Bladder Mucosal CO2 Compared with Gastric Mucosal CO2 as a Marker for Low Perfusion States in Septic Shock

Abstract

Recent reports indicate the possible role of bladder CO2 as a marker of low perfusion states. To test this hypothesis, shock was induced in six beagle dogs with 1 mg/kg of E. coli lipopolysaccharide, gastric CO2 (CO2-G) was measured with a continuous monitor, and a pulmonary catheter was inserted in the bladder to measure CO2 (CO2-B). Levels of CO2-B were found to be lower than those of CO2-G, with a mean difference of 36.8 mmHg (P<0.001), and correlation between both measurements was poor (r2=0.16). Even when the correlation between CO2-G and ΔCO2-G was narrow (r2=0.86), this was not the case for the relationship between CO2-B and ΔCO2-B (r2=0.29). Finally, the correlation between CO2-G and base deficit was good (r2=0.45), which was not the case with the CO2-B correlation (r2=0.03). In our experience, bladder CO2 does not correlate to hemodynamic parameters and does not substitute gastric CO2 for detection of low perfusion states.