Tissue oxygen monitoring during hemorrhagic shock and resuscitation: a comparison of lactated Ringer's solution, hypertonic saline dextran, and HBOC-201

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.

Cremaster muscle perfusion, oxygenation, and heterogeneity revealed by a new automated acquisition system in a rodent model of prolonged hemorrhagic shock

Local blood flow/oxygen partial pressure (Po₂) distributions and flow-Po₂ relationships are physiologically relevant. They affect the pathophysiology and treatment of conditions like hemorrhagic shock (HS), but direct noninvasive measures of flow, Po₂, and their heterogeneity during prolonged HS are infrequently presented. To fill this void, we report the first quantitative evaluation of flow-Po₂ relationships and heterogeneities in normovolemia and during several hours of HS using noninvasive, unbiased, automated acquisition. Anesthetized rats were subjected to tracheostomy, arterial/venous catheterizations, cremaster muscle exteriorization, hemorrhage (40% total blood volume), and laparotomy. Control animals equally instrumented were not subjected to hemorrhage/laparotomy. Every 0.5 h for 4.5 h, noninvasive laser speckle contrast imaging and phosphorescence quenching were employed for nearly 7,000 flow/Po₂ measurements in muscles from eight animals, using an automated system. Precise alignment of 16 muscle areas allowed overlapping between flow and oxygenation measurements to evaluate spatial heterogeneity, and repeated measurements were used to estimate temporal heterogeneity. Systemic physiological parameters and blood chemistry were simultaneously assessed by blood samplings replaced with crystalloids. Hemodilution was associated with local hypoxia, but increased flow prevented major oxygen delivery decline. Adding laparotomy and prolonged HS resulted in hypoxia, ischemia, decreased tissue oxygen delivery, and logarithmic flow/Po₂ relationships in most regions. Flow and Po₂ spatial heterogeneities were higher than their respective temporal heterogeneities, although this did not change significantly over the studied period. This quantitative framework establishes a basis for evaluating therapies aimed at restoring muscle homeostasis, positively impacting outcomes of civilian and military trauma/HS victims.NEW & NOTEWORTHY This is the first study on flow-Po₂ relationships during normovolemia, hemodilution, and prolonged hemorrhagic shock using noninvasive methods in multiple skeletal muscle areas of monitored animals. Automated flow/Po₂ measurements revealed temporal/spatial heterogeneities, hypoxia, ischemia, and decreased tissue oxygen delivery after trauma/severe hemorrhage. Hemodilution was associated with local hypoxia, but hyperemia prevented a major decline in oxygen delivery. This framework provides a quantitative basis for testing therapeutics that positively impacts muscle homeostasis and outcomes of trauma/hemorrhagic shock victims.

Automated noninvasive evaluation of blood flow and oxygenation in rats integrated with systemic physiological monitoring

BACKGROUND

Many studies evaluating blood flow and oxygen partial pressure (PO2) do not directly measure both parameters, are confined to few locations/microvessels, and depend on investigator's selection of measuring sites. Moreover, clinically/physiologically relevant systemic parameters are not simultaneously recorded. We implemented an automated system for prolonged blood flow/PO2 acquisition in large areas while collecting relevant systemic information.

METHODS

In anesthetized animals, cardiorespiratory parameters were continuously recorded. Other data were collected at baseline and hourly after 4 hours of hemorrhagic shock. A cremaster muscle was spread over a pedestal fixed to a motorized stage. One 2-dimensional tissue scan allowed 16 noninvasive PO2 measurements using oxygen-dependent phosphorescence quenching and fiber optics. Blood flow was estimated using laser speckle contrast imaging in the same areas used for PO2 measurements. At each timepoint, blood was sampled for extensive biochemistry/coagulation profile.

RESULTS

The system was used successfully by different operators. A set of flow/PO2 measurements was completed in less than 90 seconds. Muscle flow and PO2 correlated with some but not several systemic parameters, emphasizing the importance of performing both local and systemic evaluations.

CONCLUSION

System advantages include integration between local and over 40 systemic parameters, unbiased data collection/analysis, improved performance/sampled area, easy expansion, implementation and maintenance, no customized programming, and simplified training. Combining this system with trauma/prolonged HS models will enhance our ability to investigate tissue stability and select better resuscitation strategies to improve outcomes and survival.

LEVEL OF EVIDENCE

Diagnostic test, level V.

The Effects of Pancreatic Microcirculatory Disturbances on Histopathologic Tissue Damage and the Outcome in Severe Acute Pancreatitis

OBJECTIVES

Severe acute pancreatitis is an inflammatory disease of the pancreas with a high morbidity and mortality. To date, no causal treatment is known. The aim of the present study was to analyze the impact of pancreatic microcirculatory disturbances in severe acute pancreatitis and to correlate the effects with histopathologic tissue damage and outcome.

METHODS

Severe acute pancreatitis was induced in 129 pigs by injection of glycodeoxycholic acid into the pancreatic duct. Pancreatic microcirculation, pancreatic tissue oxygenation, histopathologic tissue damage, and survival were measured and analyzed.

RESULTS

Our study demonstrates a strong correlation between pancreatic microcirculatory disturbances and histopathologic tissue damage (r = 0.728; P < 0.001). Furthermore, we showed a strong correlation between tissue oxygenation and the severity of the pancreatitis according to an established porcine pancreatitis score (r = 0.694; P < 0.001). In addition, disturbances of the pancreatic microcirculation were shown to be associated with an increased mortality rate in severe acute pancreatitis.

CONCLUSIONS

We found that pancreatic microcirculatory disturbances have significant effects on histopathologic tissue damage and the outcome of severe acute pancreatitis. For a better survival of severe acute pancreatitis, the treatment should focus on an improvement of pancreatic microcirculation.

