A Comparison of the Hemoglobin-Based Oxygen Carrier HBOC-201 to Other Low-Volume Resuscitation Fluids in a Model of Controlled Hemorrhagic Shock

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.

The effect of pPolyHb on hemodynamic stability and mesenteric microcirculation in a rat model of hemorrhagic shock

The effects of polymerized porcine hemoglobin (pPolyHb) on hemodynamic stability and maintenance of mesenteric microvascular function were explored in a rat model of hemorrhagic shock (HS). Following controlled hemorrhage, rats were infused with equal volumes of either pPolyHb, hetastarch (HES), or red blood cell (RBC). The results showed that pPolyHb was superior to HES and RBC in restoring hemodynamic stability and reversing anaerobic metabolism. We observed a reduction in the diameter of mesenteric microvasculature after HS. Resuscitation with pPolyHb and RBC was able to restore the diameters of the venules and arterioles, whereas HES failed to restore the diameters during the observation period.

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.

Hypertonic HBOC-201 decreases neutrophil activation after hemorrhagic shock

OBJECTIVE

To evaluate neutrophil activation after exposure to standard HBC-201 (suspended in lactate Ringer's solution) versus HBOC-201 suspended in hypertonic 7.5% saline solution.

METHODS

We use plasma and tissue obtained from pigs subjected to controlled hemorrhagic shock and an ex vivo model of stimulated human whole blood. The pigs were resuscitated with the following (n = 8 per group) standard HBOC-201, or hypertonic HBOC-201. We used HTS 7.5%, Ringer's lactate as control resuscitation. Human blood was stimulated with same fluids. We measured the following neutrophil markers; IL-8, H2O2 in pig plasma, MPO in pig tissue, and H2O2, IL-8, and CD11b/CD18 in human whole blood.

RESULTS

H2O2 and IL-8 as well as tissue MPO were significantly decreased in pigs resuscitated with HT-HBOC-201 and HT 7.5%. Ex vivo experiments blood diluted with HTS and HT-HBOC-201 revealed lower expression of CD11b/CD18, H2O2, and IL-8. Blood diluted with HBOC-201 had a higher CD11b/CD18 expression than blood diluted with LR solution.

CONCLUSION

Our in vivo and ex vivo experiments indicate that HBOC-201 suspended in hypertonic 7.5% saline solution is associated with significantly less neutrophil activation when compared to standard HBOC-201 suspended in lactate Ringer's solution.

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.

Animal models for trauma research: what are the options?

Even if trauma patients initially avoid death after trauma (due to massive blood volume loss, primary severe brain injury), they are still at risk for multiple organ failure. Thus, it is crucial to elucidate the underlying pathophysiological mechanisms of trauma/hemorrhagic shock and the immune response involved. As of now, many hemorrhagic shock/trauma studies have used various types of animal models. Despite a large number of results from these efforts, some authors have argued that animal model results are difficult to translate directly into the clinical scenario. This review summarizes the advantages and the disadvantages of using animal models in trauma/hemorrhagic shock studies and discusses the relevance of various animal studies to the clinical scenario.

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.

Blood substitutes: hemoglobin-based oxygen carriers

Blood product substitutes, particularly the hemoglobin-based oxygen carriers, represent one of the most exciting fields of research and development in modern medicine. The concept has been several decades in the making, and with products in phase III clinical trials, the use of hemoglobin-based oxygen carriers may be close to reality. The potential applications are limitless with interest from the military and civilian sectors.

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.

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.

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

BACKGROUND

Data are limited on the actions of hemoglobin based oxygen carriers (HBOCs) after traumatic brain injury (TBI). This study evaluates neurotoxicity, vasoactivity, cardiac toxicity, and inflammatory activity of HBOC-201 (Biopure, Cambridge, Mass.) resuscitation in a TBI model.

METHODS

Swine received TBI and hemorrhage. After 30 minutes, resuscitation was initiated with 10 mL/kg normal saline (NS), followed by either HBOC-201 (6 mL/kg, n = 10) or NS control (n = 10). Supplemental NS was administered to both groups to maintain mean arterial pressure (MAP) >60 mm Hg until 60 minutes, and to maintain cerebral perfusion pressure (CPP) >70 mm Hg from 60 to 300 minutes. The control group received mannitol (1 g/kg) and blood (10 mL/kg) at 90 minutes and half (n = 5) received CPP directed phenylephrine (PE) therapy after 120 minutes. Serum cytokines were measured with ELISA and coagulation was evaluated with thromboelastography. Brains were harvested for neuropathology.

