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In drug development a frequently used phrase is "data‐driven". Just as high‐test gas fuels a car, so drug development "runs on" high‐quality data; hence, good data management practices, which involve case report form design, data entry, data capture, data validation, medical coding, database closure, and database locking, are critically important. This review covers the essentials of clinical data management (CDM) for the United States. It is intended to demystify CDM, which means nothing more esoteric than the collection, organization, maintenance, and analysis of data for clinical trials. The review is written with those who are new to drug development in mind and assumes only a passing familiarity with the terms and concepts that are introduced. However, its relevance may also extend to experienced professionals that feel the need to brush up on the basics. For added color and context, the review includes real‐world examples with RRx‐001, a new molecular entity in phase III and with fast‐track status in head and neck cancer, and AdAPT‐001, an oncolytic adenovirus armed with a transforming growth factor‐beta (TGF‐β) trap in a phase I/II clinical trial with which the authors, as employees of the biopharmaceutical company, EpicentRx, are closely involved. An alphabetized glossary of key terms and acronyms used throughout this review is also included for easy reference. [ABSTRACT FROM AUTHOR]

Summary: The pathophysiologic mechanism of sickle cell disease (SCD) involves polymerization of deoxygenated haemoglobin S (HbS), leading to red blood cell (RBC) sickling, decreased RBC deformability, microvascular obstruction, haemolysis, anaemia and downstream clinical complications. Pharmacological increase in the concentration of oxygenated HbS in RBCs has been shown to be a novel approach to inhibit HbS polymerization and reduce RBC sickling and haemolysis. We report that GBT021601, a small molecule that increases HbS‐oxygen affinity, inhibits HbS polymerization and prevents RBC sickling in blood from patients with SCD. Moreover, in a murine model of SCD (SS mice), GBT021601 reduces RBC sickling, improves RBC deformability, prolongs RBC half‐life and restores haemoglobin levels to the normal range, while improving oxygen delivery and increasing tolerance to severe hypoxia. Notably, oral dosing of GBT021601 in animals results in higher levels of Hb occupancy than voxelotor and suggests the feasibility of once‐daily dosing in humans. In summary, GBT021601 improves RBC health and normalizes haemoglobin in SS mice, suggesting that it may be useful for the treatment of SCD. These data are being used as a foundation for clinical research and development of GBT021601. [ABSTRACT FROM AUTHOR]

Background: Hemolysis releases toxic cell‐free hemoglobin (Hb), heme, and iron, which overwhelm their natural scavenging mechanisms during acute or chronic hemolytic conditions. This study describes a novel strategy to purify a protein cocktail containing a comprehensive set of scavenger proteins for potential treatment of hemolysis byproducts. Study Design and Methods: Tangential flow filtration was used to purify a protein cocktail from Human Cohn Fraction IV (FIV). A series of in vitro assays were performed to characterize composition and biocompatibility. The in vivo potential for hemolysis byproduct mitigation was assessed in a hamster exchange transfusion model using mechanically hemolyzed blood plasma mixed with the protein cocktail or a control colloid (dextran 70 kDa). Results: A basis of 500 g of FIV yielded 62 ± 9 g of a protein mixture at 170 g/L, which bound to approximately 0.6 mM Hb, 1.2 mM heme, and 1.2 mM iron. This protein cocktail was shown to be biocompatible in vitro with red blood cells and platelets and exhibits nonlinear concentration dependence with respect to viscosity and colloidal osmotic pressure. In vivo assessment of the protein cocktail demonstrated higher iron transport to the liver and spleen and less to the kidney and heart with significantly reduced renal and cardiac inflammation markers and lower kidney and hepatic damage compared to a control colloid. Discussion Taken together, this study provides an effective method for large‐scale production of a protein cocktail suitable for comprehensive reduction of hemolysis‐induced toxicity. [ABSTRACT FROM AUTHOR]

Microvascular fluid exchange is primarily dependent on Starling forces and both the active and passive myogenic response of arterioles and post‐capillary venules. Arterioles are classically considered resistance vessels, while venules are considered capacitance vessels with high distensibility and low tonic sympathetic stimulation at rest. However, few studies have investigated the effects of modulating interstitial hydrostatic pressure, particularly in the context of hemorrhagic shock. The objective of this study was to investigate the mechanics of arterioles and functional capillary density (FCD) during application of negative tissue interstitial pressure after 40% total blood volume hemorrhagic shock. In this study, we characterized systemic and microcirculatory hemodynamic parameters, including FCD, in hamsters instrumented with a dorsal window chamber and a custom‐designed negative pressure application device via intravital microscopy. In large arterioles, application of negative pressure after hemorrhagic shock resulted in a 13 ± 11% decrease in flow compared with only a 7 ± 9% decrease in flow after hemorrhagic shock alone after 90 minutes. In post‐capillary venules, however, application of negative pressure after hemorrhagic shock resulted in a 31 ± 4% decrease in flow compared with only an 8 ± 5% decrease in flow after hemorrhagic shock alone after 90 minutes. Normalized FCD was observed to significantly improve after application of negative pressure after hemorrhagic shock (0.66 ± 0.02) compared to hemorrhagic shock without application of negative pressure (0.50 ± 0.04). Our study demonstrates that application of negative pressure acutely improves FCD during hemorrhagic shock, though it does not normalize FCD. These results suggest that by increasing the hydrostatic pressure gradient between the microvasculature and interstitium, microvascular perfusion can be transiently restored in the absence of volume resuscitation. This study has significant clinical implications, particularly in negative pressure wound therapy, and offers an alternative mechanism to improve microvascular perfusion during hypovolemic shock. [ABSTRACT FROM AUTHOR]

