Pain Flashcards
Measure pain?
Pain scale 1-10
• faces for children
Non-opioid analgesia
- Paracetamol
- NSAIDs/COX-2 inhibitors
- Topical treatments
- Capsaicin
- Lidocaine
Opioids analgesia for mild/mod pain
- weak opioids - limited potency at mu receptor
- Codeine
- dihydrocodeine
- tramadol
Opioid analgesia mod/severe pain
- strong opioids
- high potency at mu receptor
- Morphine
- diamorphine
- oxycodone
- fentanyl
Strong opioid eg
- morhpine
- diamorphine
- oxycodone
- fentanyl
Weak opioid eg
- codeine
- tramadol
- dihydrocodeine
considerations surrounding opioid analgesia
- metabolism
- SE
- renal function
- dependence/addiction
opioid SE
- Constipation
- N&V
- drowsiness
- drowsiness
- sedation
- respiratory depression
Adjuvant therapy
- anti-epileptic drugs
- antidepressants
- dexamethasone for bone pain in palliative care
- non-pharmaceutical strategies
non pharmaceutical strategies for pain relief
- physiotherapy
- exercise
- psychological therapy
- acupuncture
chronic pain classification?
- musculoskeletal
- neuropathic
- non-specific persistent pain
- chronic headache syndrome
Musculoskeletal pain eg
- mechanical pain
- osteoarthritis
- lower back pain
- rheumatoid arthritis
Lower back pain/ sciatica
- low back pain that is not associated with serious or potentially serious causes
- sciatica - leg pain secondary to lumbosacral nerve root pathology
- worldwide lower back pain causes more disability than any other condition
Sciatic is?
leg pain 2º to lumbosacral nerve root pathology
Lower back pain/sciatica treatment
- continue normal activities
- group exercise programs
- manual therapies
- psychological therapy
- oral NSAID
- if NSAID CI weak opioid +/- paracetamol for ACUTE pain only
- surgical treatments
Surgical treatments for lower back pain/sciatica
- radiofrequency denervation
* spinal cord stimulation
Sciatica specfic treament
- epidural injections (local anaesthetic + corticosteroid),
* spinal decompression surgery
Ostheoarthritis
- most common form
- breakdown of cartilage in the joints, commonly hips, knees, hands, lower back and neck
- symptoms
symptoms of osteoarthritis
- joint pain during and after activity
- initial limited range of of motion
- clicking or cracking in joints
- swelling around joints
- muscle weakness around joint
- instability of the joint
osteoarthritis treatment
- exercise and manual therapy
- weight loss if overweight/obese
- paracetamol +/- topical NSAID
- topical capsaicin
- if the above are ineffective, consider oral NSAID/COX2 inhibitor
- intra-articular corticosteroid
Rheumatoid Arthritis what?
- autoimmune disease
- inflammation of synovium
- leads to erosion and deformation of the affected joints
- can affect other tissues
Rheumatoid arthritis symptoms
- symmetrical pain and swelling of small joint in hands and feet lasting >6weeks
- spread to larger joints
- joints may be warm and tender
- stiffness on waking/after inactivity
- fatigue, fever and loss of appetite
Treat to target monotherapy
- methotrexate
- leflunomide
- sulfasalazine
treat to target in mild or palindromic disease
hydroxychloroquine as alternative to MTX/leflunomide
treat to pain step up strategy
• + DMARD (methotrexate) in combination where dose titration hasnt achieved remission/low disease activity
DMARD eg
- methotrexate
- leflunomide
- sulfasalazine
- hydroxychloroquine
If no response to conventional DMARD….
- biologial DMARDs
- infliximab
- adalimumab
- sarilumb
biological DMARD eg
- upadacitinib
- sarilumb
- adalimumab
- etanercept
- infliximab
inadequate response to biological DMARD
• rituximab
neuropathic pain types
- peripheral neuropathy
- complex regional pain syndrome
- central pain
Neuropathic pain treatment
- amitriptyline
- duloxetine
- gabapentin
- pregabalin
- if one not work, try other.