Tissue oxygen tension monitoring of organ perfusion: rationale, methodologies, and literature review

Tissue oxygen tension is the partial pressure of oxygen within the interstitial space of an organ bed. As it represents the balance between local oxygen delivery and consumption at any given time, it offers a ready monitoring capability to assess the adequacy of tissue perfusion relative to local demands. This review covers the various methodologies used to measure tissue oxygen tension, describes the underlying physiological and pathophysiological principles, and summarizes human and laboratory data published to date.

Regional oxygen saturation index (rSO2) in brachioradialis and deltoid muscle. Correlation and prognosis in patients with respiratory sepsis

OBJECTIVE

To compare oxygen saturation index (rSO2) obtained simultaneously in two different brachial muscles.

DESIGN

Prospective and observational study.

SETTING

Intensive care unit.

PATIENTS

Critically ill patients with community-acquired pneumonia.

INTERVENTIONS

Two probes of NIRS device (INVOS 5100) were simultaneously placed on the brachioradialis (BR) and deltoid (D) muscles.

VARIABLES

rSO2 measurements were recorded at baseline (ICU admission) and at 24h. Demographic and clinical variables were registered. Pearson's correlation coefficient was used to assess the association between continuous variables. The consistency of the correlation was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman plot. The predictive value of the rSO2 for mortality was calculated by ROC curve.

RESULTS

Nineteen patients were included with an ICU mortality of 21.1%. The rSO2 values at baseline and at 24h were significantly higher in D than in BR muscle. Values obtained simultaneously in both limbs showed a strong correlation and adequate consistency: BR (r=0.95; p<0.001; ICC=0.94; 95% CI: 0.90-0.96; p<0.001), D (r=0.88; p=0.01; ICC=0.88; 95% CI: 0.80-0.90; p>0.001) but a wide limit of agreement. Non-survivors had rSO2 values significantly lower than survivors at all times of the study. No patient with rSO2 >60% in BR died, and only 17.6% died with an rSO2 value >60% in D. Both muscles showed consistent discriminatory power for mortality.

CONCLUSION

Both BR and D muscles were appropriate for measuring rSO2.

[Erythrocytes and microvascular tone during acute traumatic haemorrhagic shock]

Haemorrhagic shock remains a leading cause of death in trauma patients. The concept of haematologic damage control is gradually taking place in the management of traumatic haemorrhagic shock. It is based primarily on the early implementation of a quality blood transfusion involving erythrocytes, plasmas and platelets transfusion. Red blood cell transfusion is mainly supported by the oxygen carrier properties of erythrocytes. However, it appears that erythrocytes ability to modulate the bioavailability of nitric oxide (NO) plays a major role in capillary opening and perfusion. Erythrocytes are also actively involved in the processes of hemostasis and coagulation. In this context, it seems difficult to define a threshold of hemoglobin concentration to determine the implementation of a blood transfusion in traumatic haemorrhagic shock.

Tissue oxygen saturation changes during intramedullary nailing of lower-limb fractures

BACKGROUND

The systemic complications of acute intramedullary nailing (IMN) in trauma patients are well known. There are no reliable methods available to predict these adverse outcomes. Noninvasive near-infrared spectroscopy (NIRS) allows measurement of oxygen saturation within muscle tissue (StO2) and quantification of the potential metabolic and microcirculatory effects of IMN in real time. The aim of this study was to characterize tissue oxygenation changes occurring during reamed IMN.

METHODS

Patients undergoing reamed IMN for fixation of a tibia or femur fracture and patients having an open reduction and internal fixation of the ankle (to control for potential effects of anesthesia) had a noninvasive NIRS probe attached to the thenar eminence of the hand. Tissue oxygenation was monitored continuously throughout the operation and digitally recorded for later analysis. Vascular occlusion tests, an established technique with the NIRS device, were performed before canal opening and after nail insertion (at equivalent times in the control group), to establish the presence and nature of changes in systemic microcirculation occurring during the duration of the operation.

RESULTS

Tissue oxygenation data were collected on 23 patients undergoing 26 IMN. (mean [SD] age, 36 [19] years; median Injury Severity Score [ISS], 9; interquartile range, 9-12). The control group consisted of 19 patients (mean [SD] age, 41 [18] years; ISS, 4). Remote muscle tissue desaturated significantly faster after IMN compared with the control operation (mean [SD] difference in IMN desaturation rate, 1.8% per minute [2.6% per minute]; mean [SD] difference in control group desaturation rate, -0.6% per minute [1.5% per minute]; p = 0.014). Near infrared-derived muscle oxygen consumption (NIR VO(2)) was significantly increased during the course of IMN compared with the control (mean [SD] difference in IMN NIR VO(2), 19.9 [32.1]; mean [SD] difference in control NIR VO(2), -4.2 [17.9]; p = 0.041).

CONCLUSION

IMN causes significant remote microcirculatory changes. The responsiveness of the microcirculation could be a predictor of secondary organ dysfunction.

LEVEL OF EVIDENCE

Epidemiologic study, level III.

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.

Bladder tissue oxygen tension monitoring in pigs subjected to a range of cardiorespiratory and pharmacological challenges

PURPOSE

A fall in tissue oxygen tension (tPO(2)) is an early indicator of organ hypoxia in both patients and animal models. We previously demonstrated the utility of bladder tPO(2) in various rodent shock models. As a prelude to clinical testing, we aimed to provide further validation of bladder tPO(2) monitoring in a large animal model undergoing a range of cardiorespiratory insults and vasoactive drug interventions.

METHODS

Anaesthetized, mechanically ventilated, instrumented female pigs (n = 8) were subjected to a range of short-term cardiorespiratory (changes in inspired oxygen concentration (FiO(2)), haemorrhage, positive end-expiratory pressure) and pharmacologic (inotrope, pressor) challenges. Global haemodynamics, arterial and pulmonary blood gases and bladder tPO(2) were measured before and after each challenge.

RESULTS

Bladder tPO(2) values fell in line with increasing degrees of hypoxaemia and haemorrhage, and were restored during resuscitation. These changes often preceded those seen in global haemodynamics, arterial base excess and lactate. The rise in bladder tPO(2) with hyperoxia, performed as an oxygen challenge test, was incrementally blunted by progressive haemorrhage. Dobutamine and norepinephrine both increased cardiac output and global O(2) delivery, but had no effect on bladder tPO(2) or lactataemia in these healthy pigs.

