Biocompatibility of the oxygen carrier polymerized human hemoglobin towards HepG2/C3A cells

Hemoglobin (Hb) based oxygen carriers (HBOCs) are designed to minimize the toxicity of extracellular Hb, while preserving its high oxygen-carrying capacity for oxygen delivery to cells. Polymerized human Hb (PolyHb) is a novel type of nanosized HBOC synthesized via glutaraldehyde-mediated crosslinking of free Hb, and which preserves the predominant quaternary state during the crosslinking reaction (low oxygen affinity tense (T) quaternary state PolyHb is synthesized at 0% Hb oxygen saturation, and high oxygen affinity relaxed (R) quaternary state PolyHb is synthesized at 100% Hb oxygen saturation). Major potential applications for PolyHbs, and HBOCs in general, include oxygenation of bioreactor systems containing large liver cell masses, and ex-vivo perfusion preservation of explanted liver grafts. The toxicity of these compounds toward liver cells must be evaluated before testing their use in these complex systems for oxygen delivery. Herein, we characterized the effect of PolyHbs on the hepatoma cell line HepG2/C3A, used as a model hepatocyte and as a cell line used in some investigational bioartificial liver support devices. HepG2/C3A cells were incubated in cell culture media containing PolyHbs or unmodified Hb at concentrations up to 50 mg/mL and for up to 6 days. PolyHbs were well tolerated at a dose of 10 mg/mL, with no significant decrease in cell viability; however, proliferation was inhibited as much as 10-fold after 6 days of exposure at 50 mg/mL. Secretion of albumin, and urea, as well as glucose and ammonia removal were measured in presence of 10 mg/mL of PolyHbs or unmodified Hb. In addition, methoxy- and ethoxy-resorufin deacetylase (MROD and EROD) activities, which reflect cytochrome P450 metabolism, were measured. R-state PolyHb displayed improved or intact activity in 3 out of 7 functions compared to unmodified Hb. T-state PolyHb displayed improved or intact activity in 4 out of 7 functions compared to unmodified Hb. Thus, PolyHbs, both in the R-state and T-state, are safer to use at a concentration of 10 mg/mL as compared to unmodified Hb in static culture liver-related applications.

Issues in the development of hemoglobin based oxygen carriers

Hemoglobin based oxygen carriers (HBOCs) have been developed as alternative oxygen transporting formulations for the acute treatment of anemia and ischemia. Efficacy has been demonstrated in a variety of preclinical models and selected human patients; however, a higher overall incidence of mortality and myocardial infarction in those dosed with HBOCs in later stage clinical trials has prevented widespread regulatory approval. Diagnosis of myocardial infarction is confounded by the fact that HBOCs interfere with troponin assays, as well as other clinical chemistry measurements. Analysis of data pertaining to potential toxicity mechanisms suggests that coronary vasoconstriction is an unlikely contributor, but promotion of intravascular thrombosis may occur by several mechanisms. In addition, fluid and anemia management in patients infused with HBOCs has been suboptimal. Elucidation of potential toxicity mechanisms, refinement of use protocols, and definition of improved patient inclusion/exclusion criteria remain active areas of inquiry in understanding the best manner in which to utilize HBOCs.

Haemoglobin-based oxygen carriers and myocardial infarction

The incidence of investigator diagnosed myocardial infarction (MI) is greater in patients treated with haemoglobin-based oxygen carriers (HBOCs) than controls. Clinical trials and literature pertaining to possible HBOC toxicity mechanisms have been analyzed in order to identify possible reasons for this imbalance. MI diagnosis is hampered by potential interference of troponin assays by haemoglobin, haemolysis and bilirubin. Nevertheless, insofar as the reported incidence correlates with actual occurrence, there is a positive relationship between MI and HBOC dose and size. Preclinical and clinical data suggest that direct cardiac toxicity and coronary vasoconstriction are unlikely. More probable are detrimental intravascular interactions between HBOCs and components of the coagulation cascade, particularly dysfunctional endothelium. Elucidation of mechanisms is impeded by a lack of clinical data. Measurement of relevant biomarkers would be extremely useful in this regard and in improving patient selection criteria. Conduct of clinical trials in carefully selected patient populations after the development of improved protocols for MI diagnosis, along with concomitant biomarker data collection, is recommended.

Analytical interference of HBOC-201 (Hemopure, a synthetic hemoglobin-based oxygen carrier) on four common clinical chemistry platforms

BACKGROUND

There are 13 million blood transfusions each year in the US. Limitations in the donor pool, storage capabilities, mass casualties, access in remote locations and reactivity of donors all limit the availability of transfusable blood products to patients. HBOC-201 (Hemopure®) is a second-generation glutaraldehyde-polymer of bovine hemoglobin, which can serve as an "oxygen bridge" to maintain oxygen carrying capacity while transfusion products are unavailable. Hemopure presents the advantages of extended shelf life, ambient storage, and limited reactive potential, but its extracellular location can also cause significant interference in modern laboratory analyzers similar to severe hemolysis.

