A prospective observational study of the incidence, natural history, and risk factors for intravenous immunoglobulin-mediated hemolysis.

BACKGROUND: Intravenous Immune Globulin (IVIG) is used to treat numerous immune-mediated and inflammatory conditions. There is growing awareness of hemolysis, occasionally severe, as a side-effect of this therapy. While most cases are associated with anti-A and/or anti-B isoagglutinins, the frequency and mechanism of hemolysis remain poorly characterized. STUDY DESIGN AND METHODS: A prospective observational study was conducted to determine incidence, natural history and risk factors for IVIG-mediated hemolysis. A total of 99 infusions of high-dose IVIG (2 g/kg or higher) administered to 78 non-group O patients were monitored and graded according to Canadian IVIG Hemolysis Pharmacovigilance Group. Serum ferritin and C3/C4 levels were monitored as indicators of macrophage activation and complement consumption, respectively. Supplementary investigations included assessment for ABO zygosity, Secretor status, FcR polymorphisms, eluate IgG subclass, monocyte monolayer assay, and a panel of cytokines. RESULTS: Hemolysis was observed in 32 of 99 (32%) of infusions, with 19 of 99 (19%) grade 2 or higher. Hemolysis was only apparent 5-10 days after a completed IVIG infusion in 84% of cases and was associated with increases in serum ferritin without complement-consumption. In univariate analysis, increased risk was observed in group AB patients, first-time IVIG recipients, those not taking immuosuppressive medications, or patients treated with a specific IVIG brand; however, in multivariate analysis, product association was no longer observed. No other patient- or practice-related risk factors were identified. CONCLUSION: IVIG-mediated hemolysis is common and frequently severe. Monitoring for 5-10 days following an infusion should be considered in non-O patients receiving high-dose IVIG with known risk factors.

The utility of a monocyte monolayer assay in the assessment of intravenous immunoglobulin-associated hemolysis.

BACKGROUND: Hemolysis following the administration of intravenous immunoglobulin (IVIG) is an important adverse event (AE). While the monocyte monolayer assay (MMA) has been used to predict in vivo hemolysis when serologically incompatible blood may be transfused, it has also been shown to correlate with IVIG-associated hemolysis. In this study, the MMA was examined for its utility in assessing the risk of hemolysis after IVIG. STUDY DESIGN AND METHODS: Forty-two non-blood group O patients receiving high-dose IVIG (≥2 g/kg) were examined using an autologous and allogeneic MMA. Hemolysis was defined by a drop in hemoglobin of ≥1 g/L, a positive direct antiglobulin test (DAT) and eluate, and a decrease in haptoglobin or increase in lactate dehydrogenase and/or reticulocytes. RESULTS: Forty-two patients provided 50 assessable postinfusion samples, with hemolysis observed in 20 (40%) of cases. Autologous MMA using post-IVIG red blood cells significantly correlated with clinical outcomes when compared to allogeneic MMA (P = .0320 vs .5806, t test). No significant difference in receiver operating characteristics was observed when comparing autologous MMA testing against DAT for the diagnosis of IVIG-associated hemolysis. However, when using samples collected 5 to 10 days after receipt of high-dose IVIG, the autologous MMA had higher sensitivity than the DAT. CONCLUSION: MMA testing with autologous monocytes collected 5 to 10 days after receipt of high-dose IVIG can be used for the diagnosis of IVIG-associated hemolysis and may be of particular value in cases in which the Day 5 to 10 DAT is negative.

Stability of 40 cytokines/chemokines in chronically ill patients under different storage conditions.