Background: Hemoglobin (Hb)‐based oxygen (O2) carriers (HBOCs) are being developed as alternatives to red blood cells and blood when these products are unavailable. Clinical trials of previous HBOC generations revealed side effects, including hypertension and vasoconstriction, that were not observed in preclinical studies. Large molecular weight (MW) polymerized bovine Hb (PolybHb) represents a new class of HBOC with promising results. We evaluated the safety profile of PolybHb after an exchange transfusion (ET) in guinea pigs (GPs). This study compares changes in indices of cardiac, inflammatory, and organ function after ET with high (R‐state) and low (T‐state) O2 affinity PolybHb with high MW. Study Design and Methods: Guinea pigs underwent a 20% ET with PolybHb. To assess the implication of PolybHb ET on the microcirculation, hamsters instrumented with a dorsal window chamber were subjected to a similar volume ET. Results: T and R‐state PolybHb did not induce significant alterations in cardiac function. T‐state PolybHb induced mild vasoconstriction shortly after transfusion, while R‐state did not have acute effects on microvascular tone. Conclusion: Large MW PolybHbs were found to be safe and efficacious in increasing O2 carrying capacity and the O2 affinity of the PolybHb did not affect O2 delivery or extraction by tissues in relevant preclinical models. In conclusion, these results suggest that both T‐state and R‐state PolybHb are safe and do not impair O2 delivery. The results are encouraging and support further evaluation of high MW PolybHbs and their future feasibility compared to allogenic blood in a trauma model. [ABSTRACT FROM AUTHOR]

Abstract: The platelet inhibitory effects of the Phase 3 anticancer agent and nitric oxide (NO) donor, RRx‐001, (1‐bromoacetyl‐3,3‐dinitroazetidine) were examined ex vivo and compared with the diazeniumdiolate NO donor, diethylenetriamine NONOate (DETA‐NONOate), which spontaneously releases nitric oxide in aqueous solution. In the absence of red blood cells and in a dose‐dependent manner, DETA‐NONOate strongly inhibited platelet aggregation induced by several stimuli (ADP, epinephrine and collagen) whereas RRx‐001 only slightly inhibited platelet aggregation under the same conditions in a dose‐dependent manner; these antiaggregant effects were blocked when both DETA‐NONOate and RRx‐001 were co‐incubated with carboxy‐PTIO (CPTIO 0.01‐100 micromol), a widely accepted NO scavenger. However, in the presence of red blood cells from healthy human donors, RRx‐001, which binds covalently to haemoglobin (Hb) and catalyses the production of NO from endogenous nitrite, more strongly inhibited the aggregation of platelets than DETA‐NONOate in a dose‐dependent manner likely because haemoglobin avidly scavenges nitric oxide and reduces its half‐life; the RRx‐001‐mediated platelet inhibitory effect was increased in the presence of nitrite. The results of this study suggest that RRx‐001‐bound Hb (within RBCs) plays an important role in the bioconversion of NO 2 − to NO., which makes RRx‐001 a more physiologically relevant inhibitor of platelet aggregation than other nitric oxide donors, whose effects are attenuated in the presence of red blood cells. Therefore, RRx‐001‐mediated platelet inhibition is a potentially useful therapeutic property, especially in hypercoagulable cancer patients that are at an increased risk of thrombotic complications. [ABSTRACT FROM AUTHOR]

