Effect of Carbon dioxide on structural and functional viability of human
saphenous vein endothelium -- Role of calcium mobilisation and nitric
oxide production
Abstract
Objective Carbon dioxide (CO2) is used by many endoscopic vein
harvesting systems to facilitate visualisation and dissection by
creating a subcutaneous tunnel. We aim to investigate the potential
detrimental effect of CO2 insufflation, on endothelial structural and
functional viability of human saphenous vein (HSV). Method We performed
an ex vivo experiment on HSV segments (n = 40) by applying CO2 for 40
minutes at 6 – 12 mmhg in a specially designed chamber and compared it
with controls (n = 40). We have investigated the level of endothelial
damage by Calcein/Propidium iodide (PI) Live/Dead assay. Functional
viability of HSV was assessed by Ca2+ (FLUO3 AM) and nitric oxide
(DAF-FM) specific indicators for calcium mobilisation and endothelial
nitric oxide synthase related nitric oxide (NO) production. Results CO2
did not cause any immediate structural endothelial damage and there was
no statistical difference between control and CO2 groups (Calcein p =
0.27 and PI p = 0.98). After CO2 exposure and bradykinin stimulation,
Ca2+ mobilisation was significantly attenuated (p = 0.013) and NO
generation was also markedly reduced in endothelial cells, without
reaching statistical significance (p = 0.078). Conclusion We believe
these results are purely due to CO2 insufflation, which can compromise
the entire length of vein graft. However, more research is required to
establish, whether these findings are transient in nature or they have
long term implications on graft survival and clinical outcome.