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110 Phoon Ping CHEN, Christopher Ping Wing CHU, Edmond Kin Nam CHUNG
Liposome-encapsulated extended release morphine
via the epidural route provides analgesia that may
last for 48 hours after a single bolus injection. It
therefore avoids the need for an epidural catheter
and infusion pump for continuous infusion of
medications. However, significant side effects are
associated with this preparation of morphine [287].
e incidences of vomiting, pruritus and decreased
oxygen saturation are higher than placebo.
Epidural opioids
Epidural opioid provides analgesia without the
loss of sensory, sympathetic or motor function,
and therefore allows patients to ambulate without
orthostatic hypotension or motor dysfunction
usually associated with epidural local anaesthetic.
However, caution should be exercised when
using pethidine as it has local anaesthetic activity
which may result in sympathetic blockade and
hypotension [224]. Hypotension, nausea and
pruritus are more common with a larger dose of
opioid such as fentanyl [246]. Not surprisingly,
epidural opioids can cause respiratory depression
with a large enough dose.
Significant systemic and fat absorption occurs with
more lipophilic opioids like fentanyl and sufentanil.
When administered at the lumbar level for upper
abdominal and thoracic analgesia, fentanyl is not
more effective than when injected intravenously
[104]. Hydrophilic opioids such as morphine have
a slower onset but prolonged duration of action
when compared with a lipid soluble opioid (high
octanol partition coefficient) (Table 8.11). Rostral
spread allows morphine to be injected at the lumbar
levels for thoracic analgesia. However, spread to
higher levels may cause respiratory depression
some 6 to 12 hours later. Significant risk occurs in
the elderly or high-risk patient when the epidural
morphine dose is greater than 5 mg and when
other sedatives are concomitantly administered.
Patients who receive epidural or intrathecal
opioids should be monitored closely for 24 hours.
Although lipophilic opioids such as fentanyl and
sufentanil are deemed safe, rostral spread can occur
and respiratory complications have been reported
[37, 155, 302]. e recommended doses in Table
8.11 should be reduced for elderly and high-risk
patients [231].
Level of epidural insertion
Unlike epidural morphine analgesia, which may
be administered at a lower level, epidural local
anaesthetic administered at the level of the spinal
cord segment consistent with the surgical site
produces segmental spinal analgesia (Table 8.12).
In general, thoracic epidural analgesia is used
for major abdominal and thoracic surgery while
lumbar is given for surgery in the lower limbs
Complications of epidural
analgesia
Severe complications with permanent neurological
damage are rare in patients who receive epidural
Table 8.10 Drug prescriptions for epidural infusion
analgesia
• Bupivacaine 0.0625–0.125% + fentanyl 2–5
mcg/ml
• Ropivacaine 0.1–0.2% + fentanyl 2–4 mcg/ml
• Bupivacaine 0.0625–0.125% + morphine 0.05
mg/ml
• Morphine 0.05 mg/ml
Table 8.11 Common prescription for bolus epidural opioids injection in adult patients
Opioid Bolus dose* Onset (minute) Duration of analgesia (hour)
Morphine 2–5 mg 30–60 12–24
Hydromorphone 1.0–1.5 mg 20–30 6–12
Pethidine 25–100 mg 10–20 4–8
Fentanyl 50–100 mcg 5–15 2–4
Sufentanil 10–50 mcg 5–15 2–4
* Dosage should be reduced for elderly and high-risk patients.
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Acute Pain Management 111
analgesia. Nonetheless, all patients on epidural
analgesia must be monitored closely as other drug-
related side effects may be present. e adverse
effects of this technique are shown in Table 8.13.
Common side effects include hypotension, muscle
weakness, paraesthesia and urinary retention.
Segmental blockade of the area of surgical site and
pain, instead of blocking all dermatomes distal to
the surgical site, may reduce the incidence of side
effects. Compression of the spinal cord by either
epidural haematoma or abscess can present as severe
back pain, with or without reticular radiation,
and new onset of sensory and motor deficits. For
epidural abscess, fever may not always be present.
Suspicious cord compression warrants immediate
radiological investigation (e.g. magnetic resonance
imaging) and surgical intervention within 8 hours
after the onset of neurological signs.
Epidural analgesia is contraindicated in patients
on anticoagulant therapy, or with a coagulation
abnormality, allergy to drug to be administered,
and local skin or systemic sepsis. e risk-benefit
should be considered for epidural analgesia if
this technique is considered in patients with
thrombocytopenia of less than 100,000 x 109/L.
