The report, published in the Journal of Artificial Organs by Masayuki Kimura and colleagues at Harada Hospital in Hiroshima, describes two patients on long-term hemodialysis whose severe, treatment-refractory restless legs syndrome resolved after they were switched to postdilution online hemodiafiltration using a vitamin E-bonded polysulfone membrane. It is, according to the authors, the first published indication that this specific pairing of membrane and dilution mode may represent a new therapeutic option for the syndrome in dialysis patients.

Restless legs syndrome is one of the most burdensome non-dialysis-related complications of end-stage kidney disease. In the general population it affects a small minority of adults, but among patients on maintenance hemodialysis the prevalence rises steeply, and the symptoms tend to be more severe. The disorder is closely linked to disturbances of dopamine signaling and iron metabolism in the brain, which is why dopaminergic drugs such as pramipexole and anticonvulsants such as gabapentin are the usual pharmacological mainstays. Yet in dialysis patients these agents often provide only partial relief, and the underlying uremic environment, the accumulation of toxins that healthy kidneys would normally clear, is thought to keep fueling the problem.

That uremic link is where the new report begins. Previous research, including a 2015 study in Sleep Medicine, has associated restless legs syndrome in hemodialysis patients with oxidative stress and inflammation, suggesting that reactive molecules accumulating in the blood may aggravate the neurological symptoms. A separate line of work has focused on a specific protein called alpha1-microglobulin, a small glycoprotein that binds and neutralizes reactive free molecules in tissue. Because alpha1-microglobulin carries much of the body’s antioxidant defense burden, its accumulation in kidney failure is considered a marker of a pro-oxidant, inflammatory state. A large Japanese observational study, the JAMREDS protocol published in Blood Purification in 2024, is currently examining whether the rate at which dialysis removes alpha1-microglobulin relates to patient survival, underscoring how central this molecule has become to thinking about dialysis adequacy.

Kimura’s team approached the problem in stages. Both patients first received standard pharmacological therapy combined with high-efficiency online hemodiafiltration, a technique that pushes large volumes of replacement fluid across a highly permeable membrane to clear middle-sized uremic toxins more effectively than conventional hemodialysis. The team targeted an alpha1-microglobulin removal rate of at least 40 percent, a threshold associated in prior work with meaningful clearance of these middle molecules. Even with that level of removal achieved, the patients’ symptoms did not improve sufficiently.

The next step was to change the membrane itself. The vitamin E-bonded polysulfone dialyzer is a standard polysulfone filter with vitamin E chemically immobilized on its inner surface. Vitamin E is a lipid-soluble peroxyl radical scavenger, and during dialysis the blood repeatedly contacts artificial surfaces and oxygen-rich extracorporeal circuits that promote lipid peroxidation. A membrane bearing vitamin E can intercept these radical reactions at the blood-membrane interface, and clinical studies, including a systematic review and meta-analysis published in Blood Purification in 2017, have shown that vitamin E-coated membranes reduce markers of oxidative stress and inflammation compared with conventional membranes. Japanese researchers had earlier demonstrated that this membrane lowers a novel oxidative lipid marker in dialysis patients, and a randomized trial in Sleep Medicine found that oral vitamins C and E modestly improved restless legs symptoms in hemodialysis patients, providing a plausible mechanistic bridge between antioxidant therapy and symptom relief.

What happened next in the two cases is the most technically interesting part of the report. When the patients were placed on predilution online hemodiafiltration with the vitamin E membrane, in which replacement fluid is infused before the blood enters the filter, only limited improvement was observed. The team then switched to postdilution mode, infusing the replacement fluid after the blood has passed through the filter. In postdilution hemodiafiltration, the concentrated blood leaving the filter allows solute removal to be driven more directly by the high ultrafiltration rate, typically achieving superior clearance of middle molecules compared with predilution, although at the cost of requiring sufficient blood flow and hemoconcentration tolerance. After the switch, both patients experienced marked clinical benefit, with their restless legs syndrome resolving.

