Elevation of the head during intensive care management in people with severe traumatic brain injury

But what do our doctors have to say about doing this for stroke? 6 posts on HOBOE (Head-of-Bed Optimization of Elevation) for your doctor to injest.

http://europepmc.org/abstract/med/29283434
Alarcon JD ¹ , 

Rubiano AM , 

Okonkwo DO , 

Alarcón J , 

Martinez-Zapata MJ , 

Urrútia G , 

Bonfill Cosp X  

Affiliations

The Cochrane Database of Systematic Reviews [28 Dec 2017, 12:CD009986]

Type: Research Support, Non-U.S. Gov't, Review, Journal Article
DOI: 10.1002/14651858.CD009986.pub2

Abstract

Traumatic brain injury (TBI) is a major public health problem and a fundamental cause of morbidity and mortality worldwide. The burden of TBI disproportionately affects low- and middle-income countries. Intracranial hypertension is the most frequent cause of death and disability in brain-injured people. Special interventions in the intensive care unit are required to minimise factors contributing to secondary brain injury after trauma. Therapeutic positioning of the head (different degrees of head-of-bed elevation (HBE)) has been proposed as a low cost and simple way of preventing secondary brain injury in these people. The aim of this review is to evaluate the evidence related to the clinical effects of different backrest positions of the head on important clinical outcomes or, if unavailable, relevant surrogate outcomes.To assess the clinical and physiological effects of HBE during intensive care management in people with severe TBI.We searched the following electronic databases from their inception up to March 2017: Cochrane Injuries' Specialised Register, CENTRAL, MEDLINE, Embase, three other databases and two clinical trials registers. The Cochrane Injuries' Information Specialist ran the searches.We selected all randomised controlled trials (RCTs) involving people with TBI who underwent different HBE or backrest positions. Studies may have had a parallel or cross-over design. We included adults and children over two years of age with severe TBI (Glasgow Coma Scale (GCS) less than 9). We excluded studies performed in children of less than two years of age because of their unfused skulls. We included any therapeutic HBE including supine (flat) or different degrees of head elevation with or without knee gatch or reverse Trendelenburg applied during the acute management of the TBI.Two review authors independently checked all titles and abstracts, excluding references that clearly didn't meet all selection criteria, and extracted data from selected studies on to a data extraction form specifically designed for this review. There were no cases of multiple reporting. Each review author independently evaluated risk of bias through assessing sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting, and other sources of bias.We included three small studies with a cross-over design, involving a total of 20 participants (11 adults and 9 children), in this review. Our primary outcome was mortality, and there was one death by the time of follow-up 28 days after hospital admission. The trials did not measure the clinical secondary outcomes of quality of life, GCS, and disability. The included studies provided information only for the secondary outcomes intracranial pressure (ICP), cerebral perfusion pressure (CPP), and adverse effects.We were unable to pool the results as the data were either presented in different formats or no numerical data were provided. We included narrative interpretations of the available data.The overall risk of bias of the studies was unclear due to poor reporting of the methods. There was marked inconsistency across studies for the outcome of ICP and small sample sizes or wide confidence intervals for all outcomes. We therefore rated the quality of the evidence as very low for all outcomes and have not included the results of individual studies here. We do not have enough evidence to draw conclusions about the effect of HBE during intensive care management of people with TBI.The lack of consistency among studies, scarcity of data and the absence of evidence to show a correlation between physiological measurements such as ICP, CCP and clinical outcomes, mean that we are uncertain about the effects of HBE during intensive care management in people with severe TBI.Well-designed and larger trials that measure long-term clinical outcomes are needed to understand how and when different backrest positions can affect the management of severe TBI.

ORCIDs linked to this article

Martinez-Zapata MJ , 0000-0002-5836-1138

Read Article at publisher's site

Head position may not affect outcomes during acute stroke treatment

So are these previous ones now obsolete? Your doctor better know the answer. I bet none of these ever made it into use at your hospital, which shows complete and total fucking incompetency.

