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

Abstract

The effects of upright postures on the cerebral circulation early post-ischaemic stroke are not fully understood. We conducted a systematic review and meta-analysis to investigate the effects of head positioning on cerebral haemodynamics assessed by imaging methods post-ischaemic stroke. Of the 21 studies included ( n = 529), 15 used transcranial Doppler. Others used near-infrared, diffuse correlation spectroscopy and nuclear medicine modalities. Most tested head positions between 0° and 45°. Seventeen studies reported changes in CBF parameters (increase at lying-flat or decrease at more upright) in the ischaemic hemisphere with position change. However, great variability was found and risk of bias was high in many studies. Pooled data of two studies ≤24 h ( n = 28) showed a mean increase in cerebral blood flow (CBF) velocity of 8.5 cm/s in the ischaemic middle cerebral artery (95%CI,−2.2–19.3) from 30° to 0°. The increase found ≤48 h ( n = 50) was of 2.3 cm/s (95%CI,−4.6–9.2), while ≤7 days ( n = 38) was of 8.4 cm/s (95%CI, 1.8–15). Few very early studies (≤2 days) tested head positions greater than 30° and were unable to provide information about the response of acute stroke patients to upright postures (sitting, standing). These postures are part of current clinical practice and knowledge on their effects on cerebral haemodynamics is required.

Cerebral blood flow velocity progressively decreases with increasing levels of verticalization in healthy adults. A cross-sectional study with an observational design

“…the range of results of previous studies investigating BP and HR in different body positions (17)(18)(19). In summary, our study provides evidence that the circulatory changes during verticalization are comparable to the changes during the orthostatic reaction during conventional mobilization.…”

“…The results of previous studies investigating the changes in HR and BP associated with changes in body positions were inconclusive. For systolic BP, results range from an increase in more upright body positions (17) to no significant change (18) to a significant decrease (19). Diastolic BP as well as HR did not change significantly in some studies (17,19), while they increased in sitting position compared to supine in another (18).…”

“…For systolic BP, results range from an increase in more upright body positions (17) to no significant change (18) to a significant decrease (19). Diastolic BP as well as HR did not change significantly in some studies (17,19), while they increased in sitting position compared to supine in another (18). Hence, our findings concerning BP and HR during verticalization fall within (p = 0.04) for diastolic BP and significant at 70 • (p = 0.002) for oxygen saturation.…”

“…In addition, it allows CBFV measurements with continuous TCD, which would have been more prone to artifacts during conventional mobilization due to more bulk movement. Doppler ultrasound is widely used to measure CBFV ( 20 ). In addition, CBFV seems to be a good surrogate for CBF, at least during simulated orthostasis ( 13 ).…”

Pre-stroke Physical Activity and Cerebral Collateral Circulation in Ischemic Stroke: A Potential Therapeutic Relationship?

“…Given the established link between favorable collateral circulation and improved stroke outcomes, the cerebral collateral circulation system is regarded as a potential therapeutic target to improve outcomes in acute ischemic stroke ( 6 , 13 ). Pharmaceutical and non-pharmaceutical strategies to optimize collateral circulation in the acute stroke setting have been proposed, including optimal head position during acute care ( 14 , 15 ), medications to induce blood volume expansion, vasodilation or hypertension, neural stimulation, partial occlusion of the aorta, and limb compression devices ( 6 , 13 ). However, the most appropriate strategies remain unclear ( 6 ).…”