13. Chronic Pain Flashcards
- A 56- year- old woman attends the chronic pain clinic with a history of chronic pain in her right arm. What is the best way to differentiate between chronic regional pain syndrome (CRPS) type 1 and CRPS type 2?
A. History B. Clinical examination C. Nerve conduction studies D. Budapest criteria E. Degree of resulting physical disability
A
CRPS type 2 requires a history of specific nerve injury for diagnosis.
CRPS type 1 may look and feel the same on clinical examination but can occur following any type of injury in the affected area.
Nerve conduction studies primarily test thick myelinated Aα and B fibres in mixed peripheral
nerves. They do not test small Ad and C fibres primarily affected in chronic pain.
The Budapest criteria must be met for diagnosis of both types of CRPS but cannot differentiate
between the two.
The degree of physical impairment is important in the ongoing management of
such patients but is not part of the diagnostic criteria for either condition
- A 40- year- old man is referred to the pain clinic complaining of gnawing pain in his right thigh. He is wheelchair bound following a spinal cord transection at T12 two years previously. He denies any recent injury and is systemically well. The most likely cause of his pain is:
A. A pathological pelvic fracture
B. A deep venous thrombosis
C. Psychosomatic pain
D. Neuropathic pain following the accident
E. Nociceptive pain following the accident
- D
Neuropathic pain is extremely common in those with spinal cord injury.
It is estimated to affect 70% of this group. It is thought to be due to sprouting of new nerve fibres below the level of spinal cord lesion. While essential for recovery, these neurones are hyperexcitable and their responses not always positive.
There is no history to suggest a pelvic fracture nor metastatic disease.
Psychosomatic implies no organic cause of pain but this patient has definite underlying causes.
However, psychological issues can arise from pain and input from psychology is very helpful in managing pain.
Nociceptive pain should not persist past 12 weeks
- You anaesthetize a 35- year- old woman for mastectomy and axillary clearance alongside your Consultant.
Your Consultant suggests you include nitrous oxide in your gas mix instead of your planned oxygen/ air/ volatile mix.
What is the best reason for using nitrous oxide in this patient?
A. To augment the postoperative analgesic regimen
B. To expedite recovery from general anaesthesia
C. To reduce the total opioid requirement
D. To reduce the incidence of chronic scar pain developing
E. To reduce the incidence of airway complications at induction and emergence
- D
Mastectomy is complicated by a high incidence of postoperative chronic pain including scar pain.
This is due to many factors but an important method of prevention is good intraoperative analgesia including use of nitrous oxide as an adjunct.
Nitrous oxide has fallen out of favour in recent years with trends towards using a ‘cleaner’ gas mix
of oxygen/ air/ volatile to reduce postoperative nausea and vomiting.
This must be balanced against the high incidence of chronic pain following this procedure particularly affecting younger female patients.
- A 64- year- old man with peripheral vascular disease requires a below knee amputation. He is taking regular paracetamol and 30 mg of morphine sulphate (MST) twice daily with Sevredol 10 mg 4 hourly
for breakthrough. What would be the optimal analgesic technique to manage stump pain postoperatively and reduce his chance of developing
phantom limb pain?
A. Intrathecal opioid
B. An epidural running for 48 hours before surgery
C. An infusion of IV ketamine intraoperatively
D. A perineural sciatic nerve catheter and with a local anaesthetic infusion running for 72– 96 hours
E. Pre- medicate with pregabalin and use a morphine patient- controlled analgesia (PCA)
device postoperatively
- D
It is important to treat acute pain effectively with good quality analgesia. This reduces both the
pathophysiological stress response and the patient’s psychological contribution.
Poor analgesia
in the immediate postoperative period predisposes to reduced functional recovery and the development of chronic stump and phantom limb pain.
Prolonged analgesia via continuous perineural blockade is the gold standard analgesic technique for
early management of stump and phantom pain.
It should be extended beyond 72 hours wherever
possible. It is safe, effective, opioid sparing with few side effects, and requires low levels of
monitoring.
The other options are all used, either alone or in combination, and provide reasonable
analgesia. Each has its own merits and side effect profile.
Studies of epidural analgesia have been disappointing. They have failed to show any reduction in the
incidence of chronic pain or phantom pain post amputation but in most studies the infusion was
stopped early after operation.
Aside from this they have a 10% failure rate, a risk of infection and other morbidities in an often diabetic or anticoagulated patient group.
- A 67- year- old man with peripheral vascular disease presents as an emergency for a right above knee amputation. He is currently on clopidogrel.
You administer a general anaesthetic including intravenous ketamine as part of your perioperative pain management. What is the principal site for the pharmacological action of ketamine?
A. GABA receptors B. Opioid receptors C. Monoaminergic receptors D. Cholinergic receptors E. NMDA receptors
- E
The principal action of ketamine is non- competitive antagonism of the NMDA receptor. It also
interacts with all the other receptors mentioned.