CONCLUSIONS

In this pig model bladder tPO(2) provides a sensitive indicator of organ hypoxia compared to traditional biochemical markers during various cardiorespiratory challenges. This technique offers a potentially useful tool for clinical monitoring.

Microcirculation follows macrocirculation in heart and gut in the acute phase of hemorrhagic shock and isovolemic autologous whole blood resuscitation in pigs

BACKGROUND

Disparity between the macro- and microcirculation is thought to occur as a result of (micro)vascular dysfunction in some types of shock. Whether this occurs during hemorrhagic shock, however, is unknown. We therefore investigated both macro- and microcirculatory variables in the heart as a vital organ and the gut as a nonvital organ. We hypothesized that the microcirculation in the gut would follow the macrocirculation in the acute phase of hemorrhagic shock and isovolemic autologous whole blood resuscitation, but that the microcirculation in the heart would be preserved even under conditions of macrocirculatory depression.

STUDY DESIGN AND METHODS

Eleven pigs (23 ± 4 kg) were anesthetized and subjected to a controlled hemorrhagic shock (30 and 45% reduction of total blood volume) and isovolemic resuscitation with autologous blood. Quantitative measurement of microvascular oxygen pressures (µpO(2)) was performed by phosphorimetry on the gut and heart simultaneously. Measurements of systemic hemodynamic and regional oxygen-derived variables as well as µpO(2) were performed at baseline, after the first and second phases of hemorrhage, and after resuscitation.

RESULTS

Five pigs responded to resuscitation, while six pigs died spontaneously within 20 to 30 minutes after reinfusion of the withdrawn blood, without significant differences in macro- or microcirculatory variables at baseline and after hemorrhage. Correlation analysis showed that microvascular pO(2) in the heart and the gut were closely related to macrocirculatory variables (cardiac index, mean arterial pressure, and oxygen delivery) during hemorrhage and resuscitation.

CONCLUSIONS

This study demonstrated that the microcirculation in the gut (being a nonvital organ) and heart (being a vital organ) follow the macrocirculation in the acute phase of hemorrhagic shock and isovolemic autologous whole blood resuscitation.

Tissue oxygen tension monitoring: will it fill the void?

PURPOSE OF REVIEW

The holy grail of circulatory monitoring is an accurate, continuous and relatively noninvasive means of assessing the adequacy of organ perfusion. This could be then advantageously used to direct therapeutic interventions to prevent both under-treatment and over-treatment and thus improve outcomes. However, in view of the heterogeneous response (adaptive or maladaptive) of different organs to various shock states, any monitor of perfusion adequacy cannot reflect every organ system, but should at least detect early deterioration in a 'canary' organ. Tissue oxygen tension reflects the balance between local oxygen supply and demand, and could thus be a potentially useful monitoring modality. This article examines the different technologies available and reviews the current literature regarding its utility as a monitor.

RECENT FINDINGS

Tissue oxygen tension, measured at a variety of sites in both human and laboratory studies, does appear to be a sensitive indicator of organ perfusion in different shock states. However, responses can vary not only between organs and between different shock states, but also over time. These changes reflect the particular oxygen supply-demand balance present in that tissue bed at that specific time point in the disease process. The response to a dynamic oxygen challenge test provides further information that allows severity to be more readily differentiated.

SUMMARY

Monitoring of tissue oxygen tension may offer a potentially useful tool for clinical management though significant validation needs to be first performed to confirm its promise.

Treatment with beta-hydroxybutyrate and melatonin is associated with improved survival in a porcine model of hemorrhagic shock

INTRODUCTION

The neuroprotective ketone β-hydroxybutyrate (BHB) and the antioxidant melatonin have been found at elevated levels in hibernating mammals. Previous studies in rat models of hemorrhagic shock have suggested a benefit. We compared infusion of 4M BHB and 43 mM melatonin (BHB/M) to 4M sodium chloride and 20% DMSO (control solution) to evaluate for potential benefits in porcine hemorrhagic shock.

METHODS

Hemorrhagic shock was induced to obtain systolic blood pressures <50 mmHg for 60 min. Pigs were treated with a bolus of either BHB/M (n=9) or control solution (n=8) followed by 4-h infusion of the either BHB/M or control solution. All animals were then resuscitated for 20 h after shock. Physiological data were continually recorded, and blood samples were taken at intervals throughout the experiment. Serum samples were analyzed via high resolution NMR for metabolomic response.

RESULTS

BHB/M treatment significantly increased 24-h survival time when compared to treatment with control solution (100% versus 62%; p=0.050), with a trend toward decreased volume of resuscitative fluid administered to animals receiving BHB/M. BHB/M-treated animals had lower base deficit and higher oxygen consumption when compared to animals receiving control solution. Serum metabolite profiles revealed increases in β-hydroxybutyrate (BHB), succinate, 2-oxovalerate and adipate with BHB/M treatment as compared with animals treated with control infusion.

CONCLUSION

Infusion of BHB/M conferred a survival benefit over infusion of control solution in hemorrhagic shock. BHB and its products of metabolism are identified in serum of animals subjected to shock and treated with BHB/M. Further preclinical studies are needed to clarify the mechanisms of action of this promising treatment strategy.

Prolonged hypoxemia and acidemia in anesthetized pigs: a model for research on extracorporeal organ support in an intensive care setting

PURPOSE

Hypoxemia and acidemia (hypoxemia/acidemia) are serious complications in the critically ill and often occur in unstable patients exposed to extracorporeal organ support. Still, little is known about the biocompatibility interactions of hypoxemia/acidemia with extracorporeal circuits (ECC). Existing animal models often include the release of mediator cascades (sepsis-, lung injury models) or are based on small laboratory animals. We established a porcine model of hypoxemia/acidemia without an underlying disease and further challenged the situation with an extracorporeal circuit (ECC).