If epidural technique is considered for a patient
on prophylactic low molecular weight heparin, the
epidural procedure should be performed 12 hours
after the last dose. Similarly, the epidural catheter
should be removed at least 12 hours after the last
dose of low molecular weight heparin and the next
dose should be given no sooner than 2 hours after
catheter removal [116].
Epidural PCA
Using the concept of titrating the analgesic drug to
the desired analgesic level, PCEA is effective in both
surgical and obstetric settings [257, 266, 283]. One
Table 8.12 Recommended level of catheter
placement for postoperative epidural local
anaesthetic infusion (+ opioid) analgesia
Surgical procedures Epidural level
Thoracic surgery
Lung surgery,
oesophagectomy
Upper abdominal surgery
Gastrectomy, hepatobiliary
surgery, Whipple’s
operation
Nephrectomy, adrenalectomy
Lower abdominal surgery
Colectomy, intestinal
resection
Urological surgery
Cystectomy
Radical abdominal
prostatectomy, ureteral
reimplantation
Gynaecological surgery
Radical abdominal
hysterectomy, ovarian
cancer debulking
Pelvic exenteration
Orthopaedic surgery
Major joint replacement of
lower limb, amputation of
lower limb
Pelvis surgery
T4–6
T6–7
T7–8
T8–10
T8–10
T10–12
T8–10
T10–12
L2–4
T10–12
Adverse effects of epidural analgesia
Side effects
of local
anaesthetics
Motor blockade and impaired
proprioception result in
muscle weakness, prolonged
immobilisation, falls and pressure
sores
Autonomic nervous system
blockade causes hypotension and
urinary retention
Side effects
of opioids
Respiratory depression, nausea
and vomiting, pruritus, sedation,
urinary retention
Trauma to
dura, neural
structure
during
catheter
placement
Postdural puncture headache
Incidence of spinal cord injury/
nerve root damage causing
paraplegia or severe permanent
neurological damage: 0.005–
0.05% [66, 102, 135]
Catheter
migration
Migration to venous plexus,
subdural space or subarachniod
space may result in systemic
toxicity or high spinal block
Epidural
haematoma
Haematoma can cause spinal cord
compression and ischaemia
Incidence: 1 in 10,000 to 1 in
100,000 [178, 309]
Infection Incidence of epidural abscess:
0.015–0.05% [140, 291]
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112 Phoon Ping CHEN, Christopher Ping Wing CHU, Edmond Kin Nam CHUNG
of the advantages of PCEA is that less drug is used
when compared with continuous epidural infusion.
e choice of drugs for PCEA is either opioids
alone or opioids combined with local anaesthetics.
Table 8.14 shows some examples of regimens
used for epidural opioid PCA [231]. A mixture
of opioids and local anaesthetics may provide a
better dynamic pain score [298, 300]. Common
opioids employed in PCEA are fentanyl, sufentanil,
alfentanil and pethidine because of their relatively
high lipophilicity and rapid onset. Morphine is
a less popular choice because of its hydrophilic
nature and slower onset. ere is a wide variety of
regimes for PCEA with bolus only or combined
with background infusion. Wong et al. have found
that the PCEA mixture of ropivacaine and fentanyl
with a background infusion can lead to an increase
in side effects [305].
Outcomes with epidural
analgesia
Whether epidural analgesia can decrease
postoperative complications is controversial. A recent
study comparing lumbar epidural anaesthesia and
analgesia with general anaesthesia and postoperative
IV PCA in patients having total knee replacement
found that while pain relief is superior with the
epidural technique, there was no difference in
major outcomes [53]. e study, however, reported
a trend towards less postoperative complications,
and early ambulation and hospital discharge in
the epidural group. In high-risk patients, greater
positive effects are seen if epidural or continuous
regional analgesic techniques are used for pain relief
after major operation instead of parenteral opioids
[72, 262]. ere is evidence that postoperative
epidural analgesia improves postoperative
pulmonary function, attenuates neuroendocrine
responses to surgery, decreases myocardial oxygen
demand, reduces the incidence of thromboembolic
complications, improves intestinal motility and
significantly reduces pulmonary morbidity. Meta-
analyses show that thoracic epidural analgesia is
better than that of lumbar epidural in reducing
postoperative myocardial infarction and improving
bowel recovery [20, 131]. However, the recent
MASTER trial, which examined the effect of
epidural analgesia versus IV analgesia on the
outcomes of major abdominal surgery, could
not demonstrate any statistical improvement in
postoperative death, cardiovascular events, hepatic
failure, gastrointestinal failure, haematological
failure, renal failure and sepsis in the epidural
analgesia group; only respiratory failure was found
to be lower in the epidural group [237]. Overall, the
current evidence shows that epidural analgesia can
provide superior pain relief and decrease respiratory
complications in general [15, 29, 237].