Curiously, the alpha1-microglobulin removal rates after the switch to postdilution mode fell below the 40 percent threshold that the team had previously targeted. This apparent paradox led the authors to an important interpretive conclusion: high-efficiency alpha1-microglobulin removal and the use of a vitamin E-bonded polysulfone membrane may contribute to improvement in restless legs syndrome through distinct mechanisms. In other words, simply clearing more of the marker protein is not the whole story. The antioxidant action of the membrane, and perhaps the way postdilution mode changes the dynamics of blood contact with the vitamin E surface, appears to matter independently of the measured removal rate.

The authors also emphasize that the beneficial effect of the vitamin E-bonded membrane may be affected by the dilution mode itself. In predilution, the incoming replacement fluid dilutes the blood before it contacts the membrane, reducing the concentration of solutes and potentially altering how oxidative reactions proceed at the blood-membrane interface. In postdilution, the blood is more concentrated as it traverses the filter, which may enhance the antioxidant interplay between the vitamin E surface and the lipid components of the blood. This mechanistic distinction, drawn from just two patients, remains a hypothesis, but it is a testable one that could reshape how clinicians configure hemodiafiltration for symptomatic dialysis patients.

The report comes with the usual caveats that attach to any two-case series. There is no control group, no blinding, and the possibility of placebo effects or natural symptom fluctuation cannot be excluded. The study was approved by an institutional review board and conducted with written informed consent from both patients, whose information was anonymized. The authors declare no conflicts of interest and received no specific funding for the work. Nonetheless, the clinical signal is striking: two patients with long-standing, drug-refractory symptoms achieved resolution after a specific technical intervention, and the pattern of improvement tracked the change in dilution mode rather than the measured clearance of a single marker protein. For a condition that affects a substantial fraction of the world’s roughly four million dialysis patients and that has few good options once first-line drugs fail, even a carefully documented two-case signal is worth pursuing. If larger controlled studies confirm that postdilution hemodiafiltration with a vitamin E-bonded polysulfone membrane relieves restless legs syndrome, a simple change in dialysis prescription, already available in many units, could offer relief to patients who have exhausted the pharmacological toolkit.

Subject of Research: Resolution of dialysis-associated restless legs syndrome using vitamin E-bonded membrane hemodiafiltration

Article Title: Resolution of restless legs syndrome after postdilution online hemodiafiltration using a vitamin E-bonded polysulfone membrane: a report of two cases

Article References: Kimura, M., Morita, N., Karasuda, K., Yamashita, K., & Doi, T. (2026). Resolution of restless legs syndrome after postdilution online hemodiafiltration using a vitamin E-bonded polysulfone membrane: a report of two cases. Journal of Artificial Organs, 29(4), Article 66. https://doi.org/10.1007/s10047-026-01596-1

Image Credits: AI Generated

DOI: 10.1007/s10047-026-01596-1

Keywords: restless legs syndrome, hemodiafiltration, vitamin E-bonded polysulfone membrane, oxidative stress, alpha1-microglobulin, hemodialysis, chronic kidney disease, postdilution mode, dopamine, dialysis membrane, case report, Journal of Artificial Organs

The Impella family of devices works by drawing blood from the left ventricle through an inlet area near the pump’s tip and expelling it into the ascending aorta, providing up to several liters per minute of forward flow while simultaneously unloading the failing ventricle. The pump motor and bearing assembly sit within the blood stream, and heat and mechanical stress make that region a nidus for thrombus formation. To prevent clot from accumulating around the motor, the device continuously flushes a sterile purge solution through the narrow clearance space between the rotor and the housing; the solution then exits into the circulation. Because this purge fluid is delivered directly into the patient’s blood, whatever is dissolved in it becomes part of the patient’s systemic drug exposure. Historically, the manufacturer’s instructions have called for heparin to be added to the purge solution, so the purge line acts as a continuous low-dose heparin infusion on top of whatever systemic anticoagulation the patient is already receiving.

