[Clinical randomized controlled studies in anesthesiology according to quality guidelines of good clinical practice. 2: Principles of implementation, analysis, publication and evaluation].

This article was written to give researchers and clinicians a short synopsis of ethical and thorough design, conduct, analysis, publication, and interpretation of randomised controlled clinical trials according to the European quality standards of Good Clinical Practice (GCP). The paper consists of two parts. In the first part we introduce important elements of study design, especially study hypothesis, criteria of inclusion and study population, sample size calculation, validity considerations, bias and confounding, randomisation, stratification, and masking of treatment assignment. Different treatment allocation like multiple parallel groups, factorial experiment, cross-over, and sequential design are presented. Requirements of ethical standards according to the Declaration of Helsinki are discussed for their necessity in any experimentation in humans. Principles of informed consent are demonstrated with emphasis on special conditions in anaesthesia, emergency medicine, and intensive care research. In the second part of this article we explain issues of baseline assessment, experimental intervention, data recording, and data monitoring, particularly of negative or hazardous treatment effects. Topics of data analysis and reporting of trial results in publications are illustrated with regard to their influence on subsequent interpretation.