HOBOE (Head-of-Bed Optimization of Elevation) Study: association of higher angle with reduced cerebral blood flow velocity in acute ischemic stroke.         May, 2012

The influence of positioning upon cerebral oxygenation after acute stroke: a pilot study  Nov. 2011

Bedding and pillows improve positioning in stroke patients Feb. 2015 

Lying Flat, Sitting Up Equal for Mild Stroke Recovery Feb. 2017

 

https://www.healio.com/cardiology/stroke/news/online/%7B68eb46c7-2533-493c-8a04-ce5b87dc8e4e%7D/head-position-may-not-affect-outcomes-during-acute-stroke-treatment?utm_source=selligent&utm_medium=email&utm_campaign=cardiology%20news&m_bt=592835816269

Anderson CS, et al. N Eng J Med. 2017;doi:10.1056/NEJMoa1615715.

June 22, 2017

During treatment for acute stroke, whether a patient was lying down or sitting up did not make a difference in disability outcomes, according to a study in The New England Journal of Medicine.

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“What we found is that head position does not matter so much over and above good nursing care,” Craig S. Anderson, MD, PhD, professor of stroke medicine and clinical neuroscience at the University of Sydney George Institute for Global Health, said in a press release. “It does not help with recovery, with mortality or how a patient feels. However, we also found there was no significant harms associated with either lying down flat or sitting up.”
Head position for acute stroke
For the pragmatic, cluster-randomized, crossover HeadPoST trial, researchers analyzed data from 11,093 patients (mean age, 68 years; 40% women) with acute stroke. Patients were assigned a lying-flat (n = 5,295) or sitting-up position (n = 5,798) in the ED and maintained the position for 24 hours. The patient’s head was elevated at least 30° for the sitting-up position. Patients were followed up at 90 days through phone interview.
The primary outcome was the degree of disability at 90 days as assessed by the modified Rankin scale. Secondary outcomes included major disability or death at 90 days and death at 90 days. Researchers also recorded serious adverse events such as pneumonia.
Patients were placed in the assigned head position at an average of 14 hours after onset of stroke (interquartile range [IQR] = 5-35).
Rate of adherence to the assigned head position for 24 hours was lower in patients assigned the lying-flat position (87%; median time, 23.3 hours; IQR = 20-24) vs. those assigned the sitting-up position (95%; median time, 24 hours; IQR = 23-24; P < .001).
Similar outcomes
At 90 days, the degree of disability did not differ between the two groups (unadjusted OR for difference in distribution of scores on modified Rankin scale in those assigned the lying-flat position = 1.01; 95% CI, 0.92-1.1). Prevalence of major disability or death was also similar in patients assigned the sitting-up position (39.7%) and lying-flat position (38.9%; OR = 0.94; 95% CI, 0.85-1.05). Death occurred in 7.4% of patients in the sitting-up group vs. 7.3% of patients in the lying-flat group (OR = 0.98; 95% CI, 0.85-1.14). The rate of pneumonia did not differ between the two groups.
“Most of the patients in our trial had the assigned head position implemented after the time window for reperfusion with thrombolytic or endovascular treatment had passed, and the patients had mostly mild neurologic deficits from a range of causes of stroke,” Anderson and colleagues wrote. “It is possible that earlier initiation of head position after the onset of symptoms when the ischemic penumbra is potentially modifiable may have produced different results.” – by Darlene Dobkowski

Lying Flat, Sitting Up Equal for Mild Stroke Recovery

So are these previous ones now obsolete? Your doctor better know the answer. I bet none of these ever made it into use at your hospital, which show complete and total fucking incompetency.

HOBOE (Head-of-Bed Optimization of Elevation) Study: association of higher angle with reduced cerebral blood flow velocity in acute ischemic stroke.         May, 2012

The influence of positioning upon cerebral oxygenation after acute stroke: a pilot study  Nov. 2011

Bedding and pillows improve positioning in stroke patients Feb. 2015

The new one here: which is totally useless since mild has no objective definition.

Lying Flat, Sitting Up Equal for Mild Stroke Recovery

But uncertain whether trial findings apply to severe, large-vessel strokes

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• by Kristina Fiore
  Associate Editor, MedPage Today February 22, 2017
• This article is a collaboration between MedPage Today® and:
  

Action Points

• Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
• Note that this large randomized trial found no significant benefit or risk to a "lying flat" approach after stroke compared to a more upright positioning.
• Be aware that the vast majority of strokes were mild; some experts conjecture that lying flat may still offer benefit to those with more severe strokes.

