The effects of diaspirin cross-linked hemoglobin in sepsis

Human-specific CHRFAM7A primes macrophages for a heightened pro-inflammatory response at the earlier stage of inflammation

α7-Nicotinic acetylcholine receptor (α7-nAChR) is the key effector molecule of the cholinergic anti-inflammatory pathway. Evolution has evolved a uniquely human α7-nAChR encoded by CHRFAM7A. It has been demonstrated that CHRFAM7A dominant negatively regulates the functions of α7-nAChR. However, its role in inflammation remains to be fully characterized. CHRFAM7A transgenic (Tg) mice were phenotypically normal and their peritoneal macrophages exhibited decreased ligand-binding capability and, importantly, an activated gene expression profile of pro-inflammatory cytokines. Surprisingly, when challenged with sepsis, the Tg mice showed no survival disadvantage relative to their wild-type (Wt) counterparts. Further analysis showed that the complete blood count and serum levels of pro-inflammatory cytokines were comparable at resting state, but the degrees of leukocyte mobilization and the increase of pro-inflammatory cytokines were significantly higher in Tg than Wt mice at the early stage of sepsis. In vitro, peritoneal macrophages of the Tg mice exhibited an exaggerated response to lipopolysaccharides (LPSs), especially at the earlier time points and at lower dosages of LPS. Remarkably, monocytes from CHRFAM7A-carrier showed similar dynamic changes of the pro-inflammatory cytokines to that observed in the Tg mice upon LPS challenge. Our results suggest that CHRFAM7A increases the mobilization of leukocytes and primes macrophages that confer an enhanced immune response at the early stage of inflammation, which may lead to prompt pathogen clearance, an evolutionary advantage in less severe inflammatory conditions.

Advances in Rodent Experimental Models of Sepsis

In the development of therapeutic strategies for human diseases, preclinical experimental models have a key role. However, the preclinical immunomodulatory therapies developed using rodent sepsis were not successful in human clinical trials. Sepsis is characterized by a dysregulated inflammation and redox imbalance triggered by infection. Human sepsis is simulated in experimental models using methods that trigger inflammation or infection in the host animals, most often mice or rats. It remains unknown whether the characteristics of the host species, the methods used to induce sepsis, or the molecular processes focused upon need to be revisited in the development of treatment methods that will succeed in human clinical trials. Our goal in this review is to provide a survey of existing experimental models of sepsis, including the use of humanized mice and dirty mice, and to show how these models reflect the clinical course of sepsis. We will discuss the strengths and limitations of these models and present recent advances in this subject area. We maintain that rodent models continue to have an irreplaceable role in studies toward discovering treatment methods for human sepsis.

Resuscitation with PEGylated carboxyhemoglobin preserves renal cortical oxygenation and improves skeletal muscle microcirculatory flow during endotoxemia

PEGylated carboxyhemoglobin (PEGHbCO), which has carbon monoxide-releasing properties and plasma expansion and oxygen-carrying properties, may improve both skeletal microcirculatory flow and renal cortical microcirculatory Po₂ (CµPo₂) and, subsequently, limit endotoxemia-induced acute kidney injury. Anesthetized, ventilated Wistar albino rats (n = 44) underwent endotoxemic shock. CµPo₂ was measured in exposed kidneys using a phosphorescence-quenching method. Rats were randomly assigned to the following five groups: 1) unresuscitated lipopolysaccharide (LPS), 2) LPS + Ringer's acetate (RA), 3) LPS + RA + 0.5 µg·kg·^-1min^-1 norepinephrine (NE), 4) LPS + RA + 320 mg/kg PEGHbCO, and 5) LPS + RA + PEGHbCO + NE. The total volume was 30 mL/kg in each group. A time control animal group was used. Skeletal muscle microcirculation was assessed by handheld intravital microscopy. Kidney immunohistochemistry and myeloperoxidase-stained leukocytes in glomerular and peritubular areas were analyzed. Endotoxemia-induced histological damage was assessed. Plasma levels of IL-6, heme oxygenase-1, malondialdehyde, and syndecan-1 were assessed by ELISA. CµPo₂ was higher in the LPS + RA + PEGHbCO-resuscitated group, at 35 ± 6mmHg compared with 21 ± 12 mmHg for the LPS+RA group [mean difference: -13.53, 95% confidence interval: (-26.35; -0.7156), P = 0.035]. The number of nonflowing, intermittent, or sluggish capillaries was smaller in groups infused with PEGHbCO compared with RA alone (P < 0.05), while the number of normally perfused vessels was greater (P < 0.05). The addition of NE did not further improve CµPo₂ or microcirculatory parameters. Endotoxemia-induced kidney immunohistochemistry and histological alterations were not mitigated by PEGHbCO 1 h after resuscitation. Renal leukocyte infiltration and plasma levels of biomarkers were similar across groups. PEGHbCO enhanced CµPo₂ while restoring skeletal muscle microcirculatory flow in previously nonflowing capillaries. PEGHbCO should be further evaluated as a resuscitation fluid in mid- to long-term models of sepsis-induced acute kidney injury.