METHODS

Hypoxemia/acidemia were induced (3.5 h) and maintained (3 h) in anesthetized pigs (40 kg) by a stepwise reduction in oxygenation, infusion of 0.4 mol.l⁻¹ lactic and hydrochloric acid and by low tidal volume ventilation, targeting an PaO₂ < 70 mmHg, SvO₂ < 65%, pH ~ 7.2. Venovenous hemofiltration (CVVH) operated in recirculation mode without volume exchange was chosen to prove the suitability of the model for studies on ECCs under clinical conditions (ECC group, n=6). Another 6 animals underwent the same protocol except for the CVVH (reference group, n=6).

RESULTS

The median PaO₂ during hypoxemia/acidemia was 62 mmHg, the median SvO₂ was 38%, and the median pH was 7.22. Hypoxemia/acidemia was successfully induced and maintained for 6.5 h in all pigs. CVVH could be performed for 3 h with blood flow rates up to 300 ml.min⁻¹ and filtrate rates up to 60 ml.min⁻¹.

CONCLUSIONS

Our model provides hypoxemia/acidemia with blood gas values comparable to critically ill adult patients for several hours, during which it is possible to perform CVVH. Thus, it enables research on the biocompatibility reactions of extracorporeal circuits under intensive care conditions.

A Prospective Randomized Pilot Study of Near-Infrared Spectroscopy-Directed Restricted Fluid Therapy versus Standard Fluid Therapy in Patients Undergoing Elective Colorectal Surgery

There are substantial data supporting the concept that algorithms that effectively limit fluid volumes to patients undergoing elective surgery, particularly intraoperatively, significantly reduce perioperative morbidity. We hypothesized that intraoperative fluid limitation could be safely accomplished when guided by near-infrared spectroscopy (NIRS) monitoring, and that this fluid restriction regimen would result in a reduction in postoperative morbidity when compared with standard monitoring and fluid therapy. The intent of this pilot study was to demonstrate the feasibility and ease of conduct of this study protocol before expanding to the multicenter pivotal trial. We performed a prospective, (2:1) randomized, pilot study at two centers. A total enrollment of 24 fully evaluable patients undergoing elective open colorectal surgery (16 restricted, 8 standard) was planned. After providing informed consent, patients were randomized to standard fluid resuscitation (500 LR induction bolus, then LR 7 mL/kg/h X 1 h, then 5 mL/kg/h) or restricted fluid resuscitation (no induction bolus, then LR 2 mL/kg/h). Subsequent fluid bolus infusions were guided by physiologic parameters (systolic blood pressure < 90 mm Hg, heart rate > 100 bpm, or oliguria) in the standard group, and by tissue oxygen saturation from NIRS (tissue oxygen saturation (StO2) < 75%, or 20% below baseline; or the same physiologic parameters) in the restricted group. Primary endpoints were major postoperative complications. A total of 27 patients were randomized (18 restricted, 9 standard). Age, gender, ethnicity, past medical history, and body mass index were similar. American Society of Anesthesiologists class was somewhat higher in the restricted group (American Society of Anesthesiologists class 3 in 77% of restricted vs 44% of standard patients; P = 0.194). Median total intraoperative fluids were less in the restricted group (1300 mL) when compared with the standard group (3014 mL) ( P = 0.021). Total fluids for the hospitalization were also statistically significantly decreased in the restricted group. Complications occurred in about two-thirds of patients, and complication rates were not statistically different between groups (1.6/restricted patient vs 2.1/standard patient; P = 0.333). Primary indications for boluses (n = 93) given to study patients were: hypotension (69%); oliguria (15%); and tachycardia (14%), with multiple indications per bolus. In only two instances did the StO2 drop to less than 75 per cent, or decrease by 20 per cent from baseline in the 3 minutes before bolus as an indication for fluid administration. Patients undergoing elective colorectal surgery with a fluid restricted strategy had only rare episodes of decreased StO2, suggesting that adequate tissue perfusion was maintained in this group. As a result, NIRS monitoring did not significantly influence intraoperative fluid management of patients undergoing colorectal surgery.

Hemodynamic support of the trauma patient

PURPOSE OF REVIEW

The aim of this review is to address and summarize some key issues and recent insights into the hemodynamic support of the trauma patient related to fluid administration.

RECENT FINDINGS

Colloids are not superior to crystalloids in treating hypovolemia in the trauma patient and show no survival benefit. Furthermore, several adverse effects (renal failure, bleeding complications and anaphylaxis) have been reported with the use of artificial colloids. Hypertonic saline is effective and well tolerated in the treatment of hypovolemic shock and traumatic brain injury. Potential benefits are reduced fluid requirements and immune modulation. Resuscitation strategies should depend on the type of injury (penetrating vs. blunt; concomitant brain injury). Excessive fluid resuscitation, which can cause acute respiratory distress syndrome, abdominal compartment syndrome and brain edema, should be avoided. Dynamic parameters to guide volume therapy are probably more reliable than static parameters and minimally invasive techniques to monitor the microcirculation are becoming more important to determine the endpoints of resuscitation.

SUMMARY

Hemodynamic support is an early goal in the treatment of the trauma patient. The use of crystalloids is currently recommended in trauma resuscitation. The amount of fluid we give should be tailored to the individual trauma patient in which clear endpoints of resuscitation are of vital importance to maximize the chances of survival.

