Transcript Controlling Pain - UHCW Medical Education

Managing Pain (effectively!)
Alec Price-Forbes
Consultant Rheumatologist
March 21st 2012
Mrs W
• OA, Inflammatory arthritis
• April 2010 unwell anaemic, APR raised
• July 2010 presumed osteomyelitis right
ankle
• September 2010 Staph sepsis
• Cervical discitis
• ? SBE
Mrs W
• 3/12 IV antibiotics
• November 2010
- septic
- CCU for inotropes
- drowsy
• On fentanyl 175mcg/hr
– What is PRN dose
– What dose of diamorphine would you convert to?
Aims
To consider general aspects of pain relief
What is pain?
To consider issues around assessing and
diagnosing pain
To understand the principles of choosing
an analgesic
To understand the use of morphine and
appropriate dose calculations
What is pain?
 How would you describe and define pain?
- please share thoughts with your neighbour
The background
What is pain?
• Pain is perceived along a spectrum from
peripheral pain receptors to the cerebral cortex
and is modified at every step along its travel
• Pain is an unpleasant, complex, sensory and
emotional experience
• Pain is a distressing experience for the patient
• Pain is what the patient says it is
Causes of failure to relieve pain
Reasons
• Belief that pain is inevitable
Consequences
•
Unnecessary pain
• Inaccurate diagnosis of the
cause
• Lack of understanding of
analgesics
•
Inappropriate Rx
•
• Unrealistic objectives
• Infrequent review
• Insufficient attention to mood
and morale
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Use of inappropriate,
insufficient or infrequent
analgesics
Dissatisfaction with Rx
Rejection of Rx by patient
Lowered pain threshold
Adapted from Twycross Update 1972
Total Pain
Spiritual
Physical
Total Pain
Social
Psychological
Saunders 1964
Chronic pain is different…
Ms. Unhappy
Why can’t you fix my
back and fxxk off
Ms. Unhappy
• 33 year old woman, accident at work
• “lifted something heavy and felt a click at
the back”
• MRI: unremarkable
Nociception
Ms. Unhappy
• She felt so bad that she cannot sleep,
cannot eat, and became irritable
Affect
Ms. Unhappy
• She cannot work, cannot go out, cannot
do housework, cannot….
Social
Ms. Unhappy
• She insisted in using a walking aid, visited
4 doctors for the “right diagnosis”, alcohol
to “knock me off the pain”
Behavior
Acute versus chronic pain
Acute (eg fracture)
• Obviously in pain
• Complains of pain
• Understands why they
have pain
• Primarily affects patient
Chronic (eg neuralgia)
• May only seem
depressed
• May only complain of
discomfort
• May see pain as neverending/meaningless
• Pain overflows to affect
others
Definitions
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Nociception
Pain threshold versus pain tolerance
Allodynia
Analgesia
Dysasthesia
CLASSIFICATION OF PAIN
• Nociceptive – associated with tissue
distortion or injury
• Caused by tissue damage injury – information
carried to the brain via normal nerves
CLASSIFICATION OF PAIN
• Neuropathic – associated with nerve
compression or injury
• The nerves carrying the information to the brain are
abnormal and are associated with abnormal sensations
» Nerve compression
» Nerve crushing/destruction
» Nerve being cut
Issues in assessing pain
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Where is it?
What is it like?
How long has it been present?
How severe is it?
Does it spread anywhere else
How is it affecting functioning?
What are the goals for the pain?
Managing Pain
• Take a good history and examine the patient
• Think about the cause or type of pain
– Somatic
– Visceral
– Neuropathic
• Establish patient’s expectations, priorities
• Choose appropriate medication
• Set realistic goals, negotiate a plan
Problems in assessing pain
Think about TWO problems that could make
it difficult to assess someone’s pain?
