Ranitidine or dobutamine alone or combined has no effect on gastric intramucosal-arterial PCO2 difference after cardiac surgery

Objective: To test the hypothesis that ranitidine, either alone or in combination with dobutamine, modifies the gastric intramucosal-arterial PCO2 difference. Design: Full factorial design (double-blinded for ranitidine). Setting: Intensive Care Unit of a university hospital. Patients: Sixty-four haemodynamically stable coronary artery bypass surgery patients. Interventions: Ranitidine (150 mg preoperatively per os and 50 mg intravenously postoperatively) and dobutamine (4 mu g.kg(-1).min(-1) for 3 h postoperatively) were administered in four randomised groups of patients: preoperative and postoperative ranitidine, either alone (n = 15) or in combination with dobutamine (n = 17), dobutamine alone (n = 15) or neither ranitidine nor dobutamine (n = 17). Measurements and results: Gastric intramucosal-arterial PCO2 difference was measured during the first 5 postoperative hours. No differences in the postoperative pattern of gastric intramucosal-arterial PCO2 difference were found among the groups. Conclusions: Ranitidine and dobutamine have no effect on the gastric tonometry results on intramucosal-arterial PCO2 difference after uncomplicated cardiac surgery. Hence, the routine use of H-2-antagonists for gastrointestinal tonometry is not warranted. Our results must be limited to results obtained by tonometry; they do not allow any conclusions on the effects of these drugs on splanchnic blood flow or its distribution.