- tramadol for acute rescue therapy
- consider capsaicin cream for localised pain
- carbamazepine for management of trigeminal neuralgia
Carbamazepine for ?
management of trigeminal neuralgia
non specific persistent pain treatment
- supervised group exercise program
- psychological therapy
- acupuncture
- antidepressants - paroxetine
- NOT recommend = paracetamol, opioids, NSAIDs, antiepileptic drugs, benzodiazepines
non specific persistent pain antidepressant eg
- duloxetine
- fluoxetine
- paroxetine
- citalopram
- sertraline
- amitriptyline
AVOID in non specific persistent pain
- paracetamol
- opioids
- NSAIDs
- antiepileptic drugs
- benzodiazepines
Cluster type - chronic headache
- idiopathic
- intermittent
- unilateral eye
- lasts >2h
- > 3days per week
Analgesic overuse - chronic headache what symptoms?
- bilateral
- constant
- last 8 to 24hr
Tension-type - chronic headache
- 1º headache
- bilateral eye
- constant
- last 8-24hr
- 7-9 days/month
Post-trauma - chronic headache
- bilateral
- constant
- last 8 to 24h
- 7 to 9 days/month
Chronic migraine - chronic headache, type? Lasts? Side?
- 1º migraine
- bilateral
- last 1-4h
Acute pain what?
- sudden onset
- <6 months
- spontaneous insult/trauma
- planned surgery
- spontaneous/trauma
- childbirth
Spontaneous/trauma eg
- broken bones
- burns and cuts
- tooth ache
- headache
Management of Acute pain
- OTC analgesia
- Paracetamol
- NSAIDs
- low dose weak opioids
- non-pharmacological
Palliative care is ?
• an approach to improve quality of life of pt and their families
Palliative care = end of life?
NO
Pain control in palliative care
- WHO pain ladder
- morphine commonly used as strong opioid.
- no max dose of morphine
Opioids long acting & breakthrough
- one long acting opioid/ prolonged release formulation
- With short acting opioid/ immediate release formulation for breakthrough pain
- breakthrough analgesia 1/10 to 1/6 of daily long acting dose
- opioid equivalences when switching drug
In acute pain, breakthrough analgesia should be…?
1/10 to 1/6 of daily long acting dose
Syringe drivers
- SC infusion
- drugs & diluent set to infuse over (24h)
- concern over stability of the contents.
PCA - what is it
Patient controlled Analgesia
drug delivery PCA
- loading dose (by nurse)
- top ups (pt controlled)
- lock out to prevent overdose
- adjuncts for management of toxicity
Drug deliver PCA monitoring the pt
- pain scores
* AVPU - alert, voice, pain, unresponsive
AVPU in PCA monitoring
- Alert
- Voice
- Pain
- Unresponsive
Advantages PCA
- Pt in control
- Predictable pain relief
- Active participants in their recovery
- Faster alleviation of pain
- Pt doesn’t have to wait for pain relief – reduced distress in waiting for pain relief
- Less time consuming for nurse
- Easy to titrate dose according to response or need of pain control
Disadvantages PCA
- Patient not responsive to use
- May be scared of self administration
- Poor dexterity
- Reduced mobility
- Potential to increase length of stay
- Liable to abuse
- Patients lack of understanding on how to use PCA
- SIDE EFFECTS
Loading dose in PCA is?
dose on initiation
Commonly in PCA
morphine or fentanyl
Bolus in PCA is?
dose administered on triggering
Lockout in PCA is ?
min time between doses
background rate in PCA is?
