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8/16/2019 Br. J. Anaesth.-1994-LEITH-552-8 (1)
1/7
British Journal of
Anaesthesia
1994; 73: 552-558
COMMENTARIES
Extradural infusion analgesia for postoperative pain relief
S.
LEITH,
R. G.
WHEATLEY,
I. J. B.
JACKSON,
T. H.
MADEJ AND
D.
HUNTER
Summary
W e describe 4-yr experience providing extradural
infusion analgesia in a distr ict hospital for treatment
of postoperative
pain.
A total of 770 patients
recovering from major surgery were treated on
general surgical wards between April 1989 and
March 1993. The results of a retrospective audit
showed
that pain
control,
assessed with both
a
visual analogue scale (VAS score (0-10 cm)) and a
verbal rating scale (VRS), was good. At rest, more
than 80 of patients scored pain as absent or mild
(VAS
score 0-3) during the first 24 h, with only 4
experiencing
severe pain (VAS score 7-10). On
movement, 50 of patients had good pain control
(VAS
score 0-3) while
20
of
patients experienced
severe
pain (VAS score 7-10). Minor
com plications
such as
emetic
sequelae
and
pruritis
were c ommon ;
these
conditions were mild and rarely required
treatment.
Hypotension (
8/16/2019 Br. J. Anaesth.-1994-LEITH-552-8 (1)
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Extradural analgesia
for
postoperative pain
553
between patients receiving PCA and extradural
analgesia.
To
minimize this risk
and the
time
involved in refilling the syringes, a new system was
introduced. The updated system used an ambulatory
PCA device (Bard Ltd, Crawley, W. Sussex, UK)
which included a 250-ml infusion bag. T his system
was again updated
in 1992 and now
extradural
infusion analgesia
is
maintained using ambulatory
Abbott Pancretec Provider pumps (Abbott Labora-
tories Ltd ) which use a 500-ml infusion bag prepared
by
our
pharm acy. T hi s system differs physically
from the PCA system, avoiding confusion, and
provides analgesia for up to 5 days w ithout refilling.
SOLUTIONS
Initially
the
extradural infusate consisted
of a
solution of 0.15% bupivacaine with diamorphine
5
mg in
50
ml
(0.01 % ).
The
dose
of
diamorphine
was reduced to 2.5 mg in 50 ml (0.005 % ) in patients
more than
65
yr of age.
In
1990, after the introdu ction
of the larger infusion bags, the dose of diamorphine
added to 0.15% bupivacaine was reduced and all
patients, irrespective
of
age, received d iamo rphine
at
the lower concentration of 0.005
(25 mg in
500 ml). T his change
was
designed
to
reduce
the
daily dose of diamorphine administered. The first
year's experience with
the
service demonstrated that
the lower concentration was effective in the majority
of patien ts. Infusion rates varied from 4 to 10 ml h
1
.
NURSING OBSERV TIONS
While patients were
in the
recovery room, nursing
observations (ventilatory frequencies, pain score
(0-3)
[2],
derma tomal level, arterial pressu re
and
sedation score (0-3)) were assessed at 15-min
intervals. In the ward, similar observations were
made by the nursing staff, hourly for the first 4 h and
then 4-hourly for the duration of the infusion. Each
set
of
observations
was
signed
for by the
recording
nurse. The extradural forms were assessed daily on
die A PT ward round
for
occurrence of com plications
and completeness of recording. The compliance of
die nursin g staff
in
recording
the
data was extremely
high (approaching 100 % ). In the first year,
1989-1990, sedation
was not
assessed
but a
simple
sedation score was included subsequently in the
postoperative observations. Each extradural chart
contained guidelines
for the
management
of
complications. Guidelines were available also on the
wards
and the
nursing staff attended in-house
training on the management of extradurals (See
appendix). A mem ber
of
th e
APT
was available
on a
24-h basis (including weekends) to give advice and
treatment if required. Bolus doses and changes in the
infusion ra te could be given only by a member of th e
pain team.
CUTE P IN TE M W RD ROUND
After referral
to the APT,
each patient receiving
extradural infusion analgesia was seen twice daily on
the morning and afternoon ward rounds for the
duration of treatment. The acute pain service (AP S),
which
has
been
in
operation since
1989
[2],
is
based
on the existing obstetric anaesthetic service and is
provided
by
three consultant a naesthetists,
an
acute
pain sister, and die on-call obstetric trainee an-
aesthetist.
An
audit
of the
entire workload
of the
A PS
for the
year 1989-1990 showed that approxi-
mately
30
of each con sultant session was spent on
the ward rounds and work related to the provision of
the service (both ex tradural analgesia and PCA). The
trainee anaesthetists spent
26% of
their working
time on acute pain work. A substantial part of the
time spent
by the
trainee anaesthetist
in the
year
1989—1990 was refilling and attending to problems
with
the
PCA p um ps which were also being used
for
extradural analgesia during this year. This pro-
portion of work has decreased over the past 3 yr widi
the increasing involvement of die nursing staff.
