Dynamic cerebral autoregulation after intracerebral hemorrhage: A case-control study

Abstract

Background: Dynamic cerebral autoregulation after intracerebral hemorrhage (ICH) remains poorly understood. We performed a case-control study to compare dynamic autoregulation between ICH patients and healthy controls.

Methods: Twenty-one patients (66 ± 15 years) with early (< 72 hours) lobar or basal ganglia ICH were prospectively studied and compared to twenty-three age-matched controls (65 ± 9 years). Continuous measures of mean flow velocity (MFV) in the middle cerebral artery and mean arterial blood pressure (MAP) were obtained over 5 min. Cerebrovascular resistance index (CVRi) was calculated as the ratio of MAP to MFV. Dynamic cerebral autoregulation was assessed using transfer function analysis of spontaneous MAP and MFV oscillations in the low (0.03-0.15 Hz) and high (0.15-0.5 Hz) frequency ranges.

Results: The ICH group demonstrated higher CVRi compared to controls (ipsilateral: 1.91 ± 1.01 mmHg·s·cm-1, p = 0.04; contralateral: 2.01 ± 1.24 mmHg·s·cm-1, p = 0.04; vs. control: 1.42 ± 0.45 mmHg·s·cm-1). The ICH group had higher gains than controls in the low (ipsilateral: 1.33 ± 0.58%/mmHg, p = 0.0005; contralateral: 1.47 ± 0.98%/mmHg, p = 0.004; vs. control: 0.82 ± 0.30%/mmHg) and high (ipsilateral: 2.11 ± 1.31%/mmHg, p < 0.0001; contralateral: 2.14 ± 1.49%/mmHg, p < 0.0001; vs. control: 0.66 ± 0.26%/mmHg) frequency ranges. The ICH group also had higher coherence in the contralateral hemisphere than the control (ICH contralateral: 0.53 ± 0.38, p = 0.02; vs. control: 0.38 ± 0.15) in the high frequency range.

Conclusions: Patients with ICH had higher gains in a wide range of frequency ranges compared to controls. These findings suggest that dynamic cerebral autoregulation may be less effective in the early days after ICH. Further study is needed to determine the relationship between hematoma size and severity of autoregulation impairment.

Figure 1

Cross-spectral function analysis for the ICH group and the control. Cross-spectral function analyses of the beat-to-beat mean arterial pressure and middle cerebral artery mean flow velocity in the 0.03-0.5 Hz ranges were used to determine the gain, coherence and phase values for the ICH group (ipsilateral and contralateral sides) and the control group.

Figure 2

Transfer function analysis for the ICH group and controls. Comparison of transfer function gain, coherence, and phase in the low (0.03-0.15 Hz) and high (0.15-0.5 Hz) frequency ranges between the ICH group (n = 21) and controls (n = 23). Values are expressed as mean (bar) ± SD (error bar). Ipsilateral and contralateral sides of the ICH group were compared to controls. Significant differences between the two groups are shown. *p < 0.01, **p < 0.001, ***p < 0.0001.

Figure 3

Relationship between hematoma size and transfer function gain in the ICH group. Within the ICH group (n = 21), correlation between hematoma size and transfer function gain at 0.03-0.15 Hz and 0.15-0.5 Hz frequency ranges are shown. Lines represent linear regression for ipsilateral (dashed lines) and contralateral (solid lines) hemisphere.