Prehospital HBOC-201 after traumatic brain injury and hemorrhagic shock in swine

Cerebrovascular Response to Phenylephrine in Traumatic Brain Injury: A Scoping Systematic Review of the Human and Animal Literature

Intravenous phenylephrine (PE) is utilized commonly in critical care for cardiovascular support. Its impact on the cerebrovasculature is unclear and its use may have important implications during states of critical neurological illness. The aim of this study was to perform a scoping review of the literature on the cerebrovascular/cerebral blood flow (CBF) effects of PE in traumatic brain injury (TBI), evaluating both animal models and human studies. We searched MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and the Cochrane Library from inception to January 2020. We identified 12 studies with various animal models and 4 studies in humans with varying TBI pathology. There was a trend toward a consistent increase in mean arterial pressure (MAP) by the injection of PE systemically, and by proxy, an increase of the cerebral perfusion pressure (CPP). There was a consistent constriction of cerebral vessels by PE reported in the small number of studies documenting such a response. However, the heterogeneity of the literature on the CBF/cerebral blood volume (CBV) response makes the strength of the conclusions on PE limited. Studies were heterogeneous in design and had significant limitations, with most failing to adjust for confounding factors in cerebrovascular/CBF response. This review highlights the significant knowledge gap on the cerebrovascular/CBF effects of PE administration in TBI, calling for further study on the impact of PE on the cerebrovasculature both in vivo and in experimental settings.

Evaluation of prolonged 'Permissive Hypotension': results from a 6-hour hemorrhage protocol in swine

Background

Tactical Combat Casualty Care guidelines for hemorrhage recommend resuscitation to systolic blood pressure (SBP) of 85±5 mm Hg during prehospital care. Success depends on transport to definitive care within the ‘golden hour’. As future conflicts may demand longer prehospital/transport times, we sought to determine safety of prolonged permissive hypotension (PH).

Methods

Adult male swine were randomized into three experimental groups. Non-shock (NS)/normotensive underwent anesthesia only. NS/PH was bled to SBP of 85±5 mm Hg for 6 hours of prolonged field care (PFC) with SBP maintained via crystalloid, then recovered. Experimental group underwent controlled hemorrhage to mean arterial pressure 30 mm Hg until decompensation (Decomp/PH), followed by 6 hours of PFC. Hemorrhaged animals were then resuscitated with whole blood and observed for 24 hours. Physiologic variables, blood, tissue samples, and neurologic scores were collected.

Results

Survival of all groups was 100%. Fluid volumes to maintain targeted SBP in PFC were significantly higher in the hemorrhage group than sham groups. After 24 hours’ recovery, no significant differences were observed in neurologic scores or cerebrospinal fluid markers of brain injury. No significant changes in organ function related to treatment were observed during PFC through recovery, as assessed by serum chemistry and histological analysis.

Conclusions

After 6 hours, a prolonged PH strategy showed no detrimental effect on survival or neurologic outcome despite the increased ischemic burden of hemorrhage. Significant fluid volume was required to maintain SBP—a potential logistic burden for prehospital care. Further work to define maximum allowable time of PH is needed.

Study type

Translational animal model.

Level of evidence

N/A.

A systematic review of large animal models of combined traumatic brain injury and hemorrhagic shock

Traumatic brain injury (TBI) and severe blood loss (SBL) frequently co-occur in human trauma, resulting in high levels of mortality and morbidity. Importantly, each of the individual post-injury cascades is characterized by complex and potentially opposing pathophysiological responses, complicating optimal resuscitation and therapeutic approaches. Large animal models of poly-neurotrauma closely mimic human physiology, but a systematic literature review of published models has been lacking. The current review suggests a relative paucity of large animal poly-neurotrauma studies (N = 52), with meta-statistics revealing trends for animal species (exclusively swine), characteristics (use of single biological sex, use of juveniles) and TBI models. Although most studies have targeted blood loss volumes of 35-45%, the associated mortality rates are much lower relative to Class III/IV human trauma. This discrepancy may result from potentially mitigating experimental factors (e.g., mechanical ventilation prior to or during injury, pausing/resuming blood loss based on physiological parameters, administration of small volume fluid resuscitation) that are rarely associated with human trauma, highlighting the need for additional work in this area.

