Impact of distal aortic perfusion on 'segmental steal' depleting spinal cord blood flow-a quantitative experimental approach.

OBJECTIVES: Aortic steal is an underestimated risk factor for intraoperative spinal cord ischaemia. A negative effect on spinal cord perfusion in thoraco-abdominal aneurysm repair has been suspected if blood drains away from the cord initiated by a reversal of the arterial pressure gradient. The amount of blood and pressure loss via back-bleeding of segmental arteries and the impact of distal aortic perfusion (DaP) have not been analysed yet. The aim of our study was to quantify 'segmental steal' in vivo during simulated thoraco-abdominal aneurysm repair and to determine the impact of DaP on steal and spinal cord perfusion.

METHODS: Ten juvenile pigs were put on cardiopulmonary bypass with DaP and visceral arteries were ligated. 'Segmental steal' was quantified by draining against gravity with/without DaP. Blood volume of 'segmental steal' was quantified and microspheres were injected for Post mortem spinal cord perfusion analysis. 'Segmental steal' was quantified with/without DaP-and with stopped DaP.

RESULTS: Quantification revealed a significantly higher steal on cardiopulmonary bypass with DaP with a mean difference of 24(11) ml/min. In all spinal cord segments, blood flow was diminished during steal drainage on DaP, compared to 'no steal'. The least perfused region was the low thoracic to upper lumbar segment.

CONCLUSIONS: 'Segmental steal' is a relevant threat to spinal cord perfusion-even with the utilization of DaP-diminishing spinal cord perfusion. The blood volume lost by back-bleeding of segmental arteries is not to be underestimated and occlusion of segmental arteries should be considered in thoraco-abdominal aneurysm repair.