title: Hierarchy of regional oxygen delivery during cardiopulmonary bypass.
abstract: BACKGROUND
  Relative to the nonbypass state, cardiopulmonary bypass may decrease whole-body oxygen (O2) delivery. We predicted that during cardiopulmonary bypass, a hierarchy of regional blood flow and O2 delivery could be characterized.
  
  
  METHODS
  In 8 46.5 +/- 1.2-kg pigs, fluorescent microspheres were used to determine blood flow and O2 delivery to five organ beds before and during 37 degrees C cardiopulmonary bypass at four randomized bypass flows (1.4, 1.7, 2.0, and 2.3 L/min/m2). At completion, 18 tissue samples were obtained from the cerebral cortex (n = 4), renal cortex (n = 2), renal medulla (n = 2), pancreas (n = 3), small bowel (n = 3), and limb muscle (n = 4) for regional blood flow determination.
  
  
  RESULTS
  At conventional cardiopulmonary bypass flow (2.3 L/min/m2), whole-body O2 delivery was reduced by 44 +/- 6% relative to the pre-cardiopulmonary bypass state (p < 0.05). Over a range of cardiopulmonary bypass flows (2.3 to 1.7 L/min/m2), brain and kidney maintained their perfusion. Blood flow and O2 delivery to both regions were reduced when the cardiopulmonary bypass flow was reduced to 1.4 L/min/m2. However, perfusion and O2 delivery to other visceral organs (pancreas, small bowel) and skeletal muscle showed pump flow dependency over the range of flows tested.
  
  
  CONCLUSIONS
  This study characterizes the organ-specific hierarchy of blood flow and O2 distribution during cardiopulmonary bypass. These dynamics are relevant to clinical decisions for perfusion management.
authors.affiliation: Department of Surgery, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
authors.forename: U S
authors.initials: US
authors.lastname: Boston
authors.forename: J M
authors.initials: JM
authors.lastname: Slater
authors.forename: T A
authors.initials: TA
authors.lastname: Orszulak
authors.forename: D J
authors.initials: DJ
authors.lastname: Cook
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply; D002315:Cardiopulmonary Bypass; D007421:Intestine, Small / Q000098:blood supply; D007668:Kidney / Q000098:blood supply; D018482:Muscle, Skeletal / Q000098:blood supply; D010100:Oxygen / Q000378:metabolism*; D010179:Pancreas / Q000098:blood supply; D012039:Regional Blood Flow; D013552:Swine
chemical_list: D010100:Oxygen