Bovine polymerized hemoglobin (hemoglobin-based oxygen carrier-201) resuscitation in three swine models of hemorrhagic shock with militarily relevant delayed evacuation--effects on histopathology and organ function

A novel animal model to study delayed resuscitation following traumatic hemorrhage

A focus of combat casualty care research is to develop treatments for when full resuscitation after hemorrhage is delayed. However, few animal models exist to investigate such treatments. Given the kidney's susceptibility to ischemia, we determined how delayed resuscitation affects renal function in a model of traumatic shock. Rats were randomized into three groups: resuscitation after 1 h (ETH-1) or 2 h (ETH-2) of extremity trauma and hemorrhagic shock, and sham control. ETH was induced in anesthetized rats with muscle injury and fibula fracture, followed by pressure-controlled hemorrhage [mean arterial pressure (MAP) = 55 mmHg] for 1 or 2 h. Rats were then resuscitated with whole blood until MAP stabilized between 90 and 100 mmHg for 30 min. MAP, glomerular filtration rate (GFR), creatinine, blood gases, and fractional excretion of sodium (nFENa+) were measured for 3 days. Compared with control, ETH-1 and ETH-2 exhibited decreases in GFR and nFENa+, and increases in circulating lactate, creatinine, and blood urea nitrogen (BUN) before and within 30 min after resuscitation. The increases in creatinine, BUN, and potassium were greater in ETH-2 than in ETH-1, whereas lactate levels were similar between ETH-1 and ETH-2 before and after resuscitation. All measurements were normalized in ETH-1 within 2 days after resuscitation, with 22% mortality. However, ETH-2 exhibited a prolonged impairment of GFR, increased nFENa+, and a 66% mortality. Resuscitation 1 h after injury therefore preserves renal function, whereas further delay of resuscitation irreversibly impairs renal function and increases mortality. This animal model can be used to explore treatments for prolonged prehospital care following traumatic hemorrhage.NEW & NOTEWORTHY A focus of combat casualty care research is to develop treatment where full resuscitation after hemorrhage is delayed. However, animal models of combat-related hemorrhagic shock in which to determine physiological outcomes of such delays and explore potential treatment for golden hour extension are lacking. In this study, we filled this knowledge gap by establishing a traumatic shock model with reproducible development of AKI and shock-related complications determined by the time of resuscitation.

New Applications of HBOC-201: A 25-Year Review of the Literature

If not cured promptly, tissue ischemia and hypoxia can cause serious consequences or even threaten the life of the patient. Hemoglobin-based oxygen carrier-201 (HBOC-201), bovine hemoglobin polymerized by glutaraldehyde and stored in a modified Ringer's lactic acid solution, has been investigated as a blood substitute for clinical use. HBOC-201 was approved in South Africa in 2001 to treat patients with low hemoglobin (Hb) levels when red blood cells (RBCs) are contraindicated, rejected, or unavailable. By promoting oxygen diffusion and convective oxygen delivery, HBOC-201 may act as a direct oxygen donor and increase oxygen transfer between RBCs and between RBCs and tissues. Therefore, HBOC-201 is gradually finding applications in treating various ischemic and hypoxic diseases including traumatic hemorrhagic shock, hemolysis, myocardial infarction, cardiopulmonary bypass, perioperative period, organ transplantation, etc. However, side effects such as vasoconstriction and elevated methemoglobin caused by HBOC-201 are major concerns in clinical applications because Hbs are not encapsulated by cell membranes. This study summarizes preclinical and clinical studies of HBOC-201 applied in various clinical scenarios, outlines the relevant mechanisms, highlights potential side effects and solutions, and discusses the application prospects. Randomized trials with large samples need to be further studied to better validate the efficacy, safety, and tolerability of HBOC-201 to the extent where patient-specific treatment strategies would be developed for various clinical scenarios to improve clinical outcomes.

