Extracellular fluid tonicity impacts sickle red blood cell deformability and adhesion

Lactated Ringer vs Normal Saline Solution During Sickle Cell Vaso-Occlusive Episodes

Importance

Sickle cell disease (SCD), a clinically heterogenous genetic hemoglobinopathy, is characterized by painful vaso-occlusive episodes (VOEs) that can require hospitalization. Patients admitted with VOEs are often initially resuscitated with normal saline (NS) to improve concurrent hypovolemia, despite preclinical evidence that NS may promote erythrocyte sickling. The comparative effectiveness of alternative volume-expanding fluids (eg, lactated Ringer [LR]) for resuscitation during VOEs is unclear.

Objective

To compare the effectiveness of LR to NS fluid resuscitation in patients with SCD and VOEs.

Design, Setting, and Participants

This multicenter cohort study and target trial emulation included inpatient adults with SCD VOEs who received either LR or NS on hospital day 1. The Premier PINC AI database (2016-2022), a multicenter clinical database including approximately 25% of US hospitalizations was used. The analysis took place between October 6, 2023, and June 20, 2024.

Exposure

Receipt of LR (intervention) or NS (control) on hospital day 1.

Main Outcome and Measures

The primary outcome was hospital-free days (HFDs) by day 30. Targeted maximum likelihood estimation was used to calculate marginal effect estimates. Heterogeneity of treatment effect was explored in subgroups.

Results

A total of 55 574 patient encounters where LR (n = 3495) or NS (n = 52 079) was administered on hospital day 1 were included; the median (IQR) age was 30 (25-37) years. Patients who received LR had more HFDs compared with those who received NS (marginal mean difference, 0.4; 95% CI, 0.1-0.6 days). Patients who received LR also had shorter hospital lengths of stay (marginal mean difference, -0.4; 95% CI, -0.7 to -0.1 days) and lower risk of 30-day readmission (marginal risk difference, -5.8%; 95% CI, -9.8% to -1.8%). Differences in HFDs between LR and NS were heterogenous based on fluid volume received: among patients who received less than 2 L, there was no difference in LR vs NS; among those who received 2 or more L, LR was superior to NS.

Conclusion and Relevance

This cohort study found that, compared with NS, LR had a small but significant improvement in HFDs and secondary outcomes including 30-day readmission. These results suggest that, among patients with VOEs in whom clinicians plan to give volume resuscitation fluids on hospital admission, LR should be preferred over NS.

Association of baseline serum sodium with long-term outcomes in newly diagnosed coronary heart disease patients without heart failure: a prospective cohort study

Sodium is crucial for maintaining cardiovascular health, especially in relation to heart failure. The impact of baseline serum sodium concentrations on the outcomes of newly diagnosed coronary heart disease (CHD) without heart failure remains unclear. This prospective cohort study included 681 patients who were newly diagnosed with CHD. Cox proportional hazards models and restricted cubic spline (RCS) analysis were used to assess the relationship between serum sodium concentrations and major adverse cardiovascular events. The improvement in traditional prediction models by the addition of serum sodium concentrations was assessed using changes in the C-statistic, net reclassification improvement (NRI), and integrated discrimination improvement (IDI). During a median follow-up of 51.04 months (IQR: 40.88-53.80 months), 131 events were recorded. Multivariate Cox proportional hazards models showed that the L2 group (136-138.9 mmol/L) had the highest MACE risk. Compared to L2, the hazard ratios (HRs) and 95% confidence intervals (CIs) for the L1 (130-135.9 mmol/L), L3 (139-140.9 mmol/L), L4 (141-142.9 mmol/L), and L5 (143-147.0 mmol/L) groups were 0.31 (0.14-0.70, P = 0.005), 0.48 (030-0.78, P = 0.003), 0.56 (0.34-0.92, P = 0.022), and 0.37 (0.22-0.64, P < 0.001), respectively. Including serum sodium concentrations in the prediction model significantly improved the C-statistic from 0.647 to 0.679 (P = 0.022), with an NRI of 0.338 (P < 0.001) and an IDI of 0.026 (P < 0.001). RCS analysis showed a nonlinear relationship: within the 130-138 mmol/L sodium range, MACE risk gradually increased with higher sodium levels (HR 1.39, 95% CI 1.09-1.76, P = 0.008); whereas within the 138-147 mmol/L range, the risk gradually decreased (HR 0.88, 95% CI 0.80-0.98, P = 0.014). Baseline serum sodium concentrations are significantly associated with long-term cardiovascular risk in newly diagnosed CHD patients, showing an inverted U-shaped relationship, whereas low serum sodium may be specifically linked to higher risks of death and nonfatal myocardial infarction. Further research is needed to explore the impact of long-term changes in serum sodium concentrations on disease prognosis.

Intravenous Hydration and Associated Outcomes in Patients With Sickle Cell Disease Admitted With Vaso-Occlusive Crises: A Systematic Review

Acute painful vaso-occlusive crisis (VOC) is the common presentation of sickle cell disease (SCD) leading to emergency room visits, admissions, morbidity, mortality, and negative impacts on quality of life. Among various treatment approaches commonly employed to manage the condition, intravenous (IV) hydration is also frequently used in emergency and inpatient settings. Although helpful to overcome dehydration, IV hydration often leads to adverse outcomes like fluid overload, pulmonary edema, increased length of stay, transfer to intensive care unit, new oxygen requirement, etc. Small-scale retrospective studies are conducted to study the outcomes of IV hydration but have failed to conclusively demonstrate its benefits as well as choice of IV fluids, rate of IV fluid replacement, etc. We conduct this review as an attempt to summarize the available evidence on the role and utility of IV hydration in sickle cell crises along with reported adverse outcomes.

