Fetal oxygen content is restored after maternal hemorrhage and fluid replacement with polymerized bovine hemoglobin, but not with hetastarch, in pregnant sheep

We investigated the ability of hemoglobin-based oxygen carrying solutions ( HBOCs) to alleviate fetal hypoxemia from maternal hemorrhage. Fifteen pregn ant ewes (132-day gestational age) were hemorrhaged 20 mL/kg over 1 h; they were randomized to receive 20 mL/kg TV of HBOC, hetastarch (HTS), or autol ogous blood (BLD) (n = 5 each) over 30 min and were monitored for 2 h. Hemo rrhage significantly (P less than or equal to 0.05) decreased maternal mean blood pressure (from 98 to 48 mm Hg, median), arterial oxygen content (fro m 12.2 to 11.1 mL/dL), and fetal arterial oxygen content (from 8.1 to 3.9 m L/dL). Fluid replacement restored maternal blood pressure in all groups, al though maternal oxygen content immediately returned to baseline only after BLD or HBOC. Maternal oxygen saturation decreased after HBOC (from 98% to 8 8%). Fetal oxygen content rapidly returned to baseline with either BLD (7.1 mL/dL) or HBOC (8.0 mL/dL) but was never restored with HTS (4.7 mL/dL), an d, 60 min after fluid replacement, it was higher with HBOC (8.3 mL/dL) than with HTS (4.7 mL/dL). Fetal plasma-free hemoglobin did not change after HB OC. In conclusion, maternal fluid replacement with HBOC or BLD effectively restored fetal oxygenation, primarily by restoring maternal oxygen content, whereas HTS did not.