Microvascular and Systemic Impact of Resuscitation with PEGylated Carboxyhemoglobin-Based Oxygen Carrier or Hetastarch in a Rat Model of Transient Hemorrhagic Shock

BACKGROUND

Hemorrhage is the leading cause of preventable, traumatic death. Currently, prehospital resuscitation fluids provide preload but not oxygen-carrying capacity-a critical blood function that mitigates microvascular ischemia and tissue hypoxia during hemorrhagic shock. Solutions containing polymerized hemoglobin have been associated with vasoactive and hypertensive events. A novel hemoglobin-based oxygen carrier, modified with PEGylation and CO moieties (PEG-COHb), may overcome these limitations.

OBJECTIVES

To evaluate the systemic and microcirculatory effects of PEG-COHb as compared with the 6% hetastarch in a rat model of hemorrhagic shock.

METHODS

Male Sprague Dawley rats (N = 20) were subjected to severe, controlled, hemorrhagic shock. Animals were randomized to 20% estimated blood-volume resuscitation with either 6% hetastarch or PEG-COHb. Continuous, invasive, cardiovascular measurements, and arterial blood gases were measured. Microcirculatory measurements of interstitial oxygenation (PISFO2) and vasoactivity helped model oxygen delivery in the spinotrapezius muscle using intravital and phosphorescence quenching microscopy.

RESULTS

Hemorrhage reduced mean arterial pressure (MAP), arteriolar diameter, and PISFO2, and increased lactate 10-fold in both groups. Resuscitation with both PEG-COHb and hetastarch improved cardiovascular parameters. However, PEG-COHb treatment resulted in higher MAP (P < 0.001), improved PISFO2 (14 [PEG-COHb] vs. 5 [hetastarch] mmHg; P < 0.0001), lower lactate post-resuscitation (P < 0.01), and extended survival from 90 to 142 min (P < 0.001) as compared with the hetastarch group.

CONCLUSIONS

PEG-COHb improved MAP PISFO2, lactate, and survival time as compared with 6% hetastarch resuscitation. Importantly, hypertension and vasoactivity were not detected in response to PEG-COHb resuscitation supporting further investigation of this resuscitation strategy.

Fluids for Prevention and Management of Acute Kidney Injury

Fluids are the only known method of attenuating renal injury. Furthermore, whether for hydration, resuscitation or renal replacement therapy, fluid prescriptions must be tailored to the fluid and electrolyte, cardiovascular status and residual renal function of the patient. Different fluids have significantly different effects both on volume expansion as well as on the electrolyte and acid-base balance; while controversial, different fluids may even influence renal function differently. This systematic review focuses on fluids for prevention and management of acute kidney injury. We have reviewed the available evidence and have made recommendations for clinical practice and future studies.

Beneficial effects of novel cross-linked hemoglobin YQ23 on hemorrhagic shock in rats and pigs

BACKGROUND

To overcome the problems of previously reported hemoglobin-based oxygen carriers, we developed a stabilized nonpolymeric cross-linked tetrameric hemoglobin solution (YQ23). The aims of this study were to investigate the oxygen carrying and releasing properties of this novel hemoglobin-based oxygen carrier and to determine whether it has beneficial effects for hemorrhagic shock.

METHODS

Using a hemorrhagic shock model in Sprague-Dawley rats and mini-pigs, we tested the effects of infusing 0.1, 0.3, and 0.5 g/kg YQ23 on animal survival, tissue oxygen delivery (DO₂) and consumption (VO₂), hemodynamics parameters, and liver, renal, and cardiac function.

RESULTS

YQ23 infusion increased the survival rate of rats and pigs with severe hemorrhagic shock in a dose-dependent manner. Moreover, it improved the hemodynamic parameters, cardiac output, DO₂ and VO₂, and the mitochondrial respiratory function of vital organs. Among the three doses of YQ23, 0.5 gHb/kg YQ23 achieved a similar beneficial effect as whole blood.

CONCLUSIONS

This study indicated that the novel cross-linked tetrameric hemoglobin YQ23 has good oxygen carrying and releasing properties and exhibits beneficial effects on hemorrhagic shock in rats and pigs by improving the oxygen carrying and delivery function of blood, which maintains organ function.

