title: Hemodynamic effects of short-term hyperoxia after coronary artery bypass grafting.
abstract: BACKGROUND
  Although oxygen is generally administered in a liberal manner in the perioperative setting, the effects of oxygen administration on dynamic cardiovascular parameters, filling status and cerebral perfusion have not been fully unraveled. Our aim was to study the acute hemodynamic and microcirculatory changes before, during and after arterial hyperoxia in mechanically ventilated patients after coronary artery bypass grafting (CABG) surgery.
  
  
  METHODS
  This was a single-center physiological study in a tertiary care ICU in the Netherlands. Twenty-two patients scheduled for ICU admission after elective CABG were enrolled in the study between September 2014 and September 2015. In the ICU, patients were exposed to a fraction of inspired oxygen (FiO2) of 90% allowing a 15-min wash-in period. Various hemodynamic parameters were measured using direct pressure signals and continuous arterial waveform analysis at three sequential time points: before, during and after hyperoxia.
  
  
  RESULTS
  During a 15-min exposure to a fraction of inspired oxygen (FiO2) of 90%, the partial pressure of arterial oxygen (PaO2) and arterial oxygen saturation (SaO2) were significantly higher. The systemic resistance increased (P < 0.0001), without altering the heart rate. Stroke volume variation and pulse pressure variation decreased slightly. The cardiac output did not significantly decrease (P = 0.08). Mean systemic filling pressure and arterial critical closing pressure increased (P < 0.01whereas the percentage of perfused microcirculatory vessels decreased (P < 0.01). Other microcirculatory parameters and cerebral blood flow velocity showed only slight changes.
  
  
  CONCLUSIONS
  We found that short-term hyperoxia affects hemodynamics in ICU patients after CABG. This was translated in several changes in central circulatory variables, but had only slight effects on cardiac output, cerebral blood flow and the microcirculation. Clinical trial registration Netherlands Trial Register: NTR5064.
authors.affiliation: Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands. H.J.F.Helmerhorst@lumc.nl.|Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands. H.J.F.Helmerhorst@lumc.nl.|Laboratory of Experimental Intensive Care and Anesthesiology, Academic Medical Center, Amsterdam, The Netherlands. H.J.F.Helmerhorst@lumc.nl.
authors.forename: Hendrik J F
authors.initials: HJF
authors.lastname: Helmerhorst
authors.affiliation: Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands.
authors.forename: Rob B P
authors.initials: RBP
authors.lastname: de Wilde
authors.affiliation: Department of Nephrology, Einthoven Laboratory for Vascular Medicine, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Dae Hyun
authors.initials: DH
authors.lastname: Lee
authors.affiliation: Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Meindert
authors.initials: M
authors.lastname: Palmen
authors.affiliation: Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands.
authors.forename: Jos R C
authors.initials: JRC
authors.lastname: Jansen
authors.affiliation: Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands.
authors.forename: David J
authors.initials: DJ
authors.lastname: van Westerloo
authors.affiliation: Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands.
authors.forename: Evert
authors.initials: E
authors.lastname: de Jonge
keywords: Arterial oxygenation; Cerebral blood flow velocity; Hemodynamics; Hyperoxia; Intensive care unit; Microcirculation; Thoracic surgery