Hypothermal opto-thermophoretic tweezers

Optical tweezers have profound importance across fields ranging from manufacturing to biotechnology. However, the requirement of refractive index contrast and high laser power results in potential photon and thermal damage to the trapped objects, such as nanoparticles and biological cells. Optothermal tweezers have been developed to trap particles and biological cells via opto-thermophoresis with much lower laser powers. However, the intense laser heating and stringent requirement of the solution environment prevent their use for general biological applications. Here, we propose hypothermal opto-thermophoretic tweezers (HOTTs) to achieve low-power trapping of diverse colloids and biological cells in their native fluids. HOTTs exploit an environmental cooling strategy to simultaneously enhance the thermophoretic trapping force at sub-ambient temperatures and suppress the thermal damage to target objects. We further apply HOTTs to demonstrate the three-dimensional manipulation of functional plasmonic vesicles for controlled cargo delivery. With their noninvasiveness and versatile capabilities, HOTTs present a promising tool for fundamental studies and practical applications in materials science and biotechnology.

iCLOTS: open-source, artificial intelligence-enabled software for analyses of blood cells in microfluidic and microscopy-based assays

While microscopy-based cellular assays, including microfluidics, have significantly advanced over the last several decades, there has not been concurrent development of widely-accessible techniques to analyze time-dependent microscopy data incorporating phenomena such as fluid flow and dynamic cell adhesion. As such, experimentalists typically rely on error-prone and time-consuming manual analysis, resulting in lost resolution and missed opportunities for innovative metrics. We present a user-adaptable toolkit packaged into the open-source, standalone Interactive Cellular assay Labeled Observation and Tracking Software (iCLOTS). We benchmark cell adhesion, single-cell tracking, velocity profile, and multiscale microfluidic-centric applications with blood samples, the prototypical biofluid specimen. Moreover, machine learning algorithms characterize previously imperceptible data groupings from numerical outputs. Free to download/use, iCLOTS addresses a need for a field stymied by a lack of analytical tools for innovative, physiologically-relevant assays of any design, democratizing use of well-validated algorithms for all end-user biomedical researchers who would benefit from advanced computational methods.

Hypothermal opto-thermophoretic tweezers

Optical tweezers have profound importance across fields ranging from manufacturing to biotechnology. However, the requirement of refractive index contrast and high laser power results in potential photon and thermal damage to the trapped objects, such as nanoparticles and biological cells. Optothermal tweezers have been developed to trap particles and biological cells via opto-thermophoresis with much lower laser powers. However, the intense laser heating and stringent requirement of the solution environment prevent their use for general biological applications. Here, we propose hypothermal opto-thermophoretic tweezers (HOTTs) to achieve low-power trapping of diverse colloids and biological cells in their native fluids. HOTTs exploit an environmental cooling strategy to simultaneously enhance the thermophoretic trapping force at sub-ambient temperatures and suppress the thermal damage to target objects. We further apply HOTTs to demonstrate the three-dimensional manipulation of functional plasmonic vesicles for controlled cargo delivery. With their noninvasiveness and versatile capabilities, HOTTs present a promising tool for fundamental studies and practical applications in materials science and biotechnology.

Hyperviscosity syndromes; hemorheology for physicians and the use of microfluidic devices

PURPOSE OF REVIEW

Hyperviscosity syndromes can lead to significant morbidity and mortality. Existing methods to measure microcirculatory rheology are not readily available and limited in relevance and accuracy at this level. In this review, we review selected hyperviscosity syndromes and the advancement of their knowledge using microfluidic platforms.

RECENT FINDINGS

Viscosity changes drastically at the microvascular level as the physical properties of the cells themselves become the major determinants of resistance to blood flow. Current, outdated viscosity measurements only quantify whole blood or serum. Changes in blood composition, cell number, or the physical properties themselves lead to increased blood viscosity. Given the significant morbidity and mortality from hyperviscosity syndromes, new biophysical tools are needed and being developed to study microvascular biophysical and hemodynamic conditions at this microvascular level to help predict those at risk and guide therapeutic treatment.

SUMMARY

The use of 'lab-on-a-chip' technology continues to rise to relevance with point of care, personalized testing and medicine as customizable microfluidic platforms enable independent control of many in vivo factors and are a powerful tool to study microcirculatory hemorheology.

