Spinal cord ischemia after selective cerebral perfusion in a porcine "frozen elephant trunk" simulation model

The "frozen elephant trunk" procedure (FET) represents the therapy of choice for extended aortic diseases. The aim of our study was to analyze whether 90 minutes of selective cerebral perfusion (SCP) at 28 °C followed by permanent occlusion of the thoracic segmental arteries (TSA) would cause spinal cord ischemia in a porcine model.

14 pigs (41 ± 3 kg) were cooled on CPB to 28 °C. After aortic clamping, SCP was established for 90 minutes. Randomly, in 7 animals the TSA were clipped (T4-T13); the TSA of 7 animals remained untouched. After the animals were weaned from CPB, hemodynamic data were registered for 120 minutes. Regional spinal cord blood flow (SCBF) was calculated, and motor-evoked potentials (MEP) were assessed at 6 time points. After sacrifice of the animals, the spinal cord was analyzed histologically by use of a schematic grading system (0 = normal; 8 = total necrosis).

During SCP the SCBF was maintained at baseline (5.9 ± 2.4 mL/min/100 g) in the T4-T13 region but showed a decrease (from 8.4 ± 4.3 to 1.3 ± 1.5 mL/min/100 g) in the L1-L5 region. During reperfusion it increased, with two to three times higher values in the nonclipped animals. After 90 minutes of SCP, the MEP reached lower levels in the L1-L5 region of the TSA-clipped animals: 59% ± 7% vs 84 ± 15% (vastus medialis muscle) and 48% ± 6% vs 82% ± 26% (tibialis anterior muscle). The MEP recovered only in the nonclipped group. Higher ischemia rates were seen in the L1-L5 region of the TSA-clipped animals (score: 6.0 ± 0.6 vs 2.5 ± 2.3).

90 minutes of SCP provided sufficient spinal cord protection during arch replacement at 28 °C. In combination with permanent TSA occlusion, the lumbar spinal cord perfusion may be altered, which causes functional and structural damage.