As systemic oxygen delivery (DO2
) is reduced, oxygen consumption (VO2
) is maintained until a critical level is reached (DO2
crit) below which VO2
becomes supply-dependent and anaerobic metabolism ensues. We examined the relationship between gastric intramucosal PCO2
) and the onset of systemic supply dependency. We also compared PiCO2
to mixed venous and portal venous blood PCO2
) to assess their utility as premonitory indicators of supply dependency.
Six dogs were subjected to stepwise hemorrhage to effect a progressive decrease in DO2
. Inflection points for changes in VO2
, PmvCO (2
), and PpvCO2
crit was 6.0 +/- 0.7 mL[center dot]kg-1
, whereas the DO2
at which inflection points occurred for PiCO (2
) and PpvCO2
were 13.2 +/- 1.4 and 11.2 +/- 1.5 mL[center dot]kg-1
, respectively (p < 0.05 for both).
Continuous monitoring of PiCO2
using capnometric recirculating gas tonometry can serve as an early indicator of systemic hypoperfusion before the onset of systemic supply dependency.