Changes of oxygen transport variables and serum lactate during open-chest cardiac massage in dogs

The aim of this study was to investigate the influence of critically low cardiac output (CO) upon oxygen transport. We especially focused on the changes of mixed venous oxygen saturation (S-vO₂) in the presence of oxygen consumption ([Formula: see text]) debts. Additionally, we examined the correlation between the cumulative oxygen deficit (Def[Formula: see text]) and serum lactate. Def[Formula: see text] was calculated as the integrated area under the tissue[Formula: see text]) deficit (baseline[Formula: see text]-acutal[Formula: see text]) and time curve. To produce severe low CO, we performed openchest cardiopulmonary resuscitation (CPR) in 11 anesthetized dogs for 1 h. We made the measurements before (baseline values) and during the CPR at 10-min intervals. Supplydependent[Formula: see text] was observed when CO decreased below 40 ml·min^-1·kg^-1. The mean value of S-vO₂ in the range of supply-dependent[Formula: see text] was 13±2% and did not change significantly during 1 h of CPR. The changes of lactate from baseline values were linearly correlated with Def[Formula: see text] (r=0.62,P<0.01), but absolute values of serum lactate were not.