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 combi nation with dobutamine, modifies the gastric intramucosal-arterial PCO2 dif ference. 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 intraveno usly postoperatively) and dobutamine (4 mu g.kg(-1).min(-1) for 3 h postope ratively) were administered in four randomised groups of patients: preopera tive and postoperative ranitidine, either alone (n = 15) or in combination with dobutamine (n = 17), dobutamine alone (n = 15) or neither ranitidine n or dobutamine (n = 17). Measurements and results: Gastric intramucosal-arterial PCO2 difference was measured during the first 5 postoperative hours. No differences in the pos toperative pattern of gastric intramucosal-arterial PCO2 difference were fo und among the groups. Conclusions: Ranitidine and dobutamine have no effect on the gastric tonome try results on intramucosal-arterial PCO2 difference after uncomplicated ca rdiac surgery. Hence, the routine use of H-2-antagonists for gastrointestin al tonometry is not warranted. Our results must be limited to results obtai ned by tonometry; they do not allow any conclusions on the effects of these drugs on splanchnic blood flow or its distribution.