title: Low-flow cardiopulmonary bypass: importance of blood pressure in maintaining cerebral blood flow.
abstract: BACKGROUND
  During cardiopulmonary bypass (CPB), global hypoperfusion of the brain has been shown to result in ischemic insult and subsequent neurologic injury.
  
  
  METHODS
  We measured cerebral blood flow during independent manipulations of arterial blood pressure and pump flow rate to determine which of these hemodynamic parameters regulates cerebral perfusion during CPB. Seven adolescent baboons were placed on CPB and cooled to 28 degrees C. Pump flow rate and arterial blood pressure were altered in varied sequence to each of four conditions: (1) full flow (2.23 +/- 0.06 L.min-1.m-2, mean +/- standard deviation) at high pressure (61 +/- 2 mm Hg), (2) full flow (2.23 +/- 0.06 L.min-1.m-2) at low pressure (24 +/- 3 mm Hg), (3) low flow (0.75 L.min-1.m-2) at high pressure (62 +/- 2 mm Hg), and (4) low flow (0.75 L.min-1.m-2) at low pressure (23 +/- 3 mm Hg). During each of these hemodynamic conditions cerebral blood flow was measured by washout of intracarotid xenon 133.
  
  
  RESULTS
  Cerebral blood flow was greater at high blood pressure than at low pressure during CPB both at low flow (34 +/- 8.3 versus 14.1 +/- 3.7 mL.min-1.100 g-1) and full flow (27.6 +/- 9.9 versus 16.8 +/- 3.7 mL.min-1.100 g-1) (p < 0.01). At comparable mean arterial blood pressure, alteration of pump flow rate produced no significant change in cerebral blood flow.
  
  
  CONCLUSIONS
  These results indicate that during low-flow CPB, mean arterial pressure should be maintained within the brain's autoregulatory range to maximize cerebral blood flow.
authors.affiliation: Department of Surgery, Columbia University College of Physicians & Surgeons, New York, New York 10032, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Michler
authors.forename: A A
authors.initials: AA
authors.lastname: Sandhu
authors.forename: W L
authors.initials: WL
authors.lastname: Young
authors.forename: A E
authors.initials: AE
authors.lastname: Schwartz
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002315:Cardiopulmonary Bypass; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006439:Hemodynamics; D006706:Homeostasis; D008297:Male; D010215:Papio