Relationship between cardiac output and mixed venous-arterialPCO ₂ gradient in sodium bicarbonate-treated dogs

We examined the relationship between cardiac output (CO) and mixed venous-arterialPCO ₂ gradient ([Formula: see text]) along with the other variables derived from arterial and/or mixed venous blood gases in sodium bicarbonate-treated dogs. Six dogs with low cardiac output following cardiopulmonary resuscitation were used. CO, blood gases, and hemoglobin measurements were repeated every 20-30 min after administration of sodium bicarbonate or normal saline. All measurements were performed after the confirmation of a steady state of CO₂ elimination by end-tidal CO₂ monitoring. Arteriovenous oxygen content difference ([Formula: see text]), mixed venous oxygen saturation ([Formula: see text]), and[Formula: see text] were highly correlated with CO. The correlation coefficients between[Formula: see text],[Formula: see text], and[Formula: see text] werer=-0.81 (P<0.001),r=0.70 (P<0.001), andr=-0.77 (P<0.001), respectively. The results suggest that, if[Formula: see text] is measured during the steady state, except for the period during the transient increase in CO₂ elimination just after the administration of sodium bicarbonate,[Formula: see text] can be used as an index of systemic perfusion even after the administration of sodium bicarbonate.