High Incidence of Circuit Clotting in Critically Ill COVID-19 Patients Treated with Renal Replacement Therapy : Journal of the American Society of Nephrology

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High Incidence of Circuit Clotting in Critically Ill COVID-19 Patients Treated with Renal Replacement Therapy

Grenon, Eloïse1; Canet, Emmanuel2

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JASN 32(7):p 1823-1824, July 2021. | DOI: 10.1681/ASN.2021040528
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We read, with great interest, the study by Gupta et al.1 on the risk factors and outcomes of patients critically ill with coronavirus disease 2019 (COVID-19) who developed AKI and were treated with RRT. They found AKI is frequent in patients with COVID-19, and that RRT is associated with high mortality. On the basis of our experience, we would like to draw attention to the clinical relevance of circuit clotting, a feature not addressed by Gupta et al. Indeed, hypercoagulability is a common problem in patients with COVID-19, and is associated with a high risk of deep venous thrombosis and pulmonary embolism.2,3 In our center, 30.5% of patients critically ill with COVID-19, who were admitted during the first wave of the COVID-19 pandemic, required RRT. Among 130 RRT sessions performed in 20 patients, circuit clotting or catheter thrombosis occurred in 21% of RRT sessions, leading to premature termination of the session. These thrombotic events occurred despite prophylactic anticoagulation with systemic heparin (40%), systemic and prefilter heparin (35%), or prefilter heparin (25%). We compared patients with COVID-19 with a control group of 20 critically ill patients without COVID-19 who underwent 130 RRT sessions in our intensive care unit within 6 months before the onset of the COVID-19 pandemic. Patients were matched for age, comorbidities, severity scores, need for mechanical ventilation and vasopressors, and anticoagulation regimen. We found that the incidence of thrombotic events of patients with COVID-19 during RRT sessions was four times that of patients without COVID-19 (21% versus 4.1%, P=0.003). Moreover, laboratory analyses revealed significant differences in coagulation parameters. Patients with COVID-19 displayed a higher level of fibrinogen (9.05 versus 6.6 g/L, P=0.0004) and platelet count (364 versus 194 g/L, P=0.008), and a lower level of D-dimers (1274 versus 14,814 ng/ml, P=0.02) compared with patients without COVID-19.

Our results are similar to those reported by Shankaranarayanan et al.4 They analyzed 203 circuits and found a 40% incidence of premature clotting on various anticoagulation regimens. We aim to raise the awareness of intensive-care-unit physicians who manage patients with COVID-19 and severe AKI on the high incidence of thrombotic events during RRT. We hypothesize that repeated loss of RRT circuits may have contributed to significant blood loss and the delivery of a low intensity of therapy. Such adverse events can play a significant role in increasing RRT-related morbidity and mortality in patients with COVID-19. Further studies are needed to assess whether the optimization of anticoagulation can translate into improved management of RRT and better patient outcomes.

Ethics Approval and Consent To Participate

The study was performed in accordance with Good Clinical Practice and Declaration of Helsinki principles for ethical research. This retrospective study was approved by the ethics committee of the French Intensive Care Society (CE SRLF 21-07) on February 11, 2021.


E. Canet reports receiving fees from Baxter, Gilead, and Sanofi Genzyme for lectures, conference talks, and travel and accommodation expenses. The remaining author has nothing to disclose.



Published online ahead of print. Publication date available at www.jasn.org.

See related original article, “AKI Treated with Renal Replacement Therapy in Critically Ill Patients with COVID-19,” in Vol. 32, Iss. 1, on pages .

E. Grenon and E. Canet designed the study, wrote the manuscript, and performed the statistical analysis.

Data Sharing Statement

The datasets used and/or analyzed during this study are available from the corresponding author on reasonable request.


1. Gupta S, Coca SG, Chan L, Melamed ML, Brenner SK, Hayek SS, et al.; STOP-COVID Investigators: AKI treated with renal replacement therapy in critically ill patients with COVID-19. J Am Soc Nephrol 32: 161–176, 2021
2. Tang N, Bai H, Chen X, Gong J, Li D, Sun Z: Anticoagulant treatment is associated with decreased mortality in severe coronavirus disease 2019 patients with coagulopathy. J Thromb Haemost 18: 1094–1099, 2020
3. Klok FA, Kruip MJHA, van der Meer NJM, Arbous MS, Gommers DAMPJ, Kant KM, et al.: Incidence of thrombotic complications in critically ill ICU patients with COVID-19. Thromb Res 191: 145–147, 2020
4. Shankaranarayanan D, Muthukumar T, Barbar T, Bhasin A, Gerardine S, Lamba P, et al.: Anticoagulation strategies and filter life in COVID-19 patients receiving continuous renal replacement therapy: A single-center experience. Clin J Am Soc Nephrol 16: 124–126, 2020

COVID-19; renal replacement therapy; circuit clotting; intensive care unit; acute kidney injury

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