Cardiovascular Effects of Polymerized Hemoglobin in a Dyslipidemia Model

The need for alternatives to allogeneic red blood cells (RBCs) for transfusion medicine has been recognized for more than a century. Large molecular size polymerized human hemoglobin (Hb) (PolyhHb) is a Hb based oxygen (O2) carrier (HBOC) recently evaluated with promising results in efficient O2 delivery and minimal toxicity. Despite significant commercial development, late stage clinical results of HBOC solutions hampered development. To evaluate the safety of PolyhHb as an O2 therapeutic agent in a vulnerable population, the present study was performed in a guinea pigs subjected to a high fat and high sucrose diet (HDHS). This model mimics human dyslipidemia and potentially induces endothelial dysfunction (ED). The objective of this study was to evaluate the impact of large molecular size PolyhHb on cardiovascular function in guinea pigs with dyslipidemia. Animals weighing between 150–200 g were fed a HDHS for 12 weeks. The metabolic characterization of the model included glucose tolerance testing (GTT) and measurement of the lipid profile. After metabolic characterization, the carotid artery and jugular vein were catheterized and catheters were exteriorized dorsally. Then, PolyhHb (n = 5) was subjected to a 20% blood volume (BV) exchange‐transfusion (BV estimated as 7.5% of body weight) with PolyhHb at 10 g/dL. Sham (n = 5) was subjected to the same procedure, but no exchange transfusion was performed. Post exchange, the animals were allowed to recover for 24 hours, after which blood pressure (BP) and heart rate (HR) were recorded, and BP and HR variability (HRV) were evaluated by spectral analysis. Animals were subjected to a sequence of vasoactive drugs to evaluate their baroreflex (phenylephrine, sodium nitroprusside, 1 and 2 ug), endothelial function (acethocoline (ACH), 2 and 4 ug), and nitric oxide response (Nitro‐L‐arginine methyl ester (L‐NAME), 12 mg/kg). Animals presented glucose intolerance and dyslipidemia. PolyhHb induced an 18% increase in MAP 24 hours after exchange‐transfusion. PolyhHb showed a decreased response to L‐NAME, suggesting a deficiency in nitric oxide (NO) dependent regulation of vascular tone, a known consequence of acellular Hb NO scavenging. There were no differences in baroreflex between groups nor significant endothelial dysfunction for the PolyhHb group compared to the Sham group. An increase in HRV and in sympathetic nervous system (SNS) modulation of the heart (low frequency band, LF) was observed in the PolyhHb group compared to Sham. On the other hand, parasympathetic modulation of the heart (high frequency band, HF) was decreased for the PolyhHb group compared to Sham, culminating in a 2‐fold increase in sympathetic vagal balance. Moreover, BP variability as well as blood vessel SNS modulation was increased for PolyhHb compared to Sham. In conclusion, PolyhHb transfusion impaired the autonomic nervous system in guinea pigs with dyslipidemia. Our results suggest that dyslipidemic patients might be more vulnerable to PolyhHb transfusion side effects.Support or Funding InformationThis work was supported by the NIH Heart Lung and Blood Institute under Grants T32‐HL105373, R01‐HL126945, and the DOD DMRDP under Grant W81XWH‐18‐1‐0059