The impact of cardiac surgery on cognition

This brief review focuses on coronary artery bypass grafting (CABG) and valve surgery and their post-operative effects on cognitive domains. Despite the substantial technical advances in cardiac surgery over the past few decades, the incidence of permanent cognitive impairment remains alarmingly high: 20-70 per cent of patients exhibit cognitive impairment during the first week after surgery, with the incidence declining to 10-40 per cent after 6 weeks and remaining at this level thereafter. We find that language, concentration and motor control are most consistently reported to be affected, while memory, attention and executive function are more variably affected. Valve surgery is generally associated with a worse outcome than CABG surgery. It remains unclear whether the use of the cardio-pulmonary bypass machine adversely affects cognitive outcome. There is an urgent need to identify the risk factors and surgical techniques that influence post-operative cognitive impairment, yet it is difficult to reach meaningful conclusions from the present data due to a lack of concordance in experimental design and data analysis. To address this challenge, future research will need to control for confounds such as mood state, post-operative pain, learning effects, and anaesthesia and will need to compare a wide range of cognitive domains and surgical procedures within large multi-centre studies