Functional comparison of hemoglobin purified by different methods and their biophysical implications

Hemoglobin (Hb) that is purified from red blood cells (RBCs) is commonly subjected to harsh processing conditions, such as high temperatures and extensive column separation, which may damage the Hb by altering the heme prosthetic group and/or the Hb protein structure. In this study, bovine and human Hb purified by tangential flow filtration (TFF) was compared to commercial preparations of human Hb (Hemosol, Inc., Toronto, Canada) and bovine Hb (Biopure, Inc., Cambridge, MA). Purified Hbs were characterized by measuring their overall purity (SDS-PAGE, SEC, and ESI-MS), susceptibility to oxidation (k(ox)), responses to physiological conditions (pH, [Cl(-)], [IHP], and T), and ligand binding kinetics (O(2), NO, and CO). All Hbs evaluated possessed comparable biophysical properties, however, a small amount of catalase was detected in the TFF-purified Hbs that reduced the rate of autoxidation. Mass changes observed by mass spectrometry suggest that structural alterations may be introduced into Hbs that are purified by extensive chromatographic separations. These results demonstrate that TFF is a suitable process for the purification of Hb from RBCs with a quality equivalent to that of commercial Hb preparations that employ more extensive purification strategies. This work also shows that TFF can yield highly pure Hb which can be used for Hb-based O(2) carrier synthesis.

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.

Nitroglycerin attenuates vasoconstriction of HBOC-201 during hemorrhagic shock resuscitation

BACKGROUND

Vasoconstriction, an inherent property of Hemoglobin Based Oxygen Carriers (HBOC) potentially due to nitric oxide (NO) scavenging, may increase cardiovascular complications in HBOC resuscitated trauma patients. The purpose of this study was to determine if co-administration of a weak NO donor, intravenous nitroglycerin (NTG), with HBOC-201 during resuscitation from hemorrhagic shock could safely attenuate HBOC-201 vasoconstriction.

METHODS AND RESULTS

Hemorrhagic shock was induced in 44 swine randomized to receive fluid resuscitation with HBOC, HBOC+NTG10 mcg/kg/min, HBOC+NTG20 mcg/kg/min, HBOC+NTG40 mcg/kg/min, Hetastarch (HES), HES+NTG20 mcg/kg/min, NTG20 mcg/kg/min and Lactated Ringers (LR). HBOC resuscitation from hemorrhagic shock increased mean arterial pressure (MAP=94+/-33 mmHg), mean pulmonary artery pressure (MPAP=29+/-11 mmHg) and systemic vascular resistance (SVR=2684+/-871 dyns/cm(5)) in comparison to HES. Co-administration of NTG during HBOC resuscitation attenuated vasoconstriction with HBOC+40 mcg/kg/min demonstrating the most robust reduction in vasoconstriction (MAP=59+/-23 mmHg, MPAP=18+/-7 mmHg, and SVR=1827+/-511 dyns/cm(5)), although the effects were transient. Co-administration of NTG with HBOC did not alter base deficit, lactate, methemoglobin levels, nor cause profound hypotension during resuscitation.

CONCLUSION

Nitroglycerin attenuates vasoconstrictive properties of HBOC when co-administered during resuscitation in this swine model of hemorrhagic shock. Translational survival studies are required to determine if this strategy of attenuation of the vasoconstriction of HBOC-201 reduces cardiovascular complications and improves outcome with HBOC fluid resuscitation for hemorrhagic shock.

A prospective, randomized comparison of Oxyglobin (HB-200) and packed red blood cell transfusion for canine babesiosis

OBJECTIVE

To establish the efficacy of Oxyglobin (HB-200) in canine babesiosis and compare it to standard therapy, packed red blood cell transfusion (pRBCT) with respect to improvements in specific parameters of blood gas, acid-base, blood pressure, and subjective evaluations.

DESIGN

Prospective, randomized, clinical trial.

SETTING

Onderstepoort Veterinary Academic Hospital.

ANIMALS

Twelve dogs (8-25 kg) naturally infected with Babesia rossi and a hematocrit of 0.1-0.2 L/L (10-20%).

INTERVENTIONS

Treatment groups were randomized to receive either 20 mL/kg of Oxyglobin or pRBCT over 4 hours via a central venous catheter. Transfusions were followed by lactated Ringer's solution infusion. Rectal temperature, femoral arterial and mixed venous blood sampling, oscillometric blood pressure, and subjective assessment of patient status (habitus), and appetite were performed at time points 0, 1, 4, 8, 24, 48, and 72 hours.

MAIN RESULTS

Dogs presented with a hypoalbuminemic alkalosis; hyperchloremic, dilutional acidosis; normotensive tachycardia; pyrexia; depression; and anorexia. Both treatments produced similar results, with the exception of significant differences in pH (4 h); PCO(2) (4 h); hemoglobin (8 h, 24 h); mean arterial pressure (48 h); albumin (4 h, 8 h); habitus (8 h, 48 h); and appetite (24 h). Arterial O(2) content was higher for pRBCT than Oxyglobin at 72 hours, but central venous PO(2) did not differ between groups or over time and was consistently subnormal.

CONCLUSIONS

Oxyglobin provides similar overall improvements to pRBCT in dogs with anemia from babesiosis, with respect to blood gas, acid-base and blood pressure, although patients receiving packed cells tended to have more rapid normalization of habitus and appetite.

Influence of the Hemoglobin Solution HBOC-201 on Tissue Oxygenation in the Rat R1H-Tumor

BACKGROUND

HBOC-201 is an ultra purified bovine hemoglobin solution. It has already been used in clinical phase II/III trials for emergency treatments. Animal experiments have shown that HBOC-201 is highly effective in tissue oxygenation. The study was performed in order to assess the potential of low dose HBOC-201 to improve tumor oxygenation.

METHODS

30 rats with a subcutaneously growing rhabdomyosarcoma R1H tumor were randomly assigned either to be ventilated with carbogen (n = 10), or to receive an IV injection of 0.3 g/kg HBOC-201 (n = 10) or a combination of 0.3 g/kg HBOC-201 and carbogen breathing (n = 10). Under general anesthesia the effects of the respective treatment on the tissue oxygen tension (tpO2) of the tumor were determined using a flexible stationary probe at baseline (b) and 15 and 60 min after application of the respective medication.

