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Critically ill patients are at very high risk of developing severe infections, with incidence rates five to ten times higher than general wards.1 Data from US hospitals covering 2009 to 2010 showed that, although patients in critical care wards represent only 15.1% of the hospital population, they developed almost 43% of healthcare-associated infections (HAIs). Approximately 65% of all device-related HAIs occurred in intensive care unit (ICU) settings.1,2

Critically ill patients have numerous insults to normal host mechanisms. Peripheral and/or central access devices or wounds usually compromise skin integrity. Certain immunosuppressive medications decrease the ability of the immunologic defenses to function properly. Furthermore, other underlying medical conditions, such as diabetes, malnutrition, and renal disease, may predispose patients to infectious complications.

Antimicrobials are consistently among one of the most important and commonly prescribed drugs; appropriate policies for their use must exist in the ICU. A survey of antibiotic usage in the United States from 2011 demonstrated that almost 50% of all patients in hospitals received at least one antibiotic medication. This number approached 75% of patients in critical care settings.2,3 The success of these drugs is dependent on many factors; therefore, it is imperative for healthcare providers to have a clear understanding of antimicrobial use in the critically ill patient.

General principles of antimicrobial use in critical care should include the following35:

  • Healthcare providers need to have a clear understanding that all fevers and leukocytosis are not always caused by infections. Systemic inflammatory response syndrome (SIRS) can be due to many noninfectious causes; thus, empirical antimicrobials are not always indicated.

    • Pursue diagnostic studies for both infectious and noninfectious causes until a diagnosis is reached.

  • Always attempt to arrive at a diagnosis for the syndrome encountered.

    • Clinical outcomes are improved when a diagnosis is reached and targeted therapy is provided.

  • Develop an empirical antimicrobial therapy based on differential diagnosis and predicted mortality.

    • Treat patients with sepsis with broad-spectrum antibiotics empirically.

    • Modify therapy to the most narrow-spectrum antibiotic when site and microbiology of the infection is defined.

    • Source control is essential for optimal care.

  • Appropriately dose antimicrobials to achieve adequate dosing and minimize toxicity.

    • In cases of sepsis, early and appropriate administration is essential to improve survival.

    • Modify doses in patients with renal or hepatic dysfunction.

    • Have awareness of drug interactions with other medications.

  • Define and continually address duration of antimicrobial therapy.

    • Tailor therapy based on microbiologic results and clinical response.

    • Discontinue antimicrobials if a noninfectious etiology is documented.

    • Base duration of therapy on clearly established standards.

  • Address antimicrobial resistance, including use of surveillance cultures.

    • Antimicrobial stewardship is needed.


There are several considerations when evaluating a critically ill, febrile patient.6 The normal human body temperature is 37 ± 0.5 to 1°C, and may be affected by ...

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