Acute Pain Management
after Trauma
e treatment of pain in the trauma patient is
similar in principle to postoperative pain. Careful
evaluation of the patient is mandatory. In patients
with an impaired level of consciousness, airway
compromise and shock, immediate resuscitation
must take precedence. In the conscious patient,
once urgent surgical and neurological evaluations
have been performed, the provision of analgesia
during the acute phase is not contraindicated. In
fact, good pain relief improves patients’ co-operation
and facilitates evaluation. Treating injuries such
as pneumothorax, dislocations and fractures may
relieve the pain. Reassurance and information may
help allay anxiety and fear.
Table 8.14 Epidural opioids PCA
Background infusion (per hour) PCA bolus dose* Lockout interval (minute)
Fentanyl 20–30 mcg 10–30 mcg 10–15
Sufentanil 2.5–7.5 mcg 5 mcg 10–15
Alfentanil - 200–250 mcg 10–15
Pethidine - 10–20 mg 10–20
* Dosage should be reduced for elderly and high-risk patients.
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Acute Pain Management 113
e appropriate analgesic and its dosage must be
considered carefully in trauma patients who are in
shock. Patients with contracted blood volume are
often more responsive to a smaller dose of drugs.
Analgesic drugs should be titrated gradually and
carefully to effect. Non-steroidal anti-inflammatory
drugs are contraindicated in shock as there is a
significant risk of renal failure [40]. Intravenous
opioids are commonly used for the treatment of pain
in the trauma patient. However, pethidine should
be used with caution in shock as accumulation of
norpethidine may occur in the presence of impaired
renal function [273]. Even patients who are sedated
for cardiorespiratory support may be in pain from
their injuries and supplemental analgesics should
be considered. Most sedative and hypnotic agents
do not have analgesic properties.
In patients with traumatic pain, regional analgesia
techniques should be considered. Peripheral nerve
blocks as well as central neuroaxial blockade provide
excellent analgesia in appropriate cases. When
considering the latter, caution should be exercised
in the presence of hypovolaemia and hypotension
as sympathetic blockade may remove part of the
compensatory mecahnisms and lead to haemodynamic
instability. Peripheral nerve blocks have less
cardiovascular adverse effect, and in appropriate cases,
continuous infusion of local anaesthetic via a catheter
to the nerves supplying the injured site provides
excellent analgesia for many days.
Pain Relief in Burns
Pain in the burns patient occurs in partial thickness
burns where nerve endings are damaged and
become sensitised to produce pain. In full thickness
burns, nerve endings are completely destroyed and
the acute burn is supposed to be painless. However,
areas of burn described as full thickness are often
associated with some areas of partial thickness burn
and pain may be present. Non-viable insensate
tissue is often surrounded by regenerating areas
where pain may also arise. In addition, neuropathic
pain may be present in areas of nerve damage. In
fact, a combination of nociceptive and neuropathic
pain is common after burn injury and must be
treated appropriately. Often a multimodal and
multidisciplinary treatment approach is required.
Advances in burn care have led to a focus in an
aggressive treatment approach that changes
the course of burns. e use of temporary skin
substitutes in partial thickness burns reduces pain
and increases the healing rate, while the use of slow
release topical silver dressings markedly reduces
discomfort, need for dressing changes and results
in an overall decrease in infection [73].
Psychological factors usually play an important role
in burn pain. Pain in burns patients may also occur
during and after frequent dressing changes, wound
debridement, reconstructive surgery, skin grafting
and rehabilitative procedures. Recurrent wound
infections and multiple surgical procedures may
prolong the course of pain. Some patients continue
to experience pain in the scars. Dysaesthesias in the
scarred areas have been reported in up to 80% of
patients 1 year after the burn [52].
Acute burns
During the early resuscitative phase, patients with
severe burns may be in circulatory shock. e
maintenance of adequate airway, oxygenation and
cardiovascular resuscitation take precedence over
pain relief. Following resuscitation, acute burns
are associated with a hyperdynamic circulation
and increased metabolic rate. As the result of
altered pharmacokinetics and pharmacodynamics,
pain management in the burns patient must be
individualised. Burns patients must be evaluated
at regular intervals to assess the effectiveness of
treatment and for any side effects. In the initial
phase, simple measures such as cooling, covering
and immobilising the affected area may provide
analgesia [68, 99, 141].
Opioid is the mainstay of acute pain management
in patients with burns. Initial treatment involves
titration of small doses of IV morphine to avoid
cardiorespiratory depression. Intramuscular
injection is not recommended as there is variable
and delayed absorption especially in the early phase
of the burn. After the pain is controlled, analgesia is
maintained by IV morphine either as a continuous
infusion or PCA.