HOUSTON -- It didn't matter whether patients lay flat or sat up while recovering from a stroke: there were no differences in death or disability 3 months later, researchers reported here.
In the HeadPoST trial -- a cluster crossover trial involving 114 hospitals around the world -- there was no significant difference in changes in modified Rankin Scale (mRS) scores at 90 days between the two post-stroke strategies (OR 1.01, 95% CI 0.92-1.10, P=0.84), Craig Anderson, MD, PhD, of The George Institute in Australia, and colleagues reported at the International Stroke Conference here.
"There was no difference at all in any of the measures of disability, but conversely, we didn't show any extra harms, we didn't find any extra risk of pneumonia," Anderson said during a press briefing. "We couldn't find any clear signal of benefits or harms in any of the subgroups that we have examined. So we can't make any clear recommendations for policy about whether there could be benefits or harms of a specific head position in acute stroke."
"Whether we can improve upon what nature is [doing] by positioning or pumps or other things is debatable," he added. "I guess our study shows maybe it's not possible to do that naturally."
Researchers who were not involved in the study cautioned that most of the included patients had mild strokes, so the question as to which strategy should be preferred for those with more severe strokes remains unanswered.
"It's quite conceivable people with larger vessel strokes presumably might benefit more from the head position being flat," said Bruce Ovbiagele, MD, of Medical University of South Carolina in Charleston, who moderated the session at which the findings were presented. "There could be a difference there. The type of population they had in this study is reflective of the kind of patients we see for most part, but when you think about the potential underlying pathophysiology, those large-vessel [patients] might benefit from lying flat."
Anderson noted that a recent Doppler study suggested that lying flat increases blood flow, which would be important following ischemic stroke. Thus, having recovering patients take on the supine position could be beneficial by increasing blood flow to the brain.
On the other hand, laying flat could be tied to complications such as aspirating stomach contents or saliva, contributing to pneumonia risk.
AHA/ASA guidelines for the early management of patients with acute ischemic stroke suggest that non-hypoxic patients who are able to tolerate it should lay in the supine position, while patients at risk for airway obstruction or aspiration and those with suspected elevated intracranial pressure should have the bed tilted 15 to 30 degrees.
There's little evidence, however, regarding which position is optimal, and physicians must balance competing interests and patient tolerance, Anderson said.
To assess which strategy might prove superior, the researchers recruited hospitals to a cluster crossover trial, in which they first assigned 70 patients to one strategy, and then the participating centers crossed over and assigned a subsequent 70 patients to the other strategy.
Overall, they assessed just over 11,000 patients from 114 hospitals in 19 countries, with large populations from the U.K. and China. Mean patient age was 68, 40% were female, and the median NIHSS score was 4.
In addition to finding no difference in the unadjusted shift in mRS scores at 90 days, there were no differences in further controlled analyses; nor were there any differences among subgroups assessed by age, gender, region, or severity.
Additionally, there were no differences whether patients had an ischemic or hemorrhagic stroke, Anderson reported.
He cautioned that laying flat was uncomfortable to many patients, potentially raising the issue of compliance.
Ralph Sacco, MD, of the University of Miami, a past president of the American Heart Association and president-elect of American Academy of Neurology, who was not involved in the study, noted that more data to show how well hospitals and patients followed the protocols could be helpful.
"These patients had more mild stroke, which means they are more likely to be getting up and walking around," he noted.
Sacco echoed other researchers' concerns about the study's majority of mild stroke patients being a limitation, as patients with worse disease may potentially have different outcomes.
"We need more subgroup analysis to know if large strokes with signs of edema show any benefit," Sacco said. "The important [question] here is whether those with large strokes -- hemorrhages or infarcts -- that may even have signs of early edema" would do better.

The study was supported by the National Health and Medical Research Council of Australia.
The authors reported reimbursement from Takeda China and Boehringer Ingelheim for speaker fees and travel expenses.

• Reviewed by F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner

last updated 02.22.2017

• Primary Source

  International Stroke Conference

  Source Reference: Anderson CS, et al "Head position in stroke trial: An international cluster crossover randomized trial" ISC 2017; Abstract LB1.

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Latest in Your Specialty

Bedding and pillows improve positioning in stroke patients

How does this interact with the Head of Bed positioning? How many years will this take to get rolled out to your hospital? 50? 100?

HOBOE (Head-of-Bed Optimization of Elevation) Study: association of higher angle with reduced cerebral blood flow velocity in acute ischemic stroke.

