Abstract TMP81: Cerebral Blood Flow and Blood Pressure Reduction Do Not Affect Perihematomal Edema Growth in Acute Intracerebral Hemorrhage

Abstract

Background: Both vasogenic and cytotoxic (ischemic) processes have been postulated to play a role in perihematoma edema formation. In the Intracerebral Hemorrhage Acutely Decreasing Arterial Pressure Trial (ICH ADAPT), cerebral blood flow (CBF) was measured in ICH patients assigned to systolic blood pressure (SBP) targets of <150 or <180 mmHg. In this secondary analysis, we tested the hypotheses that edema growth is associated with reduced CBF and lower SBP. Methods: Non-contrast CT scans were obtained at baseline, 2h and 24h post-randomization. Mean relative CBF (rCBF) in the perihematoma region was calculated from raw CT Perfusion data obtained at 2h. Edema volume was measured using planimetric techniques and a Hounsfield unit threshold of ≤24 at baseline and 24h. Results: ICH patients were randomized (n=33 per group) at a median (IQR) of 7.6 (12.8) h after symptom onset. Mean SBP was significantly lower in the <150 mmHg (139±21 mmHg) than the <180 mmHg (163±11, p=<0.0001) at the time of CTP. Mean perihematoma rCBF in the <150 mmHg group (0.85±0.12) was similar to that in the <180 mmHg group (0.88±0.09, p=0.34). Treatment groups were balanced with respect to baseline SBP (180±18 vs. 185±25 mmHg, p=0.39) and acute ICH volume (20.7±22.0 vs. 28.0±25.8 ml, p=0.22). In all patients, median edema volume increased significantly between the baseline 1.8(2.5) ml and 24 h scans (3.1 (5.1) ml, p<0.0001). Linear regression indicated that ICH expansion predicted edema growth (β =0.3 [0.0, 0.2]). Lower perihematoma rCBF did not predict edema growth independently of ICH expansion (β =-0.2 [-229.5, 0.4]). Mean edema growth in the <150 group (2.4±6.9) was similar to that in the <180 group (2.9±6.4, p=0.737). Edema growth was not predicted by SBP change (β=0.12 [-0.45, 1.22]). Neither low SBP load (fraction of time SBP<150 mmHg over 24 h; β=0.07 [-0.13, 0.24]) nor high SBP load (time SBP >180 mmHg; β=0.07 [-0.13, 0.24]) predicted edema growth. Conclusion: Perihematoma edema growth is explained by ICH volume expansion. Lower perihematoma CBF and BP treatment do not exacerbate edema growth. These data are not consistent with a cytotoxic mechanism of edema formation and support the safety of early BP treatment.