That arrangement is straightforward when Impella is used alone, but it becomes genuinely complicated when ECMO is added. Patients on ECPELLA support are typically managed with systemic anticoagulation to protect the oxygenator and tubing of the extracorporeal circuit, guided by protocols such as those issued by the Extracorporeal Life Support Organization, whose 2021 adult and pediatric anticoagulation guidelines consolidated contemporary practice. Layering a heparin-containing purge on top of systemic heparin, or on top of an alternative agent such as bivalirudin, creates a second, parallel route of anticoagulant delivery whose contribution to the total dose is not independently measured by standard monitoring. Clinicians therefore face a balancing act: enough anticoagulation to protect two devices and a circuit, but not so much that bleeding, the most common complication of mechanical circulatory support, becomes life-threatening. Some centers have responded by removing heparin from the purge bag entirely, running the purge with anticoagulant-free solutions such as 5% dextrose in water or sodium bicarbonate, and relying on systemic anticoagulation to protect the pump.

The question is whether an anticoagulant-free purge actually protects the device. The purge flow rate is titrated to maintain a specified pressure gradient across the purge circuit, which serves as a proxy for patency of the tiny channels that bathe the motor; if those channels clot, purge pressure rises, the purge rate climbs to compensate, and in the worst case the pump malfunctions. Prior single-center experiences, including analyses of heparin 25 units per milliliter purge solutions and separate evaluations of bicarbonate-based purge solutions in patients with cardiogenic shock supported by Impella, have suggested that non-standard purge strategies can be workable, but the data remain limited and the patients most likely to receive ECPELLA, those in profound cardiogenic shock, have been underrepresented. The new study by Nathaniel J. Martin, Christoph G. S. Nabzdyk, Scott D. Nei, Andrew N. Rosenbaum, Troy G. Seelhammer, and Patrick M. Wieruszewski was designed to examine exactly this gap: Impella device function in patients receiving combined ECMO and Impella support, stratified by whether their purge solution contained heparin or not.

The design was observational and modest in scale, and the authors are explicit about its limits. The team identified 25 patients supported with ECPELLA at their institution. Fourteen of these patients received an anticoagulant-free purge solution, either 5% dextrose or sodium bicarbonate, while the remaining 11 received a heparin-containing purge solution. The median duration of ECPELLA support was five days, a duration long enough for purge-related thrombosis to become clinically apparent if it were going to occur. The primary observation of interest was Impella device malfunction attributable to purge failure, the outcome that would most directly signal that an anticoagulant-free purge was inadequate to keep the motor housing clear. Ethical approval for the study came from the Mayo Clinic Institutional Review Board, with a waiver of informed consent, consistent with the retrospective review of clinical care.

The headline finding is stark in its simplicity. Across the entire cohort, the only episode of Impella device malfunction occurred in a patient in the heparin-containing group. No patient in the anticoagulant-free group experienced a purge-related device failure during their course of support, and device longevity appeared acceptable in both groups. Read at face value, the result suggests that dextrose- or bicarbonate-based purge solutions, paired with systemic anticoagulation, did not compromise the mechanical integrity of the Impella during a median of five days of combined support. In an environment where every additional unit of heparin delivered through the purge line potentially shifts a critically ill patient’s hemostatic balance, a strategy that removes that infusion without evident device harm is clinically meaningful, even if the evidence behind it is still thin.

The authors themselves are careful not to overstate the case, and their caution is warranted for reasons that go to the heart of how small clinical studies work. With only 25 patients and a low overall event rate, the study cannot exclude a modest increase in device malfunction risk associated with anticoagulant-free purge solutions; the single malfunction in the heparin group, far from indicting heparin, illustrates precisely how noisy such comparisons are at this scale. Bleeding outcomes, thromboembolic events, and hemolysis, all of which matter enormously in this population, are not the focus of the abstract-level reporting, and confounding by indication is a live concern: the choice of purge solution likely reflected evolving institutional practice and individual patient characteristics rather than random assignment. The conclusion the authors draw is correspondingly measured. Given the low event rate and the apparent maintenance of acceptable device longevity, they write, use of anticoagulant-free purge solutions alongside systemic anticoagulation in ECPELLA patients may be reasonable, but the strategy requires validation in an appropriately powered study.

