DI-SPME-LC-MS was recently applied to study the human plasma metabolome in patients undergoing cardiac surgery [42]. The results showed that the metabolites extracted allowed the detection of changes in metabolic pathways induced by the surgery and the applied pharmacotherapy. The most significant changes were observed in metabolic profiles of lysophospholipids, triacylglycerols, mediators of platelet aggregation, and linoleic-acid metabolites. In addition to the observation of general trends in the studied group, personalized responses to therapy characterized by different changes in metabolic pattern were also noted in individual patients. As personalized therapy is one of the main aims of modern medicine, SPME, as a fast, simple sample-preparation/extraction tool, could be employed for on-site (bed-site) diagnostic assay when combined with rapid analytical instrumentation.