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The effect of low-dose dopexamine and dopamine on gastric intramucosal pH (pHi) during cardiac surgery and 16 hours postoperatively was studied in 35 adults patients (coronary artery bypass grafting and/or valve replacement). The patients were assigned randomly to treatment groups with either dopexamine (1 microgram.kg-1.min-1 (n = 12), dopamine 2.5 micrograms.kg-1.min-1 (n = 11) or to a control group (n = 12). The infusions were started after induction of anaesthesia and were continued until 16 hours after CPB. pHi and arterial pH (pHa) 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 (PaCO2) and of the saline in the tonometer (PtonCO2) 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 pHi and pHa and between arterial and tonometric PCO2. It is concluded that low dose dopexamine and dopamine have no influence on pHi during and after cardiac surgery. The observed changes in pHi and PtonCO2 were due to changes in pHa and in PaCO2 and not a sign of gastric mucosal ischemia.

Gastric tonometry was used to study the possible effect of dopexamine infusion on a low calculated intramucosal pH (pHi) as a sign of splanchnic ischemia. Measurements were made during surgery and for approximately 18 hours postoperatively on 19 non-selected adult patients undergoing valve replacement. Patients developing a postoperative pHi > 7.30 were randomized to receive dopexamine (2 micrograms.kg-1 min-1) or placebo in a double blind fashion. Eighteen patients were randomized, 10 to receive dopexamine and 8 to placebo. The calculated pHi remained unchanged for the first 2 hours in both groups. After 4 hours a significant (P < 0.05) decrease in pHi was noted in the dopexamine group which remained significantly below the placebo group during the monitoring period. The dopexamine treated patients had a significantly longer period of low pHi but the pH-gap i.e. the difference between arterial pH and pHi did not differ between the two groups. Patients with postoperative complications, defined as infections (2), myocardial infarction (1), single- (2) or multiple organ failure and death (1), did not have longer periods with pHi below 7.30. In these patients, however, a pH-gap > 0.12 occurred more often than in those without complications, indicating that an increased incidence of complications was related to a pH-gap > 0.12. It is our opinion that true mucosal ischemia is best detected by estimating the difference in carbon dioxide tension between arterial blood and mucosa. This can be expressed either directly as PCO2-gap (PtonCO2-PaCO2) or indirectly as pH-gap.

A patient underwent pulmonary thromboendoarterectomy for chronic, major-vessel thromboembolic pulmonary hypertension. After operation the patient developed reperfusion oedema and hypoxaemia which was treated successfully with inhalation of nitric oxide. Before operation, the response to inhaled nitric oxide was characterized by a slight reduction in pulmonary vascular resistance but without improvement in gas exchange. The postoperative improvement in oxygenation after inhalation of nitric oxide contrasted sharply with the preoperative reaction.

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