Page 22 - Medicine and Surgery

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18 Chapter 1: Principles and practice of medicine and surgery

and constipation are predictable, patients should be of their analgesia. A loading dose is given first, then the
alerted to these and provided with means by which these patient presses a button to deliver subsequent small bo-
can be treated early. luses of intravenous opioid. The PCA pump has a lock-
out time usually set at 5–10 minutes, which allows time
The WHO ladder of analgesia for each dose to take effect before another dose can be
The World Health Organisation analgesia ladder is a given. This prevents respiratory depression due to acci-
method for choosing appropriate analgesia depending dental overdose by the patient repeatedly pressing the
on the severity of pain. It was originally developed for button. If the patient becomes overly sedated, the de-
cancer patients but is useful for many types of pain. Ini- livery of opioid ceases. If patients are not adequately
tially, analgesia may be given on an as needed basis, but analgesed, the bolus dose is increased. This system is
if frequent doses are required, regular doses should be not suitable for patients who are too unwell or confused
given, so that each dose is given before the effect of the to understand the system and be able to press the button.
previousdosewearsoff.Acombinationofdifferentdrugs
often improves the pain relief with fewer adverse effects.
Local and regional anaesthetic
After analgesia is initiated, if it is ineffective at maximal
Local anaesthetic is useful perioperatively. It is often
dose, the next step on the ladder is tried. Certain drugs
givenaround the wound or as a regional nerve block
are contraindicated or used with caution in patients with
to provide several hours of pain relief. Spinal anaesthe-
co-morbidities. Postoperative patients may descend the
sia is useful for surgery of the lower half of the body.
ladder, as severe pain is expected immediately after tissue
Postoperatively, continued analgesia using an epidural
damage and this pain reduces as healing takes place.
catheter to administer boluses or a continuous infusion
STEP 1 (Mild pain): Non-opioid analgesia is used, such
is useful. Usually a combination of local anaesthetic with
as paracetamol or an NSAID. These may be given
an opioid is used. The advantage of epidural analgesia is
orally or rectally.
that there is good pain control with a lesser risk of the
STEP 2 (Mild to moderate pain): Weak opioids such as systemic side-effects of opioids. However, complications
codeine, dihydrocodeine or tramadol orally or intra-
include hypotension due to sympathetic block, urinary
muscularly are added to regular paracetamol or an
retention and motor weakness. Patients require special-
NSAID.
ist care and monitoring on a ward accustomed to the
STEP 3 (Moderate to severe pain): Strong opioid anal-
management of patients with epidurals.
gesia such as morphine or diamorphine is used.
Co-analgesics
Modes of delivery of opioids
These are other drugs that are not primarily analgesics,
The oral route is preferred for most patients, but for
but can help to relieve pain. In particular, neuropathic
patients unable to take oral medication or for rapid re-
pain is relatively insensitive to opioids; drugs such as an-
lief of acute pain, intramuscular or intravenous boluses
tidepressants and anticonvulsants are more effective, e.g.
are faster acting and more suitable. The disadvantage of
amitryptiline or gabapentin. Tramadol is a weak opioid
boluses for continued pain is that often there is a delay
that has some action at adrenergic and serotonin recep-
between the patient experiencing pain and analgesia be-
tors and so may be useful for combination nociceptive
ing given. In intensive care settings or terminal care a
and neuropathic pain. Muscle spasm often responds to
continuous infusion by a syringe driver may be appro-
benzodiazepines.
priate, but with any continuous delivery system there is a
riskofaccidentaloverdose,soregularmonitoringofpain
score, sedation score and respiratory rate is needed. In Non-pharmacological treatment
stable patients with severe ongoing pain, a transdermal In addition to prescribing analgesia, it is important to
patch may be suitable. These release opioid in a con- consider other methods that relieve pain, such as treat-
trolled manner, usually over 72 hours. ing the underlying cause, immobilising a painful joint
Patient-controlled analgesia (PCA) is a system by with a splint, mobilising joints for stiffness and treating
whichthepatientscandeterminethefrequencyofdosing concomitant depression. Acupuncture, local heat or ice,