Low Blood Flow Rates Research Articles

Improving the hemocompatibility of centrifugal mechanical circulatory support devices at low flow rates.

An innovative solution has been recently proposed for the treatment of heart failure with preserved ejection fraction (HFpEF), using a centrifugal mechanical circulatory support (MCS) device. We sought firstly to assess the hemocompatibility of the proposed device. HFpEF treatment requires the blood pump to operate at low blood flow rate (0.05-0.5 L/min). Given high blood trauma expected in these conditions, we sought secondly to investigate design improvements in order to reduce this risk. Computational fluid dynamics was used to analyze the blood fluid filled within the centrifugal pump and to estimate the blood trauma due to its operation. This assessment is based on the computation of integrated quantities such as the hemolysis index and the turbulent dissipation energy. The hemolysis index associated with the present device is comparable to the figures from HVAD. With the proposed pump, for instance, an index of 0.0036 is obtained at 1 L/min and 3000 rpm. Using thinner blades for the impeller allows a 12% reduction of the hemolysis index in average, while reducing its diameter leads to an index 2.8 folds lower at 0.5 L/min. The present investigation shows the promising hemocompatibility of our centrifugal pump. Concerns about very high hemolysis generated at low flow rates could be overcome by reducing the impeller diameter. Experimental validations are planned to support our findings.

The ADVanced Organ Support (ADVOS) hemodialysis system removes IL-6: an in vitro proof-of-concept study

BackgroundIL-6 is a pleiotropic cytokine modulating inflammation and metabolic pathways. Its proinflammatory effect plays a significant role in organ failure pathogenesis, commonly elevated in systemic inflammatory conditions. Extracorporeal blood purification devices, such as the Advanced Organ Support (ADVOS) multi hemodialysis system, might offer potential in mitigating IL-6's detrimental effects, yet its efficacy remains unreported.MethodsWe conducted a proof-of-concept in vitro study to assess the ADVOS multi system's efficacy in eliminating IL-6. Varying concentrations of IL-6 were introduced into a swine blood model and treated with ADVOS multi for up to 12 h, employing different blood and concentrate flow rates. IL-6 reduction rate, clearance, and dynamics in blood and dialysate were analyzed.ResultsIL-6 clearance rates of 0.70 L/h and 0.42 L/h were observed in 4 and 12-h experiments, respectively. No significant differences were noted across different initial concentrations. Reduction rates ranged between 40 and 46% within the first 4 h, increasing up to 72% over 12 h, with minimal impact from flow rate variations. Our findings suggest that an IL-6-albumin interaction and convective filtration are implicated in in vitro IL-6 elimination with ADVOS multi.ConclusionsThis study demonstrates for the first time an efficient and continuous in vitro removal of IL-6 by ADVOS multi at low blood flow rates. Initial concentration-dependent removal transitions to more consistent elimination over time. Further clinical investigations are imperative for comprehensive data acquisition.

Significance of effluent dose in continuous renal replacement therapy in children

Abstract Continuous renal replacement therapy (CRRT) is one of the commonly used extracorporeal blood purification therapies and its use in the pediatric population has increased in the past two decades due to the availability of safer machines which allow lower blood flow rate and dialysate flow rate. The usual indication for initiation of CRRT is for solute clearance and or fluid removal in oliguric patients with acute kidney injury. Knowledge regarding the principles of solute removal and fluid removal along with the application of these mechanisms in different modes of CRRT helps the physician to decide on the appropriate therapy for the given patient. Understanding the concept of CRRT dose and the factors to be considered in the prescription for achieving the preset targets of CRRT is vital for the efficient utilization of the therapy.

Effects of Hyperbaric Oxygen Therapy Combined with Music Therapy on Brain Function and Mental Health of Patients with Aneurismal Subarachnoid Hemorrhage: A Retrospective Study.