Intravenous Fluid Administration and the Risk of Adverse Outcomes in Sickle Cell Disease Patients Hospitalized for Vaso-Occlusive Crisis

Vaso-occlusive crisis (VOC) is the leading cause of hospitalization in sickle cell disease (SCD). Intravenous fluid (IVF) administration is the usual practice during VOC episodes to slow the sickling process. In the absence of an evidence-based, clear-cut consensus on the optimal choice, route, and rate of fluid administration, there has been a wide variability in the practice of IVF administration in the treatment of VOC. However, there are growing concerns about the safety of this practice. This systematic review summarized the current evidence on the risk of negative outcomes in SCD patients treated for VOC with IVFs. A database search of Medline/PubMed, EMBASE, Scopus, Web of Science, CINAHL, Wiley Cochrane Library, Clinicaltrials.gov, and conference proceedings of the European Hematology Association (EHA) and American Society of Hematology (ASH) were performed. The results were presented using narrative analysis of quantitative data. Of the 2,821 identified records, a total of three eligible retrospective cohort studies with a total demographic population of 549 SCD patients were included in this review. Normal saline, a frequently used IVF for VOC may be associated with adverse outcomes such as poor pain control and volume overload. Volume overload, new oxygen requirement, acute chest syndrome, and acute kidney injury are potential adverse outcomes of inappropriate IVF use in VOC. There is limited evidence supporting the current practice of IVF use in VOC. Randomized controlled trials are required to fully clarify the place and safety of IVF in the management of VOC.

Microfluidics in vascular biology research: a critical review for engineers, biologists, and clinicians

Neovascularization, the formation of new blood vessels, has received much research attention due to its implications for physiological processes and diseases. Most studies using traditional in vitro and in vivo platforms find challenges in recapitulating key cellular and mechanical cues of the neovascularization processes. Microfluidic in vitro models have been presented as an alternative to these limitations due to their capacity to leverage microscale physics to control cell organization and integrate biochemical and mechanical cues, such as shear stress, cell-cell interactions, or nutrient gradients, making them an ideal option for recapitulating organ physiology. Much has been written about the use of microfluidics in vascular biology models from an engineering perspective. However, a review introducing the different models, components and progress for new potential adopters of these technologies was absent in the literature. Therefore, this paper aims to approach the use of microfluidic technologies in vascular biology from a perspective of biological hallmarks to be studied and written for a wide audience ranging from clinicians to engineers. Here we review applications of microfluidics in vascular biology research, starting with design considerations and fabrication techniques. After that, we review the state of the art in recapitulating angiogenesis and vasculogenesis, according to the hallmarks recapitulated and complexity of the models. Finally, we discuss emerging research areas in neovascularization, such as drug discovery, and potential future directions.

Microfluidic methods to advance mechanistic understanding and translational research in sickle cell disease

Sickle cell disease (SCD) is caused by a single point mutation in the β-globin gene of hemoglobin, which produces an altered sickle hemoglobin (HbS). The ability of HbS to polymerize under deoxygenated conditions gives rise to chronic hemolysis, oxidative stress, inflammation, and vaso-occlusion. Herein, we review recent findings using microfluidic technologies that have elucidated mechanisms of oxygen-dependent and -independent induction of HbS polymerization and how these mechanisms elicit the biophysical and inflammatory consequences in SCD pathophysiology. We also discuss how validation and use of microfluidics in SCD provides the opportunity to advance development of numerous therapeutic strategies, including curative gene therapies.

Tripartite collaboration of blood-derived endothelial cells, next generation RNA sequencing and bioengineered vessel-chip may distinguish vasculopathy and thrombosis among sickle cell disease patients

Sickle cell disease (SCD) is the most prevalent inherited blood disorder in the world. But the clinical manifestations of the disease are highly variable. In particular, it is currently difficult to predict the adverse outcomes within patients with SCD, such as, vasculopathy, thrombosis, and stroke. Therefore, for most effective and timely interventions, a predictive analytic strategy is desirable. In this study, we evaluate the endothelial and prothrombotic characteristics of blood outgrowth endothelial cells (BOECs) generated from blood samples of SCD patients with known differences in clinical severity of the disease. We present a method to evaluate patient-specific vaso-occlusive risk by combining novel RNA-seq and organ-on-chip approaches. Through differential gene expression (DGE) and pathway analysis we find that BOECs from SCD patients exhibit an activated state through cell adhesion molecule (CAM) and cytokine signaling pathways among many others. In agreement with clinical symptoms of patients, DGE analyses reveal that patient with severe SCD had a greater extent of endothelial activation compared to patient with milder symptoms. This difference is confirmed by performing qRT-PCR of endothelial adhesion markers like E-selectin, P-selectin, tissue factor, and Von Willebrand factor. Finally, the differential regulation of the proinflammatory phenotype is confirmed through platelet adhesion readouts in our BOEC vessel-chip. Taken together, we hypothesize that these easily blood-derived endothelial cells evaluated through RNA-seq and organ-on-chips may serve as a biotechnique to predict vaso-occlusive episodes in SCD patients and will ultimately allow better therapeutic interventions.