RESULTS

With HBOC administration, MAP, CPP, and brain tissue PO2 were restored within 30 minutes and maintained until 300 minutes. Clot strength and fibrin formation were maintained and 9/10 successfully extubated. In contrast, with control, MAP and brain tissue PO2 did not correct until 120 minutes, after mannitol, transfusion and 40% more crystalloid. Furthermore, without PE, CPP did not reach target and 0/5 could be extubated. Lactate, heart rate, cardiac output, mixed venous oxygenation, muscle oxygenation, serum cytokines, and histology did not differ between groups.

CONCLUSIONS

After TBI, a single HBOC-201 bolus with minimal supplements provided rapid resuscitation, while maintaining CPP and improving brain oxygenation, without causing cardiac dysfunction, coagulopathy, cytokine release, or brain structural changes.

Resuscitation from Hemorrhagic Shock: Fluid Selection and Infusion Strategy Drives Unmeasured Ion Genesis

BACKGROUND

This study compares unmeasured ion generation by different resuscitation fluids and strategies for hemorrhagic shock (HS).

METHODS

A rectus crush injury and 40% hemorrhage initiated controlled HS in 24 minipigs. Pigs (n = 8/gp) were untreated (NON) or bolused (10 cc/kg bw) with HBOC-201 (HBOC), or 6% Hetastarch (HEX) after 20 minutes of HS. Additional boluses occurred for hypotension (mean arterial pressure [MAP] <60 mm Hg) or tachycardia (heart rate [HR] >baseline) for 4 hours; other therapy was withheld, simulating delayed evacuation. Hemodynamics, acid-base parameters, and strong ion difference (SID) and strong ion gap (SIG), were assessed. Data are means +/- SD or percent; significance for p < 0.05.

RESULTS

Initial MAP was similar (p > 0.05) as was ultimate survival (p > 0.05). By 30 minutes, MAP was higher with HBOC (63 +/- 8; p = 0.01) versus HEX (37 +/- 5) or NON (35 +/- 4). HBOC required less fluid than HEX (515 +/- 58 versus 830 +/- 45 mL, p = 0.019). Lactate was similar between groups (p > 0.05). pH was highest in HBOC by 180 minutes (p < 0.05). SID was constant in NON, decreased in HEX, but increased in HBOC (p < 0.05 by 60 minutes). SIG remained unchanged in NON and HEX, but declined in HBOC (p < 0.05 by 30 minutes).

CONCLUSIONS

HBOC resuscitation required the least fluid. Unmeasured anions were prevalent in HEX and NON (+ SIG), whereas HBOC liberated unmeasured cations (- SIG); differences were inapparent when only evaluating pH. Only HBOC increased the SID, electrochemically promoting alkalosis. Resuscitation fluid differences may aid care in high lactate conditions where an induced counterbalancing metabolic alkalosis may be beneficial.

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

OBJECTIVE

To test our hypothesis that hemoglobin-based oxygen carrier (HBOC)-201 resuscitation in hemorrhagic shock (HS) will not lead to increased organ injury and dysfunction.

DESIGN

Three swine HS models simulating military-relevant delayed evacuation: a) moderate controlled HS, b) severe controlled HS, and c) severe uncontrolled HS.

SETTING

Military research laboratory.

SUBJECTS

Swine.

INTERVENTIONS

Swine were anesthetized/intubated and instrumented. To induce HS, in two controlled hemorrhage experiments, 40% (moderate controlled HS) or 55% (severe controlled HS) of blood volume was withdrawn; in an uncontrolled HS experiment, the liver was crushed/lacerated. During a 4-hr "prehospital phase," pigs were resuscitated with HBOC-201 (HBOC) or Hextend (HEX) or were nonresuscitated (NON). Upon "hospital arrival," liver injury was repaired (severe uncontrolled HS), blood or saline was infused, hemodynamics were monitored, and blood was collected. Upon animal death and/or 72 hrs, necropsy was followed by histopathologic evaluation of organ injury (hematoxylin and eosin, electron microscopy) and immunohistochemistry of oxidative potential (3-nitrotyrosine). Significance (p < .05) was assessed by Kruskal-Wallis, analysis of variance/Bonferroni, and mixed procedure tests.

