In coronary artery bypass graft (CABG) surgery, minimal extracorporeal circulation (MECC) was introduced, providing clinical improvements due to reduced hemodilution and the absence of a blood–air interface. Yet, compared to conventional extracorporeal circulation (CECC), the effects of MECC on intraoperative microvascular perfusion have not been explored. A study used orthogonal polarisation spectral imaging to look at changes in microvascular perfusion during on-pump CABG at four different time points (T1-T4). A total of 40 patients were randomized to receive MECC or CECC surgery. A blinded investigator looked at functional capillary density (FCD), blood flow velocity, and channel diameter changes. Following the initiation of extracorporeal circulation (ECC) and aortic cross-clamping (T2), both groups showed a significant decrease in FCD, with the MECC group having a considerably higher FCD (206.8 ± 33.6 cm/cm2 in CECC versus 217.8 ± 35.3 cm/cm2 in MECC; P=.034). FCD in the MECC group had recovered by the end of the ECC (T3), however, FCD in the CECC group was still considerably depressed (223.1 ± 35.6 cm/cm2 in MECC group; P=.100 vs T1; 211.1 ± 36.9 cm/cm2 in CECC group; P=.017 vs T1). FCD returned to baseline in both groups once ECC (T4) was stopped. After aortic cross-clamping, blood flow velocity tended to be higher in the MECC group, with a significant intergroup difference (T2).
According to orthogonal polarisation spectral imaging data, microvascular perfusion is impaired during on-pump CABG. During the reperfusion period, changes in FCD imply a faster recovery of microvascular perfusion in MECC. The perioperative benefits found for MECC could be partly explained by the beneficial recovery of microvascular organ perfusion.