title: Increased intrathoracic pressure affects cerebral oxygenation following cardiac surgery.
abstract: BACKGROUND
  Cerebral oximetry reflects circulatory stability during surgery. We evaluated whether frontal lobe oxygenation is influenced by a transient increase in intrathoracic pressure as induced by a lung recruitment manoeuvre.
  
  
  METHODS
  Intrathoracic pressure was increased to 40 cm H(2)O for 20 s immediately after cardiac surgery in ten patients (age 64 ± 10 year, mean ± SD) with frontal lobe oxygenation assessed by near-infrared spectroscopy and cardiac output by thermodilution.
  
  
  RESULTS
  The lung recruitment manoeuvre increased arterial O(2) pressure (from 29 ± 15 to 40 ± 12 kPa) with a decrease in mean arterial pressure (MAP) (from 69 ± 7 to 55 ± 11 mmHg), cardiac output (from 5·4 ± 0·6 to 5·0 ± 0·7 l min(-1)) and frontal lobe oxygenation (from 68 ± 9 to 60 ± 13%; all P<0·05). A reduction in MAP by more than 15 mmHg caused cerebral desaturation by 10%, the lowest cerebral oxygenation (44%) was with a reduction in MAP by 24 mmHg, and according to multiple linear regression, only MAP predicted cerebral deoxygenation (P = 0·03). Following the lung recruitment manoeuvre, hemodynamic variables and frontal lobe oxygenation were restored.
  
  
  CONCLUSIONS
  A lung recruitment manoeuvre decreases frontal lobe oxygenation when MAP is low suggesting that with increased intrathoracic pressure, arterial pressure should be kept within the limits of cerebral autoregulation.
authors.affiliation: Department of Anaesthesia, Hvidovre Hospital, Hvidovre, Denmark. larsmoellerp@gmail.com
authors.forename: Lars M
authors.initials: LM
authors.lastname: Pedersen
authors.forename: Jonas
authors.initials: J
authors.lastname: Nielsen
authors.forename: Morten
authors.initials: M
authors.lastname: Østergaard
authors.forename: Eigil
authors.initials: E
authors.lastname: Nygård
authors.forename: Henning B
authors.initials: HB
authors.lastname: Nielsen
mesh_terms: D000368:Aged; D062186:Arterial Pressure; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects; D002560:Cerebrovascular Circulation; D003718:Denmark; D005625:Frontal Lobe / Q000098:blood supply*; D006706:Homeostasis; D006801:Humans; D007022:Hypotension / Q000097:blood / Q000209:etiology / Q000503:physiopathology*; D016014:Linear Models; D008168:Lung / Q000503:physiopathology*; D008875:Middle Aged; D015999:Multivariate Analysis; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000097:blood*; D012143:Respiratory Physiological Phenomena; D019265:Spectroscopy, Near-Infrared; D013815:Thermodilution; D035423:Thoracic Cavity; D013997:Time Factors
chemical_list: D010100:Oxygen