METHODS

Observed error in 26 commonly measured analytes was determined on 4 different analytical platforms in plasma from a patient therapeutically transfused Hemopure as well as donor blood spiked with Hemopure at a level equivalent to the therapeutic loading dose (10% v/v).

RESULTS

Significant negative error ratios >50% of the total allowable error (>0.5tAE) were reported in 23/104 assays (22.1%), positive bias of >0.5tAE in 26/104 assays (25.0%), and acceptable bias between -0.5tAE and 0.5tAE error ratio was reported in 44/104 (42.3%). Analysis failed in the presence of Hemopure in 11/104 (10.6%). Observed error is further subdivided by platform, wavelength, dilution and reaction method.

CONCLUSION

Administration of Hemopure (or other hemoglobin-based oxygen carriers) presents a challenge to laboratorians tasked with analyzing patient specimens. We provide laboratorians with a reference to evaluate patient samples, select optimal analytical platforms for specific analytes, and predict possible bias beyond the 4 analytical platforms included in this study.

Ultrasound Triggered Tumor Oxygenation with Oxygen-Shuttle Nanoperfluorocarbon to Overcome Hypoxia-Associated Resistance in Cancer Therapies

Tumor hypoxia is known to be one of critical reasons that limit the efficacy of cancer therapies, particularly photodynamic therapy (PDT) and radiotherapy (RT) in which oxygen is needed in the process of cancer cell destruction. Herein, taking advantages of the great biocompatibility and high oxygen dissolving ability of perfluorocarbon (PFC), we develop an innovative strategy to modulate the tumor hypoxic microenvironment using nano-PFC as an oxygen shuttle for ultrasound triggered tumor-specific delivery of oxygen. In our experiment, nanodroplets of PFC stabilized by albumin are intravenously injected into tumor-bearing mice under hyperoxic breathing. With a low-power clinically adapted ultrasound transducer applied on their tumor, PFC nanodroplets that adsorb oxygen in the lung would rapidly release oxygen in the tumor under ultrasound stimulation, and then circulate back into the lung for reoxygenation. Such repeated cycles would result in dramatically enhanced tumor oxygenation and thus remarkably improved therapeutic outcomes in both PDT and RT treatment of tumors. Importantly, our strategy may be applied for different types of tumor models. Hence, this work presents a simple strategy to promote tumor oxygenation with great efficiency using agents and instruments readily available in the clinic, so as to overcome the hypoxia-associated resistance in cancer treatment.

Blood doping: risks to athletes' health and strategies for detection

Blood doping has been defined as the misuse of substances or certain techniques to optimize oxygen delivery to muscles with the aim to increase performance in sports activities. It includes blood transfusion, administration of erythropoiesis-stimulating agents or blood substitutes, and gene manipulations. The main reasons for the widespread use of blood doping include: its availability for athletes (erythropoiesis-stimulating agents and blood transfusions), its efficiency in improving performance, and its difficult detection. This article reviews and discusses the blood doping substances and methods used for in sports, the adverse effects related to this practice, and current strategies for its detection.

Oxygen therapeutics: perfluorocarbons and blood substitute safety

Current demands over the blood supply in developed and developing nations will compound over time. Red cell substitutes have a promising value proposition for transfusion services, because they hold the promise of increasing the availability of blood products and removing donor and contamination safety risks. In this article, the authors note that existing products suffer from critical shortcomings such as vasoactivity; they also point out that substitutes not based on human blood introduce potentially more complex safety hurdles. The authors discuss the attributes of an ideal blood substitute, and the mechanism and current status of perfluorocarbons; they also review the shortcomings of all oxygen therapeutic products in development today.

Interference in clinical chemistry assays by the hemoglobin-based oxygen carrier, Hemospan

OBJECTIVE

To evaluate interference by the hemoglobin-based oxygen carrier Hemospan on clinical laboratory assays.

DESIGN AND METHODS

Interfering Hemospan concentrations were determined for general chemistry and cardiac marker analytes in pooled serum and the corresponding hemolysis index was calculated.

RESULTS

Hemospan did not interfere with 20 of 35 analytes. Hemospan produced a negative interference in serum creatinine, amylase, alkaline phosphatase, uric acid, and GGT assays and a positive interference in serum phosphate, LDH, iron, triglycerides, total protein, AST, cholesterol, magnesium, and albumin assays, and appeared to positively bias the serum cardiac troponin I (cTnI) assay only when cTnI is present in the sample.