Common mistakes in pain
management
• Forgetting there may be more than one
pain
• Reluctance to prescribe morphine
• Failure to explore holistically
• Failure to educate patient about dose,
timing, side effects and deal with their
fears
• Reducing the interval instead of increasing
the dose
Problems in assessing pain
• The number of different pains (50% of patients
have 3 or more different pains)
• Not all pains respond to morphine
• Patients underplaying their pain
• Patients reacting markedly to their pain (usually
anxiety, anger or depression are present)
• Staff or partners assessing a patient’s pain
• The patient with poor or absent communication
Help with assessing pain
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Ask the patient
Ask the partner
Body chart
VAS
highly accurate
subject to bias
involves patient
some patients stuggle
with the concept
• Pain diary
qualitative research
• Pain questionnaire
Diagnosing Pain
• Bone metastases produce pain worsened with
movement
• Muscle pain produces pain on active movement
• Chest infection causes pain worse on inspiration
• Constipation causes pain at rest in the abdomen
which is periodic
• Neuropathic pain causes an unpleasant sensory
change at rest, sometimes with pain on touching
Pain behaviours/signs where
communication impaired
• Expressive: grimacing, clenched teeth,
shut eyes, wide open eyes
• Adaptive: rubbing or holding area, keeping
still, reduced or absent function
• Distractive: rocking, pacing, biting,
clenched fists
• Postural: increased muscle tension,
limping
• Autonomic: sympathetic, parasympathetic
Analgesic Mantra
By the
Mouth
By the
Clock
By the
Ladder
Individualised
Treatment
Attention to
detail
Types of analgesic
Primary
• Non-opioids eg paracetamol
• Weak opioid agonists eg codeine, DF118
• Strong opioid agonists eg morphine,
diamorphine, fentanyl, oxycodone
• Opioid partial agonist/antagonists eg
buprenorphine
• NSAIDs
• NMDA antagonists eg ketamine, methadone
• Nitrous oxide
Types of analgesic
Secondary analgesics
• Adrenergic pathway modifiers eg clonidine
• Antibiotics
• Anticonvulsants eg CMZ, gabapentin
• Antidepressants eg amitriptyline
• Antispasmodics eg hyoscine
• Antispastics eg Baclofen
• Corticosteroids
• Membrane stabilising drugs eg flecanide, lidocaine
• NSAIDs
WHO Pain Ladder
Consider
nerve block
WHO Analgesic staircase
• Use non-opioids, weak opioids and strong
opioids as the 3 steps
• However, not all pain opioid responsive
(eg colic, neuropathic pain)
• Consider adjuvants for each patient
• Different pains need different analgesics
Opioids
• Agonists at opioid receptors (mu, kappa,
delta) in spinal cord and brain
• Differences between opioids relate to
differences in receptor affinity
• Morphine is the strong opioid of choicecost, effectiveness, no ceiling effect
CASE SCENARIO
• In groups of 3, work through the first 4
questions
Opioid choice
Morphine given
Orally
Regularly
Prevents pain
Haloperidol treats nausea
Injections are unnecessary
No addiction is seen and
Early use is best
Morphine is still the gold
standard opioid:
• It has more evidence for
its use and safety
• No evidence that other
opioids are better
• 30 years use
• Wide safety margin
• Well tolerated in most
people
ANSWER Q1
• F never delay using if pain requires a strong
opioid
• T aim is not simply to treat pain, but prevent
recurrence
• F injection route more potent (less drug needed
for same effect) but is not more effective
• F morphine is converted to active metabolites so
reduced liver function has little effect
• T active metabolites are excreted via kidney
Starting Opioids
• What concerns might patients have about
starting morphine?
Dependence and Addiction
• Dependence- state in which an
abstinence syndrome may occur
following abrupt opioid withdrawal or
administration of opioid antagonist.
• Addiction - characterised by
psychological dependence
Morphine dose timing
• For continuous pain analgesia should be
continuous
• Regular administration should enable
good pain control and prevent it returning
• Do not rely on PRN
PRN = ‘PAIN RELIEF NIL’
Indications for injections
• Inability to tolerate other routes (eg
nausea and vomiting)
But NOT because of poor pain control:
• Giving injections means need less drug to
have same effect
• But it cannot be more effective because
it’s the same drug
Metabolism
• Morphine is absorbed from small bowel,
metabolised in liver to active metabolite
(morphine 6-glucuronide, M6G) which is
renally excreted
• Liver impairment has little effect; kidney
impairment does affect handling
• Other metabolites (eg M3G) also renally
excreted and can accumulate
Strong Opioids
• Immediate release (peak concentration
after 1h, duration of action 1-4 hours)
– Oramorph, Sevredol, OxyNorm
• Modified release (peak concentration
after 2-6 hours, duration 12-24h
depending on formulation)
– MST, MXL, Oxycontin
Starting morphine
• (5mg – 10mg) 4hrly + 30mins prn (& laxative)
(2.5 mg 4hrly if previously on non-opioid)
• 4hrly dose plus prn dose over 24hrs=TDD (total
