Body mass index is negatively correlated with respiratory muscle weakness and interleukin-6 production after coronary artery bypass grafting

Abstract

Purpose The present study was performed to clarify the relationships between body mass index (BMI), interleukin-6 (IL-6) production, and respiratory muscle weakness in patients undergoing coronary artery bypass grafting (CABG). Materials and Methods The correlations among BMI, changes in maximum inspiratory and expiratory pressure (ΔMIP, ΔMEP) on postoperative days (POD) 1 and 7, postoperative IL-6, and rapid turnover proteins (retinol-binding protein, prealbumin, and transferrin) on POD1 were assessed in 154 consecutive patients undergoing elective CABG. The patients were divided into quartiles of BMI, Q1 (BMI, <20.8 kg/m 2) to Q4 (BMI, ≥25.25 kg/m 2), and compared among groups. Results There were significant correlations between ΔMIP and BMI (POD1, r = −0.369; POD7, r = −0.285) and IL-6 (POD1, r = 0.423; POD7, r = 0.431), and between ΔMEP and BMI (POD1, r = −0.252; POD7, r = −0.228) and IL-6 (POD1, r = 0.252; POD7, r = 0.384). Interleukin-6 showed a significant negative correlation with BMI ( r = −0.374) and retinol-binding protein ( r = −0.382). Interleukin-6 was highest in Q1 and lowest in Q4. Higher BMI indicated greater respiratory muscle strength than lower BMI. Conclusions Preoperative BMI is correlated with respiratory muscle strength and cytokine production after CABG. The findings of this study suggest that BMI may be a valuable predictor for respiratory management in CABG patients.