If applicable, IV PCA is a safe and effective method
of providing analgesia to patients with burns [51].
e advantages of PCA include avoiding any
delay in pain relief medication and allowing for
titration of dose to individual requirement. When
gut function has returned to normal, parenteral
opioid may be converted to oral morphine. Long-
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114 Phoon Ping CHEN, Christopher Ping Wing CHU, Edmond Kin Nam CHUNG
acting oral opioid may be appropriate when
severe nociceptive pain persists in the healing and
rehabilitative phases. Clonidine has been shown to
have an opioid-sparing effect when used in burns
patients [285].
Non-steroidal anti-inflammatory drugs are not
recommended during the acute phase of the burn
where there may be severe pain and significant
concerns for the drugs’ anti-platelet, gastrointestinal
and renal effects. However, they may be considered as
the burn heals and the severity of pain decreases.
Anxiolytics may be helpful in decreasing anxiety
and improving pain tolerance, but they must not
be used as substitute for opioids as they are not
analgesics [215]. Benzodiazepines such as diazepam,
midazolam and lorazepam are commonly used
for this purpose. Neuropathic pain, if present, is
often unrelieved by opioids and treatment with
antidepressants and anticonvulsants is effective
[172, 175]. In a small study, burns patients who
received gabapentin had lower opioid consumption
and pain scores compared with a retrospective
matched group of patients who received standard
therapy alone [60]
Poorly controlled burn pain is associated with
negative long-term psychological effects such as
depression, suicidal ideation and post-traumatic
stress disorder for as long as 2 years after the initial
burn injury [301].
Psychological techniques such as behavioural
modification, relaxation exercises, desensitisation,
imagery and hypnosis are useful in the management
of pain in patients with burns (see below). A
biopsychosocial model and multidisciplinary
approach using pharmacological and psychological
techniques can be individualised for each patient
to optimise pain relief [215]. Patient education and
reassurance are also effective in relieving anxiety
and pain.
Procedural pain in the burns
patient
Procedures such as dressing changes may be
associated with intense pain in up to 84% of
burns patients [8]. In extensive burn cases, general
anaesthesia is required for procedural pain.
Otherwise opioid is commonly used for pain
relief during these procedures. It is often given
intravenously or intramuscularly several minutes
before the procedure, with further supplementary
boluses administered as required during the
procedure. Lipid-soluble opioids such as fentanyl
and alfentanil are commonly used. ey can be
administered via PCA [225, 260]. Fentanyl may also
be administered via the intranasal [32, 90] and oral
transmucosal routes [252]. e short duration of
action of these opioids makes them appropriate for
short procedures in the burns patient. Remifentanil,
which is an ultra-short-acting potent opioid with a
short half-life and context sensitive half-time, may
be administered as a continuous infusion. However,
remifentanil should be used with caution and with
adequate monitoring during the procedure as
respiratory depression may occur [152].
Ketamine is also widely used as an analgesic agent
in burns patients. ere is evidence that ketamine
reduces hyperalgesia [121. is agent produces
intense analgesia with preservation of ventilation
and airway reflexes, and cardiovascular stimulation.
e dose often used for sedation and analgesia
is 0.2–0.8 mg/kg intravenously or 2–4 mg/kg
intramuscularly in unpremedicated patients. For
premedicated patients (e.g. given benzodiazepine),
a lower dose may be used. With a low dose,
emergence reaction is uncommon. Ketamine
when administered together with morphine has
been shown to have synergistic analgesic effects in
volunteers exposed to skin burn injury [245].
In less severe burns, self-administered Entonox
may provide safe and rapid pain relief. However,
the use of Entonox in an area where scavenging
is not available may lead to high level of nitrous
oxide pollution and expose the patient and staff to
its potential adverse effects. Other methods of pain
relief which have been reported in some case series
include IV lignocaine infusion [130], patient-
controlled propofol [55], lorazepam and morphine
combination, and topical application of morphine
infused silver sulfadiazine cream [159].
Hypnosis has also been used in treating burn
pain. Patients with burn injuries tend to be more
receptive to hypnosis than the general population
[216]. A study comparing hypnosis and stress-
reducing strategies found that the anxiety scores
were lower after hypnosis although there was no
significant difference in pain scores [96]. Recently,
virtual reality-based games have been shown to
provide analgesia with minimal side effects in
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Acute Pain Management 115
management of procedural pain in children with
burn injuries [67].
All burns patients who have been given sedative
medications such as opioid, benzodiazepine and
ketamine must be monitored closely for over-
sedation and respiratory depression.