Background: RRx‐001 is an aerospace‐derived, intravenously administered NLRP3‐specific inhibitor with confirmed CNS‐penetrant properties and a favorable safety profile in a Phase 3 clinical trial. It is under investigation as an anticancer agent, a chemoradioprotector for oral mucositis and a prophylactic for acute graft vs. host disease (aGVHD). RRx‐001 has been shown to reduce interleukin‐1β (IL‐1β) production in vivo and to attenuate the severity both of experimental autoimmune encephalomyelitis (EAE), a disease model of multiple sclerosis, and dextran sulfate sodium (DSS)‐induced colitis. Method: In the present study, the neuroprotective effects of 2mg/kg RRx‐001 administration on Alzheimer's Disease (AD), which has been linked to aberrant NLRP3 activation, were evaluated via i.p. injection once weekly for 3 months on aged (21‐24 months old) triple transgenic AD model (3xTg‐AD) mice and control non‐transgenic (NonTg) mice. Result: This sub‐chronic administration of RRx‐001 improved performance on learning and spatial memory tasks and greater risk assessment behavior based on the elevated plus maze test. A significant increase in reduced glutathione and a decrease in lipid peroxidation and amyloid plaque density were also observed in the 3xTg‐AD mice. Conclusion: Together, these findings suggest that RRx‐001 reverses histological hallmarks of AD and protects cognitive and emotional function in aged 3xTg‐AD mice [ABSTRACT FROM AUTHOR]

New Findings What is the central question of this study? The purpose of the present study was to determine the effects of exercise-induced haemoconcentration and hyperthermia on blood viscosity., What is the main finding and its importance? Exercise-induced haemoconcentration, increased plasma viscosity and increased blood aggregation, all of which increased blood viscosity, were counterbalanced by increased red blood cell (RBC) deformability (e.g. RBC membrane shear elastic modulus and elongation index) caused by the hyperthermia. Thus, blood viscosity remained unchanged following prolonged moderate-intensity exercise in the heat., Previous studies have reported that blood viscosity is significantly increased following exercise. However, these studies measured both pre- and postexercise blood viscosity at 37°C even though core and blood temperatures would be expected to have increased during the exercise. Consequently, the effect of exercise-induced hyperthermia on mitigating change in blood viscosity may have been missed. The purpose of this study was to isolate the effects of exercise-induced haemoconcentration and hyperthermia and to determine their combined effects on blood viscosity. Nine subjects performed 2 h of moderate-intensity exercise in the heat (37°C, 40% relative humidity), which resulted in significant increases from pre-exercise values for rectal temperature (from 37.11 ± 0.35 to 38.76 ± 0.13°C), haemoconcentration (haematocrit increased from 43.6 ± 3.6 to 45.6 ± 3.5%) and dehydration (change in body weight = −3.6 ± 0.7%). Exercise-induced haemoconcentration significantly ( P < 0.05) increased blood viscosity by 9% (from 3.97 to 4.33 cP at 300 s−1), whereas exercise-induced hyperthermia significantly decreased blood viscosity by 7% (from 3.97 to 3.69 cP at 300 s−1). When both factors were considered together, there was no overall change in blood viscosity (from 3.97 to 4.03 cP at 300 s−1). The effects of exercise-induced haemoconcentration, increased plasma viscosity and increased red blood cell aggregation, all of which increased blood viscosity, were counterbalanced by increased red blood cell deformability (e.g. red blood cell membrane shear elastic modulus and elongation index) caused by the hyperthermia. Thus, blood viscosity remained unchanged following prolonged moderate-intensity exercise in the heat. [ABSTRACT FROM AUTHOR]

New Findings What is the central question of this study? The aim was to evaluate the effect of perfusion pressure on blood flow in small arterioles. The hypothesis was that blood flow regulates the thickness of the red-cell-free layer and, therefore, blood flow determines blood apparent viscosity and local vascular resistance in vascular networks with limited myogenic or metabolic regulation of blood flow., What is the main finding and its importance? Reduced perfusion pressures lowered volumetric flow rates and increased local vascular resistance, due to increased blood apparent viscosity. Thus, the local vascular resistance of small arterioles with limited myogenic or metabolic regulation of blood flow, appeared to be determined by changes in blood rheology rather than blood vessel diameter., The study of blood flow regulation is important to understand and resolve pathological conditions. As blood is a complex non-Newtonian multiphase system, the foundations of blood rheological properties have been obtained mostly in viscometers. However, blood rheological behaviour in vivo depends on the concentration of red blood cells (RBCs), their mechanical properties and the RBC hydrodynamics, including RBC migration away from the vessel wall in shear flow. This migration promotes the formation of a RBC-depleted zone, or cell-free layer (CFL), which reduces the apparent viscosity of blood. We hypothesize that perfusion pressure determines blood apparent viscosity in microvessels, as shear rate affects axial migration of RBCs by influencing the CFL thickness. In this study, we analysed the effects of perfusion pressure on blood flow in individual arterioles within the rat cremaster muscle preparation. Perfusion pressures to this microvascular bed were controlled by occlusions of the iliac artery using a pressure cuff. Blood flow measurements were obtained from direct measurements of blood flow velocity profile, as well as determination of CFL thickness using intravital microscopy. Our results indicate that perfusion pressure determines shear rates and the CFL thickness and its variations. In addition, blood flow reduction increased local vascular resistance by augmenting blood apparent viscosity rather than vascular hindrance. In conclusion, blood rheology could act as an intrinsic mechanism to further limit blood flow to tissue with limited myogenic and metabolic responses at low perfusion pressures. [ABSTRACT FROM AUTHOR]

