Intracranial Hypertension and Cerebral Autoregulation: a Systemic Review and Meta-Analysis

Introduction: Refractory intracranial hypertension is one of the leading causes of morbidity and mortality in patients with acute neurological disease. In recent years, some authors have linked intracranial hypertension with impairment of cerebral blood flow autoregulation (CA), which is supposed to be trigger factor of high ICP. The objective of this paper is to present a systematic review and meta-analysis aiming to establish the relation between CA and intracranial hypertension.

Methods: An electronic search was designed to identify studies that analyzed CBF autoregulation in patients undergoing intracranial pressure (ICP) monitoring. The following search term was used: “Cerebral autoregulation and intracranial hypertension”. The inclusion criteria were as follows: 1) published manuscripts, 2) original articles of any design with prospective or retrospective data, 3) studies in adult patients, and 4) studies in which patients under invasive ICP monitoring were subjected to CA assessment. Data meta-analysis and sensitivity were performed.

Results: A static CA technique was applied in 10 studies (26.3%), a dynamic technique in 25 (65.8%) and both in 3 (7.9%). Static CA studies with cerebral blood flow technique revealed impaired CA in patients with ICP ≥ 20 (SMD 5.44%, 95% CI 0.25 to 10.65, p = 0.04); static CA studies with transcranial Doppler (TCD) revealed a tendency of impaired CA in patients with ICP ≥ 20 (SMD –7.83%, 95% CI –17.52 to 1.85, p = 0.11). Moving correlation CA studies reported impaired CA in patients with ICP ≥ 20 (SMD 0.06, 95% CI 0.07 to 0.14, p < 0.00001). Regarding the analysis, which compared CA values with mean ICP, it was clear that higher ICP was associated with impaired CA (SMD 5.47, 95% CI 1.39 to 10.1, p = 0.01). The probability of having impaired CA was elevated in patients with ICP ≥ 20 (OR 2.27, 95% CI 1.20 to 4.31, p = 0.01).

Conclusion: There is a clear tendency toward impairment of CA in patients with raised ICP. Future CA studies need standardize collection to provide more precise data concerning impaired CA and intracranial hypertension