Postoperative cognitive function (POCD) has been subject to extensive research. In the literature, large differences are apparent in methodology such as the test batteries, the interval between sessions, the endpoints to be analysed, statistical methods, and how neuropsychological deficits are defined. Traditionally, intelligence tests or tests developed for clinical neuropsychology have been used. The tests for detecting POCD should be based on well-described sensitivity and suitability in relation to surgical patients. In tests using scores, floor/ceiling effects may compromise the evaluation if the tests are either too easy or to difficult. Uncontrolled testing facilities and change of test personnel may affect the test performance. Practice effects are pronounced in neuropsychological tests but have generally been ignored. The use of a suitable normative population is essential to allow correction for practice effects and variability between sessions. Missing follow-up may severely compromise valid conclusions since subjects unable or unwilling to be examined are particularly prone to suffer from POCD. In the statistical analysis of the test results, the evaluation should be based on differences between pre- and postoperative performance. Parametric statistical tests are not relevant unless the appropriate Gaussian distributions are present, perhaps after transformation of data. The definition of cognitive dysfunction should be restrictive and the criteria should be fulfilled in only a small proportion of volunteers. In the literature, these requirements often have not been fulfilled. This precludes a reasonable estimation of the incidence of POCD and the conclusions of comparative studies should be interpreted with great caution. In this review article, we present a number of recommendations for the design and execution of studies within this area. In addition, the critical reader may use these recommendations in the evaluation of the literature.

Postoperative cognitive dysfunction occurs frequently but resolves by 3 months after surgery. It may be associated with decreased activity during this period. Subjective report overestimates the incidence of POCD. Patients may be helped by recognition that the problem is genuine and reassured that it is likely to be transient.

The incidence of postdural puncture headache (PDPH) was investigated prospectively in 873 consecutive patients undergoing a total of 1021 spinal anesthesias, and its association to age, sex, needle size, number of attempted dural punctures, needle bevel direction, duration of postoperative recumbency, and previous PDPH was analyzed. Multivariate analysis showed that age (P less than 0.0001), direction of the bevel of the needle when puncturing the dura mater (P = 0.022), and a history of previous PDPH (P = 0.018) were significant predictors of PDPH. The estimated relation between PDPH, on the one hand, and age and orientation of the bevel, on the other, enables the anesthetist to predict the risk of PDPH and thereby to choose an acceptable age limit for spinal anesthesia.