The effects of positioning after stroke on physiological homeostasis: A review [6]

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Research letters
401
1
Department of Community Health Sciences,
St George’s, University of London,
Cranmer Terrace, Tooting, London SW17 0RE, UK
2
School of Health and Social Care, Reading University,
Whiteknights Lane, Reading, UK
*To whom correspondence should be addressed
Email: tharris@sgul.ac.uk
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doi:10.1093/ageing/afi105
The effects of positioning after stroke on
physiological homeostasis: a review
SIR—There is increasing evidence that several abnormal
physiological parameters (pyrexia, hyperglycaemia, hypoten-
sion, hypoxia) post stroke are associated with poor outcome
[1] and strategies are now being used to maintain physiolog-
ical homeostasis, although randomised controlled trials are
required to measure their effectiveness [2, 3]. Other physio-
logical parameters such as oxygenation, blood pressure, cer-
ebral blood flow and intracranial pressure may be
potentially modified by changes in body position after
stroke, some beneficial and others not [4, 5]. Normally,
assuming an upright position leads to transient hypotension
which is compensated by an increase in heart rate and cere-
bral vasodilatation, thus maintaining cerebral perfusion [6].
After acute stroke, cerebral autoregulation is impaired,
thereby risking cerebral hypoperfusion upon standing [7].
Whether sitting out of bed within 24 hours of stroke as part
of an early rehabilitation programme reduces early neuro-
logical deterioration, because of a complex interaction
between improved cerebral perfusion pressure, reduced
intracranial pressure and improved oxygenation, is unclear
at present [8]. Before evidence-based recommendations can
be made on positioning in the acute phase of stroke (within
24 hours to 7 days), information is required about its effects
on physiological homeostasis, which may have prognostic
significance.
A systematic literature search was therefore undertaken
to find clinical studies investigating the effects of different
body positions on physiological homeostasis during the first
week after stroke.
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Research letters
402
Methods
A systematic search of Medline/PubMed databases, as well
as the Cochrane Database of Systematic Reviews from 1966
to 2003 was undertaken entering the terms ‘body position’,
‘posture’, ‘oxygen’, ‘cerebral perfusion’, ‘cerebral blood
flow’, ‘cerebral artery velocity’, ‘intracranial pressure’ and
‘blood pressure’. We combined these items with the term
‘acute stroke’. In addition, the search strategy included hand
searching of reference lists, bibliographies of retrieved
papers and contact with authors as suggested by the
MOOSE Group [9]. The list of studies identified by the
search was independently assessed by two reviewers (AB,
VMP) to find those studies which met the inclusion criteria
for this review. For further details of the methods used,
please see Appendix I in the supplementary data on the
journal website (www.ageing.oupjournals.org).
Results
We identified 28 studies on the effects of body positioning
on oxygenation, blood pressure, cerebral perfusion, cerebral
artery velocity and intracranial pressure during the first
week of stroke [4, 10–35]. Four studies only described single
case reports [17–20], ten studies examined blood pressure
change after 1 week of stroke [24–33] and four studies
described cerebral blood flow in patients in the chronic
phase of stroke [21–24]. Ten studies met the pre-deter-
mined criteria for inclusion in the review [4, 10–16, 34, 35].
Table 1 summarises the univariate associations between the
effects of positioning on physiological parameters after
stroke.
Oxygenation
Four studies were described [4, 10–12]. Elizabeth and col-
leagues [4] demonstrated that mean oxygen saturation levels
were higher in stroke patients managed in the semi-recum-
bent position (93.2% versus 91.9%) than those supine.
Rowat and colleagues [12] suggested that if patients could
tolerate sitting in a chair, this was the optimal position to
maintain the highest mean oxygen saturation (≥96%) within
72 hours of stroke, although a small proportion of patients
(18%) desaturated when in this position. Pang and col-
leagues [10] and Chatterton and colleagues [11] demon-
strated no significant changes in oxygenation with different
body positions within 48 and 72 hours, respectively, of
acute stroke.
