Gastric mucosal end-tidal PCO2 difference as a continuous indicator of splanchnic perfusion

Abstract

Gastric mucosal and arterial blood Pco2 must be known to assess mucosal perfusion by means of gastric tonometry. As end-tidal Pco2 (PE'(co2)) is a function of arterial Pco2, the gradient between PE'(co2) and gastric mucosal Pco2 may reflect mucosal perfusion. We studied the agreement between two methods to monitor gut perfusion. We measured the difference between gastric mucosal Pco2 (air tonometry) and PE'(co2) (=DPco(2gas)) and the difference between gastric mucosal Pco2 (saline tonometry) and arterial blood Pco2 (=DPco(2sal)) in 20 patients with or without lung injury. DPco(2gas) was greater than DPco(2sal) but changes in DPco(2gas) reflected changes in DPco(2sal). The bias between DPco(2gas) and DPco(2sal) was 0.85 kPa and precision 1.25 kPa. The disagreement between DPco(2gas) and DPco(2sal) increased with increasing dead space. We propose that the disagreement between the two methods studied may not be clinically important and that DPco(2gas) may be a method for continuous estimation of splanchnic perfusion.