Numerous studies point to the utility of blood cytokine measurements in the diagnosis and treatment of human disease. Advances in detection allow robust multiplex analysis. However, cytokines are present at low levels and are produced and act in complex networks which can remain active in stored blood. A major barrier to the routine use of cytokines as clinical biomarkers is sample management prior to analysis. Studies on cytokine stability under storage frequently use 'spiked' normal control plasma or serum to generate detectable levels of the cytokines of interest. These conditions may oversimplify the reality of clinically complex samples and provide limited information regarding optimal management of whole blood samples prior to plasma separation. Cytokine stability has also been addressed previously using plasma from normal individuals under different conditions of anticoagulant use, storage time and temperature of storage. No studies have as yet been undertaken to address cytokine stability in critically ill patients which may differ from normal, healthy individuals due to underlying cofounders such as inflammation. To address these issues, we subjected samples from five patients exhibiting an inflammatory disease state to three storage extremes which might be encountered in a clinical setting, prior to analysis of 40 cytokines. Blood drawn into EDTA or ACD anticoagulant was immediately separated and plasma stored at -80 °C. Matched samples were stored as follows; whole blood overnight at room temperature, or whole blood or plasma stored 10 days at 4 °C. We used equivalence testing to determine the similarity of stored cytokine values to baseline values. In ACD plasma, Eotaxin, IL-6, IL-11, IL-15, IP10, MDC, MCP-1 met equivalence to baseline in all storage conditions while for EDTA plasma stored 10 days at 4 °C EGF, FGF2, Fractalkine, G-CSF, IL-1ß, IL-5, IL-6, IL-7, IL-11, IP-10, TGFα and TNFα showed equivalence to baseline measurements. Intraclass Correlation Coefficients (ICC) were calculated and the following cytokines showed good to excellent agreement across all 4 storage conditions: Eotaxin, IL-5, IL-6, IL-11, IL-13, IP-10, MCP-1 and TNFα when collected in EDTA, and Eotaxin, IL-5, IL-6, IL-11, IL12-p40, IL-15, IP-10 and MCP-1 when collected in ACD. Five plasma cytokines were identified as being the least stable in both ACD and EDTA: IL-7, IL-9, IL12p70, RANTES, sCD40L, while IL-1ß was identified as unstable stored in ACD plasma. This study identified several clinically important cytokines that are remarkably stable in blood and plasma, and some that stored poorly. To our knowledge, this is the first cytokine storage study to use medically unwell patient samples and equivalence testing to evaluate the stability of measured cytokine values after storage.

Can furosemide prevent transfusion-associated circulatory overload? Results of a pilot, double-blind, randomized controlled trial.

BACKGROUND: Transfusion-associated circulatory overload (TACO) is a leading cause of transfusion-attributable morbidity. It is unclear whether diuretics are safe and effective in preventing this reaction. MATERIALS AND METHODS: In a pilot controlled feasibility trial, inpatients 65 years or older ordered a single unit of red blood cells were randomized to pre-transfusion furosemide 20 mg or placebo intravenously. Primary outcome was the ability to enroll 80 patients within a 2-month time period. Secondary feasibility outcomes included proportion of RBC transfusions meeting eligibility criteria, proportion of eligible patients enrolled, and compliance to study protocol. Clinical outcomes included the incidence of TACO and associated complications. RESULTS: Nine months of enrollment were required for 80 patients to complete the study, due primarily to fewer transfusions than expected meeting eligibility criteria and lower than anticipated consent rates. Protocol compliance was below target due to missing chart documentation of patient fluid balance, and transfusion infusion time. Blinding was maintained throughout the study and treatment arms were well-balanced. A single case of TACO occurred in each arm, for an overall incidence of 2.5%. No differences in peri-transfusion vital signs, B-natriuretic peptide, or signs of furosemide toxicity were observed. CONCLUSION: The study protocol was not feasible as designed, primarily due to challenges in patient enrollment. Modifications to trial design to improve feasibility in future studies have been identified.

Randomization is not associated with socio-economic and demographic factors in a multi-center clinical trial of children with sickle cell anemia.

BACKGROUND: Few studies have investigated factors influencing participation rates for minority children with a chronic disease in clinical trials. The Silent Cerebral Infarct Multi-Center Clinical (SIT) Trial provides an opportunity to study the impact of demographic and socio-economic factors on randomization in a clinical trial among Black children. Our primary objective was to characterize the factors associated with successful randomization of children with sickle cell disease (SCD) and silent cerebral infarct (SCI) in the SIT Trial after initial consent. PROCEDURE: Differences in socio-economic and demographic variables, family history and disease-related variables were determined between eligible participants who were successfully randomized and those who were not randomized following initial consent. Head of household educational level and family income were examined separately for US versus non-US sites. RESULTS: Of 1,176 children enrolled in the SIT Trial, 1,016 (86%) completed screening. Of 208 (20%) children with qualifying SCI on pre-randomization MRI, 196 (94%) were successfully randomized. There were no differences in socio-economic, demographic, or disease-related variables between children who were or were not randomized. Participants from non-US sites were more likely to be randomized (22% vs. 12%, P = 0.011); although, randomization by country was associated with neither head of household education nor family income. CONCLUSION: In the SIT Trial, acceptance of random allocation was not associated with socio-economic or demographic factors. Although these factors may represent barriers for some participants, they should not bias investigators caring for children with SCD in their approach to recruitment for clinical trial participation.