Hyperbaric oxygen therapy (HBOT), which is widely used in clinical practice, is aimed at improving nerve function impairment after brain injury. Meanwhile, the effects of music therapy on brain function are unclear. This retrospective study was conducted to explore the application effect of HBOT combined with music therapy on patients suffering from aneurysmal subarachnoid hemorrhage (aSAH). For this retrospective study, 130 patients with aSAH after HBOT were selected from our hospital from June 2021 to June 2022. The patients were divided into the observation (n = 70) and control (n = 60) groups based on whether they received music therapy. Comparisons were made on general demographic data, blood flow rate in median cerebral artery (MCA), cerebral vasospasm (CVS), National Institutes of Health Stroke Scale (NIHSS), activities of daily living (ADL) score, Self-Rating Depressive Scale (SDS), and Self-Rating Anxiety Scale (SAS) of patients. Baseline data between the two groups showed no statistically significant difference (P > 0.05). After management, patients in the observation group presented significantly lower SAS and SDS scores (P < 0.05), lower blood flow rate in MCA, CVS and NIHSS scores (P < 0.05), and higher ADL scores than the control group (P < 0.05). The combination of HBOT and music therapy can considerably improve cerebral neurological deficits, slow down cerebral arterial blood flow, promote the recovery of postoperative cerebral function in aSAH patients, and improve anxiety and depression and the patients' ADL.

When to consider intra-target microdosing: physiologically based pharmacokinetic modeling approach to quantitatively identify key factors for observing target engagement.

Intra-Target Microdosing (ITM), integral to Phase 0 clinical studies, offers a novel approach in drug development, effectively bridging the gap between preclinical and clinical phases. This methodology is especially relevant in streamlining early drug development stages. Our research utilized a Physiologically Based Pharmacokinetic (PBPK) model and Monte Carlo simulations to examine factors influencing the effectiveness of ITM in achieving target engagement. The study revealed that ITM is capable of engaging targets at levels akin to systemically administered therapeutic doses for specific compounds. However, we also observed a notable decrease in the probability of success when the predicted therapeutic dose exceeds 10mg. Additionally, our findings identified several critical factors affecting the success of ITM. These encompass both lower dissociation constants, higher systemic clearance and an optimum abundance of receptors in the target organ. Target tissues characterized by relatively low blood flow rates and high drug clearance capacities were deemed more conducive to successful ITM. These insights emphasize the necessity of taking into account each drug's unique pharmacokinetic and pharmacodynamic properties, along with the physiological characteristics of the target tissue, in determining the suitability of ITM.

Transit-time flowmetry measurement features of coronary bypass grafts after multiple percutaneous coronary interventions

The functionality of coronary bypass grafts after surgical myocardial revascularization in patients with coronary heart disease directly depends on the state of the target coronary arteries. In the presence of widespread and diff use atherosclerotic lesions or microcirculatory dysfunctions, a high frequency of coronary bypass dysfunctions is noted in the near future. In some cases, shunt dysfunction can lead to severe hemodynamic instability, accompanied by acute circulatory disorders.Aim: To assess the function of coronary bypass grafts during myocardial revascularization using the method of ultrasonic flowmetry in patients with and without a history of multiple percutaneous coronary interventions (PCI).Material and methods. The retrospective study included 47 patients who underwent coronary artery bypass surgery. A total of 145 coronary bypass grafts were performed. All patients were divided into 2 groups. Group 1 (PCI group) included patients after multiple previous PCI (n = 25; 74 coronary bypass grafts), group 2 (without PCI) included patients without previous PCI (n = 22; 71 coronary bypass grafts). All patients underwent intraoperative ultrasonic flowmetry of coronary bypass grafts using the VeriQ system (Medistim, Norway).Results. When analyzing the status of coronary bypass grafts in patients after multiple PCI, a significantly low mean volumetric blood flow rate was noted (29.5 ± 8.3 ml/min and 48.2 ± 11.6 ml/min, respectively, p = 0.0001) and lower diastolic filling (55.2 ± 8.2% and 71.9 ± 7.1%, p = 0.0001). Also in the group of patients after multiple PCI, there were 2 (2.7%) cases of revision of the distal anastomosis due to a high pulsatile index and low volumetric blood flow velocity. However, no such events were noted in the group without PCI.Conclusions. Previous percutaneous coronary interventions are compromising factors for the state of the coronary bed, which reduces the functional status of coronary bypass grafts and may increase the perioperative risk of surgical myocardial revascularization.