CONCLUSIONS

We present a report of assays affected by Hemospan and the threshold concentrations for interference. This study highlights the importance of interference studies in understanding the effects of hemoglobin-based oxygen carriers on results reported by the clinical laboratory.

Anaesthetic issues related to postpartum haemorrhage (excluding antishock garments)

The obstetric anaesthetist is a key member of the multidisciplinary team required to manage postpartum haemorrhage, having been trained in resuscitation and being experienced in managing haemorrhage and in monitoring and caring for the critically ill patient. The diagnosis of shock, initial resuscitation controversies surrounding fluid replacement, cell salvage in obstetrics and monitoring are discussed.

Oxygen therapeutics: pursuit of an alternative to the donor red blood cell

CONTEXT

There is no true substitute for the many functions of human red blood cells, and synthetic products will not replace the need for blood donation in the foreseeable future. Hemoglobin-based oxygen carriers have many characteristics that would serve as a useful adjunct to red cells in clinical settings. Over time, these technologies have the potential to dramatically reshape the practice of transfusion medicine.

OBJECTIVE

To review the characteristics and potential utility of hemoglobin-based oxygen carriers and perfluorocarbon-based oxygen carriers. Several hemoglobin-based oxygen carriers are under study in phase III clinical trials. Novel uses for synthetic oxygen therapeutics are emphasized.

DATA SOURCES

All published reports with the key words oxygen therapeutics, blood substitutes, and red cell substitutes from 1933 until March 2006 were searched through Medline. Significant findings were synthesized.

CONCLUSIONS

Recognition of the true impact of red cell substitutes is still several years away. The most compelling products, hemoglobin-based oxygen carriers, have potential use in trauma, providing immediate oxygen-carrying support in the face of alloantibodies or autoantibodies, and in other clinical situations in which long-term survival of red cells is not essential. In the interim, efforts should be focused on enhancing the current blood supply system while supporting ongoing and planned blood substitute research efforts, including trials assessing novel clinical indications for these products.

Biochemistry, physiology, and complications of blood doping: facts and speculation

Competition is a natural part of human nature. Techniques and substances employed to enhance athletic performance and to achieve unfair success in sport have a long history, and there has been little knowledge or acceptance of potential harmful effects. Among doping practices, blood doping has become an integral part of endurance sport disciplines over the past decade. The definition of blood doping includes methods or substances administered for non-medical reasons to healthy athletes for improving aerobic performance. It includes all means aimed at producing an increased or more efficient mechanism of oxygen transport and delivery to peripheral tissues and muscles. The aim of this review is to discuss the biochemistry, physiology, and complications of blood doping and to provide an update on current antidoping policies.

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.

Perioperative blood transfusion and outcome

PURPOSE OF REVIEW

As a result of advances in pathogen testing and transfusion standards over the last decade, the risk of disease transmission through allogeneic blood transfusions has decreased markedly. The effects of allogeneic blood transfusions on the immune system, however, have received more attention, as they appear to influence outcome. The following review summarizes the effects of allogeneic blood transfusions on selected outcome parameters and the influence of white blood cell reduction on these parameters.

RECENT FINDINGS

Adverse effects of allogeneic blood transfusions on outcome variables such as postoperative infection, cancer recurrence, pulmonary function, length of stay, and mortality have been shown in multiple trials, but most were not randomized or blinded. One proposed approach to reduce unwanted side-effects is to reduce the donor's white blood cell count before transfusion. This can be done either by individual bedside filtration or by pre-storage (or post-storage) universal white blood cell reduction. Studies investigating this approach have yielded conflicting results.

SUMMARY

Although the results of a number of studies suggest a negative impact of allogeneic blood transfusions on immune function and consequently outcome parameters, this has not been proven in rigorously controlled randomized trial, or in meta-analyses. Reduction of white blood cells might be beneficial in selected patient populations, but at this time does not appear warranted in the general surgical population. As universal white blood cell reduction is a very costly process, it probably should not be implemented until such a benefit is proven.

Rationale for blood conservation

BACKGROUND

Exposure of patients to allogeneic blood transfusion can be minimized or avoided by the systematic use of multiple blood conservation techniques. Current use of these technologies is variable.

METHODS

Review of pertinent English language literature.

RESULTS

Enthusiasm for preoperative autologous blood donation (PAD) has declined considerably, perhaps due to increased cost and inconvenience to patients. Acute normovolemic hemodilution (ANH) has several practical advantages over PAD, but has not become generally accepted as a blood conservation strategy. Erythropoietin, iron, and artificial oxygen carriers are pharmacologic alternatives.

CONCLUSIONS

Pharmacologic stimulation of erythropoiesis offers substantial potential to progress toward a goal of bloodless medicine. The potential of artificial blood substitutes is still being defined.

