Pain control Flashcards
Define pain:
unpleasant sensory or emotional experience associated with actual or potential tissue damage or described in terms of such damage
Define nociception:
unconscious afferent response to traumatic or noxious stimuli
NOT pain as this is a conscious experience
What are the types of pain fibres?
C fibres = unmyelinated = transmit dull, poorly localised ill defined sensation
A delta fibres = myelinated = transmit fast, sharp, well localised sensation- synapse with 2nd order neurone in dorsal horn = plasticity = gate control theory of pain
What is encompassed in total pain?
physical = pain due to disease location, other symptoms (nausea), physical decline + fatigue
Social = relationships, families role, work life, financial problems
psychological = grief, depression, anxiety, anger, adjustment to condition
spiritual = existential issues, religious faith, meaning of life and illness, personal value as a human
When treating pain what is important to know?
knowing what has/hasn’t worked previously
- dose, compliance, side effects, suitable route and duration
What are the steps of the WHO pain ladder?
Step 1: paracetamol / NSAID
Step 2: codeine, dihydrocodeine, tramadol
Step 3: morphine, oxycodone, fentanyl, buprenorphone, hdyropmorphone
doses depend on patient and previous opioid hx
What are examples of adjuvants?
anti-depressants anti-convulsants smooth muscle relaxants steroids bisphosphonates radiotherapy / chemo or surgery
What is somatic pain?
Aching, often constant
dull or sharp
often worse on movement
well localised
musculo-skeletal e.g. bone metastases, arthritis, muscle sprain and spasm, fracture
How is somatic pain often treated?
NSAIDs
depends on degree of pain - often NSAIDs and opioids aren’t enough for bone metastases -consider RT
What is visceral pain ?
constant or crampy
aching
poorly localised
referred
abdominal organs e.g. cancer pancreas, bowel obstriction, liver capsule stretch, bladder spasm
How is visceral pain treated?
often responds well to opioids - although colic responds better to smooth muscle relaxants
also consider steroids e.g. dexamethasone 4-8mg daily for tumour oedema
What is neuropathic pain?
pain arising as a consequence of a disturbance of function or pathological change in a nerve or the nervous system
What is steady dysasethetic neuropathic pain like?
burning, tingling
constant, aching
squeeing, itching
e.g. diabetic neuropathy, post-herpetic neuroapthy
What is paroxysmal neuralgic neuropathic pain like?
stabing, shock like, shooting, lancinating
e.g. trigeminal neuralgia, nerve root compression
What signs suggest neuropathic pain?
- ” I just can’t describe it”
- burning and numbness
- allodynia
- cancer pain is often mixed
What are the treatment options for neuropathic pain?
partially respsonsive to opioids and to NSAIDs
other options:
- anti-depressants e.g. TCAs
- anti-convulsants e.g. gabapentin
- steroids - esp if loss of function
Beyond WHO ladder: ketamine, lidocaine, methadone
What is background and breakthrough pain?
constant nature
- needs long acting / regular analgesics
and then breakthrough pain requires additional analgesa
breakthrough = pain that occurs despite regular doses of modified release morphone = 1/6th of total daily morphine
What is incident pain?
e. g. pain precipitated by movement
- difficult to treat as may be very severe but short lived typically (45 mins or less)
- usual analgesics don’t work quickly enough but then analgesics may help but prolonged duration often leads to side effects
What is the usual treatment for incident pain?
traditional treatment = oral liquid morphine (10mg/5ml)
transmucosal opioids may be faster acting e.g. fentanyl lozenge
newer alternatives = sublingual and buccal fentanyl tablets/nasal spray
What are the different forms of morphone?
Oral morphine - immediate release -> oramorph liquid -> sevredol tablets = rapid onset 20-30 mins - duration 4 hours
- slow release
-> MST
-> Zomorph
= given eveyr 12 hours
What are the side effects of opioids?
constipation nausea sedation respiratory depression myoclonic jerks others: miosis, dry mouth, confusion, visual hallucinations, itching, euphoria
How can you treat the main side effects of opioids?
constipation = co-prescribe laxative permanently nausea= co-prescribe anti-emetic PRN first 5-7 days hallucinations = stop/reduce /switch - Drowsiness = assess - may pass/reduce but advise may need to temporarily stop driving
Define tolerance:
normal physiological phenomenon in which increasing doses are required to produce the same effect
Define physical dependence:
normal physiological phenomenon in which a withdrawal syndrome occurs when an opioid is abruptly discontinued
Define psychological dependence:
pattern of drug use characterised by a continued craving for an opioid which is manifest as compulsive drug seeking behaviour leading to an overwhelming involvement in the use and procurement of the drug
What are the symptoms of opioid toxicity?
intractable nausea hallucinations drowsiness myoclonic jerks = very suggestive opioid neurotoxicity pinpoint pupils depressed respiration
metabolites of morphine can accumulte and lead to renal failure
When are opioid patches useful?
if pain is stable difficulty taking oral meds compliance reduce medication load side effect profile = renal impariment, consitpation may be better with patches
e.g. fentanyl patches or buprenorphine
What are syringe drivers?
used when patient is unable to take oral medication - terminal stage, vomiting, bowel obstruction
What are the advantages o syringe drivers?
portable
relatively non-invasive
combine several drugs