Fluid resuscitation of uncontrolled hemorrhage using a hemoglobin-based oxygen carrier: effect of traumatic brain injury

Animal models of combined traumatic brain injury (TBI) and hemorrhagic shock (HS) suggest a benefit of hemoglobin-based oxygen carrier (HBOC)-based resuscitation, but their use remains controversial, and little is known of the specific effects of TBI and high-pressure (large arterial injury) bleeding on resuscitation. We examine the effect of TBI and aortic tear injury on low-volume HBOC resuscitation in a swine polytrauma model and hypothesize that HBOC-based resuscitation will improve survival in the setting of aortic tear regardless of the presence of TBI. Anesthetized swine subjected to HS with aortic tear with or without fluid percussion TBI underwent equivalent limited resuscitation with HBOC, lactated Ringer's solution, or HBOC + nitroglycerine (vasoattenuated HBOC) and were observed for 6 h. There was no independent effect of TBI on survival time after adjustment for fluid type, and there was no interaction between TBI and resuscitation fluid type. However, total catheter hemorrhage volume required to reach target shock blood pressure was less with TBI (14.0 mL · kg(-1) [confidence interval, 12.4-15.6 mL · kg(-1)]) versus HS only (21.0 mL · kg(-1) [confidence interval, 19.5-22.5 mL · kg(-1)]), with equivalent lactate accumulation. Traumatic brain injury did not affect survival in this polytrauma model, but less hemorrhage was required in the presence of TBI to achieve an equivalent degree of shock suggesting globally impaired cardiovascular response to hemorrhage in the presence of TBI. There was also no benefit of HBOC-based fluid resuscitation over lactated Ringer's solution, contrary to models using liver injury as the source of hemorrhage, considering wound location is of paramount importance when choosing resuscitation strategy.

Resuscitation after hemorrhagic shock: the effect on the liver--a review of experimental data

The liver is currently considered to be one of the first organs to be subjected to the hypoxic insult inflicted by hemorrhagic shock. The oxidative injury caused by resuscitation also targets the liver and can lead to malfunction and the eventual failure of this organ. Each of the various fluids, vasoactive drugs, and pharmacologic substances used for resuscitation has its own distinct effect(s) on the liver, and the anesthetic agents used during surgical resuscitation also have an impact on hepatocytes. The aim of our study was to identify the specific effect of these substances on the liver. To this end, we conducted a literature search of MEDLINE for all types of articles published in English, with a focus on articles published in the last 12 years. Our search terms were "hemorrhagic shock," "liver," "resuscitation," "vasopressors," and "anesthesia." Experimental studies form the majority of articles found in bibliographic databases. The effect of a specific resuscitation agent on the liver is assessed mainly by measuring apoptotic pathway regulators and inflammation-induced indicators. Apart from a wide range of pharmacological substances, modifications of Ringer's Lactate, colloids, and pyruvate provide protection to the liver after hemorrhage and resuscitation. In this setting, it is of paramount importance that the treating physician recognize those agents that may attenuate liver injury and avoid using those which inflict additional damage.

The effect HBOC-201 and sodium nitrite resuscitation after uncontrolled haemorrhagic shock in swine

BACKGROUND

Development of Haemoglobin-based oxygen carriers (HBOCs) as blood substitutes has reached an impasse due to clinically adverse outcomes attributed to vasoconstriction secondary to nitric oxide (NO) scavenging. Studies suggest haemoglobin exhibits nitrite reductase activity that generates NO and N(2)O(3); harnessing this property may offset NO scavenging. Therefore, the effects of concomitantly infusing sodium nitrite (NaNO(2)) with HBOC-201 were investigated.

METHODS

Swine underwent uncontrolled liver haemorrhage before receiving up to three 10min 10ml/kg infusions of HBOC-201 (HBOC) with or without concurrent NaNO(2) (5.4μmol/kg [LD NaNO(2)] or 10.8μmol/kg [HD NaNO(2)]) or 6% Hetastarch (HEX) with or without HD NaNO(2) during "prehospital" resuscitation (15, 30 and 45min after injury). Definitive surgical care occurred at 75min; anaesthetic recovery at 120min. Animals were euthanised at 72h.