Current Status of Artificial o2 Carriers

This article describes currently evaluated artificial O2 carriers, summarizes their efficacy, and discusses their side effects, based on and restricted to published data. For compounds in phase III testing, approximately 500 to 1000 patients have been dosed, and similar numbers of control patients have been investigated. For compounds in phase I or II testing, the number of patients dosed is significantly less. Unfortunately, there is a significant amount of nonpublished data, which renders the overall assessment difficult, and the direct comparison among different types of artificial O2 carriers is significantly limited by the virtual nonexistence of studies that directly compare different products.

Lactate Measurement Interference by Hemoglobin-Based Oxygen Carriers (Oxyglobin??, Hemopure??, and Hemolink???)

We sought to determine whether hemoglobin-based oxygen carriers (HBOCs), hemoglobin glutamer-200 [bovine] (HBOC-200, Oxyglobin), hemoglobin glutamer-250 [bovine] (HBOC-201, Hemopure), and hemoglobin raffimer (Hemolink) interfere with the accuracy of lactate measurements. Combinations of concentrated L-lactate solution, HBOC, and blood or plasma with added PlasmaLyte-A were added to sample tubes to make a linear and constant increase in lactate concentration in consecutive samples. Sample lactate concentrations ranged from 5-110 mg/dL (0.6-12 mm) (physiological reference range: 5-20 mg/dL [0.56-2.2 mm]). Comparisons were made between machine measured lactate concentrations and calculated lactate concentrations. For Hb glutamer-250, the average difference between measured and calculated lactate concentrations was -5.1 mg/dL (-0.57 mm) (LX-20), with greater underestimation at larger lactate concentrations. For Hb raffimer, the average difference was -2.2 mg/dL (-0.24 mm) (LX-20). The veterinary product, Hb glutamer-200, was tested on 3 analyzers (LX-20(R), YSI 1500, and YSI 2300). The YSI 1500 was the most accurate instrument with the mean difference between measured minus calculated lactate being +1.3 mg/dL versus -2.6 mg/dL (YSI 2300) and -8.4 mg/dL (LX-20). The clinical implications of this study are that with increasing levels of an HBOC in plasma, lactate interpretation may become inaccurate, especially at larger lactate concentrations, causing underestimation of measured lactate values and possible under-treatment of the patient. Therefore, caution must be exercised when interpreting lactate results when a HBOC is present in plasma.

The Effect of Hemopure?? on Coagulation in Clinically Relevant Concentrations

Hemopure is a new colloidal blood substitute that may influence coagulation. We designed this study to examine the influence of this product on in vitro coagulation of whole blood by using the thrombelastograph (TEG). Blood samples from 20 volunteers were obtained. Hemopure was added to blood samples to obtain 0.5, 1, and 2 g/dL mixtures of Hemopure in blood. Control consisted of an undiluted sample and, for comparison, two samples diluted with volumes of lactated Ringer's solution (LR) equivalent to the two higher Hemopure dilutions. TEG with Hemopure at a concentration of 2 g/dL showed significantly shorter reaction and clot formation k times and an increased alpha angle compared with control. LR dilution with equivalent volume to 2 g/dL Hemopure solution also resulted in significantly shorter reaction and k times, as well as an increased alpha angle. Coagulation in samples with Hemopure at concentrations of 0.5 and 1 mg/dL did not vary significantly from control. Maximum amplitude did not vary significantly from control in any samples. The effect of Hemopure on TEG measures of coagulation is not significantly different from that of LR at clinically relevant concentrations.

The impact of hemolysis on Ortho-Clinical Diagnostic's ECi and Roche's elecsys immunoassay systems

BACKGROUND

Hemolysis is regularly encountered in clinical specimens and often interferes with a variety of laboratory test methods. Although not widely recognized, immunoassays based on nonisotopic detection systems can also be affected by hemolysis. For this reason, we investigated the effect of differing amounts of hemolysis across a range of values for several immunoassays on the Ortho-Clinical Diagnostics ECi and Roche Elecsys platforms.

METHODS

Hemolysate was prepared from whole blood and spiked at varying concentrations into pooled patient serum samples for different analytes.

RESULTS

Out of the 21 analytes tested, six (28.6%) exhibited significant increases or decreases in measured concentrations with increasing amounts of hemolysis.

CONCLUSIONS

Although immunoassays are generally thought to be impervious to hemolysis interference, hemolysis can interfere in immunoassay testing platforms. For these reasons, we recommend that laboratories conduct hemolysis interference studies for all laboratory test protocols.