However, the increase in die number of patients
referred
to the
service
(660 in
1989-1990,
1362 in
1992-1993)
has
kept
the
workload
of the
trainee
anaesthetist constant.
The
assessment
at 24 h in-
cluded: (1) VAS score (0-10) for pain at rest; (2)
VAS score (0-10)
for
pain
on
movement;
(3) VRS
for satisfaction (poor, fair, adequate, good, excel-
lent); and (4) VRS for pain (absent, mild, dis-
comforting, distressing, excruciating). Both (2) and
(4) were introduced in 1990 after the first year's
experience with
die
service.
The
inclusion
of a
movem ent component improved the measurement of
efficacy without significantly increasing die workload
of the APT. In addition, the incidences of emetic
sequelae
and
pruritus were recorded.
Results
P TIENT D T
In die 4-yr period, April 1989 to March 1993, 770
patients received extradural infusion analgesia
on
general wards in York District Hospital (table 1).
T he num ber of patients receiving extradural infusion
analgesia increased from
150 in
1989-1990
to 226
in 1992-1993. The mean duration of treatment
increased from 55 to 80 h over die same period.
The majority of patients (65-82% ) were referred
to
the
service after general abdominal su rgery .
Non-
surgical referrals included pancreatitis
and
chest
trauma.
ASA status ranged from ASA I to IV with the
majority
of
patients
(73%) of ASA
I I -IV status.
There was an annual decrease in the percentage of
ASA
I
patients receiving extradural infusion
an-
algesia (40% in 1989-1990, 16% in 1992-1993).
Patients satisfaction with the method of analgesia
was high, widi more dian 88
of
patients regarding
it as adequate, good or excellent.
P IN SSESSMENT
VAS
SCORE
0 - 10 )
In the first year of the service, 75% of patients
receiving extradural analgesia scored pain as mild,
with only
7%
experiencing severe pain (table
2).
After the introduction in 1990 of separate VAS
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British Journal of Anaesthesia
Table 1
Patient data (mean (SD or range))
Male
Female
N o .
of patients
Age(yr)
Weight (kg)
Duration of treatment (h)
Dose of opioid mg/24 h (1989)
Dose of opioid mg/24 h (1990-93)
433
65(14-92)
70(13)
70 (1-240)
9.7
7.23
33 7
61(17-99)
63(13)
64(1-576)
9.7
6.8
Table 2
Twenty-four-hour pain assessment (VAS 0-10) at rest
(% patients). M989-1990 single VAS at 24 h
VAS score
1989-90 1990-91 1991-92 1992-93
0-3 (mild)
4—6 (moderate)
7-10 (severe)
75*
18 *
7*
91
9
0
93
6
1
83
13
4
Table 3
Twenty-four-hour pain assessment (VAS 0—10) on
movement (% patients)
VAS score
1989-90 1990-91 1991-92 1992-93
0-3 (mild) — 57 61 47
4-6 (moderate) — 36 23 32
7-10 (severe) — 14 16 21
Table
5 Patient assessment of pain severity (VRS)
(% patients)
1989-90 1990-91 1991-92 1992-93
Absent —
Mild —
Discomforting —
Distressing —
Excruciating —
21
38
29
10
2
25
41
19
11
4
26
25
32
14
3
Table 6
Incidence of vomiting in the first 24 h (% patients)
1989-90 1990-91 1991-92 1992-93
Females
Males
26
13
23
2
19
11
24
16
scores (0-10)
for
assessing pain
at
rest
and on
movement,
the
results showed that more than
80
%
of patients scored their pain as mild
at
rest (table
2),
but this declined to 50% on movement, with
16-21 % experienc ing severe pain (table 3). Mean
pain scores varied from 0.85 to 1.3 at rest and from
3.14
to
3.84
on
mov emen t (table 4). On assessing
the
severity
of
pain experienced
by
patients using
the
V R S , 50%
experienced
no
pain
or
mild pain
and
less than
4%
described dieir pain
as
excruciating
(table 5).
MINOR COMPLICATIONS
Hypotension
secondary
to
relative hypovolaemia was
a frequent finding;
34% of
patients
had a
systolic
arterial pressure
of
less tha n 100 mm
Hg at
some
time in the first 24 h (see discussion).
Mean ventilatory frequency
varied betw een 14
and
15 b.p.m ., with 2.6
of
patien ts w ith frequencies
of
8 b.p.m.
or
less.
Emetic sequelae. The
incidence
of
vomiting
in
females
was
(19-26 % ) compared with
males
(2-16 % )
(table
6).
Pruritis.
T he incidence of pruritus varied between
12 and 2 2% , but treatment was rarely required.
