Interpretation
RBC and PPP transfusion achieved excellent prognosis and yielded a
better foetus survival rate than did HES infusion (79% vs. 38%, on an
average), although the difference was not significant. Some animals
transfused with RBCs achieved the target Hb concentration of up to 9
g/dL after transfusion for PPH.30,31 Consequently, the
maternal CtO2 levels reached >10 vol %,
which ensured a foetal CtO2 of 8 vol
%32. HbV infusion also maintained haemodynamic
parameters and CtO2 levels to the systemic tissues
throughout the experiment. The acute prognosis of the HbV group was
significantly better than that of the HES group, whereas it was
significantly worse than that of the RBC/PPP group. HbV infusion yielded
a foetus survival rate of 56%. HbVs have a shorter half-life than
RBCs24, which might affect the prognosis beyond 6
hours. In addition, carbonic anhydrase is not incorporated into HbV.
Consequently, plasma HCO3- levels in
the HbV group was significantly lower than that in the RBC group. This
may be critical because some studies reported that low
HCO3-, particularly <16
mmol/L, independently predicted short-term
prognosis33.
Chemically modified, cell-free HBOCs, including
glutaraldehyde-polymerised and PEG-conjugated Hbs, have advanced to
clinical trials34,35. Nevertheless, such cell-free
HBOCs showed toxicities caused by extravasation, oxidative stress,
hypertension, and vasoconstriction. In contrast, the current HbVs
compartmentalise a concentrated Hb solution in the inner aqueous phase
of liposomes, analogous to erythrocytes, leading to reduced toxicities
of bared Hb7,10,19. In this study, HbV administration
had no scavenging effect on plasma NOx levels. We
previously observed that HbVs did not cross the placental
barrier36. Moreover, HbVs may be beneficial for
foetuses because they are degraded by the maternal reticuloendothelial
system, which is premature in the foetuses. However, the optimal
strategy for improving foetal hypoxia or shock stress is an important
issue that needs further research in the management of severe PPH.