Pregnancy outcomes in women with thalassemia in North America and the United Kingdom.

Improved survival in thalassemia has refocused attention on quality of life, including family planning. Understanding the issues associated with infertility and adverse pregnancy outcomes may impact clinical care of patients with thalassemia. We report the number and outcomes of pregnancies among subjects enrolled in Thalassemia Clinical Research Network (TCRN) registries and examine variables associated with successful childbirth. We identified 129 pregnancies in 72 women among the 264 women, age 18 years or older in our dataset. Over 70% of pregnancies resulted in live births and 73/83 (88%) of live births occurred at full term. Most pregnancies (78.2%) were conceived without reproductive technologies. Most (59.3%) pregnancies occurred while on chronic transfusion programs, however only 38.9% were on iron chelation. Four women developed heart problems. Iron burden in women who had conceived was not significantly different from age- and diagnosis-matched controls that had never been pregnant. There was also no difference in pregnancy outcomes associated with diagnosis, transfusion status, diabetes or Hepatitis C infection. Pregnancies occurred in 27.3% of women with thalassemia of child-bearing age in the TCRN registries, a notable increase from our previous 2004 report. With optimal health maintenance, successful pregnancies may be achievable.

Do children with central venous line (CVL) dysfunction have increased risk of symptomatic thromboembolism compared to those without CVL-dysfunction, while on cancer therapy?

BACKGROUND: Thromboembolism (TE) and infection are two common complications of central venous line (CVL). Thrombotic CVL-dysfunction is a common, yet less studied, complication of CVL. Two retrospective studies have reported significant association of CVL-dysfunction and TE. Recent studies indicate association of CVL-related small clot with infection. Infection is the most common cause of non-cancer related mortality in children with cancer. We and others have shown reduced overall survival (OS) in children with cancer and CVL-dysfunction compared to those without CVL-dysfunction. Despite these observations, to date there are no prospective studies to evaluate the clinical significance of CVL-dysfunction and it's impact on the development of TE, infection, or outcome of children with cancer. STUDY DESIGN: This is a prospective, analytical cohort study conducted at five tertiary care pediatric oncology centers in Ontario. Children (≤ 18 years of age) with non-central nervous system cancers and CVL will be eligible for the study. Primary outcome measure is symptomatic TE and secondary outcomes are infection, recurrence of cancer and death due to any cause. Data will be analyzed using regression analyses. DISCUSSION: The overall objective is to delineate the relationship between CVL-dysfunction, infection and TE. The primary aim is to evaluate the role of CVL-dysfunction as a predictor of symptomatic TE in children with cancer. We hypothesize that children with CVL-dysfunction have activation of the coagulation system resulting in an increased risk of symptomatic TE. The secondary aims are to study the impact of CVL-dysfunction on the rate of infection and the survival [OS and event free survival (EFS)] of children with cancer. We postulate that patients with CVL-dysfunction have an occult CVL-related clot which acts as a microbial focus with resultant increased risk of infection. Further, CVL-dysfunction by itself or in combination with associated complications may cause therapy delays resulting in adverse outcome.This study will help to identify children at high risk for TE and infection. Based on the study results, we will design randomized controlled trials of prophylactic anticoagulant therapy to reduce the incidence of TE and infection. This in turn will help to improve the outcome in children with cancer.

Determination of alpha-2-macroglobulin complexes by a new immuno-activity assay.