Safety and Metabolic Tolerance of Citrate Anticoagulation in Critically Ill Polytrauma Patients with Acute Kidney Injury Requiring an Early Continuous Kidney Replacement Therapy.

For severe polytrauma patients with an early AKI requiring renal replacement therapy, anticoagulation remains a great challenge. Due to a high bleeding risk, hemodynamic instability, and increased lactate levels, continuous modality (CKRT) and citrate anticoagulation seem to be the most appropriate. However, their safety with regard to the potential risk of impaired citrate metabolism is not documented. A retrospective study of 60 severe polytrauma patients admitted to the emergency department between January 2000 and December 2021 was conducted; the patients requiring CKRT during the first 72 h were treated with citrate (n. 46, group Citrate) or with heparin (n. 14, group Heparin). Out of 60 patients, 31 survived (51.7%). According to logistic regression analysis, age and SOFA score were significant predictors of mortality. The incidence of rhabdomyolysis was more common in the survivors (77.4 vs. 51.7%), and Kaplan-Meyer analysis showed a better trend towards survival at 90 days for the group Citrate than the group Heparin (p 0.0956). In the group Citrate, hemorrhagic episodes were significantly less common (0.045 vs. 0.273 episodes/day, p < 0.001); the effective duration (h/day) of CKRT was longer; and the effective net ultrafiltration rate (mL/kg/h) and blood flow rate were lower. For severe polytrauma patients, early, soft CKRT with citrate anticoagulation at a low blood flow rate and circuit citratemia showed a better safety and hemodynamic stability, suggesting that citrate should be the first choice anticoagulant in this subset of patients.

Hemodialysis through persistent left superior vena cava. Should it be used?

Background To describe a case of hemodialysis done through persistent left superior vena cava, identified incidentally after a left jugular central venous dialysis catheter insertion, and to discuss its feasibility. Case Summary Single case: A 66-year-old woman was admitted to the ICU with a diagnosis of septic shock, severe pneumonia, and acute renal failure. Hemodialysis was required for acute renal insufficiency. Persistent left superior vena cava (PLSVC) was detected on Chest x-ray after a left jugular central venous dialysis catheter placement. Hemodialysis was uneventful. Using a permanent dialysis catheter placed later through the PLSVC was less efficient. Although no complications were seen during hemodialysis, it was technically difficult (with high pressure in access and low blood flow rate). Conclusion Hemodialysis through PLSVC should remain an exceptional and short-term therapeutic alternative in dialysis patients.

Impact of needle type on substitution volume during online hemodiafiltration: plastic cannulae versus metal needles.

Plastic cannulae have attracted increasing interest as an alternative to traditional metal needles with the aim of reducing cannulation-related complications. We investigated whether the substitution volumes during hemodiafiltration differ using these two types of needles in dialysis patients. An intervention study involving 26 hemodialysis patients was conducted in Korea between March and September in 2021. Patients first received online hemodiafiltration using traditional metal needles, and thereafter plastic cannulae were used in a stepwise protocol. Repeated-measures design and linear mixed-effect models were used to compare substitution volumes between the two needle types with the same inner diameter. The mean patient age was 62.7 years, and their mean dialysis vintage was 95.2 months. Most patients (92.3%) had an arteriovenous fistula as the vascular access. The substitution volume increased as blood flow and needle size increased for both plastic cannulae and metal needles. The substitution volume was significantly higher with 17-gauge (G) plastic cannulae than with 16-G metal needles at blood flow rates of 280, 300, and 330 mL/min. Similar results were obtained for 15-G metal needles and 16-G plastic cannulae at a blood flow rate of 330 mL/min. However, the patient ratings of pain on a visual analogue scale were higher for plastic cannulae. Higher substitution volumes were obtained at the same prescribed blood flow rate with plastic cannulae than with metal needles during online hemodiafiltration. Plastic cannulae are an option for achieving high-volume hemodiafiltration for patients with low blood flow rates.