continuous infusion on top of which bolus dose given
Monitoring during PCA use
- BP
- Pulse
- Respiratory rate
- sedation
- pain score
- nausea
- hourly for 1st 8hr from initiation
- 2hrly for 48h following
- 4hrly until discontinuation
PCA SE
- N&V
- Pruritis
- Respiratory disease (RR <8)
- Excessive sedation
PCA SE N&V treatment
• cyclizine 50mg TDS
PCA SE Pruritis treatment
• Chlorphenamine 4mg TDS PO
PCA SE Respiratory depression treatment
- O2
- Turn off PCA
- Monitor O2 SATs
- Consider naloxone 200-400mcg IV
PCA SE Excessive sedation treatment
- Remove PCA handset
- Monitor O2 SATs, pain, sedation scores
- Ensure adequate non opiate analgesia prescribed regularly
Post operative paracetamol
offered post operatively unless CI
• weight >50kg - 1g QDS
• weight <50kg - dose reduction
Post operative analgesia Oral NSAID
- Ibuprofen immediately post operative pain (except fractured hip)
- IV NSAIDs not common
- careful age, co-morbidities
Post operative pain oral opioid
- if pain mod-severe
* not with PA or opiate containing epidural
Post operative neuropathic pain?
Gabapentin
Post operative gabapentin?
Neuropathic pain
Post operative analgesia - patient factors to consider
- comorbidities
- age
- frailty
- renal & liver fn
- allergies
- current meds
- cognitive function
Post operative analgesia - patient discussion
- likely pain from procedure
- pt preference
- pt expectation
- pain history
- potential benefits and risks
- long term risks
- different types of pain relief
- plans for discharge
What is epidural analgesia
administration of analgesics into epidural space.
• allows injection near spinal cord and nerves
• powerful analgesic effect
Epidural space in spine?
- contains fat
- above subdural space
- which is above subarachnoid space - contains CSF
Area of analgesic effect from epidural analgesia
- thoracic
- low thoracic/high lumbar
- low thoracic
- lumbar
What is in epidural bag?
- opioid analgesic &
* local anaesthetic
Opioid in epidural does what?
- diffuses into CSF
- inhibits pain transmission in spinal cord
- main site of action - spinal opiate receptors
- no effect motor or sensory functions
- reversible
- doesnt migrate
local anaesthetic in epidural does what?
- diffuses across myelin sheath into nerve cell
- inhibit Na+ channels, prevent Na+ influx, reduce cell membrane excitability
- reversible
- doesn’t migrate
Epidural advantages
- High quality pain relief
- ↓ need for gaseous anaesthesia
- Reduced incidence of DVT
- Less sedation
- Left in situ for post-op analgesia
- Improved pulmonary function
- Reduced cardiac morbidity
- Reduced sepsis/chest infection
- Faster re-establishment of oral intake
- Tiny opioid dose compared to systemic analgesia
Epidural disadvantages
- Risk of permanent spinal damage
- Accidental injection into spinal cord “total spinal block”
- Infection risk
- Accidental IV administration (bupivacaine very cardiotoxic)
- Dural puncture headache
- Epidural bleed/haematoma
- Migration of drug leading to respiratory paralysis
Accidental IV admin of bupivacaine in Epidural - rescue therapy
- Intralipid 20% shown to reverse LA- induced cardiac arrest in animal models
- recovery LA-induced cardiac arrest may take an hour
Opioid toxicity in Epidural - rescue therapy
- IV naloxone 100-400mcg
* short 1/2 life = repeat doses
Severe hypotension in Epidural - rescue therapy
• ephedrine
Epidural CI?
- pt refuse
- infection at proposed site
- clotting abnormalities
- severe respiratory impairment
- uncorrected hypovolaemia
- raised intercranial pressure
- neurological disease
- tattoos?
types of pain
- somatic
- visceral
- neuropathic
- sympathetically maintained pain
somatic pain is
- From cutaneous / musculoskeletal tissue or peritoneal membranes
- Post-operative, post-exercise, mild trauma
Visceral pain is
- The thoracic or abdominal organs
* Post-operative, cancer-related, traumatic injury
Neuropathic pain is
- From injury to the peripheral or central nervous system
* Amputation (surgical or traumatic), type 2 diabetes
Sympathetically maintained pain is
- Sensitisation of CNS causes neuropathic-like pain in distribution of a sympathetic nerve
- Complex Regional Pain Syndromes (CRPS)
Nociception is?
