Transfusion of anemic patients with
hemoglobin-based
oxygen carriers (HBOCs) may improve cerebral
oxygen delivery. Conversely, cerebral vasoconstriction, associated with HBOC transfusion, could limit optimal cerebral tissue oxygenation. We hypothesized that
hemodilution with a HBOC would maintain cerebral tissue oxygenation, despite the occurrence of cerebral vasoconstriction.
Isoflurane-anesthetized rats (100%
oxygen) underwent direct measurement of mean arterial blood pressure (MAP), caudate tissue
oxygen tension (P(Br)o(2)), and regional cortical cerebral blood flow (rCBF) before and after 50% of the estimated blood volume (30 mL/kg) was exchanged with either an HBOC (
hemoglobin raffimer;
Hemolink) or
pentastarch (n = 6).
Hemodilution with
hemoglobin raffimer caused a transient increase in P(Br)o(2) from 24.9 +/- 13.3 mm Hg to 32.2 +/- 19.1 mm Hg (P < 0.05), a sustained increase in MAP, and no change in rCBF. Arterial blood
oxygen content was maintained despite an increase in
methemoglobin and reduced oxygen saturation.
Hemodilution with
pentastarch caused a transient increase in MAP, no change in P(Br)o(2), and a sustained increase in rCBF (P < 0.05), whereas the
hemoglobin concentration and
oxygen content were significantly reduced.
Hemodilution with
hemoglobin raffimer augmented P(Br)o(2) and prevented the increase in rCBF observed after similar
hemodilution with
pentastarch. These data suggest that transfusion with
hemoglobin raffimer may help to maintain cerebral oxygenation during severe
anemia.