Chapter 3 - pain and its management Flashcards
what are two broad types of pain?
nociceptive pain
neuropathic pain
what is nociceptive pain?
Pain occurring from a defined lesion, that causes tissue damage leading to stimulation of nociceptors in somatic (bone and soft tissue) and visceral (capsular, hollow, cardiac) tissues.
what are the two types of nociceptive pain?
1) somatic pain - tissue damage or bone damage
2) visceral pain - lesion in or compression of hollow viscus, capsule, or cardiac solid organ
what is neuropathic pain?
inflammation, irritation or neural tissue compression, within the central or peripheral nervous system
what are the types of neuropathic pain?
peripheral - damage to the nervous system
allodynia - caused by stimulus that does not evoke pain e.g. feather or light touch
hyperalgesia - increased response to a normally painful stimulus
central - pain caused by damage to the spinal cord or brain
complex regional pain syndrome
sympathetic maintained neuropathic pain
what is breakthrough pain?
a transient exacerbation of pain in a person with otherwise stable well controlled background pain
what is background pain?
persistent pain of long duration managed with regular analgesia
what is spontaneous pain?
pain experienced prior to when the next dose of analgesia is due - if extra doses are required more than twice a day on a regular basis, then consider increasing the regular background analgesia dose
what is incident pain?
pain associated with an identifiable incident ie. procedural, involuntary act (cough) or voluntary i.e. walking
what is end of dose pain?
term used to describe pain that occurs in the period just before the next dose of analgesia is due
what is the socrates acronym for pain?
site onset character radiation association time course exacerbating/relieving factors severity
what are some pain assessment tools for patients with dementia?
DS-DAT (discomfort scale for dementia of alzhiemers type)
DisDAT (disability distress assessment scale)
dolopus-2 (behavioural tool for pain in the elderly)
Abbey pain scale
what is the WHO pain ladder steps?
step 1 - mild to moderate pain (NON OPIOID +/- ADJUVANT)
step 2- moderate pain (WEAK OPIOID + NON OPIOID +/- ADJUVANT)
step 3- severe pain (STRONG OPIOID + NON OPIOID +/- ADJUVANT)
what are the kind of drugs used in the first step of the WHO pain ladder?
paracetamol + NSAIDS
if not adequate in 24 hours proceed to the next step
what kind of drugs are used for the second step in the WHO pain ladder?
combination preparations i.e. cocodamol (paracetamol 500mg/codeine 30mg) + dihydrocodeine (30-60mg, 6 hourly) + low dose tramadol (50mg 6 hourly)
what kind of drugs are used for the third step of the WHO pain ladder?
oral 1st line - morphine
oral 2nd line - oxycodone
SC 1st line - diamorphine/morphine
SC 2nd line - oxycodone
what is the pharmacology of opioids?
block opioid receptors in the dorsal horn of the spinal cord, brain stem + peripheral nerves.
Opioid receptors - Mu, Kappa, Delta.
how do opioids cause a constipating effect?
act on opioid receptors in the myenteric and sub mucous plexus causing reduction in gut motility
what are the different types of opioid receptors?
mu, delta and kappa
what is the starting dose of morphine?
5-10mg IR 4 hourly
if elderly, frail or renal impairment can consider starting 1.25-2.5mg
what is the conversion factors from codeine to morphine?
codeine is 10 times weaker
to convert from codeine to morphine you divide by 10
i.e. if a patient is taking two co-codamol strong tablets four times a day (30/500), they are taking 240mg of codeine a day
so 240/10 = 24mg of oral morphine
how long does IR morphine last?
around 4 hours
how long does MR morphine last?
12 hours
how can you manage incident pain?
incident pain = pain associated with doing something i.e. movement or getting out of bed
- ensure medication timings are given 30 mins before the incident
- alternatively, can give fentanyl preparations as these act much quicker but are more expensive (i.e. oral transmucous (Actiq) or sublingual (Abstral, Effentora) or intranasal (Instantly).
how should you convert a patient from opioid to another?
calculate the equivalent opioid dose and reduce by 1/3, ensuring PRN’s are available
what is the conversion from PO to SC opioids?
divide by 2
what is the conversion of oral morphine to SC alfentanil?
divide by 30
what is the conversion of SC diamorphine from oral morphine?
divide by 3
list the opioids that can be given orally?
morphine oxycodone codeine tramadol methadone
list the opioids that can be given SC?
morphine
oxycodone
diamorphine
alfentanil
what are the two types of transdermal patches that are used?
fentanyl patch
buprenorphine
what dose of morphine should patients be on before rapid acting fentanyl patches are used?
when a patient is on 60mg/24hrs oral morphine AT LEAST
what are is an example of a trans mucosal fentanyl product?
actiq
what is an example of a sublingual fentanyl product?
abstral
what is an example of a nasal spray fentanyl product?
instantyl/pecfent
how should buccal/transmucosal/sublingual/nasal products be started?
at the lowest dose- regardless of background opioid usage
what is the practical benefit of using diamorphine?
comes in powder form and is highly soluble in water, so can be easily used in a CSCI where high doses of opioids are needed
when is alfentanil indicated?
renal failure - as does not accumulate in renal failure
metabolised in the liver and has inactive metabolites that are excreted via the kidney
why alfentanil not used as a breakthrough typically?
it has very short duration of action so may not work as effectively
when should transdermal patches be considered?
