DOBUTAMINE-INDUCED DISSOCIATION BETWEEN CHANGES IN SPLANCHNIC BLOOD-FLOW AND GASTRIC INTRAMUCOSAL PH AFTER CARDIAC-SURGERY

Gastric intramucosal acidosis, a sign of splanchnic tissue hypoxia, is common after cardiac surgery. We tested the hypothesis that an increa se in splanchnic blood flow induced by dobutamine improves splanchnic tissue oxygenation after cardiac surgery. We measured changes in gastr ic intramucosal pH, splanchnic blood flow and oxygen transport in resp onse to increased systemic flow induced by dobutamine (mean 4.4 (range 3.0-7.0) mu g kg(-1) min-l) after coronary artery bypass. We studied 22 stable postoperative patients who were allocated randomly to receiv e dobutamine (n = 11) or to serve as controls (n = 11). Dobutamine was given also to a separate group with a low cardiac index after operati on (n = 6). The end-point was to increase cardiac index by at least 25 % and to exceed 2 litre min(-1) m(-2). Dobutamine consistently increas ed mean splanchnic blood flow (control 0.6 (SD 0.2) vs 0.7 (0.2) litre min(-1) m(-2) (P < 0.05); normal cardiac output and dobutamine 0.7 (0 .2) vs 1.1 (0.4) litre min(-1) m(-2) (P < 0.01); low cardiac output an d dobutamine 0.4 (0.1) vs 0.7 (0.1) litre min(-1) m(-2) (P < 0.05)) an d oxygen delivery (control 102 (29) vs 111 (28) ml min(-1) m(-2) (ns); normal cardiac output and dobutamine 106 (27) vs 156 (47) ml min(-1) m(-2) (P < 0.01); low cardiac output and dobutamine 75 (21) vs 110 (26 ) ml min(-1) m(-2) (P < 0.05)) but had no effect on splanchnic oxygen consumption (control 44 (10) vs 49 (10) ml min(-1) m(-2) (ns); normal cardiac output and dobutamine 45 (12) vs 51 (17) ml min(-1) m(-2) (ns) ; low cardiac output and dobutamine 37 (9) vs 40 (9) ml min(-1) m(-2) (ns)). Despite this, dobutamine reduced gastric intramucosal pH in all patients with low cardiac output (7.33 (0.12) vs 7.25 (0.06) (P < 0.0 5)) and in 50% of patients with stable haemodynamics (7.37 (0.07) vs 7 .34 (0.06) (ns)). In contrast, gastric intramucosal pH remained stable in the control group (7.34 (0.05) vs 7.34 (0.04) (ns)). We conclude t hat dobutamine resulted in a dissociation between splanchnic oxygen de livery and gastric mucosal tissue oxygenation, suggesting inappropriat e distribution of blood flow within the splanchnic region.