1474 Stroke June 2016 Methods Patient Selection

Intracerebral hemorrhage (ICH) is still the deadliest type of stroke and accounts for 10% to 20% of all cerebrovascular events. Hematoma expansion occurs in about one third of patients and is strongly associated with poor outcome. As a potentially modifiable determinant of ICH prognosis, hematoma expansion represents an appealing target for acute ICH treatment. The relationship between acute inflammation, white blood cell (WBC) count and ICH pathophysiology is complex. ICH is associated with leukocytosis, but the inflammatory activation represented by leukocytosis may, in turn, play a role in ICH severity. The results of multiple studies suggest that higher WBC counts accompany more severe ICH as measured by reduced consciousness, higher baseline hematoma volume, and intraventricular hemorrhage presence. Leukocyte count has also been associated with higher risk of early neurological deterioration, increased long-term mortality, and poor functional outcome. However, Di Napoli et al found that leukocytosis does not independently predict poor ICH prognosis when controlling for other outcome determinants including age, baseline hematoma volume, and admission Glasgow Coma Scale. Leukocytes interact with platelets, endothelium, and coagulation factors and have been widely recognized as important contributors to facilitating hemostasis in physiological and pathological conditions. Acute leukocytosis shifts the hemostatic balance in favor of coagulation and may therefore play an important role in the arrest of bleeding after an ICH occurs. To test the hypothesis that acute leukocytosis limits the extent of bleeding after acute ICH, we investigated whether acute leukocytosis reduced the risk of subsequent hematoma expansion. Background and Purpose—Acute leukocytosis is a well-established response to intracerebral hemorrhage (ICH). Leukocytes, because of their interaction with platelets and coagulation factors, may in turn play a role in hemostasis. We investigated whether admission leukocytosis was associated with reduced bleeding after acute ICH. Methods—Consecutive patients with primary ICH were prospectively collected from 1994 to 2015 and retrospectively analyzed. We included subjects with a follow-up computed tomographic scan available and automated complete white blood cell count performed within 48 hours from onset. Baseline and follow-up hematoma volumes were calculated with semiautomated software, and hematoma expansion was defined as volume increase >30% or 6 mL. The association between white blood cell count and ICH expansion was investigated with multivariate logistic regression. Results—A total of 1302 subjects met eligibility criteria (median age, 75 years; 55.8% men), of whom 207 (15.9%) experienced hematoma expansion. Higher leukocyte count on admission was associated with reduced risk of hematoma expansion (odds ratio for 1000 cells increase, 0.91; 95% confidence interval, 0.86–0.96; P=0.001). The risk of hematoma expansion was inversely associated with neutrophil count (odds ratio, 0.90; 95% confidence interval, 0.85–0.96; P=0.001) and directly associated with monocyte count (odds ratio, 2.71; 95% confidence interval, 1.08–6.83; P=0.034). There was no association between lymphocyte count and ICH expansion (odds ratio, 0.96; 95% confidence interval, 0.79–1.17; P=0.718). Conclusions—Higher admission white blood cell count is associated with lower risk of hematoma expansion. This highlights a potential role of the inflammatory response in modulating the coagulation cascade after acute ICH. (Stroke. 2016;47:1473-1478. DOI: 10.1161/STROKEAHA.116.013176.)