next topic we're going to look at is
the possibility of postural hypertension
so we're considering complications of
immobility on the cardiovascular system
we've considered deep venous thrombosis
we consider pulmonary emboli
now they're going to consider postural
hypertension
now hypotension means low blood pressure
hypo
low tension to do with blood pressure
and it's hypotension which depends on
the posture of the patient
so in postural hypertension you've
probably experienced this yourself if
you've been lying down
and all of a sudden you jump up you go
dizzy for a while
maybe only for 10 seconds or so but you
feel a bit dizzy when you jump up
and the reason for that is that your
blood pressure has been a lower when
you're lying down
then when you jump up your brain is
uphill from your heart
and the hearts start working harder and
there has to be peripheral
vasoconstriction
to increase the blood pressure so your
brain is properly perfused
and the reason you go dizzy is because
there's not enough blood going to your
brain and you can feel that in your in
your head that makes you feel dizzy
quite a nasty feeling actually normally
uh when i get it i lie down again until
it passes off
so postural hypertension low blood
pressure as a result of the position
you've been in
now when you jumped up onto your feet
you've probably only been lying down for
half an hour
but if you've been lying down for a long
period of time
then it would take much longer for your
blood pressure to get going again
so that you don't feel dizzy when you're
sitting up again
so patients that have been immobile for
a while can actually feel quite dizzy
just when they sit up
never mind when they stand up and we
have to get them used to this
gradually again so it can build up the
blood pressure
so we're thinking about postural
hypotension
due to decreased effect of gravity on
the patient's extremities
one cause anyway that means they get
vasodilation
which reduces the blood pressure which
is okay when they're lying down
but the blood pressure is then no longer
enough to perfuse their brain when
they're upright
so when the patient first sits up or
changes from the horizontal to the
vertical position
results in a hypoperfusion of the brain
which may cause dizziness and may cause
nausea
now as well as the peripheral
vasodilation
there's probably lots of muscle tone in
the arterial system
so when we sit up normally we have
arterial vasoconstriction
which which increases the blood pressure
but if someone's been lying
down for a long period of time this
muscle tone in the arterial system is
probably lost
therefore the arterials can't respond
they can't contract
to increase the blood pressure
and the effect seems to be worse when
patients are sat up
passively by you rather than sitting
themselves up
using their active muscular system
so postural hypertension let's think
about how we're going to prevent this
so if possible we can allow the patient
to uh
be propped up by pillows so they're not
lying flat for much of the time
it's a good idea not to lie your
patients flat unless you have to
allow the patients to become upright as
regularly as possible
and get up slowly in several stages
allow them to get up slowly so don't
take them from lying flat sitting up
straight away
allow them to get up on their own in
stages
and in fact this is a good idea with
anyone who's been ill or in bed or even
some old people
when you're getting them out of bed just
give them a minute to sit on the edge of
the bed
before you get them up then it gives
them time to
increase the heart rate time for
peripheral vasoconstriction to occur to
get the blood pressure up a bit
the patients have been immobilized for a
long period of time that's going to take
hours to maybe even a day or so to get
them up not just minutes as it does in
our case
when when you've been in your mobile for
a short period of time and of course
this can be prevented by minimizing the
period that the patient is immobile for
this is true with all these
complications the less time the patient
is immobile
the less of these complications are
going to occur
and the less severe these complications
will be
so postural hypertension
next complication we're going to look at
is possible increased
cardiac workload
now cardiac workload may increase when
patients are lying flat it shouldn't
occur otherwise because when the
patients are lying flat
the distribution of the circulating
blood changes
so in mobile patients that are lying
flat the distribution of the blood
changes
and the way it changes is that some of
the blood
supply that would normally be in the
legs
moves to the thorax 11 of legs blood
supply moves to the thorax
this is when patients are lying flat in
other words venous return from the legs
is increased that's really what i'm
saying
therefore venous return to the heart is
increased because there's more blood
venous blood in the thorax
and if more blood goes back to the heart
the heart is then obliged
by the frank starling reflex to pump
more blood out
so increasing cardiac workload when the
patient is lying
flat so keep patients set up as much as
possible
now immobility causes an increase in
heart rate
and as we've said this is because the
circulatory system is working less
efficiently
it's the exact opposite of someone who's
athletically fit when the heart rate
slows down
so in deconditioning due to immobility
there's an increase in heart rate
and subsequent exercise will increase
the tachycardia
because the patients are very unfit
therefore any effort
is going to cause a tachycardia
in other words there's a deconditioning
there's a loss of endurance
which may take some time to recover from
so let's just review what we've said
there to clarify it
there's an increasing cardiac workload
when patients are lying flat because
there's an increase in venous return
that's one point the other point is when
patients are immobile they become
unfit therefore the heart has to work
quicker because it's working less
efficiently
and the circulatory system is less
efficiently working less efficiently
so high rate has to increase as opposed
to when someone is fit when heart rate
decreases
so there's an increase in heart rate and
then when the person does exercise
because they become so unfit the heart
rate increases fairly significantly to
facilitate that exercise
because the circulatory system is
working inefficiently
let's think about the prevention now of
these complications
well obviously as we've said limit
the time of immobility as much as
possible
do not immobilize your patients unless
you've got a good rationale
for doing so however if someone has been
immobilized for some period of time
they need grassic gradual progressive
rehabilitation
so they can regain their fitness just
like if you want to start running
marathons or doing a lot of strenuous
exercise
you've got to build up to fitness over a
period of time
and it's the same with patients who've
been immobilized to return to a normal
level of fitness
it takes time to to progressively
rehabilitate them so it's a good idea
just to keep an eye on
pulse rate and blood pressure during
times of immobility
and as the patient start to recover to
regain their
fitness