Moderate-to-Severe Anemia After Mechanical Thrombectomy Linked to Poorer Outcomes


Moderate-to-severe anemia decreased the likelihood of a favorable outcome after mechanical thrombectomy compared with no anemia.

Red blood cells | Image Credit: Vector8DIY/Pixabay

Credit: Vector8DIY/Pixabay

Moderate-to-severe anemia within 24 hours after mechanical thrombectomy for stroke was associated with a decreased likelihood of an advantageous outcome, according to new research.1

The data collected in the registry-based hospital cohort study showed the hemoglobin concentrations within 24 hours after macular thrombectomy had a better predictive capability than the hemoglobin concentration on admission and the ΔHb. Hemoglobin concentrations within 24 hours after mechanical thrombectomy were found to decrease with an increase in the number of device passes.

“Blood loss during the mechanical thrombectomy procedure might further worsen outcomes in patients with anemia on admission,” wrote the investigative team, led by Ryoma Inui, department of cerebrovascular medicine, National Cereberal and Cardiovascular Center. “In contrast, the predictive ability of the ΔHb for outcomes was moderate, which suggested that the effect of a decrease in hemoglobin concentrations was inconsistent among patients.”

Mechanical thrombectomy has improved outcomes for individuals with acute large vessel occlusion, but outcomes remain poor, with mortality a major risk after 3 months.2 Anemia is common on admission among patients with acute ischemic stroke, but prior evidence correlates moderate-to-severe anemia with poor functional outcomes after acute large vessel occlusion.

An aspiration maneuver of blood with thrombi is essential during the procedure, regardless of the thrombectomy strategy, and may reduce postoperative hemoglobin concentrations.1 Investigators noted a higher number of device passes may lead to lower postoperative hemoglobin concentrations, but the association between the procedure and postoperative anemia is unknown.1

As a result, Inui and colleagues hypothesized that anemia caused by the blood aspiration maneuver during each device pass worsens functional outcomes. Investigators retrospectively recruited consecutive patients who underwent mechanical thrombectomy as an endovascular revascularization procedure from January 2014 to April 2022. The mechanical thrombectomy procedures included stent receiver thrombectomy, contact aspiration, or a combined procedure.

Study participants were separated into three cohorts according to hemoglobin concentrations within 24 hours after mechanical thrombectomy, including no anemia (hemoglobin concentrations ≥13 g/dL for men and ≥12 g/dL for women), mild anemia (hemoglobin concentrations of 11–13 g/dL, and <10 g/dL, respectively), and moderate-to-severe anemia (hemoglobin concentrations <11 g/dL and <10 g/dL, respectively).

The ∆Hb was used to represent the change in hemoglobin concentrations within 24 hours after mechanical thrombectomy from the concentration on admission. At the 3-month mark, investigators evaluated a favorable outcome (modified Rankin Scale [mRS] score, 0–2), excellent outcome (mRS score of 0–1), favorable shift in the mRS score, and mortality in each study participant.

Inui and colleagues analyzed 470 patients (217 women, median age: 78 years), of which 168 (35.7%) patients had mild anemia and 136 (29%) patients had moderate-to-severe anemia after mechanical thrombectomy. Those in the moderate-to-severe anemia cohort were older, with a higher rate of female patients, and exhibited a more frequent history of comorbid congestive heart failure and stroke.

Investigators found hemoglobin concentrations after MT decreased with an increase in the number of device passes (P for trend <0.001). Upon multivariable analysis, moderate-to-severe anemia within 24 hours after the procedure was more frequent in the group with two device passes (adjusted odds ratio [OR], 3.45; 95% CI, 1.46 - 8.34), three device passes (adjusted OR, 7.21; 95% CI, 2.73 – 19.90), and ≥4 device passes (adjusted OR, 15.20; 95% CI, 6.07 – 41.10) than those with one device pass.

Further analyses showed the moderate-to-severe anemia group was less likely to have a favorable outcome versus the no-anemia group (aOR, 0.46; 95% CI, 0.26 - 0.81) independent of the baseline hemoglobin concentration. Using a restricted cubic spline model, investigators found the adjusted odds for a favorable outcome in patients were lower when hemoglobin concentrations were reduced within 24 hours after mechanical thrombectomy.

“The present result suggests the importance of being aware of blood loss during the mechanical thrombectomy procedure, especially in patients with anemia on admission,” Inui and colleagues wrote.


  1. Inui R, Koge J, Tanaka K, et al. Detrimental effect of anemia after mechanical thrombectomy on functional outcome in patients with ischemic stroke. Front Neurol. 2023;14:1299891. Published 2023 Dec 19. doi:10.3389/fneur.2023.1299891
  2. Fujiwara, S, Sakai, N, Imamura, H, Ohara, N, Tanaka, K, Yamagami, H, et al. Association between anemic status on admission and clinical outcomes of acute large vessel occlusion. J Neurol Sci. (2022) 440:120343. doi: 10.1016/j.jns.2022.120343
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