Human polymerized hemoglobin as an alternative to blood in resuscitation from hemorrhagic shock

Abstract

Hemoglobin (Hb) based oxygen carriers (HBOCs) have been developed as an alternative to blood. However, previous generations of HBOCs failed clinical trials due to toxicological and safety issues. High molecular weight (MW) polymerized human Hb (PolyhHb) has been recently tested with results that demonstrate reduced vasoconstriction and hypertension. Recently, it was observed that guinea pigs (GP) are a more clinically relevant model to test the safety of PolyHb due to a lack of ascorbic acid production, as humans present the same characteristics. Therefore, the present study aimed to evaluate the efficacy and safety of resuscitation from hemorrhagic shock (HS) with fresh blood, 2 weeks stored blood, and PolyhHb in a GP model. GP weighing between 300-400 were anesthetized. The carotid artery and jugular vein were catheterized. Hemorrhagic Shock (HS) was induced by 40 % blood volume (BV) withdrawal from the carotid artery (BV estimated as 7.5% of body weight) and the hypovolemic state was maintained for 50 minutes. After the 50 minutes into HS, GP were divided into three study groups, and 25% of their blood volume was reinfused with Fresh Blood (FB), Stored Blood (SB), or PolyhHb (n=6 animals/group). Mean arterial pressure (MAP), heart rate (HR), blood gasses, and hematocrit (Hct) were measured 15 minutes after resuscitation (R1), and animals were allowed to recover from anesthesia. Moreover, measurements were taken 2 hours (R2) and 24 hours (R3) after resuscitation, after R3 animals were euthanized and blood and tissues harvested. Markers of organs function and damage were evaluated. All groups decreased MAP equally during shock. At R3 MAP was equal between groups. HR was not different among groups. Hct decreased due to HS. FB presented higher Hct at R1 compared to the other groups, and Hct remained higher during R2 and R3. SB presented higher Hct than PolyhHb at R1 and R3. PolyhHb presented a lower total Hb than FB and SB at R3. There were no differences observed between groups in terms of pH, pO2, or pCO2 throughout the protocol. Lactate increased equally between groups, and lactate recovered to baseline for all groups after reperfusion. At R3 AST, ALP, and liver CXCL1 were increased on the SB group, but no differences were found on ALT, SOD, MDA, indicating that SB caused liver damage. SB and PolyhHb groups increased serum creatinine but no differences were found for BUN and UNgal. Serum IL-6 and CXCL1 were not different between groups, but SB presented higher IL-10 compared to all the other groups. Moreover, SB increased catecholamines and cardiac troponin at R3 suggesting cardiac damage. These results suggest that PolyhHb was as effective in recovering guinea pigs from HS as FB and SB, moreover, SB caused some degree of liver and cardiac damage, and increased catecholamines when PolyhHB seems to not have these same side effects. Therefore, these results are promising and encourage the use of this new generation of PolyhHb as an alternative when blood is not available. Furthermore, more experiments should be done to ensure PolyhHb safety before moving forward to a clinical trial.