Even so, the study contributes to a broader and increasingly visible conversation about how anticoagulation should be managed across the growing arsenal of temporary circulatory support devices. Pharmacotherapy reviews have called for optimization of anticoagulation in Impella-supported patients, noting the tension between manufacturer recommendations, center-specific protocols, and the absence of definitive trial evidence. Comparisons of bivalirudin versus heparin for systemic anticoagulation during ECMO, published in Critical Care Medicine by members of the same Mayo group, reflect the same underlying effort to rationalize hemostatic management in extracorporeal support. The purge solution sits at an unusual intersection within this landscape: it is simultaneously a device-maintenance fluid and a systemic drug delivery route, and it is frequently overlooked in discussions that focus on the more visible systemic anticoagulants. Recognizing the purge line as a pharmacologic exposure, and studying it as one, is a conceptual step forward for the field.

For the bedside intensivist, pharmacist, and perfusionist managing an ECPELLA patient tonight, the practical takeaway is not a new protocol but a new data point in an evolving conversation. Anticoagulant-free purge solutions, whether 5% dextrose or sodium bicarbonate, have now been used in a consecutive series of ECPELLA patients at a high-volume center without evident compromise of device function over a median of five days of support. That observation will not end the debate, and no one should abandon heparinized purge on the strength of 25 patients, but it legitimizes the strategy as a subject for the large, prospectively designed comparative study it deserves. Until such a study exists, the choice of purge solution will remain a matter of institutional protocol and clinical judgment, exercised within the same delicate balance that defines all of extracorporeal support: keeping the blood fluid enough to survive the machine, and the patient solid enough to survive the bleeding. This small study suggests the balance can be struck without heparin in the purge bag, and that alone makes it worth the field’s attention.

Subject of Research: Impella purge solution strategy and device function in patients receiving combined ECMO and Impella (ECPELLA) support

Article Title: Impella purge solutions in patients receiving extracorporeal membrane oxygenation

Article References: Martin, N. J., Nabzdyk, C. G. S., Nei, S. D., Rosenbaum, A. N., Seelhammer, T. G., & Wieruszewski, P. M. (2026). Impella purge solutions in patients receiving extracorporeal membrane oxygenation. Journal of Artificial Organs, 29(4), Article 64. https://doi.org/10.1007/s10047-026-01595-2

Image Credits: AI Generated

DOI: 10.1007/s10047-026-01595-2

Keywords: Impella, ECMO, ECPELLA, purge solution, anticoagulation, heparin, mechanical circulatory support, cardiogenic shock, left ventricular unloading, device malfunction, critical care, ventricular assist device

The clinical picture on presentation was dire. Acute severe mitral regurgitation had produced extreme respiratory failure despite maximal ventilatory support: while breathing pure oxygen, the patient’s arterial blood showed a pH of 7.144, a partial pressure of oxygen of only 48 mmHg, and a partial pressure of carbon dioxide of 101 mmHg. Those numbers describe profound, life-threatening hypoxemia and hypercapnia, the biochemical signature of lungs so waterlogged and failing that gas exchange had nearly collapsed. Fulminant pulmonary edema of this kind, driven by the sudden backflow of blood through an incompetent mitral valve, typically leaves clinicians with a narrow and dangerous window in which to act.

The standard emergency answer for such patients is often veno-arterial ECMO, in which blood is drained from the venous system, oxygenated outside the body, and returned to the arterial circulation, simultaneously supporting the heart and lungs. But the authors highlight a well-recognized paradox: VA-ECMO can worsen pulmonary congestion in patients with a failing left ventricle. By returning oxygenated blood to the aorta, it increases the afterload against which the damaged left ventricle must pump, which can push blood backward into the lungs and aggravate the very edema the therapy is meant to buy time against. Recent literature, including a 2024 position paper on dual-circulation physiology during venoarterial ECMO and multicenter data linking left ventricular unloading to lower mortality in cardiogenic shock, has sharpened attention on this problem and on strategies to relieve the loaded ventricle.