The Influence of Pain and Analgesia in Rodent Models of Sepsis

Sepsis is a multifaceted host response to infection that dramatically affects patient outcomes and the cost of health care. Animal models are necessary to replicate the complexity and heterogeneity of clinical sepsis. However, these models entail a high risk of pain and distress due to tissue trauma, inflammation, endotoxin-mediated hyperalgesia, and other mechanisms. Several recent studies and initiatives address the need to improve the welfare of animals through analgesics and standardize the models used in preclinical sepsis research. Ultimately, the goal is to provide high-fidelity, humane animal models that better replicate the clinical course of sepsis, to provide more effective translation and advance therapeutic discovery. The purpose of this review is to discuss the current understanding of the roles of pain and analgesia in rodent models of sepsis. The current definitions of sepsis along with an overview of pain in human sepsis are described. Finally, welfare concerns associated with animal models of sepsis and the most recent considerations for relief of pain and distress are reviewed.

Transfusion of the injured patient: proceed with caution

Transfusion of the injured patient with packed red blood cells (PRBCs) is a dynamic process requiring vigilance during the acute resuscitative and recovery phases postinjury. Although adverse events have been reported in 2% to 10% of injured patients, the advent of new detection techniques for viral pathogens has markedly decreased the risk of infectious transmission. However, transfusions are strongly associated with immunosuppression in the host, which may occur days after the initial injury and may lead to bacterial infections. Conversely, early transfusion of stored PRBCs, > 6 units in the first 12 h postinjury, contributes to an early state of hyperinflammation that is a strong, independent predictor of multiple organ failure (MOF) in those patients with intermediate injury severity scores. The roles of prestorage leukoreduction are also reviewed with respect to the promotion of both immunosuppression and hyperinflammation. We further summarize studies with hemoglobin substitutes, whose use may obviate many of the untoward events of transfusion and promise to lead to better outcomes for injured patients.

Temporal effect of hemoglobin resuscitation on sepsis survival

Hemoglobin (Hb)-based oxygen carriers are promising resuscitation fluids for hemorrhagic shock. However, infusion of large amounts of Hb-based material could interfere with reticuloendothelial function potentiating postresuscitation sepsis mortality. We investigated the temporal relationship between hemorrhage-resuscitation and sepsis survival. Male SD rats were subjected to hemorrhage and resuscitated with shed blood volumes of purified human hemoglobin solution (HS). Sepsis was induced by cecal ligation and puncture (CLP) 24 h before, 0, 24, or 72 h after hemorrhage/resuscitation (H/R) and survival was monitored. In additional animals with or without Hb resuscitation, hepatic heme oxygenase-1 (HO-1) gene expression and HO activity were assessed. Seven-day survival for animals resuscitated with HS prior to sepsis induction was significantly higher than other groups. Animals resuscitated with HS showed hepatic HO-1 gene expression while non-HS resuscitated animals did not. In addition, hepatic HO activity levels were significantly higher in HS resuscitated animals than non-HS resuscitated animals. In conclusion, HS resuscitation does not appear to enhance postresuscitation sepsis mortality. Rather, when conducted concomitantly or prior to sepsis, HS resuscitation appears to improve survival from a subsequent sepsis challenge.

Therapeutic potential for transient inhibition of adenosine deaminase in systemic inflammatory response syndrome

OBJECTIVE

We sought to determine the potential usefulness of 2'-deoxycoformycin (pentostatin), an inhibitor of adenosine deaminase, as a postinsult, or prophylactic treatment for systemic inflammatory response syndrome resulting from fecal peritonitis.

DESIGN

Prospective, randomized, controlled experiment.

SETTING

Small animal basic science laboratory.