R6230 --> 548.13 --> Drag reducing polymers (DRPs) have been used in various engineering applications, such as the transfer of crude oil or seawater in pipelines. The use of DRPs has crossed into the bioengineering sphere, with previous ex‐vivo and in‐vivo studies suggesting that the addition of DRPs decreases the erythrocyte cell free layer (CFL) or cell depleted layer near the vessel wall and increases microvascular blood flow. The objective of this study was to investigate whether the addition of DRPs would improve microvascular perfusion in a rodent model of extracorporeal circulation (ECC). Male Golden Syrian hamsters were instrumented with a dorsal skinfold window chamber, along with an arterial catheter into the right carotid artery to monitor blood pressure and heart rate. During ECC, animals were anesthetized with isoflurane, and a drainage cannula was inserted through the left jugular. The animal was connected to the circuit, primed with either lactate ringers (LR group) or 5 PPM 500 kDa polyethylene glycol in lactate ringers (DRP group). Blood was drained from the jugular cannula, run through a peristaltic pump and bubble trap, before entering the carotid catheter for reinfusion. The circuit was run for 90 minutes in total, with 60 minutes at a flowrate equivalent to 15% of the animal's cardiac output. Measurements were taken before ECC (baseline, BL) and after 1, 2, and 24 hrs post‐ECC. At each timepoint, microvessel (arterioles and venules) diameter, red blood cell velocity and functional capillary density (FCD) were measured using intravital microscopy. Arteriole and venule hemodynamics are displayed in Figure 1. The arteriole results showed an interesting contrast between effects at 1 hr and 24 hrs post‐ECC. At 1 hr post‐ECC, the DRP group displayed a statistically lower arteriole diameter compared to the LR group, but no statistical difference in blood flow between the two groups. At 24 hrs post‐ECC, no difference in arteriole diameter was observed between groups, while arteriole blood flow was statistically higher in the DRP group compared to the LR group. In venules, no changes were observed between groups at 1 hr post‐ECC. However, at 2 and 24 hrs post‐ECC, the DRP group had a statistically significant higher diameter compared to the LR group. Venular blood flow was statistically elevated in the DRP group at 24 hrs post‐ECC compared to the LR group. Figure 2 shows the changes in FCD. FCD was lower for both DRP and LR groups at 1 and 2 hrs post‐ECC when compared to BL levels. The DRP group displayed a higher FCD at 2 hrs post‐ECC compared to the LR group. At 24 hrs however, while the DRP group was able to recover back to BL levels, the LR group was statistically lower than BL. From these results we conclude that the addition of DRPs to priming fluids for ECC procedures may be beneficial in preserving microvascular perfusion 24 hrs post‐ECC. This may help reduce the risk of ischemic injury, production of pro‐inflammatory markers, and development of multiorgan dysfunction. Further research is warranted to optimize the DRPs parameters, such as concentration and molecular weight. [ABSTRACT FROM AUTHOR]

Background Human red blood cells ( RBCs) can be stored for up to 42 days under controlled conditions. Physical and chemical changes occur during RBC storage, altering their function. This study links stored cell mechanical changes with hemodynamic functional alterations upon transfusion. Study Design and Methods Mechanical properties of fresh and stored RBCs were evaluated in vitro. Their transfusion effects were evaluated in vivo using intravital microscopy of the rat's cremaster muscle preparation. Rats were hemodiluted to 30% hematocrit, to mimic an anemic state before transfusion, and then exchange-transfused with fresh or stored cells. Results In vitro studies on rheology and oxygen affinity of stored cells confirmed previously published results. Storage was found to modify static and dynamic RBC mechanic behavior. After transfusion, systemic hemodynamics were similar for fresh and stored cells; however, microvascular hemodynamics were drastically affected by stored cells. Stored cells reduced blood flow and oxygen delivery. Additionally, the presence of stored cells in circulation affected cell-to-cell and cell-to-wall interactions and affected cell hydrodynamics. Stored cells disrupted the RBC cell-free layer and wall shear stress signals. Conclusion The reduced cell deformability due to RBC 'storage lesions' caused pathologic changes in microvascular hemodynamics, endothelial cell mechanotransduction, and RBC dynamics. Thus, the mechanical changes of blood-banked cells can limit transfusion ability to achieve its intended goal. [ABSTRACT FROM AUTHOR]