The surgical team proceeded with emergency mitral valve replacement under cardiopulmonary bypass. When the operation ended, however, the heart could not be weaned from the bypass machine: severe pulmonary edema and post-cardiotomy shock conspired to keep the ventricle too weak and the lungs too compromised for independent circulation. Rather than defaulting to VA-ECMO, the surgeons made a deliberate split decision. They implanted an Impella 5.5, an axial-flow catheter-mounted pump, directly into the ascending aorta through a prosthetic graft, positioning it across the aortic valve so it could draw blood out of the left ventricle and deliver it antegrade into the systemic circulation. Then they added veno-venous ECMO, which drains deoxygenated blood from the venous side and returns it oxygenated to the veins, supporting only the lungs.

The physiological logic of this combination is what makes the case compelling. The Impella 5.5 provides left ventricular unloading and forward systemic flow, reducing the pressure that would otherwise be transmitted back into the pulmonary vasculature, while VV-ECMO takes over gas exchange without adding any arterial afterload at all. In effect, the circulation and the respiration were decoupled and managed independently, avoiding the differential hypoxemia problem known as harlequin syndrome, in which poorly oxygenated blood ejected by the native heart mixes with oxygenated ECMO return in patients on VA-ECMO. The authors argue that this decoupled strategy may be an effective option for selected patients suffering concomitant severe respiratory and circulatory failure, particularly when VA-ECMO risks compounding pulmonary congestion.

The early postoperative course was rocky but revealing. The patient initially required substantial vasoactive and inotropic drug support to maintain blood pressure, a reflection of both the stunned post-cardiotomy myocardium and the inflammatory burden of prolonged critical illness. Serum lactate, a biochemical marker of inadequate tissue perfusion, peaked transiently at 10.9 mmol/L on postoperative day one, a level indicating significant anaerobic metabolism. Crucially, however, systemic perfusion was maintained throughout, and as the ventricle recovered, the team was able to stabilize the circulation on Impella-mediated antegrade flow alone, without ever converting to VA-ECMO or the hybrid V-AV configuration that many centers would have reached for in a similar situation.

Respiratory recovery followed a parallel and equally instructive trajectory. Under VV-ECMO-supported lung rest, with the membrane lung shouldering the work of oxygenation and carbon dioxide removal, and under an intensive diuretic regimen to strip away the excess lung water, the patient’s respiratory function improved progressively. Bilateral pulmonary opacities on imaging, the radiographic shadow of the edema, gradually cleared. VV-ECMO was removed on postoperative day three, a remarkably short run that suggests the lung injury, while fulminant, was largely hydrostatic and reversible once the circulatory derangement was corrected. The Impella 5.5 was explanted on postoperative day six as ventricular function recovered.

The outcome was a full survival: the patient was discharged on postoperative day 46 without any neurological sequelae, an outcome that would have been considered improbable at the moment of presentation, when his blood gases were incompatible with sustained life on conventional support. For a case report, the message is less about a single heroic save than about a reproducible physiological principle. The authors position the combination as a way to sidestep the afterload penalty of VA-ECMO while still providing both pump function and gas exchange, drawing on established techniques for direct aortic Impella implantation that allow the device to be placed surgically with secure fixation.

The report also underscores how rapidly the mechanical support landscape is evolving. The Impella 5.5, originally developed as a percutaneous left ventricular assist device for high-risk procedures and cardiogenic shock, is increasingly being combined with ECMO in creative configurations, and the literature now includes dedicated analyses of left ventricular decompression during VA-ECMO and reviews of the collision between native and device circulations. This case adds a new entry to that growing repertoire: instead of adding an Impella to unload a ventricle already supported by VA-ECMO, the team used the pump as the sole circulatory engine and paired it with purely respiratory extracorporeal support. The authors are careful to frame the approach as appropriate for selected patients, and a single case cannot establish superiority over conventional strategies. But for clinicians confronting the double failure of heart and lungs, particularly when pulmonary edema makes VA-ECMO counterproductive, the case provides a concrete, technically documented template. It suggests that thinking about circulatory and respiratory failure as separable problems, rather than as a single indication for one device, can turn a nearly certain death into a discharge home with an intact brain.

