No abstract

Sir,With great interest, we have read the article by Messerotti Benvenuti and colleagues about preliminary evidence for reduced preoperative cerebral blood flow (CBF) velocity as a risk factor for cognitive decline three months after cardiac surgery. 1 The occurrence of neurocognitive decline (NCD) is a significant problem in cardiac surgery due to its high incidence. Preoperative detection of reduced CBF velocity may help the surgical team to detect patients who have a higher risk of developing neurocognitive impairment and, therefore, in the future, possibly enable them to conduct certain intraoperative management in order to reduce the occurrence of NCD; however, that still remains contradictory and needs to be scientifically verified. With this research, the authors provide an important step forward in the aim of reaching better and timely applied neuroprotection in patients undergoing cardiac surgery.The occurrence of postoperative NCD is also affected by other influencing factors that were, in our opinion, not properly stressed and adequately elaborated on by the authors. Those factors could have a significant impact on the outcome and, therefore, on the interpretation of results as well as the conclusion of the conducted study. In the preoperative period, these factors are hypertriglyceridemia and calcified aorta in the form of so called "aortic atheroma burden". 2,3 Although the authors focus on preoperatively reduced CBF in the left middle cerebral artery as a risk factor for postoperative NCD and, by that, concentrate on the correlation between pre-existing hemodynamic disturbances and NCD, the surgical technique and the approach being used during the intraoperative period are also major influencing factors. In the study, as much as one third of the patients underwent some form of surgical myocardial revascularization. The increased number of surgical manipulations on the ascending aorta for proximal anastomosis creation lead to neurocognitive damage. Hammon et al. say that a single-clamp strategy leads to neurocognitive status improvement in the 6-months follow-up period. 4 We believe that all patients included in the study should have undergone the same surgical procedure or, if different procedures were being used, the authors should have emphasized the differences between the groups in order to eliminate possible bias in data processing and to achieve the most objective conclusion. The occurrence of postoperative arrhythmias, not only pre-existing arrhythmias, especially atrial fibrillation, has a direct impact on the reduction of cardiac output, which may precipitate and induce thrombus formation in cardiac cavities, which could then lead to NCD via embolization. 5 A rapid rewarming strategy on cardiopulmonary bypass and postoperative hyperthermia in the first 24 hours after the surgical procedure are associated with severe cognitive dysfunction. 6,7 In conclusion, we believe that, in future studies, it would be exceptionally important to appropriately design the study. Since observational research...