Pretreatment of serum containing hemoglobin vesicles (oxygen carriers) to prevent their interference in laboratory tests

Hemoglobin vesicles (HbV, diameter: 251 +/- 81 nm) are artificial oxygen (O2) carriers encapsulating concentrated hemoglobin (Hb) solution with phospholipid bilayer membrane, and their O2 transporting ability in vivo has been extensively studied. It is important to clarify the interference of the HbV suspension in clinical laboratory tests performed on serum and to establish a pretreatment method to avoid such an interference. The HbV suspension, acellular Hb solution ([Hb] = 10 g/dl) or saline, was mixed with a pooled human serum at various ratios up to 50 vol% ([Hb] = 5 g/dl), and the magnitude of the interference effect of HbV and Hb on 30 analytes was studied. The mixture of the HbV suspension and serum was ultracentrifuged (50,000 g, 20 min) to remove the HbV particles as precipitate, and the supernatant was analyzed and compared with the saline control group. The HbV particles were also removed by centrifugation (2,700 g, 30 min) in the presence of dextran (Mw 200 kDa). The HbV suspension showed considerable interference effects in most analytes. The majority of these effects was more serious than those of the acellular Hb solution. These findings are thought to be due to the light absorption of Hb in HbV and/or the light scattering generated in the suspension that interferes with the colorimetric and turbidimetric measurements. The components of HbV may also interfere with the chemical reactions of the studied assays. However, removal of the HbV from the supernatant diminished the interference in most of the assays: this is an advantage of HbV in comparison with acellular chemically modified Hb solutions.

Transfusion medicine: looking to the future

The evolution of transfusion medicine into a clinically oriented discipline emphasising patient care has been accompanied by challenges that need to be faced as specialists look to the future. Emerging issues that affect blood safety and blood supply, such as pathogen inactivation and more stringent donor screening questions, bring new pressures on the availability of an affordable blood supply. Imminent alternatives for management of anaemia, such as oxygen carriers, hold great promise but, if available, will require close oversight. With current estimates of HIV or hepatitis C viral (HCV) transmission approaching one in 2000000 units transfused, keeping to a minimum bacterial contamination of platelet products (one in 2000) and errors in transfusion, with its estimated one in 800000 mortality rate, assume great urgency. Finally, serious difficulties in blood safety and availability for poor, developing countries require innovative strategies and commitment of resources.

Validation of oxygen saturation measurements in a canine model of hemoglobin-based oxygen carrier infusion

This study was designed to validate oxygen saturation measurements from the NOVA CO-Oximeter (NOVA Biomedical Corporation, Waltham, MA), the i-STAT System (Sensor Devices, Waukesha, WI), and the Corning 170 blood gas analyzer (Bayer Corporation, East Walpole, MA) under conditions similar to the clinical application of a hemoglobin-based oxygen carrier (HBOC, hemoglobin glutamer-200 [bovine]; Oxyglobin, Biopure Corporation, Cambridge, MA). A canine model was used for both in vitro and in vivo experiments. In vivo experiments were conducted in a canine laboratory, and in vitro experiments were conducted in a tonometry laboratory. Study subjects were six mixed-breed dogs, each weighing approximately 30 kg. In the first set of experiments, the target blood po(2) levels were reached by tonometry. In the second set of experiments, quantitative measurements of total oxygen content with the LEXO2CON-K (HOSPEX Fiberoptics, Chestnut Hill, MA) were performed, immediately followed by measurements with the NOVA CO-Oximeter and the i-STAT system. HBOC was added in concentrations of 16.2, 32.5, 65, and 97.5 g/L. To analyze the clinical significance of the differences in the results obtained with the each investigated instrument, blood samples from dogs treated with HBOC after acute hemorrhagic shock were used. Oxygen saturation, oxygen content, and po(2) were measured. There was a strong correlation between the oxygen saturation values measured with the investigated instruments in samples after tonometry and known po(2). The total calculated oxygen content varied by 5% based on results generated by calculations using the investigated instruments. The results did not change with different oxygenation of the sample. The differences among methods were not significant when the HBOC concentration was 16.2 g/L. Higher concentrations of HBOC increased the difference between calculated and measured oxygen content; the i-STAT system demonstrated a greater deviation compared with the results of the other two instruments. Systemic oxygen uptake using the investigated instruments showed a high correlation with values based on LEXO2CON-K measurements (R = 0.97 for CO-Oximeter, R = 0.96 for Corning 170 blood gas analyzer, and R = 0.79 for i-STAT system). Systemic oxygen uptake values based on CO-Oximeter and Corning 170 blood gas analyzer data showed 75% accuracy; i-STAT system accuracy was 63% for control samples and 50% for samples after HBOC infusion.