RESULTS

HBOC-201 alone failed to improve tumor tpO2 (b: 1.3 +/- 1.2mmHg; 15min: 1.4 +/- 1 mmHg; 60min: 1 +/- 1 mmHg). In combination with carbogen the mean tpO2 of the tumor raised in comparison to baseline values (b: 3.1 +/- 4.6 mmHg; mmHg; 15min: 8.5 +/- 11*mmHg; 60min: 4.8 +/- 5mmHg; *p < 0.05 vs. b), but this effect was less pronounced than the increase in tpO2 by carbogen alone (b: 3.4 +/- 3.4mmHg; 15min: 9 +/- 10* mmHg; 60 min: 13 +/- 19* mmHg; *p < 0.05 vs. b).

CONCLUSION

The application of low dose hemoglobin solution HBOC-201 does not result in improvement of tissue oxygenation in the rat rhabdomyosarcoma R1H.

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.

Apoptosis and haemorrhagic shock

Abstract

This is a review paper that provides an overview of current information on programmed cell death in haemorrhagic shock, including the identification of different molecular receptor signals. A PubMed search for all dates was undertaken using the search terms apoptosis, trauma and haemorrhagic shock. Original research, sentinel and review papers from peer-reviewed journals were included for identification of key concepts. Haemorrhagic shock remains a primary cause of death in civilian and military trauma. Apoptosis is accelerated following haemorrhagic shock. Many methods are used to detect and quantify apoptosis. Fluid resuscitation regimens vary in their effect on the extent of apoptosis. Investigators are examining the effects of haemorrhagic shock and fluid resuscitation on apoptotic signalling pathways. Molecular information is becoming available and being applied to the care of patients experiencing haemorrhagic shock, making it essential for nurses and other health care providers to consider the mechanisms and consequences of apoptosis.

Bench-to-bedside review: latest results in hemorrhagic shock

Hemorrhagic shock is a leading cause of death in trauma patients worldwide. Bleeding control, maintenance of tissue oxygenation with fluid resuscitation, coagulation support, and maintenance of normothermia remain mainstays of therapy for patients with hemorrhagic shock. Although now widely practised as standard in the USA and Europe, shock resuscitation strategies involving blood replacement and fluid volume loading to regain tissue perfusion and oxygenation vary between trauma centers; the primary cause of this is the scarcity of published evidence and lack of randomized controlled clinical trials. Despite enormous efforts to improve outcomes after severe hemorrhage, novel strategies based on experimental data have not resulted in profound changes in treatment philosophy. Recent clinical and experimental studies indicated the important influences of sex and genetics on pathophysiological mechanisms after hemorrhage. Those findings might provide one explanation why several promising experimental approaches have failed in the clinical arena. In this respect, more clinically relevant animal models should be used to investigate pathophysiology and novel treatment approaches. This review points out new therapeutic strategies, namely immunomodulation, cardiovascular maintenance, small volume resuscitation, and so on, that have been introduced in clinics or are in the process of being transferred from bench to bedside. Control of hemorrhage in the earliest phases of care, recognition and monitoring of individual risk factors, and therapeutic modulation of the inflammatory immune response will probably constitute the next generation of therapy in hemorrhagic shock. Further randomized controlled multicenter clinical trials are needed that utilize standardized criteria for enrolling patients, but existing ethical requirements must be maintained.

Use of hemoglobin-based oxygen-carrying solution-201 to improve resuscitation parameters and prevent secondary brain injury in a swine model of traumatic brain injury and hemorrhage: laboratory investigation

OBJECT

Traumatic brain injury (TBI) often occurs as part of a multisystem trauma that may lead to hemorrhagic shock. Effective resuscitation and restoration of oxygen delivery to the brain is important in patients with TBI because hypotension and hypoxia are associated with poor outcome in head injury. We studied the effects of hemoglobin-based oxygen-carrying (HBOC)-201 solution compared with lactated Ringer (LR) solution in a large animal model of brain injury and hemorrhage, in a blinded prospective randomized study.

METHODS

Swine underwent brain impact injury and hemorrhage to a mean arterial pressure (MAP) of 40 mm Hg. Twenty swine were randomized to undergo resuscitation with HBOC-201 (6 ml/kg) or LR solution (12 ml/kg) and were observed for an average of 6.5 +/- 0.5 hours following resuscitation. At the end of the observation period, magnetic resonance (MR) imaging was performed. Histological studies of swine brains were performed using Fluoro-Jade B, a marker of early neuronal degeneration.

RESULTS

Swine resuscitated with HBOC-201 had higher MAP, higher cerebral perfusion pressure (CPP), improved base deficit, and higher brain tissue oxygen tension (PbtO(2)) than animals resuscitated with LR solution. No significant difference in total injury volume on T2-weighted MR imaging was observed between animals resuscitated with HBOC-201 solution (1155 +/- 374 mm(3)) or LR solution (1246 +/- 279 mm(3); p = 0.55). On the side of impact injury, no significant difference in the mean number of Fluoro-Jade B-positive cells/hpf was seen between HBOC-201 solution (61.5 +/- 14.7) and LR solution (48.9 +/- 17.7; p = 0.13). Surprisingly, on the side opposite impact injury, a significant increase in Fluoro-Jade B-positive cells/hpf was seen in animals resuscitated with LR solution (42.8 +/- 28.3) compared with those resuscitated with HBOC-201 solution (5.6 +/- 8.1; p < 0.05), implying greater neuronal injury in LR-treated swine.

CONCLUSIONS

The improved MAP, CPP, and PbtO(2) observed with HBOC-201 solution in comparison with LR solution indicates that HBOC-201 solution may be a preferable agent for small-volume resuscitation in brain-injured patients with hemorrhage. The use of HBOC-201 solution appears to decrease cellular degeneration in the brain area not directly impacted by the primary injury. Hemoglobin-based oxygen-carrying-201 solution may act by improving cerebral blood flow or increasing the oxygen-carrying capacity of blood, mitigating a second insult to the injured brain.

