Antiplatelet pretreatment does not increase hematoma volume in experimental intracerebral hemorrhage

Abstract

While oral anticoagulants are associated with greater hematoma expansion and higher mortality rates in patients with intracerebral hemorrhage (ICH), there is ongoing discussion whether pretreatment with antiplatelet drugs also worsens prognosis. Using an experimental model of ICH, we investigated the effects of antiplatelet pretreatment on hematoma volume and functional outcome. CD-1 mice were treated with acetyl-salicylic acid (ASA, 60 mg/kg per 24 hours), clopidogrel (22.5 mg/kg per 24 hours), or both (ASA+clopidogrel) through drinking water for 3 days (n=20 per group). Thereafter, platelet aggregation was found to be significantly reduced. Untreated mice and mice pretreated with warfarin served as controls. A stereotactic injection of collagenase into the right striatum was used to induce ICH. Twenty-four hours after ICH induction, hematoma volume was measured to be 15.0 ± 4.4 μL in controls, 14.1 ± 5.3 μL in ASA mice, 16.8 ± 5.1 μL in clopidogrel mice, and 16.4 ± 5.1 μL in ASA+clopidogrel animals. These differences were not statistically significant. However, mice pretreated with warfarin revealed largely increased hematoma volumes (25.0 ± 7.4 μL versus controls, P=0.001). Neurologic outcome was not different between antiplatelet-pretreated animals and untreated controls. Our results suggest that plasmatic coagulation rather than platelet function is the most critical element for preventing hematoma expansion in acute ICH. Future therapeutic strategies may take these findings into account.

Figure 1

Results of platelet aggregation testing. (A) Induction by arachidonic acid (500 μg/mL) for control mice, ASA mice, and ASA+CPG mice. (B) Induction by adenosine 5′-diphosphate (20 μmol/L) for control mice, CPG mice, and ASA+CPG mice (a total of 8 animals were tested per group). ASA, acetyl-salicylic acid; CPG, clopidogrel.

Figure 2

Tail-bleeding volumes measured by quantitative hemoglobin content determination in control mice, ASA mice, CPG mice, and ASA+CPG mice (n=11 per group). One-way ANOVA was used for comparison between treatment groups and controls. ^* Indicates significant difference. ANOVA, analysis of variance; ASA, acetyl-salicylic acid; CPG, clopidogrel.

Figure 3

Functional outcome. (A) Results of the hanging wire testing (% of attempts with three attempts per mouse). (B) Neurologic outcome as assessed on a 5-point scale for control mice, ASA mice, CPG mice, and ASA+CPG mice (% of animals, n=20 per group). Both for hanging wire testing and the neurologic scale, outcome was not different between groups. ASA, acetyl-salicylic acid; CPG, clopidogrel.

Figure 4

Hematoma volume determined 24 hours after hemorrhage induction by means of quantitative hemoglobin content determination for untreated control mice, ASA mice, CPG mice, and ASA+CPG mice (n=20 per group). Warfarin mice served as a positive control (n=4). One-way ANOVA revealed no differences between treatment groups (ASA, CPG, ASA+CPG) and controls. The t-test was used for comparison between warfarin mice and controls. ^* Indicates significant differences. ANOVA, analysis of variance; ASA, acetyl-salicylic acid; CPG, clopidogrel.