daily dose)
• TDD/2= 12 hourly (bd) dose
• TDD/6= prn dose
• Median dose for morphine is 100mg/day so PRN
is 15mg 4-hrly
• 90% patients managed with morphine dose
<500mg
Question 3
• NO high dose would produce adverse
effects and deter patient from continuing
with an effective drug
• NO usually any increase is done third day
• NO useful rule is to increase by half (50%)
• Yes increase by 50% of dose every third
day
Calculate breakthrough dose for
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MST 30mg bd
MST 60mg bd
MST 120 mg bd
MST 1500 mg bd
MST 3000 mg bd
Dose titration
• 12 hourly dose & total prn use= new TDD
• New TDD/2= new 12 hourly dose
• New TDD/6= new prn dose
Calculate new MST dose and
breakthrough dose for
• MST 10mg bd and 4 doses of oramorph
2.5 mg
• MST 120 mg bd and 2 doses of oramorph
40mg
• MST 600 mg and 6 doses of oramorph
200mg
Case scenario
• Please do questions 5-7
Q5 Morphine worries
• Feeling drugged is unlikely since tolerance to may side
effects is rapid (effects wear off quickly)
• Tolerance to analgesia is not seen (pain relief does not
wear off with time)
• Withdrawal symptoms are likely if morphine stopped
abruptly but not if reduced slowly eg. over 5 days
• Addiction to morphine is unlikely. Circumstances in
which they take morphine does jot encourage addictive
behaviour
• Constipation is very likely
• Hallucinations, confusion and nightmares very
unlikely
Q6
• True intolerance to opioids very unusual and allergy rare
REAL INTOLERANCE
• Fear of opioids is commonest cause of intolerance but can be
managed by explanation
• Reduced drug clearance
• Morphine and oxycodone accumulate in renal impairment; fentanyl,
methadone little effect
• Opposite for liver impairment
APPARENT INTOLERANCE
• Dose too high
• Titration too rapid
• Conversion ratio incorrect
• Other cause of confusion (biochemical, infections, other drugs)
• Constipation
Changing the route of administration
• po morphine > sc morphine
• 1/2
• po morphine > sc diamorphine
• 1/3
• po morphine > sc oxycodone
• 1/4
• po oxycodone > sc oxycodone
• 1/2
STRONG OPIOIDS
• Morphine – global strong oral opioid of
choice
• Morphine – s/c if unable to take oral
morphine.
(When changing to Morphine (s/c) from
morphine (oral) give 1/2 of the PO
morphine dose)
• Fentanyl – transdermal patch or sublingual
Alternative Strong Opioids
Opioid
Equivalent potency to
oral morphine
Key points
Oxycodone
= 1/2 x oral morphine
dose
(10mg oral oxycodone =
20mg oral morphine)
Patients experiencing
toxicity with another
opioid
Diamorphine
=1/3 oral morphine dose
(10mg diamorphine sc =
30mg oral morphine
More soluble than
morphine, used in CSCI
Buprenorphine
BuTrans 7 day patch
20 micrograms/h = 10-20
mg oral morphine
Transtec 3-4 day patch
35 micrograms/h = 50100mg oral morphine
In practice main route
used is transdermal
Useful in renal disease or
when oral route not
possible
For CONTROLLED pain
Alternative Opioids
Fentanyl Patches
• Adhesive patch delivering a constant amount of
fentanyl per unit time: e.g. 25 micrograms/hour
• Less constipation, sedation and nausea
• Preferable in serious renal impairment
• Change every 72 hours
• Takes up to 24 hours to start or stop acting
• For controlled pain
• Need to supply breakthrough morphine or
oxycodone
Equivalent doses of fentanyl
Fentanyl patch dose
Approximate
equivalent dose of oral
morphine in 24 h
Breakthrough dose of
morphine
12mcg/h
45mg
5-10mg
25 mcg/h
90mg
10-20mg
50mcg/h
180mg
20-35mg
75mcg/h
270mg
35-45mg
STRONG OPIOIDS continued
• Hydromorphone – analogue of morphine
with similar pharmacokinetics
• Oxycodone – similar properties to
morphine. Less SE’s in some patients
• Methadone – needs to be started as
inpatient
Starting Opioids
• Dorothy, 63y diagnosed with advanced
ovarian cancer
• Constant low abdominal pain
• Bowels regular
• Taking co-codamol 30/500, 2 tablets qds
• What dose of morphine would you start?
• How would you advise her to take it?
•Name and address of
the patient
•The name of the drug
•The form and strength
of the preparation
•The total quantity of the
preparation, or the
number of dose units, in
both words and figures
•Dosing instructions
Nerve Damage
• Membrane stabilizing drugs
– Tricyclics
– Anti-epileptic drugs eg. Carbamazepine
– Gabapentin
Routes of administration
• Oral :
Tablets
/
Liquids
• Rectal
• Sublingual
/
Transdermal
• Parenteral
/
Subcutaneous
Other forms of treatment
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Physiotherapy
Hot / Warm
TENS stimulation
Acupuncture
Hypnosis
Complementary therapies
Relaxation therapies
Treating of underlying psychological,
social, spiritual distress
Mrs W
• Fentanyl 175
• What is equivalent morphine/diamorphine
dose?
Summary
• Pain is a subjective “total” experience and
assessment and management must take this
into account
• The WHO Ladder provides a framework for
managing pain
• There are a number of opioid medications,
with morphine being the opioid of choice in
most situations
• Adjuvant drugs are an important part of pain
management