A novel cross-linked haemoglobin-based oxygen carrier is beneficial to sepsis in rats

Pathological hypoxia-induced organ dysfunction contributes to the high mortality of sepsis. Because of the microcirculation dysfunction following severe sepsis, it is difficult for erythrocytes to transport oxygen to hypoxic tissues. Haemoglobin-based oxygen carriers (HBOCs) are capable of delivering oxygen to hypoxic tissues. The aim of this study is to observe the potential benefits of a novel bovine-derived, non-polymerized, cell-free HBOC solution, YQ23, on sepsis in rats. Cecum ligation and puncture was performed to induce sepsis in Sprague-Dawley rats. Effects of Lactate Ringer's solution (LR), YQ23, and whole blood on oxygen delivery and consumption, mitochondrial function, organ protection and animal survival were observed. LR failed to restore oxygen delivery and the therapeutic effects were limited, whereas low dosage of YQ23 and whole blood significantly increased the tissue oxygen delivery and consumption, improved the mitochondrial function of heart, liver, kidney and intestine, prevented the vital organs injuries and improved the animal survival. The effects of 0.15 g·kg^-1 YQ23 resembled that of the whole blood. In addition, YQ23 did not induce renal toxicity, severe oxidative effect and acute vasoconstriction. Thus, YQ23 is a safe and effective resuscitation fluid for sepsis.

Current understanding of neuroinflammation after traumatic brain injury and cell-based therapeutic opportunities

Traumatic brain injury (TBI) remains a major cause of death and disability worldwide. Increasing evidence indicates that TBI is an important risk factor for neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and chronic traumatic encephalopathy. Despite improved supportive and rehabilitative care of TBI patients, unfortunately, all late phase clinical trials in TBI have yet to yield a safe and effective neuroprotective treatment. The disappointing clinical trials may be attributed to variability in treatment approaches and heterogeneity of the population of TBI patients as well as a race against time to prevent or reduce inexorable cell death. TBI is not just an acute event but a chronic disease. Among many mechanisms involved in secondary injury after TBI, emerging preclinical studies indicate that posttraumatic prolonged and progressive neuroinflammation is associated with neurodegeneration which may be treatable long after the initiating brain injury. This review provides an overview of recent understanding of neuroinflammation in TBI and preclinical cell-based therapies that target neuroinflammation and promote functional recovery after TBI.

Cerebral Vasoactivity and Oxygenation with Oxygen Carrier M101 in Rats

The severity of traumatic brain injury (TBI) may be reduced if oxygen can be rapidly provided to the injured brain. This study evaluated if the oxygen-carrier M101 causes vasoconstricton of pial vasculature in healthy rats (Experiment 1) and if M101 improves brain tissue oxygen (PbtO₂) in rats with controlled cortical impact (CCI)-TBI (Experiment 2). M101 (12.5 mL/kg intravenous [IV] over 2 h) caused a mild (9 mm Hg) increase in the mean arterial blood pressure (MAP) of healthy rats without constriction of cerebral pial arterioles. M101 (12 mL/kg IV over 1 h) caused a modest (27 mm Hg) increase in MAP (peak, 123 ± 5 mm Hg [mean ± standard error of the mean]) of CCI-TBI rats and restored PbtO₂ to near pre-injury levels. In both M101 and untreated control (NON) groups, PbtO₂ was ∼30 ± 2 mm Hg pre-injury and decreased (p ≤ 0.05) to ∼16 ± 2 mm Hg 15 min after CCI. In NON, PbtO₂ remained ∼50% of baseline but M101 administration resulted in a sustained increase in PbtO₂ (peak, 25 ± 5 mm Hg), which was not significantly different from pre-injury until the end of the study, when it decreased again below pre-injury (but was still higher than NON). Histopathology showed no differences between groups. In conclusion, M101 increased systemic blood pressures without concurrent cerebral pial vasoconstriction (in healthy rats) and restored PbtO₂ to 86% of pre-injury for at least 80 min when given soon after CCI-TBI. M101 should be evaluated in a clinically-relevant large animal model for pre-hospital treatment of TBI.

Storage of nitroglycerin (NTG) admixed with HBOC-201 for 30 days in polyolefin plastic bags: a pilot study

Hemorrhaged animals have benefited from resuscitation with the hemoglobin-based oxygen carrier (HBOC-201). Co-infusion of nitric oxide (NO) via separate intravascular lines is effective in attenuating HBOC-induced elevation of blood pressure. We tested whether nitroglycerin (NTG) and HBOC-201 can be packaged together as a single drug for resuscitation. Since NTG binds easily to plastics such as polyvinylchloride, we assessed the stability of this combination in oxygen barrier double-layer ethylene-vinyl alcohol/polyolefin bags over a 30-day period. Outcome measures indicative of the stability of HBOC/NTG were reported as changes in levels of hemoglobin (Hb), methemoglobin (MetHb), NTG, and nitrite over time. Individual tightly sealed small aliquots of HBOC/NTG were prepared under nitrogen and analyzed in a timely fashion from 0 to 30 days using hematology instruments, HPLC, FPLC, and chemiluminescence. The level of NTG in the HBOC/NTG mixture was reduced significantly over time whereas it was stable in control mixtures of NTG/saline. The level of total Hb in the HBOC/NTG and HBOC/saline mixtures remained stable over time. MetHb formed and increased to 6% up to day 1 and then slowly decreased in the HBOC/NTG mixture whereas it remained unchanged in the HBOC/saline mixture. Nitrite was produced in the HBOC/NTG group upon mixing, was increased at day 1, and then became undetectable. The reaction between HBOC-201 and NTG occurring upon mixing and developing over time in polyolefin bags makes the long-term storage of this mixed combination inappropriate.

