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Impact of body mass index on postoperative bleeding in cardiopulmonary bypass


Body mass index (BMI) has been described as a risk factor for coronary artery disease, but association with postoperative bleeding after cardiopulmonary bypass (CPB) has been found in several studies recently. Nevertheless the strong relationship between a low BMI and excessive bleeding remains unexplained. We sought to investigate the BMI role on postoperative bleeding and its relationship with leptin levels, coagulation, fibrinolysis and complement parameters.


We performed a nested case–control study of 26 patients, who did not receive antifibrinolytic prophylaxis. We used Bray's classification for BMI: lower than 27 kg/m2; 27–30 kg/m2; higher than 30 kg/m2. Variables were collected preoperatively, at ICU admission (0 hours), and at 4 and 24 hours after surgery. Excessive bleeding was defined as blood loss higher than 1 l in the first 24 hours after intervention. The associations of BMI with demographic factors, leptin levels, coagulation, fibrinolysis and complement parameters were analyzed. Pearson's chi-squared test and Fisher's exact test were used, the Student t test for independent groups and the Mann–Whitney U test for nonparametric variables.


In total, 61.5% of patients showed BMI >27 kg/m2 (median 28 kg/m2, range 25.2–30.7 kg/m2). Patients with BMI lower than 26.4 kg/m2 (25–28 kg/m2) presented excessive bleeding (P = 0.026). Leptin levels after adjusting by BMI were significantly associated with excessive bleeding at all postoperative time points (P < 0.001, P < 0.001 and P = 0.004, respectively) (Figure 1). BMI presented a direct correlation with leptins, fibrinogen and plasminogen activator inhibitor-1 (PAI-1) on arrival, meanwhile 24-hour bleeding showed an inverse correlation with the same parameters and BMI (Table 1). Patients with BMI < 27 kg/m2 had significantly greater coagulation, fibrinolysis and complement activation. Therefore these patients required significantly greater hemoderivatives.

Figure 1

abstract P5

Table 1 abstract P257)


Lower BMI was associated with higher postoperative bleeding and lower procoagulant factor levels.

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Brouard, M., Jimenez, J., Iribarren, J. et al. Impact of body mass index on postoperative bleeding in cardiopulmonary bypass. Crit Care 11, P257 (2007).

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  • Body Mass Index
  • Fibrinogen
  • Plasminogen
  • Cardiopulmonary Bypass
  • Postoperative Bleeding