MEASUREMENTS AND MAIN RESULTS

Survival was significantly higher with HBOC than HEX only with severe uncontrolled HS (p = .002). Myocardial necrosis/fibroplasia, fluid requirements, cardiac output, and cardiac enzymes were generally similar or lower in HBOC than HEX pigs, but creatine kinase-MB (but not creatine kinase-MB/creatine kinase ratio) was higher with HBOC in moderate controlled HS. Alveolar/interstitial pulmonary edema was similar with HBOC and HEX, but Po2 was higher with HBOC in severe uncontrolled HS. Jejunal villar epithelial and hepatocellular necrosis were similarly minimal to moderate in all groups. Minimal biliary changes occurred exclusively with HBOC. Aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase were generally higher with HBOC than HEX. Mild renal papillary injury occurred more frequently with HBOC, but consistent patterns for urine output, blood urea nitrogen, and creatinine, were not seen. The 3-nitrotyrosine staining intensity was not different.

CONCLUSIONS

In comparison with hetastarch, HBOC-201 resuscitation of swine with HS increased survival (with severe HS), did not increase evidence of oxidative potential, and had histopathologic and/or functional effects on organs that were clinically equivocal (myocardium, lungs, hepatic parenchyma, jejunum, and renal cortex/medulla) and potentially adverse (hepatobiliary and renal papilla). The effects of HBOC-201-resuscitation in HS should be corroborated in controlled clinical trials.

Immune effects of resuscitation with HBOC-201, a hemoglobin-based oxygen carrier, in swine with moderately severe hemorrhagic shock from controlled hemorrhage

HBOC-201, a hemoglobin-based oxygen carrier, improved physiologic parameters and survival in hemorrhagic shock (HS) animal models. However, resuscitation from HS and the properties of different fluids influence immune responses. The aim of this study was to determine if HBOC-201 significantly alters immune function in traumatic HS. Anesthetized pigs underwent soft tissue injury, controlled hemorrhage of 40% of blood volume, and resuscitation with HBOC-201 or Hextend, or no resuscitation. Sequential whole-blood samples were collected for analyses of leukocyte differential (hematology analyzer), T-lymphocyte subsets (CD3, CD4, and CD8) (FACS), lymphocyte adhesion marker CD49d (alpha4-integrin) expression (FACS), plasma cytokines-tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-10-(ELISA), and lymphocyte apoptosis (annexin-V/propidium iodide staining) (FACS). Statistical analyses were performed by the mixed procedure. Total WBC counts decreased posthemorrhage in both resuscitation groups. Lymphocyte percentages decreased and PMN percentages increased around 4 h posthemorrhage in all groups. CD3 cells decreased in all groups, but CD4 and CD8 cells decreased only in the resuscitation groups. TNF-alpha levels were not detectable in any groups. IL-6 levels were similar across treatment groups (P > 0.05); however, IL-10 levels were higher in the HBOC group, as early as 1 h posthemorrhage (P = 0.04). Increases in lymphocytic CD49d expression levels and apoptosis occurred only in nonresuscitation and Hextend groups, respectively (P < or = 0.01). In comparison with Hextend, HBOC-201 had no significant adverse or beneficial effects on immune function in this model of moderately severe HS in swine, suggesting that it may be safe as a resuscitation fluid in HS patients.

Prolonged low-volume resuscitation with HBOC-201 in a large-animal survival model of controlled hemorrhage

BACKGROUND

Military guidelines call for two 500-mL boluses of Hextend for resuscitation in far-forward environments. This study compared a hemoglobin-based oxygen carrier (HBOC-201; Hemopure) to Hextend when used to treat hemorrhagic shock in situations of delayed definitive care military operations.