- in STABLE pain
- poor compliance
- difficulties swallowing/taking regular PRN’s
breakthroughs are needed until peak conc. levels are achieved. This delay also means patches cannot be used for titration and are only used for stable pain.
when are fentanyl patches usually changed?
72 hours
when are buprenorphine patches changed?
72-96 (transtec) hours, or 7 days (butrans)
what are some common SE with opioids?
drowsiness/sedation - usually only lasts for the first 48hrs
constipation - patients should be on a stimulant + softener ideally
nausea/vomiting - patients advised to be on regular antiemetic for first week (usually metoclopramide)
dry mouth
when a patients advised to drive when taking opioids?
avoid driving for 7 days after commencing/increasing opioid or within 4 hours of PRN dose
which anti-emetic is usually recommended in patients taking opioids and why?
metoclopramide - due to its central effects and impact on opioid included gut stasis
what can be advised for patients with dry mouth secondary to opioids?
chewing sugar free gum to stimulate salvia production, good oral hygiene, salvia substitutes or mouth washes
what can be prescribed for opioid induced constipation?
stimulant + softener (i.e. Senna + Sodium docusate)
peripherally acting u-opioid antagonist such as naloxegol tablets or methynaltrexone relistor
can also give targinact (oxycodone + naloxegol together) - however this is contraindicated in hepatic failure
what can increase the likelihood of opioid toxicity?
renal failure - accumulation of active metabolites
rapid upward titration
conversion from one opioid to another
development of acute infection
commencement of adjuvant such as pregabalin
symptoms of opioid toxicity?
myoclonic jerks pinpoint pupils - not most reliable confusion/agitation drowsiness hallucination/vivid dreams cognitive impairment respirator depression
what should be done in mild opioid toxicity?
reduce dose of opioid
rehydration
treat underlying cause
if agitation - give 1.5-3mg haloperidol orally or SC
what should be done in moderate toxicity?
if RR> 8/min + O2 sats normal + patient not cyanosed + easily rousable, omit the next dose (or stop infusion/patch), and adopt “wait and see” approach
when the next dose is due, re-titrated to the patients needs
what should be done in severe opioid toxicity?
if RR<8/min consider naloxone
stop opioids at current dose + re-titrate as needed
how should naloxone be given and what dose?
400mcg diluted in 10ml of 0.9 NaCl
administer 0.5mls IV ever 2 mins until RR satisfactory
further boluses may be required
if no iv access, can be given SC - 100mcg
consider infusion pump if multiple doses are needed
what is an example of an antidepressant used for pain?
amitryptilline (TCA) used in neuropathic pain
what is an example of anticonvulsants used for pain?
gabapentin
pregabalin
both used for neuropathic pain
what is an example of antispasmodic used for pain?
hyoscine butyl bromide (i.e. buscopan) for bowel colic
what is an example of a bisphosphonate used for pain?
pamidronate used for bone pain
there is evidence that bisphosphonates help with metastatic bone pain as they inhibit osteoclast activity
They should not be used first line, side effects include:
- hypocalcaemia
- renal failure
- osteonecrosis of the jaw
give three example of situations where nerve blocks are indicated?
solitary rib mets fractured NOF (lumbar plexus) pancreatic pain (coeliac plexus)
how long can it take for radiotherapy to improve bone pain?
3 weeks
what are some interventions for bone pain?
NSAIDs
pamidronate/zolendronate. - bisphosphonates
radiotherapy
what can be used to ease liver capsule pain?
pain due to liver mets stretching the peritoneum on the liver surface can respond to dexamethasone (4-6mg)
what can be given for muscle pain?
skeletal muscle relaxants such as diazepam 2mg TDS or baclofen 5mg TDS
what are some examples of complementary therapies used in pain?
acupuncture massage aromatherapy hypnosis spiritual healing reflexology art therapy relaxation techniques
what are some non-pharmacological interventions?
positioning catheterisation splinting exercise talking therapies diversional therapies psychosocial support
how does TENS machine work?
sensory nerves are excited by the transcutaneous electrical nerve stimulation and either the pain gate mechanisms and/or opioid system are also stimulated in order to “override” the pain
what are contraindications to a TENS machine?
pacemaker
recent haemorrhage
