Laser Doppler flowmetry in evaluation of colonic blood flow during aortic reconstruction

Intraoperative laser Doppler flowmetry (LDF) was used to measure blood perfusion in terminal ileum and sigmoid colon in eight patients operated on for aorto-iliac occlusive disease (AIO) and eight patients for abdominal aortic aneurysm (AAA). The aim of the study was to evaluate the influence of clamping the inferior mesenteric artery (IMA) on intestinal perfusion. LDF-measured sigmoid colon flow was also compared with the postoperative clinical course, to define a limit below which risk of ischaemic colitis is high and revascularisation should be considered. Neither clamping of the IMA nor aortic reconstruction affected perfusion in the terminal ileum in any group. Sigmoid colon perfusion in the AAA-group showed a slight, not significant reduction after reconstruction (P = 0.09). AIO patients showed significant flow reduction in the sigmoid colon when the IMA was clamped (P less than 0.05), returning to the initial value after aortic reconstruction with end-to-side proximal anastomosis and preservation of IMA. AAA patients, operated with end-to-end proximal anastomosis and ligation of IMA, had significantly lower sigmoid colon perfusion after aortic reconstruction than AIO patients (P less than 0.05). Thirteen patients had sigmoid colon flux values greater than 5 RFU (Relative Flux Units) after reconstruction, and had no complications. Three aneurysm patients had flux values less than 3.3 RFU, and developed symptoms of ischaemic colitis. We conclude that LDF can be easily applied to the evaluation of colonic blood flow during aortic surgery. Flux values less than 4 RFU may indicate a risk of ischaemic colitis, and justify revascularisation of the colon.