Patients with critical COVID-19 have a high risk of thromboembolism, but intensified thromboprophylaxis has not been proven beneficial. The activity of low-molecular-weight heparins can be monitored by measuring anti-Factor Xa. We aimed to study the association between anti-Factor Xa values and death, thromboembolism, and bleeding in patients with critical COVID-19. This retrospective cohort study included adult patients with critical COVID-19 admitted to an intensive care unit at three Swedish hospitals between March 2020 and May 2021 with at least one valid peak and/or trough anti-Factor Xa value. Within the peak and trough categories, patients’ minimum, median, and maximum values were determined. Logistic regressions with splines were used to assess associations. In total, 408 patients had at least one valid peak and/or trough anti-Factor Xa measurement, resulting in 153 patients with peak values and 300 patients with trough values. Lower peak values were associated with thromboembolism for patients’ minimum (p = 0.01), median (p = 0.005) and maximum (p = 0.001) values. No association was seen between peak values and death or bleeding. Higher trough values were associated with death for median (p = 0.03) and maximum (p = 0.002) values and with both bleeding (p = 0.01) and major bleeding (p = 0.02) for maximum values, but there were no associations with thromboembolism. Measuring anti-Factor Xa activity may be relevant for administrating low-molecular-weight heparin to patients with critical COVID-19. Lower peak values were associated with an increased risk of thromboembolism, and higher trough values were associated with an increased risk of death and bleeding. Prospective studies are needed to confirm the results. The study was retrospectively registered at Clinicaltrials.gov, NCT05256524, February 24, 2022.

中文翻译：

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一项关于抗 Xa 因子值与危重 COVID-19 患者死亡、血栓栓塞和出血之间关系的回顾性多中心队列研究

危重 COVID-19 患者发生血栓栓塞的风险很高，但强化血栓预防尚未被证明是有益的。低分子量肝素的活性可以通过测量抗 Xa 因子来监测。我们的目的是研究危重 COVID-19 患者的抗 Xa 因子值与死亡、血栓栓塞和出血之间的关联。这项回顾性队列研究包括 2020 年 3 月至 2021 年 5 月期间入住瑞典三家医院重症监护病房的危重 COVID-19 成年患者，这些患者至少有一个有效的抗 Xa 因子值峰值和/或谷值。在峰值和谷值类别中，确定患者的最小值、中值和最大值。使用样条的逻辑回归来评估关联性。总共，408 名患者具有至少一项有效的抗 Xa 因子测量峰值和/或谷值，导致 153 名患者具有峰值，300 名患者具有谷值。较低的峰值与患者的最小（p = 0.01）、中值（p = 0.005）和最大（p = 0.001）值的血栓栓塞相关。峰值与死亡或出血之间没有发现关联。较高的谷值与中位值 (p = 0.03) 和最大值 (p = 0.002) 的死亡相关，最大值与出血 (p = 0.01) 和大出血 (p = 0.02) 相关，但与血栓栓塞无关。测量抗 Xa 因子活性可能与向危重 COVID-19 患者施用低分子量肝素相关。较低的峰值与血栓栓塞风险增加相关，而较高的谷值与死亡和出血风险增加相关。需要进行前瞻性研究来证实结果。该研究于2022年2月24日在ClinicalTrials.gov上回顾性注册，NCT05256524。