Perfluorocarbon (PFC) emulsions can transport and release various gases based on concentration gradients. The objective of this study was to determine the possibility of carrying and delivering exogenous nitric oxide (NO) into the circulation by simply loading PFC emulsion with NO prior infusion. PFC was equilibrated with room air (PFC) or 300 ppm NO (PFC-NO) at atmospheric pressure. Isotonic saline solution was used as a volume control (Saline). PFC and PFC-NO were infused at a dose of 3.5 mL/kg in the hamster window chamber model. Blood chemistry, and systemic and microvascular hemodynamic response were measured. Infusion of PFC preloaded with NO reduced blood pressure, induced microvascular vasodilation and increased capillary perfusion; although these changes lasted less than 30 min post infusion. On the other hand, infusion of PFC (without NO) produced vasoconstriction; however, the vasoconstriction was followed by vasodilatation at 30 min post infusion. Plasma nitrite and nitrate increased 15 min after infusion of NO preloaded PFC compared with PFC, 60 min after infusion nitrite and nitrate were not different, and 90 min after infusion plasma S-nitrosothiols increased in both groups. Infusion of NO preloaded PFC resulted in acute vascular relaxation, where as infusion of PFC (without NO) produced vasoconstriction, potentially due to NO sequestration by the PFC micelles. The late effects of PFC infusion are due to NO redistribution and plasma S-nitrosothiols. Gas solubility in PFC can provide a tool to modulate plasma vasoactive NO forms availability and improve microcirculatory function and promote increased blood flow. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1565-1572, 2013 [ABSTRACT FROM AUTHOR]

Perfluorocarbon (PFC) emulsions used as artificial oxygen carriers lack colloid osmotic pressure (COP) and must be administered with colloid-based plasma expanders (PEs). Although PFC emulsions have been widely studied, there is limited information about PFC emulsion interaction with PEs and blood. Their interaction forms aggregates due to electrostatic and rheological phenomena, and change blood rheology and blood flow. This study analyzes the effects of the interaction between PFC emulsions with blood in the presence of clinically-used PEs. The rheological behavior of the mixtures was analyzed in vitro in parallel with in vivo analysis of blood flow in the microcirculation using intravital microscopy, when PEs were administered in a clinically relevant scenario. The interaction between the PFC emulsion and PE with blood produced PFC droplets and red blood cell (RBCs) aggregation and increased blood viscosity in a shear dependent fashion. The PFC droplets formed aggregates when mixed with PEs containing electrolytes, and the aggregation increased with the electrolyte concentration. Mixtures of PFC with PEs that produced PFC aggregates also induced RCBs aggregation when mixed with blood, increasing blood viscosity at low shear rates. The more viscous suspension at low shear rates produced a blunted blood flow velocity profile in vivo compared to nonaggregating mixtures of PFC and PEs. For the PEs evaluated, human serum albumin produced minimal to undetectable aggregation. PFC and PEs interaction with blood can affect sections of the microcirculation with low shear rates (e.g., arterioles, venules, and pulmonary circulation) when used in a clinical setting, because persistent aggregates could cause capillary occlusion, decreased perfusion, pulmonary emboli or focal ischemia. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:796-807, 2013 [ABSTRACT FROM AUTHOR]

BACKGROUND: Treating hemorrhage with blood transfusions in subjects previously hemodiluted with different colloidal plasma expanders, using fresh autologous blood or blood that has been stored for 2 weeks, allows identifying the interaction between type of plasma expander and differences in blood storage. STUDY DESIGN AND METHODS: Studies used the hamster window chamber model. Fresh autologous plasma, 130-kDa starch-based plasma expander (hydroxyethyl starch [HES]), or 4% polyethylene glycol-conjugated albumin (PEG-Alb) was used for 20% of blood volume (BV) hemodilution. Hemodilution was followed by a 55% by BV 40-minute hemorrhagic shock period, treated with transfusion of fresh or blood that was stored for 2 weeks. Outcome was evaluated 1 hour after blood transfusion in terms of microvascular and systemic variables. RESULTS: Results were principally dependent on the type of colloidal solution used during hemodilution, 4% PEG-Alb yielding the best microvascular recovery evaluated in terms of the functional capillary density. This result was consistent whether fresh blood or stored blood was used in treating the subsequent shock period. Fresh blood results were significantly better in systemic and microvascular terms relative to stored blood. HES and fresh plasma hemodilution yielded less favorable results, a difference that was enhanced when fresh versus stored blood was compared in their efficacy of correcting the subsequent hemorrhage. CONCLUSION: The type of plasma expander used for hemodilution influences the short-term outcome of subsequent volume resuscitation using blood transfusion, 4% PEG-Alb providing the most favorable outcome by comparison to HES or fresh plasma. [ABSTRACT FROM AUTHOR]

