Impact of both ends of the hemoglobin range on clinical outcomes in acute ischemic stroke

Background and Purpose: Although both ends of the hemoglobin range may negatively influence clinical outcomes in acute ischemic stroke, most studies have examined the linear relationship or focused on the lower end of the range. Furthermore, it is unclear whether hemoglobin concentrations at different time points during hospitalization correlate with clinical outcomes in the same manner. Methods: We identified 2681 consecutive patients with acute ischemic stroke from a prospective stroke registry database and grouped them into hemoglobin concentration quintiles using the following 5 indices: initial, nadir, time-averaged, discharge hemoglobin, and hemoglobin drop. To examine the effect of both ends of hemoglobin range, the third quintile was selected as a reference category except for hemoglobin drop, for which the first quintile was used. As outcome variables, 3-month modified Rankin Scale as an ordinal scale and 3-month mortality were used. Results: With respect to higher modified Rankin Scale scores, the adjusted odds ratios and 95% confidence intervals of the first quintiles of initial, nadir, time-averaged, and discharge hemoglobin were 1.74 (1.31-2.31), 2.64 (2.09-3.33), 1.81 (1.42-2.30), and 1.65 (1.29-2.13), respectively. The opposite ends of these hemoglobin indices were not significantly associated. The adjusted odds ratio of the fifth quintile of hemoglobin drop (greatest hemoglobin drop) was 2.09 (1.51-2.89). The mortality analysis showed similar results except for initial hemoglobin. Conclusions: In acute ischemic stroke, poor outcome was related to the lower but not the higher end of the hemoglobin range, regardless of when and how hemoglobin concentrations were measured.