Detection of hantavirus infection in hemolyzed mouse blood using alkaline phosphatase conjugate

Conventional methods such as ELISA and culture require a long time for the determination of viral infections. Fast and reliable instrumentation suitable for operation under field conditions that allows rapid detection of hantavirus in rodent populations in the wild, would be a substantial improvement over these methods. In response to this challenge, a prototype amperometric immunosensor based on highly dispersed immunoelectrode for rapid, sensitive and quantitative assay of hantavirus in mice blood has been developed. A sandwich scheme of immunoassay is used and the naphthol that is formed as a result of enzymatic hydrolysis of alpha-naphthyl phosphate in the presence of alkaline phosphatase (AP) label is quantified amperometrically. The main complication faced when testing the amperometric immunosensor for application to mouse blood samples under field conditions is the removal of the interference caused by the electroactive components due to the hemolysis of the samples. We studied the possibility of using other enzyme markers such as AP to replace the horseradish peroxidase (HRP) used earlier in testing for antibodies against hantavirus in human blood plasma. Best results were obtained when the reference electrode is covered with a thin Nafion layer. Further improvement of assay performance was achieved by the modification of the sensing element. The amperometric immunoelectrode showed significantly higher sensitivity (more than 10-fold) than the standard spectrophotometric detection ELISA method. It can also be used for rapid analysis in conventional and field conditions in biological, physiological and analytical practices.

Beyond EPO

The objective of this review is to examine newer compounds coming on the market capable of boosting red blood cell concentration and thus improving aerobic activities in particular. Erythropoietin (EPO) has been used extensively in the past by the athletic community in this role. Its main disadvantages are the side effects due to increased viscosity, and the recent development of a blood test for drug testing methods. Two new methods of increasing red blood cell concentration for use in medicine are hemoglobin oxygen carriers and perfluorocarbons, each having a different structure, but which allow oxygen to be delivered to the tissues. Hemoglobin oxygen carriers physically alter the hemoglobin molecule by several methods so that complications such as renal toxicity are obviated. Perfluorocarbons belong to a group of synthetic compounds containing hydrocarbons to which fluorine is added. Evidence is available to suggest that athletes are already adapting these newer molecules for their benefit.

Oxygen saturation measurements in canine blood containing hemoglobin glutamer-200 (Bovine): in vitro validation of the NOVA CO-Oximeter

This study was designed to validate in vitro oxygen saturation (SO2) measurements with the NOVA CO-Oximeter (Nova Biomedical Corp, Waltham, Mass, USA) in canine blood containing hemoglobin (Hb) glutamer-200 bovine (Hb-200; Oxyglobin, Biopure, Cambridge, Mass, USA) as a Hb-based oxygen carrier recently introduced into clinical practice. In the first set of experiments, stored blood from 6 mixed-breed canine blood donors was used. Target PO2 levels were reached in aliquots of blood samples by tonometry. Oxygen saturation was then measured with the test device and calculated based on known PO2 values. In the second set of experiments, total oxygen content was directly measured by means of an oxygen-specific electrode in aliquots of fresh whole arterial, venous, and mixed (arterial-venous) blood withdrawn from the same canine blood donors. Hb-200 was added to those blood samples to yield plasma Hb concentrations of 1.62, 3.25, 6.50, and 9.75 g/dL. Based on Hb content and SO2 measured by the NOVA CO-Oximeter in these samples, total oxygen content was also calculated for each sample and compared with measured values. A strong correlation was found between SO2 values measured with the co-oximeter in samples after tonometry, and calculated SO2 based on known PO2. Directly measured total blood O2 content varied by </=5% from values computed based on co-oximeter measurements of Hb content and SO2. These results did not change with different levels of oxygenation of the samples or different plasma Hb-200 concentrations. In conclusion, the NOVA CO-Oximeter is an accurate analyzer for measurement of SO2 after Hb-200 administration to canine blood.

Co-oximetry interference by hemoglobin-based blood substitutes

The blood substitutes now being developed from molecularly modified hemoglobin interfere with a wide variety of clinical analyzers, but their effects on cooximeters are unknown. Therefore, we investigated the effects of five hemoglobin-based blood substitutes on the measurements of eight different oximeters and cooximeters: the AVL Omni 6, the AVOXimeters 1000 and 4000, the Ciba Corning (now Bayer) CC270 CO-Oximeter, the Instrumentation Laboratory Synthesis 35, the IL482 and IL682 CO-Oximeters, and the Radiometer OSM3 Hemoximeter. The five blood substitutes in this study were obtained from Apex Bioscience (Research Triangle Park, NC), Baxter Healthcare Corp. (Deerfield, IL), Biopure Corp. (Cambridge, MA), Hemoglobin Therapeutics, and Hemosol, Inc. (Etobicoke, Ontario, Canada). A cooximeter control was used to compare the eight different instruments' measurements on unaltered human hemoglobin. The instruments yielded measurements of total hemoglobin concentration in undiluted blood substitutes that were generally not more variable than those on the control material. By contrast, when compared with readings on controls, the test instruments yielded measurements of the fractional concentrations of oxy-, deoxy-, carboxy-, and methemoglobin that showed greater instrument-to-instrument disparities and larger standard deviations about the all-instrument means. In some cases, the interference was even more obvious: five of six cooximeters gave negative carboxyhemoglobin readings on one particular product. Our findings indicate that the instruments will give less accurate but clinically useful measurements in the presence of these hemoglobin-based blood substitutes.

