|dc.description.abstracteng||Postoperative acute kidney injury (AKI) is a frequently observed phenomenon after cardiac surgery with the use of cardio-pulmonary-bypass (CPB) and a severe complication which is associated with adverse patient outcome. To apply preventive and therapeutic measures it is essential to identify at risk patients. To estimate the individual risk for AKI, scoring systems were developed. Adequate scores then allow not only focused applying of preventive measures but also an objective analysis of its effect.
This project evaluated, validated, and applied the Thakar score. Prior studies, with the endpoint criterion "renal replacement therapy", reported good discrimination but not constantly good calibration. Since implementation of RIFLE and AKIN classification, which are objective, comparable, and precise definitions of AKI, the original endpoint criterion turned obsolete. Thus, the evaluation of the consequences of applying an adequate endpoint-criterion is of predominantly clinical importance for the implementation of the Thakar score. The present study adjusted not only the endpoint-criterion to current standards but also optimized data acquisition and the evaluation of risk factors by prospective study design. However, these modifications did not lead to good calibration or discrimination. Only adding intraoperative risk factors improved discrimination. I conclude that when developing scoring systems, it is essential that they base on precise parameters, which are not in need of interpretation, and that the endpoint criterion is objective and consistent and also corresponds to current standards. This would allow correct evaluation of AKI risk and further steps of implementation and improvement of prevention and therapeutic strategies may follow. In a second part, we demonstrated the application of the Thakar score when clarifying the question if the preemptive administration of sodium bicarbonate can prevent AKI. With the use of the score we estimated and ensured comparable risk configuration in the control group and the group where patients were treated with sodium bicarbonate. I found that sodium bicarbonate significantly decreased the incidence of AKI.||de