Prolonged block Two patients in the first year of
the study developed prolonged unilateral motor
block lasting 4—10 days which delayed mobilization
[2].
Both patients
had
lumbar extradural catheters
sited
for
pain relief after abdominal hysterectomy.
While formal assessment
of
motor block
was not
made, it was noted frequently on the APT ward
round that after hysterectomy, patients with extra-
dural infusion analgesia had difficulty mobilizing
because
of
motor block.
It has
since become
departmental policy
to use PGA for
pain control
after this type
of
surgery, avoiding the use
of
lumbar
extradural catheters.
Urinary retention
was
not
studied as most patients
receiving extradural infusion analgesia were
catheterized before operation.
MAJOR COMPLICATIONS (TABLE 7)
In the 4-yr period 1989-1993, four patients (0.52 % )
developed
severe respiratory depression
associated
with excessive sedation, airway obstruction and
hypoxaemia. One patient subsequently died (patient
N o. 3).
High block
One p atient with
a
thoracic extradural
catheter
in situ for
analgesia after laparotomy
de-
veloped hypotension associated with slurred speech
because of block to the third thoracic dermatome
(patient No. 5).
Two patients (Nos 6, 7) with major postoperative
intra-abdominal haemorrhage
were managed
in-
adequately as hypotension was attribu ted incorrectly
Table 4
Twenty-four-hour VAS 0-10 (mean (range)).
1989-90 1990-91
Rest 2.2*
Movement —
0.85 (0-6)
3.23 (0-10)
M989-1990 single 24 h VAS 0-10
1991-92
1.02(0-9)
3.14(0-10)
1992-93
1.3 (0-10)
3.84 (0-10)
1990-93
1.05(0-10)
3.40 (0-10)
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Table 7 Serious complications with extradural infusion analgesia 1989-1993 . *Patients 3, 6 and 7 died while receiving extradural analgesia
Patient
No. Age Sex Past history Operatio n
Problem
Hours Ventilatory Infusion rate
postop.
freq. (b.p.m.) (ml h
1
) Treatment Outcome Remarks
B
I
3
79 F Obstructive
jaundice, atrial
fibrillation
82 F Hypertension
Laparotomy for
carcinoma of pancreas
Rt. hemicolectomy Ca.
of colon, transverse
incision
73 F Reasonably healthy Laparotom y abandoned
because of inoperable
gastric carcinoma
75 F Parkinson's disease, Laparotomy. Long
obesity midlinc incision,
apendicetomy
76 M Reasonably healthy Laparotom y abandone d
because of inoperable
gastric carcinoma
Unrousable, sedation 51 10
score = 3, previous
scores = 1
8 h postop. sedation score 21 6
= 2, infusion rate I
from 6 to 2 ml h
1
.
Patient remained
drowsy, sedation score
= 3 at 21 h
Drowsy postop. 7 20
Remained drowsy
despite decreases in
infusion r ate. 7 h
postop. sedation score
-
2. AP = 90/60 mm Hg
30 h postop. sedation 30 20
score = 3, AP =
80/50 mm Hg. Previous
scores = 1
16 h posto p. AP = 16 14
75/45 mm Hg, slurred
speech, level = T3
81 M Inferior MI 18 yr Cholecystectomy
previously, atrial
fibrillation
7
Reasonably healthy Abdominal-perineal
resection
10 h post op. hypotensiv e 10
AP = 90/60 mm Hg
12 h postop. hypotensi ve 12
AP = 85/45 mm Hg
I.v. naloxone Good, no adverse
sequelae
I.v. naloxone Good, no adverse
sequelae
I.v. fluids, Good recovery
Resp. depression can
occur at any time
Some elderly patients
are very sensitive to
opioids
infusion
discontinued
initially. At 13 h
postop. cardiac arrest
PM = Basal
congestion/aspiration
I.v. naloxone, Good, no adverse
i.v. fluids sequelae
Overscdated pt who
became hypoxaemic
due to fluid overload.
Aspiration occurring
as part of terminal
event
Resp. depression can
occur at any time
Infusion
discontinued,
i.v. fluids,
ephedrine
Infusion
discontinued,
i.v. fluids
Infusion
discontinued,
i.v. fluids
Good response to
treatment but patient
developed CCF and
pul. oedema 2 h later.
Treated successfully
Inadequately
resuscitated. Cardiac
arrest 2 h later.
PM—Large intra-
abdominal
haemorrhage
Inadequately
resuscitated. Cardiac
arrest 4 h later.
PM—Large intra-
abdominal
haemorrhage
CCF due to fluid
overload and rebound
vasoconstriction on
stopping infusion
Other causes of
hypotension should
be suspected when
there is an inadequate
response to simple
measures
As above
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British Journal of Anaesthesia
to the effects of extradural block. A surgical cause
was not considered.