Hemoglobin-Based Oxygen Carrier Rescues Double-Transplant Patient From Life-Threatening Anemia

This case describes a 46-year-old male recipient of a kidney-pancreas transplant who is Jehovah's Witness. Early in the postoperative period, he was found to have splenic vein thrombosis requiring heparin infusion. Two days later, he developed severe symptomatic anemia (hemoglobin <6 g/dL). Standard medical therapy for bloodless surgical patients with severe anemia was instituted. Nevertheless, the patient's hemoglobin concentration continued to decline to critical levels (2 g/dL). Because he was Jehovah's Witness, transfusion of allogeneic blood products was not an option, prompting use of a hemoglobin-based oxygen carrier (HBOC). After approval by the U.S. Food and Drug Administration and the local institutional review board, 12 U of HBOC-201 were transfused over a period of 8 days. Two weeks later, the patient's hemoglobin levels had increased to 6.8 g/dL. The patient's overall clinical condition improved, and he was discharged home. This case describes the first use of HBOC transfusion in a double solid organ transplant patient. HBOC may represent a viable option in patients with severe symptomatic anemia when allogeneic blood transfusion is not an option.

Combined hemorrhage/trauma models in pigs-current state and future perspectives

The majority of injury combinations in multiply injured patients entail the chest, abdomen, and extremities. Numerous pig models focus on the investigation of posttraumatic pathophysiology, organ performance monitoring and on potential treatment options. Depending on the experimental question, previous authors have included isolated insults (controlled or uncontrolled hemorrhage, chest trauma) or a combination of these injuries (hemorrhage with abdominal trauma, chest trauma, traumatic brain injury, and/or long-bone fractures). Combined trauma models in pigs can provide a high level of clinical relevance, when they are properly designed and mimicking the clinical situation. Most of these models focus on the first hours after trauma, to assess the acute sequel of traumatic hemorrhage. However, hemorrhagic shock and the associated mass transfusion are also major causes for organ failure and mortality in the later clinical course. Thus, most models lack information on the pathomechanisms during the late posttraumatic phase. Studying new therapies only during the early phase is also not reflective of the clinical situation. Therefore, a longer observation period is required to study the effects of therapeutic approaches during intensive care treatment when using animal models. These long-term studies of combined trauma models will allow the development of valuable therapeutic approaches relevant for the later posttraumatic course. This review summarizes the existing porcine models and outlines the need for long-term models to provide real effective novel therapeutics for multiply injured patients to improve organ function and clinical outcome.

Traumatic brain injury and severe uncontrolled haemorrhage with short delay pre-hospital resuscitation in a swine model

INTRODUCTION

Unavailability of blood (and oxygen delivery) for pre-hospital resuscitation in haemorrhagic shock patients are major problems, supporting the importance for novel resuscitation strategies. In a combined polytrauma model of uncontrolled haemorrhage and traumatic brain injury (TBI) in swine, we investigated if pre-hospital administration of the haemoglobin based oxygen carrier HBOC-201 will improve tissue oxygenation and physiologic parameters compared to Lactated Ringer's (LR) solution.

MATERIALS AND METHODS

Anaesthetised Yorkshire swine underwent fluid-percussion TBI and Grade III liver laceration. During a 30-min pre-hospital phase, the animals were resuscitated with a single infusion of HBOC-201, LR solution, or nothing (NON). Upon hospital arrival, the animals were given blood or normal saline as needed. Surviving animals were euthanised 6h post-injury. Cerebral blood flow was measured by microsphere injection, and pathology was assessed by gross observation and immunohistochemical analysis.

RESULTS

Mean TBI force (2.4±0.1atm) (means±standard error of the mean) and blood loss (22.5±1.7mL/kg) were similar between groups. Survival at the 6h endpoint was similar in all groups (∼50%). Cerebral perfusion pressure (CPP) and brain tissue oxygen tension were significantly greater in HBOC-201 as compared with LR animals (p<0.005). Mean arterial pressure (MAP) and mean pulmonary artery pressure (MPAP) were not significantly different amongst groups. Blood transfusion requirements were delayed in HBOC-201 animals. Animals treated with HBOC-201 or LR showed no immunohistopathological differences in glial fibrillary acidic protein (GFAP) and microtubule-associated protein 2 (MAP-2). Severity of subarachnoid and intraparenchymal haemorrhages were similar for HBOC and LR groups.

CONCLUSION

In this polytrauma swine model of uncontrolled haemorrhage and TBI with a 30-min delay to hospital arrival, pre-hospital resuscitation with one bolus of HBOC-201 indicated short term benefits in systemic and cerebrovascular physiological parameters. True clinical benefits of this strategy need to be confirmed on TBI and haemorrhagic shock patients.