Pain Relief in Obstetrics
Inadequately treated labour pain may result in
adverse physiological effects, such as increased
maternal oxygen consumption, hypoxaemia
and hypocarbia [48]. ese effects give rise to
abnormal uterine contraction, prolonged duration
of labour and may lead to decreased uteroplacental
perfusion, causing fetal hypoxaemia and acidosis.
Women experiencing painful and traumatic labour
without a feeling of control are more likely to
suffer from post-traumatic stress disorder [59] with
sexual avoidance, fear of childbirth, or postnatal
depression [14]. Adequate analgesia during labour
prevents these adverse effects and facilitates a
maternal state of mind conducive to maternal-
infant bonding. e goals of pain relief in obstetrics
are to provide effective and safe analgesia during
labour and delivery without interfering with the
process of labour and delivery.
A recent study found that women with severe acute
pain after childbirth (whether by Caesarean section
or vaginal delivery) have a 2.5-fold increased risk
of persistent pain and a three-fold increased risk of
postpartum depression compared with those with
mild pain. e increased risks were independent of
Caesarean section [83].
Anatomy of labour pain
Pain in the early stage of labour is primarily caused
by dilatation of the cervix and lower uterine
segment and from distension of the body of the
uterus (T10–L1). As the fetal head descends into the
pelvis, pain from the distension of pelvic structures
and pressure on the roots of the lumbosacral plexus
(L1–S4) occurs. Pain is also produced by stretching
of the perineum (S2–4).
Monitoring
During labour, both the mother and fetus must be
monitored closely to allow early detection of any
complications. When pain treatment is instituted,
the monitoring should include pain relief and
potential side effects of the treatment on the mother
and fetus (see patient evaluation above). Maternal
vital signs such as blood pressure and sedation
level are recommended, while cardiotocography is
recommended for fetal monitoring.
Methods of labour pain relief
Non-pharmacological methods
A number of different psychological techniques
such as psychoprophylaxis and hypnosis have been
used to control labour pain (Table 8.15). However,
these methods alone are often inadequate and
require supplementary pharmacological means for
pain relief. Psychoprophylaxis is a technique based
on information and education to reduce anxiety
and incorporates exercises to promote relaxation
and distraction. Continuous or one-to-one support
by either a midwife or trained layperson during
labour reduces analgesia use, operative delivery and
dissatisfaction. e benefit is greater if the support
person is not a member of the hospital staff and
is present from early labour, and if an epidural
analgesia service is not available [115].
Hypnosis administered during labour may lead
to a decreased requirement for pharmacological
analgesia, increased incidence of spontaneous
vaginal delivery and decreases the need for labour
augmentation and improves parturient’s satisfaction
Table 8.15 Methods of labour pain relief
Non-pharmacological methods
• Psychological techniques, e.g. hypnosis,
psychoprophylaxis
• Transcutaneous electrical nerve stimulation
(TENS)
• Acupuncture
Inhalational analgesia
• Intermittent self-administration of Entonox
• Volatile agents
Systemic opioid
• Intramuscular pethidine
Epidural analgesia
• Intermittent bolus injection
• Continuous infusion
• Patient-controlled analgesia
• Combined spinal-epidural analgesia
Intrathecal analgesia
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116 Phoon Ping CHEN, Christopher Ping Wing CHU, Edmond Kin Nam CHUNG
with pain relief [64, 263]. Acupuncture may decrease
the need for analgesia [263]. Transcutaneous
electrical nerve stimulation, on the other hand,
does not reduce labour pain, but there is evidence
for a weak analgesic-sparing effect [42].
Inhalational analgesia
Intermittent self-administration of Entonox (50%
nitrous oxide in oxygen) is often the first-line
method of analgesia in many obstetric labour units.
e administration of Entonox is a simple and safe
method [241], while the maternal and fetal effects
and impact on the progress of labour are benign [43,
297]. Although a safe method, Entonox inhalation
does not often provide adequate analgesia [43].
Parturients must be well instructed to inhale the
gas mixture before the onset of each painful uterine
contraction [292].
Subanaesthetic concentrations of volatile anaesthetic
agents such as trichloroethylene, methoxyflurance,
isoflurane and desflurane have also been used
in obstetric analgesia. ese methods have not
been popular because of their associated potential
adverse effects such as sedation, amnesia, pollution,
fire and explosion.
Parenteral opioid
Intramuscular administration of opioids is a
commonly used method of analgesia during labour.
It is simple and is administered by midwives. ere
is insufficient data to evaluate the comparative
efficacy and safety of any opioid administered
via the IM route in this setting [84]. Analgesia
is often inadequate with fixed dose intermittent
IM injections. is is largely due to variations in
individual patient response and the unfavourable
pharmacokinetic profile of intermittent IM
injections.