INTRODUCTION: Alpha-2-macroglobulin (α(2)M) is a broad specificity protease inhibitor which impacts several hemostatic pathways. Selective detection of various α(2)M complexes may be useful to define markers for the status of different hemostatic components. We present proof of principle for a novel assay to quantitatively measure α(2)M in complex with a variety of hemostatic factors. MATERIALS AND METHODS: The assay makes use of the fact that α(2)M entraps proteases within a molecular "cage", leaving them inaccessible to macromolecular substrates while retaining functionality against small synthetic substrates. Wells coated with anti-α(2)M antibodies were used to isolate the complexes from buffer or plasma, followed by detection of specific proteases with chromogenic substrates. Macromolecular inhibitors were added to eliminate signal from any unbound proteases. RESULTS: Calibration curves constructed with purified protease-α(2)M complexes were sigmoidal in nature, as is typical with immuno-assays. The specificity of signal production was confirmed with inhibitors that target either free protease, or both free and α(2)M-bound protease. The detection range of the assay was dependent on the protease being measured, and the surrounding matrix. Interference in detection of complexes in plasma was found to be caused, in part, by free α(2)M. Thrombin-α(2)M complexes were quantified in adult and newborn plasma following induction of thrombin generation and found to be significantly higher in adults, likely due to higher prothrombin levels. CONCLUSIONS: This assay provides a versatile platform method for quantification of multiple protease-α(2)M complexes. It may prove useful for mechanistic in vitro studies of hemostatic pathways, and potentially for clinical applications.

Binding of heparin to metals.

Heparin is a major prophylactic and treatment agent for thrombosis. Structurally, this anticoagulant is a polydisperse, highly negatively charged polysaccharide mixture that contains a variable density of sulfate group substituents per molecule. Previous study has shown that heparin molecules have a high affinity for a wide range of metal ions with varying oxidation states. However, reports in literature on binding of heparin to metals have investigated only a small sampling of heparin-metal ion interactions. Since interaction of heparin with fluid phase and cell surface macromolecules in vivo is dependent on the heparin structure when bound in a metal ion complex, a survey of the physical parameters for heparin binding to metals is imperative. Atomic absorption and spectrophotometry experiments were performed for metal quantification, and in this study, the relative values for affinity constants and number of binding sites for heparin binding to several alkaline, alkaline earth, main group, and transition metals in their most common oxidation states are reported. We found an overall trend for heparin-metal affinity to be Mn(2+) > Cu(2+) > Ca(2+) > Zn(2+) > Co(2+) > Na(+) > Mg(2+) > Fe(3+) > Ni(2+) > Al(3+)> Sr(2+), with the trend in N (b) being opposite compared with the K (a).

Education and employment status of children and adults with thalassemia in North America.

BACKGROUND: Advances in the management of thalassemia have resulted in increased life expectancy and new challenges. We conducted the first survey of education and employment status of people with thalassemia in North America. PROCEDURES: A total of 633 patients (349 adults and 284 school age children) enrolled in the Thalassemia Clinical Research Network (TCRN) registry in Canada and the U.S. were included in the data analysis. Predictors considered for analysis were age, gender, race/ethnicity, site of treatment (Canada vs. United States), transfusion and chelation status, serum ferritin, and clinical complications. RESULTS: Seventy percent of adults were employed of which 67% reported working full-time. Sixty percent had a college degree and 14% had achieved some post-college education. Eighty-two percent of school age children were at expected grade level. In a multivariate analysis for adults, Whites (OR = 2.76, 95% CI: 1.50-5.06) were more likely to be employed compared to Asians. Higher education in adults was associated with older age (OR = 1.67, 95% CI: 1.29-2.15), female gender (OR = 2.08, 95% CI: 1.32-3.23) and absence of lung disease (OR = 14.3, 95% CI: 2.04-100). Younger children (OR = 5.7 for 10-year increments, 95% CI: 2.0-16.7) and Canadian patients (OR = 5.6, 95% CI: 1.5-20) were more likely to be at the expected education level. Neither transfusion nor chelation was associated with lower employment or educational achievement. CONCLUSIONS: Individuals with thalassemia in North America can achieve higher education; however, full-time employment remains a problem. Transfusion and chelation do not affect employment or education status of this patient population.

Effect of covalent antithrombin-heparin complex on developmental mechanisms in the lung.