SYNCOPE DUE TO PRESSURE ON AV NODE DURING HEMODIALYSIS

TYPE: Case Report TOPIC: Cardiovascular Disease INTRODUCTION: Syncope in patients undergoing hemodialysis may happen due to many factors and is usually associated with an increased risk of cardiovascular disease and mortality. CASE PRESENTATION: A 79 y/o M with history of hypertension, hyperlipidemia, cerebrovascular disease, chronic kidney disease stage V not on RRT, was admitted due to painless hematuria and hyponatremia. Creatinine progressively worsened from 5.4 to 6.6 and BUN rose from 57 to 86, despite removal of clots from the bladder. A permacath was placed for hemodialysis (HD). During his first HD, within 10 minutes, the patient complained of dizziness and syncopized with tonic rigidity. Troponin was negative 2 hours later, and he was transferred to ICU. He tolerated the second session with a low blood flow rate. On his third HD, the patient had a similar episode, and telemetry showed an atrioventricular (AV) second degree Mobitz I block with bradycardia (HR 40-44) and a dropped beat. He denied chest pain in the peri-event period on both occasions. Troponins were negative 2 and 6 hours after the event, EKG was unremarkable. This was not consistent with acute coronary events. On chest X-ray the permacath tip was within the right atrium nearing the tricuspid valve. DISCUSSION: To the best of our knowledge there are no reported cases of syncope related to HD with a catheter placed close to the AV node. Higher blood flow rates produced elevated pressures on the AV node, which may have altered conduction contributing to our patient’s syncope. CONCLUSIONS: This case indicates the importance of proper permacath placement. DISCLOSURE: Nothing to declare. KEYWORD: syncope av node hemodialysis

Renal papillary necrosis in a transplanted kidney

Renal papillary necrosis (RPN) was first described in autopsy studies. The characteristic pathologic feature is selective coagulative necrosis of the inner medulla and papillae of the renal pyramids. This area of the renal parenchyma is vulnerable to ischaemic injury because its blood supply comes from narrow caliber vessels with low rates of blood flow. RPN represents the end-point of a number of conditions which compromise blood flow or increase metabolic demand in this vulnerable region. Diagnosis of RPN is typically made radiologically and operative management is not usually required.

Risks and Benefits of Ultra-Lung-Protective Invasive Mechanical Ventilation Strategies with a Focus on Extracorporeal Support.

Lung-protective ventilation strategies are the current standard of care for patients with acute respiratory distress syndrome in an effort to provide adequate ventilatory requirements while minimizing ventilator-induced lung injury. Some patients may benefit from ultra-lung-protective ventilation, a strategy that achieves lower airway pressures and Vt than the current standard. Specific physiological parameters beyond severity of hypoxemia, such as driving pressure and respiratory system elastance, may be predictive of those most likely to benefit. Because application of ultra-lung-protective ventilation is often limited by respiratory acidosis, extracorporeal membrane oxygenation or extracorporeal carbon dioxide removal, which remove carbon dioxide from blood, is an attractive option. These strategies are associated with hematological complications, especially when applied at low blood-flow rates with devices designed for higher blood flows, and a recent large randomized controlled trial failed to show a benefit from an extracorporeal carbon dioxide removal-facilitated ultra-lung-protective ventilation strategy. Only in patients with very severe forms of acute respiratory distress syndrome has the use of an ultra-lung-protective ventilation strategy-accomplished with extracorporeal membrane oxygenation-been suggested to have a favorable risk-to-benefit profile. In this critical care perspective, we address key areas of controversy related to ultra-lung-protective ventilation, including the trade-offs between minimizing ventilator-induced lung injury and the risks from strategies to achieve this added protection. In addition, we suggest which patients might benefit most from an ultra-lung-protective strategy and propose areas of future research.

Comparative efficacy between hemodialysis using super high-flux dialyzer with hemoperfusion and high-volume postdilution online hemodiafiltration in removing protein bound and middle molecule uremic toxins: A cross-over randomized controlled trial.