IMPLICATIONS

We investigated the effects of five hemoglobin-based blood substitutes on the measurements of eight different cooximeters. Some blood substitutes caused obvious interference, such as negative carboxyhemoglobin readings; however, the findings indicate that cooximeters will generally give less accurate but clinically useful measurements in the presence of the hemoglobin-based blood substitutes that were tested.

Impact of Ultra-Sensitive technology and contemporary therapy on laboratory results

The introduction of ultra-sensitive labels for immunoassays has exposed some of the limitations inherent in them. Thus, for instance a major problem with acridinium esters used, as chemiluminescence label is the formation of the so called "pseudobases" at an alkaline pH, which if not suppressed can affect the rate of the chemiluminescence reaction. Chemiluminescence labels such as luminol can also be problematic when attached to antibodies and small molecules to the extent that the sensitivity of the assay can be reduced by the decrease in the intensity of chemiluminescence. The increased use of molecular methods such as polymerase chain reaction (PCR) and post PCR methods to study mutations have various pittalls, which if unrecognized and uncontrolled can lead to incorrect results and misinterpretation. Patients who are exposed to mouse immunoglobulins through imaging or therapeutic techniques can develop antibodies to mouse immunoglobulins (human anti-mouse antibodies or HAMA) which can be a major problem for non optimized immunoassays using murine monoclonal antibodies. The types of therapy such as anticoagulant used in anticoagulant therapy, blood substitute and drug therapy can impact on the measurements of some of the biochemical and other analytes. One must separate the transient, physiological effects introduced by therapy from long-term biochemical alterations due to disease.

Remission in models of type 1 diabetes by gene therapy using a single-chain insulin analogue

A cure for diabetes has long been sought using several different approaches, including islet transplantation, regeneration of beta cells and insulin gene therapy. However, permanent remission of type 1 diabetes has not yet been satisfactorily achieved. The development of type 1 diabetes results from the almost total destruction of insulin-producing pancreatic beta cells by autoimmune responses specific to beta cells. Standard insulin therapy may not maintain blood glucose concentrations within the relatively narrow range that occurs in the presence of normal pancreatic beta cells. We used a recombinant adeno-associated virus (rAAV) that expresses a single-chain insulin analogue (SIA), which possesses biologically active insulin activity without enzymatic conversion, under the control of hepatocyte-specific L-type pyruvate kinase (LPK) promoter, which regulates SIA expression in response to blood glucose levels. Here we show that SIA produced from the gene construct rAAV-LPK-SIA caused remission of diabetes in streptozotocin-induced diabetic rats and autoimmune diabetic mice for a prolonged time without any apparent side effects. This new SIA gene therapy may have potential therapeutic value for the cure of autoimmune diabetes in humans.

Update on Transfusion Therapy

The science and technology of transfusion have improved dramatically over the past decade. Improvements in screen ing for viral pathogens have reduced the risk of transfusion transmitted viral infections to historic lows. Newly recog nized entities, including the transfusion transmitted virus and Parvo viruses are being investigated as pathogens. There is increasing appreciation that bacterial infection and parasites may be transmitted via transfusion, and a variety of approaches are being developed to deal with them. Clin ical studies continue to conflict about what the ideal hemo globin for patients with cardiovascular disease should be, but several studies suggest that higher hematocrits may be beneficial. Factor deficiency may play a more important role in massive transfusion than previously believed. The impor tance of autologous predeposit of red cells and hemodilu tion may diminish as the blood supply becomes ever safer, but intraoperative salvage is likely to remain an important technique. Finally, although blood substitutes have been under development for more than 10 years, they have not yet become widely used in medicine. The few remaining products under development are presently in advanced clin ical trials but face a variety of clinical and economic obsta cles before they can rise to their potential.