We have developed a potent antithrombin (AT)-heparin conjugate (ATH) that is retained in the lung to prevent pulmonary thrombosis associated with respiratory distress in premature newborns. During continuing maturation, pulmonary angiogenesis in premature infants would be a crucial process in lung development. A naturally occurring latent form of antithrombin (L-AT) has antiangiogenic effects on lung vascularization. However, impact of latent ATH (L-ATH) on developing lung vascularization is unknown. Thus, effects of L-AT and L-ATH on fetal murine lung development were compared. Lung buds from embryonic day 11.5 (E11.5) Tie2-LacZ mouse embryos were incubated in DMEM plus FBS supplemented with PBS, AT, L-AT, heparin, ATH, or L-ATH. Vasculature of cultured explants was quantified by X-galactosidase staining. RNA was analyzed with murine gene probes for angiopoietin (Ang)-1, Ang-2, fibroblast growth factor 2 (FGF2), platelet endothelial cell adhesion molecule (PECAM), and vascular endothelial growth factor (VEGF). FGF2-supplemented medium was used to test contribution to effects of L-AT and L-ATH on angiogenesis. Epithelial branching morphogenesis was inhibited by L-AT (P = 0.003) and heparin (P < 0.001). L-AT and heparin decreased relative vascular area compared with PBS, ATH, and L-ATH. Expressions of all genes studied were downregulated by L-AT. However, L-AT and L-ATH inhibited branching morphogenesis and vasculature with added FGF2. These findings indicate that covalent linkage of AT to heparin negates disruptive effects of these moieties on lung morphology, vascularization, and growth factor gene expression. ATH may have enhanced safety as an anticoagulant during vascular development.

Quantitative analysis of catheter roughness induced by cutting and manipulation: a potential prothrombotic risk.

Thrombosis is a major complication of central venous access devices, its incidence depending on material, diameter, tip position, and tip surface. Catheters are usually cut to the appropriate length for accurate positioning. Cutting is not recommended, however, as rough surfaces can serve as a nidus for thrombosis. The present study was performed to assess the roughness of catheter tips provided by various manufacturers versus the roughness once cut and handled. Three types of catheters (Hickman, Port-a-Cath, and Per Q Cath) were cut by scissors, iris scissors, or scalpel, and were handled with debakey forceps, a needle driver, adson with teeth or adson without teeth, to determine the damage created on the catheter. The uncut manufactured tip was compared as a control. Scanning electron microscopy was used for imaging of all samples, and roughness was quantified by atomic force microscopy for the cutting methods. Qualitative results by scanning electron microscopy showed that scalpel-cut and manufactured ends appeared smoother relative to those cut with scissors or iris scissors. This complemented the roughness analysis by atomic force microscopy. Catheters handled by debakey forceps and adsons with teeth showed most roughness, visible as deep holes or a grainy surface when observed by high-magnification scanning electron microscopy. Overall, the smoothest result was produced by scalpel, followed by the manufactured end, scissors, and iris scissors. Handling should be minimized, and use of adsons with teeth, needle drivers and debakey forceps should be avoided, as they can leave permanent damage. Adsons without teeth appeared the least damaging.

Selective cleavage of heparin using aqueous 2-hydroxypyridine: production of an aldose-terminating fragment with high anticoagulant activity.

Unfractionated heparin (UFH) was partially depolymerized by heating at 115 degrees C with aqueous 2-hydroxypyridine. Compared to starting UFH, no significant loss of anticoagulant (anti-Xa) activity was observed. Products consisted of polysaccharide fragments and small quantities of ammonia, sulfate, and hexuronic acid. Fragments with aldose termini that reacted with [3H]NaBH4 (fragment A) were of relatively uniform size (6000 D) and increased as depolymerization time increased. Fragment A contained the anticoagulant activity, with 90-94% and 24-31% binding to Sepharose-thrombin and Sepharose-antithrombin, respectively. In contrast, a non-reducing fragment B that did not react with [3H]NaBH4 was more heterogeneous (6000-10,000 D) and did not have anticoagulant activity or Sepharose-antithrombin affinity. Given the polysaccharide 3H-incorporation, small release of monosaccharide products, and fragment A end-group analysis, thermolysis of UFH is likely limited to one site per molecule when protected by 2-hydroxypyridine. Thus, an anticoagulant fragment A is hydrolytically released from UFH leaving a variable-length fragment B complete with linkage region.

The fibrinolytic system in newborns and children.