Hemodialysis (HD) using super high-flux dialyzer (HD+SHF) comparably removed uremic toxins to high-volume postdilution online hemodiafiltration (olHDF). Integration of hemoperfusion (HP) to HD+SHF (HD+SHF+HP) might provide superior uremic toxin removing capability to high-volume postdilution olHDF. The present study was conducted in thrice-a-week HD patients to compare the efficacy in removing indoxyl sulfate (IS), beta-2 microglobulin (β2 M), and urea between high-volume postdilution ol-HDF and HD+SHF+HP, comprising HD+SHF as the main treatment plus HD+SHF+HP 1/week in the first 4weeks and 1/2weeks in the second 4weeks. Ten prevalent HD patients with blood flow rate (BFR) above 400ml/min were randomized into two sequences of 8-week treatment periods of HD+SHF+HP and later high-volume postdilution olHDF or vice versa. When compared with high-volume postdilution olHDF (convective volume of 26.02±1.8 L/session), HD+SHF+HP provided comparable values of percentage reduction ratio of IS (52.0±11.7 vs. 56.3±7.5%, p=0.14) and β2 M (83.7±4.9 vs. 84.0±4.3%, p=0.37) and slightly lower urea reduction ratio. Despite greater dialysate albumin loss (p=0.008), there was no significant change in serum albumin level in HD+SHF+HP group. HD+SHF+HP could not provide superior efficacy in removing uremic toxins to high-volume postdilution olHDF. The use of low BFR of 200ml/min during the first 2h of HD+SHF+HP session, according to the instruction of manufacturer, might impair the efficacy of the HD+SHF part in removing uremic toxins.

Interrelation of cognitive functions and neural networks with blood flow velocity through the internal jugular vein in patients with chronic cerebral ischemia

Understanding age-related and functional changes in cerebral venous circulation is critical for the development of new preventive, diagnostic and therapeutic approaches to maintaining brain health in the elderly. Chronic cerebral ischemia is one of the widespread socially significant vascular diseases caused by a decrease in the level of blood circulation. To assess the role of venous outflow through the internal jugular veins in cognitive decline and neural networks in patients with chronic cerebral ischemia, 30 men and 40 women (average age 66.5 years), cognitive functions and organization of neural networks were studied at high and low levels of cerebral venous blood flow through the internal jugular veins. To assess the venous outflow, the systolic blood flow rate was measured by the internal jugular veins. A higher rate of venous outflow through internal jugular veins is associated with a more successful performance of the Luria test for verbal memory. A higher or lower blood flow rate affects the formation of neural networks of the brain. At a higher blood flow rate, the predominant areas of the resting neural networks (the passive mode network of the brain and the salient network) are localized in the frontal regions, at a low blood flow rate, the predominant neural network (frontal-parietal) is located in the left hemisphere. The state of faster and slower venous outflow forms neural networks using different neural formations that affect verbal memory. Reorganization of neural networks in this case, apparently, is the central mechanism responsible for cognitive decline in chronic cerebral ischemia (2 figs, 1 table, bibliography: 10 refs)

Microfluidic photoreactor to treat neonatal jaundice

While in most cases, jaundice can be effectively treated using phototherapy, severe cases require exchange transfusion, a relatively risky procedure in which the neonate's bilirubin-rich blood is replaced with donor blood. Here, we examine extracorporeal blood treatment in a microfluidic photoreactor as an alternative to exchange transfusion. This new treatment approach relies on the same principle as phototherapy but leverages microfluidics to speed up bilirubin removal. Our results demonstrate that high-intensity light at 470 nm can be used to rapidly reduce bilirubin levels without causing appreciable damage to DNA in blood cells. Light at 470 nm was more effective than light at 505 nm. Studies in Gunn rats show that photoreactor treatment for 4 h significantly reduces bilirubin levels, similar to the bilirubin reduction observed for exchange transfusion and on a similar time scale. Predictions for human neonates demonstrate that this new treatment approach is expected to exceed the performance of exchange transfusion using a low blood flow rate and priming volume, which will facilitate vascular access and improve safety.

