to a 43 microns heparin coated arterial linefilter (Cobe Sentry) or to no filtration (control group). All operationswere performed by one surgeon (DPT) using intermittent ischaemia withnonpulsatile CPB, a COBE CML membrane oxygenator and alpha-stat paCO2management. Flow rates were maintained between 2.0 and 2.4 l-1 m2 per minwith a perfusion pressure of 50-80 mmHg and a systemic temperature of 34degrees C. Cerebral injury was defined by careful neurological examinationand serial measurement of the serum concentration of S-100 protein (ahighly specific astroglial cell derivative, elevated serum levels of whichcorrelate with proven cerebral injury). RESULTS: 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 patienthad 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 ofpatients 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 cerebralinjury. CONCLUSIONS: This study suggests that (i) subclinical cerebralinjury is common (58% of patients in this study) even after apparentlyuncomplicated surgery with short CPB times; (ii) serum S-100 protein is avaluable marker for investigating potentially cerebral protectiveinnovations during CPB; and (iii) arterial line filtration significantlyreduces but does not eliminate cerebral injury.