Blood pressure
Four studies were described [13, 14, 34, 35]. Panayiotou and
colleagues [13] demonstrated significant increases in blood
pressure in mild to moderate stroke patients when managed
supine for 10 minutes and then either sitting or standing for
5 minutes. The incidence of sustained postural hypotension
was <10%. Panayiotou and colleagues [34] also demon-
strated no significant falls in mean arterial blood pressure
and heart rate in stroke patients specifically taking anti-
hypertensive therapy after sitting or standing up. Schwarz
and colleagues [14] demonstrated significant falls in mean
arterial blood pressure with early head elevation (15–30°)
from supine (90 ± 1.6 mmHg to 76.1 ± 1.6 mmHg) in
18 patients within 6 days of ischaemic stroke. Asperg [35]
demonstrated in a controlled study (non-randomised) that
regular early standing up within 48 hours of stroke did not
lead to significant orthostatic hypotension (tilting at 70°) at
1 week but was associated with a lower proportion of
severely disabled patients at 1 week compared with a con-
trol group (no regular standing practice).
Cerebral perfusion and cerebral artery velocity
Three studies were identified [14–16]. Jack and colleagues
[15], using single photon emission tomography, showed
improved regional cerebral perfusion in the semi-recum-
bent position (30–45°) compared with supine. Schwarz and
colleagues [14], however, demonstrated significant falls in
middle cerebral artery velocity and cerebral perfusion pres-
sure with early head elevation (30°) from supine in 18
patients within 6 days of ischaemic stroke. Wojner and col-
leagues [16] showed that middle cerebral artery velocity was
significantly higher by 13.1% in 11 patients who were man-
aged in the supine position compared with the semi-recum-
bent position within 48 hours of ischaemic stroke.
Intracranial pressure
Schwarz and colleagues [14] demonstrated that intracranial
pressure decreased from 13.0±0.9mmHg to 12.0±0.9mmHg
at 15° and to 11.4 ± 0.9 mmHg at 30° backrest elevation in
18 patients with ischaemic stroke.
Discussion
The research evidence available does not enable us to
answer the following clinical questions due to lack of ran-
domised controlled trial data. Should we manage all stroke
patients initially in the semi-recumbent position or sitting
up? Which patients should be placed in which positions, for
how long and at what time after stroke? Studies included in
this search were observational in nature, including a narra-
tive description of each study with limited data on outcome.
Limitations include number of patients studied, lack of data
on stroke type, lack of multivariate analyses and the hetero-
geneity of the populations studied.
Studies measuring the effects of body position on oxy-
gen saturation levels differed in stroke severity, variations
in positions, duration of oxygen saturation measurements
and intervals between stroke onset and oxygen saturation
measurement. However, there was some evidence that
patients nursed in a sitting position or propped up in bed
had higher oxygen saturation levels than those in supine
positions, although desaturation occasionally occurred in
these positions, throwing into question the adoption of this
position for all patients in routine practice. The short-term
changes in oxygen saturation described in these observa-
tional studies may not necessarily reflect what is seen in clin-
ical practice where positional changes are adopted over a
long period of time (2–4 hours) [36]. Nursing and therapy
practice occasionally advocates the practice of side lying on
the affected side [37]; however, potentially this could lead to
further hypoxia resulting from increased blood flow to the
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403
Table 1. Effects of positioning on physiological parameters in acute stroke
Variable Positional intervention No. Mean age Stroke type
Timing of
intervention Duration of each position Stroke severity Effects
......................................................................................................................................................................................................................................................