Porcine model of hemorrhagic shock with microdialysis monitoring

BACKGROUND

A number of experimental protocols have been used to try to reproduce the clinical scenarios of hemorrhagic shock. The present study reports on an experimental swine model of controlled hemorrhagic shock that incorporates microdialysis monitoring for the evaluation of tissue perfusion and oxygenation. The aim of our study was to provide a reproducible, accurate, and reliable model for the testing and evaluation of therapeutic interventions in the area of hemorrhagic shock.

METHODS

Landrace swine (n = 8) were subjected to controlled hemorrhagic shock, with a mean arterial pressure of 35 ± 5 as the endpoint. Six more pigs were used as the control group. Microdialysis monitoring of the tissue lactate/pyruvate ratio was used. The mean arterial pressure, heart rate, hematocrit, hemoglobin, and lactate/pyruvate ratio measurements were obtained just before (phase A) and 30 min after (phase B) hemorrhage in the study group; the control group underwent the same measurements at the corresponding points.

RESULTS

The mean arterial pressure, hematocrit, and hemoglobin were lower (P < 0.05) in the study group than in the control group at phase B and compared with the values for the study group at phase A. Also, the lactate/pyruvate ratio and heart rate were greater (P < 0.05) in the study group than in control group at phase B and compared with the values for the study group at phase A.

CONCLUSIONS

This model of hemorrhagic shock is effective and correlates with the clinical parameters of tissue oxygenation, as documented by microdialysis.

Effects of a small acute subdural hematoma following traumatic brain injury on neuromonitoring, brain swelling and histology in pigs

An acute subdural hematoma (ASDH) induces pathomechanisms which worsen outcome after traumatic brain injury, even after a small hemorrhage. Synergistic effects of a small ASDH on brain damage are poorly understood, and were studied here using neuromonitoring for 10 h in an injury model of controlled cortical impact (CCI) and ASDH. Pigs (n = 32) were assigned to 4 groups: sham, CCI (2.5 m/s), ASDH (2 ml) and CCI + ASDH. Intracranial pressure was significantly increased above sham levels by all injuries with no difference between groups. CCI and ASDH reduced ptiO(2) by a maximum of 36 ± 9 and 26 ± 11%, respectively. The combination caused a 31 ± 11% drop. ASDH alone and in combination with CCI caused a significant elevation in extracellular glutamate, which remained increased longer for CCI + ASDH. The same two groups had significantly higher peak lactate levels compared to sham. Somatosensory evoked potential (SSEP) amplitude was persistently reduced by combined injury. These effects translated into significantly elevated brain water content and histological damage in all injury groups. Thus, combined injury had stronger effects on glutamate and SSEP when compared to CCI and ASDH, but no clear-cut synergistic effects of 2 ml ASDH on trauma were observed. We speculate that this was partially due to the CCI injury severity.

Pre-hospital resuscitation with HBOC-201 and rFVIIa compared to HBOC-201 alone in uncontrolled hemorrhagic shock in swine

In a previous dose escalation study our group found that combining 90μg/kg rFVIIa with HBOC-201 reduced blood loss and improved physiologic parameters compared to HBOC alone. In this follow-up study in a swine liver injury model, we found that while there were no adverse hematology effects and trends observed in the previous study were confirmed, statistical significance could not be reached. Additional pre-clinical studies are indicated to identify optimal components of a multifunctional blood substitute for clinical use in trauma.

Polynitroxylated pegylated hemoglobin: a novel neuroprotective hemoglobin for acute volume-limited fluid resuscitation after combined traumatic brain injury and hemorrhagic hypotension in mice

OBJECTIVE

Resuscitation of hemorrhagic hypotension after traumatic brain injury is challenging. A hemoglobin-based oxygen carrier may offer advantages. The novel therapeutic hemoglobin-based oxygen carrier, polynitroxylated pegylated hemoglobin (PNPH), may represent a neuroprotective hemoglobin-based oxygen carrier for traumatic brain injury resuscitation.

HYPOTHESES

1) PNPH is a unique non-neurotoxic hemoglobin-based oxygen carrier in neuronal culture and is neuroprotective in in vitro neuronal injury models. 2) Resuscitation with PNPH would require less volume to restore mean arterial blood pressure than lactated Ringer's or Hextend and confer neuroprotection in a mouse model of traumatic brain injury plus hemorrhagic hypotension.

DESIGN

Prospective randomized, controlled experimental study.

SETTING

University center.

