The effect of different bypass flow rates and low-dose dopamine on gut mucosal perfusion and outcome in cardiac surgical patients.

The aim of this double-blind, randomized, placebo-controlled trial was to investigate the effects of different cardiopulmonary bypass flow rates and low-dose dopamine on gastric mucosal pH (pHi) and outcome. We hypothesized that by minimizing gut mucosal hypoperfusion during and after cardiac surgery endotoxin translocation may be prevented, resulting in an improved clinical outcome. Four groups of 25 patients each receiving high or low flows during bypass and low-dose dopamine or saline for 24 hours after induction of anaesthesia were studied. The pHi was measured at six time intervals over 24 hours. The combination of low-dose dopamine and a low bypass flow rate was associated with a significantly greater frequency and severity of low pHi. This group also demonstrated a significantly lower vascular resistance on admission to the intensive care unit. There may be an association between low pHi and low vascular resistance.