Fluid overload due to intravenous fluid therapy for vaso-occlusive crisis in sickle cell disease: incidence and risk factors

Intravenous fluid therapy (IV‐FT) is routinely used in the treatment of vaso‐occlusive crises (VOCs), as dehydration possibly promotes and sustains erythrocyte sickling. Patients with sickle cell disease (SCD) are at risk of developing diastolic dysfunction and fluid overload due to IV‐FT. However, data on the adverse effects of IV‐FT for VOC is sparse. We aimed to evaluate the incidence and risk factors of fluid overload due to IV‐FT in patients with SCD. Consecutive hospitalisations for VOC treated with IV‐FT between September 2016 and September 2018 were retrospectively analysed. The median (interquartile range) age was 25·0 (18·3–33·8) years and 65% had a severe genotype (HbSS/HbSβ⁰‐thal). Fluid overload occurred in 21% of 100 patients. Hospital stay was longer in patients with fluid overload (6·0 vs. 4·0 days, P = 0·037). A positive history of fluid overload (P = 0·017), lactate dehydrogenase level (P = 0·011), and top‐up transfusion during admission (P = 0·005) were independently associated with fluid overload occurrence. IV‐FT was not reduced in 86% of patients despite a previous history of fluid overload. Fluid overload is frequently encountered during IV‐FT for VOC. IV‐FT is often not adjusted despite a positive history of fluid overload or when top‐up transfusion is indicated, emphasising the need for more awareness of this complication and a personalised approach.

Vascularized Microfluidics and Their Untapped Potential for Discovery in Diseases of the Microvasculature

Microengineering advances have enabled the development of perfusable, endothelialized models of the microvasculature that recapitulate the unique biological and biophysical conditions of the microcirculation in vivo. Indeed, at that size scale (<100 μm)-where blood no longer behaves as a simple continuum fluid; blood cells approximate the size of the vessels themselves; and complex interactions among blood cells, plasma molecules, and the endothelium constantly ensue-vascularized microfluidics are ideal tools to investigate these microvascular phenomena. Moreover, perfusable, endothelialized microfluidics offer unique opportunities for investigating microvascular diseases by enabling systematic dissection of both the blood and vascular components of the pathophysiology at hand. We review (a) the state of the art in microvascular devices and (b) the myriad of microvascular diseases and pressing challenges. The engineering community has unique opportunities to innovate with new microvascular devices and to partner with biomedical researchers to usher in a new era of understanding and discovery of microvascular diseases.

Time to rethink haemoglobin threshold guidelines in sickle cell disease

Alleviating anaemia in patients with sickle cell disease (SCD) is crucial in managing acute complications, mitigating end‐organ damage and preventing early mortality. Some disease‐modifying and curative therapies have increased haemoglobin (Hb) levels to exceed 100 g/l, a threshold above which complications from red blood cell (RBC) transfusions have occurred, raising concern about whole‐blood viscosity‐related complications with these therapies. Here we discuss the rationale behind this limit, the effect of viscosity on blood flow and the applicability of this Hb threshold to therapies for SCD beyond RBC transfusions.

Acute Liver Failure From Sickle Cell Hepatopathy Treated With Exchange Transfusion

Sickle cell disease (SCD) is a qualitative hemoglobinopathy that can cause widespread sickling and vaso-occlusive events in all organ systems. Sickle cell hepatopathy is an umbrella term for various acute and chronic pathologies of the liver as a result of sickling in SCD patients. We present below the case of a 49-year-old woman who had an acute liver failure in the setting of a hepatic crisis with recovery after exchange transfusion. Hepatic involvement in SCD may be life-threatening. Understanding the etiology and severity of hepatic involvement by sickling is necessary for appropriate treatment.

Concurrent Assessment of Deformability and Adhesiveness of Sickle Red Blood Cells by Measuring Perfusion of an Adhesive Artificial Microvascular Network

Biomarker development is a key clinical research need in sickle cell disease (SCD). Hemorheological parameters are excellent candidates as abnormal red blood cell (RBC) rheology plays a critical role in SCD pathophysiology. Here we describe a microfluidic device capable of evaluating RBC deformability and adhesiveness concurrently, by measuring their effect on perfusion of an artificial microvascular network (AMVN) that combines microchannels small enough to require RBC deformation, and laminin (LN) coating on channel walls to model intravascular adhesion. Each AMVN device consists of three identical capillary networks, which can be coated with LN (adhesive) or left uncoated (non-adhesive) independently. The perfusion rate for sickle RBCs in the LN-coated networks (0.18 ± 0.02 nL/s) was significantly slower than in non-adhesive networks (0.20 ± 0.02 nL/s), and both were significantly slower than the perfusion rate for normal RBCs in the LN-coated networks (0.22 ± 0.01 nL/s). Importantly, there was no overlap between the ranges of perfusion rates obtained for sickle and normal RBC samples in the LN-coated networks. Interestingly, treatment with poloxamer 188 decreased the perfusion rate for sickle RBCs in LN-coated networks in a dose-dependent manner, contrary to previous studies with conventional assays, but in agreement with the latest clinical trial which showed no clinical benefit. Overall, these findings suggest the potential utility of the adhesive AMVN device for evaluating the effect of novel curative and palliative therapies on the hemorheological status of SCD patients during clinical trials and in post-market clinical practice.