The influence of positioning upon cerebral oxygenation after acute stroke: a pilot study

The new one here:

Bedding and pillows improve positioning in stroke patients

Many patients with a cerebral injury cannot move independently. Every year, 45,000 new stroke patients are affected in such a way. They have to be repositioned at regular intervals for a long period of time in order to prevent pressure ulcers that may develop as a result of patients’ physical immobility. Heidrun Pickenbrock et al., in a topical original article in Deutsches Ärzteblatt International, compare two positioning methods for immobile patients. They found that lying in the so called neutral position is more comfortable for affected patients, and that mobility of hips and shoulders is improved compared with when the conventional method is used.
In the study, more than 218 immobile patients with a brain injury were placed in a conventional position or the neutral position for two hours. The positions differ primarily in terms of the load placed on certain body sections. In the neutral position, the body parts are aligned in order to prevent overextension and shortening of muscles and tendons. A survey among participating patients showed that the neutral position is experienced as more comfortable than the conventional position. Furthermore, a study of passive mobility showed that the hip and shoulder joints were more mobile after patients had been placed in the neutral position than after conventional positioning.
http://www.aerzteblatt.de/pdf.asp?id=167249

 

 

Optical Bedside Monitoring of Cerebral Blood Flow in Acute Ischemic Stroke Patients During Head-of-Bed Manipulation

This was first written about in Nov. 2011 and I bet not one single hospital in the world tried to implement this. Prove me wrong.
http://stroke.ahajournals.org/content/45/5/1269.abstract?etoc

1. Christopher G. Favilla, MD*;
2. Rickson C. Mesquita, PhD*;
3. Michael Mullen, MD;
4. Turgut Durduran, PhD;
5. Xiangping Lu, MD;
6. Meeri N. Kim, PhD;
7. David L. Minkoff, BA;
8. Scott E. Kasner, MD;
9. Joel H. Greenberg, PhD;
10. Arjun G. Yodh, PhD;
11. John A. Detre, MD

+ Author Affiliations

1. From the Departments of Neurology (C.G.F., M.M., X.L., S.E.K., J.H.G., J.A.D.), Physics and Astronomy (R.C.M., M.N.K., D.L.M., A.G.Y.), and Radiology (J.A.D.), University of Pennsylvania, Philadelphia, PA; Institute of Physics, University of Campinas, Campinas, Brazil (R.C.M.); and ICFO-Institut de Ciències Fotòniques, Castelldefels, Barcelona, Spain (T.D.).

1. Correspondence to John A. Detre, MD, Department of Neurology, University of Pennsylvania, 3400 Spruce St, 3 West Gates, Philadelphia, PA 19104-4283. E-mail detre@mail.med.upenn.edu

1. Guest Editor for this article was Markku Kaste, MD, PhD.
2. ↵* Drs Favilla and Mesquita are joint first authors and contributed equally.

Abstract

Background and Purpose—A primary goal of acute ischemic stroke (AIS) management is to maximize perfusion in the affected region and surrounding ischemic penumbra. However, interventions to maximize perfusion, such as flat head-of-bed (HOB) positioning, are currently prescribed empirically. Bedside monitoring of cerebral blood flow (CBF) allows the effects of interventions such as flat HOB to be monitored and may ultimately be used to guide clinical management.

Methods—Cerebral perfusion was measured during HOB manipulations in 17 patients with unilateral AIS affecting large cortical territories in the anterior circulation. Simultaneous measurements of frontal CBF and arterial flow velocity were performed with diffuse correlation spectroscopy and transcranial Doppler ultrasound, respectively. Results were analyzed in the context of available clinical data and a previous study.

Results—Frontal CBF, averaged over the patient cohort, decreased by 17% (P=0.034) and 15% (P=0.011) in the ipsilesional and contralesional hemispheres, respectively, when HOB was changed from flat to 30°. Significant (cohort-averaged) changes in blood velocity were not observed. Individually, varying responses to HOB manipulation were observed, including paradoxical increases in CBF with increasing HOB angle. Clinical features, stroke volume, and distance to the optical probe could not explain this paradoxical response.

Conclusions—A lower HOB angle results in an increase in cortical CBF without a significant change in arterial flow velocity in AIS, but there is variability across patients in this response. Bedside CBF monitoring with diffuse correlation spectroscopy provides a potential means to individualize interventions designed to optimize CBF in AIS.

HOBOE (Head-of-Bed Optimization of Elevation) Study: association of higher angle with reduced cerebral blood flow velocity in acute ischemic stroke.

