Resuscitative efficacy of hemoglobin vesicles for severe postpartum hemorrhage in pregnant rabbits

Abstract

We aimed to investigate the resuscitative efficacy of hemoglobin vesicles (HbVs) as a red blood cell (RBC) substitute for the initial treatment of severe postpartum hemorrhage (PPH). Twenty-five pregnant rabbits underwent cesarean section; uncontrolled hemorrhage was induced by transecting the right uterine artery to establish a severe PPH model. During the first 30 min, all rabbits were administered 6% hydroxyethyl starch (HES) of an equivalent volume to the hemorrhage every 5 min. Thereafter, they received any of the following three isovolemic fluids for resuscitation every 5 min: RBCs with platelet-poor plasma (RBC/PPP) (n = 8), 6% HES (n = 7), or HbVs with 25% human serum albumin (n = 10). After surgical hemostasis at 60 min, survival was monitored until 12 h. No rabbits receiving only HES infusion survived beyond 6 h, whereas all rabbits receiving RBC/PPP transfusion survived. The rabbits receiving HbV infusion showed significantly higher mean arterial pressure and hemoglobin levels than the HES-receiving rabbits, and 8 of 10 rabbits survived for 6 h. The HbV group showed significantly higher survival than the HES group but worse survival than the RBC/PPP group. In conclusion, HbV infusion for severe PPH effectively prevents lethal hemorrhagic shock in a pregnant rabbit model.

Figure 1

Surgical procedures and experimental protocol. (A) Rabbits underwent cesarean section to deliver fetuses from the right side of the bicornate uterus. (B) After closing the incision in the uterus, uncontrolled hemorrhage is induced by transecting the right uterine artery. (C) Pregnant rabbits undergo CS, and uncontrolled hemorrhage is progressed to severe PPH. First, all rabbits are administered 6% HES for initial treatment. After progressed to severe PPH, the rabbits receive isovolemic fluid resuscitation with an equivalent volume of hemorrhage every 5 min. Resuscitative administration regimens include the following: RBC/PPP (vol/vol = 1:1, n = 8), 6% HES (n = 7), or HbVs with 25% human serum albumin (vol/vol = 4:1, n = 10). After 60 min from the start of hemorrhage or when the hemorrhage volume reaches 200 mL, surgical hemostasis is performed. Survival is monitored thereafter for at least 12 h. Data shown are the mean ± standard deviation. Alb albumin, BL blood loss, CS caesarean section, HbV haemoglobin vesicles, HES hydroxyethyl starch, PPH postpartum haemorrhage, RBC/PPP red blood cells with platelet-poor plasma.

Figure 2

Hemodynamic changes and survival curves of all three groups. (A) The HES group shows progressively decreased MAP after 30 min, and the values are significantly lower than in the other groups. (B) In the HES group, the shock index from 25 to 45 min is significantly higher than in the other groups, whereas there is no significant difference at 60 min. (C) Survival of the HbV group is significantly better than that of the HES group (P < 0.01), whereas it is significantly worse than that of the RBC/PPP group (P = 0.01). *P < 0.05, value significantly different from the other groups. ^†P < 0.05, the prognosis of the RBC/PPP group is significantly different from that of the other groups. ^‡P < 0.05, the prognosis of the HbV group is significantly different from that of the HES group. Data shown are the mean ± standard deviation. HbV hemoglobin vesicles, HES hydroxyethyl starch, MAP mean arterial pressure, RBC/PPP red blood cells with platelet-poor plasma.

Figure 3

Changes in the levels of hematologic and blood gas variables. (A) At 60 min, the hemoglobin concentration is maintained over 6.0 g/dL in the RBC/PPP and HbV groups, whereas it decreases under 2.0 g/dL in the HES group. (B) The hematocrit is similarly decreased in both the HbV and HES groups, unlike that in the RBC/PPP group. (C) The pH levels in the HES group are significantly lower than those in the other groups after 30 min. (D) The base excess levels at 45 and 60 min are significantly higher in the RBC/PPP group than in the other groups. (E) The CtO₂ level is decreased in all groups until 30 min; however, it is maintained above approximately 7.0 vol% beyond 30 min in the RBC/PPP and HbV groups. (F) At 60 min, the lactate acid levels are significantly higher in the HES group than in the other groups. *P < 0.05, value significantly different from the other groups. Data shown are the mean ± standard deviation. CtO₂ concentration of total oxygen, HbV hemoglobin vesicles, HES hydroxyethyl starch, RBC/PPP red blood cells with platelet-poor plasma.

Figure 4

Changes in the levels of (A) PaO₂, (B) PaCO₂, and (C) HCO₃. (A) There are no significant differences in the PaO₂ levels among all the groups throughout the experiment. (B) There are also no significant differences in the PaCO₂ levels among all groups throughout the experiment. (C) At 45 and 60 min, the HCO3^- level is significantly higher in the RBC/PPP group than in the other groups. *P < 0.05, value significantly different from the other groups. Data shown are the mean ± standard deviation. HbV hemoglobin vesicles, HES hydroxyethyl starch, RBC/PPP red blood cells with platelet-poor plasma.

Figure 5

Changes in the levels of coagulation variables. (A) The plasma fibrinogen values in the RBC/PPP group are maintained over 110 mg/dL even at 60 min. (B) The AT III values are significantly lower in the HbV and HES groups than in the RBC/PPP group at 45 and 60 min. (C) The PT values are significantly longer in the HbV and HES groups than in the RBC/PPP group at 60 min. (D) The APTT values after 30 min is set as the reference value because the value over 75 s could not be measured in the current analysis. (E) ACT at 60 min is significantly longer in the HES group and the HbV group than in the RBC/PPP group. (F) There are no significant differences in the clot rate among the three groups throughout the experiment. *P < 0.05, value significantly different from the other groups. ^†At 60 min, the APTT levels are unmeasurable in the HbV and HES groups. Data shown are the mean ± standard deviation. ACT activated clotting time, APTT activated partial thromboplastin time, AT III antithrombin III, HbV hemoglobin vesicles, HES hydroxyethyl starch, PT prothrombin time, RBC/PPP red blood cells with platelet-poor plasma.

Figure 6

Changes in the levels of Fe²⁺ and cell-free heme. (A) The values of Fe²⁺ tends to increase in the HbV and RBC/PPP groups after 30 min. (B) The concentration of cell-free heme is increased after RBC transfusion or HbV infusion, with the increase being greater after RBC transfusion than after HbV infusion. ^‡P < 0.05, The concentration of cell-free hemoglobin increased after RBC transfusion than after HbV infusion. Data shown are the mean ± standard deviation. HbV hemoglobin vesicles, HES hydroxyethyl starch, RBC red blood cell, RBC/PPP red blood cells with platelet-poor plasma.