Discuss ion
Efficacy and safety are major considerations in the
provision of pain
relief.
This is particularly relevant
with the use of invasive techniq ues such as extrad ural
infusion analgesia where hypotension and respir-
atory depression are potential complications. It is
therefore important to demonstrate a high benefit to
risk ratio.
EFFIC CY
T he VAS score (0-10) at 24 h has been used w idely
to quantify postoperative pain and has been shown to
be an acceptable indication of a patient's pain after
surgery [6]. The visual analogue and verbal de-
scriptive score techniques have been shown to
successfully assess the sensory intensity of exper-
imental pain [7]. These two methods of pain
assessment were used for the 3-yr period 1990-1993.
The results showed that more than 80% of our
patients were comfortable at rest (mean VAS 1.05),
with 50 % (47-54% ) being comfortable on move-
ment (mean VAS 3.4). Using the VRS to assess the
quality of pain experienced by the patient, more than
5 0 % (51-6 7% ) described their pain as absent to
mild, with less than 2 0% (12-17 % ) describing their
pain as distressing or excruciating. Direct com-
parison of our results with similar studies is difficult
because of the different methods used for pain
assessment [8,
9].
The use of a local anaesthetic with
an opioid in the extradural space results in better
pain relief than one of the agents alone [10], while
minimizing the side effects associated with the
administration of each drug alone. Administration
by infusion also produces effects in a more gradual
manner.
Extradural infusion analgesia provides improved
postoperative pain control compared with parenteral
methods. In a study using i.m. analgesia, Kuhn and
colleagues [3] found that only 13 % of patients had
little or no pain while 40 % described pain as very
painful. Similarly, Owen, McMillan and Rogowski
[4],
using a pain rating scale, found that only 26 of
patients described pain as mild or absent while 37 %
rated pain as unbearable or severe. Jayr and
co-workers, [11] in a recent study comparing the
effects of extradural bupivacaine and opioids with
parenteral opioids (s.c. morphine 2.5 mg h~')j found
that pain control was significantly better in the
extradural group than in the s.c. group, especially
during recovery and on the first and second post-
operative days. The results of our first year's
experience with the APT [2] showed that patients
receiving extradural analgesia were more likely to
have no pain or mild pain than those receiving PCA
(chi-square, P
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Extradural analgesia for postoperative pain
55 7
results confirm the observation of Ready and co-
workers th at excessive sedation is a valuable clinical
sign of impending respiratory depression [16]. In
this series, extradural infusion analgesia tende d to be
used in older, high-risk patients with associated
cardiorespiratory disease, undergoing extensive sur-
gery, who were more prone to the depressive effects
of opioids. In patients receiving morphine orally or
parenterally (i.v., i.m., s.c.) the incidence of life-
threatening respiratory depression has been reported
to be 0.9% [17], which is higher than in our study.
Opioid-induced respiratory depression is not the
only hazard to the surgical patient. Myocardial
ischaemia secondary to tachycardia and hypertension
with poor analgesia may pose a greater risk to the
elderly surgical patient than the rare case of res-
piratory depression w ith extradural opioids. In high-
risk patients undergoing non-cardiac surgery, early
postoperative myocardial ischaemia is an important
correlate of adverse cardiac outcome [18].
Hypotension secondary to hypovolaemia from
inadequate fluid replacement and sympathetic vaso-
dilatation was a frequent finding: 34 of patients
devejoped hy potension of less than 100 mm Hg at
some time during the first 24 h. W hile Hob bs and
R oberts [8] recorded an incidence of only 2.6 % for
hypotension less than 95 mm H g, Jayr and co-
workers [11] found that 2 1 % of his patients with
extradura l infusion analgesia had hy potensio n of less
than 80 mm Hg which responded rapidly to treat-
ment. This is significantly greater (P
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558
British Journal of Anaesthesia
4. Arterial pressure
I F B P I S L E S S T H A N T H E N
I N C R E A S E I .V . I N F U S I O N R A T E
L I E P A T I E N T F L A T
A D M I N I S T E R O X Y G E N
BLEEP M TERNITY N ESTHETIST
5. Level = dermatome at which cold sensation
returns
Dermatomes: T5— Xiphistemum
T10—Umbilicus
T12—Pubis
If level is greater than then inform maternity anaesthetist
PROBLEMS
If there are any problems with the extradural please contact the
junior or consultant maternity anaesthetist.
N.B. Extradural analgesia is an effective method of pain relief
which relies on the adm inistration of local anaesthetic and opioid
drugs via a catheter in the extradural space. The settings on the
pum p are chosen by the anaesthetist with reference to the patient's
age, general condition and type of surgery. The settings should
only be altered by members of the acute pain team.
References
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3.
Kuhn S, Cooke K, Collins M , Jones JM , Mucklow JC.
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