Body mass index and in-hospital mortality have a U-shaped relationship among critically ill cardiac surgery patients

1. A U-shaped relationship was found between body mass index and in-hospital mortality among critically ill cardiac surgery patients, with an optimistic risk threshold of 25kg/m2.

Evidence Rating Level: 2 (Good)

Cardiac surgery is associated with substantial perioperative mortality, with a greater risk among critically ill patients. Body mass index (BMI) is associated with chronic non-communicable diseases, including cardiovascular disease. However, there is a lack of research on the association between baseline BMI and in-hospital mortality following major cardiac surgery. This study thus examined the relationship between baseline BMI and in-hospital mortality among cardiac surgery patients admitted to intensive care units (ICU). This retrospective cohort study analyzed data from the eICU Collaborative Research Database, consisting of ICU records from 208 US hospitals from 2014-2015. Critically ill adult patients (≥ 18 years) who underwent cardiac surgery and were subsequently admitted to the ICU were included. The primary outcome was BMI within 24 hours of ICU admission. The primary outcome was 3-day mortality. Among the 8,032 patients included in the study (BMI: 29.6 ± 6.8 kg/m2), mortality occurred in 289 (3.6%). No relationship was found between BMI and mortality (OR = 0.99, 95% CI 0.97–1.01). The relationship between BMI and mortality was found to have a U-shaped pattern with inflection at 25.0 kg/m2. Each BMI unit increase below this threshold reduced mortality risk by 10% (OR = 0.90, 95% CI 0.83–0.96), while no association was observed above this point (OR = 1.01, 95% CI 0.98–1.03). Overall, this study found a U-shaped relationship between BMI and mortality among critically ill cardiac surgery patients, with an optimistic risk threshold of 25kg/m2. These findings may guide perioperative BMI management in this population. Future studies should confirm these results in other populations. 

Click here to read this study in European Journal of Medical Research

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