Predictors of mortality in a Chinese medical ICU: a focus on ICU-acquired bloodstream infections

BACKGROUND: Bloodstream infection (BSI) is a leading cause of morbidity and mortality among critically ill patients. This retrospective study aimed to determine the frequency of a medical intensive care unit (ICU)-acquired BSIs and identify the mortality risk factors associated with BSIs in critically ill patients within the medical ICU who were transferred from the internal medicine department, not from the surgical department after a surgery. METHODS: Blood samples were processed using the BACTEC 9240 blood culture system, with species identification conducted for culture-positive cases using a Bruker mass spectrometer, and susceptibility tests by Vitek-2 system, or TDR YEAST-AST system. Pre-specified risk factors for mortality were analyzed through logistic regression. RESULTS: Over a 9-year period, 113 isolates of BSI occurred in 106 (2.2%) of 4820 patients. Gram-negative bacteria predominated as the primary pathogens, accounting for 64.6% of all isolated pathogens. The most frequent pathogen was Enterobacteriaceae (36.3%), primarily Klebsiella pneumoniae (25.7%). The lungs were the most common source of infections. Septic shock was present at the onset of BSI in 71 (67.0%) patients. Of the total, 66 (62.3%) patients died within 1 month following the onset of BSIs. Multivariate analysis identified the following independent factors for 1-month all-cause mortality: lymphocyte count < 0.5 × 10⁹/L (OR = 4.305) and septic shock (OR = 3.275), while BMI ≥ 23 (OR = 0.181) and appropriate antibiotic treatment (OR = 0.333) remained protective. CONCLUSIONS: This study, focusing on a high-risk medical ICU population with BSIs, identifies key factors associated with mortality: septic shock as the predominant risk factor, the prognostic relevance of severe lymphopenia, the critical role of appropriate antibiotics, and the potential consideration of the “obesity paradox” (BMI ≥ 23) in patient assessment.