Acute Pain - final version - Faculty of pain medicine - Australian and ...

6.3 INTRAMUSCULAR AND SUBCUTANEOUS ROUTES
IM
and
SC
injections
of
analgesic
agents
(usually
opioids)
are
still
commonly
employed
for
the
treatment
of
moderate
or
severe
pain.
Absorption
may
be
impaired
in
conditions
of
poor
perfusion
(eg
in
hypovolaemia,
shock,
hypothermia
or
immobility),
leading
to
inadequate
early
analgesia
and
late
absorption
of
the
drug
depot
when
perfusion
is
restored.
6.3.1 Opioids and tramadol
IM
injection
of
opioids
has
been
the
traditional
mainstay
of
postoperative
pain
management,
despite
the
fact
that
surveys
have
repeatedly
shown
that
pain
relief
with
prn
IM
opioids
is
frequently
inadequate.
Although
IM
opioids
are
often
perceived
to
be
safer
than
opioids
given
by
other
parenteral
routes,
the
incidence
of
respiratory
depression
reported
in
a
review
ranged
from
0.8
(0.2
to
2.5)%
to
37.0
(22.6
to
45.9)%
using
respiratory
rate
and
oxygen
saturation,
respectively,
as
indicators
(for
comparisons
with
PCA
and
epidural
analgesia,
see
Section
7;
for
comments
on
respiratory
rate
as
an
unreliable
indicator
of
respiratory
depression,
see
Section
4.1.3)
(Cashman
&
Dolin,
2004
Level
IV).
Single
doses
of
IM
morphine
10
mg
(McQuay
et
al,
1999
Level
I)
and
IM
pethidine
(meperidine)
100
mg
(Smith
et
al,
2000
Level
I)
have
been
shown
to
be
effective
in
the
initial
treatment
of
moderate
to
severe
postoperative
pain.
The
use
of
an
algorithm
allowing
administration
of
IM
morphine
or
pethidine
hourly
prn
and
requiring
frequent
assessments
of
pain
and
sedation,
led
to
significant
improvements
in
pain
relief
compared
with
longer
dose
interval
prn
regimens
(Gould
et
al,
1992
Level
III‐3).
The
quality
of
pain
relief
was
less
with
intermittent
IM
regimens
compared
with
IV
PCA
(Hudcova
et
al,
2005
Level
I).
The
placement
of
SC
plastic
cannulae
or
‘butterfly’
needles
allows
the
use
of
intermittent
injections
without
repeated
skin
punctures.
In
healthy
volunteers,
median
time
to
reach
maximum
serum
concentration
(T max )
after
SC
injection
of
morphine
was
15
mins
(Stuart‐Harris
et
al,
2000).
In
elderly
adults,
mean
T max 
after
a
single
SC
injection
of
morphine
was
15.9
minutes
and
the
rate
of
absorption
and
the
variability
in
the
rate
of
absorption
were
similar
to
those
reported
after
IM
injection
(Semple
et
al,
1997
Level
IV).
In
patients
given
a
second
and
same
dose
of
SC
morphine
5
hours
after
the
first,
it
was
shown
that
there
can
also
be
significant
within‐patient
variations
in
absorption
(Upton
et
al,
2006).
In
children,
there
was
no
difference
in
rate
of
onset,
analgesic
effect
and
side
effects
when
SC
injections
of
morphine
were
compared
with
IM
morphine
injections,
and
there
was
a
significantly
higher
patient
preference
for
the
SC
route
(Cooper,
1996
Level
II;
Lamacraft
et
al,
1997
Level
IV).
A
comparison
of
IM
and
SC
morphine
in
patients
after
Caesarean
section
reported
no
significant
differences
in
side
effects,
patient
satisfaction
or
pain
relief
at
rest,
but
lower
pain
scores
after
SC
administration
at
12,
16
and
20
hours
after
surgery
(Safavi
&
Honarmand,
2007
Level
II).
A
comparison
of
the
same
dose
of
morphine
given
as
either
a
single
SC
or
IV
injection,
showed
that
use
of
the
IV
route
resulted
in
more
rapid
onset
of
analgesia
(5
minutes
IV;
20
minutes
SC)
and
better
pain
relief
between
5
minutes
and
25
minutes
after
injection,
but
also
led
to
higher
sedation
scores
up
to
30
minutes
after
injection,
and
higher
PCO 2 
levels
(Tveita
et
al,
2008
Level
II).
However,
a
comparison
of
intermittent
IV
and
SC
doses
of
hydromorphone
(the
doses
adjusted
in
a
similar
manner
according
to
the
patients’
pain
scores
and
given
at
intervals
of
no
less
that
3
hours)
showed
no
differences
in
pain
relief
or
side
effects
over
a
48‐hour
CHAPTER
6
Acute
pain
management:
scientific
evidence
 157