100 QUESTIONS IN CARDIOLOGY

37 How common are neuropsychological

complications after cardiopulmonary bypass

(CPB)? How predictable and severe are they?

Can they be prevented?

Stan Newman and Jan Stygall

Neuropsychological complications have been found to occur in a

proportion of patients following CPB. These problems reveal

themselves as impaired cognitive function, i.e. difficulties with

memory, attention, concentration, and speed of motor and mental

response. However, the reported frequency with which these

problems occur varies considerably. Studies assessing patients

5–10 days postoperatively have suggested an incidence of

neuropsychological deficits ranging from 12.5 to 90%. Later

assessments, at about 2 to 6 months after surgery, have indicated

deficits in 12 to 37% of patients studied.

How predictable are they?

The variation in reported incidence has been ascribed to several

factors such as number, type, sensitivity, and timing of neuro-

psychological tests used, as well as the definition of neuro-

psychological deficit and the method of statistical analysis

employed. These methodological issues have been addressed at

international consensus conferences in 1994 and 1997. Patient

related variables such as age and disease severity have also been

associated with cognitive decline post-cardiac surgery. Therefore

centres employing different criteria for surgery may report

differing rates of deficit.

Deficits detected within a few days of surgery are also problematic

in that they are often transient in nature. These assessments appear

to be contaminated by postoperative readjustment and anaesthetic

residue as well as genuine neuropsychological difficulties. Long

term deficits (over 6 weeks) are considered to be more stable and to

reflect a more persistent neuropsychological problem.

How severe are they?

Given that these problems reflect a decline in performance of

approximately 20–25% from that prior to surgery, they can be