RESULTS

NaNO(2) temporarily reduced systemic and pulmonary blood pressure increases from HBOC in a dose-dependent fashion. There was no significant effect between groups in indices of tissue oxygenation or survival. Adverse clinical signs requiring humane euthanasia occurred with highest frequency after HBOC+HD NaNO(2) (3 of 4 pigs) and HBOC+LD NaNO(2) (2 of 4 pigs). Gross evidence of pulmonary congestion was observed in 5 of 8 swine receiving a HBOC and NaNO(2) combination compared to 1 of 16 swine receiving HBOC alone, HEX alone, or HEX+NaNO(2). Gross lesions correlated with histological evidence of pulmonary oedema and congestion, and in 2 of 4 HBOC+HD NaNO(2) pigs, pulmonary fibrin thrombi also were found. No other pig had similar evidence of thrombi. Asymmetric pre-resuscitation cardiac index was a potential confounder.

CONCLUSIONS

A significant interaction between NaNO(2) and HBOC-201 ameliorated HBOC-201 vasoconstrictive effects, consistent with HBOC possessing a nitrite reductase activity that generates vasodilator NO equivalents. Results were relatively equivalent in survival and markers of tissue oxygenation. The highest dose of NaNO(2) was the most effective in reducing HBOC-associated pulmonary and systemic vasoactivity but also with the highest incidence of adverse events. In this model, the transient nature of NaNO(2) in off-setting HBOC-201 vasoconstriction makes it less clinically promising than anticipated and the combination of NaNO(2) and HBOC appear to increase the risk of pulmonary complications in a dose-dependent fashion independently of haemodilutional effects on haemostatic components.

Vital organ tissue oxygenation after serial normovolemic exchange transfusion with HBOC-201 in anesthetized swine

This study determined the effects of serial, normovolemic, stepwise exchange transfusions with either 6% human serum albumin (HSA) or the hemoglobin-based oxygen carrier, HBOC-201, on tissue oxygenation of the heart, brain, and kidney in intact anaesthetized pigs. Exchange transfusions to 10%, 30%, and 50% of the pigs' total blood volume were completed at a withdrawal rate of 1.0 mL·kg(-1)·min(-1) followed by an infusion rate of 0.5 mL·kg(-1)·min(-1) of HBOC-201 or iso-oncotically matched 6% HSA. Measurements included invasive systemic hemodynamic (blood pressures, left ventricular end-diastolic pressure), hematolic (hemoglobin, hematocrit, methemoglobin), acid-base (pH, PCO2), and biochemistry (serum lactate) measurements. Brain and kidney tissue oxygenation (tPO2) was determined by electron paramagnetic resonance and heart tPO2 by O2 sensitive fiberoptic probe. The main results demonstrated that tPO2 after HBOC-201 remained stable despite significant decreases in hematocrit and changing hemodynamics. In vivo tPO2 measurements (heart tPO2 average ≥22 mmHg, brain tPO2 average ≥8 mmHg, and kidney tPO2 average ≥10 mmHg) were maintained in all groups at all times. Blood pressures were 20 to 30 mmHg higher after HBOC-201 compared with HSA controls. Heart rate and left ventricular end-diastolic pressure were not different among treatment groups. In conclusion, the administration of HBOC-201 maintained tPO2 in three vital organs after profound hemodilution.

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.

Fluid resuscitation: past, present, and the future

Hemorrhage remains a major cause of preventable death following both civilian and military trauma. The goals of resuscitation in the face of hemorrhagic shock are restoring end-organ perfusion and maintaining tissue oxygenation while attempting definitive control of bleeding. However, if not performed properly, resuscitation can actually exacerbate cellular injury caused by hemorrhagic shock, and the type of fluid used for resuscitation plays an important role in this injury pattern. This article reviews the historical development and scientific underpinnings of modern resuscitation techniques. We summarized data from a number of studies to illustrate the differential effects of commonly used resuscitation fluids, including isotonic crystalloids, natural and artificial colloids, hypertonic and hyperoncotic solutions, and artificial oxygen carriers, on cellular injury and how these relate to clinical practice. The data reveal that a uniformly safe, effective, and practical resuscitation fluid when blood products are unavailable and direct hemorrhage control is delayed has been elusive. Yet, it is logical to prevent this cellular injury through wiser resuscitation strategies than attempting immunomodulation after the damage has already occurred. Thus, we describe how some novel resuscitation strategies aimed at preventing or ameliorating cellular injury may become clinically available in the future.