SUBJECTS

Male Spague-Dawley rats, weighing 300 to 350 g.

INTERVENTIONS

Rats with fecal peritonitis (intraperitoneal cecal slurry) were treated with 1 mg/kg pentostatin intraperitoneally 24 hrs before, or intravenously when signs of illness presented (2 hrs after induction of peritonitis). Signs of illness included tachycardia, tachypnea, and leukopenia. All rats received 50 mL/kg 0.9% saline resuscitative fluid at 2 hrs.

MEASUREMENTS AND MAIN RESULTS

Survival to day 6 was 100% in nonseptic sham rats, but 33% in untreated septic rats. In rats given pentostatin either 2 hrs after the insult, or 24 hrs before the insult, 6-day survival improved to 81% and 78%, respectively. Histology revealed diffuse peritonitis, and evidence of systemic inflammatory response syndrome, including local and distant site vascular damage and leukocyte activation. These responses to the septic challenge were abrogated by pentostatin treatment. Return of significant amount of tissue adenosine deaminase activity by 24 hrs and later recovery of white blood cell counts argue against any potential for inappropriate immunosuppression by pentostatin.

CONCLUSIONS

These data indicate that the novel use of pentostatin to prevent systemic inflammatory response syndrome secondary to fecal peritonitis shows uncommon promise as a therapeutic tool. All indices of systemic inflammatory response syndrome were abrogated and survival improved when pentostatin was not given until after signs of the illness became manifest. Because protection was afforded with treatment 24 hrs in advance of the inciting insult, pentostatin also has the unique potential for use as a true prophylactic agent.

Inhibiting adenosine deaminase modulates the systemic inflammatory response syndrome in endotoxemia and sepsis

By pharmacological manipulation of endogenous adenosine, using chemically distinct methods, we tested the hypothesis that endogenous adenosine tempers proinflammatory cytokine responses and oxyradical-mediated tissue damage during endotoxemia and sepsis. Rats were pretreated with varying doses of pentostatin (PNT; adenosine deaminase inhibitor) or 8-sulfophenyltheophylline (8-SPT; adenosine receptor antagonist) and then received either E. coli endotoxin (lipopolysaccharide; 0.01 or 2.0 mg/kg) or a slurry of cecal matter in 5% dextrose in water (200 mg/kg). Resultant levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-10 were measured in serum and in liver and spleen. Untreated, 2 mg/kg lipopolysaccharide elevated serum TNF-alpha, IL-1beta, and IL-10. PNT dose dependently attenuated, without ablating, the elevation in serum TNF-alpha and IL-1beta and raised liver and spleen IL-10. PNT also attenuated elevation of TNF-alpha in serum, liver, and spleen at 4 and 24 h after sepsis induction, and 8-SPT resulted in higher proinflammatory cytokines. Modulating endogenous adenosine was also effective in exacerbated (8-SPT) or diminished (PNT) tissue peroxidation. Survival from sepsis was also improved when PNT was used as a posttreatment. These data indicate that endogenous adenosine is an important modulatory component of systemic inflammatory response syndromes. These data also indicate that inhibition of adenosine deaminase may be a novel and viable therapeutic approach to managing the systemic inflammatory response syndrome without ablating important physiological functions.

The hemodynamic effects of diaspirin cross-linked hemoglobin in dopamine-resistant endotoxic shock in swine

As the blood substitute Diaspirin Cross-linked Hemoglobin (DCLHb) has potent vasopressor activity, we assessed its hemodynamic effects in a clinically relevant dopamine-resistant endotoxic shock model in swine. In a randomized and controlled study, E. coli LPS was administered to anesthetized and invasively monitored swine. Group I (n = 3) control pigs were not resuscitated. Groups II (n = 5) and III (n = 6) pigs received dopamine (DA) after MAP decreased 30%, and hetastarch and DCLHb, respectively, after dopamine-resistance occurred. Progressive hemodynamic decline occurred in Group I pigs. DA failed to restore MAP to baseline. However, 0% and 67% of pigs also treated with heta-starch and DCLHb, respectively, achieved temporary restoration of baseline MAP (p = 0.03), prompting a reduction in the dose of DA in 0% of hetastarch vs. 50% of DCLHb treated pigs. Except for increased MPAP and decreased heart in DCLHb treated pigs (p<0.001), hemodynamics and survival were not different (p>0.05). In conclusion, although DCLHb exacerbated pulmonary hypertension and did not improve O2 utilization or survival, because DCLHb restored MAP to baseline and had a dopamine sparing effect, further investigation of DCLHb's hemodynamic effects in adrenergic agent-resistant endotoxemia is warranted.