You can compare this one to a previous post.
current:
http://feedproxy.google.com/~r/nih/bxxu/~3/4OYCBnhlFjU/display.cgi
Cerebral autoregulation can be impaired after ischemic stroke, with potential adverse effects on cerebral blood flow during early rehabilitation.The objective of this study was to assess changes in cerebral blood flow velocity with orthostatic variation at 24 hours after stroke.This investigation was an observational study comparing mean flow velocities (MFVs) at 30, 15, and 0 degrees of elevation of the head of the bed (HOB).Eight participants underwent bilateral middle cerebral artery (MCA) transcranial Doppler monitoring during orthostatic variation at 24 hours after ischemic stroke. Computed tomography angiography separated participants into recanalized (artery completely reopened) and incompletely recanalized groups. Friedman tests were used to determine MFVs at the various HOB angles. Mann-Whitney U tests were used to compare the change in MFV (from 30� to 0�) between groups and between hemispheres within groups.For stroke-affected MCAs in the incompletely recanalized group, MFVs differed at the various HOB angles (30�: median MFV=51.5 cm/s, interquartile range [IQR]=33.0 to 103.8; 15�: median MFV=55.5 cm/s, IQR=34.0 to 117.5; 0�: median MFV=85.0 cm/s, IQR=58.8 to 127.0); there were no significant differences for other MCAs. For stroke-affected MCAs in the incompletely recanalized group, MFVs increased with a change in the HOB angle from 30 degrees to 0 degrees by a median of 26.0 cm/s (IQR=21.3 to 35.3); there were no significant changes in the recanalized group (-3.5 cm/s, IQR=-12.3 to 0.8). The changes in MFV with a change in the HOB angle from 30 degrees to 0 degrees differed between hemispheres in the incompletely recanalized group but not in the recanalized group.Generalizability was limited by sample size.The incompletely recanalized group showed changes in MFVs at various HOB angles, suggesting that cerebral blood flow in this group may be sensitive to orthostatic variation, whereas the recanalized group maintained stable blood flow velocities.

Previous:
 http://oc1dean.blogspot.com/2011/11/influence-of-positioning-upon-cerebral.html

The influence of positioning upon cerebral oxygenation after acute stroke: a pilot study

So who has followed up on this to see how best to position a patient after a stroke? Or does it not matter because we should first be figuring out how to open the capillaries that are closed by pericytes?
http://ageing.oxfordjournals.org/content/37/5/581.full
Passive postural changes may have an effect on a number of physiological parameters after stroke [1]. For example, standing, sitting or even elevating the head after stroke might reduce cerebral blood flow due to poor collateral circulation and an inability to regulate and augment cerebral blood flow in ischaemic regions of the brain [2–5]. Optimal positioning for patients in the acute stage after stroke is still unknown [6–8]. Variation in clinical practice is evident in the literature [5–9] and has been observed [10]. This variation could be because of the paucity of experimental findings to inform a scientific rationale for positioning early after stroke. For example, traditionally, people who have suffered a large hemispheric stroke have been managed with head elevation between 30° and 45° [5], a practice generalised from clinical experience with head trauma patients despite differences in pathophysiology [11].

There is some experimental evidence that positional change may alter cerebral haemodynamics after stroke [12, 13]; but, there is disagreement on how this is changed early after the ictus [12–15]. Moreover, the natural history of autoregulation following stroke is unclear [16]. At present, there is a paucity of evidence to support or refute the possibility that in some people the vulnerable ischaemic penumbra might be at risk from a reduction in cerebral blood flow mediated through positional changes after stroke [1].

To be relevant clinically, cerebral oxygenation needs to be measured in relation to changes in posture. It also needs to be measured in real time at the bedside to enable appropriate clinical decisions about positioning. The relatively new technology of near infrared spectroscopy (NIRS), a minimally invasive technique, offers the possibility of making such measurements [17]. The aim of this pilot study is to explore whether changes in position, involving different placements of the head and upper body in relation to gravity, in the first week after a middle cerebral artery cortical ischaemic stroke produce changes in cerebral oxygenation in the region of the arterial territory.

Next Section

Methods

A replicated single case study design was used with the phase sequence ABACA (details in procedure section below). The study was approved by the Local Research Ethics Committee and participants provided either written informed consent or, if that was not possible, assent was provided by their next-of-kin.

