Changes in mental functions after open-heart operations. Methodolgical aspects.

The authors present an attempt to develop methodological points of view on studies of changes in mental functions after various forms of anaesthesia and operation, e.g. open-heart operations. The value of results from unoperated control patients examined with the same methods and at the same intervals, is pointed out. Intraindividual changes in scores from pretest to post-tests seem to be the best measure of postoperative mental functions. For a more accurate appraisal of the results in a material of this kind, it is also recommended to make only a limited number of basic tests of specified hypotheses. For many investigations in this field para metric methods are unsuitable and nonparametric statics should therefore be preferred.