Microfluidic electrical impedance assessment of red blood cell-mediated microvascular occlusion

Alterations in the deformability of red blood cells (RBCs), occurring in hemolytic blood disorders such as sickle cell disease (SCD), contribute to vaso-occlusion and disease pathophysiology. There are few functional in vitro assays for standardized assessment of RBC-mediated microvascular occlusion. Here, we present the design, fabrication, and clinical testing of the Microfluidic Impedance Red Cell Assay (MIRCA) with embedded capillary network-based micropillar arrays and integrated electrical impedance measurement electrodes to address this need. The micropillar arrays consist of microcapillaries ranging from 12 μm to 3 μm, with each array paired with two sputtered gold electrodes to measure the impedance change of the array before and after sample perfusion through the microfluidic device. We define RBC occlusion index (ROI) and RBC electrical impedance index (REI), which represent the cumulative percentage occlusion and cumulative percentage impedance change, respectively. We demonstrate the promise of MIRCA in two common red cell disorders, SCD and hereditary spherocytosis. We show that the electrical impedance measurement reflects the microvascular occlusion, where REI significantly correlates with ROI that is obtained via high-resolution microscopy imaging of the microcapillary arrays. Further, we show that RBC-mediated microvascular occlusion, represented by ROI and REI, associates with clinical treatment outcomes and correlates with in vivo hemolytic biomarkers, lactate dehydrogenase (LDH) level and absolute reticulocyte count (ARC) in SCD. Impedance measurement obviates the need for high-resolution imaging, enabling future translation of this technology for widespread access, portable and point-of-care use. Our findings suggest that the presented microfluidic design and the integrated electrical impedance measurement provide a reproducible functional test for standardized assessment of RBC-mediated microvascular occlusion. MIRCA and the newly defined REI may serve as an in vitro therapeutic efficacy benchmark for assessing the clinical outcome of emerging RBC-modifying targeted and curative therapies.

Microfluidics in Sickle Cell Disease Research: State of the Art and a Perspective Beyond the Flow Problem

Sickle cell disease (SCD) is the monogenic hemoglobinopathy where mutated sickle hemoglobin molecules polymerize to form long fibers under deoxygenated state and deform red blood cells (RBCs) into predominantly sickle form. Sickled RBCs stick to the vascular bed and obstruct blood flow in extreme conditions, leading to acute painful vaso-occlusion crises (VOCs) – the leading cause of mortality in SCD. Being a blood disorder of deformed RBCs, SCD manifests a wide-range of organ-specific clinical complications of life (in addition to chronic pain) such as stroke, acute chest syndrome (ACS) and pulmonary hypertension in the lung, nephropathy, auto-splenectomy, and splenomegaly, hand-foot syndrome, leg ulcer, stress erythropoiesis, osteonecrosis and osteoporosis. The physiological inception for VOC was initially thought to be only a fluid flow problem in microvascular space originated from increased viscosity due to aggregates of sickled RBCs; however, over the last three decades, multiple molecular and cellular mechanisms have been identified that aid the VOC in vivo. Activation of adhesion molecules in vascular endothelium and on RBC membranes, activated neutrophils and platelets, increased viscosity of the blood, and fluid physics driving sickled and deformed RBCs to the vascular wall (known as margination of flow) – all of these come together to orchestrate VOC. Microfluidic technology in sickle research was primarily adopted to benefit from mimicking the microvascular network to observe RBC flow under low oxygen conditions as models of VOC. However, over the last decade, microfluidics has evolved as a valuable tool to extract biophysical characteristics of sickle red cells, measure deformability of sickle red cells under simulated oxygen gradient and shear, drug testing, in vitro models of intercellular interaction on endothelialized or adhesion molecule-functionalized channels to understand adhesion in sickle microenvironment, characterizing biomechanics and microrheology, biomarker identification, and last but not least, for developing point-of-care diagnostic technologies for low resource setting. Several of these platforms have already demonstrated true potential to be translated from bench to bedside. Emerging microfluidics-based technologies for studying heterotypic cell–cell interactions, organ-on-chip application and drug dosage screening can be employed to sickle research field due to their wide-ranging advantages.

Total hip arthroplasty for sickle cell osteonecrosis: guidelines for perioperative management

The prognosis of sickle cell disease (SCD) has greatly improved in recent years, resulting in an increased number of patients reporting musculoskeletal complications such as osteonecrosis of the femoral head. Total hip arthroplasty (THA) can be utilized to alleviate the pain associated with this disease.

Although it is well known that hip arthroplasty for avascular necrosis (AVN) in SCD may represent a challenge for the surgeon, complications are frequent, and no guidelines exist to prevent these complications. Because patients with SCD will frequently undergo THA, we thought it necessary to fulfil the need for guidance recommendations based on experience, evidence and agreement from the literature.

For all these reasons this review proposes guidelines that provide clinicians with a document regarding management of patients with SCD in the period of time leading up to primary THA. The recommendations provide guidance that has been informed by the clinical expertise and experience of the authors and available literature.

Although this is not a systematic review since some papers may have been published in languages other than English, our study population consisted of 5,868 patients, including 2,126 patients with SCD operated on for THA by the senior author in the same hospital during 40 years and 3,742 patients reported in the literature.

Cite this article: EFORT Open Rev 2020;5:641-651. DOI: 10.1302/2058-5241.5.190073

Randomized phase 2 trial of Intravenous Gamma Globulin (IVIG) for the treatment of acute vaso-occlusive crisis in patients with sickle cell disease: Lessons learned from the midpoint analysis

Sickle Cell Disease (SCD) is a chronic hemolytic disorder associated with frequent pain episodes, end organ damage and a shortened lifespan. Currently there exist no disease specific targeted therapies for the treatment of acute vaso-occlusive crisis (VOC) and management with analgesics and hydration is purely supportive. Improvement in understanding of disease pathophysiology has resulted in a great interest in disease modifying novel therapies and many are being evaluated in clinical trials. Here we report the results from the pre-specified mid-point analysis of the Phase 2 study of Intravenous Gamma Globulin (IVIG) for the treatment of acute VOC in patients with SCD and lessons learned.

