title: Arterio-venous gradients of free energy change for assessment of systemic and splanchnic perfusion in cardiac surgery patients.
abstract: OBJECTIVE
  Adequacy of organ perfusion depends on sufficient oxygen supply in relation to the metabolic needs. The aim of this study was to evaluate the relationship between gradients of free energy change, and the more commonly used parameter for the evaluation of the adequacy of organ perfusion, such as oxygen-extraction in patients undergoing valve replacement surgery using normothermic cardiopulmonary bypass (CPB).
  
  
  METHODS
  In 43 cardiac patients, arterial, mixed venous, and hepato-venous blood samples were taken synchronously after induction of anaesthesia (preCPB), during CPB, and 2 and 7 h after admission to the intensive care unit (ICU+2, ICU+7). Blood gas analysis, cardiac output, and hepato-splanchnic blood flow were measured. Free energy change gradients between mixed venous and arterial (-deltadeltaG(v - a)) and hepato-venous and arterial (-deltadeltaG(hv - a)) compartments were calculated.
  
  
  RESULTS
  Cardiac index (CI) increased from 1.9 (0.7) to 2.8 (1.3) L/min/m (median, inter-quartile range) (p = 0.001), and hepato-splanchnic blood flow index (HBFI) from 0.6 (0.22) to 0.8 (0.53) L/min/m (p = 0.001). Despite increasing flow, systemic oxygen extraction increased after CPB from 24 (10)% to 35 (10)% at ICU+2 (p = 0.002), and splanchnic oxygen extraction increased during CPB from 37 (19)% to 52 (14)% (p = 0.001), and remained high thereafter. After CPB, high splanchnic and systemic gradients of free energy change gradients were associated with high splanchnic and systemic oxygen extraction, respectively (p = 0.001, 0.033, respectively).
  
  
  CONCLUSIONS
  Gradients of free energy change may be helpful in characterising adequacy of perfusion in cardiac surgery patients independently from measurements or calculations of data from oxygen transport.
authors.affiliation: Department of Anaesthesiology and Intensive Care, Charité-Universitätsmedizin Berlin, Berlin, Germany. jan.braun@charite.de
authors.forename: Jan-Peter
authors.initials: JP
authors.lastname: Braun
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Jakob
authors.forename: Thomas
authors.initials: T
authors.lastname: Volk
authors.forename: Ulrich R
authors.initials: UR
authors.lastname: Doepfmer
authors.forename: Maryam
authors.initials: M
authors.lastname: Moshirzadeh
authors.forename: Shirin
authors.initials: S
authors.lastname: Stegmann
authors.forename: Pascal M
authors.initials: PM
authors.lastname: Dohmen
authors.forename: Claudia
authors.initials: C
authors.lastname: Spies
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001158:Arteries / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output; D002315:Cardiopulmonary Bypass; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008102:Liver Circulation; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010100:Oxygen / Q000097:blood; D011446:Prospective Studies; D013152:Splanchnic Circulation; D014680:Veins / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D019344:Lactic Acid; D010100:Oxygen