Diaspirin cross-linked hemoglobin improves oxygen extraction capabilities in endotoxic shock

We studied the effects of diaspirin cross-linked hemoglobin (DCLHb), a cell-free hemoglobin derived from human erythrocytes, on blood flow distribution and tissue oxygen extraction capabilities in endotoxic shock. Eighteen pentobarbital sodium-anesthetized, mechanically ventilated dogs received 2 mg/kg of E. coli endotoxin, followed by saline resuscitation to restore cardiac filling pressures to baseline levels. The animals were randomly divided into three groups: six served as control, six received DCLHb at a dose of 500 mg/kg (group 1) and six DCLHb at a dose of 1,000 mg/kg (group 2). Cardiac tamponade was then induced by saline injection in the pericardial sac to progressively reduce cardiac index and thereby allow study of tissue oxygen extraction capabilities. DCLHb had a dose-dependent vasopressor effect but did not significantly alter cardiac index or regional blood flow. During cardiac tamponade, critical oxygen delivery was 12.8 +/- 0.7 ml. kg(-1). min(-1) in the control group, but 8.6 +/- 0.9 and 8.2 +/- 0.7 ml. kg(-1). min(-1) in groups 1 and 2, respectively (both P < 0.05 vs. control group). The critical oxygen extraction ratio was 39.1 +/- 3.1% in the control group but 58.7 +/- 12.8% and 60.2 +/- 9.0% in groups 1 and 2, respectively. We conclude that DCLHb can improve whole body oxygen extraction capabilities during endotoxic shock in dogs.

Effect of alpha-alpha diaspirin crosslinked hemoglobin (DCLHb) on the potency of sodium nitroprusside and nitroglycerine to decrease blood pressure in rats: a dose-response study

The nitrovasodilators, sodium nitroprusside and nitroglycerine, effect a dose-dependent decrease in mean arterial blood pressure (MABP) by liberating nitric oxide. Alpha-alpha diaspirin crosslinked hemoglobin (DCLHb) is known to bind nitric oxide. We studied the effect of DCLHb on the potency of sodium nitroprusside (n=36) and nitroglycerine (n=36) to decrease MABP in rats which received 1, 10, 100, 1,000, or 10,000 mg/kg of the DCLHb, or normal saline as the Control. Six doses of sodium nitroprusside or nitroglycerine were given to each rat in a systematically varied sequence. For both drugs, in rats given 1, 10, or 100 mg/kg of DCLHb there were no between groups differences in the change in MABP compared to the Control group. For rats that received 1,000 or 10,000 mg/kg of DCLHb, the potency of nitroglycerine and sodium nitroprusside to decrease MABP was less (p<0.05) than the other groups. These data support the hypothesis that small doses of DCLHb effect a minimal change in the potency of nitrovasodilators to reduce blood pressure. However, they suggest that clinically relevant doses of DCLHb attenuate the vasodilatory ability of sodium nitroprusside and nitroglycerine.

Hemoglobin solutions--not just red blood cell substitutes

OBJECTIVE

To review current knowledge about cell-free hemoglobin solutions.

DATA SOURCES

All studies involving cell-free hemoglobin were retrieved from a computerized MEDLINE search from 1980 to 1998. We also reviewed the reference lists of all available review articles and primary studies to identify references not found in the computerized search.

STUDY SELECTION

Clinical and experimental studies in which cell-free hemoglobin solutions were studied.

DATA EXTRACTION

From the selected studies, information was obtained regarding the experimental model or the study population in which cell-free hemoglobin solutions were investigated, the type of cell-free hemoglobin solution, their deleterious or beneficial effects, and their possible indications.

DATA SYNTHESIS

In many studies, hemoglobin solutions were considered as efficient resuscitative agents and good alternatives to red blood cell transfusion, because of their marked vasopressor effect coupled with their capacity to improve the microcirculation and quickly restore metabolic parameters. Nevertheless, potential problems include an increased susceptibility to infection, immunosuppression, oxidative damage, excessive pulmonary and systemic vasoconstriction, and platelet activation.