The Role of Gray-Scale Ultrasound in the Diagnosis of Postnatal Testicular Torsion in Children

Testicular torsion is a severe variant of postnatal gonad pathology in children. The speed of development of irreversible ischemic disorders determines not only the medical, but also the social significance of the problem and determines the need for accurate and rapid diagnosis and prompt provision of adequate care to the patient. The only objective method for diagnosing testicular torsion in children is ultrasound. At the same time, the characteristics of the child’s body: the small size of the object of study, low rates of intratesticular blood flow and restless behavior during the study sharply reduce the diagnostic value of the Doppler study or make it technically impossible. Thus, seroshkal ultrasound is the first stage of diagnosis of this complex emergency pathology, based on the results of which it is possible to diagnose testicular torsion with great accuracy. The publication summarizes our own experience of 110 echographic observations of postnatal testicular torsion in children older than 2 months, all cases were verified intraoperatively. A quantitative method for estimating the deformity of a twisted testicle is proposed and its statistical reliability is proved. The options presented for gray-scale changes in the structure of damaged gonads and determined their prognostic significance. The publication contains a review of the literature and is extensively illustrated.

Membrane-based therapeutic plasma exchange: Hemodynamics and operational characteristics leading to procedure failure.

Therapeutic plasma exchange (TPE) is a blood purification treatment capable of removing large molecular weight substances from plasma. It is commonly used for the removal of circulating pathogenic immunoglobulins presumed to be the cause of many autoimmune diseases. TPE can be performed with a membrane-based system (mTPE) or a centrifugal-based system (cTPE). When plasma separation is performed with a membrane, filter clotting can lead to longer treatment time, higher cost and can negatively impact patient satisfaction. In this study, we examine the operational characteristics that might influence filter life. We report on 24 patients, with a total of 135 mTPE treatments in a single tertiary care academic center using the NxStage machine. The study focuses on treatment specific parameters that may lead to procedure failure. The main parameters of interest were transmembrane pressure (TMP) and the filtration fraction as displayed on the machine (FFd) compared to the calculated filtration fraction (FFc). Primary outcome was to measure whether TMP, FFc, and FFd influenced filter survival. Secondary outcomes included factors that might have indirectly resulted in filter failure, including hematocrit (Hct), platelet count, heparin use, and intra-treatment calcium administration. In this study, we demonstrated that machine displayed filtration fractions (FFd) were lower than FFc and this difference was significantly larger in TPE sessions that experienced a clotting event (7.58 vs 6.22, P=.031). TPE sessions that clotted had a higher mean TMP (57.48 mmHg vs 44.43 mmHg, P=.001) and clotting events tended to have a lower mean blood flow rate (175.83 mL/min vs 189.55 mL/min, P=.002). In TPE sessions that received prefilter calcium administration, a higher mean dose of calcium gluconate was found in the sessions that experienced clotting (3.27 g vs 2.70 g, P=.013). Patients who experienced at least one clotting event were noted to be heavier than those patients without any clotting events (91.52 kg vs 72.15 kg, P=.040). Prefilter heparin administration was not associated with a lower incidence of filter clotting. We did not find a statistically significant difference in clotting events based upon type of intravenous access, pretreatment hematocrit, or pretreatment platelet counts. Among patients undergoing mTPE, machine FFd on the NxStage system are consistently lower than FFc. Treatments where there was a greater difference between displayed and FFc had a greater likelihood of filter clotting. Treatments with higher TMP were associated with failed treatments. Prefilter calcium administration during treatment was associated with increased filter clotting. Lower blood flow rates and higher patient weight were also associated with increased filter clotting. Prefilter heparin administration did not reduce the incidence of filter clotting.

Characterization of the cylindrical electrospun nanofibrous polysulfone membrane for hemodialysis with modelling approach.

