Critical oxygen delivery in conscious septic rats under stagnant or anemic hypoxia.

Although evidence shows that critical O-2 delivery (QO(2)crit), the point at which oxygen consumption becomes limited by 02 delivery (QO(2)), is not affected by the method used to decrease QO(2) in healthy subjects, microcirculatory injury caused by sepsis may modify QO(2), crit in a unique manner. We therefore designed this study to compare QO(2)crit in anemic and stagnant hypoxia in conscious septic rats. Rats were randomized to control or sepsis induced by cecal ligation and perforation; 24 hours later, oxygen consumption was measured using expired gas analysis, whereas QO(2) was calculated from standard formula. Rats were further randomized to anemic hypoxia by isovolemic hemodilution or stagnant hypoxia by step-wise inflation of a balloon-tip catheter in the right atrium. QO(2)crit and critical hemoglobin concentration were calculated by dual linear regression analysis. We found that (1) QO(2)crit was not different between anemic and stagnant hypoxia in sepsis and that (2) the critical hemoglobin concentration in anemic hypoxia was similar between sepsis and control, indicating that tolerance to acute anemia is not altered by sepsis. Further studies are needed before the clinical relevance of these conclusions can be fully understood.