Oxygen Supine, sitting, paretic and
non-paretic side lying
20 – – <48 hours 20 minutes MRC grade ≤2 O
2
saturation >90% for all
positions
Oxygen Supine to semi-recumbent (45°) 19 80 – <48 hours One hour MRC grade ≤2 O
2
saturation on supine
91.9% versus semi-
recumbent 93.2%**
Oxygen Sitting (70°), sitting in chair, right
and left side lying (45°)
24 68.2 83% CI
17% PICH
<72 hours 15 minutes ESS
median 57.5
range (0–100)
Mean arterial O2 >95% for
all positions
Oxygen Sitting in chair, propped in bed,
supine lying, paretic and non
paretic side, right and left side lying
129 72 TACS 35%
PACS 36%
LACS 22%
POCS 5%
Unclassed 2%
<72 hours (median) 10 minutes MRC grade ≤2
(50% patients)
O
2
saturation ≥96% on
sitting in chair compared
to other positions*
Blood pressure Supine to sitting and standing 40 76 45% CI
55% Unclassed
<72 hours 5 minutes sitting and
standing
CNSS
median 90
range (70–105)
Increase change in DBP
from supine to sitting
(5 ± 7 mmHg)***
Increase change in MABP
from supine to standing
(3.0 ± 9 mmHg)*
Blood pressure Supine to sitting and standing 40 74 100% CI <72 hours 5 minutes sitting and
standing
CNSS
median 90
range (65–115)
Increase in MABP in sitting
(3 ± 9 mmHg)* and
standing (4 ± 10 mmHg)
Blood pressure Sit to stand hourly for 12 hours
each day for a week (trial group)
30 45–86 70% CI
3% PICH
27% Unclassed
<48 hours Tilting at 70° from
supine for 6 minutes
at one week
10% incontinent
66% hemiparesis
17% dysphasia
During tilting, fall in SBP of
8 mmHg in trial group
versus 19 mmHg in
control group. At one
week, severe disabled
patients (Katz’ Index,
F and G), trial group
20% versus 52% control
group***
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404
*P <0.05, **P < 0.03, ***P < 0.001, ****P < 0.0001. DBP, diastolic blood pressure; MABP, mean arterial blood pressure; MRC, Medical Research Council; ESS, European Stroke Scale; CNSS, Canadian Neurological Stroke
Scale; NIHHS, National Institute of Health Stroke Scale; TACS, total anterior circulatory stroke; PACS, partial anterior circulatory stroke; LACS, lacunar stroke; POCS, posterior circulatory stroke; CI, cerebral infarction;
PICH, primary intracerebral haemorrhage.
Table 1. continued
Variable Positional intervention No. Mean age Stroke type
Timing of
intervention Duration of each position Stroke severity Effects
......................................................................................................................................................................................................................................................
Blood pressure Supine to head elevation (15–30°) 18 61.2 100% CI <6 days 5 minutes >2/3 middle
cerebral artery
ischaemic stroke
Reduction in blood pressure
on head elevation
(90±1.6mmHg to
82.7 ± 1.7 to
76.1 ± 1.6 mmHg)****
Cerebral
perfusion
Supine to semi-recumbent (30–45°) 9 – 100% CI <48 hours Not presented Partial anterior
circulatory
stroke
Increase in cerebral
perfusion on semi-
recumbency (>50% change)
Cerebral blood
flow
Supine to head elevation (30°) 11 60 100% CI <48 hours 2 minutes NIHHS
median 8.7
range (4–20)
Increase change in cerebral
blood flow from head
elevation (51 ± 17.5 cm/s) to
supine (58 ± 19.3 cm/s)*
Cerebral blood
flow
Supine to head elevation (15–30°) 18 61.2 100% CI <6 days 5 minutes >2/3 middle
cerebral artery
ischaemic stroke
Reduction in cerebral blood
flow on head elevation
(72.87 ± 11.3 cm/s to
67.2 ± 9.7 cm/s to
61.2 ± 8.9 cm/s)****
Intracranial
pressure
Supine to head elevation (15–30°) 18 61.2 100% CI <6 days 5 minutes >2/3 middle
cerebral
artery ischaemic
stroke
Reduction in intracranial
pressure on head elevation
(1.6 ± 0.3 mmHg)
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405
dependent lung, thus aggravating intra-pulmonary shunting
[38]. Whether sitting stroke patients up immediately to
improve their oxygen saturation will improve short-term
neurological recovery is unknown and requires further eval-
uation. Larger studies should address the effects of different
positions on oxygenation within the first 24 hours of stroke
when the ischaemic penumbra is potentially salvageable as well
in other patients with co-existing cardio-respiratory disease.
The evidence that positional change after acute stroke
caused orthostatic hypotension was mixed and was con-
founded by stroke severity and the positions used. In addi-
tion, continuous blood pressure monitoring was not used
and therefore beat-to-beat haemodynamic measures were
not carried out. Ischaemic strokes as well as older people
have been shown to be associated with impairment of
orthostatic blood pressure control due to blunting of
baroreflex sensitivity resulting from sympathetic nervous sys-
tem hypofunction [7]. Orthostatic blood pressure responses
after acute stroke might give rise to significant reductions in
cerebral perfusion, resulting in neurological deterioration
[24]. Whether patients with orthostatic hypotension and
concomitant use of antihypertensive agents after stroke
should be managed more conservatively with initial supine
bed rest is unclear. The effect of the degree of vessel occlu-
sion and territory of stroke (anterior versus posterior) on
cerebral haemodynamics also needs to be studied.
