Cerebrovascular tone and resistance measures differ between healthy control and patients with acute intracerebral haemorrhage: exploratory analyses from the BREATHE-ICH study

Abstract

Objective. Cerebral autoregulation impairment in acute neurovascular disease is well described. The recent BREATHE-ICH study demonstrated improvements in dynamic cerebral autoregulation, by hypocapnia generated by hyperventilation, in the acute period following intracranial haemorrhage (ICH). This exploratory analysis of the BREATHE-ICH dataset aims to examine the differences in hypocapnic responses between healthy controls and patients with ICH, and determine whether haemodynamic indices differ between baseline and hypocapnic states. Approach. Acute ICH patients were recruited within 48 h of onset and healthy volunteers were recruited from a university setting. Transcranial Doppler measurements of the middle cerebral artery were obtained at baseline and then a hyperventilation intervention was used to induce hypocapnia. Patients with ICH were then followed up at 10–14 D post-event for repeated measurements. Main results. Data from 43 healthy controls and 12 patients with acute ICH met the criteria for statistical analysis. In both normocapnic and hypocapnic conditions, significantly higher critical closing pressure and resistance area product were observed in patients with ICH. Furthermore, critical closing pressure changes were observed to be sustained at 10–14 D follow up. During both the normocapnic and hypocapnic states, reduced autoregulation index was observed bilaterally in patients with ICH, compared to healthy controls. Significance. Whilst this exploratory analysis was limited by a small, non-age matched sample, significant differences between ICH patients and healthy controls were observed in factors associated with cerebrovascular tone and resistance. These differences suggest underlying cerebral autoregulation changes in ICH, which may play a pivotal role in the morbidity and mortality associated with ICH.

Intracranial Compliance Assessed by Intracranial Pressure Pulse Waveform

“…Under physiologic conditions, P1 produced by arterial contraction is the highest peak observed, with P2 reflecting both vascular and ventricular repercussion of pressure pulse spread. As cerebrovascular resistance is normally lower [11] in comparison with other systems and organs, the tidal wave assumes an amplitude lower than P1. When the buffering mechanisms described above are exhausted and intracranial hypertension (ICH) is present, there is [12] deformation of ICPW, with P2 assuming an amplitude higher than P1, and the ICPW becomes progressively pyramidal [13], with the enlargement of the time interval between P1 and P2 [7] (Figure 1).…”

Dynamics of the cerebral autoregulatory response to paced hyperventilation assessed using subcomponent and time-varying analyses

“…Knowledge of the characteristics of CrCP and RAP in PHPV has potential clinical implications. A recent analysis demonstrated significantly increased CrCP and RAP in patients with intracerebral hemorrhage (ICH) at poikilocapnia and during hypocapnia (35), suggesting that in ICH, cerebrovascular tone and resistance are altered (35). Further information about alterations in CBF controls in these patients could be obtained from the calculation of SRV RAP and SRV CrCP .…”

Cerebral Autoregulation and Neurovascular Coupling in Acute and Chronic Stroke

“…There is debate as to the sensitivity of CrCP to variation in intracranial pressure (ICP) (32). However, the presence of a haematoma in ICH as compared to controls, during normocapnic and hypocapnic conditions, showed significant differences in CrCP and RAP (33). Beyond common indices of dCA, there is limited knowledge of tone and resistance parameters in acute cerebrovascular states as compared to the traumatic brain injury literature.…”