Perioperative ketamine has been shown to reduce
the incidence of persistent post- surgical pain.
- You anaesthetize a 38- year- old woman for mastectomy and axillary clearance. Which analgesic technique is best to reduce the incidence of
chronic scar pain postoperatively?
A. Thoracic epidural B. Paravertebral block C. Cryo- analgesia to intercostal nerves perioperatively D. PCA morphine E. Lidocaine infusion via wound catheter
- B
The intensity of acute pain is a consistent predictor of post- surgical chronic pain (PSCP).
PSCP is most common in areas where nerves are damaged during surgery and those which are richly
innervated (e.g. chest wall).
Paravertebral block has been shown to be effective in minimizing chronic scar pain. A thoracic epidural may also help but would confer more risks for similar benefits in mastectomy.
Identifying intercostals nerves to preserve them may help (though not mentioned in the answer) but
cryo- analgesia at the time of surgery makes subsequent chronic pain worse.
PCA morphine and lidocaine wound infusion work well in the acute phase of postoperative pain but have no impact on the development of chronic pain.
Lidocaine does however reduce the incidence of PSCP but only when given intravenously.
- A 36- year- old patient has chronic scar pain following mastectomy. She is to be given a new analgesic patch to try. Which method of delivery will
maximize any placebo effect gained from the
treatment?
A. Ask GP to prescribe and patient to apply herself
B. Refer to practice nurse for information and first application
C. Refer to nurse- led pain clinic session for information and first application
D. Prescribe the most expensive brand of the patch
E. Give patient written information detailing the efficacy of the patch in trials
- C
Placebo effect is common and occurs in addition to the therapeutic effects of intervention. It is largely contextual and therefore is maximized when given by more senior members of staff in more specialized areas.
The actual treatment given is less important than the therapeutic encounter, its rituals, symbols, and interactions which surround the application or use.
Branded medicines have a larger placebo effect than generic versions, injections have a greater effect than tablets, and administration by a doctor confers more placebo effect than when given by a nurse.
- Which of the following methods is best used for measuring pain in a 90- year- old patient with dementia who has sustained a fractured neck
of femur?
A. Verbal descriptor score B. Visual analogue score C. Numerical rating scale D. Wong– Baker faces scale E. Behavioural assessment
- E
Acute pain can be assessed by any unidirectional method but options A, B, C, and D require intact
cognition to understand the questions asked, the details of the scale, and to know how to respond.
Behavioural assessment is the most useful: observing facial expression, movement, or lack thereof,
and the response to same. Be aware that this type of assessment, proxy reporting of pain, is less accurate than personal (self ) reporting of pain by the patient and usually underestimates the amount of pain actually being experienced by the patient. It does not take into account the affective and cognitive aspects of pain which cause distress too.
Communication barriers may be due to
dementia or confusion and when cognition is intact but the patient is dysphasic or aphasic.
- Which of the following gives the most accurate description of the way each tool is used to assess pain?
A. The McGill Pain Questionnaire provides an objective measure of pain
B. The McGill Pain Questionnaire measures sensory, affective, and cognitive aspects of pain
C. The HADS (Hospital Anxiety and Depression Scale) is useful in assessing acute pain
D. The HADS uses numerical sub- scales to assess each question
E. The Brief Pain Inventory is most relevant to cancer pain
- B
To assess pain it is necessary to consider the affective and cognitive aspects of pain, as well as the
more obvious sensory aspects. There is no objective measure of pain.
The HADS score, though useful in the overall assessment of pain as described above, does not
assess the sensory aspect most relevant in acute pain.
The Brief Pain Inventory was developed
to assess cancer pain but is now thoroughly validated for use in persistent pain from any source
or cause.
- You consent a patient for caudal epidural steroid injection on the interventional pain list. Which combination of risks best reflects what you would discuss with the patient?
A. Failure, infection, nerve damage, risk of dural puncture headache
B. Failure, infection, worsening of pain afterwards, constipation
C. Infection, worsening of pain afterwards, impotence, and urinary retention
D. Failure, infection, worsening of pain afterwards, leg weakness post procedure
E. Failure, infection, worsening of pain afterwards, delayed onset of any benefit
- E
The patient must be informed of the risks of failure of the block (both technical and clinical), and infection.
Nerve damage should be mentioned in context showing its rarity.
Interventions in chronic pain can make the patient’s pain worse in the acute phase. This is due to the needle causing additional trauma in a painful area. It should settle after five to seven days.
The dura and cerebrospinal fluid end around S2 so are unlikely to be breached during caudal catheter placement.
Constipation, urinary retention, and impotence are all side effects of lumbar sympathectomy and
are not relevant to caudal injections.
- Which of the following groups of characteristics describes the patient who is most likely to suffer from chronic pain?
