Relative importance of flow versus pressure in splanchnic perfusion duringcardiopulmonary bypass in rabbits

Background: Decreased gastrointestinal perfusion has been reported during c ardiopulmonary bypass (CPB). Conflicting results have been published concer ning thresholds of pressure and flow to avoid splanchnic ischemia during CP B, This study compared splanchnic perfusion during independent and randomiz ed variations of CPB pump flow or arterial pressure. Methods: Ten rabbits were studied during mild hypothermic (36 degrees C) no npulsatile CPB using neonatal oxygenators, Simultaneous measurements of tis sue blood flow in four different splanchnic areas (gastric, jejunum, ileum, and liver) were performed by laser Doppler flowmetry (LDF) before CPB (T0) and during a 4-step factorial experimental block design. Pressure and now were alternatively high or low in random order. Results: Laser Doppler flowmetry was significantly lower than pre-CPB value but was better preserved (analysis of covariance) in all organs, except li ver, when CPB flow was high, whatever the pressure. Splanchnic LDF values i n the low- versus high-flow groups expressed as perfusion unit were (mean /- SD): stomach, 94 +/- 66 versus 137 +/- 75; jejunum, 118 +/- 78 versus 17 2 +/- 75; ileum, 95 +/- 72 versus 146 +/- 83; and liver, 79 +/- 72 versus 1 08 +/- 118, No significant difference of LDF was observed between the high- and low-pressure groups, whatever the flow, except for liver: stomach, 115 +/- 64 versus 117 +/- 83; jejunum, 141 +/- 80 versus 148 +/- 83; ileum, 12 7 +/- 87 versus 114 +/- 76; liver, 114 +/- 88 versus 73 +/- 70. Conclusion: Prevention of splanchnic ischemia during CPB should focus on pr eservation of high CPB blood now rather than on high pressure.