MEASUREMENTS AND MAIN RESULTS

In rat primary cortical neuron cultures, control bovine hemoglobin was neurotoxic (lactate dehydrogenase release; 3-[4,5-dimethylthiazol-2-yl-]-2,5-diphenyltetrazolium bromide assay) at concentrations from 12.5 to 0.625 μM, whereas polyethylene glycol-conjugated hemoglobin showed intermediate toxicity. PNPH was not neurotoxic (p<.05 vs. bovine hemoglobin and polyethylene glycol hemoglobin; all concentrations). PNPH conferred neuroprotection in in vitro neuronal injury (glutamate/glycine exposure and neuronal stretch), as assessed via lactate dehydrogenase and 3-[4,5-dimethylthiazol-2-yl-]-2,5-diphenyltetrazolium bromide (all p<.05 vs. control). C57BL6 mice received controlled cortical impact followed by hemorrhagic hypotension (2 mL/100 g, mean arterial blood pressure ∼35-40 mm Hg) for 90 min. Mice were resuscitated (mean arterial blood pressure>50 mm Hg for 30 min) with lactated Ringer's, Hextend, or PNPH, and then shed blood was reinfused. Mean arterial blood pressures, resuscitation volumes, blood gasses, glucose, and lactate were recorded. Brain sections at 7 days were examined via hematoxylin and eosin and Fluoro-Jade C (identifying dying neurons) staining in CA1 and CA3 hippocampus. Resuscitation with PNPH or Hextend required less volume than lactated Ringer's (both p<.05). PNPH but not Hextend improved mean arterial blood pressure vs. lactated Ringer's (p<.05). Mice resuscitated with PNPH had fewer Fluoro-Jade C positive neurons in CA1 vs. Hextend and lactated Ringer's, and CA3 vs. Hextend (p<.05).

CONCLUSIONS

PNPH is a novel neuroprotective hemoglobin-based oxygen carrier in vitro and in vivo that may offer unique advantages for traumatic brain injury resuscitation.

Bovine blood and neuromuscular paralysis as a bridge to recovery in a patient with severe autoimmune hemolytic anemia

Hemoglobin solutions have several advantages as substitutes for erythrocyte transfusions. They have a prolonged shelf life, do not require cross-matching, are associated with few transfusion reactions, and are effective in delivering oxygen to the tissues. Despite the potential clinical utility of these solutions, they have not achieved widespread use. HbOC-201 (Hemopure, Biopure, Cambridge, MA, USA) is a bovine hemoglobin solution that has been FDA approved for compassionate use in Jehovah's witness patients requiring transfusions. Here we report a case of a patient with hemoglobin H disease who developed a severe life-threatening mixed warm and cold antibody mediated autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP) who was successfully treated with HbOC-201 as an adjunct to blood transfusion.

Hemoglobin-based oxygen carrier (HBOC-201) and escalating doses of recombinant factor VIIa (rFVIIa) as a novel pre-hospital resuscitation fluid in a swine model of severe uncontrolled hemorrhage

Exsanguinating hemorrhage and unavailability of blood are major problems in pre-hospital trauma care. We investigated if combining rFVIIa with HBOC-201 reduces blood loss and improves physiologic parameters compared to HBOC alone. Swine underwent liver injury and were resuscitated with HBOC-201 alone or HBOC+90, 180 or 360 μg/kg rFVIIa before hospital arrival at 240 min; animals survived to 72 hours. Blood loss was reduced; MAP, CI, transcutaneous oxygen saturation, and 72-hour survival improved in the 90 and 180 μg/kg rFVIIa groups. Lactate was cleared faster in the HBOC+rFVIIa 90 μg/kg group. Verification in a large, well-powered study is indicated.

Optimal fluid resuscitation: timing and composition of intravenous fluids

BACKGROUND

Recent data suggest that the timing of fluid resuscitation and the type of fluid used to treat hemorrhagic shock contribute to the inflammatory response as well as cell death.

METHODS

Rats were bled of 40% of their total blood volume and then resuscitated in either early or delayed fashion. Treatment was assigned randomly and consisted of lactated Ringer's solution, normal saline, bicarbonate Ringer's solution, hypertonic saline, or no resuscitation. The first four groups were subdivided into early and late resuscitation. After a 5-h observation period, lung and liver samples were evaluated for apoptosis, and blood was collected for measurements of the cytokines interleukin (IL)-6, IL-10, and IL-1beta.

RESULTS

The rats that were not resuscitated had significantly more apoptosis in liver tissue. In the lung, bicarbonate Ringer's solution, when given early, was associated with significantly less apoptosis. Non-resuscitated rats had significantly higher IL-6 concentrations than all other groups. Animals receiving hypertonic saline early had significantly higher IL-6 concentrations than those given any other fluid. The concentration of IL-1beta was significantly higher in the non-resuscitated rats than in those receiving bicarbonate Ringer's, lactated Ringer's, or normal saline for early resuscitation. Interleukin-10 was elevated significantly in non-resuscitated rats.

CONCLUSIONS

Cellular destruction and a pro-inflammatory response follow hemorrhagic shock. Early resuscitation with isotonic crystalloid fluids decreases these responses.

