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The Association between Hematocrit and Mortality among Ischemic Stroke Patients

Sico JJ, Myers LJ, Ordin D, Williams LS, Bravata DM. The Association between Hematocrit and Mortality among Ischemic Stroke Patients. Paper presented at: American Heart Association Annual Scientific Sessions; 2012 Nov 5; Los Angeles, CA.




Abstract:

Introduction: Anemia is associated with higher mortality among patients with such non-stroke vascular conditions as heart failure and myocardial infarction. Less is known regarding the relationship between anemia and mortality among patients with acute ischemic stroke. Methods: Medical records were abstracted for a sample of 3965 veterans from 131 Veterans Health Administration (VHA) facilities who were admitted for a confirmed diagnosis of ischemic stroke (fiscal year 2007). Hematocrit (Hct) values from 24-hours of admission were categorized into 6-tiers ( 27%, 28-32%, 33-37%, 38-42%, 43-47%, 48%). We excluded patients with: female gender (n = 95), incomplete Hct data (n = 94), thrombolysis (n = 32), and inconsistent death dates (n = 6). We used multivariate logistic regression to examine the relationship between anemia and in-hospital, 30-day, 60-day and one-year mortality using multivariate logistic regression models for each time point, adjusting for age, NIHSS, comorbidity (including pneumonia), and Acute Physiology and Chronic Health Evaluation (APACHE)-III scores. The discrimination (c-statistics) and calibration (Hosmer-Lemeshow goodness of fit [HLGOF]) statistics were generated to gauge model performance and fit. Results: Approximately 2.1% of the N = 3750 patients presented with Hcts 27%, 6.2% were 28-32%, 17.9% were 33-37%, 36.4% were 38-42%, 28.2% were 43-47%, and 9.1% were 48%. Adjusted mortality odds at all time points were 2.5 to 3.5 times higher for those with Hct 27% (p values < 0.013 for in-hospital and 30-day mortality; p values at 6 months and one year were 0.002 and 0.001, respectively). Mortality risk at 6 months and 1 year showed a significant and dose-response relationship to Hct for all Hct groups < 38%. High Hcts were independently associated only with in-hospital mortality and only in those with Hct 48 (OR 2.9, p = 0.004). Models performed well across time points (C = 0.813, HLGOF = 0.9684 [in-hospital]; C = 0.832, HLGOF = 0.8186 [30-day]; C = 0.863, HLGOF = 0.7307 [60-day]; C = 0.880, HLGOF = 0.4313 [one-year]). Conclusions: Even a moderate level of anemia is independently associated with an increased risk of death during the first year following acute ischemic stroke. Very low or very high Hct is associated with early post-stroke mortality. Further work is required to evaluate whether interventions that treat anemia, its complications and underlying etiologies may also reduce post-stroke mortality.





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