Toxicological consequences of extracellular hemoglobin: biochemical and physiological perspectives

Under normal physiology, human red blood cells (RBCs) demonstrate a circulating lifespan of approximately 100-120 days with efficient removal of senescent RBCs taking place via the reticuloendothelial system, spleen, and bone marrow phagocytosis. Within this time frame, hemoglobin (Hb) is effectively protected by efficient RBC enzymatic systems designed to allow for interaction between Hb and diffusible ligands while preventing direct contact between Hb and the external environment. Under normal resting conditions, the concentration of extracellular Hb in circulation is therefore minimal and controlled by specific plasma and cellular (monocyte/macrophage) binding proteins (haptoglobin) and receptors (CD163), respectively. However, during pathological conditions leading to hemolysis, extracellular Hb concentrations exceed normal plasma and cellular binding capacities, allowing Hb to become a biologically relevant vasoactive and redox active protein within the circulation and at extravascular sites. Under conditions of genetic, drug-induced, and autoimmune hemolytic anemias, large quantities of Hb are introduced into the circulation and often lead to acute renal failure and vascular dysfunction. Interestingly, the study of chemically modified Hb for use as oxygen therapeutics has allowed for some basic understanding of extracellular Hb toxicity, particularly in the absence of functional clearance mechanisms and in circulatory antioxidant depleted states.

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.

A double blind, single centre, sub-chronic reperfusion trial evaluating FX06 following haemorrhagic shock in pigs

OBJECTIVE

Haemorrhagic shock causes ischaemia and subsequent fluid resuscitation causes reperfusion injury, jointly resulting in high morbidity and mortality. We tested whether the anti-inflammatory fibrin-derived peptide, Bbeta(15-42), also called FX06, is tissue protective in a model of haemorrhagic shock.

METHODS

In a pig model, we standardised the severity of haemorrhagic shock by achieving a cumulative oxygen deficit of approximately 100ml/kg body weight by withdrawing blood over a period of 1h. This was followed by resuscitation with shed blood and full electrolyte solution, and pigs were monitored for 3 days. At reperfusion, 17 pigs were randomly assigned to FX06 or solvent treatment.

RESULTS

FX06-treated pigs demonstrated improved cardiac function (stroke volume index: 67ml/m(2) versus 33ml/m(2)), decreased troponin T release in the early reperfusion (0.24ng/ml versus 0.78ng/ml), decreased AST levels after 24h (106U/l versus 189U/l) and decreased creatinine levels after 24h (108micromol/l versus 159micromol/l). Furthermore, FX06-treated pigs demonstrated preservation of the gut/blood barrier, while controls demonstrated high endotoxin plasma levels indicating translocation of bacteria and/or its products (0.2EU/ml versus 24.3EU/ml) after 24h. This study also demonstrates a significantly improved neurological performance in the FX06 group as determined by S100beta serum levels (0.72microg/l versus 1.25microg/l) after 48h and neurological deficit scores (11 versus 70) after 24h.

CONCLUSION

FX06 - when administered as an adjunct to fluid resuscitation therapy - is organ protective in pigs. Further investigations are warranted to reveal the protective mechanism of FX06.

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.

The effects of decreasing low-molecular weight hemoglobin components of hemoglobin-based oxygen carriers in swine with hemorrhagic shock

BACKGROUND

Some hemoglobin-based oxygen carriers (HBOCs) improve outcome in animal models of hemorrhagic shock (HS) in comparison with standard asanguinous resuscitation fluids. Nevertheless, concern about intrinsic vasoactivity, linked in part to low-molecular weight (MW) hemoglobin (Hb), has slowed HBOC development. We assessed the impact of decreasing the low-MW Hb component of bovine HBOC on vasoactivity in severe HS.

