title: Impact of closed minimal extracorporeal circulation on microvascular tissue perfusion during surgical aortic valve replacement: intravital imaging in a prospective randomized study.
abstract: OBJECTIVE
  Closed minimal extracorporeal circulation (MECC) systems currently do not represent the standard of surgical care for open-heart surgery. Yet, considering the beneficial results reported for coronary artery bypass graft (CABG) surgery, we used an MECC system in aortic valve replacement (AVR) and analysed the effects on intraoperative microvascular perfusion in comparison with conventional open extracorporeal circulation (CECC).
  
  
  METHODS
  In the current study, we analysed alterations in microvascular perfusion at 4 predefined time points (T1-T4) during surgical AVR utilizing orthogonal polarization spectral (OPS) imaging. Twenty patients were randomized for being operated on utilizing either MECC or CECC. Changes in functional capillary density (FCD, cm/cm(2)), mircovascular blood flow velocity (mm/s) and vessel diameter (μm) were analysed by a blinded investigator.
  
  
  RESULTS
  After the start of extracorporeal circulation and aortic cross-clamping (T2), both groups showed a significant drop in FCD, but with a significantly higher FCD in the MECC group (153.1 ± 15.0 cm/cm² in the CECC group vs 160.8 ± 12.2 cm/cm² in the MECC group, P = 0.034). During the late phase of the cardiopulmonary bypass (CPB) (T3), the FCD was still significantly depressed in both treatment groups (153.5 ± 14.6 cm/cm² in the CECC group, P <0.05 vs 'T1'; 159.5 ± 12.4 cm/cm² in the MECC group, P <0.05 versus 'T1'). After termination of CPB (T4), the FCD recovered in both groups to baseline values. Microvascular blood flow velocity tended to remain at a higher level in the MECC group, whereas haemodilution during CPB was significantly reduced in the MECC group.
  
  
  CONCLUSIONS
  The use of MECC in AVR did not affect procedural safety and, resulted in beneficial preservation of microvascular blood flow velocity and significantly reduced haemodilution during CPB. In contrast to CABG surgery, the use of MECC did not improve FCD during surgical AVR. Clinical advantages possibly resulting from attenuated haemodilution and preservation of microvascular blood flow velocity require further validation in larger patient cohorts.
authors.affiliation: Department of Cardiac Surgery, University of Rostock, Rostock, Germany peter.donndorf@med.uni-rostock.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Donndorf
authors.affiliation: Department of Cardiac Surgery, University of Rostock, Rostock, Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Park
authors.affiliation: Institute of Experimental Surgery, University of Rostock, Rostock, Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Vollmar
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University of Rostock, Rostock, Germany.
authors.forename: Angela
authors.initials: A
authors.lastname: Alms
authors.affiliation: Department of Trauma and Reconstructive Surgery, University of Rostock, Rostock, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Gierer
authors.affiliation: Department of Cardiac Surgery, University of Rostock, Rostock, Germany.
authors.forename: Gustav
authors.initials: G
authors.lastname: Steinhoff
authors.affiliation: Department of Cardiac Surgery, University of Rostock, Rostock, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kaminski
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000503:physiopathology / Q000601:surgery*; D001022:Aortic Valve Insufficiency / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D001024:Aortic Valve Stenosis / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D001783:Blood Flow Velocity; D002315:Cardiopulmonary Bypass; D015199:Extracorporeal Membrane Oxygenation / Q000009:adverse effects; D005260:Female; D005858:Germany; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects; D006438:Hemodilution; D006801:Humans; D008297:Male; D008833:Microcirculation; D008859:Microscopy, Polarization; D018715:Microscopy, Video; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009061:Mouth Mucosa / Q000098:blood supply*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012039:Regional Blood Flow; D013997:Time Factors; D016896:Treatment Outcome
keywords: Aortic valve replacement; Haemodilution; Microcirculation; Minimal extracorporeal circulation