[Laboratory testing in intensive care medicine]

Despite the tremendous technological developments in medicine, careful history-taking and clinical examination remain the cornerstones of diagnostics. Numerous laboratory tests are ordered in intensive care and emergency medicine. The rate of overutilization of these tests during initial patient admission is almost 50%. Patient history may be frequently insufficient for conducting targeted laboratory testing, and concern about not overlooking a pathology also contributes to laboratory test overutilization. On the other hand, laboratory test profiles are frequently defined a priori to simplify the management process. However, these profiles are commonly based on symptoms rather than on a suspected diagnosis. Several laboratory variables are outside the normal range in critically ill patients. However, normal ranges are defined on the basis of data from healthy subjects, and these do not allow for a clear distinction between stress adaptation and clinically relevant changes that require correction. Pathophysiological changes due to the acute injury in critically ill patients and the reaction of the organism to the injury or even to the treatment itself can lead to changes in laboratory values. Untargeted laboratory tests contribute to iatrogenic anemia and increased costs. The results of such tests are either hardly noticed or, in the worst case, lead to further unnecessary diagnostic steps and unjustified therapeutic measures. Point-of-care laboratory tests, including blood gas analysis, blood count, serum electrolytes, and lactate, to assess the patient's homeostatic state and laboratory data for the relevant critical care scores are uniformly required. Beyond that, every laboratory test should be chosen wisely based on a concrete clinical question.