Head Position on Cerebral Haemodynamics in Acute Ischemic Stroke and Controls
Head Position on Cerebral Haemodynamics in Acute Ischemic Stroke and Controls
Cerebral autoregulation is an important mechanism whereby cerebral perfusion is normally
 maintained at a constant level, over a relatively wide blood pressure range. It can be
 assessed noninvasively by the use of Trans Cranial Doppler (TCD). This means using ultrasound
 probes over both sides of the head to measure changes in blood flow in one of the main brain
 arteries (the middle cerebral artery) in response to beat to beat changes in blood pressure
 dynamic cerebral autoregulation (dCA). It is established that dCA is impaired following
 moderate to severe stroke, acting as a key role in the development of secondary brain damage
 related to brain swelling and further damage related to the low blood flow. The
 administration of clot busting therapy (thrombolysis), one of the main approved treatments of
 acute ischaemic stroke (AIS), results in recanalisation of the blocked artery in only
 approximately 50% of patients. Therefore, as well as attempts to treat major vessel blockage,
 improving brain blood flow, particularly to the penumbral area, through arteries that bypass
 the blockage is another potential therapeutic approach in AIS.One simple way of achieving
 this might be to lower the head of AIS patient into a lying flat (0⁰) position. However, to
 date, there have been very few studies exploring this. This research will use the noninvasive
 technique of Trans Cranial Doppler (TCD) to see how blood flow changes in different head
 positions, both in healthy volunteers and AIS patient. This study will provide important data
 regarding blood pressure management in acute stroke, an important and common clinical
 dilemma.
In the United Kingdom (UK) alone, approximate 100,000 people suffer a stroke each year.
 Improved management of stroke patients not only reduces morbidity and mortality, but also
 reduces the cost of long term social care.

 The brain has control systems (i.e.cerebral autoregulation) to maintain blood flow to the
 brain, over a relatively wide blood pressure range. Cerebral Autoregulation can be described
 as static, reflecting the integrity of such mechanisms over time, or dynamic, occurring in
 response to sudden fluctuations in perfusion pressure. When blood pressure drops, small
 arteries increase in size to restore flow levels, and when blood pressure rises, they narrow
 to protect the most delicate blood vessels. It is known that sudden decompensated blood
 pressure (BP) changes can occur after stroke, this could result in brain bleeding and
 swelling when there is uncontrolled increased blood flow, or reduce the viability of tissue
 surrounding the stroke area when there is reduced blood flow to the brain.

 It is known that the clot busting agent (Alteplase), the main effective treatment used in the
 acute stroke can only improve blood flow in already blocked arteries in 50% of patients.
 Therefore, as well as attempts to treat blockage of major vessel, improving the blood flow
 through vessel that bypass the blocked vessel around the stroke area (penumbra) could be
 another potential therapeutic approach in acute ischaemic stroke patients. A simple way of
 increase blood flow to these penumbral area might be just lower the head of acute stroke
 patients into a lying flat position. Several observational studies have investigated the
 effects of head positioning on blood flow to the brain in a healthy population, however few
 studies carried out on acute ischaemic stroke patients so far.

 Cerebral autoregulation can be assessed non-invasively by the use of Trans Cranial Doppler
 (TCD). This means using ultrasound probes over both sides of the head to measure changes in
 blood flow in one of the main brain arteries (the middle cerebral artery) in response to beat
 to beat changes in blood pressure dynamic cerebral autoregulation. This research will use the
 noninvasive technique of Trans Cranial Doppler to see how blood flow changes during different
 head position between acute ischaemic stroke patients and healthy controls, as well as over
 time during recovery after a stroke. This knowledge will help us to understand the changes in
 brain blood flow control and blood pressure in stroke patients, with implications of
 diagnosis, prognosis, and treatment of the disease.
Inclusion Criteria:

 - Informed volunteer consent, patient consent or personal consultee declaration form

 -  Male or female, aged 18 years or above

 -  Able (in the Investigator's opinion) and willing to comply with all study requirements

 -  Willing to allow his or her General Practitioner (GP) to be notified of participation
 in the study Stroke Patient-specific Inclusion Criteria

 -  Clinical diagnosis of ischaemic stroke within 24 hours of onset (for patients waking
 with a stroke, time of onset will be taken to be the time when the patient was last
 asymptomatic)

 Exclusion Criteria:

 -  Male or Female, aged under 18 years

 -  Unable (in the Investigator's opinion) or unwilling to comply with any study
 requirements

 -  Participants who practice yoga regularly

 -  Female participants who are pregnant, lactating or planning pregnancy during the
 course of the study Stroke Patient-specific Exclusion Criteria

 -  Clinical diagnosis of stroke greater than 24 hours from onset

 -  Having had a resolved transient ischaemic attack (TIA) (i.e. neurological
 symptoms completely resolved upon hospital presentation)

 -  Definite clinical indication to 'sitting up' (≥30⁰) head position (i.e.
 pneumonia, decompensated heart failure)

 -  Definite clinical indication to lying flat (0⁰) head position (i.e. shock,
 airways obstruction)

 -  Co-morbidity with anticipated life expectancy less than 3 months