Research protocol: Microbiology in pleural effusions in the intensive care unit - A retrospective cohort study
Creators: name: Frambo, Søren Philip
name: Arge, Símun Ingi
name: Rasmussen, Bodil Steen
name: Nielsen, Hans Linde
name: Søgaard, Kirstine Kobberøe
name: Schjørring, Olav Lilleholt
Publisher: name: Zenodo
Year: 2023
Subjects: subject: Blood culture
subject: Critical illness
subject: Intensive care units
subject: Microbiology
subject: FOS: Biological sciences
subject: Observational study
subject: Pleural effusion
subject: Pleural fluid culture
subject: Pneumonia
subject: Thoracentesis

description: Pleural effusions are a common occurrence in intensive care unit (ICU) patients with reported prevalence rates ranging from 37% to 80%. Thoracentesis is often performed in ICU patients, and pleural fluid culture is routinely conducted. However, there is a lack of comprehensive data regarding the prevalence of positive cultures from pleural fluid in a large ICU population, particularly in relation to the indications for thoracentesis. Additionally, the correlation between microbiological findings in pleural fluid and other microbiologic test results, as well as association with mortality, remains unclear. This is a protocol for a retrospective regional observational cohort study with the objective to quantify the prevalence of positive cultures from pleural fluid in ICU patients based on the indication for thoracentesis and the presence of ipsilateral pneumonia. Additionally, the correlation between microbiological findings in the pleural fluid and associations with 90-day all-cause mortality, as well as with results from blood cultures and cultures of airway secretions will be investigated. We hypothesize that positive cultures from primary pleural fluid samples obtained from adult ICU patients are rare, with a prevalence of less than 10%. Furthermore, we expect that diagnostic thoracentesis will be associated with a higher incidence of positive cultures compared to therapeutic thoracentesis, and that parapneumonic effusions will be associated with a higher incidence of positive cultures compared to non-parapneumonic effusions. As a secondary hypothesis, we postulate that a positive culture from pleural fluid will be linked to a higher 90-day all-cause mortality compared to a negative culture in adult ICU patients who undergo thoracentesis with pleural fluid sampling for culturing. The study will include all adult patients (aged 18 years or above) who were admitted to any of the eight ICUs in the North Denmark Region and had pleural fluid culturing performed during their ICU stay over a 10-year period from March 1, 2013, to February 28, 2023. The primary outcome measure will be a positive pleural fluid culture. The secondary outcome will be all-cause mortality within 90 days from the primary pleural fluid sampling, and its association with the primary outcome will be assessed. This study will contribute valuable insights into the prevalence of positive cultures from pleural fluid in ICU patients, their correlation with other microbiologic findings, and their association with 90-day mortality. The findings may inform clinical decision-making and optimize the management of pleural effusions in critically ill patients.