CONCLUSIONS

Hemoglobin solutions are more than mere blood substitutes. Promising effects on oxygen transport and the microcirculation need to be confirmed, and the results of continuing research are eagerly awaited.

Diaspirin cross-linked hemoglobin improves mucosal perfusion in the ileum of septic rats

OBJECTIVE

To determine the effect of a bolus infusion of diaspirin cross-linked hemoglobin (DCLHb or hemoglobin crosfumaril) on the ileal mucosal microcirculation in septic rats.

DESIGN

Prospective, randomized, single-blinded study.

SETTING

University-affiliated animal research laboratory.

SUBJECTS

Twenty-four male Sprague-Dawley rats, weighing 320-380 g.

INTERVENTIONS

Under inhalational anesthesia, arterial and venous catheters were inserted and sepsis was created by cecal ligation and perforation (CLP). Twenty-four hours later, animals were reanesthetized and ventilated. Via midline abdominal incision, the ileum was mobilized and prepared for intravital microscopy. Post-CLP hemodynamic values were obtained, and videomicroscopy was performed on four to ten villi. Animals were then randomized to receive 2 mL of DCLHb solution (100 mg/mL; n = 12) or pentastarch (n = 12) intravenously, and measurements were repeated after 20 mins. Rats treated with DCLHb then received nitroprusside to restore mean arterial pressure to post-CLP levels, and final measurements were obtained 15 mins later.

MEASUREMENTS AND MAIN RESULTS

Cardiac index increased with both treatments (p < .001), whereas systemic vascular resistance index and mean arterial blood pressure were augmented only with DCLHb (p < .0001 compared with pentastarch). Intercapillary areas (ICA; inversely related to capillary density) were determined using computerized image analysis. ICA size decreased after treatment, from 974 +/- 79 to 791 +/- 106 microm2 with DCLHb and from 1044 +/- 90 to 840 +/- 82 microm2 with pentastarch (both p < .05). Red blood cell velocity in terminal arterioles, as assessed by velocimetry from the recorded images, increased by 15% with both treatments (p < .05). Restoration of mean arterial pressure to post-CLP levels in DCLHb animals by nitroprusside infusion abolished the effects of the hemoglobin solution on ICA size and red blood cell velocity.

CONCLUSION

Both DCLHb and pentastarch infusion improved microcirculatory perfusion in the ileum of septic rats. In addition, DCLHb also exhibited vasopressor properties, which in combination with improved perfusion may be particularly useful in the treatment of sepsis.

Hemoglobin infusion augments the tumor necrosis factor response to bacterial endotoxin (lipopolysaccharide) in mice

OBJECTIVE

To determine whether cell-free hemoglobin augments the inflammatory cascade, as detected by production of tumor necrosis factor (TNF) elicited by bacterial endotoxin (lipopolysaccharide [LPS]).

DESIGN

In vivo and ex vivo study, using a mouse model of sepsis.

SETTING

Animal research facility

SUBJECTS

Female Swiss Webster mice.

INTERVENTIONS

For the in vivo experiments, an LD50 dose (500 microg) of Escherichia coli LPS was injected intraperitoneally into mice. Cell-free crosslinked hemoglobin (60 mg/mouse) or saline was administered intravenously 10 hrs before or coincident with LPS. For the ex vivo experiments, hemoglobin (60 mg/mouse) or saline was administered intravenously to mice, and, 10 hrs later, hepatic Kupffer cells, peripheral blood mononuclear cells, or peritoneal macrophages were isolated.

MEASUREMENTS AND MAIN RESULTS

Intravenous infusion of hemoglobin either 10 hrs before or coincident with intraperitoneal LPS resulted in a peak of plasma TNF that was greater than in control mice administered LPS only. Cultured Kupffer cells, isolated from mice that had received hemoglobin in vivo 10 hrs before cell collection, produced more TNF in response to LPS in vitro than cells from normal mice. A trend toward greater TNF production in vitro by peripheral blood mononuclear cells obtained from hemoglobin-treated mice also was observed. Enhanced sensitivity to LPS was not observed with cultured peritoneal macrophages from mice that had received hemoglobin.

CONCLUSIONS

Intravenous hemoglobin increased the sensitivity of hepatic macrophages to subsequent stimulation by LPS. This effect may contribute to the increased mortality that we have observed in animals that have received both LPS and hemoglobin.