BACKGROUND: The hemoglobin of the earthworm Lumbricus terrestris (also known as erythrocruorin, or LtEc) is a naturally occurring high-molecular-weight protein assembly (3.6 MDa) that is extremely stable, resistant to oxidation, and transports oxygen similarly to human whole blood. Therefore, LtEc may serve as an alternative to donated human red blood cells. However, a suitable purification process must be developed to produce highly pure LtEc on a large scale that can be evaluated in an animal model to determine the safety and efficacy of LtEc. STUDY DESIGN AND METHODS: We used tangential-flow filtration (TFF), an easily scalable and affordable technique, to produce highly pure LtEc from earthworms. The purity, yield, methemoglobin level, viscosity, colloid osmotic pressure, O2 binding equilibria, and ligand-binding kinetics of the purified LtEc were measured in vitro. The purified LtEc product was then evaluated in hamsters using a hypervolemic infusion model to establish its basic biocompatibility and detect any changes in microcirculatory and systemic variables. RESULTS: TFF was able to produce LtEc with high purity and yield (5-10 g/1000 worms). The purified LtEc product did not elicit hypertension or vasoconstriction when infused into hamsters. CONCLUSION: LtEc may be easily purified and safely transfused into hamsters in small amounts (0.5-1.5 g/dL final concentration in blood) without any noticeable side effects. Therefore, LtEc may serve as a very promising oxygen carrier for use in transfusion medicine. [ABSTRACT FROM AUTHOR]

In a recent study, ultrahigh molecular weight (M w) glutaraldehyde-polymerized bovine hemoglobins (PolybHbs) were synthesized with low O2 affinity and exhibited no vasoactivity and a slight degree of hypertension in a 10% top-load model.1 In this work, we systematically investigated the effect of varying the glutaraldehyde to hemoglobin (G:Hb) molar ratio on the biophysical properties of PolybHb polymerized in either the low or high O2 affinity state. Our results showed that the M w of the resulting PolybHbs increased with increasing G:Hb molar ratio. For low O2 affinity PolybHbs, increasing the G:Hb molar ratio reduced the O2 affinity and CO association rate constants in comparison to bovine hemoglobin (bHb). In contrast for high O2 affinity PolybHbs, increasing the G:Hb molar ratio led to increased O2 affinity and significantly increased the CO association rate constants compared to unmodified bHb and low O2 affinity PolybHbs. The methemoglobin level and NO dioxygenation rate constants were insensitive to the G:Hb molar ratio. However, all PolybHbs displayed higher viscosities compared to unmodified bHb and whole blood, which also increased with increasing G:Hb molar ratio. In contrast, the colloid osmotic pressure of PolybHbs decreased with increasing G:Hb molar ratio. To preliminarily evaluate the ability of low and high O2 affinity PolybHbs to potentially oxygenate tissues in vivo, an O2 transport model was used to simulate O2 transport in a hepatic hollow fiber (HF) bioreactor. It was observed that low O2 affinity PolybHbs oxygenated the bioreactor better than high O2 affinity PolybHbs. This result points to the suitability of low O2 affinity PolybHbs for use in tissue engineering and transfusion medicine. Taken together, our results show the quantitative effect of varying the oxygen saturation of bHb and G:Hb molar ratio on the biophysical properties of PolybHbs and their ability to oxygenate a hepatic HF bioreactor. We suggest that the information gained from this study can be used to guide the design of the next generation of hemoglobin-based oxygen carriers (HBOCs) for use in tissue engineering and transfusion medicine applications. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011 [ABSTRACT FROM AUTHOR]

The use of many plasma expanders (PEs) is often limited by undesirable side effects, such as red blood cell (RBC) aggregation (hydroxyethyl starch), nephrotoxicity (dextran), and extravasation (albumin). Despite its natural prevalence in the bloodstream, human serum albumin (HSA) can increase the risk of mortality when administered to patients with increased vascular permeability (i.e., patients suffering from burns, septic shock, and endothelial dysfunction). The harmful extravasation of HSA can be limited by polymerizing HSA to increase its molecular size. In this study, HSA was nonspecifically cross-linked with glutaraldehyde at different cross-link densities by varying the molar ratio of glutaraldehyde to HSA. The results of this study show that the weight-averaged molecular weight (MW), viscosity, and extent of RBC aggregation of polymerized HSA increases with increasing cross-link density, whereas the colloid osmotic pressure (COP) decreases with increasing cross-link density. Interestingly, circular dichroism measurements indicate that the secondary structure of HSA is unaffected by polymerization. Altogether, these results show that glutaraldehyde can effectively cross-link HSA to produce high MW polymers, yielding a novel series of potential PEs that exhibit low COP and high viscosity. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011 [ABSTRACT FROM AUTHOR]

