title: Low-flow lower body perfusion for spinal protection in a frozen elephant trunk simulation model.
abstract: OBJECTIVE
  The frozen elephant trunk (FET) procedure using isolated selective cerebral perfusion (SCP) at moderate hypothermia is associated with an increased risk for spinal cord ischaemia. The aim of this study was to evaluate the benefit of a combined selective cerebral and low-flow lower body perfusion (CLBP) in a porcine model.
  
  
  METHODS
  Twenty pigs (46 ± 5 kg) were cooled on cardiopulmonary bypass (CPB) to 28°C. After aortic clamping and occlusion of the thoracic segmental arteries (TSAT4-T13), a pressure-controlled SCP (50 mmHg) was established for 90 min. Randomly, in n = 10 animals, an additional lower body perfusion (LBP) was performed with 15 ml/kg/min (CLBP). Regional spinal cord blood flow (SCBF), cerebrospinal fluid pressure (CSFP) and motor-evoked potentials (MEPs) were registered at six time points. The animals were sacrificed after 120 min of weaning from CPB, and the spinal cord was analysed histologically using a schematic scoring system (0 = normal, 8 = total necrosis).
  
  
  RESULTS
  Isolated SCP led to an SCBF decrease from 18.5 ± 9.4 to 0.9 ± 1.4 ml/min/100 g in the L1-L5 region (P = 0.005). CLBP preserved an almost physiological lumbar SCBF of 11.3 ± 5.3 ml/min/100 g. CSFP decreased in both groups during cooling and SCP/CLBP to 70-80% and increased during reperfusion to 150%, without showing significant differences between groups. The MEP amplitude decreased in both groups, with certain regional differences: T7-T11. MEP recording revealed a more pronounced amplitude decrease in the CLBP group (52.5 ± 2.0 vs 71.3 ± 0.9%), but MEP amplitudes recovered in both groups (SCP: 73.7 ± 0.5 vs CLBP: 82.6 ± 0.1%). During selective hypothermic perfusion, SCP-treated animals showed significant lower MEP amplitudes, when compared with CLBP-treated animals: 60 ± 9 vs 90 ± 3% (P < 0.001). After weaning, CLBP animals showed a better MEP recovery, especially in the L1-L5 region (99 ± 7 vs 70 ± 13%; P < 0.001). The histological analysis did not show significant differences in the necrosis extension in the thoracic spinal cord. A different situation was seen in the L1-L5 area: all animals with isolated SCP, but only 50% of the CLBP animals presented a score of >5. A higher grade of lumbar ischaemia could be seen after isolated SCP (score: 5.9 ± 0.6 vs 3.6 ± 2.9).
  
  
  CONCLUSIONS
  The prolonged SCP provides an insufficient lumbar spinal cord protection during the FET procedure at 28°C. The use of a low-flow LBP in addition to SCP may reduce functional and structural spinal damage.
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Bergmannsheil, Ruhr-University of Bochum, Bochum, Germany peter.haldenwang@bergmannsheil.de.
authors.forename: Peter Lukas
authors.initials: PL
authors.lastname: Haldenwang
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Bergmannsheil, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Lorine
authors.initials: L
authors.lastname: Häuser
authors.affiliation: Department of Neuroanatomy and Molecular Brain Research, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Nora
authors.initials: N
authors.lastname: Prochnow
authors.affiliation: Department of Neuroanatomy and Molecular Brain Research, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Damian
authors.initials: D
authors.lastname: Ziebura
authors.affiliation: Department of Anesthesiology, University Hospital Bergmannsheil, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Baumann
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Bergmannsheil, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Sikole
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Bergmannsheil, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Schlömicher
authors.affiliation: Institute for Pathology, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Inge
authors.initials: I
authors.lastname: Schmitz
authors.affiliation: Institute for Medical Statistics, Informatics and Epidemiology, University of Cologne, Köln, Germany.
authors.forename: Hildegard
authors.initials: H
authors.lastname: Christ
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Bergmannsheil, Ruhr-University of Bochum, Bochum, Germany.
authors.forename: Justus Thomas
authors.initials: JT
authors.lastname: Strauch
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000601:surgery*; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000379:methods*; D002315:Cardiopulmonary Bypass / Q000379:methods; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology; D004195:Disease Models, Animal; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007036:Hypothermia, Induced / Q000379:methods; D007430:Intraoperative Care / Q000379:methods; D019344:Lactic Acid / Q000097:blood; D008159:Lumbar Vertebrae; D009336:Necrosis; D010477:Perfusion / Q000379:methods; D011897:Random Allocation; D012039:Regional Blood Flow; D013116:Spinal Cord / Q000098:blood supply / Q000473:pathology; D020760:Spinal Cord Ischemia / Q000209:etiology / Q000517:prevention & control*; D034421:Sus scrofa; D013904:Thoracic Vertebrae
chemical_list: D019344:Lactic Acid
keywords: Aortic arch; Circulatory arrest; Frozen elephant trunk; Moderate hypothermia; Spinal protection