Influence of sepsis on the plasma elimination pharmacokinetics of diaspirin crosslinked hemoglobin in rats

Septic shock is characterized by abnormalities in microcirculatory O2 delivery (QO2) and profound tissue O2 debt. Administration of crosslinked hemoglobin may be a means of augmenting the QO2 and tissue O2 availability. Sepsis is associated with hemodynamic and metabolic alterations which may affect the pharmacokinetics of crosslinked hemoglobin. The objective of this study was to determine the effect of sepsis on the plasma elimination of diaspirin crosslinked hemoglobin (DCLHb). Twenty-four hours after the induction of sepsis by cecal ligation and perforation, septic (n = 9) and sham rats (n = 8) received an intravenous infusion of 300 mg of DCLHb and arterial blood samples were taken at regular intervals to determine free plasma hemoglobin concentration. DCLHb elimination in septic and sham rats was consistent with first-order elimination kinetics. The half life (t1/2) for septic rats was 4.2 +/- 0.7 h and was significantly shorter than the t1/2 of non-septic rats (5.4 +/- 0.9 h). In all rats, free plasma hemoglobin returned to basal levels by 24 hours after DCLHb administration. The volume of distribution for DCLHb in the septic and non-septic rats was not significantly different and suggests that DCLHb is not influenced by altered gut permeability. Despite significant changes in some elimination parameters the differences were small. Consequently, dosing regimens for this compound may not need to be altered in sepsis.

Diaspirin crosslinked hemoglobin improves systemic oxygen uptake in oxygen supply-dependent septic rats

Diaspirin crosslinked hemoglobin (DCLHb) is a cell-free hemoglobin derived from human erythrocytes. DCLHb has been shown to improve blood flow to vital organs in healthy and septic animals. In this study, we determined the efficacy of DCLHb by comparing its effect on systemic O2 uptake to freshly stored and aged red blood cells (RBCs) in septic rats. Twenty-four hours after induction of sepsis by cecal ligation and perforation, O2 supply dependency was created by isovolemic hemodilution with rat plasma. In O2 supply dependency, rats were randomized to receive an exchange transfusion of 7.5 ml "fresh" RBCs (stored < 6 d; Hct: 70%), "fresh" diluted RBCs (stored < 6 d; Hct: 30%), "old" RBCs (stored 28 to 35 d; Hct: 70%), or DCLHb (Hb: 100 g/L). We found, that survival following O2 supply dependency and transfusion with old RBCs was poor (33% versus 91.7% in the other groups; p < 0.01), precluding further analysis of post-transfusion data from this group. Systemic O2 uptake increased in all remaining groups (p < 0.001), while systemic O2 delivery increased with "fresh" RBCs (p < 0.0001) and "fresh" diluted RBCs (p < 0.05) but not with DCLHb. Systemic O2 extraction increased with DCLHb as compared to baseline (p < 0.05) and to the other groups (p < 0.0001). Improved tissue oxygenation was associated with an increase in blood pressure and a fall in arterial lactate in all groups. We conclude that transfusion of DCLHb or "fresh" RBCs was efficacious at increasing systemic O2 uptake in O2 supply-dependent, septic rats.

Initial evaluation of diaspirin cross-linked hemoglobin (DCLHb) as a vasopressor in critically ill patients

OBJECTIVE

To evaluate the hemodynamic effects and any toxicologic effects of diaspirin cross-linked hemoglobin (DCLHb) in critically ill patients.

DESIGN

A prospective, observational study.

SETTING

A seven-bed intensive care unit (ICU) in a University teaching hospital.

PATIENTS

Fourteen critically ill patients requiring vasopressor therapy to maintain adequate mean arterial pressure (MAP). All patients had secondary organ dysfunction.