METHODS

Anesthetized invasively monitored swine were hemorrhaged 55% blood volume and resuscitated with bovine HBOC containing 31% (31 TD [HBOC-301]), 2% (2 TD [HBOC-201]), or 0.4% (0.4 TD) low-MW Hb. Pigs received four 10 mL/kg infusions over 60 minutes, hospital arrival was simulated at 75 minutes, organ blood flow (BF) was evaluated by microsphere injection, and monitoring was continued for 4 hours followed by complete necrotic evaluation.

RESULTS

There were few differences between 2 TD and 0.4 TD. Thirty-one TD pigs had higher systemic and pulmonary blood pressure (BP), systemic vascular resistance index, and pulmonary artery wedge pressure, compared with 2 TD or 0.4 TD (p < 0.01); however, pigs in all groups had at least mildly elevated BP. Transcutaneous tissue oxygenation, base excess, and mixed venous oxygen saturation were similar across groups; lactate and methemoglobin were highest with 0.4 TD (p < 0.03). There were no group differences in BF. Over time, myocardial BF increased and hepatic BF decreased in all groups (for 31 TD, p < 0.05); renal BF was unchanged in all groups. There were no group differences in heart, lung, or liver histopathology, and survival.

CONCLUSIONS

Although purification from 31% to 2% low-MW Hb content significantly decreased vasoactive responses, further purification to 0.4% had no additional clinically measurable effects in severe HS. If further diminution in HBOC vasoactivity is desired for use in HS, additional technical approaches may be required.

Vasoactivity of Bovine Polymerized Hemoglobin (HBOC-201) in Swine With Traumatic Hemorrhagic Shock With and Without Brain Injury

BACKGROUND

We previously reported that bovine polymerized hemoglobin (HBOC- 201) improved outcome in swine with hemorrhagic shock (HS) with and without traumatic brain injury (TBI). Herein, we add analyses of blood pressure (BP) responses, associated physiologic data, and HS fluid infusion guidelines.

METHODS

HBOC-201 versus standard fluid resuscitation was compared in four anesthetized invasively monitored swine models: moderate controlled HS, severe controlled HS, severe uncontrolled HS (liver injury), and severe uncontrolled HS/TBI (liver/parietal brain injuries). Pigs received fluid for hypotension and tachycardia, and were followed up to 6 (HS alone) or 72 hours (HS/TBI). The change in mean arterial pressure (DeltaMAP) response severity was stratified and analyzed based on infusion number and HS severity, using Student's t and Fisher's exact tests.

RESULTS

HBOC-201 vasoactivity resulted in higher MAP in all studies. Among HBOC-201 pigs, DeltaMAP responses were significant for the first two infusions and inversely related to HS severity. Among controls, DeltaMAP responses remained significant through the fourth infusion in controlled HS models, and through the first in severe uncontrolled HS/TBI; none were significant in severe uncontrolled HS. DeltaMAP was higher with HBOC-201 through the first infusion in moderate controlled HS, the fifth in severe uncontrolled HS, and the second in severe uncontrolled HS/TBI; there were no group differences in severe controlled HS. No severe MAP responses occurred. Higher DeltaMAP severity did not impact outcome. Hypotension satisfied fluid reinfusion criteria less consistently than tachycardia. Overall, HBOC-201 improved physiologic parameters and survival without causing hypoperfusion; in severe HS, perfusion improved.

CONCLUSIONS

In swine with HS +/- TBI, HBOC-201 had mild to moderate vasoactivity, resulting in significant DeltaMAP responses mainly after initial infusions, no severe/adverse responses, and improved outcome. Our data suggest that use of physiologic parameters (e.g., tachycardia), in addition to hypotension to guide fluid reinfusion during HS resuscitation with HBOC-201, will minimize hypoperfusion risk and maximize potential benefit.

