Biological effects of coronary surgery: role of surgical trauma and CPB

We did read with interest the Letter to the Editor from Dr Raja in the May issue of the EJCTS [1]. He commented the prospective randomised study, comparing off-pump and on-pump CABG, by Wehlin recently published in the EJCTS [2]. Moreover, he quoted as reference a review paper about the same topic from our group [3]. Here we would make some comments about the contents expressed by Dr Raja. First, quoting the review paper from our group, he stated that excessive shear stress during CPB may cause damage to blood constituents, activation of the inflammatory response, platelet activation and it may contribute to endothelial injury. We recognize that the shear stress may have a potential role in the pathophysiology of the CPB. Nevertheless, we have to point out that our literature review did not investigate the evidences about the relationships between shear stress and CPB [3]. Moreover, we also recognize that the CPB may elicit the inflammatory response by means of several pathways. However, the evidences emerged from the available literature comparing on-pump surgery to offpump surgery, including even major thoracic and abdominal surgery, suggest that CPB may have a limited role in inflammatory and hemostatic derangements during the perioperative period. Moreover, such role seems to be limited to the final steps of the operation and the very early postoperative hours [3]. On the other side, it is likely that the trauma to the tissue, imposed by the surgical procedure, may be the more consistent source of proinflammatory and pro-coagulant mediators during the entire perioperative period. In our opinion, the observations from Wehlin and colleagues are a further confirmation of this hypothesis [2].