A. Male, 75 years of age, retired, low educational background
B. Female, 75 years of age, retired, high educational background
C. Male 50 years of age, unemployed, low educational background
D. Female, 50 years of age, unemployed, low educational background
E. Female, 45 years of age, unemployed, high educational background
- D
There are specific risk factors for developing chronic pain. These include being female, being of
a younger age (chronic pain is much reduced in the elderly), being unemployed, and being from a
low educational background. Answer D contains four risk factors. No other option contains more than 2.
12. A 45- year- old man presents to clinic with a diagnosis of chronic headache. Extensive investigation has found no abnormal results. He has tried a variety of drugs which have failed to help the pain. He asks about non- pharmacological therapies. Which would be the best intervention to try first? A. Acupuncture B. Pain management programme C. Botulinum toxin injections D. Greater occipital nerve block E. TENS machine
- A
When considering interventions, it is important to consider the degree of invasiveness, the
associated risks, and the evidence for potential benefit.
Acupuncture is minimally invasive and
there is some evidence of its efficacy in treating chronic headache (and low back pain).
Greater occipital nerve blocks are no longer recommended as there is little evidence supporting their efficacy.
Repeat blocks also introduce risks of infection, nerve damage, and increase the patient’s
lifetime steroid load. Botulinum toxin is considered an effective treatment and may be considered
It is more invasive than acupuncture. A Pain management programme may be beneficial when all
treatment options have been exhausted. A TENS machine could be used by the patient but there is
no evidence it improves pain.
- You review a 46- year- old woman in the pain clinic. She describes a right sided burning pain confined to the area supplied by T6 following an episode of shingles six months previously. You diagnose post- herpetic neuralgia (PHN) The best treatment to control her pain acutely is:
A. Regular diclofenac and co- codamol B. Famciclovir C. Gabapentin D. Lidocaine patch E. Nortriptyline
- C
PHN is a self- limiting condition and management is directed at controlling the pain while waiting for
the condition to resolve itself.
A multimodal approach to the analgesic regimen will provide additive effects though efficacy will vary between individuals.
Lidocaine patches work well but the effect is transient, lasting only 4– 12 hours.
The analgesic effect of nortriptyline and other tricyclic antidepressants is very slow and a trial of around three months is required to determine whether there is any benefit.
Gabapentin is effective and works quickly. It is also effective in treating the sleep disturbance that
commonly co- exists so would be the first line therapy in this case.
Opioids, while not mentioned
here are only occasionally indicated for cases with extreme pain.
Paracetamol and NSAIDs alone have not been shown to be effective in PHN although they may be
included as part of a multimodal approach. Famciclovir is an antiviral drug which, if given at the start
of the episode of shingles, reduces the incidence of chronic pain developing after it has resolved.
- On the acute pain round you review a 56- year- old man who had a midline laparotomy yesterday for bowel obstruction. He has a thoracic epidural running at 6 mL/ hour with 0.1% levobupivacaine and 2 μg/ mL
fentanyl.
He complains of severe abdominal pain which got much worse this morning. On examination his epidural block is to T6. The most likely reason for his pain is:
A. The epidural has become disconnected overnight
B. He has been asleep all night and no pain assessments have been carried out
C. The rate of epidural infusion is too low
D. He has suffered an anastomotic dehiscence
E. He has a low pain threshold
- D
Acute pain has complex aetiology and is highly variable between individuals.
Pain is always subjective and the severity is, as the patient states. The rate of the epidural infusion is on the low side but on testing, his block is adequate to cover the wound.
Regular pain assessment improves acute pain
control but is not necessary overnight if the patient is sleeping. This would be more relevant if the
epidural was a patient- controlled bolus system.
The history of any pain is always of fundamental importance including its onset, spread, character,
and associated features. Complaints of pain despite a seemingly adequate spread of epidural
analgesia should always be taken seriously. The patient gives a recent history of acutely worsening
pain over a short period which suggests something has happened around that time, such as an intraabdominal
catastrophe.
- A 24- year- old female with chronic back pain attends the chronic pain clinic seeking improvement in her pain.
She reports a pain score of 9/ 10.
She takes tramadol 100 mg four times per day, ibuprofen 400 mg three times daily, pregabalin 300 mg twice daily, and amitriptyline 25 mg daily,
yet remains unable to work due to pain. What is the next best step in the management of her pain?
A. Commence MST/ sevredol B. Increase dose pregabalin C. Refer for pain physiotherapy D. Refer for spinal cord stimulation E. Refer to orthopaedic surgeons for surgery
- C
Pain physiotherapy would be the next best thing to offer this patient. This requires engagement
from the patient. Pain psychology may have a beneficial role here too.
A short course of strong opioids may be helpful to facilitate participation in pain physiotherapy but
there is no evidence for their use in the long term. Any opioid trial should be finite with no dose
escalation. Opioids can lead to addiction and dependence and have many side effects. This patient
is already on a large dose of tramadol and the maximum dose (600 mg daily) of pregabalin.
