Impact of anemia on acute ischemic stroke outcomes: A systematic review of the literature

INTRODUCTION: Anemia has been reported in nearly 40% of acute ischemic stroke (AIS) patients and is linked to significant morbidity and disability. The presence of anemia is associated with worse outcomes in AIS, specifically in the presence of large vessel occlusion (LVO). An optimal hemoglobin (Hb) target specific to this pathology has not yet been established. The goal of this review is to systematically review literature that observes the association that exists between AIS outcomes and hemoglobin (Hb) levels. METHODS: A systematic review was performed in accordance with guidelines for the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) to identify studies from 2008–2022. The following inclusion and exclusion criteria were used: studies of adult patients with AIS; must describe outcomes with regard to Hb levels in AIS (not limited to LVO); must be written in English. The clinical variables extracted included Length of Stay (LOS), modified rankin score (mRS), Hb levels, and mortality. RESULTS: A total of 1,154 studies were gathered, with 116 undergoing full text review. 31 studies were included in this review. The age of patients ranged from 61.4 to 77.8. The presence of anemia in AIS increased LOS by 1.7 days on average and these patients also have a 15.2% higher rate of mortality at one year, on average. DISCUSSION: This data suggests that the contemporary thresholds for treating anemia in AIS patients may be inadequate because anemia is strongly associated with poor outcomes (e.g., mRS>2 or mortality) and increased LOS in AIS patients. The current generalized Hb threshold for transfusion (7 g/dL) is also used in AIS patients, however, a more aggressive transfusion parameter should be further explored based on these findings. Further studies are required to confirm these findings and to determine if a more liberal RBCT threshold will result in clinical benefits.