Microemboli from cardiopulmonary bypass are associated with a serum marker of brain injury

Abstract

An increasing number of reports surrounding neurologic injury in the setting of cardiac surgery has focused on utilizing biomarkers as intermediate outcomes. Previous research has associated cerebral microemboli and neurobehavioral deficits with biomarkers. A leading source of cerebral microemboli is the cardiopulmonary bypass (CPB) circuit. This present study seeks to identify a relationship between microemboli leaving the CPB circuit and a biomarker of neurologic injury. We enrolled 71 patients undergoing coronary artery bypass grafting at a single institution from October 14, 2004 through December 5, 2007. Microemboli were monitored using Power-M-Mode Doppler in the inflow and outflow of the CPB circuit. Blood was sampled before and within 48 hours after surgery. Neurologic injury was measured using S100beta (microg/L). Significant differences in post-operative S100beta relative to microemboli leaving the circuit were tested with analysis of variance and Kruskal-Wallis. Most patients had increased serum levels of S100beta (mean .25 microg/L, median .15 microg/L) following surgery. Terciles of microemboli measured in the outflow (indexed to the duration of time spent on CPB) were associated with elevated levels of S100beta (p = .03). Microemboli leaving the CPB circuit were associated with increases in postoperative S100beta levels. Efforts aimed at reducing microembolic load leaving the CPB circuit should be adopted to reduce brain injury.

Figure 1.

Detection of microemboli in cardiopulmonary bypass circuit—location of Doppler sensors in the inflow and outflow of the cardiopulmonary bypass circuit.

Figure 2.

Distribution of microemboli leaving the cardiopulmonary bypass circuit—overall distribution of outflow microemboli (emboli leaving the cardiopulmonary bypass circuit) during the cardiopulmonary bypass period.

Figure 3.

Post-operative values of S100β by terciles of microemboli—relationship between terciles of microemboli measured in the CPB circuit (indexed by onpump time) and levels of S100β (postoperative values, p = .03).