The fibrinolytic system comprises a series of serine proteases that interact to cleave fibrin into fibrin degradation products. Although all key components of the fibrinolytic system are present at birth, important age-dependent, quantitative and qualitative differences are present during childhood as compared to adults. These differences include decreased plasma concentrations of plasminogen, tissue-type plasminogen activator and alpha2-antiplasmin, increased plasma concentrations of plasminogen activator inhibitor-1, as well as a decrease in both plasmin generation and overall fibrinolytic activity. Increasing evidence suggests that these age-dependent differences may contribute to the development of specific childhood diseases and influence the course of fibrinolytic therapy, particularly in newborns. This review aims to summarize the available information on the age-dependent features of the fibrinolytic system in newborns and children in healthy and disease states and the impact of these features on fibrinolytic therapy.

The influence of age on in vitro plasmin generation in the presence of fibrin monomer.

BACKGROUND AND OBJECTIVES: The components of the fibrinolytic system interact to generate plasmin from its zymogen form, plasminogen. At birth, all the components of the fibrinolytic system are present but with differing plasma concentrations. The present study was undertaken to explore the effect of physiological, age-dependent factors of the fibrinolytic system during childhood on the capacity to generate plasmin. DESIGN AND METHODS: Total plasmin generation was measured in venous plasma from umbilical cords and adults, on plastic and cell surfaces, in the presence of fibrin monomer, Desafib. Plasminogen, its inhibitors alpha2-antiplasmin and plasminogen activator inhibitor type 1, and plasmin-alpha2-antiplasmin complex in the time samples were assayed by enzyme-linked immunosorbent assay. The effect of addition of plasminogen on the plasmin generation in cord plasma and the effect of lipoprotein on adult and cord plasmin generation were measured. RESULTS: On the surface of human umbilical vein endothelial cells, onset of plasmin generation was earlier (40 min) compared to plastic (60 min) but total plasmin generation was similar on both surfaces. The addition of plasminogen to cord plasma increased plasmin generation. Supplementation of lipoprotein in adult plasma had an inhibitory effect, but there was no significant effect in cord plasma. INTERPRETATIONS AND CONCLUSIONS: Plasmin generation is reduced in newborn compared to adult plasma. Decreased plasmin generation in cord plasma is likely due to decreased plasminogen concentration. The antifibrinolytic effect of lipoprotein is more pronounced in adults as compared to newborns due to the presence of higher plasminogen concentration.

Effect of heparins on thrombin generation in hemophilic plasma supplemented with FVIII, FVIIa, or FEIBA.

Central venous catheters assist infusion of coagulation factors in hemophiliacs but can be problematic due to mechanical dysfunction, infection, and thrombosis. The effect of low molecular weight heparin, unfractionated heparin, or covalent antithrombin-heparin complex on thrombin generation in factor concentrate-supplemented hemophilic plasma were studied. Thrombin levels were similar to normal plasma after the addition of factor eight inhibitor bypassing agent to hemophilic plasma. At 0.2 U/ml of heparin, covalent antithrombin-heparin inhibited free thrombin generation to a greater degree than heparin and low molecular weight heparin. Covalent anti-thrombin-heparin may give a greater anticoagulant response in hemophilic plasma supplemented with factor VIII or factor VIIa than with factor eight inhibitor bypassing agent. Requirements for heparin in hemophilic patients with thrombosis may depend on the procoagulant treatment used.

Isoform composition of antithrombin in a covalent antithrombin-heparin complex.

Antithrombin (AT) circulates in two isoforms, alpha- (90-95%) and beta-AT (5-10%). AT inhibits clotting factors such as thrombin and factor Xa, a reaction catalyzed by heparin. Heparin has been used in many clinical situations but suffers from limitations such as a short intravenous half-life, bleeding risk, and the inability to inhibit thrombin bound to fibrin clots. In order to overcome some of heparin's limitations, we prepared a covalent AT-heparin complex (ATH) that has increased intravenous half-life, reduced bleeding risk, and can directly inhibit clot-bound thrombin. However, structural analysis is required to further develop this promising antithrombotic agent. It was found that the proportion of isoforms in ATH (55% alpha-AT, and 45% beta-AT) was significantly different than that in the commercial AT starting material (80% alpha-AT and 20% beta-AT). Further analysis of the rate of heparin-catalyzed inhibition of thrombin by AT isoforms prepared from ATH revealed that the beta-variant reacted approximately 2-fold faster.