METHODS

Yorkshire swine (55-65 kg) were hemorrhaged to a mean arterial blood pressure (MAP) of 30 mmHg. Hypotension was maintained for 45 minutes followed by resuscitation with either Hextend (HEX) (n = 8) or HBOC-201 (HBOC) (n = 8). Over 8 hours, animals received up to 1,000 mL of either fluid in an effort to sustain an MAP of 60 mmHg. At the end of 8 hours, HEX animals received 2 L of lactated Ringer's solution followed by shed blood. HBOC animals received 4 L of lactated Ringer's solution only. Animals were killed and necropsied on postprocedure day 5. Hemodynamic data were collected during shock and resuscitation. Complete blood counts, amylase, lactate, coagulation studies, and renal and liver function were measured throughout the experiment.

RESULTS

Equivalent volumes were hemorrhaged from each group (HBOC, 44.3 +/- 2.2 mL/kg; HEX, 47.4 +/- 3.0 mL/kg). The HBOC group achieved the goal MAP (HBOC, 60.0 +/- 2.3 mmHg; HEX, 46.4 +/- 2.3 mmHg; p < 0.01) and required less volume during the initial 8 hours (HBOC, 12.4 +/- 1.4 mL/kg; HEX, 17.3 +/- 0.3 mL/kg; p < 0.01). The HBOC group had lower SvO2 (HBOC, 46.3 +/- 2.4%; HEX, 50.7 +/- 2.5%; p = 0.12) and cardiac output (HBOC, 5.8 +/- 0.4 L/min; HEX, 7.2 +/- 0.6 L/min; p = 0.05), but higher systemic vascular resistance (HBOC, 821.4 +/- 110.7 dynes . s . cm-5; HEX, 489.6 +/- 40.6 dynes . s . cm-5; p = 0.01). Base excess, pH, lactate, and urine output did not differ between groups. HEX group survival was 50% (four of eight) versus 88% for the HBOC group (seven of eight). All animals survived the initial 8 hours. Animals surviving 5 days displayed no clinical or laboratory evidence of organ dysfunction in either group.

CONCLUSION

HBOC-201 more effectively restored and maintained perfusion pressures with lower volumes, and allowed for improved survival. These data suggest that hemoglobin-based oxygen carriers are superior to the current standard of care for resuscitation in far-forward military operations.

Effects of bovine polymerized hemoglobin on coagulation in controlled hemorrhagic shock in swine

HBOC-201, a bovine polymerized hemoglobin, has been proposed as a novel oxygen-carrying resuscitative fluid for patients with hemorrhagic shock (HS). Herein, we evaluated the hemostatic effects of HBOC-201 in an animal model of HS. A 40% blood loss-controlled hemorrhage and soft tissue injury were performed in 24 invasively monitored Yucatan mini-pigs. Pigs were resuscitated with HBOC-201 (HBOC) or hydroxyethyl starch (HEX), or were not resuscitated (NON) based on cardiac parameters during a 4-h prehospital phase. Afterward, animals received simulated hospital care for 3 days with blood or saline transfusions. Hemostasis measurements included in vivo bleeding time (BT), thromboelastography (TEG), in vitro bleeding time (platelet function; PFA-CT), prothrombin time (PT), and partial thromboplastin time (PTT). Serum lactate was measured and lung sections were evaluated for microthrombi by electron microscopy. During the prehospital phase, BT remained unchanged in the HBOC group. TEG reaction time increased in HBOC pigs during the late prehospital phase and was greater than in NON or HEX pigs at 24 h (P = 0.03). TEG maximum amplitude was similar for the two fluid-resuscitated groups. PFA-CT increased in both resuscitated groups but less with HBOC (P = 0.02) in the prehospital phase; this effect was reversed by 24 h (P = 0.02). In the hospital phase, PT decreased (P < 0.02), whereas PTT increased above baseline (P < 0.01). Lactic acidosis in HBOC and HEX groups was similar. Aspartate aminotransferase was relatively elevated in the HBOC group at 24 h. Electron microscopy showed no evidence of platelet/fibrin clots or microthrombi in any of the animals. Twenty-four-hour group differences mainly reflected the fact that all HEX animals (8/8) received blood transfusions compared with only one HBOC animal (1/8). In swine with HS, HBOC resuscitation induced less thrombopathy than HEX during the prehospital phase. Mild delayed effects on platelet and clot formation during the hospital phase are transient and likely related to fewer blood transfusions. In swine with HS, HBOC resuscitation induced less thrombopathy than HEX during the prehospital phase but more thrombopathy in the hospital phase. The delayed effects on platelet and clot formation during the hospital phase are transient and may be related to the need for fewer blood transfusions.

