Dynamic cerebral autoregulation measurement using rapid changes in head positioning: experiences in acute ischemic stroke and healthy control populations

Abstract

The ideal technique for dynamic cerebral autoregulation (dCA) assessment in critically ill patients should provide considerable variability in blood pressure (BP) but without the need for patient cooperation. We proposed using rapid head positioning (RHP) over spontaneous BP fluctuations for dCA assessment in patients with acute ischemic stroke (AIS). Cerebral blood velocity (transcranial Doppler), beat-to-beat BP (Finometer), and end-tidal CO2 (capnography) were recorded during 5-min baseline and RHP in 16 controls (8 women and 8 men, mean age: 57 ± 16 yr) and 15 patients with AIS (7 women and 8 men, mean age: 69 ± 8 yr) at two (12 ± 8 days) and three visits (13.3 ± 6.9 h, 4.8 ± 3.2 days, and 93.9 ± 11.5 days from the symptom onset), respectively. All participants were able to complete the RHP protocol without difficulty. Compared with controls, patients with AIS were hypocapnic (all visits, P < 0.0024) and hypertensive ( visit 1, P = 0.011), although BP gradually reduced after the acute phase. RHP demonstrated greater beat-to-beat BP variability (BPV) in controls ( visits 1 and 2, P < 0.001) but not in patients with AIS at any visit. Compared with controls, a reduced autoregulation index (ARI) was demonstrated in patients with AIS, at visit 2 for the baseline recording but not at other visits or during RHP. The area under the receiver-operating curve was 0.53 and 0.54 for baseline and RHP, respectively. The RHP paradigm required minimal patient cooperation and could be considered a feasible alternative for assessing dCA, mainly in conditions leading to increased BPV. The lack of BPV increase in AIS with RHP deserves further investigation. NEW & NOTEWORTHY This study used rapid head positioning (RHP) to enhance blood pressure (BP) variability (BPV) to improve BP signal-to-noise ratio and reliability of dynamic cerebral autoregulation (dCA). RHP was well accepted by controls and acute ischemic stroke (AIS); the increased BPV induced in controls was not observed in AIS, suggesting BPV at rest was already elevated. RHP did not improve detection of impaired CA in AIS; further work is needed to understand the different responses observed.

The Effects of Gradual Change in Head Positioning on the Relationship between Systemic and Cerebral Haemodynamic Parameters in Healthy Controls and Acute Ischaemic Stroke Patients

“…This could be explained by an improvement in peri-infarct tissue from visit 1 to visit 2. A study also demonstrated the concept of improvement, where in response to rapid head positioning in visit 2 (~7 days) improved CBFV was observed [28]. However, in both this study and Lam et al (2019), visit 3 seemed to associate with loss of this initial improvement, and subsequently stroke symptoms worsened [28].…”

“…A study also demonstrated the concept of improvement, where in response to rapid head positioning in visit 2 (~7 days) improved CBFV was observed [28]. However, in both this study and Lam et al (2019), visit 3 seemed to associate with loss of this initial improvement, and subsequently stroke symptoms worsened [28]. In contrast, other studies observed impaired CA in the sub-acute phase before recovery in the following weeks [36,37].…”

“…The initial lack of increase in MABPv in visit 1 could be due to pre-existing BPv. Studies have shown that in the hyperacute, acute and subacute stages of AIS patients, pre-existing BPv is present and therefore insensitive to the effects of changes in head position [26][27][28]. However, a significant difference in MABPv observed over time (visits 2 and 3) could be explained by the temporal relationship seen during stroke recovery, however, in healthy controls, a significant increase in BPv in response to GHP was seen [18,29].…”

Cerebral haemodynamics with head position changes post-ischemic stroke: A systematic review and meta-analysis

“…Stroke severity was reported using the National Institutes of Health Stroke Scale (NIHSS) in 13 studies. 16,20–31 Mean NIHSS range was 3–19. Lesion side was reported in 14 studies, 15,20,23–26,28–30,32–36 while only 4 reported thrombolytic therapy.…”

“…In seven studies ( n = 243), participants were assessed within 24 h of stroke onset. 16,20–22,25,30,31 In four studies ( n = 80), they were assessed within 48 h, 16,28,29,37 while in seven studies ( n = 136), it was within seven days. 15,21,23,24,31,36,38 In the final seven studies ( n = 142), patients were assessed over seven days; 26,27,31–35 months 32–34 or years 26,35 post-stroke (16 days to 6 years, Table 1).…”