The evidence that cerebral blood flow is at risk from
semi-recumbent positioning after acute stroke is equivocal.
Cerebral blood velocity was measured in these studies using
transcranial Doppler, which only provides non-invasive,
indirect measurements of cerebral blood flow [39]. The tra-
ditional approach of adopting moderate head elevation
between 30° and 45° in patients with large hemispheric
stroke is tempered by the findings of reduced middle cere-
bral artery velocity and cerebral perfusion in some studies
[14, 16]. Consequently the ischaemic penumbra may be
exposed to additional risk from reduction in cerebral blood
flow mediated through positional changes after cerebral
arterial occlusion. What is not clear is the natural history of
autoregulation following stroke and how this varies in
ischaemic and haemorrhagic stroke.
The practice of early head elevation to reduce intracra-
nial pressure for patients with stroke has been based on
studies of head trauma despite differences in pathophysiol-
ogy [40]. Although there was some evidence that intracra-
nial pressure was reduced in some patients with early head
elevation, this was at the expense of reduced blood pressure
and cerebral perfusion pressure [14].
Given that stroke is a heterogeneous condition, it is unlikely
that one single optimal position will maintain physiological
homeostasis in all patients. Systematic evaluation of individual
positions is required to assess potential risks and benefits [37].
It is likely that different positional strategies are required for
different phases after acute stroke, particularly in agitated and
confused patients. Positioning should be tailored to the individ-
ual pathophysiological situation. It is currently not known
which physiological parameters predict outcome or what is the
best target for therapy. If raised intracranial pressure is particu-
larly problematic in the supine position, then head elevation
may be appropriate, whereas if control of cerebral perfusion
pressure is the priority, the supine position may be an option.
Studies are required to examine the effects of positioning on
physiological parameters in a wider range of stroke patients
than previously studied, particularly at different stages of acute
stroke, to ascertain their prognostic significance.
Key points
• There are few published studies demonstrating the
effects of positioning after stroke on physiological
homeostasis.
• The evidence at present is not robust enough to guide
clinical practice for positioning.
• Further trials are required to investigate whether optimal
control of physiological parameters through different
positions will alter stroke outcome.
A. BHALLA
1,3,
*, R. C. TALLIS
2,3
, V. M. POMEROY
2,3
1
Department of Geriatric Medicine,
St Helier Hospital, Surrey, UK
2
Department of Geriatric Medicine, University of Manchester,
Manchester, UK
3
Division of Geriatric Medicine, St George’s Hospital Medical
School, University of London, London, UK
Fax: (+44) 0208 296 2421
Email: abhalla@sghms.ac.uk
*To whom correspondence should be addressed
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doi:10.1093/ageing/afi106
Religious attendance and 12-year survival
in older persons
SIR—In religiosity the question is how religion is manifested
in an individual life. Religiosity has many dimensions, e.g.
public–private, organisational–non-organisational, intrinsic–
extrinsic [1]. Most studies concerning religiosity and mortal-
ity have been carried out in the USA, and the measure of
religiosity usually used is the frequency of religious attend-
ance [2–4]. In US follow-up studies, those who attended reli-
gious events at least weekly had lower mortality rates than
those who attended less than once a week [2–4]. In a meta-
analysis of data from 42 studies examining the association
of religious involvement and all-cause mortality (total
n =120,000), religious involvement was associated with lower
mortality [5]. The association was stronger in the studies in
which women constituted the majority of participants, there
was inadequate control of other covariates of mortality, or
measures of public religious involvement were used [5].
The aim of this study was to describe the 12-year sur-
vival of older Finns according to the frequency of their
religious attendance and gender, and to analyse the associa-
tions between mortality, the frequency of religious attend-
ance, and the confounding variables describing age, marital
status, education, smoking, hypertension, coronary heart
disease, functional abilities, depression and number of
medications.
Methods
The data for this study come from a population-based
follow-up study of 1,080 persons (449 men and 631
women) aged 65 years or over, living in Lieto, a semi-indus-
trialised municipality in south-western Finland.
The frequency of religious attendance (times per year)
was asked about in the interview. In the USA, the attend-
ance variable is often dichotomised into once a week or
more versus less than once a week [2–4]. In our material
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