Impact of distal aortic perfusion on ‘segmental steal’ depleting spinal cord blood flow—a quantitative experimental approach

Abstract

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.

Minimally invasive staged segmental artery coil embolization (MIS2ACE) for spinal cord protection

“…One underestimated advantageous side-effect of MIS 2 ACE is the reduction of back-bleeding. Segmental back-bleeding after opening of the aneurysm can worsen the overview of the operative field, and therefore back-bleeding can be a severe threat to the spinal cord as shown by an experimental study of our group ( 18 ). In endovascular repair, previous MIS 2 ACE can reduce the incidence of type II endoleaks.…”

Collateral network concept in 2023

“…It is paramount to measure both upper body and lower body arterial pressure during TAAA repair. The MAP needs to be maintained on the high side (>90 mmHg) especially during sacrifice of the SAs and after completion of repair (2,(6)(7)(8)39,47,49). This can be also achieved by increasing cardiopulmonary bypass flow through the femoral artery to increase a distal aortic perfusion pressure to the lower SAs (49).…”

“…The MAP needs to be maintained on the high side (>90 mmHg) especially during sacrifice of the SAs and after completion of repair (2,(6)(7)(8)39,47,49). This can be also achieved by increasing cardiopulmonary bypass flow through the femoral artery to increase a distal aortic perfusion pressure to the lower SAs (49). Care should be taken to maintain pulsatile flow of the upper body during partial cardiopulmonary bypass of the lower body as pulsatile flow provides more blood flow to the spinal cord, as demonstrated by Etz et al (39).…”

“…A University of Texas group reported their experience of TAAA repair using the adjunct of distal aortic perfusion (increasing CNP) and CSF drainage (lowering CSF pressure), providing a low incidence of SCI ( 15 ). Recently, Haunschild and colleagues showed the significance of steal phenomenon even during distal aortic perfusion ( 49 ). In this report, distal aortic perfusion with blood flow steal from the SAs resulted in decrease in perfusion in the spinal cord regional flow, especially in the lower thoracic and upper lumbar levels (Th8-L2).…”

“…Neuromonitoring such as MEP and/or SSEP is frequently used to detect early SCI during the procedure ( 4 , 23 , 37 , 42 ). Once SCI is suspected on MEPs or SSEPs after clamping SAs, the target MAP can be increased and measurement of MEP is repeated in 1 to 5 minutes to observe recovery of evoked potentials ( 13 , 14 , 43 , 47 , 49 ). Dr. Etz’s group from Leipzig introduced the efficacy of collateral network near-infrared spectroscopy (NIRS) ( 17 , 27 ) as non-invasive, real-time monitoring of spinal cord oxygenation which can be used during surgical repair and postoperatively.…”