Electrospun nanofibrous membrane (ENM) is a membrane fabricated using electrospinning technique which has considerable characteristics such as high porosity, nanometer pore size, and simple process. Although ENMs are being evaluated in various medical applications, the effectiveness for hemodialysis (HD) has not been evaluated carefully. Thus, in this study, the cylindrical electrospun nanofibrous polysulfone (CENP) membrane was fabricated and its performance in the dialysis adequacy in HD patients was evaluated.The CENP membrane was fabricated in a tabular shape. The physical characteristics of the membrane are examined using scanning electron microscope (SEM) images and the permporometry technique. Then, its efficiency in urea and creatinine removal from the blood serum of 21 HD patients was evaluated at a low blood flow rate (BFR) of 200 ml min-1 and dialysate fluid rate (DFR) of 300 ml min-1. Afterwards, the results were modeled and optimized using artificial neural network (ANN) and genetic algorithm (GA), respectively. Finally, sensitive analysis was performed via Spearman's rank correlation coefficient. The highest dialysis adequacy was observed in membranes with an inner diameter of 3 mm. The CENP membrane belongs to the super high-flux membrane and it could be replaced with existing commercial hollow fiber membranes.

Retinal and choroidal blood flow variations after an endurance exercise: A real-life pilot study at the Paris Marathon

ObjectivesTo collect information about the retinal blood flow variations and other choroidal and retinal parameters during a prolonged effort such as marathon running. DesignNon-randomized prospective cohort study. MethodsPatients were recruited through an information campaign at the Rothschild Foundation Hospital (Paris, France). A first visit (V1) was planned in the month before the marathon. All participants underwent blood pressure measurement, fundus photography, spectral domain-optical coherence tomography (SD-OCT) and OCT-angiography (OCT-A). A second visit (V2) was scheduled within one hour of crossing the finish line. The same tests were repeated, using the same equipment. ResultsOf the 31 runners who were included, 29 finished the marathon and attended V2. At baseline, various ophthalmological abnormalities were found in 45.2% of the 58 eyes, among which almost a third concerned the optic nerve and a quarter the pachychoroid spectrum. A significant decrease in retinal vascular plexus density was found between V1 and V2 (p<0.01). While median macular and retinal nerve fiber layer (RNFL) thicknesses significantly increased after the marathon (p<0.01), median choroidal thickness significantly decreased (p<0.01). Both systolic and diastolic blood pressures significantly decreased (p<0.01 and p=0.021 respectively). ConclusionsProlonged physical effort impacts the structure and vascularization of the retina and the choroid. Hypoxia and dehydration due to such an effort may induce a low ocular blood flow rate resulting in a choroidal thinning, contrasting with a transient subclinical ischemic edema of the inner retina and optic nerve head. Clinical Trial Registration NumberNCT03864380.

Hemolysis at low blood flow rates: in-vitro and in-silico evaluation of a centrifugal blood pump

BackgroundTreating severe forms of the acute respiratory distress syndrome and cardiac failure, extracorporeal membrane oxygenation (ECMO) has become an established therapeutic option. Neonatal or pediatric patients receiving ECMO, and patients undergoing extracorporeal CO2 removal (ECCO2R) represent low-flow applications of the technology, requiring lower blood flow than conventional ECMO. Centrifugal blood pumps as a core element of modern ECMO therapy present favorable operating characteristics in the high blood flow range (4 L/min–8 L/min). However, during low-flow applications in the range of 0.5 L/min–2 L/min, adverse events such as increased hemolysis, platelet activation and bleeding complications are reported frequently.MethodsIn this study, the hemolysis of the centrifugal pump DP3 is evaluated both in vitro and in silico, comparing the low-flow operation at 1 L/min to the high-flow operation at 4 L/min.ResultsIncreased hemolysis occurs at low-flow, both in vitro and in silico. The in-vitro experiments present a sixfold higher relative increased hemolysis at low-flow. Compared to high-flow operation, a more than 3.5-fold increase in blood recirculation within the pump head can be observed in the low-flow range in silico.ConclusionsThis study highlights the underappreciated hemolysis in centrifugal pumps within the low-flow range, i.e. during pediatric ECMO or ECCO2R treatment. The in-vitro results of hemolysis and the in-silico computational fluid dynamic simulations of flow paths within the pumps raise awareness about blood damage that occurs when using centrifugal pumps at low-flow operating points. These findings underline the urgent need for a specific pump optimized for low-flow treatment. Due to the inherent problems of available centrifugal pumps in the low-flow range, clinicians should use the current centrifugal pumps with caution, alternatively other pumping principles such as positive displacement pumps may be discussed in the future.