Medical Chronicle November/December 2013 | Page 38

PAIN

Acute pain: The role of opioids
“By any reasonable code, freedom from pain should be a basic
human right, limited only by our knowledge to achieve it.”
DR ERIC HODGSON Chief Specialist Anaesthesiologist, Inkosi Albert Luthuli Central Hospital and Honorary Lecturer, Department of Anaesthesia, Critical
Care and Pain Management, Nelson R Mandela School of Medicine, University of KwaZulu-Natal
There has been strong evidence
of oligoanalgesia in acute pain
management since a landmark
article by Marks and Sachar in
1973. They were psychiatrists
routinely called on to evaluate
drug-seeking behaviour and
addiction in hospitalised medical
patients, and concluded that the
majority of the patients they
examined simply had severe
untreated pain. A recent review
article in 2013 confirms that
oligoanalgesia still exists today in
20%-75% of patients in hospital for
various diseases.

Usually, the cause of acute pain in
the emergency department (ED)
or surgical ward is obvious but
appropriate treatment is less well
understood. Pain arises from trauma
as a result of injury, disease or
surgery. Pain resolves as the injury
heals so that treatment is only
required for a short period.

Treatment of acute pain

Fear of side effects leads to
inappropriate withholding and/
or inadequate prescription of
pain medication as revealed by
the following studies:
• Less than 2% of long bone
fractures received analgesia
• Only 26% of children with
second-degree burns received
analgesia
• Less than 50% of patients
discharged were satisfied with
their pain management.

Treatment of acute pain is improved
by a systematic approach that
emphasises:

Monitoring - Measurement of
level of consciousness
A sleeping patient with a respiratory
rate >10/min does not need to be
woken to be asked if they are in pain.
If the respiratory rate is <10/min,
the patient should be roused and
not asked about pain but to assess
the requirement for administration
of naloxone and closer monitoring
in a monitored/intensive care
environment.

Rousability is best assessed by
the AVPU score:
A - Awake & Able to assess
V - Rouses to Verbal stimulus
P - Rouses to Painful (Noxious)
stimulus: Glabellar ta p,
Trapezius pinch, nailbed
pressure/jaw thrust. Not:
Sternal rub/nipple twist.
U - Unresponsive = General
anaesthesia

Measurement of pain level in
conscious patients: A simple
four-point score is most useful in
the ward/ER:
1 - No pain
2 - Discomfort NOT needing
added therapy
3 - Pain requiring therapy
4 - Severe pain despite therapy

• Anti-hyperalgesic drugs hyperalgesia is a prominent
feature of acute nociceptive pain,
especially dynamic pain. Adequate
treatment of dynamic pain with
antihyperalgesic drugs is essential
to allow adequate breathing and
coughing and to allow mobilisation
after injury.
• Paracetamol has few
contraindications, with IV
paracetamol providing excellent
initial pain relief.
• Non-steroidal anti-inflammatory
drugs (NSAIDs) have numerous
contraindications relevant to
acute pain management including:
dehydration/hypovolaemia,
renal dysfunction, wound and
gastrointestinal bleeding,
allergy and cardiovascular (CV)
thrombosis. CV thrombosis is
associated not only with the coxibs
(like rofecoxib) but also the nonaspirin NSAIDs such as diclofenac
and ibuprofen.
• Local anaesthetics are also
extremely effective for ED pain
management by various routes,
including infiltration, nerve and
plexus blocks.
• Analgesic drugs are drugs that
increase, rather than normalise, the

Appropriate drugs

38 MEDICAL CHRONICLE NOVEMBER/DECEMBER 2013

pain threshold. The most
commonly used
drugs in this
group are the
opioids analgesics. Appropriate
prescriptions
will use regular
antihyperalgesic
drugs, in the
absence of contraindications, to
minimise opioids
requirements.

Despite having many registered
compound analgesics with many
inappropriate drugs included, there
have been a limited number of opioid
analgesics available to South African
clinicians treating acute pain.
The selection was further
reduced by the withdrawal of SA’s
most widely used opioid analgesic,
dextropropoxyphene, due to concerns
regarding cardiac toxicity and use in
suicide attempts.
Codeine remains available but relies
on metabolism by cytochrome to
morphine by three enzymatic variants
as follows:
1. Ultra-rapid: Resulting in
potentially fatal levels of morphine
that may result in death as seen in a
child post-tonsillectomy in the US,
leading to a recommendation from
the FDA that codeine be withheld
from paediatric pain management.
2. Normal metabolism: Seen in the
majority of persons taking codeine,
resulting in morphine analgesia
with varying onset and duration.
3. Slow metabolism: Patients will
characteristically complain of
inadequate pain relief with codeine
but still experiencing constipation,
caused by unmetabolised codeine.

Analgesic drugs

Oxycodone was registered for use
in SA in 2012. Oxycodone provides
opioid analgesia without a ceiling
effect at clinically achievable
concentrations. Oxycodone has twice
the potency of morphine and has an
oral bioavailability of 60% as opposed

Oxycodone

to 30% for morphine. Oxycodone
dosing is thus 30%-40% of that
required for morphine.
A safe dose in healthy volunteers
is 0.2mg/kg of an immediate-release
preparation (Oxynorm®). The dose
can be repeated every 2-4 hours until
pain relief is achieved.
Where pain could be expected to
persist for more than 48 hours, a slowrelease preparation (OxyContin®)
may be used at a dose of 0.2-0.4mg/
kg 12 hourly, with immediate-release
oxycodone given at 2-4 hourly
intervals at a dose of 0.2mg/kg for
breakthrough pain.
OxyContin is formulated to release
40% of the dose immediately with
delayed release of the remaining 60%
from a matrix that remains intact and
may be passed in the stool. The matrix
also hinders the abuse of OxyContin
by preventing crushing and dissolving
of the oxycodone for illicit IV
administration. The FDA has recently
banned the manufacture of generics
without this tamper-proof matrix.
The aim of pain management with
oxycodone should be to administer
60%-80% of oxycodone required
as slow-release preparation, which
provides excellent pain relief,
without the euphoria that may
predispose to abuse.
There is no reason for patients
admitted to a modern ED
or surgical ward to suffer
inadequate pain management
with the many and varied options
available for relief.

Conclusion

References available on request.