Prognostic Value of Hyponatremia During Acute Painful Episodes in Sickle Cell Disease

BACKGROUND

Low plasma sodium concentration has been recognized as a prognostic factor in several disorders but never evaluated in sickle cell disease. The present study evaluates its value at admission to predict a complication in adult patients with sickle cell disease hospitalized for an initially uncomplicated acute painful episode.

METHODS

The primary outcome of this retrospective study, performed between 2010 and 2015 in a French referral center for sickle cell disease, was a composite criterion including acute chest syndrome, intensive care unit transfer, red blood cell transfusion or inpatient death. Analyses were adjusted for age, sex, hemoglobin genotype and concentration, lactate dehydrogenase (LDH) concentration, and white blood cell count.

RESULTS

We included 1218 stays (406 patients). No inpatient death occurred during the study period. Hyponatremia (plasma sodium ≤135 mmol/L) at admission in the center was associated with the primary outcome (adjusted odds ratio [OR] 1.95, 95% confidence interval [CI] 1.3-2.91, P = 0.001), with acute chest syndrome (OR 1.95 [95% CI 1.2-3.17, P = 0.008]), and red blood cell transfusion (OR 2.71 [95% CI 1.58-4.65, P <0.001]) but not significantly with intensive care unit transfer (OR 1.83 [95% CI 0.94-3.79, P = 0.074]). Adjusted mean length of stay was longer by 1.1 days (95% CI 0.5-1.6, P <0.001) in patients with hyponatremia at admission.

CONCLUSIONS

Hyponatremia at admission in the medical department for an acute painful episode is a strong and independent prognostic factor of unfavorable outcome and, notably, acute chest syndrome. It could help targeting patients who may benefit from closer monitoring.

How I Treat Acute and Persistent Sickle Cell Pain

Sickle pain is the hallmark of sickle cell disease (SCD). It could be acute, persistent/relapsing, chronic, or neuropathic. Although there is a general consensus that pain is a major manifestation of SCD, there is a controversy as to the types of pain and their interrelationship between acute, chronic, relapsing, persistent, etc. This report first reviews the general approach to the management of acute vaso-occlusive crisis (VOC) pain, including education, counseling, pharmacotherapy, non-pharmacotherapy, and fluid therapy. This is followed by the presentation of five patients that represent typical issues that are commonly encountered in the management of patients with SCD. These issues are: individualized treatment of pain, bilaterality of pain, use of illicit drugs, tolerance to opioids, opioid-induced hyperalgesia, and withdrawal syndrome. The clinical aspects and management of each of these issues are described. Moreover, such complications as tolerance and withdrawal may persist after discharge and may be mistaken as chronic pain rather than resolving, persistent or relapsing pain.

Kahar Method: A Novel Calculation Method of Tonicity Adjustment

Background:

Hypertonic and hypotonic conditions in pharmaceutical preparations decrease the drug’s absorption and bioavailability. In addition, it can cause tissue damage. There are several calculation methods to regulate hypotonic preparations. However, there are no methods that can be used to regulate hypertonic preparations without causing dose-dividing problem.

Objective:

This study aimed to develop a new calculation using basic principle of freezing point depression method (cryoscopic) that can solve hypotonic and hypertonic problems, especially for hypertonic preparations through reducing the levels of additional ingredients.

Methods:

The calculation of Kahar method was successfully obtained by substitution and simplification in the basic principle equation of cryoscopic method, and then evaluated by resolving the problems in 42 sterile formula preparations and compared with White–Vincent method, cryoscopic method, equivalent NaCl method, and milliequivalent method through the analysis of its similarity and reliability.

Results:

The results of similarity analysis between Kahar method and other methods showed good similarity values with more than 0.880. Kahar method and cryoscopic method have the highest similarity of the calculation result with a similarity value of 1. The reliability analysis obtained very good result with Cronbach α = 0.990.

Conclusions:

These results suggest that Kahar method provides reliable equation with complete and efficient solution to hypotonic and hypertonic problems.

Vascularized Microfluidics and the Blood-Endothelium Interface

The microvasculature is the primary conduit through which the human body transmits oxygen, nutrients, and other biological information to its peripheral tissues. It does this through bidirectional communication between the blood, consisting of plasma and non-adherent cells, and the microvascular endothelium. Current understanding of this blood-endothelium interface has been predominantly derived from a combination of reductionist two-dimensional in vitro models and biologically complex in vivo animal models, both of which recapitulate the human microvasculature to varying but limited degrees. In an effort to address these limitations, vascularized microfluidics have become a platform of increasing importance as a consequence of their ability to isolate biologically complex phenomena while also recapitulating biochemical and biophysical behaviors known to be important to the function of the blood-endothelium interface. In this review, we discuss the basic principles of vascularized microfluidic fabrication, the contribution this platform has made to our understanding of the blood-endothelium interface in both homeostasis and disease, the limitations and challenges of these vascularized microfluidics for studying this interface, and how these inform future directions.