INTERVENTIONS

Administration of 100 mL boluses of 10% diaspirin cross-linked hemoglobin, up to a maximum of 500 mL, given over 15 mins and separated by 60 to 90 mins.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic parameters, norepinephrine and inotropic requirements, arterial and mixed venous blood gases, urine output, and biochemical and hematologic analyses were measured before diaspirin cross-linked hemoglobin administration and at multiple time points up to 72 hrs. MAP was maintained at approximately preinfusion values and the reduction in norepinephrine requirements was used as the main end point to assess the efficacy of diaspirin cross-linked hemoglobin as a vasopressor. Diaspirin cross-linked hemoglobin demonstrated a marked vasopressor action, allowing norepinephrine requirements to be reduced from 0.29 +/- 0.15 (SD) microgram/kg/min to 0.15 +/- 0.14 and 0.07 +/- 0.10 microgram/kg/min after the first (at 1.5 hrs, p < .001) and last (at 7.5 hrs, p < .0001) boluses, respectively. These reductions in norepinephrine requirements were maintained at 24, 48, and 72 hrs (p < .01 at all time points). These hemodynamic changes began within 5 mins of starting the diaspirin cross-linked hemoglobin infusion. MAP, heart rate, central venous pressure, pulmonary artery occlusion pressure, mean pulmonary arterial pressure (MPAP), systemic vascular resistance index, and urine output did not demonstrate any significant changes from preinfusion values. Pulmonary vascular resistance index increased at 7.5 hrs despite nonsignificant increases in MPAP. Cardiac index and oxygen delivery index decreased significantly at 7.5 hrs and 24 hrs. Total plasma bilirubin increased significantly from baseline at 24 and 48 hrs, before returning to baseline values within 5 days. Platelet count was significantly reduced at 6 and 24 hrs. No other biochemical or hematologic analyses were altered significantly post diaspirin cross-linked hemoglobin.

CONCLUSIONS

This preliminary study demonstrated that diaspirin cross-linked hemoglobin is a potent vasopressor agent in critically ill patients with septicemic shock or systemic inflammatory response syndrome. This vasopressor characteristic of diaspirin cross-linked hemoglobin may have future clinical applications.

Pulmonary hypertension and systemic vasoconstriction may offset the benefits of acellular hemoglobin blood substitutes

OBJECTIVE

We tested the hypothesis that the pharmacologic properties of a small volume of alpha alpha-cross-linked hemoglobin (alpha alpha Hb) could effectively resuscitate pigs subjected to hemorrhage.

METHODS

Fourteen pigs hemorrhaged to a mean arterial pressure (MAP) of 40 mm Hg for 60 minutes were treated with a 4-mL/kg 2-minute infusion of 10 g/dL alpha alpha Hb or 7 g/dL human serum albumin, an oncotically matched control solution.

RESULTS

The removal of blood (17 +/- 1.5 mL/kg) caused the typical physiologic responses to hemorrhagic hypovolemia. Infusion of alpha alpha Hb restored mean arterial pressure and coronary perfusion pressure, but cardiac output and mixed venous O2 saturation did not improve significantly. Pulmonary arterial pressure and pulmonary vascular resistance increased markedly and were higher than baseline levels after alpha alpha Hb. Infusion of human serum albumin produced only minor hemodynamic changes. Brain blood flow did improve to baseline values after alpha alpha Hb, but was the only tissue to do so. In the human serum albumin group, superior mesenteric artery blood flow recovered to baseline values, whereas brain blood flow did not. Blood flows to other tissues were similar in both groups.

CONCLUSION

Small-volume infusion of alpha alpha Hb restored mean arterial pressure and brain blood flow, but pulmonary hypertension and low peripheral perfusion may offset benefits for trauma patients.

Inhaled nitric oxide reverses cell-free hemoglobin-induced pulmonary hypertension and decreased lung compliance. Preliminary results

BACKGROUND: In order to test the hypothesis that inhaled nitric oxide (NO) reverses the pulmonary hypertension induced by alphaalpha-diaspirin crosslinked hemoglobin (alphaalphaHb), were studied anesthetized pigs that were administered with a total dose of 200 mg/kg of 10% alphaalphaHb. Inhaled NO (5 ppm) was administered for 10 min, and then discontinued for 10 min. This cycle was then repeated with 10 ppm inhaled NO. RESULTS: alphaalphaHb caused pulmonary arterial pressure (PAP) to increase from 27 +/- 1.7 to 40 +/- 3.0 mmHg (P<0.05) and dynamic lung compliance to decrease from 29+/- 1.5 to 23+/- 1.6 ml/cmH2O (P < 0.05). After both doses of inhaled NO, but particularly 10 ppm, PAP was reduced (P < 0.05) and lung compliance increased (P < 0.05) from the alphaalphaHb levels. When inhaled NO was discontinued PAP again increased and lung compliance decreased to levels significantly different from baseline (P < 0.05). CONCLUSION: We conclude that cell-free hemoglobin-induced pulmonary hypertension and decreased lung compliance can be selectively counteracted by inhaled NO.