Subject of Research: Combined veno-venous ECMO and direct aortic Impella 5.5 support for emergency mitral valve replacement in acute severe mitral regurgitation with fulminant pulmonary edema

Article Title: Combined veno-venous ECMO and direct aortic impella 5.5 support enabling emergency mitral valve replacement in acute severe mitral regurgitation with fulminant pulmonary edema

Article References: Combined veno-venous ECMO and direct aortic impella 5.5 support enabling emergency mitral valve replacement in acute severe mitral regurgitation with fulminant pulmonary edema. (n.d.). https://doi.org/10.1007/s10047-026-01592-5

Image Credits: AI Generated

DOI: 10.1007/s10047-026-01592-5

Keywords: veno-venous ECMO, Impella 5.5, mechanical circulatory support, left ventricular unloading, differential hypoxemia, mitral regurgitation, pulmonary edema, cardiogenic shock, mitral valve replacement, cardiac surgery, Journal of Artificial Organs, case report

The letter, authored by Barina Khan of Karachi Medical and Dental College and published on 3 September 2026 as Volume 29, article number 59 of the journal, is written in direct response to a pilot study by Tran and colleagues that documented dynamic platelet dysfunction in patients undergoing extracorporeal membrane oxygenation. That pilot work, which appeared in the same journal earlier in 2026, used platelet function testing to follow how platelet performance changed over the course of ECMO support and explored whether those changes tracked with clinically significant bleeding. The new letter does not dispute that platelet dysfunction is real and important in ECMO patients. Instead, it questions whether the specific instrument and protocol used can reliably detect it in this population.

The core of the concern lies in what laboratory scientists call a ceiling effect. The PFA-200 measures the time it takes for platelets, under controlled high shear conditions, to form a plug that occludes a microscopic aperture in a cartridge coated with platelet agonists such as collagen and epinephrine or collagen and adenosine diphosphate. When platelet function is severely impaired, the plug simply never forms, and the instrument reports a result at or above the maximum assay limit, typically a value greater than 300 seconds. In profoundly thrombocytopenic or platelet-exhausted patients, which many ECMO patients quickly become, large numbers of test results pile up at this artificial ceiling. Once a value has been censored at the upper limit, the assay can no longer distinguish between moderately severe and catastrophic platelet failure, compressing exactly the range of dysfunction that matters most for predicting bleeding.

Khan’s letter argues that this censoring problem is particularly acute during ECMO, where platelet counts fall progressively, platelets become activated and exhausted through continuous contact with the oxygenator membrane and circuit tubing, and acquired platelet defects accumulate over days of support. If a study correlates closure times with bleeding episodes in such a cohort, the relationship may be flattened or distorted by the many results that read simply as greater than 300 seconds. Statistical associations computed on censored data risk either underestimating the true strength of the link between platelet failure and hemorrhage or, depending on how the ceiling values are handled in the analysis, producing misleading conclusions about when platelet dysfunction begins to matter clinically.

The second confounder the letter highlights is hematocrit, the proportion of blood volume occupied by red blood cells. It is a long-standing observation in hematology that the PFA-100 and PFA-200 are exquisitely sensitive to the hematocrit of the sample. Red cells are not passive bystanders in primary hemostasis; they physically push platelets toward the vessel wall in flowing blood and contribute chemical signals, including adenosine diphosphate released from erythrocytes, that amplify platelet activation. When the hematocrit drops below roughly 30 percent, closure times lengthen even if platelets themselves are functioning normally, and severe anemia can push closure times beyond the assay limit on its own. Conversely, elevating the hematocrit can shorten closure times and mask genuine platelet defects, an effect documented decades ago in studies of uremic and cirrhotic patients evaluated on the platelet function analyzer.

This sensitivity is a serious problem in the ECMO population specifically. Patients on extracorporeal support are frequently anemic, whether from hemodilution caused by circuit priming, hemolysis within the circuit, repeated blood sampling, gastrointestinal bleeding, or the suppressed red cell production that accompanies critical illness. In such patients, a prolonged closure time may reflect the red cell deficit rather than intrinsic platelet failure, and the degree of prolongation may bear little relationship to the true functional capacity of the platelets. Khan’s letter suggests that unless hematocrit is either matched across study groups or formally adjusted for in the statistical model, the association reported between PFA-200 closure times and bleeding in ECMO patients may be confounded from the outset, with anemia masquerading as platelet dysfunction.

