Impact of blood flow velocity changes during cardiac surgery with cpb to postoperative cognitive functions

Abstract

Introduction Postoperative cognitive dysfunction (POCD) occurs in 30-80% patients. Cerebral blood flow changes during surgery, especially via cardiopulmonary bypass (CPB), when it becomes nonpulsate. This is one of the factors, which may lead to various neurological complications. The aim of this study was to compare a. cerebri media (ACM) blood flow changes before, during and after heart surgery with CPB for patients with and without POCD based on Addenbrookes cognitive examination (ACE-III). Methods This prospective- case control study included patients undergoing elective coronary artery bypass grafting (CABG) or/and valve surgery with cardiopulmonary bypass (CPB). 110 patient completed ACE-III for cognitive evaluation. For determine mild cognitive dysfunction cut-off 88 was chosen. Mean flow velocity was monitored with transcranial doplerography device and evaluated 1 day before surgery, after anaesthesia induction, before CPB, at the beginning, ending and after of CPB, and post-surgery in ICU unit. Results 97 patients without preoperative cognitive dysfunction were examined, 67 (69.1%) male and 29 (29.9%) female; age 70± 9.2. According to ACE-III results patients were enrolled in to 2 groups: healthy patients without cognitive dysfunction after surgery were included into the first (H)group, patients with postoperative cognitive dysfunction (POCD) were included into the second (POCD) group. Groups did not differ according to age, comorbidities, amount of narcotic analgesia, duration of bypass and cross-clamping, ejection fraction. POCD was established for 29 patients. ACM blood flow velocity (BFV) was significantly higher after anaesthesia induction (mean 39.9 SE 2.2) comparing to velocity during CPB (mean 36.5; SE 2.4); p = 0.029 and lower after bypass (mean 36.5 SE 2.3) comparing to velocity after surgery (mean 38.7; SE 2.1) in POCD group; p = 0.000 ACM BFV was significantly lower before surgery (median 44.7) comparing to velocity after surgery (median 45.9); p = 0.001 and BFV after bypass (median 44.5) was lower comparing to BFV after surgery, (median 45.9); p = 0.018 in H group. ACM BFV during CPB was significantly lower in POCD group (median 36.12), comparing H group (median 54.9), p = 0.03. ACM BFV after surgery (median 34.43) was lower in POCD group comparing to H group (median 55.21),p = 0.01. Spearman correlation analysis revealed that ACM blood flow velocity during bypass was week positively correlated (Spearman Ro 0.339, p = 0.01) and moderate positively correlated (Sprearman Ro 0.428, p = 0.00) with ACE-III test result after surgery. Discussion Comparing ACM blood changes during heart surgery revealed that patients with mild cognitive dysfunction ACM velocity was lower than in patients without POCD, and correlation was found between lower ACE-III test results ant reduced blood flow.