Positive Pleural Fluid Cultures in the ICU: A 10-Year Population-Based Cohort Study of Prevalence, Microbial Characteristics, and Clinical Associations.

OBJECTIVE

Pleural effusions are common in the ICU, often requiring drainage. Although fluid cultures are frequently obtained, pleural microbial findings in ICU patients remain poorly characterized. The current study aimed to assess prevalence and microbial characteristics of positive pleural fluid cultures in ICU patients, assessing positive cultures' associations with clinical assessments and 90-day mortality.

DESIGN

Retrospective population-based cohort study of pleural fluid cultures in ICU. The primary outcome was the proportion of first pleural fluid cultures yielding positive microbial growth, secondary outcome was 90-day all-cause mortality. Using multiple regression, we assessed associations between suspected pleural infection and parapneumonic effusion, respectively, and the risk of a positive culture, as well as associations between a positive culture and 90-day mortality.

SETTING

Data from eight ICUs comprising the entire North Denmark Region from March 1, 2013, to February 28, 2023, were obtained from the regional microbiological database, administrative databases, and through review of electronic medical records.

PATIENTS: All adult patients who underwent pleural fluid culturing in any of the eight ICUs within the inclusion period.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN

RESULTS

A total of 1251 patients were included, of whom 51 (4.1%) had a positive first pleural culture. Suspected pleural infection was associated with a higher positive culture risk (adjusted risk ratio [RR]: 4.88; 95% CI, 2.70-8.83). No such association was observed for parapneumonic effusions (adjusted RR: 1.41; 95% CI, 0.83-2.38). A positive culture was associated with increased 90-day mortality (adjusted RR: 1.35; 95% CI, 1.04-1.73).

CONCLUSIONS

In this 10-year cohort study of ICU patients undergoing pleural drainage, the risk of positive pleural fluid cultures was low. Suspected pleural infection significantly increased the likelihood of a positive culture, suggesting that culturing may be most useful in these cases. A positive pleural culture was associated with increased 90-day mortality underscoring its potential clinical significance.