Patient summary documents provide crucial information about a patient, like allergies and adverse reactions, which are necessary for an efficient and safe treatment and offer a quick overview of the patients health status. Automatically generating patient summaries from Electronic Health Records (EHR) reduces the workload of medical personnel. Nevertheless, existing approaches do not take several challenges that occur in live operation into account. Based on a health standard-compliant approach, a system for on-demand generation of patient summaries was implemented and evaluated using real data. This work shows several problems which could be identified. Those problems are not covered sufficiently by current research. Possible approaches to a solution are suggested, which have to be further investigated in future work.