Innate Immune Responses in Swine Resuscitated from Severe Traumatic Hemorrhagic Shock with Hemoglobin-Based Oxygen Carrier-201

Hemoglobin-based oxygen carrier-201 transports oxygen and improves survival in swine with hemorrhagic shock, but has potential to be immune activating. Herein, we evaluated HBOC-201's immune effects in swine with more severe hemorrhagic shock due to soft tissue injury and 55% blood volume catheter withdrawal over 15 minutes followed by fluid resuscitation at 20 minutes with HBOC-201, Hextend, or no treatment (NON) before hospital arrival. Survival rates were similar with HBOC-201 and Hextend (p > 0.05), but were higher than in (p = 0.007). There were no significant group differences in blood cell count, percentages of leukocyte sub-populations and immunophenotype (CD4:CD8 ratio), adhesion markers expression (neutrophil CD11b; monocyte or neutrophil CD49d) and apoptosis. There was a trend to higher plasma IL-10 in HBOC-201 and groups vs. Hextend. We conclude that in swine with severe controlled HS and soft tissue injury, immune responses are similar with resuscitation with HBOC-201 and Hextend.

Glutaraldehyde-polymerized bovine hemoglobin and phosphodiesterase-5 inhibition

OBJECTIVE

Hemoglobin-based oxygen carriers (HBOC) of several types scavenge nitric oxide from the vasculature resulting in vasoconstriction and hypertension, both systemic and pulmonary. Phosphodiesterase-5 (PDE5) inhibitors promote nitric oxide activity and enhance vasodilation. The purpose of this study was to determine whether combined therapy of glutaraldehyde-polymerized bovine hemoglobin (HBOC) with a PDE5 inhibitor would counter the negative hemodynamic consequences of HBOC therapy alone, resulting in improved hemodynamics and oxygen delivery.

DESIGN

A controlled, experimental study.

SETTING

A research laboratory at a university.

SUBJECTS

Conscious male Sprague-Dawley rats.

INTERVENTIONS

Glutaraldehyde-polymerized bovine hemoglobin (HBOC), sildenafil (PDE5 inhibitor), and lactated Ringer's solution (control).

MEASUREMENTS AND MAIN RESULTS

Infusion of the HBOC resulted in significant (p < 0.05) systemic and pulmonary vasoconstriction, with reduced cardiac output and reduced oxygen delivery to the periphery. Infusion of lactated Ringer's demonstrated no changes in the measured variables. Infusion of sildenafil alone reduced systemic and pulmonary artery blood pressure, while maintaining cardiac output and oxygen delivery. Combined HBOC and sildenafil infusion resulted in stable systemic blood pressure, cardiac output, and oxygen delivery. However, the addition of sildenafil to HBOC did not fully ameliorate the pulmonary vasoconstriction caused by HBOC.

CONCLUSION

The HBOC used in this study resulted in pulmonary and systemic hypertension, reduced cardiac output, and oxygen delivery. These negative consequences of HBOC treatment can be largely overcome by combing HBOC treatment with a PDE5 inhibitor (sildenafil). Thus, these data support the continued investigation of combined HBOC and PDE5 inhibitor treatment in circumstances in which HBOC therapy is being considered.

Mixed S-nitrosylated polymerized bovine hemoglobin species moderate hemodynamic effects in acutely hypoxic rats

Hemoglobin (Hb)-based oxygen carriers (HBOCs) are being developed as a potential therapy for increasing tissue oxygenation, yet they have not reached their full potential because of unwanted hemodynamic side effects (vasoconstriction, low cardiac output, and oxygen delivery) due in part to nitric oxide (NO) scavenging by cell-free Hb. It may be possible to overcome the NO scavenging effect by coinfusing S-nitrosylated (SNO) HBOC along with unmodified HBOC. SNO-HBOC, like free Hb, may act as an NO donor in low-oxygen conditions. We hypothesized that an unaltered HBOC, polymerized bovine Hb (PBvHb), coinfused with an SNO-PBvHb, would improve hemodynamics and oxygen delivery during hypoxia. Vascular oxygen content and hemodynamics were determined after euvolemic rats were infused (3 ml) with lactated Ringer's solution, PBvHb, SNO-PBvHb, or PBvHb plus SNO-PBvHb (1:10) during normoxia or acute hypoxia (fraction of inspired oxygen = 10%, 120 min). Hemodynamic side effects resulting from PBvHb infusion (vasoconstriction, elevated pulmonary blood pressure, and reduced cardiac output) were offset by SNO-PBvHb in acute hypoxic, but not normoxic, conditions. These data support the potential use of HBOC mixed with SNO-HBOC for the treatment of conditions in which acute hypoxia is present, such as tumor oxygenation, wound healing, hemorrhagic trauma, and sickle cell and hemolytic anemia.

Hemoglobin Concentration and Cerebral Metabolism in Patients With Aneurysmal Subarachnoid Hemorrhage

Background and Purpose— The optimal hemoglobin (Hgb) target after aneurysmal subarachnoid hemorrhage is not precisely known. We sought to examine the threshold of Hgb concentration associated with an increased risk of cerebral metabolic dysfunction in patients with poor-grade subarachnoid hemorrhage.