- noxious stimuli with intensity enough to trigger reflex withdrawal, autonomic responses, pain
- pain subjective
Nociceptors
- mechanical
- thermal
- polymodal
- not protein receptors - naked nerve endings
- dont up or down regulate in response to stimulation
- pain perception is modifiable
Peripheral nociception - A fibre subtypes
- alpha
- beta
- gamma
- delta
A-alpha fibres?
- efferent
- motor
- somatic
- reflex activity
A-beta fibres?
- afferent
- innervate muscle
- touch
- pressure
A gamma fibres?
- Efferent
* muscle spindle tone
A delta fibres?
- Afferent
- pain
- cold
- temp
- tissue damage
Nerve fibres - myelinated ?
A yes
B yes
C no
Nerve fibres - diameter? conduction velocity?
A to C
diameter - decreases
conduction velocity - decreases
Nociceptors - which neurons carry noxious stimuli
A𝛿 fibres
C fibres
first pain: informative, move away
second pain: punishing pain, changes behaviour
transmission - nociception
- afferent pain fibres
- dorsal horn spinal cord
- brainstem
- thalamus
- cortex
- higher brain
detection - nociception
- noxious stimulus
- release chemical mediators
- activate nociceptors
- cell membrane become depolarised
- AP generated
perception - nociception
- Brain activation
- Reticular system
- somatosensary cortex
- limbic system
modulation - nociceptors
Changing transmission of pain impulse in spinal cord via complex DMPP (descending modulatory pain pathways)
DMPP
descending modulatory pain pathways
Trauma releases which chemical mediators?
ATP Bradykinin Prostaglandins Histamine 5HT H+
PHAB!
Capsaicin - nociceptor pharmacology
TRPV1 receptor
Bradykinin to ? pharmacology - nociceptor
- B2 receptor
- release Protein Kinase C
- phosphorylates TRPV1
- depolarisation
Prostaglandins to ? - nociceptor pharmacology
- prostanoid receptor
- protein kinase A
- Voltage gated Na channel
Prostaglandins in nociception
- PGE2 causes K+ channel inactivation and phosphorylation of TRPV1 via EP receptors
- NSAIDs inhibit PG synthesis (COX) - analgesia
TRPV1 activated by?
- heat, chemicals, phosphorylation
- capsaicin
- allyl isothiocyanate - wasabe
ASIC activated by?
H+
P2X activated by?
ATP
TRPV1 receptor role
- peripheral detect body temp
* stimulated = burning sensation
C fibre causes release of?
- peripheral release of neuropeptides
- substance P
- CGRP (calcitonin gene-related peptide)
- cause release inflammatory mediators and NGF - +ve feedback
- sustained release thus can cause hyperalgesia
Hyperalgesia
increased sensitivity
NGF
nerve growth factor
NGF acts on?
- acts on TrkA receptors
- causes upregulation of NaV channels
- signals to increase activity TRPV1 via tyrosine kinase activity (phosphorylation)
mutation to TrkA?
• congenital insensitivity to pain
NaV channels & pain
- essential for action potential propagation
- 5 NaV subtypes
- NaV 1.1, 1.6, 1.7, 1.8, 1.9
Mutations in NaV1.7 lead to?
- erythromelalgia & paroxysmal extreme pain disorder
* loss of activity of NaV 1.7 = no pain
Afferent pain fibres enter dorsal horn in different laminae. Which Fibre - laminae?
A𝛿 - laminae I and V
Aß - laminae III, IV and V
C - laminae I and II
Referred pain
- visceral activation.
- somatic perception
- eg heart attack, pain down left arm.
Perception by brain
- somatosensory cortex - process information on location & intensity
- cirgulate & insular cortices, amygdala - emotional components
