Postoperative cognitive dysfunction

Abstract

Background: Older patients in particular are vulnerable to memory disturbances and other types of cognitive impairment after surgical operations. In one study, roughly 12% of patients over age 60 had postoperative cognitive dysfunction (POCD) three months after surgery. This is an important issue in perioperative care as extensive surgery on older patients becomes more common.

Method: Selective review of the literature.

Results: POCD is usually transient. It is diagnosed by comparing pre- and postoperative findings on psychometric tests. Its pathogenesis is multifactorial, with the immune response to surgery probably acting as a trigger. Factors that elevate the risk of POCD include old age, pre-existing cerebral, cardiac, and vascular disease, alcohol abuse, low educational level, and intra- and postoperative complications. The findings of multiple randomized controlled trials indicate that the method of anesthesia does not play a causal role for prolonged cognitive impairment. POCD is associated with poorer recovery and increased utilization of social financial assistance. It is also associated with higher mortality (hazard ratio 1.63, 95% confidence interval 1.11-2.38). Persistent POCD enters into the differential diagnosis of dementia.

Conclusion: POCD can markedly impair postoperative recovery. The findings of pertinent studies performed to date are difficult to generalize because of heterogeneous patient groups and different measuring techniques and study designs. Further investigation is needed to determine which test instruments are best for clinical use and which preventive strategies might lessen the incidence of POCD.

Figure 1

Left: the Trail Making Test, Part A—connect the numbers, in ascending order, with a line. Right: the Trail Making Test, Part B—connect the numbers in ascending order and the letters in alphabetical order with a line. The time needed to do each part is measured in seconds. This is a test of dexterity and of the ability to combine tasks.

Figure 2

Left: the Digit Span Test measures how many digits presented in sequence the subject can remember (short-term memory). Right: in the Stroop Test, the printed words must be read out loud and the color they are printed in must be named. If the word is a color word that is printed in a different color, the reaction time and error rate are higer. This is a test of attention and concentration in the presence of distractors.

Figure 3

Erzigkeit’s Short Cognitive Performance Test (18) Pictures for Subtests 1 and 2 (left): the pictures shown are to be named (time measured in seconds). After a brief pause, it is then determined how many of these pictures the subject can remember (short-term memory). Board for Subtests 3, 4, and 5 (right): the numbers are to be read out loud, sorted in ascending order, and then re-sorted in the area below. The time needed for this is measured. The purpose of the subtests is to assess information processing and motor skills.