Either analgosedation or central nervous system dysfunction may be a side effect of implemented pharmacological treatment, as well as a consequence of intentional or unintentional poisoning. In traumatic lesions or anoxia of the central nervous system, a question arises after a recommended follow-up period about the effects of xenobiotics on nervous system function. Although therapeutic drug monitoring is the gold standard in such cases, usually a single toxicological estimation of "a neurodepressive compound" is performed after treatment discontinuation in order to determine the type and amount of exogenous substances, or their metabolites, in a patient's bodily fluids, which allows for an assessment of its actual effects on central nervous system functions. The aim of this paper was to describe the aspects of diagnostic toxicology which are essential for improved determination of the type and amount of exogenous substances present in biological fluids of intensive care patients. We present examples of clinical cases in order to discuss the most common discrepancies in interpretation related to the ordering of toxicology tests.
Keywords: ICU treatment; diagnostic toxicology; neurodepressants; therapeutic drug monitoring; xenobiotics.