Wednesday, January 30, 2013

Heart, kidney, and intestine have different tolerances for anemia


Heart, kidney, and intestine have different tolerances for anemia

JASPER VAN BOMMEL, MARTIN SIEGEMUND, CH. PIETER HENNY, and CAN INCE
ROTTERDAM, THE NETHERLANDS; BASEL, SWITZERLAND; AND AMSTERDAM, THE NETHERLANDS


Organ systems do not respond uniformly to changes in systemic oxygen delivery
because of global and local redistributive mechanisms. We hypothesized that
progressive hemodilution would evoke a different response in the microvascular
oxygenation of the heart compared with kidney and gut. To evaluate this hypothesis,
we studied the effect of stepwise isovolemic hemodilution on systemic hemodynamic
and oxygenation parameters as well as the relation between systemic
hematocrit (Ht) and microvascular PO2 ( PO2) in heart, kidney, and intestines in an
anesthetized and mechanically ventilated rat model.
Baseline conditions were similar in the hemodilution group and in the control group.
In the hemodilution group, Ht was diminished from 46.6 3.8% to 7.0 1.8% [mean
standard deviation (SD)]. This group had no effect on measured hemodynamics;
only when Ht fell below 10% did blood pressure start to decrease. The PO2 values
in heart, kidney, and intestines did not respond uniformly. Renal PO2 (56 10 mm
Hg at baseline) started to decrease at a Ht of 38.5 8.6%, whereas intestinal PO2
(59 6 mm Hg at baseline) did not start to decrease until Ht reached 17.4 7.1%.
Finally, cardiac PO2 (40 6 mm Hg at baseline) decreased only in the ultimate
stage of the experiment at Ht of 8.7 3.5%.
Based on these observations, we conclude that the regulation of microvascular
oxygenation during progressive anemia is specific for each organ system. The
relation between these observations and organ function and damage needs to be
determined. (Translational Research 2008;151:110-117)