Duration of antibiotic therapy in the intensive care unit

Abstract

There are certain well defined clinical situations where prolonged therapy is beneficial, but prolonged duration of antibiotic therapy is associated with increased resistance, medicalising effects, high costs and adverse drug reactions. The best way to decrease antibiotic duration is both to stop antibiotics when not needed (sterile invasive cultures with clinical improvement), not to start antibiotics when not indicated (treating colonization) and keep the antibiotic course as short as possible. The optimal duration of antimicrobial treatment for ventilator-associated pneumonia (VAP) is unknown, however, there is a growing evidence that reduction in the length of antibiotic courses to 7-8 days can minimize the consequences of antibiotic overuse in critical care, including antibiotic resistance, adverse effects, collateral damage and costs. Biomarkers like C-reactive protein (CRP) and procalcitonin (PCT) do have a valuable role in helping guide antibiotic duration but should be interpreted cautiously in the context of the clinical situation. On the other hand, microbiological criteria alone are not reliable and should not be used to justify a prolonged antibiotic course, as clinical cure does not equate to microbiological eradication. We do not recommend a 'one size fits all' approach and in some clinical situations, including infection with non-fermenting Gram-negative bacilli (NF-GNB) clinical evaluation is needed but shortening the antibiotic course is an effective and safe way to decrease inappropriate antibiotic exposure.

Keywords: Multidrug resistant (MDR); de-escalation; intensive care unit (ICU); sepsis; stewardship; ventilator-associated pneumonia (VAP).

Figure 1

Common situations with poor clinical response to antibiotics.

Figure 2

Empiric antibiotics thereafter may need to be modified once the results of blood or respiratory tract cultures become available. Modification may also be necessary if a resistant or unsuspected pathogen is found in a patient developing treatment failure. Alternatively, therapy can be de-escalated or narrowed if an anticipated organism (such as P. aeruginosa or an Acinetobacter species) was not found or if the organism isolated is sensitive to a less broad-spectrum antibiotic than was used in the initial regimen.