Dopexamine and dopamine in the prevention of low gastric mucosal pH following cardiopulmonary by-pass

The effect of low-dose dopexamine and dopamine on gastric intramucosal pH (pH_i) during cardiac surgery and 16 hours postoperatively was studied in 35 adult patients (coronary artery bypass grafting and/or valve replacement). The patients were assigned randomly to treatment groups with either dopexamine 1 μg. kg^-1.min^-1 (n=12), dopamine 2.5 μg. kg^-1.min^-1 (n=11) or to a control group (n=12). The infusions were started after induction of anesthesia and were continued until 16 hours after CPB. pH_i and arterial pH (pH_a) did not differ between groups and remained unchanged during cardiopulmonary by-pass and for the first four postoperative hours. Both the carbon dioxide tension of arterial blood (P_aCO₂) and of the saline in the tonometer (P_tonCO₂) changed in parallel with a decrease during CPB and an increase after CPB and surgery with maximal values 12 hours after termination of CPB. A significant correlation was noted between pH_i and pH_a and between arterial and tonometric PCO₂. It is concluded that low dose dopexamine and dopamine have no influence on pH_i during and after cardiac surgery. The observed changes in pH_i and P_tonCO₂ were due to changes in pH_a and in P_aCO₂ and not a sign of gastric mucosal ischemia