Comparison of gastric luminal and gastric wall PCO2 during hemorrhagic shock

Measurement of gastric wall PCO2 has emerged as a promising monitor of perfusion deficits during low-flow states of circulatory shock. In the present study, gastric luminal PCO2 measured with the gastric tonometer was compared with the PCO2, measured directly in the wall of the stomach during hemorrhagic shock in two groups of five Sprague-Dawley rats. One group was pretreated with the H2 blocker, ranitidine. During a 120-min interval of hemorrhage, tonometer PCO2 increased from 60 +/- 7 mmHg to 90 +/- 10 mmHg, and time-coincident gastric wall PCO2 from 52 +/- 5 mmHg to 131 +/- 14 mmHg. Following reinfusion of shed blood, tonometer PCO2 remained elevated for an interval exceeding 60 min, but gastric wall PCO2 returned to control levels within approximately 10 min. Ranitidine pretreatment did not alter the relationships between gastric wall PCO2 and tonometer PCO2. These observations indicate that gastric luminal PCO2 underestimates relatively rapid increases in gastric wall PCO2 during profound hemorrhagic shock in rats.