Other routes of opioid delivery including IV and
sublingual administration have also been used.
Intravenous administration has greater efficacy
than equivalent IM dosing [122]. Intravenous
opioid may be administered as patient-controlled
analgesia. However, systemic opioids in labour
often result in greater dissatisfaction with pain
relief than epidural and other regional analgesic
techniques [253]. In addition, systemic opioids
also decrease fetal heart rate variability, worsen
fetal acid-base balance [236] and increase the
number of infants requiring resuscitation at birth
or needing naloxone three- to four-fold when
compared with regional analgesia [108]. ese side
effects have limited the use of systemic opioids in
labour. Pethidine is still commonly used in many
centres but is contraindicated in pre-eclampsia as
the potential accumulation of norpethidine may
precipitate and potentiate seizure.
Epidural analgesia
Epidural analgesia is more effective in reducing pain
than non-regional methods of analgesia [118] and
is a popular method for labour analgesia. In many
obstetric labour units, the availability of a 24-hour
epidural analgesia service is considered a mandatory
standard of obstetric care during labour.
Epidural analgesia may be administered in several ways
(Table 8.15). e advantages of continuous infusion
epidural analgesia over intermittent “top-up” include
a more constant level of epidural local anaesthetic and
analgesia, and the possibility of reducing the number
of demands for “top-ups”. However close monitoring
is necessary to avoid over-infusion of local anaesthetic.
Low-dose (0.1%) bupivacaine-opioid infusions in
comparison with 0.25% bupivacaine bolus injection
reduce motor block and instrumental vaginal
delivery rate [58]. ere is no significant difference
in any outcome between the use of bupivacaine and
ropivacaine [109].
Patient-controlled epidural analgesia (PCEA) during
labour is an effective and safe alternative [81, 210].
Excellent analgesia and high patient satisfaction can
be achieved with a lower dose of analgesic. Patient-
controlled epidural analgesia without background
infusion reduces local anaesthetic use, motor
block and the need for anaesthetic intervention
compared with continuous epidural infusion [283].
Hypotension during PCEA is uncommon and
is usually associated with the initial loading dose
[100]. Various concentrations of bupivacaine from
0.0625–0.25% have been used in PCEA. e lower
concentrations are more commonly combined
with an opioid such as fentanyl or sufentanil [208].
Continuous background infusion during PCEA
is not beneficial [209]. e addition of opioid to
epidural local anaesthetic improves the quality and
duration of pain relief and reduces local anaesthetic
requirement, but it increases pruritus compared
with the equivalent dose of local anaesthetic
alone [160]. e combined infusion mixture also
improves maternal satisfaction [190].
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Acute Pain Management 117
Epidural pethidine is effective when administered
via a bolus dose, continuous infusion or patient-
controlled technique. It is more lipid-soluble than
morphine and therefore its onset and offset of
analgesic action are more rapid than morphine [197].
Epidural pethidine has been used predominantly
in the obstetric setting because morphine is not
suitable, while fentanyl has been shown to exhibit
significant systemic absorption when administered
via the epidural route. After Caesarean section,
epidural pethidine resulted in better pain relief
and less sedation than IV pethidine [206], but it
provided inferior analgesia when compared with
intrathecal morphine, despite causing less pruritus,
nausea and drowsiness [207].
Complications and adverse effects associated with
epidural analgesia during labour are uncommon.
Epidural analgesia during labour does not increase
the risk of long-term backache [303]. However,
when compared with systemic opioid, it may be
associated with a higher risk of maternal fever (4-
fold), probably related to an increase in temperature
associated with prolonged labour and nulliparity
[220].
Epidural analgesia has been implicated in many
instances affecting the mode of delivery, from
prolonged labour to increased need for instrumental
delivery or Caesarean section. However, studies
have now shown that although epidural analgesia
during labour is associated with longer duration of
labour and a higher rate of instrumental delivery, it
does not increase the Caesarean section rate when
compared with non-epidural labour analgesia
methods in nulliparous parturients [118, 153].
When studies which include induction of labour
are excluded, the increase in instrumental delivery
rate becomes insignificant [153].
Combined spinal-epidural
A combined spinal-epidural technique in labour
pain relief involves an initial intrathecal injection,
usually of a lipid-soluble opioid such as fentanyl
or sufentanil combined with low-dose bupivacaine,
followed by the insertion of an epidural catheter.
Combined spinal-epidural in comparison with
epidural analgesia reduces time to effective analgesia
and maternal satisfaction but increases the incidence
of pruritus [119]. Both techniques are associated
with similar obstetric and neonatal outcomes.
