Original contributionCD11b may be a less satisfactory indicator for cardiac ischemia-reperfusion injury in coronary artery bypass graft surgery with cardiopulmonary bypass than cardiac troponin I☆
Introduction
During cardiac operation, a series of events can lead to myocardial ischemia such as aortic cross-clamping, cardiopulmonary bypass (CPB), and the subsequent coronary reperfusion. Previous studies have demonstrated that myocardial ischemia/reperfusion injury can potentiate the inflammatory response [1] and the up-regulation of adhesion molecule expression on the neutrophil membrane [2], such as CD11b [3], [4]. Therefore, it is reasonable to take the up-regulation of adhesion molecule expression on the neutrophil membrane as a diagnostic indicator of cardiac damage in cardiac operations with CPB. However, several factors could influence adhesion molecule expression, producing misleading information. First, not only cardiac ischemia-reperfusion procedures but also nonspecific inflammatory events such as CPB per se could elicit heart damage [5]. It is, therefore, rather difficult to differentiate whether the CD11b up-regulation is caused mainly by an ischemia/reperfusion event or by CPB only, a nonspecific inflammation episode. Second, CPB can result in multiorgan inflammatory reaction [3], [4], [5], [6]. Besides the heart, other organs, including the lungs, are also major sites of inflammatory responses during the early reperfusion period [7]. In contrast to cardiac troponin I (cTnI), CD11b is not an organ-related specific parameter, so it is difficult to evaluate the injury of a certain organ based only on the up-regulation of CD11b on circulating neutrophils. Finally and most importantly, some organs have specific sequestration effects on circulating activated blood cells, including neutrophils [5]. In this case, a low level of CD11b expression on neutrophils in blood flowing out from these organs could be observed. In this study, we investigated and evaluated whether the transcardiac (coronary sinus blood vs systemic circulation blood) expression of CD11b could still be regarded as a useful myocardial damage indicator in patients undergoing coronary artery bypass graft (CABG) surgery on CPB. A very specific and sensitive marker of myocardial injury [8], cTnI was used as a reference indicator.
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Materials and methods
The clinical investigation protocol was approved by the Ethics Committee of the China-Japan Friendship Hospital.
Results
Before CPB, all hemodynamic parameters were kept stable and within physiological ranges by adequate sedation and analgesia. During cardiopulmonary circulation, mean arterial blood pressure was maintained at 50 to 60 mm Hg by pump flow set at 1.6 L/(min·m−2). The vessels for grafting are 3.08 ± 0.6; aortic clamping time, 66.6 ± 12.7 minutes; CPB time, 106.1 ± 15.4 minutes; and operation time, 5.03 ± 0.7 hours. All patients recovered very satisfactorily after their operations.
Discussion
In cardiac operation with CPB, the up-regulation of CD11b expression on neutrophils can be stimulated by 2 factors: (1) nonspecific inflammatory reaction produced by CPB per se and (2) myocardial ischemia/reperfusion injury happened during CPB and especially after aortic declamping. During CPB, factors such as the circulation of blood within the extracorporeal system and the use of priming solutions, among others, can cause nonspecific inflammatory reaction. The activated inflammation
Acknowledgments
The authors thank Dr Fenglin Wang, Dr Peng Liu (Department of Cardiovascular Surgery, China-Japan Friendship Hospital), Dr Qing Xiang (China-Japan Friendship Clinical Institute), Dr Wei Cui (Laboratory of Pekin Union Hospital, Peking Union Medical College), and Dr Ming Li (Laboratory of An Zhen Hospital, The Capital Medical University).
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Supported in part by a grant from the Ministry of Education, Beijing, China.