Coagulation patterns following haemoglobin-based oxygen carrier resuscitation in severe uncontrolled haemorrhagic shock in swine

Massive blood loss due to penetrating trauma and internal organ damage can cause severe haemorrhagic shock (HS), leading to a severely compromised haemostatic balance. This study evaluated the effect of bovine polymerized haemoglobin (Hb) (Hb-based oxygen carrier, HBOC) resuscitation on haemostasis in a swine model of uncontrolled HS. Following liver injury/HS, swine received HBOC (n= 8), Hextend (HEX) (n= 8) or no resuscitation (NON) (n= 8). Fluids were infused to increase mean arterial pressure above 60 mmHg and to reduce heart rate to baseline. At 4 h, the animals were eligible for blood transfusions. Prothrombin time (PT), activated partial thromboplastin time, fibrinogen, thromboelastography (TEG) and platelet function analyser closure time (PFA-CT) were compared by using mixed statistical model. At 4 h, blood loss (% estimated blood volume) was comparable for HBOC (65.5 +/- 18.5%) and HEX (80.8 +/- 14.4%) and less for NON (58.7 +/- 10.1%; P < 0.05). Resuscitation-induced dilutional coagulopathy was observed with HBOC and HEX, as indicated by reduced haematocrit, platelets and fibrinogen (P < 0.05). At 4 h, PT was higher in HEX than in HBOC groups (P < 0.01). In the early hospital phase, a trend to increased TEG reaction time and PFA-CT indicates that dilutional effects persist in HBOC and HEX groups. PFA-CT returned to baseline later with HBOC than with HEX (48 vs. 24 h) following blood transfusion. At 4 h, all surviving HEX animals (n= 3) required transfusion, in contrast to no HBOC (n= 7) or NON (n= 1) animals. In this severe uncontrolled HS model, successful resuscitation with HBOC produced haemodilutional coagulopathy less than or similar to that produced by resuscitation with HEX.

BOVINE POLYMERIZED HEMOGLOBIN VERSUS HEXTEND RESUSCITATION IN A SWINE MODEL OF SEVERE CONTROLLED HEMORRHAGIC SHOCK WITH DELAY TO DEFINITIVE CARE

To compare the efficacy of low-volume resuscitation with bovine polymerized hemoglobin (HBOC-201) versus hetastarch (HEX) in an intermediate severity combat-relevant hemorrhagic shock swine model with a simulated delay to hospital care. Twenty-four anesthetized pigs were hemorrhaged 55% estimated blood volume in conjunction with a 5-min rectus abdominus crush. At 20 min, pigs were resuscitated with 10 mL/kg of HBOC-201 or HEX or nothing (NON); resuscitated pigs received additional infusions (5 mL/kg) at 30, 60, 120, or 180 min if hypotension or tachycardia persisted. Pigs were monitored for a 4-h "prehospital" period. At 4-h, hospital arrival was simulated: surgical sites were repaired, blood, or saline provided, and pigs were recovered from anesthesia. Pigs were monitored for 72 h and then killed for histological evaluation. One hundred percent (8/8) of HBOC-201-, 75% (6/8) of HEX-, and 25% (2/8) of NON-resuscitated pigs survived to 72 h (P = 0.007 overall, HBOC vs. HEX P > 0.05). Mean arterial pressure and mean pulmonary arterial pressure were highest in the HBOC-201 group (P < 0.001), and HR was lowest (P < 0.001). HBOC-201- and HEX-resuscitated pigs had comparable cardiac index and prehospital fluid requirements. HBOC-201 pigs had higher transcutaneous tissue oxygen tension, P < 0.001) and lower urine output (P < 0.001). At simulated hospital arrival, no HBOC-201 pigs required additional fluids or blood transfusion. In contrast, 100% of HEX pigs required blood transfusions (P < 0.01). In this swine model of controlled hemorrhage with low-volume resuscitation and delayed definitive care, HBOC-201 pigs had improved hemodynamics, transcutaneous tissue oxygen tension, and transfusion avoidance compared with HEX.