title: Positive end-expiratory pressure does not affect indocyanine green plasma disappearance rate or gastric mucosal perfusion after cardiac surgery.
abstract: OBJECTIVE
  Positive end-expiratory pressure (PEEP) may affect hepato-splanchnic blood flow. We studied whether a PEEP of 10 mbar may negatively influence flow-dependent liver function (indocyanine green plasma disappearance rate, ICG-PDR) and splanchnic microcirculation as estimated by gastric mucosal PCO2 (PRCO2).
  
  
  METHODS
  In a randomized, controlled clinical study, we enrolled 28 patients after elective cardiac surgery using cardiopulmonary bypass. In 14 patients (13 male, 1 female; age 48-74, mean 63 +/- 7 yr) we assessed ICG-PDR and PRCO2 on intensive care unit admission with PEEP 5 mbar, after 2 h with PEEP of 10 mbar and again after 2 h at PEEP 5 mbar. Inspiratory peak pressure was adjusted to maintain normocapnia. Fourteen other patients (8 male, 6 female; age 46-86, mean 68 +/- 11 yr) in whom PEEP was 5 mbar throughout served as controls. All patients underwent haemodynamic monitoring by measurement of central venous pressure, left atrial pressure and cardiac index using pulmonary artery thermodilution.
  
  
  RESULTS
  While doses of vasoactive drugs and cardiac filling pressures did not change significantly, cardiac index slightly increased in both groups. ICG-PDR remained unchanged either within or between both groups (PEEP10 group: 24.0 +/- 6.9, 22.0 +/- 7.9 and 25.5 +/- 7.7% min-1 vs. controls: 22.0 +/- 7.5, 23.8 +/- 8.4 and 21.4 +/- 6.5% min-1) (P = 0.05). The difference between PRCO2 and end-tidal PCO2 (PCO2-gap) did not change significantly (PEEP10 group: 1.1 +/- 0.9, 1.3 +/- 0.7 and 1.3 +/- 0.9 kPa vs. controls: 0.8 +/- 0.5, 0.9 +/- 0.5 and 0.9 +/- 0.5 kPa).
  
  
  CONCLUSIONS
  A PEEP of 10 mbar for 2 h does not compromise liver function and gastric mucosal perfusion in patients after cardiac surgery with maintained cardiac output.
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, Friedrich-Schiller-University of Jena, Erlanger Allee 101, D-07747 Jena, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Holland
authors.forename: O
authors.initials: O
authors.lastname: Thuemer
authors.forename: C
authors.initials: C
authors.lastname: Schelenz
authors.forename: N
authors.initials: N
authors.lastname: van Hout
authors.forename: S G
authors.initials: SG
authors.lastname: Sakka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology; D006348:Cardiac Surgical Procedures / Q000379:methods*; D002315:Cardiopulmonary Bypass / Q000379:methods; D004396:Coloring Agents / Q000493:pharmacokinetics; D017558:Elective Surgical Procedures / Q000379:methods; D005260:Female; D005753:Gastric Mucosa / Q000098:blood supply*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007208:Indocyanine Green / Q000493:pharmacokinetics; D008099:Liver / Q000098:blood supply; D008111:Liver Function Tests / Q000379:methods; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D013152:Splanchnic Circulation / Q000502:physiology*; D013815:Thermodilution / Q000379:methods; D013997:Time Factors
chemical_list: D004396:Coloring Agents; D007208:Indocyanine Green