Immune effects of decreasing low-molecular weight hemoglobin components of hemoglobin-based oxygen carriers (HBOC) in a swine model of severe controlled hemorrhagic shock

Hemoglobin-based oxygen carriers (HBOCs) show potential as safe, efficacious, pre-hospital resuscitation fluids. The major criticism of HBOC-201 is its vasoactive property, attributed partially to low-molecular weight (low-MW) tetrameric/dimeric (TD) hemoglobin (Hb) in HBOC solution. Here we sought to determine whether resuscitation with decreasing concentrations of low-MW Hb component of HBOC affects immune responses in hemorrhagic swine. 28 anesthetized swine underwent a soft muscle crush and controlled hemorrhage of 55% blood volume, followed by resuscitation with HBOC containing 31%, 2%, or 0.4% low-MW Hb in four 10 ml/kg infusions at 20, 30, 45 and 60 minutes before hospital arrival at 75 minutes. IL-10, cell activation and adhesion markers and CD4:CD8 ratio remained unchanged in all 3 groups compared to baseline. Leukocyte apoptosis was equally elevated across all groups. Purification from 31% to 0.4% low-MW Hb in HBOC solution did not alter immune effects in a swine model of severe controlled hemorrhagic shock.

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.

Tissue oxygen monitoring in rodent models of shock

Tissue Po2 (tPo2) reflects the balance between local O2 supply and demand and, thus, could be a useful monitoring modality. However, the consistency and amplitude of the tPo2 response in different organs during different cardiorespiratory insults is unknown. Therefore, we investigated the effects of endotoxemia, hemorrhage, and hypoxemia on tPo2 measured in deep and peripheral organ beds. We compared arterial pressure, blood gas and lactate levels, descending aortic and renal blood flow, and tPo2 in skeletal muscle, bladder epithelium, liver, and renal cortex during 1) LPS infusion (10 mg/kg), 2) sequential removal of 10% of circulating blood volume, and 3) reductions in inspired O2 concentration in an anesthetized Wistar rat model with values measured in sham-operated animals. Different patterns were seen in each of the shock states, with condition-specific variations in the degree of acidemia, lactatemia, and tissue O2 responses between organs. Endotoxemia resulted in a rise in bladder tPo2 and an early fall in liver tPo2 but no significant change in muscle and renal cortical tPo2. Progressive hemorrhage, however, produced proportional declines in liver, muscle, and bladder tPo2, but renal cortical tPo2 was maintained until profound blood loss had occurred. By contrast, progressive hypoxemia resulted in proportional decreases in tPo2 in all organ beds. This study highlights the heterogeneity of responses in different organ beds during different shock states that are likely related to local changes in O2 supply and utilization. Whole body monitoring is not generally reflective of these changes.

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.

Continuous Muscle Tissue Oxygenation in Critically Injured Patients: A Prospective Observational Study

BACKGROUND

Despite normalization of vital signs, critically injured patients may remain in a state of occult underresuscitation that sets the stage for sepsis, organ failure, and death. A continuous, sensitive, and accurate measure of resuscitation after injury remains elusive.

METHODS

In this pilot study, we evaluated the ability of two continuous measures of peripheral tissue oxygenation in their ability to detect hypoperfusion: the Licox polarographic tissue oxygen monitor (PmO2) and the InSpectra near-infrared spectrometer (StO2). We hypothesized that deltoid muscle tissue oxygenation measurements could detect patients in "occult shock" who are at increased risk for post-injury complications. The study was designed to (1) define values for PmO2 and StO2 in patients who by all standard measures appeared to be clinically resuscitated; (2) evaluate the relationship between PmO2, StO2 and other physiologic variables including mean arterial pressure (MAP), lactate and base deficit (BD); and (3) examine the relationship between early low tissue oxygen values and the subsequent development of infections and organ dysfunction. Licox probes were inserted into the deltoid muscle of critically injured patients after initial surgical and radiologic interventions, and transcutaneous StO2 monitors were applied over the same muscle bed. PmO2, StO2, and standard physiologic data were collected continuously using a multimodal bioinformatics system.

RESULTS

Twenty-eight critically injured patients were enrolled in this study at admission to the intensive care unit (ICU). For patients who appeared to be well resuscitated (defined as MAP > or = 70 mm Hg, heart rate [HR] < or = 110 bpm, BD > or = -2, and partial pressure of arterial oxygen (PaO2) = 80 and 150 mm Hg), the mean PmO2 was 34 +/- 11 mm Hg and StO2 was 63 +/- 27%. There was a strong relationship between PmO2 and BD (p < 0.001) but no significant relationship between StO2 and BD. The relationship between PmO2 and StO2 was weak but statistically significant. Early low values of both PmO2 and StO2 identified patients at risk for infectious complications or multiple organ failure (MOF). In patients who were well resuscitated by standard continuous parameters (HR and MAP), low PmO2 during the first 24 hours after admission (PmO2 < or = 25 for at least 2 hours) was strongly associated with the development of infectious complications (Odds Ratio = 16.5, 95% CI 1.49 to 183, p = 0.02).

CONCLUSIONS

PmO2 is a responsive, reliable and continuous monitor of changes in base deficit. Initial low values for either PmO2 or StO2 were associated with post-injury complications. PmO2 monitoring may be useful in identifying patients in the state of occult underresuscitation who remain at risk for developing infection and MOF.

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.

A single bolus of 3% hypertonic saline with 6% dextran provides optimal initial resuscitation after uncontrolled hemorrhagic shock

BACKGROUND

The optimal fluid for early resuscitation of hemorrhagic shock would restore perfusion without increasing blood loss, hypothermia, acidosis, or coagulopathy. This study examined effects of a single bolus of hypertonic saline (HTS) with or without (+/-) dextran (D) after uncontrolled hemorrhage (UH) and determined optimal fluid composition.

METHODS

Fifty swine were anesthetized and underwent invasive line placement, celiotomy, splenectomy, suprapubic catheterization, and grade V liver injury. After 30 minutes of UH, blinded fluid resuscitation was initiated with a 250-mL bolus. Animals were randomized to five groups: normal saline (NS), 3% HTS (3%), 3% HTS/6% D (3% D), 7.5% HTS (7.5%), or 7.5% HTS/6% D (7.5% D). Mean arterial pressure (MAP) and tissue oxygen saturation (StO2) were recorded. Laboratory and thrombelastography (TEG) data were collected every 30 minutes. Animals were sacrificed 120 minutes after injury. Analysis of variance was used to compare groups. Significance was defined as p < 0.05.