Normal saline bolus use in pediatric emergency departments is associated with poorer pain control in children with sickle cell anemia and vaso-occlusive pain

Vaso-occlusive pain events (VOE) are the leading cause of emergency department (ED) visits in sickle cell anemia (SCA). This study assessed the variability in use of intravenous fluids (IVFs), and the association of normal saline bolus (NSB), on pain and other clinical outcomes in children with SCA, presenting to pediatric emergency departments (PED) with VOE. Four-hundred charts of children age 3-21 years with SCA/VOE receiving parenteral opioids at 20 high-volume PEDs were evaluated in a retrospective study. Data on type and amount of IVFs used were collected. Patients were divided into two groups: those who received NSB and those who did not. The association of NSB use on change in pain scores and admission rates was evaluated. Among 400 children studied, 261 (65%) received a NSB. Mean age was 13.8 ± 4.9 years; 46% were male; 92% had hemoglobin-SS. The IVFs (bolus and/or maintenance) were used in 84% of patients. Eight different types of IVFs were utilized and IVF volume administered varied widely. Mean triage pain scores were similar between groups, but improvement in pain scores from presentation-to-ED-disposition was smaller in the NSB group (2.2 vs 3.0, P = .03), while admission rates were higher (71% vs 59%, P = .01). Use of NSB remained associated with poorer final pain scores and worse change in pain scores in our multivariable model. In conclusion, wide variations in practice utilizing IVFs are common. NSB is given to >50% of children with SCA/VOE, but is associated with poorer pain control; a controlled prospective trial is needed to determine causality.

Patrolling monocytes scavenge endothelial-adherent sickle RBCs: a novel mechanism of inhibition of vaso-occlusion in SCD

Painful vaso-occlusive crisis (VOC) is the most common complication of sickle cell disease (SCD). Increasing evidence suggests that vaso-occlusion is initiated by increased adherence of sickle red blood cells (RBCs) to the vascular endothelium. Thus, the mechanisms that remove endothelial-attached sickle RBCs from the microvasculature are expected to be critical for optimal blood flow and prevention of VOC in SCD. We hypothesized that patrolling monocytes (PMos), which protect against vascular damage by scavenging cellular debris, could remove endothelial-adherent sickle RBCs and ameliorate VOC in SCD. We detected RBC (GPA⁺)-engulfed material in circulating PMos of patients with SCD, and their frequency was further increased during acute crisis. RBC uptake by PMos was specific to endothelial-attached sickle, but not control, RBCs and occurred mostly through ICAM-1, CD11a, and CD18. Heme oxygenase 1 induction, by counteracting the cytotoxic effects of engulfed RBC breakdown products, increased PMo viability. In addition, transfusions, by lowering sickle RBC uptake, improved PMo survival. Selective depletion of PMos in Townes sickle mice exacerbated vascular stasis and tissue damage, whereas treatment with muramyl dipeptide (NOD2 ligand), which increases PMo mass, reduced stasis and SCD associated organ damage. Altogether, these data demonstrate a novel mechanism for removal of endothelial attached sickle RBCs mediated by PMos that can protect against VOC pathogenesis, further supporting PMos as a promising therapeutic target in SCD VOC.

The biophysics and mechanics of blood from a materials perspective

Cells actively interact with their microenvironment, constantly sensing and modulating biochemical and biophysical signals. Blood comprises a variety of non-adherent cells that interact with each other and with endothelial and vascular smooth muscle cells of the blood vessel walls. Blood cells are further experiencing a range of external forces by the hemodynamic environment and they also exert forces to remodel their local environment. Therefore, the biophysics and material properties of blood cells and blood play an important role in determining blood behaviour in health and disease. In this Review, we discuss blood cells and tissues from a materials perspective, considering the mechanical properties and biophysics of individual blood cells and endothelial cells as well as blood cell collectives. We highlight how blood vessels provide a mechanosensitive barrier between blood and tissues and how changes in vessel stiffness and flow shear stress can be correlated to plaque formation and exploited for the design of vascular grafts. We discuss the effect of the properties of fibrin on blood clotting, and investigate how forces exerted by platelets are correlated to disease. Finally, we hypothesize that blood and vascular cells are constantly establishing a mechanical homeostasis, which, when imbalanced, can lead to hematologic and vascular diseases.

Small separation diffuse correlation spectroscopy for measurement of cerebral blood flow in rodents

Diffuse correlation spectroscopy (DCS) has shown promise as a means to non-invasively measure cerebral blood flow in small animal models. Here, we characterize the validity of DCS at small source-detector reflectance separations needed for small animal measurements. Through Monte Carlo simulations and liquid phantom experiments, we show that DCS error increases as separation decreases, although error remains below 12% for separations > 0.2 cm. In mice, DCS measures of cerebral blood flow have excellent intra-user repeatability and strongly correlate with MRI measures of blood flow (R = 0.74, p<0.01). These results are generalizable to other DCS applications wherein short-separation reflectance geometries are desired.