BACKGROUND: Hemoglobin (Hb) solutions are potential alternatives to blood transfusion when native oxygen (O2)-carrying capacity is lacking. Polymerized bovine Hb (PBH) solutions are characterized by its vasoactivity, low O2 affinity, oncotic effect, prolonged shelf life, and stability. Responses to facilitated O2 transport, after exchange transfusion with PBH, were studied in the hamster window chamber model during acute extreme anemia to determine how PBH affects microvascular perfusion and tissue oxygenation. STUDY DESIGN AND METHODS: An anemic state was induced by hemodilution with a plasma expander (70-kDa dextran). After hemodilution, animals were randomly assigned to exchange transfusion groups based on the concentration of PBH used, namely, PBH at 13 gHb per dL (PBH13), PBH diluted to 8 or 4 gHb per dL in albumin solution at matching colloidal osmotic pressure (COP; PBH8 and PBH4), and no PBH only albumin solution at matching COP (PBH0). Measurement of systemic variables, microvascular hemodynamics, capillary perfusion, and intravascular and tissue O2 levels was performed at 11 percent Hct. RESULTS: Restitution of O2-carrying capacity with PBH13 restored higher arterial pressure and triggered vasoconstriction, low perfusion, and higher peripheral resistance. Groups PBH4 and PBH0 had lower arterial pressures than Group PBH13. Groups PBH4 and PBH8 maintained higher perfusion and functional capillary density than Groups PBH13 and PBH0. In all groups, blood gas variables and acid-base balance were recovered proportional to microvascular perfusion. Arterial O2 tensions were improved for Groups PBH4 and PBH8 by preventing O2 precapillary release and increasing O2 reserve. CONCLUSION: Further studies to establish acellular Hb optimal dosage, efficacy, safety, and effects on outcome are indicated before these solutions are implemented in routine practice. [ABSTRACT FROM AUTHOR]

Perfluorocarbons (PFCs) developed for the intravascular transport of oxygen have a higher solubility for gases compared to plasma and therefore can be used to transport and deliver a variety of bioactive gases for therapeutic purposes. Intravenous infusion of PFCs preequilibrated with carbon monoxide gas may provide a means to produce vasodilatation. A similar effect can be obtained by preloading PFC emulsions with nitric oxide (NO), as well as introducing unsaturated PFC emulsions in the circulation, since these can scavenge and redistribute NO. Volatile anesthetics delivered in conjunction with the intravenous presence of PFCs are more effective at lower dosages, and provide for a more uniform anesthetic effect in terms of duration of anesthesia. PFC emulsions are therefore proposed as vehicles for the transport and delivery of gases to the tissues, offering high accuracy of dosage, and avoiding uncertainties of gas delivery associated with gas inspiration via the lungs. [ABSTRACT FROM AUTHOR]

Potential shortages and perceived issues with the biosafety of blood have strengthened interest in the search for alternatives to blood. Currently available plasma expanders are effective in recovering pressure by volume expansion but are not safely deployed beyond the transfusion trigger. Conventional reasoning indicates that this limitation relates to oxygen carrying capacity reaching the threshold where it no longer can satisfy the metabolic demand of the organism; however, recent findings show that this limitation is also determined by other physical factors such as their viscosity and colloidal osmotic pressure. These fluid transport properties have a strong influence on the maintenance of microvascular perfusion and function in conditions of extreme hemodilution that obtain when resuscitation is continued beyond the transfusion trigger with plasma expanders. This realization leads to the possibility of developing new plasma expanders whose physical properties enhance microvascular function compensating for the decreased intrinsic oxygen carrying capacity in extreme hemodilution via enhanced microvascular perfusion. This review presents experimental, systemic and microvascular findings obtained using polyethylene glycol conjugated albumin solutions in extreme hemodilution and shock resuscitation in the hamster window chamber model, concluding that plasma expanders of this type can be effectively used beyond the transfusion trigger. [ABSTRACT FROM AUTHOR]

Despite the advances in blood substitutes, the development of materials that are effective in maintaining blood volume and oxygen delivery remains the priority for emergency care and trauma. Vasoactivity, i.e. vasoconstriction, presumably caused by nitric oxide (NO) scavenging has been defined as the principal problem associated with acellular hemoglobin (Hb) with low hydrodynamic radius. Conversely, Hb-based materials with very large hydrodynamic radius, achieved by surface decoration of the Hb tetramer with water-trapping polymers such as polyethylene glycol (PEG) conjugation, have been found vasoinactive in spite of being effective NO scavengers. This article explores possible mechanisms for why PEGylated Hbs not only are not vasoconstrictive but also are actually facilitators for maintaining high perfusion levels in the microcirculation. The most promising mechanisms are based on relatively recent observations and models; they indicate that Hb can actively regulate availability of ‘bioactive’ NO forms. This regulation can occur via: (i) NO transport by Hb in an allosterically controlled reversible chemical reaction with the Cys beta 93 (S-NO-Hb); and (ii) production of bioactive forms of NO through nitrite reductase activity of deoxyHb. The principal issues associated with these proposed mechanisms are: (i) how these reactions generate bio-available NO and (ii) how the generated NO is delivered to the site of action without being either degraded or sequestered. We present a promising hypothesis and preliminary supporting data that PEGylated Hbs through a nitrite-mediated reaction are especially effective in generating nitrosothiols, creating a transportable source of bioactive NO. [ABSTRACT FROM AUTHOR]

