Rethinking the "Pan-Culture": Clinical Impact of Respiratory Culturing in Patients With Low Pretest Probability of Ventilator-Associated Pneumonia

Background: Respiratory cultures are often obtained as part of a "pan-culture" in mechanically ventilated patients in response to new fevers or leukocytosis, despite an absence of clinical or radiographic evidence suggestive of pneumonia.

Methods: This was a propensity score-stratified cohort study of hospitalized mechanically ventilated adult patients between 2014 and 2019, with a new abnormal temperature or serum white blood cell count (NATW), but without radiographic evidence of pneumonia, change in ventilator requirements, or documentation of purulent secretions. Two patient groups were compared: those with respiratory cultures performed within 36 hours after NATW and those without respiratory cultures performed. The co-primary outcomes were the proportion of patients receiving >2 days of total antibiotic therapy and >2 days of broad-spectrum antibiotic therapy within 1 week after NATW.

Results: Of 534 included patients, 113 (21.2%) had respiratory cultures obtained and 421 (78.8%) did not. Patients with respiratory cultures performed were significantly more likely to receive antibiotics for >2 days within 1 week after NATW than those without respiratory cultures performed (total antibiotic: adjusted odds ratio [OR], 2.57; 95% CI, 1.39-4.75; broad-spectrum antibiotic: adjusted OR, 2.47, 95% CI, 1.46-4.20).

Conclusions: Performance of respiratory cultures for fever/leukocytosis in mechanically ventilated patients without increasing ventilator requirements, secretion burden, or radiographic evidence of pneumonia was associated with increased antibiotic use within 1 week after incident abnormal temperature and/or white blood cell count. Diagnostic stewardship interventions targeting performance of unnecessary respiratory cultures in mechanically ventilated patients may reduce antibiotic overuse within intensive care units.