It has been shown in a Chinese population that
intrathecal bupivacaine 1.25 mg/fentanyl 25 mcg
produces satisfactory analgesia with minimal motor
blockade and hypotension [149]. Combined spinal-
epidural produces rapid and effective analgesia via
the intrathecal (“spinal”) component and provides
the flexibility of subsequently extending the
analgesic block via the epidural component. e
maintenance of motor function increases maternal
satisfaction [190] and may decrease the risk of
venous thrombosis and pulmonary embolism.
Although hypotension is not a significant problem
[254], loss of proprioception [186] may prevent safe
ambulation. e incidence of postdural puncture
headache in combined spinal-epidural may be
reduced by the volume of fluid injected into the
epidural space and compressing on the dural sac
[213].
Intrathecal opioid
Single-injection intrathecal opioid has been reported
to be as effective as epidural local anaesthetics for
the management of pain in early labour. Although
there was a higher incidence of pruritus, intrathecal
opioids did not have any effect on nausea or mode
of delivery [38]. Intrathecal opioid may also
increase the risk of fetal bradycardia (NNH=28)
and maternal pruritus (NNH=1.7) in comparison
with non-intrathecal opioid analgesia [165].
Pain relief after Caesarean section
Intramuscular opioid, IV PCA morphine, continuous
epidural infusion of local anaesthetic and opioid,
PCEA opioid with or without local anaesthetic and
single dose intrathecal opioid are often employed
as methods of pain relief after Caesarean section.
e management of post-Caesarean section pain
is not unlike that after major abdominal surgery.
However, for breast feeding mothers, analgesic
techniques which avoid or minimise the amount
of sedative drugs in breast milk are preferred. A
less sedating technique facilitates breast-feeding
and allows early bonding with the baby. Epidural
analgesia would be advantageous in this respect.
Table 8.16 Doses and drugs used in epidural
labour analgesia [9, 23, 30]
0.0625% bupivacaine with 2 mcg/ml fentanyl
0.1% ropivacaine with 2 mcg/ml fentanyl
0.0625% bupivacaine with 0.25 mcg/ml sufentanil
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118 Phoon Ping CHEN, Christopher Ping Wing CHU, Edmond Kin Nam CHUNG
Use of PCEA opioid has been reported to be more
effective than IV PCA opioid for pain relief after
Caesarean section [196, 229]. Although PCEA
pethidine is used in some centres, IV PCA pethidine
is not recommended because of increased risk
for neurobehavioural depression compared with
morphine [196]. Other regional techniques which
may be helpful in some patients and provide a short
period of pain relief include wound infiltration,
pudendal nerve block (S2–4), paracervical block
(T10–L1) and caudal block.
Acute Pain Management in
Older Persons
e choice of analgesic drugs for older persons requires
an understanding of age-related pharmacokinetics
and pharmacodynamic changes, and the impact of
coexisting diseases and concurrent medications [2,
13]. Other factors that make effective acute pain
management difficult in this group include altered
responses to pain, inability to co-operate with the
use of some pain relief techniques and difficulties
with pain assessment [161].
Pain assessment is more difficult in certain older
populations due to sensory loss (impaired vision or
hearing) [308] or cognitive impairment (dementia)
[21, 187, 212] and may result in under-treatment of
acute pain in this group. Different but appropriate
assessment tools should be considered for individual
patients when evaluating pain in the older person
[89]. e visual analogue scale (VAS), verbal
numerical rating scale (VNRS), verbal descriptor
scale (VDS), numerical rating scale (NRS) and
Faces Pain Scale have been reported to effectively
discriminate different levels of pain sensation in
older persons. e VDS was the most sensitive
and reliable [113]. Assessment of pain in non-
communicative patients is more difficult. Clinician
observations of facial expressions, behaviours and
sounds may accurately indicate the presence of
pain but not pain intensity in patients [163].
Drugs used in the management of acute pain in older
persons are described in Chapter 18. Pethidine,
but not morphine, fentanyl, or hydromorphone,
is associated with an increased risk of delirium in
elderly surgical patients and should be avoided
when possible [94]. Patient-controlled analgesia is
an effective method of pain relief in older people
[80, 97, 164], but elderly patients require some
degree of normal cognitive function to manage
it. Compared with IM morphine, PCA provides
better pain relief, less confusion and fewer severe
pulmonary complications in older persons [98]. In
addition, as opioid dose requirement is lower and
onset of action may be slower, the bolus dose and
lockout interval should be adjusted accordingly.
Older persons given epidural PCA (using a mixture
of bupivacaine and sufentanil) have been shown
to have lower pain scores at rest and movement,
higher satisfaction scores and more rapid recovery
of bowel function, compared with IV PCA [164].
