Postoperative Cognitive Decline After Cardiac Surgery: A Narrative Review of Current Knowledge in 2019

Abstract

The growing number of publications concerning postoperative cognitive decline (POCD) after cardiac surgery is indicative of the health-related and economic-related importance of this intriguing issue. Significantly, the reported POCD incidence over the years has remained steady due to various unresolved challenges regarding the examination of this multidisciplinary topic. In particular, a universally accepted POCD definition has not been established, and the pathogenesis is still vaguely understood. However, numerous recent studies have focused on the role of the inflammatory response to a surgical procedure in POCD occurrence. Therefore, this traditional narrative review summarizes and evaluates the latest findings, with special attention paid to the difficulties of defining POCD as well as the involvement of inflammation in POCD development. We searched the MEDLINE, Scopus, PsycINFO and CENTRAL databases for the best evidence, which was classified according to the Oxford Centre for Evidence-based Medicine. To our knowledge, this is the first narrative review that identified class-1 evidence (systematic review of randomized trials), although most evidence is still at class-2 or below. Furthermore, we revealed that defining POCD is a very controversial matter and that the inflammatory response plays an important role in the mutually overlapping processes included in POCD development. Thus, developing the definition of POCD represents an absolute priority in POCD investigations, and the inflammatory response to cardiac surgery merits further research.

Evaluation of the Risk Factors for Postoperative Neurocognitive Disorder in Elderly Patients Following Coronary Artery Bypass Grafting.

“…Moreover, brain impairment after heart surgery was found to be more extensive and not confined to hippocampal brain regions in the animal study [12]. A review by Glumac et al summarized that the current definition of PND is controversial and lacks consistency and the inflammatory response after cardiac surgery plays an important role in the pathogenesis of PND [13]. Which is worthy of further study.…”

Multiple Anesthesia/Surgery Cannot Impair Reference Memory in Adult Mice

“…Spatial reference memory in mice from the control and the multiple anesthesia/surgery groups was evaluated in the Morris water maze (MWM) since the second day after the last surgery. In different cohorts of animals, 8 mice from control, single anesthesia/surgery, and multiple anesthesia/surgery groups were euthanized at each time point (6,24, and 48 h after surgery) in each group. Hippocampus tissue and serum were harvested for the measurements of IL-1β, IL-6, TNF-α, and IL-10 by enzyme-linked immunosorbent assay (ELISA).…”

“…The condition is characterized by impaired learning and memory and may persist for months and years after surgery [4,5]. POCD is thought to be associated with major surgery and advanced age [6,7], and there is no doubt that older individuals are more likely to develop POCD [8]. Although POCD does occur in adults in clinical settings, whether adult mice develop similar learning and memory impairment after anesthesia/surgery remains controversial.…”

Current Evidence Regarding Biomarkers Used to Aid Postoperative Delirium Diagnosis in the Field of Cardiac Surgery—Review

“…Additionally, tests are not free of interfering confounders, such as ceiling or floor (basement) effect. Glumac et al found over 100 different neuropsychological tests that were being used for the diagnosis of delirium [ 59 ]. Difficulties and problematic use of them result indirectly from the non-uniform use of the definition of POD and postoperative cognitive dysfunction (POCD) [ 19 , 58 ].…”

“…Due to the multitude of diagnostic tests, many studies cannot be compared, and the results obtained in many different ways may mask the real number of patients with delirium [ 19 ]. Sheth et al proposed a period of seven days from the time of cardiac surgery until the test for cognitive impairment due to the direct influence of drugs and the hospital environment on the patient’s condition, while Glumac et al stated that the tests should be performed preoperatively and in the early postoperative period (seven to 14 days after the procedure), but also even 6 to 9 months after surgery [ 59 , 60 ].…”