Participants were adults who had suffered a middle cerebral artery cortical ischaemic stroke, confirmed by computer tomography (CT) no more than 7 days prior to testing. Exclusion criteria were: a previous stroke in the same division of the ipsilesional medial cerebral artery (MCA) territory; critical illness (peripheral oxygen saturations <90% on air, pulse >100 beats per min, systolic BP <90 mmHg, Glasgow Coma Score <10); inability to follow one-stage command; and, inability to sit upright on the edge of a bed with support from one person.

Participants were seated in a multi-position chair (see instrumentation below) in a quiet room adjacent to the acute stroke unit. Two optodes were placed bihemispherically on their scalp with a 4 or 5 cm distance between the receiving and emitting probes over each hemisphere. Positional accuracy of the optodes was achieved through superficial scalp marking over the ischaemic lesion using laser guidance at CT scanning and mirrored over the opposite hemisphere. An electronic topical recorder was used to record peripheral oxygen saturations, pulse and blood pressure at 2-min intervals. This ensured systematic haemodynamic changes were demonstrated independently of cerebral monitoring. Each participant then completed the standardised five-phase posture sequence designed to reproduce positions often used during the first week after stroke:

• A phase—supine lying.
• B phase −45° back-rest/seat with legs raised up straight as if lying propped up in bed.
• A phase—supine lying.
• C phase—sitting upright with hips, knees and ankles at 90° as if sitting in a chair.
• A phase—supine lying.

After an initialisation phase of 15 min supine, each postural challenge lasted up to15 min depending upon subjects' comfort in the position.

A two-channel ‘NIRO 300’ (Hamamatsu Photonics K.K. Japan) was used to record data on cerebral oxygenation at 2 Hz. The ‘NIRO 300’ produces infra-red light via an emitting probe which directs the photons perpendicular to the tissue surface. A receiving probe detects the incident and transmitted light intensities from the tissue. Inbuilt computational software utilising algorithms generated from the modified Beer–Lambert law display and record relative changes in the concentration of oxygenated haemoglobin (Δ[HbO₂]), deoxygenated haemoglobin (Δ[Hb]) and oxidised cytochrome oxidase (Δ[CtOx] ) over the period of study. Using the technique of spatially resolved spectroscopy (SPS), a measure of absolute tissue oxygen saturation, the tissue oxygenation index (TOI) can be generated. TOI is the ratio of oxygenated ([HbO₂]) to total tissue haemoglobin concentrations ([HbT]) [17].

The multi-position chair used for testing had an adjustable back- and leg-rest enabling any position between lying supine and sitting with hips, knees and ankles at 90°. Position was controlled by the researcher through a hand-held electronic device.

The descriptive data collected for participants were: age, gender and the National Institute of Health Stroke Scale (NIHSS) [18].

The primary outcome was bihemispheric NIRS monitored TOI (i.e. the ratio of oxygenated ([HbO₂]) to total tissue HbT.

The probability of serial dependency in 1-min sets of data, collected immediately before and after each posture change, was tested using the autocorrelation coefficient and Bartlett's test. All data sets were significantly autocorrelated-r > 0.183, range 0.285–0.991. Statistical comparison of phases was therefore invalid and data were plotted and then interpreted by visual inspection for trend and level.

Previous SectionNext Section

Results

Seven people who met the study criteria were included. In summary, their mean age was 70.71 years (range 58–81 years); five were male and the median time for measurement after stroke was 5 days (range 4–7). Subject characteristics are presented in Appendix 1 in the supplementary data on the journal's website. Two patients (subjects 2 and 3) had their anti-hypertensive medication continued after stroke onset and one patient (subject 2) had occlusion of the ipsilateral internal carotid artery. One patient (subject 2) exhibited orthostatic hypotension (defined as a drop in systolic blood pressure ≥20 mmHg) on postural challenges. There were no changes noted in heart rate or oxygen saturations.

Visual inspection of the plotted data indicated that six of the seven patients (subjects 1, 2, 3, 5, 6, 7) demonstrated changes in TOI between supine and sitting up positions. In these patients, the pattern displayed a maximum value of TOI in the supine position and a reduction of TOI on sitting up in the affected middle cerebral artery territory (Figures 1 and 2). There were also similar changes in TOI observed in the contra-lateral lobe (subjects 1, 2, 3, 6, 7); but these were less marked. In one patient (subject 5), TOI was maximal in the upright position and reduced in the supine position in the contra-lateral lobe only.