Base pneumonia treatment decisions on risk factors

A retrospective cohort study in Chest compared patients with community acquired pneumonia (CAP) admitted to an ICU with those admitted to a medical ward:

Conclusions: ICU patients present with more severe disease and more comorbidities. ICU patients stay longer in the hospital and have a much higher mortality rate when compared to ward patients.

While this was not particularly surprising or instructive the body of the paper contained important findings about the microbiology of CAP. True to prior experience, the etiology could be determined in only a minority of patients and among those with a microbiologic diagnosis Streptococcus pneumoniae was the most common pathogen. Other findings of note: Legionella antigen was not found in those patients tested and a surprisingly high number of Pseudomonas infections was found in both groups.

An accompanying editorial stressed that within the category of CAP are distinct risk groups that require different strategies. Some patients need a broader spectrum of antibiotics to include coverage for MRSA and Pseudomonas.

Current guidelines for both CAP and healthcare associated pneumonia (HCAP) recognize the need for risk stratification. Taken together the two guideline documents are potentially confusing: Whereas CAP and HCAP supposedly refer to distinct high and low risk categories with respect to the likelihood of difficult to treat pathogens, within both guideline sets are two or more such categories. Specifically, CAP guidelines stratify patients into those with high or low risk for pathogens such as Pseudomonas and MRSA whereas the HCAP guidelines stratify patients as high or low risk for “multiple drug resistant” (MDR) organisms. Antibiotic recommendations for the low risk categories in the two guideline documents are similar though not identical, as is the case for the antibiotic recommendations for the high risk categories of the respective documents.

I was lost when I first tried to sort through this. After preparing for this post, however, particularly after reading the paper and editorial in Chest, I began to appreciate the reasons for the multiple subtle distinctions. There are lessons here. Read the guidelines carefully with particular attention to the risk categories. In every encounter with a pneumonia patient ask yourself what risk category or categories apply.