Distribution and hierarchy of regional blood flow during hypothermic cardiopulmonary bypass

Background. Cardiopulmonary bypass (CPB) may decrease oxygen delivery relat ive to the nonbypass state. We predicted that a hierarchy of regional blood flow could be characterized under hypothermic 27 degreesC CPB. Methods. Ten pigs underwent bypass at 27 degreesC. Fluorescent microspheres were administered before and during CPB at four randomized flows: 1.9, 1.6 , 1.3, and 1.0 L (.) min(-1) (.) m(-2). At completion, tissue samples were obtained from brain, renal cortex and medulla, pancreas, small bowel, and l imb muscle for regional blood flow determination. Results. Cerebral blood flow remained unchanged between CPB flows of 1.9 an d 1.3 L (.) min(-1) (.) m(-2). Renal perfusion was stable between flows of 1.9 and 1.6 L (.) min(-1 .) m(-2), whereas perfusion of small bowel decreas ed linearly with pump flow. Pancreatic perfusion was unchanged over the ran ge of flows studied; muscle blood flow was profoundly reduced at the highes t CPB flow and further decreased if pump flow was reduced below 1.6 L (.) m in(-1) (.) m(-2). Conclusions. This study characterizes the organ-specific hierarchy of blood flow and oxygen distribution during hypothermic CPB. These dynamics are re levant to clinical decisions for perfusion management. (C) 2001 by The Soci ety of Thoracic Surgeons.