Objective: Acclimatization to reduced environmental oxygen includes erythropoietin-regulated increase in erythrocytes enhancing the blood's oxygen content. However, increased hematocrit levels result in elevated blood viscosity that might impair microcirculation and tissue oxygenation. To assess this oxygen supply to the skin, the authors used erythropoietin overexpressing transgenic mice (tg6) that develop excessive erythrocytosis in an oxygen-independent manner. These animals have been previously reported to elevate their blood viscosity 4-fold. Methods: The partial oxygen pressure (pO2) distribution was evaluated in microvessels as well as in subcutaneous interstitial tissue within a dorsal skinfold chamber of resting conscious mice using automated phosphorescence quenching. Results: Compared to wildtype (wt) animals, transgenic blood viscosity increased 4-fold but microvessel diameter was not altered. Despite sharing similar blood pO2 as the wt siblings, tg6 animals nearly doubled their oxygen content. Moreover, tg6 erythrocytes reduced hemoglobin's oxygen affinity by decreased 2,3-DPG levels and an increased Hill number. Transgenic arterioles and venules showed increased pO2 compared to wt controls whereas capillary and tissue pO2 were not altered. Conclusions: Excessive erythrocytosis does not elevate capillary oxygen delivery. [ABSTRACT FROM AUTHOR]

Background: Transfusions are intended to augment oxygen-carrying capacity. The ability of fresh and stored red blood cells (RBCs) to maintain microvascular perfusion and oxygen delivery to the tissue has not been directly measured.Study Design and Methods: Microvascular responses to exchange transfusion with fresh and stored RBCs after acute isovolemic hemodilution with a plasma expander were investigated with the hamster window chamber model. In-vivo functional capillary density (FCD), blood flow, and high-resolution oxygen distribution in microvascular networks were measured by noninvasive methods.Results: Exchange transfusion with an RBC suspension after a 60 percent isovolemic hemodilution with dextran 70 (6% MW = 70 kDa) resulted in a hematocrit of 18 percent (5.6 +/- 0.2 g/dL hemoglobin [Hb]). All other systemic variables were unchanged. Stored RBCs (28 days in citrate-phosphate-dextrose-adenine-1) resuspended in fresh frozen plasma matched to the Hct and Hb concentration were exchange transfused until 25 percent of the circulating RBCs were stored RBCs. Stored RBCs reduced microvascular flow and FCD by 63 and 54 percent, respectively, of the level achieved when fresh RBCs were exchange transfused. Microvascular oxygen extraction by the stored RBC was 54 percent lower than that of the fresh RBCs. The tissue oxygen levels were 3.5 and 14.4 mmHg for the stored and fresh RBCs, respectively.Conclusion: Circulation of stored RBCs in a hemodiluted animal resulted in significantly malperfused and underoxygenated microvasculature that was not detectable at the systemic level. [ABSTRACT FROM AUTHOR]

Human serum albumin (HSA) is currently used as a plasma expander (PE) to increase blood volume during hypovolemic conditions, such as blood loss. However, its effectiveness is suboptimal in septic shock and burn patients due to their enhanced endothelial permeability, resulting in HSA extravasation into the tissue space leading to edema, and deposition of toxic HSA-bound metabolites. Hence, to expand HSA's applicability toward treating patients with compromised endothelial permeability, HSA has been previously polymerized to increase its molecular size thus compartmentalizing the polymerized HSA (PolyHSA) molecules in the vascular space. Previous studies bracketed PolyHSA between 100 kDa and 0.2 μm. In this research, PolyHSA was synthesized at two cross-link densities 43:1 and 60:1 (i.e., molar ratios of glutaraldehyde to HSA) and subsequently fractionated via tangential flow filtration (TFF) into two narrower brackets: bracket A (500 kDa and 0.2 μm) and bracket B (50-500 kDa). PolyHSA within the same size bracket at different cross-link densities exhibited similar solution viscosity, zeta potential, and osmolality but differed in hydrodynamic diameter. At the same cross-link density, the PolyHSA A bracket showed higher viscosity, lowered zeta potential, and a larger hydrodynamic diameter compared with the PolyHSA B bracket while maintaining osmolality. Interestingly, PolyHSA 43:1 B, PolyHSA 60:1 A, and PolyHSA 60:1 B brackets exhibited colloid osmotic pressure similar to HSA, indicating their potential to serve as PEs., (© 2024 The Author(s). Biotechnology Progress published by Wiley Periodicals LLC on behalf of American Institute of Chemical Engineers.)