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.

Eloise Sands,Jatinder S Minhas,Man Y Lam,Thompson G Robinson,Ronney B Panerai,Louvinia Wong

doi:10.3390/brainsci10090582

Abstract

(1) Background: Larger blood pressure variability (BPv) in the first 3 h post-stroke onset increases pathophysiological effects such as infarct size, and leads to greater risk of disability, comorbidities and mortality at 90 days. However, there is limited information on the relationship between systemic and cerebral haemodynamic and variability parameters. (2) Objectives: This study determined the effect of a gradual change in head position (GHP) on cerebral blood flow velocity variability (CBFVv) and mean arterial blood pressure variability (MABPv), in healthy controls and acute ischaemic stroke (AIS) patients. Methods: CBFVv and MABPv were expressed as standard deviation (SD) and coefficient of variation. A total of 16 healthy controls (mean age 57 ± 16 years) were assessed over two visits, 12 ± 8 days apart, and 15 AIS patients (mean age 69 ± 8.5 years) were assessed over three visits (V1: 13.3 ± 6.9 h, V2: 4.9 ± 3.2 days and V3: 93.9 ± 11.5 days post-stroke). (3) Results: In response to GHP, MABPv does not initially increase, but over time MABPv showed a significant increase in response to GHP in AIS (visits 2 and 3) and controls (visit 2). Additionally, in response to GHP in AIS, CBFVv increased in the affected hemisphere. Lastly, in AIS, a significant correlation between CBFVv and MABPv, assessed by SD, was seen in the unaffected hemisphere, whereas this relationship was not demonstrated in the affected hemisphere. (4) Conclusions: To our knowledge, this is the first study to analyse the relationship between CBFVv and MABPv. Shedding light on the effect of head position on the relationship between cerebral blood flow and blood pressure is important to improve our understanding of the underlying effects of cerebral autoregulation impairment. This early mechanistic study provides evidence supporting supine head positioning in healthy controls and stroke patients, through demonstration of a reduction of MABPv and increase in CBFVv.

Highlights

Stroke is a principal cause of death and disability worldwide, with 100,000 cases being seen in the UK alone every year [1,2]
The three main findings from this study are: (1) in response to gradual head position (GHP), mean arterial blood pressure variability (MABPv) does not initially increase, but over time, i.e., visit 2 and 3, MABPv shows a significant increase in response to GHP in acute ischaemic stroke (AIS) and control groups; (2) in response to GHP, cerebral blood flow velocity variability (CBFVv) increases in the AH; (3) in AIS, a significant correlation between CBFVv and MABPv, assessed by standard deviation (SD), was seen in the UH, whereas this relationship was not demonstrated in the AH
The results observed in visit 1 showed a significant correlation for the SD of mean arterial blood pressure (MABP) and cerebral blood flow velocity (CBFV) suggesting intact CA preserved in the UH

Summary

Introduction

Stroke is a principal cause of death and disability worldwide, with 100,000 cases being seen in the UK alone every year [1,2]. Ischaemic stroke is most prevalent (85%), caused by a sudden loss of cerebral blood flow (CBF) to an area of the brain due to a cerebral arterial occlusion [3]. (CA) is an essential homeostatic mechanism that maintains CBF, despite fluctuations in mean arterial blood pressure (MABP), provided that cerebral perfusion pressure (CPP) is within the range of. BP pharmacologically, less than half of healthy adult individuals did not show a cerebral autoregulatory plateau, and instead an inferior or over reactive CA was observed [8]. Meng and Gelb (2015) observed that hypercapnia showed a shortening plateau length and increase in CBF [9]. In hypocapnia the effects on plateau length were unknown, with no effect on the lower limit, though a decrease in CBF was observed. It is important to know that CA acts within a few seconds to protect the brain from cerebral ischaemia, by minimising the effects of hypotension on cerebral perfusion

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