Randomized safety studies of intravenous perflubron emulsion. I. Effects on coagulation function in healthy volunteers

Previous perfluorocarbon (PFC) emulsions have been associated with transient adverse events (i.e., platelet activation, decreased platelet count, febrile responses, changes in hemodynamic function). The Phase I studies described in this report were parallel, randomized, double-blinded, placebo-controlled studies conducted in 48 healthy volunteers (n = 24 per study) with perflubron emulsion (Oxygent; Alliance Pharmaceutical Corp., San Diego, CA). Because of the decreased platelet counts observed with previous PFC emulsions and the intended use of perflubron emulsion in surgical patients, these studies assessed postdosing coagulation responses and hemostasis. PFC pharmacokinetic variables were also evaluated. The primary endpoint for examination of coagulation effects was prospectively defined as bleeding time. Subjects received either saline (3 mL/kg) control, or perflubron emulsion at 1.2 g PFC/kg or 1.8 g PFC/kg, and were evaluated for a 14-day period. No postinfusion changes in bleeding time or differences in ex vivo agonist-induced platelet aggregation were observed. A 17% reduction in platelet count was observed 3 days after dosing in the 1.8-g PFC/kg group; levels recovered to baseline by Day 7. The intravascular half-life of perflubron for the first 24 h was dose dependent: 9.4+/-2.2 h and 6.1+/-1.9 h in the 1.8- and 1.2-g PFC/kg groups, respectively. Results indicate that this perflubron emulsion did not affect coagulation function in healthy volunteers.

Mechanism of Interference of a Polymerized Hemoglobin Blood Substitute in an Alkaline Phosphatase Method

Background: Hemoglobin-based oxygen carriers can cause profound interferences in many analytical procedures. We determined the mechanism of interference in the assay of alkaline phosphatase activity and identified approaches that might be used to correct for this interference.

Methods: Interference of a polymerized hemoglobin blood substitute with the assay of alkaline phosphatase was examined with a Hitachi 917 analyzer and ultraviolet-visible spectrophotometry.

Results: Hemoglobin-based oxygen carrier solutions had substantial absorbance at 415 nm, the wavelength of analysis used to measure the formation of 4-nitrophenol. In addition to offsetting the initial absorbance at the analytical wavelength, polymerized hemoglobin gave rise to a strong negative interference plot because of alkali denaturation of the substitute. The same interference mechanism was also observed for native hemoglobin (hemolysate), indicating that the interference was not derived from the polymerization process. The interference can be corrected by implementing a rate-correction procedure, or the interference can be avoided by measurement at 450 nm.

Conclusions: The interference of polymerized hemoglobin in the alkaline phosphatase assay is a result of an absorbance offset caused by alkali denaturation of hemoglobin. The interference can be corrected or avoided by modifying the calculation or the analytical wavelength. The correction strategy may also be applicable to improving the hemolysis index for this method.

Blood conservation in patients undergoing non-cardiac surgery

Concerns about the safety, inventory, and cost of allogeneic blood have led to a renewed interest in blood conservation. Autologous blood collection techniques, including preoperative autologous donation, acute normovolemic hemodilution, and perioperative blood recovery are routinely used as alternatives to allogeneic transfusion. In the future, these techniques may be combined with pharmacological strategies, such as presurgical erythropoietin therapy or red cell substitutes, to reduce further the need for allogeneic blood.

A second-generation blood substitute (Perfluorodichlorooctane emulsion) generates spurious elevations in platelet counts from automated hematology analyzers

Perfluorocarbon emulsions (PFEs) appear as platelets in automated cell counters, which may affect samples from thrombocytopenic patients (less than 100,000/microL). Therefore, we mixed clinically relevant concentrations of perfluorodichlorooctane (Oxyfluor(R); Hemagen, Inc., St. Louis, MO) in vitro with whole blood samples ranging from 0 to 150,000 platelets/microL and compared a new counter that uses optical platelet recognition (Abbott CellDyn 3200; Santa Clara, CA) with conventional electroimpedance-based counters (Abbott CellDyn 3500 and CellDyn 1700). We found that emulsion particles appear as small-sized platelets either in diluent or in blood. The emulsion results in a reproducible overestimate of the platelet counts, of greater importance as PFE concentration increases, and as the actual platelet count of the blood samples decreases. The new optical technology yields smaller overestimates but, even at low PFE concentrations, gives an unacceptable relative error at platelet counts near the transfusion thresholds recommended by the American Society of Anesthesiologists guidelines for blood component therapy. Unexpected interference in the leukocyte and erythrocyte channels is also reported. Experimental limitations preclude extrapolation of these findings to other automated cell counters, because differences in technology or software may affect their capacity to separate PFE particles from platelets.

IMPLICATIONS

Perfluorocarbons are being investigated under conditions in which thrombocytopenia is likely to occur. In this in vitro study, we demonstrate significant overestimates in platelet counts from automated cell counters at clinically relevant perfluorocarbon concentrations in thrombocytopenic blood samples.

Current status of artificial oxygen carriers

Artificial oxygen carriers may be grouped into modified hemoglobin solutions and fluorocarbon emulsions. In animal experiments, both have been shown to be efficacious in improving tissue oxygenation and as substitutes for blood transfusions. Advantages and disadvantages are being discussed in this article as well as the latest steps in the clinical development.