A hemoglobin-based oxygen carrier, bovine polymerized hemoglobin (HBOC-201) versus hetastarch (HEX) in a moderate severity hemorrhagic shock swine model with delayed evacuation

OBJECTIVE

To evaluate the efficacy of HBOC-201 for resuscitation of hemorrhagic shock in a swine model incorporating soft tissue injury and delayed evacuation.

METHODS

A muscle crush injury and 40% estimated blood volume controlled hemorrhage was completed in 24 Yucatan mini-pigs. Pigs were untreated or resuscitated with HBOC-201 or 6% hetastarch (HEX) at 20 min. Invasive hemodynamics and clinical variables were monitored for 4 h (pre-hospital phase) and subsequent fluid infusions were administered for severe hypotension or tachycardia. Animals were recovered from anesthesia and monitored non-invasively to 72 h (hospital phase).

RESULTS

100% (8/8) of HBOC-201-, 88% (7/8) of HEX-, and 63% (5/8) of non-resuscitated pigs, survived to 72 h (p=0.27). Mean arterial pressure, mean pulmonary arterial pressure and systemic vascular resistance index were higher in HBOC-201 pigs. By 90 min, cardiac index was restored to baseline in the HBOC-201 group and was 1.4-fold greater than baseline in the HEX group. HBOC-201 pigs had lower fluid requirements than HEX pigs (18.8+/-1.8 and 29.9+/-1.1 ml/kg, p<0.001) in the pre-hospital phase and required fewer blood transfusions (1.3+/-1.3 and 9.4+/-0.6 ml/kg, respectively, p<0.001) in the hospital phase. Urine output and blood creatinine were comparable in HBOC-201 and HEX pigs. Tissue oxygenation levels were highest in the HBOC-201 group.

CONCLUSIONS

As HBOC-201 restored hemodynamics and tissue oxygenation and decreased fluid requirements, in comparison with HEX, HBOC-201 was at least as efficacious and possibly a superior resuscitative fluid in a military-relevant delayed evacuation hemorrhagic shock swine model.

Choice of fluid influences outcome in prolonged hypotensive resuscitation after hemorrhage in awake rats

Hypotensive resuscitation (Hypo) has been considered an alternate resuscitation strategy in clinical settings that prevent the application of standard Advanced Trauma Life Support care. However, validation of this approach when used for prolonged periods of time remains to be demonstrated. The purpose of this study was to evaluate prolonged Hypo as an alternative to standard resuscitation using various currently available resuscitative fluids. Unanesthetized, male Sprague-Dawley rats underwent computer-controlled hemorrhagic shock and resuscitation. There were six experimental groups; nonhemorrhage (NH), nonresuscitated control (C), Hypo with lactated Ringer's (HypoLR), Hypo with Hextend, 6% hydroxyethyl starch in a balanced salt solution (HEX), Hypo with PolyHeme, a polymerized hemoglobin solution (HBOC), or standard resuscitation with LR (StandLR). Animals were bled over 15 min to a mean arterial blood pressure (MAP) of 40 mmHg where the blood pressure (BP) was held for 30 min. Hypo groups were resuscitated to 60 mmHg for 4 h followed by further resuscitation to 80 mmHg. StandLR rats were resuscitated to 80 mmHg immediately after the hemorrhage period. Animals were monitored until death or they were sacrifice at 24 h. Prolonged Hypo with HEX or LR resulted in a trend toward improved 24-h survival compared with C (71%, 65%, and 48%, respectively), and performed at least as well as StandLR (58% survival). HEX required significantly less intravenous fluid (0.7x total estimated blood volume [EBV]) compared with HypoLR (1.9x EBV) and StandLR (3.2x EBV) (P < 0.05). Although HBOC required the smallest fluid volume (0.4x EBV), survival was no better than C and it resulted in the most significant acidosis. These results support the decision to use Hextend for Hypo, a strategy currently being applied on the battlefield.

