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 infrarenal aorta during abdominal aortic aneurysm (AAA) repair increases the overall embolic potential. Materials and methods: a sheath was placed in the mid-infrarenal aorta of 16 dogs. In eight animals a cross-clamp was placed at the aortic trifucation, and in another eight animals it was placed in the immediate subrenal position. Under flouroscopy blood flow within the infrarenal aorta was evaluated by contrast and particle injections. Greyscale analysis was used to calculate contrast density. Particle distribution was followed flouroscopically 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 remained 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 within 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 prevents proximal embolisation and does not promote distal embolisation. We recommend initial proximal clamping in aortic aneurysm surgery to minimise the overall risk of embolisation.