Effect of low-dose milrinone on gastric intramucosal pH and systemic inflammation after hypothermic cardiopulmonary bypass

Objective: To investigate the usefulness of low-dose milrinone on gastric i ntramucosal pH (pHi) and systemic inflammation in patients undergoing hypot hermic cardiopulmonary bypass (CPB). Design: Prospective randomized study. Setting: University hospital. Participants: Twenty patients scheduled for cardiac surgery. Interventions: Ten patients were administered a low dose of milrinone, 0.25 mug/kg/min, from the initiation of CPB to 1 hour after admission to the in tensive care unit. The other patients were administered saline. Supplementa l inotropes and intravenous fluid were given to obtain adequate mean arteri al blood pressure and pulmonary artery occlusion pressure. Measurements and Main Results: Gastric pHi and carbon dioxide pressure (PCO 2) were assessed by capnometric air tonometry. The difference between PCO2 and arterial carbon dioxide pressure (PaCO2), PCO2-gap, was also examined. Systemic inflammatory responses were evaluated by serum interleukin-6 and l eukocyte counts. Hemodynamics, oxygen delivery index, and oxygen uptake ind ex were monitored with catheters in the radial and pulmonary arteries (ther modilution). The hepatic venous blood flow and left ventricular flow were m easured using transesophageal echocardiography. Milrinone prevented gastric intramucosal acidosis, detected as a decrease in pi-ii or an increase in P CO2-gap, without affecting hepatic venous blood flow. Increases in interleu kin-6, leukocyte count, and oxygen uptake index, all of which developed aft er CPB, were significantly less in the milrinone group than in the control group. Conclusion: These results suggest that in patients undergoing hypothermic C PB, supplemental low-dose milrinone prevents gastric intramucosal acidosis and increases in some markers of systemic inflammation. Copyright (C) 2001 by W.B. Saunders Company.