Oxygen-dependent flow of sickle trait blood as an in vitro therapeutic benchmark for sickle cell disease treatments

Although homozygous sickle cell disease is often clinically severe, the corresponding heterozygous state, sickle cell trait, is almost completely benign despite the fact that there is only a modest difference in sickle hemoglobin levels between the two conditions. In both conditions, hypoxia can lead to polymerization of sickle hemoglobin, changes in red cell mechanical properties, and impaired blood flow. Here, we test the hypothesis that differences in the oxygen-dependent rheological properties in the two conditions might help explain the difference in clinical phenotypes. We use a microfluidic platform that permits quantification of blood rheology under defined oxygen conditions in physiologically sized microchannels and under physiologic shear rates. We find that, even with its lower sickle hemoglobin concentration, sickle trait blood apparent viscosity increases with decreasing oxygen tension and may stop flowing under completely anoxic conditions, though far less readily than the homozygous condition. Sickle cell trait blood flow becomes impaired at significantly lower oxygen tension than sickle cell disease. We also demonstrate how sickle cell trait can serve as a benchmark for sickle cell disease therapies. We characterize the rheological effects of exchange transfusion therapy by mixing sickle blood with nonsickle blood and quantifying the transfusion targets for sickle hemoglobin composition below which the rheological response resembles sickle trait. These studies quantify the differences in blood flow phenotypes of sickle cell disease and sickle cell trait, and they provide a potentially powerful new benchmark for evaluating putative therapies in vitro.

Red cell transfusion in paediatric patients with thalassaemia and sickle cell disease: Current status, challenges and perspectives

Notwithstanding the high safety level of the currently available blood for transfusion and the decreasing frequency of transfusion-related complications, administration of labile blood products to paediatric patients still poses unique challenges and considerations. The incidence of thalassaemia and sickle cell disease in the paediatric population may be high enough under specific racial and geographical contexts. Red cell transfusion is the cornerstone of β-thalassaemia treatment and one of the most effective ways to prevent or correct specific acute and chronic complications of sickle cell disease. However, this life-saving strategy comes with its own complications, such as additional iron overload, alloimmunization and haemolytic reactions, among others. In paediatrics, the dependency of the transfusion outcome upon disease and other recipient characteristics is more prominent compared with the adults, owing to differences in developmental maturity and physiology that render them more susceptible to common risks, exacerbate the host response to transfused cells, and modify the type or the clinical severity of the transfusion-related morbidity. The adverse branch of red cell transfusion is likely the overall effect of several factors acting synergistically to shape the clinical phenotype of this therapy, including inherent donor/blood unit variables, like antigenicity, red cell deformability and extracellular vesicles, as well as recipient variables, such as history of alloimmunization and inflammation level at time of transfusion. This review focuses on paediatric patients with β-thalassaemia and sickle cell disease as a recipient group with distinct transfusion-related characteristics, and introduces new concepts for consideration, not adequately studied and elucidated so far.

Perioperative Management of Sickle Cell Disease

Over 30 million people worldwide have sickle cell disease (SCD). Emergent and non-emergent surgical procedures in SCD have been associated with relatively increased risks of peri-operative mortality, vaso-occlusive (painful) crisis, acute chest syndrome, post-operative infections, congestive heart failure, cerebrovascular accident and acute kidney injury. Pre-operative assessment must include a careful review of the patient’s known crisis triggers, baseline hematologic profile, usual transfusion requirements, pre-existing organ dysfunction and opioid use. Use of preoperative blood transfusions should be selective and decisions individualized based on the baseline hemoglobin, surgical procedure and anticipated volume of blood loss. Intra- and post-operative management should focus on minimizing hypoxia, hypothermia, acidosis, and intravascular volume depletion. Pre- and post-operative incentive spirometry use should be encouraged.

0.9% NaCl (Normal Saline) - Perhaps not so normal after all?

Crystalloid infusion is widely employed in patient care for volume replacement and resuscitation. In the United States the crystalloid of choice is often normal saline. Surgeons and anesthesiologists have long preferred buffered solutions such as Ringer's Lactate and Plasma-Lyte A. Normal saline is the solution most widely employed in medical and pediatric care, as well as in hematology and transfusion medicine. However, there is growing concern that normal saline is more toxic than balanced, buffered crystalloids such as Plasma-Lyte and Lactated Ringer's. Normal saline is the only solution recommended for red cell washing, administration and salvage in the USA, but Plasma-Lyte A is also FDA approved for these purposes. Lactated Ringer's has been traditionally avoided in these applications due to concerns over clotting, but existing research suggests this is not likely a problem. In animal models and clinical studies in various settings, normal saline can cause metabolic acidosis, vascular and renal function changes, as well as abdominal pain in comparison with balanced crystalloids. The one extant randomized trial suggests that in very small volumes (2 l or less) normal saline is not more toxic than other crystalloids. Recent evidence suggests that normal saline causes substantially more in vitro hemolysis than Plasma-Lyte A and similar solutions during short term storage (24 hours) after washing or intraoperative salvage. There are now abundant data to raise concerns as to whether normal saline is the safest replacement solution in infusion therapy, red cell washing and salvage, apheresis and similar uses. In the USA, Plasma-Lyte A is also FDA approved for use with blood components and is likely a safer solution for these purposes. Its only disadvantage is a higher cost. Additional studies of the safety of normal saline for virtually all current clinical uses are needed. It seems likely that normal saline will eventually be abandoned in favor of safer, more physiologic crystalloid solutions in the coming years.