Changes in Mental Functions After Open-Heart Operations

Abstract
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. Intra-individual 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, parametric methods are unsuitable and nonparametric statistics should therefore be preferred.