Analgesia
Patients often arrive at the
Emergency Department in pain, and painkillers are often used before a
definitive diagnosis is made. This is humane, and enables a thorough
examination to be per- formed: there is no reason to withhold analgesia.
Patients are asked to rate the pain out of 10, with 0
being no pain, and 10 being the worst pain they can imagine. This procedure is
repeated to gauge the effectiveness of the treatment and ensure the pain is
controlled.
In general, a patient’s reported pain is taken at face
value: ‘pain is what the patient feels’ and is treated as such. Patients
seeking opiates may fake pain, but this is rare.
Non-pharmacological analgesia
Splinting of fractures immobilises the bones, reducing
pain. A patient’s anxiety and pain makes them tense, which may make pain worse:
a calm, supportive atmosphere and excellent nursing care help to keep the
patient relaxed.
Nitrous oxide
Nitrous oxide (N2O)
combined with oxygen in a 1:1 mix in cylinders (Entonox®) is often used,
particularly out of hospital. It is a short-term analgesic, effective only
while the patient is breathing the gas, as it is rapidly cleared from the body.
This ‘laughing gas’ is generally very safe, but should not be used in patients
with a possible pneumothorax.
Paracetamol (acetaminophen) and compound analgesics
Paracetamol (acetaminophen)
is effective and safe and can be given orally, rectally or intravenously.
Compound analgesics consist of paracetamol combined with another analgesic,
usually low-dose codeine. They come in different strengths, the weaker of which
are sold without prescription. They are useful analgesics for patients to be
able to take home on discharge, but prescribing the constituent drugs
separately may allow more flexibility.
Moderate opiates
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Codeine is a common component of compound analgesics, and is effective but
tends to cause constipation. Oxycodone and dihydrocodeine are
more powerful variants of codeine, but offer little extra benefit, and have
high abuse potential.
•
Tramadol may be more effective than codeine. It has less abuse potential than
other drugs of comparable potency but should be used with caution in the
elderly.
Major opiates: morphine, fentanyl, pethidine
(meperidine)
Opiates induce a feeling of well-being: patients, while
still aware of the pain, are not distressed by it. Young patients with major
fractures may require large doses of morphine, as will opiate addicts who need
analgesia. Intravenous opiates are used because intramuscular absorption is
unreliable and the intravenous route enables analgesia to be titrated to
response.
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Intravenous morphine is the gold standard of Emergency Department analgesia. It is safe,
predictable and effective. Morphine is not as lipid soluble as other opiates,
so does not give a significant ‘high’. Morphine often causes mild histamine
release that should not be confused with an allergic reaction. The duration of
action of morphine is approximately 3 hours.
•
Fentanyl is a short-acting synthetic opiate that is particularly useful when
performing short procedures, as it is cleared from the body within 30 minutes.
•
Pethidine (meperidine) is quite lipid soluble and therefore sought after by
opiate addicts as it crosses the blood–brain barrier, giving a ‘high’. It
offers no benefits over morphine and should not be used unless a patient has a
definite allergy to morphine and there are no other alternatives.
Non-steroidal anti-inflammatory drugs Injectable non-steroidal anti-inflammatory drugs (NSAIDs), e.g. ketorolac,
are very effective in an Emergency Department setting. They are particularly
useful in patients with broken bones, colicky pain (e.g. ureteric
colic) and abdominal pain, but should be avoided in elderly patients or those
with active bleeding. An equally effective alternative is a suppository (e.g. indometacin,
diclofenac), which lasts for 16 hours.
Oral NSAIDs are useful as they can also be given to
patients on discharge. Ibuprofen is the least powerful, but has a
relatively benign side-effect profile.
Diclofenac and indometacin
are more powerful NSAIDs but at a cost of increased risk of side-effects.
Local anaesthesia and nerve blocks
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Lidocaine 1% is the local anaesthetic (LA) most often used for wound
management and is effective for 20–30 minutes without adrenaline, or for 40–60
minutes with adrenaline.
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Adrenaline mixed with lidocaine increases length of action and causes
vasoconstriction giving a ‘dry’ wound that is much easier to assess, clean and
close. Fear about using local anaesthetics with adrenaline in digits was
related to high concentrations (1 : 10 000); less than 1 : 100 000 adrenaline
is safe.
•
Bupivicaine 0.25% is a long-acting local anaesthetic, lasting for 6–8 hours.
Bupivicaine is highly protein bound: adrenaline does not increase duration of
action.
A safe maximum dose of lidocaine for wound infiltration
is 3 mg/ kg, but with adrenaline is 6 mg/kg. For bupivicaine the maximum dose
is 2 mg/kg. Local anaesthetic toxicity first causes perioral parasthesia, and
then fits and arrhythmias, and is treated by lipid infusion.
Nerve blocks can offer very effective analgesia, e.g.
digital and femoral nerve blocks. Bupivicaine and lidocaine can be mixed to
provide a combination of rapid onset and long duration of action. Local
anaesthetic can also be injected into joints, e.g. for shoulder dislocation.
A haematoma block can give good anaesthesia in minor
fractures e.g. Colle’s fractures (Chapter 15). The skin is carefully cleaned
with alcohol and chlorhexidine and then up to 10 mL of local anaesthetic is
injected into the fracture haematoma. After about 10 minutes reduction can be
performed.
Intravenous regional anaesthesia (Bier’s block)
Two intravenous cannulae are sited, one in the affected
limb. A double cuff is placed on the affected limb (usually the arm), which is
then lifted to exsanguinate it. The cuff is then inflated well above the
systolic BP and local anaesthetic, e.g. prilocaine, injected. Bupivicaine should
never be used for intravenous regional anaesthesia.
After waiting 5 minutes for the local anaesthetic to
have maximal effect, the operation, e.g. fracture reduction, is performed. The
cuff must not be deflated until at least 20 minutes have elapsed from injection
of the local anaesthetic to avoid a bolus of undiluted local anaesthetic
perfusing the heart, potentially causing asystole.