RESULTS

Baseline characteristics and laboratory values were similar in all groups. All groups achieved a similar degree of shock. Two NS and two 3% animals did not survive to 120 minutes. Fluids containing dextran produced a significantly greater increase in MAP (p < 0.02). Animals receiving 3% D maintained a higher MAP 90 minutes after fluid bolus. Also, 7.5% +/- D produced a significantly greater initial increase in StO2 (p < 0.05). This effect declined after fluid bolus while 3% D continued to improve tissue oxygenation. Significant differences developed between groups in TEG values, hematocrit, fibrinogen, urine sodium, serum sodium, serum chloride, and urine output.

CONCLUSIONS

A single bolus of 3% D after uncontrolled hemorrhagic shock produces an adequate and sustained rise in MAP and StO2 and attenuates hypercoagulability. Resuscitation with 7.5% +/- D produces significantly increased urine output accompanied by a decline in MAP and StO2 over time. A single bolus of 7.5% D results in significant dilutional anemia and relative hypofibrinogenemia.

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.

Enhanced central organ oxygenation after application of bovine cell-free hemoglobin HBOC-201

PURPOSE

While the effects of dilutional anemia or isovolemic hemodilution (IHD) on the oxygen extraction and tissue oxygenation in peripheral organs after application of hemoglobin-based oxygen carriers like HBOC-201 have been studied intensively, little is known about tissue oxygenation properties of hemoglobin solutions in central organs like the liver.

METHODS

Twelve Foxhounds were anesthetized and then randomized to either a control group without hemodilution (Group 1) or underwent first step isovolemic hemodilution (pulmonary artery occlusion pressure constant) with Ringer's solution (Group 2) to a hematocrit of 25% with second step infusion of HBOC-201 until a hemoglobin concentration of +0.6 g.dL(-1) was reached. Tissue oxygen tensions (tpO2) were measured in the gastrocnemius muscle using a polarographic needle probe, and in the liver using a flexible polarographic electrode.

RESULTS

While arterial oxygen content and oxygen delivery decreased with hemodilution in Group 2, global liver and muscle oxygen extraction ratio increased after hemodilution and additional application of HBOC-201. Hemodilution and application of HBOC-201 provided augmentation of the mean liver tpO2 (baseline: 48 +/- 9, 20 min: 53 +/- 10, 60 min: 67 +/- 11*, 100 min: 68 +/- 7*; *P < 0.05 vs baseline and Group 1), while oxygen tensions in Group 1 remained unchanged. Oxygen tension in the skeletal muscle increased after hemodilution and additionally after application of HBOC-201 in comparison to baseline and to the control group (P < 0.05).

CONCLUSION

In the present animal model, IHD with Ringer's solution and additional application of HBOC-201 increased oxygen extraction and tpO(2) in the liver and skeletal muscle, in parallel and in comparison with baseline values and a control group.

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.

Bench-to-bedside review: oxygen debt and its metabolic correlates as quantifiers of the severity of hemorrhagic and post-traumatic shock

Evidence is increasing that oxygen debt and its metabolic correlates are important quantifiers of the severity of hemorrhagic and post-traumatic shock and and may serve as useful guides in the treatment of these conditions. The aim of this review is to demonstrate the similarity between experimental oxygen debt in animals and human hemorrhage/post-traumatic conditions, and to examine metabolic oxygen debt correlates, namely base deficit and lactate, as indices of shock severity and adequacy of volume resuscitation. Relevant studies in the medical literature were identified using Medline and Cochrane Library searches. Findings in both experimental animals (dog/pig) and humans suggest that oxygen debt or its metabolic correlates may be more useful quantifiers of hemorrhagic shock than estimates of blood loss, volume replacement, blood pressure, or heart rate. This is evidenced by the oxygen debt/probability of death curves for the animals, and by the consistency of lethal dose (LD)_25,50 points for base deficit across all three species. Quantifying human post-traumatic shock based on base deficit and adjusting for Glasgow Coma Scale score, prothrombin time, Injury Severity Score and age is demonstrated to be superior to anatomic injury severity alone or in combination with Trauma and Injury Severity Score. The data examined in this review indicate that estimates of oxygen debt and its metabolic correlates should be included in studies of experimental shock and in the management of patients suffering from hemorrhagic shock.

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.

Toxicities of hemoglobin solutions: in search of in-vitro and in-vivo model systems

Several hemoglobin-based oxygen carriers (HBOCs) have been developed with a rationale focused on exploiting one or more physicochemical properties (e.g., oxygen affinity, molecular weight, viscosity, and colloid osmotic pressure) resulting from the chemical or recombinant modification of hemoglobin (Hb). Several chemically modified Hbs have reached late stages of clinical evaluation in the United States and Canada. These Hbs, in general, demonstrated mixed preclinical safety and efficacy, and reasonable safety in Phase I trials. However, as clinical development shifted into later stages, an undesirable safety and efficacy profile became clear in patient populations studied, and as a result some products were withdrawn from further clinical pursuit. Several questions still remain unanswered regarding the safety of Hb products for their proposed clinical indication(s). For example, 1) were preclinical studies predictive of clinical outcome? And, 2) were the most appropriate preclinical studies performed to predict clinical outcome? The primary objectives of this analysis are to explore prelinical safety issues associated with HBOCs and provide an overview of the in-vitro and in-vivo models employed. The methods for obtaining data to serve as a basis for discussion are compiled from a literature-based survey of safety and efficacy derived from biochemical, cellular, and whole animal assessment of HBOCs. Results from this overview of a vast body of published data may provide a means for identifying critical preclinical safety issues, which may ultimately lead to identification of potential limitations in the effective clinical use of certain HBOCs.