Methods— Twenty consecutive patients with poor-grade subarachnoid hemorrhage who underwent multimodality neuromonitoring (intracranial pressure, brain tissue oxygen tension, cerebral microdialysis) were studied prospectively. Brain tissue oxygen tension and extracellular lactate/pyruvate ratio were used as markers of cerebral metabolic dysfunction and the relationship between Hgb concentrations and the incidence of brain hypoxia (defined by a brain tissue oxygen tension <20 mm Hg) and cell energy dysfunction (defined by a lactate/pyruvate ratio >40) was analyzed.

Results— Compared with higher Hgb concentrations, a Hgb concentration <9 g/dL was associated with lower brain tissue oxygen tension (27.2 [interquartile range, 21.2 to 33.1] versus 19.9 [interquartile range, 7.1 to 33.1] mm Hg, P =0.02), higher lactate/pyruvate ratio (29 [interquartile range, 25 to 38] versus 36 [interquartile range, 26 to 59], P =0.16), and an increased incidence of brain hypoxia (21% versus 52%, P <0.01) and cell energy dysfunction (23% versus 43%, P =0.03). On multivariable analysis, a Hgb concentration <9 g/dL was associated with a higher risk of brain hypoxia (OR, 7.92; 95% CI, 2.32 to 27.09; P <0.01) and cell energy dysfunction (OR, 4.24; 95% CI, 1.33 to 13.55; P =0.02) after adjusting for cerebral perfusion pressure, central venous pressure, PaO 2 /FIO 2 ratio, and symptomatic vasospasm.

Conclusions— A Hgb concentration <9 g/dL is associated with an increased incidence of brain hypoxia and cell energy dysfunction in patients with poor-grade subarachnoid hemorrhage.

HBOC-201: the multi-purpose oxygen therapeutic

Clinical and preclinical studies have revealed a diverse array of indications in which the effectiveness of HBOC-201 has been demonstrated or appears likely. Included among these are indications involving cardiac and peripheral ischaemia in which this oxygen therapeutic may prove to be an important tool in the armamentarium of the cardiologist and surgeon. Preclinical studies and clinical trials are under way to further delineate and optimise the role of HBOC-201 as an oxygen therapeutic in cardiovascular medicine.

Hemoglobin-based oxygen carrying compound-201 as salvage therapy for severe neuro- and polytrauma (Injury Severity Score = 27-41)

OBJECTIVE

A prehospital trial in trauma patients has been proposed to evaluate Hemopure (hemoglobin glutamer-250 [bovine], hemoglobin-based oxygen carrying compound [HBOC]-201, Biopure). We tested the hypothesis that HBOC-201 would improve cerebrovascular resuscitation in a unique polytrauma model.

DESIGN

Prospective, randomized, blinded animal study.

SUBJECTS

Thirty-two anesthetized swine (42 +/- 1 kg).

INTERVENTIONS

Blunt trauma to the head, right chest, and bilateral femurs (Injury Severity Score = 27-41) with captive bolt guns was followed by hypoventilation. Resuscitation was divided into phases to simulate conventional treatment in the prehospital, emergency room, and early intensive care unit. For 30-60 mins postinjury, 500 mL of either normal saline (control, n = 14) or HBOC-201 (n = 14) was administered. All received similar care thereafter. For 60-120 mins, normal saline maintained systolic arterial pressure >100 mm Hg and heart rate <100 beats/min plus mannitol (250 mg/kg) for intracranial hypertension. For 120-480 mins, phenylephrine, normal saline, and dextrose were administered to maintain cerebral perfusion pressure >70 mm Hg, filling pressure >12 mm Hg, and plasma glucose >60 mg%, respectively. Two formulations of HBOC-201 (average MW = 250 kDa) were tested: one with <3% 65 kDa tetramers (n = 7) and the other with <0.3% 65 kDa tetramers (n = 7).

MEASUREMENTS AND MAIN RESULTS

Injury severity is reflected by the death of 2 of 32 swine within 30 mins. In survivors (n = 30), systolic arterial pressure was 83 +/- 6 mm Hg, heart rate was 115 +/- 5 beats/min, and lactate was 5.8 +/- 0.4 mM. Intracranial pressure rose from 8 +/- 1 to 18 +/- 1 mm Hg and brain tissue PO2 fell from 17 +/- 1 to 2 +/- 1 mm Hg. Without immediate resuscitation, death occurred within 60 mins (n = 2). With normal saline resuscitation (n = 14), systemic hemodynamics, mixed venous oxygen, renal oxygen, portal oxygen, and muscle oxygen corrected but there were four deaths (two at 45 mins, one at 100 mins, and one at 200 mins). Cerebral perfusion pressure was not restored until mannitol and pressor therapy were initiated at 120 mins. In contrast, with HBOC-201 at 30 mins (n = 14), systolic arterial pressure and cerebral perfusion pressure corrected immediately (both p < 0.05) and there were no deaths (p = 0.0978). After 8 hrs, in both groups, cerebral perfusion pressure, systolic arterial pressure, and heart rate were stable; peripheral oxygen saturations were near normal; lactate was cleared; urine output was adequate. However, with HBOC-201, pressor and fluid requirements were reduced by half, which improved intracranial pressure and brain tissue PO2 (all p < 0.05 vs. control). Reducing tetramer content had no significant effect on the actions of HBOC-201.