Endothelial Dysfunction After Lactated Ringerʼs Solution Resuscitation for Hemorrhagic Shock

BACKGROUND

Endothelial dysfunction is presumed to occur after hemorrhagic shock and resuscitation. This study uses a novel large-animal model to evaluate the effects of diverse resuscitation regimens on endothelial function.

METHODS

Twenty-seven adult domestic pigs (Sus scrofa) were used in this study. Control pigs (n = 3) underwent instrumentation alone. The remaining pigs experienced controlled hemorrhagic shock to a mean arterial blood pressure of 30 +/- 5 mm Hg for 45 minutes. Pigs were resuscitated to their baseline mean arterial blood pressure +/-5 mm Hg with either shed blood (SB; n = 8), lactated Ringers solution (40 mL/kg) followed by shed blood (LRSB; n = 8), or lactated Ringers solution alone (LR; n = 8). At baseline, 1 and 4 hours after resuscitation, acetylcholine (5, 10, and 15 microg/min) was infused into the proximal iliac artery to measure endothelial dependent relaxation (EDR). Sodium nitroprusside was infused to determine endothelial independent relaxation at the end of the study to insure smooth muscle vasomotor integrity. External iliac artery luminal diameter was measured using motion-mode ultrasonography. Statistical analysis was performed using repeated-measures analysis of variance with Tukey's post-hoc analysis.

RESULTS

All pigs survived the experiment. Pigs required ninefold more resuscitation with LR (370.58 +/- 29 mL/kg) versus SB (41.45 +/- 3.5 mL/kg) or LRSB (76.4 +/- 1.1 mL/kg) (p < 0.05). EDR for LR pigs 1 hour after initiation of resuscitation (R1) was 70.4 +/- 14.4% compared with 94.2 +/- 13.4% for SB and 106.1 +/- 8.2% for LRSB (p < 0.05). At 4 hours after resuscitation (R4), systolic luminal diameters were larger in the SB (0.45 +/- 0.01 cm) and LRSB (0.51 +/- 0.02 cm) groups compared with LR (0.41 +/- 0.03 cm) (LRSB versus LR; p = 0.01). At R4, EDR for the LR group was 78.3 +/- 10.7% compared with SB (101.4 +/- 8.3%) and LRSB (106.4 +/- 7.4%) (p < 0.05). Infusion of sodium nitroprusside confirmed integrity of smooth muscle vasorelaxation. Analysis of serum nitric oxide levels revealed decreased values after resuscitation with LR (9.44 +/- 0.76 mol/L) compared with SB (26.3 +/- 7.8 mol/L) and LRSB (16.3 +/- 1.0 mol/L) (p = not significant).

CONCLUSION

This is the first description of a large-animal model to evaluate EDR after hemorrhagic shock. Resuscitation with LR requires significantly larger volumes than SB or LRSB. LR resuscitation leads to endothelial dysfunction, as determined by decreased EDR, versus SB or LRSB. Resuscitation with blood products may preserve nitric oxide bioactivity when compared with crystalloid resuscitation in the setting of hemorrhagic shock.

MalPEG-hemoglobin (MP4) improves hemodynamics, acid-base status, and survival after uncontrolled hemorrhage in anesthetized swine

OBJECTIVES

MalPEG-hemoglobin, 4 g/dL (MP4), is a hemoglobin-based oxygen carrier with a low hemoglobin concentration, low P50 (oxygen half-saturation pressure of hemoglobin), high colloid osmotic pressure, and high viscosity. This study evaluated resuscitation with MP4 in anesthetized swine hemorrhaged 250 mL by controlled withdrawal, followed by a 5-mm tear in the abdominal aorta.

DESIGN

Randomized, unblinded.

SETTING

Academic animal laboratory.

SUBJECTS

Anesthetized male and female Swedish Landrace pigs.

INTERVENTIONS

Four groups of pigs (n = 7 each) were randomized after hemorrhage by aortic tear to receive 250 mL of MP4, Ringer's acetate, 10% pentastarch, or 4 g/dL of stroma-free hemoglobin, followed by aortic repair and transfusion of 250 mL of autologous blood. End points were 20-hr survival, hemodynamic variables, and acid-base status.

