Time-varying association between blood pressure and malignant brain edema after large hemispheric infarction: a prospective cohort study

To investigate the time-varying association between blood pressure (BP) and malignant brain edema (MBE) risk after large hemispheric infarction (LHI). We prospectively enrolled LHI patients (CT hypodensity > 1/3 middle cerebral artery territory within 6 h or > 1/2 within 6-48 h of onset) from registry cohort. BP was recorded hourly and analyzed for 24 h and in two 12-hour epochs after onset: 1-12 h and 13-24 h. MBE was defined as neurological deterioration symptoms with midline shift ≥ 5 mm. Generalized estimating equation (GEE) compared BP patterns by MBE occurrence. Logistic regression and restricted cubic splines (RCS) assessed dose-response associations. Among 414 included LHI patients (mean age 69 ± 14y, median onset-to-admission interval 3 h [interquartile range, IQR 2-5]), 117(28.3%) developed MBE with a median post-onset interval of 29 h (IQR 15-56). No significant difference in BP level was observed during 1-12 h. Systolic BP (SBP) was significantly higher in MBE group over time during 13-24 h (GEE P = 0.027). The 24-hour mean SBP exhibited a U-shaped association with MBE risk (nonlinear test, P = 0.029), with no significance in 1-12 h and a positive correlation between mean SBP in 13-24 h and MBE risk (aOR 1.02[1.00-1.04]). A threshold effect for 24-hour mean diastolic BP (DBP) was identified (non-linear test, P = 0.039), with DBP increase above 70 mmHg associated with higher MBE risk (aOR 1.03 [1.00-1.07]). Similarly, elevated mean DBP > 75mmHg during 1-12 h was associated with higher MBE risk. In LHI patients, 24-hour mean SBP demonstrated a U-shaped association with MBE risk, with no significant effect during 1-12 h and a positive linear correlation during 13-24 h after onset. DBP exhibited a threshold effect, primarily influencing MBE risk during 1-12 h after onset.