| Resumo: | Sepsis, inducing multiorganic dysfunction, is the main cause of death in burn patients. A prompt and appropriate selection of antimicrobial therapy is crucial for their outcome. The difficulty in distinguishing true sepsis from physiological inflammatory response associated to burn injury, strongly contributes to an inadequate management of these patients, potentially leading to delayed antimicrobial therapy, increased mortality, or to superfluous antimicrobial prescription, raising the incidence of adverse events and microbial resistance. Several clinical and/or laboratorial biomarkers have been used to help clinicians to distinguish sepsis from systemic inflammatory response, namely at the Emergency and Intensive Care Departments. Among the available biomarkers, procalcitonin (PCT) is recognized as the most reliable for this purpose. The main objective of this thesis was to investigate the potential role of PCT as part of antimicrobial stewardship programs in burn patients. Taking a sample of patients from a Burn Unit of a tertiary care hospital and using specific burn sepsis definition, the results showed that PCT compared with traditional biomarkers (leucocyte and platelet countings, prothrombinemia, D-dimers, C-reactive protein, serum lactate and temperature) was the best biomarker for an early diagnosis of sepsis. An alert cut-off of 0.5 ng/mL was proposed as reason for daily PCT assessment, with empirical antimicrobial therapy recommended for values above 1.0-1.5 ng/mL. PCT demonstrated a close and statistically significant correlation with the mortality. Sustained increased values during antimicrobial therapy showed a correlation with therapeutic failure, as opposed to what happened when PCT levels consistently fell. PCT kinetics proved to be of great value for the differential diagnosis between sepsis and early inflammatory response associated with burn injury as well as for the diagnosis of postoperative sepsis in these patients. PCT levels were found to be significantly higher in patients with Gram-negative sepsis comparing to patients with Gram-positive sepsis and controls. Subgroup analysis showed that the most elevated values occurred in patients with sepsis caused by non-fermentative Gram-negative bacteria, by Klebsiella pneumoniae and, in a lesser extent, by other Enterobacteriaceae. PCT values under 0.5- ng/mL almost excluded infections due to Gram-negative bacteria. While faster, more reliable and cheaper methods of microbiological identification are not developed and widely available, repeated PCT measurements, coupled with careful anamnesis and clinical examination, empowering prescription decisions, should be included in antimicrobial stewardship programs in Burn Units in order to increase antimicrobials effectiveness, to reduce mortality, to avoid adverse events and the development of microbial resistance, and to minimize the financial burden
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