Doppler ultrasonographic identification of the critical segmental artery for spinal cord protection

Objective: The purpose of this study is to evaluate the possibility of iden tifying critical segmental arteries (CSAs) based on Doppler ultrasonographi c hemodynamics. Methods: In 18 mongrel dogs, the descending aorta was scann ed directly with a 5-MHz linear probe through left thoracotomies and the fl ow velocities in segmental arteries were measured by pulsed Doppler. The ao rta was cross-clamped between Th13 and L1, and flow velocity changes were r ecorded. According to flow increases, segmental arteries were divided into three groups: arteries with the largest flow increase (L-arteries), arterie s with the smallest increase (S-arteries) and other arteries (O-arteries). Animals were divided into three groups. One aortic segment including an L-a rtery or an S-artery was perfused via a temporary shunt during 30-min aorti c cross-clamping distal to the left subclavian artery (Group L or Group S) and neurological outcomes were compared with those of animals without shunt ing (Group N) after 24 and 48 h. Results: L-arteries had significantly larg er flow increases than S- and O-arteries (74.3 +/- 33.8, 20.4 +/-9.8 and 33 .3 +/- 17.8 cm/s, P<0.01). In Group N, five of the six animals were complet ely paraplegic (Tarlov Grade 0) and the other was Grade 1. In Group S, four animals were Grade 4 and two were Grade 0 after 24 h. However, two animals showed delayed paraplegia. Therefore, four animals were Grade 0 and two we re Grade 4 after 48 h. All animals in Group L were neurologically normal (G rade 4) at both after 24 h (vs. Group N, P=0.0013) and 48 h (vs. Group N, P =0.0013; vs. Group S, P=0.019). Conclusions: Flow responses to aortic cross -clamping differed among segmental arteries and selective perfusion of L-ar teries completely prevented paraplegia. Therefore, L-arteries were consider ed to be CSAs. Hemodynamic measurement of segmental arterial flow using Dop pler ultrasonography could be clinically useful for spinal cord protection during thoracoabdominal aortic surgery. (C) 2001 Elsevier Science B.V. All rights reserved.