Background and goal: Microcirculatory perfusion is impaired during and after cardiac surgery with cardiopulmonary bypass (CPB). A substantial part of the cardiac surgical population is obese and it is known that obese patients have impaired microcirculatory function. It is however not known how CPB affects microcirculatory perfusion in this obese group, and we hypothesized that CPB-induced alterations are more severe in obese patients. 

Materials and methods: Obese (BMI>35kg/m2) and lean (BMI 20-25kg/m2) patients without diabetes undergoing cardiac surgery with CPB were included (n=9 vs. 16 respectively). Sublingual microcirculatory perfusion was determined with Sidestream Darkfield Imaging at baseline (T=0), after induction of anesthesia (T=1), after start of CPB (T=2), after weaning from CPB (T=3) and 24 hours after surgery (T=4). 

Results and discussion:  Microcirculatory perfusion did not differ between groups at baseline (T=0) nor did induction of anesthesia (T=1) alter perfusion in either group. In obese patients, the start of CPB (T=2) decreased the proportion of perfused vessels (PPV: 6% decrease, p=0.05) as well as the microvascular flow index (MFI: 12% decrease, p=0.03). Interestingly, in the lean group these changes did not occur until weaning from CPB (T=3) (PPV 8% decrease, p=0.03; MFI 9% decrease, p=0.01). Twenty-four hours after surgery (T=4), microcirculatory perfusion was restored to baseline values in both groups. 

Conclusion: These pilot data show that cardiopulmonary bypass-induced changes in microcirculatory perfusion occur earlier in obese patients when compared to lean patients. This suggests that obese patients may be less able to compensate for hemodynamic and endothelial stress caused by CPB. Future research will focus on how this is related to the development of postoperative complications. 


08 / Microcirculatory perfusion in obese patients undergoing cardiac surgery with cardiopulmonary bypass