Cerebral Autoregulation after Subarachnoid Hemorrhage: Comparison of Three Methods

Abstract

In patients after subarachnoid hemorrhage (SAH) failure of cerebral autoregulation is associated with delayed cerebral ischemia (DCI). Various methods of assessing autoregulation are available, but their predictive values remain unknown. We characterize the relationship between different indices of autoregulation. Patients with SAH within 5 days were included in a prospective study. The relationship between three indices of autoregulation was analyzed: two indices calculated using spontaneous blood pressure fluctuations, Sxa (based on transcranial Doppler) and TOxa (based on near-infrared spectroscopy); and transient hyperemic response test (THRT) where a brief compression of the common carotid artery is used. The predictive value of indices was assessed using data from the first 5 days. Overall there was only moderate correlation between indices. However, both Sxa and TOxa showed good accuracy in predicting impaired autoregulation evidenced by a negative THRT (area under the curve (AUC): 0.788, 95% CI: 0.723 to 0.854 and AUC: 0.827, 95% CI: 0.769 to 0.885, respectively). All indices proved accurate in predicting DCI when 0-to 5-day data were used (AUC: 0.801, 95% CI: 0.660 to 0.942; AUC: 0.857, 95% CI: 0.731 to 0.984, AUC: 0.796, 95% CI: 0.658 to 0.934 for THRT, Sxa, and TOxa, respectively). Combining all three indices had 100% specificity for predicting DCI. While multiple colinearities exist between the assessed methods, multimodal monitoring of cerebral autoregulation can aid in predicting DCI.

Dynamic Autoregulatory Response After Aneurysmal Subarachnoid Hemorrhage and Its Relation to Angiographic Vasospasm and Clinical Outcome

“…Thus, some authors were able to detect good agreement between different measurement methods [46], the majority of previous studies demonstrated only minor correlations [8,10,47]. However, specificity for predicting DCI could be enhanced by combining stimulus-response and spontaneous fluctuation methods obtained from the same patient, although the time courses of the two indices showed only a weak correlation [9].…”

“…With this test, the autoregulation index (ARI) is measured which is derived from reactions of the middle cerebral artery flow velocity to blood pressure variations induced by bilateral thigh cuff deflations [7]. However, validity of those different CA measurements remains unclear since previous studies demonstrated only a very limited consistency between those methods [8][9][10][11]. This implicates that these methods are not interchangeable when describing the actual status of CA.…”

Microglia inflict delayed brain injury after subarachnoid hemorrhage

“…An appropriate explanation for this phenomenon might also be a direct mechanism-e.g., mediated chemically through hemoglobin metabolites or physically through pressure changes-which inflicts the intraparenchymal microglia accumulation. Another possible explanation for asymmetric microglia accumulation after SAH has been discussed by Czosnyka and co-workers, who argue for an asymmetry of blood flow auto-regulation after SAH [12].…”

Cerebral haemodynamics during experimental intracranial hypertension

“…Moreover, investigations combining near infrared spectroscopy derived cortical oxygenation and transcranial Doppler derived middle cerebral artery Fv also indicate a cortical vulnerability. Budohoski et al 34 found that the correlation between ABP and Fv seems to be lower than the correlation between ABP and NIRS oxygenation, while Kuriyama 35 demonstrated that prior to the onset of syncope, cortical oxygenation decreases, while middle cerebral artery Fv remains constant. From a teleological point of view, such cortical sensitivity to high ICP could be a mechanism for diverting blood flow to areas of the brain most crucial for survival; the brainstem cardiorespiratory nuclei.…”