Should initial clamping for abdominal aortic aneurysm repair be proximal or distal to minimise embolisation?

Objectives: to determine whether clamping proximally or distally on the inf rarenal aorta during abdominal aortic aneurysm (AAA) repair increases the o verall embolic potential. Materials and methods: a sheath was placed in the mid-infrarenal aorta of 1 6 dogs. In eight animals a cross-clamp was placed at the aortic trifurcatio n, and in another eight animals it was placed in the immediate subrenal pos ition. under fluoroscopy blood pow within the infrarenal aorta was evaluate d by contrast and particle injections. Greyscale analysis was used to calcu late contrast density. Particle distribution was followed fluoroscopically and confirmed pathologically. Results: Fifty-seven +/- 24% of injected contrast remained within the aorta with distal clamping while 97 +/- 7% did so with proximal clamping (p<0.01 ). With distal aortic clamping 6.2 +/- 1.3 out of 10 injected particles rem ained within the aorta after 15 seconds and only 0.8 +/- 0.8 remained after 5 min. With proximal aortic clamping, all 10 of the particles remained wit hin the aortic lumen for the full 5 minutes (p<0.001). Conclusions: initial distal clamping minimises distal embolisation, but may result in renal and/or visceral embolisation. Initial proximal clamping pr events proximal embolisation and does not promote distal embolisation. We r ecommend initial proximal clamping in aortic aneurysm surgery to minimise t he overall risk of embolisation.