MEASUREMENTS AND MAIN RESULTS

Measurements included continuous aortic, pulmonary arterial, and central venous pressures, cardiac output by thermodilution, arterial and venous blood gases; electrolytes; lactate; base excess; oxygen delivery, consumption, and extraction ratio; hematocrit; hemoglobin; and urine output. Body weight (24-27 kg) and hemorrhage volume (26-33 mL/kg) were similar in the four groups. The nadir of mean arterial pressure (22-28 mm Hg) and the increase in lactic acid (5-8 mEq/L) after hemorrhage were similar in all groups, indicating equivalent shock in the four groups. Survival was greatest in the MP4-treated animals (six of seven) compared with Ringer's acetate (two of seven), 10% pentastarch (one of seven), and stroma-free hemoglobin (two of seven) and was accompanied by an improved recovery of arterial pressure, cardiac output, and lactate. Total hemoglobin concentration was equivalent in all groups. Arterial pressure did not increase above baseline values, and systemic vascular resistance was unchanged following administration of MP4, indicating the lack of peripheral vasoconstriction. Mortality in Ringer's acetate, stroma-free hemoglobin, and 10% pentastarch treated animals was associated with deteriorating acid-base status, low urine output, and hyperkalemia.

CONCLUSION

These data demonstrate that restoration of oxygen delivery with a small volume of MP4 yields significant recovery from hemorrhage without systemic vasoconstriction.

Hemoglobin substitutes

Orthopaedic patients frequently require blood transfusions to treat peri-operative anemia. Research in the area of hemoglobin substitutes has been of great interest since it holds the promise of reducing the reliance on allogeneic blood transfusions. The three categories of hemoglobin substitutes are (1) cell-free, extracellular hemoglobin preparations made from human or bovine hemoglobin (hemoglobin-based oxygen carriers or HBOCs); (2) fluorine-substituted linear or cyclic carbon chains with a high oxygen-carrying capacity (perfluorocarbons); and (3) liposome-encapsulated hemoglobin. Of the three, HBOCs have been the most extensively studied and tested in preclinical and clinical trials that have shown success in diminishing the number of blood transfusions as well as an overall favorable side-effect profile. This has been demonstrated in vascular, cardiothoracic, and orthopaedic patients. HBOC-201, which is a preparation of cell-free bovine hemoglobin, has been approved for clinical use in South Africa. These products may well become an important tool for physicians treating peri-operative anemia in orthopaedic patients.

A Hemoglobin Based Oxygen Carrier, Bovine Polymerized Hemoglobin (HBOC-201) versus Hetastarch (HEX) in an Uncontrolled Liver Injury Hemorrhagic Shock Swine Model with Delayed Evacuation

BACKGROUND

As HBOC-201 improves outcome in animals with hemorrhagic shock (HS), we compared HBOC-201 and HEX (used by U.S. military special operations forces) in a swine model of delayed evacuation and uncontrolled HS.

METHODS

Twenty-four Yucatan pigs underwent a grade III liver injury and were resuscitated with HBOC-201, HEX, or no fluid (NON). Additional infusions were given for hypotension or tachycardia. After 4 hours, the liver was repaired; IV fluids and blood transfusions were administered. Pigs were monitored for 72 hours.

RESULTS

Survival was 7/8, 1/8, and 1/8 in HBOC-201-, HEX-, and NON-resuscitated pigs, respectively. Compared with HEX, HBOC-201 pigs had higher systemic and pulmonary artery pressures and had comparable cardiac outputs, but were less tachycardic. Transcutaneous tissue oxygenation was restored more rapidly in HBOC-201 pigs, there was a trend to lower lactic acid, and base deficit was less. HBOC-201 pigs had lower fluid requirements, higher urine output, and lower blood loss than HEX pigs.

CONCLUSIONS

Despite evidence of vasoactivity, HBOC-201 more effectively stabilized tissue oxygenation, reversed anaerobic metabolism, decreased bleeding, and increased survival in comparison with HEX. If confirmed in clinical trials, these data suggest that for the resuscitation of combat casualties with delayed evacuation and uncontrolled HS due to solid organ injury, HBOC-201 is a superior low-volume resuscitative fluid.