Evaluating new fever in adult patients in the ICU: A guidelines update

Fever is a frequent early indicator of infection and occurs in 26% to 88% of adult patients in the intensive care unit. While noninfectious causes are possible, initial evaluation of patients with new-onset fever is usually directed at potential microbial causes as starting treatment early may improve the outcomes of infections. Naomi P. O’Grady, MD, FIDSA, and Stanley Deresinski, MD, FIDSA — co-chairs of the panel that developed the latest updates to guidelines on the topic from IDSA and the Society of Critical Care Medicine — answered several questions from Science Speaks about the update.

Who are these new guidelines primarily intended for? Who will find them most useful? 

The guideline will be of use to any clinician involved in the care of intensive care patients. It likely will be of most use to intensivists, but others, including consultants in infectious diseases, pulmonary medicine and surgery, and hospitalists will benefit from interactions with the clinical microbiology laboratory and imaging consultants.

What are the most notable updates or changes compared to the 2008 guidelines on this topic?

The most notable change is the application of the Grading of Recommendations Assessment, Development and Evaluation, or GRADE, methodology to evaluate the quality and strength of the evidence supporting a recommendation. Among the added or changed items or issues discussed are the following:

• We recommend against the routine use of antipyretics. We recommend performance of CT scanning in patients who have recently undergone thoracic, abdominal or pelvic surgery in cases in which the etiology of fever is not determined during initial evaluation. Evidence regarding use of white blood cell scanning or PET-CT was deemed to be insufficient to allow a recommendation.
• We recommend against routine use of abdominal ultrasound examination but recommend use of a formal ultrasound study in patients with clinical or laboratory findings raising suspicion of an intraabdominal source of the fever. Bedside thoracic ultrasound may be considered in patients with abnormal chest radiographs in order to better delineate pleural effusions and parenchymal abnormalities.
• Detection of elevated procalcitonin or C-reactive protein cannot be used to eliminate the presence of bacterial infection, but it may be of use in patients otherwise determined to have a low to intermediate probability of bacterial infection together with other findings. In patients with suspected respiratory tract infection, testing for viral pathogens using nucleic acid amplifications tested should be performed.
• At least two sets of blood cultures should be obtained from separate sites. When infection of a central venous catheter is suspected, blood for culture should be obtained at the same time from the catheter (from at least two lumens) and from peripheral blood in order to determine the differential time to positivity. Rapid molecular tests to detect blood pathogens should only be used in conjunction with routine culture methods.
• When urinary infection is suspected in a patient with pyuria and an indwelling bladder catheter, urine sampling should be obtained after replacement of the catheter.

Several of the recommendations relate to diagnostics and imaging studies. What are the guidelines’ key takeaways in these areas when evaluating and managing these patients?

An issue of key importance is the limited quantity of quality evidence available in the evaluation of diagnostic testing in these patients. The most important needed advancements will likely largely revolve around improvement in rapid diagnostics that not only reliably provide an etiologic diagnosis but also detect antimicrobial resistance/susceptibility. The application of artificial intelligence may allow for early prediction/detection of infection onset.

The guidelines call for “rapid advancement of research” to address knowledge gaps in how to deal with new onset of fever in patients receiving critical care. What are some of the most important gaps that additional research needs to address?

One specific area that needs improvement is developing a noninvasive method to measure core body temperature with accuracy and precision. Another area that lacks data includes diagnostic imaging studies for patients in the ICU. Certainly, having portable imaging testing reduces the risk of transporting patients, but there is very little literature to suggest that portable imaging is as good as standard imaging. Lastly, while we have made advances in rapid molecular diagnostic testing as it relates to viral diseases, more advances could be made targeting bacterial and fungal diseases.

What else should health care providers know about the updated guidelines? 

It must be recognized that application of the GRADE system, which was initially designed for evaluation of therapeutic interventions, to diagnostic testing is often problematic. Diagnostic testing is overused in the intensive care setting, and this may be ameliorated by careful bedside clinical evaluation.

Read the updated guidelines, “Society of Critical Care Medicine and the Infectious Diseases Society of America Guidelines for Evaluating New Fever in Adult Patients in the ICU.”