However, IV or epidural techniques do not
influence cognitive function differently [94]. It is
important to note that epidural opioid requirement
also decreases as patient age increases [233]. In
addition, as the older person is more susceptible to
drug effects, caution should be given to check for
hypotension and excessive sedation.
Acute Pain Management in
Children
Pain in children commonly results from injuries,
illnesses and medical procedures [61]. Children
are a very heterogeneous group, with neonates,
infants, preverbal children, preschool-age children,
older children and adolescents at different stages
of development exhibiting variation in their
pharmacological needs and responses.
Safe and effective analgesic modalities for both
prevention and treatment of pain in the newborns and
children are available [24, 117, 188]. e choice of
analgesic, dose, route and method of administration
should be tailored to the individual child in
different pain situations. A better understanding of
the concerns above may improve pain management
in children. Acute pain management in children is
described in Chapter 19.
Patients with Substance Use
Disorder
Patients with a recent history of active drug abuse or
substance use disorder may not have reliable control
over their postoperative use of opioid. Concern
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Acute Pain Management 119
with opioid withdrawal often arises during the
perioperative period when opioid abstinence occurs.
e sympathetic response of opioid withdrawal
may be difficult to differentiate from under-treated
pain or stress, e.g. sepsis, hypovolaemia. Patients
with a previous history of substance abuse may also
be predisposed to re-emergence of abuse behaviour
with the stress of surgery and postoperative pain.
Behavioural problems are more common in patients
on methadone maintenance therapy (39% versus
5% control) [114]. Patients on chronic opioid may
be hyperalgesic and inadequate pain relief treatment
may contribute to behavioural problems.
Patients with substance use disorder who have
legitimate pain must not be deprived of effective
pain relief with opioid when indicated. However,
careful and frequent objective assessment is
required to minimise the chance of prescribing
opioid to a patient who is using it for reasons other
than pain. Specific drug abusive behaviour in the
postoperative patient should be recognised and
dealt with seriously (see Chapter 21). e medical,
ethical and legal consequences must be made clear
to the patient.
If difficulty is encountered during the course of
treatment, an early multidisciplinary intervention
involving the psychologist, psychiatrist, substance
abuse expert and the physician is recommended.
An institutional policy on opioid therapy for this
group of patients is useful. In some patients, drug-
seeking behaviours may be induced by inadequate
pain control and is referred to as pseudo-addiction
[294].
It is important to elicit a history of substance abuse
and distinguish the temporal characteristic of abuse
behaviour. Patients with a recent history of drug
abuse or on long-term opioid have a higher analgesic
requirement and may need a higher dose of opioid
[228]. ey may have opioid-induced hyperalgesia
[54, 114]. Patients with a distant history of drug
abuse may not require any treatment approach
different from non-abusers.
Before commencing opioid therapy, the treatment
plan, which follows institutional guidelines, must
be made clear to the patient to avoid excessive
negotiation. Clear criteria by which opioid dose
will be tapered and stopped and the consequence
of drug abuse behaviour must be defined.
Having defined the primary cause or potential
cause of the pain, non-opioid pain relief methods
should be considered as first choice. Where possible,
regional pain relief techniques with local anaesthetic
such as epidural analgesia, brachial plexus or other
peripheral neural analgesia should be considered to
avoid the need for opioid therapy. Concomitant
non-opioid therapy should be prescribed to either
reduce the opioid requirement or to replace the
opioid. Non-steroidal anti-inflammatory drugs
and paracetamol have an opioid-sparing effect.
Non-pharmacological therapy such as TENS,
cryoanalgesia and cognitive-behavioural therapy
may be helpful. Mixed agonist-antagonists may
precipitate withdrawal and should be avoided.
Patient-controlled analgesic opioid may be used
in substance abusers after major surgery when
significant pain is expected and when other
modalities of pain relief are not possible. However,
care should be given to appropriate lockout
intervals and hourly dosage limits, and that the
device is tamper-resistant so that the patient cannot
reprogramme the pump or remove any drug. A
higher bolus dose is often needed to achieve the
same analgesic effect as required for opioid-naive or
non-addicted patients.
References
Abboud TK, Zhu J, Gangolly, et al. Transnasal butorphanol: A new method for pain relief of post-Caesarean section
pain. Acta Anaesthesiol Scand 1991;35:14–8.
American Geriatric Society. e management of persistent pain in older persons. J Am Geriatr Soc 2002;50:S205–
S224.
American Society of Anesthesiologists. Task force on acute pain management. Practice guidelines for acute pain
management in the perioperative setting. Anesthesiology 2004;100:1573–81.
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