Blood Culture Positivity and Clinical Correlates of Bloodstream Infections in Post-cardiac Surgery Patients.

OBJECTIVE

To describe the positivity rate of blood cultures in postoperative cardiac surgical patients and identify clinical variables associated with bloodstream infection (BSI).

DESIGN

Retrospective cohort study.

SETTING

Single center.

PARTICIPANTS

All post-cardiac surgery intensive care unit patients for whom blood cultures were obtained between July 1, 2018, and June 30, 2023, were included. Patients were identified using the institution's Society of Thoracic Surgeons (STS) database.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN

RESULTS

For all patients, clinical variables and demographics were retrospectively obtained from the authors' institution's electronic medical record. During the study period, 3,095 patients underwent cardiac surgery, and 533 (17.2%) of them had blood cultures performed, resulting in a total of 1,294 cultures. The median day of culture acquisition was postoperative day 13 after the index surgery. Of the 1,294 cultures, 115 (8.9%) demonstrated BSI. Multivariate generalized linear mixed-effects regression analysis identified the following clinical variables to be independently associated with BSI: total parental nutrition in the 48 hours prior (odds ratio [OR] = 5.44, 95% confidence interval [CI] = 2.07, 14.30), severe thrombocytopenia (OR = 3.75, 95% CI = 1.75, 8.04), end-stage renal disease (OR = 2.19, 95% CI = 1.01, 4.78), mechanical ventilation during the 48 hours prior (OR = 1.92, 95% CI = 1.10, 3.36), and heart rate >100 in the 24 hours prior (OR = 1.70, 95% CI = 1.03, 2.79). Notably, neither fever nor leukocytosis was associated with culture-positive BSI.

CONCLUSIONS

In a single-center cohort of cardiac surgical patients, end-stage renal disease, tachycardia, recent mechanical ventilation, severe thrombocytopenia, and total parental nutrition were associated with BSI. Leukocytosis and fever were not found to be associated with culture-positive BSI. These risk factors should be validated in a prospective cohort study so that clinicians can better identify which patients are most likely to have BSI.