Association of body mass index and bloodstream infections in patients on extracorporeal membrane oxygenation: a single-centre, retrospective, cohort study

Background: Obesity is associated with poor clinical outcomes in critically ill patients. However, under some clinical conditions, obesity has protective effects. Bloodstream infections (BSI) are among the most common nosocomial infections associated with extracorporeal membrane oxygenation (ECMO). BSI during ECMO is associated with higher mortality rates and poorer clinical outcomes. Aim: To analyse whether body mass index (BMI) is associated with BSI during ECMO or with in-hospital mortality. Methods: All adult patients who had received ECMO support for >48 h were included in the analysis. The analysis of total duration of ECMO support, in-hospital mortality and BSI was stratified by BMI category. The Cox proportional hazards model was used to compare the risk of BSI among BMI categories. Findings: In total, 473 patients were enrolled in the study. The average age was 56.5 years and 65.3% were men. The total duration of ECMO was approximately 11.8 days, with a mortality rate of 47.1%. The incidence rates of BSI and candidaemia were 20.5% and 5.5%, respectively. The underweight group required ECMO for respiratory support, whereas the overweight and obese groups required ECMO for cardiogenic support (P<0.0001). No significant difference in BSI rate was found (P=0.784). However, after adjusting for clinical factors, patients in Group 4 (BMI 25.0–<30.0 kg/m²) exhibited lower mortality compared with patients in Group 2 (normal BMI) (P=0.004). Conclusion: BMI was not associated with risk of BSI, but patients with higher BMI showed lower in-hospital mortality associated with ECMO support.