Effects of F I O 2 on hemodynamic responses and O2 transport during RSR13-induced reduction in P50

Abstract

Reduced Hb-O2 affinity facilitates O2 release to tissue but may impair pulmonary O2 uptake, affecting cardiac output and systemic vascular resistance (SVR). We studied the effects of shifting the O2-dissociation curve (ODC) to the right with a continuous infusion of RSR13, an allosteric modifier of Hb, and of different inspired O2fractions ([Formula: see text]) on arterial O2 saturations ([Formula: see text]) in Hb and on hemodynamics in nonanesthetized rats. At an[Formula: see text] of 0.21,[Formula: see text] fell during RSR13 from 95 to 81%. Elevation of [Formula: see text] to 0.30 returned [Formula: see text] to baseline in the RSR13 group. The decrease in mean arterial pressure (MAP) was significantly greater in the control than in the RSR13 group at 30% O2. Cardiac index (CI) increased only during RSR13 at 21% O2 and returned to baseline at 30% O2. In contrast, SVR decreased after RSR13 was infused at 21% O2 but returned to baseline at 30%O2, whereas controls showed the opposite, a sustained SVR. In the follow-up period, when 21 O2% was reestablished and mild anemia was present, MAP and SVR fell significantly more in controls, whereas CI only increased in controls. Lactate was significantly lower in the RSR13 than in the control group during RSR13 and the follow-up period. These results demonstrate that 1) continuous infusion of RSR13 produces a constant shift in the O2 tension at which Hb is 50% saturated (P50), 2)[Formula: see text] of 0.30 compensates for the effects of increased P50 on pulmonary O2 loading, and 3) right-shifted ODC combined with supplemental O2 may improve tissue O2 availability.