Changes in gastric intramucosal pH and circulating blood volume following coronary artery bypass grafting

To determine the changes in gastric intramucosal pH (pHi) following coronary artery bypass grafting (CABG) in comparison with systemic hemodynamic variables and circulating blood volume (BVc).

Twenty patients who underwent CABG under mild hypothermic cardiopulmonary bypass (CPB) were included. Hemodynamic variables and the values of pHi were obtained at 3,6, 12 and 24 hr after admission to the intensive care unit (ICU). The pHi was measured by gastric tonometric catheter. The BVc was measured by carbon monoxide (CO)-labeled hemoglobin (CO-Hb) dilution method (CO method) at 6 and 24 hr after ICU admission.

Systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI) decreased with time. Systemic oxygen delivery index (DO2I) and systemic oxygen consumption index (VO2I) showed a gradual increase during the study period. By contrast, pHi decreased to the lowest value (7.26+/-0.05) at six hours and returned to normal levels (7.34+/-0.04) at 24 hr after ICU admission. Changes in BVc between six and 24 hr ranged from -242 ml to 978 ml (mean, 334+/-338 ml). The pHi increased in patients whose BVc increased by > 300 ml. Mean fluid balance was negative in this period (-386+/-667 ml; range, -1786 - + 423 ml).

The pHi showed the lowest value at six hours and returned to normal at 24 hr after ICU admission. The pHi increased with the decrease in vascular resistance and with the increases in BVc in this period. The improvement of pHi, an indicator of splanchnic perfusion, appears to be related to systemic vasodilatation and an increase in BVc.