CONCLUSIONS

1) A single bolus of HBOC-201 at initial resuscitation rapidly restored cerebral perfusion pressure and stabilized hemodynamics with improved intracranial pressure and brain oxygen for the first 8 hrs; and 2) HBOC-201 could be an effective salvage therapy after severe neurotrauma or as a temporizing measure during prolonged transport of a polytrauma patient.

Resuscitation from hemorrhagic shock with HBOC-201 in the setting of traumatic brain injury

Outcomes after mild or moderate head trauma are worsened with associated hypotension, and secondary brain injury can be reduced with timely resuscitation. This study was performed to investigate HBOC-201 as a resuscitation therapy in a combined hemorrhagic shock and brain injury model. Anesthetized rats sustained moderate brain injury using a controlled cortical impact device, followed by rapid hemorrhage to a mean arterial pressure of 30 mmHg. After 30 min of hypotension, animals were resuscitated with HBOC-201, autologous shed blood (SB), or lactated Ringer solution (LR). Brain injury was assessed by measurements of cerebral blood flow (CBF) and cerebral vasoreactivity to hypercapnia (CVH) using a laser Doppler flowmeter. Contusion volume was evaluated histologically, and cerebral edema was determined by total water content. The HBOC rats required significantly less resuscitation volume versus LR and SB. The CBF was significantly diminished at 60 min after resuscitation with HBOC (70.1% +/- 3.8% baseline) compared with LR (105.8% +/- 10.1% baseline; P < 0.01) and SB (96.8% +/- 5% baseline; P < 0.05). The CVH was preserved in the HBOC and SB groups. The CVH was significantly diminished compared with baseline in the LR group at 30 min after resuscitation and showed a significant loss compared with HBOC at 60 min after resuscitation. The contusion volume for HBOC (45.1 mm3) and SB (35.1 mm3) was less than LR (63.5 mm3, P < 0.01). Although CBF was diminished after resuscitation in the HBOC group, HBOC-treated animals maintained CVH and experienced significantly smaller contusion volume than those treated with LR. These results suggest that resuscitation with HBOC-201 protects autoregulatory mechanisms and may reduce secondary brain injury in traumatic brain injury.

Resuscitation following severe, controlled hemorrhage associated with a 24 h delay to surgical intervention in swine using a hemoglobin based oxygen carrier as an oxygen bridge to definitive care

OBJECTIVES

To test our hypothesis that the hemoglobin based oxygen carrier HBOC-201 would have similar or superior efficacy to 6% hetastarch (HEX) as a pre-hospital 'bridging' fluid for hemorrhagic shock when delay to definitive medical care is prolonged to 24h.

METHODS

Twenty-four pigs were anesthetized, instrumented, given a soft tissue injury, and bled 55% estimated blood volume. Pigs were randomized to receive HBOC-201, HEX, or no resuscitation fluids (NON). At 4h post-injury, surgical sites were repaired and pigs were recovered from anesthesia. Animals were non-invasively monitored, administered blood for anemia or saline for hypotension at 24 and 48h, and monitored for 72h.

RESULTS

Survival to 72h was 87.5% (7/8) in HBOC-201 and HEX pigs compared to 25% (2/8) in NON pigs (p=0.01). Increased mean arterial pressure was observed in the HBOC-201 group (p<0.0001). Cardiac index was highest in HEX pigs (overall p<0.001, HBOC-201 versus HEX p=0.002). Transcutaneous tissue oxygenation was higher with HBOC-201 (overall p=0.04, HBOC-201 versus HEX p<0.01). HBOC-201 and HEX pigs had comparable heart rates, pulmonary pressures, pre-hospital fluid requirements, venous O(2) saturation, base deficit, and lactic acid. Hemoglobin was decreased with HEX (overall p<0.0001, HBOC-201 versus HEX p<0.0002). At 24h, 14.3% (1/7) HBOC-201 pigs required blood transfusions versus 100% HEX (7/7) and NON (2/2) pigs (p>0.001).

CONCLUSIONS

HBOC-201 restored hemodynamics, maintained tissue oxygenation, and decreased blood transfusions in comparison to HEX in severe controlled HS with 24h delay to simulated hospital care. These results support the potential use of HBOC-201 as a bridging resuscitation fluid for HS.