Safety profile and efficacy of low and high oxygen affinity polymerized human hemoglobin in trauma model
Authors: Muller Cynthia R. , Courelli Vasiliki , Cuddington Clayton T. , Moses Savannah R. , Palmer Andre F. , Cabrales Pedro 
Published: May 2022

Hemoglobin (Hb)‐based O2 carriers (HBOC) are being developed as alternatives to blood. Large molecular weight polymerized human Hb (PolyhHb) represents a new class of HBOC with promising results. It has been shown that PolyhHb can be locked in the T‐state (low O2 affinity) or R‐state (high O2 affinity) to control and target O2 delivery and avoid damage. The present study hypothesized that PolyhHb’s quaternary state could differently affect safety and hemodynamics restoration, by controlling O2 distribution. Thus, we aimed to compare PolyhHb T‐state and R‐state to restore hemodynamics after trauma, and toxicity 24 hrs after resuscitation. To test the efficacy to restore hemodynamics, Wistar rats were instrumented with catheters in the femoral artery and vein, and subjected to TBI through a pneumatic controlled cortical impact. Hemorrhagic Shock (HS) was induced by blood withdrawal to achieve a mean arterial pressure (MAP) between 35‐40mmHg, and the hypotensive state was maintained for 90 min. Animals were separated into 3 groups based on the resuscitation solution: Blood, PolyhHb T‐state, or R‐state and, followed for 2 hrs after resuscitation. For toxicity evaluation guinea pigs (GP) (a more clinically relevant model due to lack of ascorbic acid production) were anesthetized and the carotid artery and jugular vein were catheterized, HS was induced by 40 % blood volume (BV) withdrawal, and the hypovolemic state was maintained for 50 min. GP was divided into 2 groups, and 25% of their BV was reinfused with PolyhHb T‐state or R‐state. Rats resuscitated with Blood and T‐state had a higher increase in MAP 30 min after resuscitation when compared to R‐state. Showing higher efficacy of T‐state to restore hemodynamics compared to R‐state. The T‐state group showed lower O2 saturation 30 min after reperfusion compared to R‐state and Blood groups. However, 2 hrs after resuscitation both the Blood and T‐state groups presented lower O2 saturation compared to R‐state. Resuscitation with R‐state in the GP increased AST, ALT, and liver chemokine ligand‐1 (CXCL1) (markers of liver damage and inflammation), suggesting that R‐state caused greater liver damage compared to T‐state. It was also observed an increase in the BUN, urine NGAL, and serum creatinine in the R‐state group compared to the T‐state group, showing an increased kidney injury in the animals resuscitated with R‐State PolyhHb. Also was observed higher levels of serum Il‐6, CXCL‐1, and Il‐10, in the R‐state group compared to the T‐State group, showing elevated inflammation in this group. Finally, was observed by increased levels of cardiac IL‐6, tumor necrosis factor‐alpha, monocyte chemoattractant protein‐1, troponin, and c‐reactive protein, higher cardiac damage in the R‐sate group when compared to the T‐state group. Our results showed that T‐state has higher efficacy on restoring hemodynamics in a model of TBI followed by HS, and also presented reduced vital organs toxicity in GP, when compared to R‐state. These results are promising and encourage the use of this new generation of PolyhHb T‐state as an alternative when blood is not available.