The letter places these concerns in a broader and somewhat sobering context. The clinical utility of closure times on the platelet function analyzer has been debated for more than two decades. Studies in cardiac surgery patients have repeatedly questioned whether the device predicts blood loss after cardiopulmonary bypass, another setting in which acquired platelet defects, hemodilution and anemia coexist. A comprehensive review in the American Journal of Hematology catalogued the assay’s utility across bleeding disorders while also documenting its susceptibility to hematologic variables, and a worldwide survey of platelet function testing practices conducted under the auspices of the International Society on Thrombosis and Haemostasis underscored how much variability exists in how platelet function is assessed even among expert laboratories. Against that backdrop, applying the PFA-200 to the uniquely harsh environment of extracorporeal circulation demands particular caution about the assay’s known limitations.

None of this means the assay should be abandoned in the ECMO setting, the letter’s argument implies, but rather that its results must be interpreted with an awareness of when the instrument can and cannot see. Practical strategies exist. Researchers can report the proportion of censored results explicitly and use statistical methods designed for data with detection limits rather than treating the ceiling value as a genuine number. Studies can stratify closure times by hematocrit, exclude samples with severe anemia from platelet-focused analyses, or measure closure times only after red cell transfusion has stabilized the hematocrit. Complementary tests that are less dependent on shear, hematocrit and sample handling, such as light transmission aggregometry, flow cytometric markers of platelet activation, or other point-of-care viscoelastic and platelet-mapping devices, can help triangulate the true state of platelet function. The pilot study’s central observation, that platelet dysfunction evolves dynamically during ECMO, remains valuable; the question is whether the PFA-200, as deployed, is measuring that dysfunction or partly measuring the anemia around it.

The stakes are far from academic. Bleeding remains one of the most feared complications of ECMO, occurring in a substantial fraction of patients and driving decisions about anticoagulation intensity, transfusion thresholds and circuit management. If closure times on the PFA-200 are adopted as a bedside guide without accounting for ceiling effects and hematocrit, clinicians risk both false reassurance, when an apparently normal result is actually capped by the assay limit in a patient with profound platelet exhaustion, and false alarm, when a prolonged result in an anemic patient triggers unnecessary platelet transfusion. Given that platelet transfusions carry their own risks, including allergic reactions, transfusion-associated circulatory overload and the theoretical promotion of thrombosis in a patient group already prone to circuit clotting, refining which patients truly need platelet support is a matter of real clinical consequence.

Khan’s letter is a compact methodological intervention, but it lands at a moment when interest in platelet function testing during extracorporeal support is growing rapidly. As devices for measuring closure times, aggregometry and platelet activation migrate from hematology laboratories to the intensive care unit bedside, the letter serves as a reminder that the validity of any such measurement depends on the biology of the sample as much as the precision of the instrument. In ECMO patients, where thrombocytopenia, platelet exhaustion and anemia march together, closure times must be read with both eyes open. Whether future studies can confirm a robust, hematocrit-independent association between PFA-200 results and bleeding in this population will determine whether the assay earns a genuine place in the ECMO management toolkit, or remains a test whose ceiling it cannot see above and whose red cell context it cannot escape.

Subject of Research: The reliability of PFA-200 platelet function closure times for assessing bleeding risk during extracorporeal membrane oxygenation

Article Title: PFA-200 closure times in ECMO: Are ceiling effects and hematocrit confounding the bleeding association?

Article References: Khan, B. (2026). PFA-200 closure times in ECMO: Are ceiling effects and hematocrit confounding the bleeding association?. Journal of Artificial Organs, 29(4), Article 59. https://doi.org/10.1007/s10047-026-01589-0

Image Credits: AI Generated

DOI: 10.1007/s10047-026-01589-0

Keywords: ECMO, PFA-200, platelet function, closure time, bleeding risk, hematocrit, coagulation, extracorporeal membrane oxygenation, platelet dysfunction, anemia, point-of-care testing, Journal of Artificial Organs