managing pain (effectively!) alec price-forbes consultant rheumatologist march 21 st 2012
TRANSCRIPT
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?
AimsTo consider general aspects of pain relief
What is pain?To consider issues around assessing and
diagnosing painTo understand the principles of choosing
an analgesicTo 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
• Inaccurate diagnosis of the cause
• Lack of understanding of analgesics
• Unrealistic objectives• Infrequent review• Insufficient attention to mood
and morale
Consequences• Unnecessary pain
• Inappropriate Rx
• 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 never-
ending/meaningless
• Pain overflows to affect others
Definitions
• 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
• 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
• Ask the patient highly accurate
• Ask the partner subject to bias
• Body chart involves patient
• VAS 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
By the Mouth
By the Clock
By the Ladder
Analgesic Mantra
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 blockConsider 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 choice- cost, 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 morphineStarting morphine
• (5mg – 10mg) 4hrly + 30mins prn (& laxative) (5mg – 10mg) 4hrly + 30mins prn (& laxative) (2.5 mg 4hrly if previously on non-opioid)(2.5 mg 4hrly if previously on non-opioid)
• 4hrly dose plus prn dose over 24hrs=TDD (total 4hrly dose plus prn dose over 24hrs=TDD (total daily dose)daily dose)
• TDD/2= 12 hourly (bd) doseTDD/2= 12 hourly (bd) dose• TDD/6= prn doseTDD/6= prn dose• Median dose for morphine is 100mg/day so PRN Median dose for morphine is 100mg/day so PRN
is 15mg 4-hrlyis 15mg 4-hrly• 90% patients managed with morphine dose 90% patients managed with morphine dose
<500mg<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 forCalculate breakthrough dose for
• MST 30mg bdMST 30mg bd
• MST 60mg bdMST 60mg bd
• MST 120 mg bdMST 120 mg bd
• MST 1500 mg bdMST 1500 mg bd
• MST 3000 mg bdMST 3000 mg bd
Dose titrationDose titration
• 12 hourly dose & total prn use= new TDD12 hourly dose & total prn use= new TDD
• New TDD/2= new 12 hourly doseNew TDD/2= new 12 hourly dose
• New TDD/6= new prn doseNew TDD/6= new prn dose
Calculate new MST dose and Calculate new MST dose and breakthrough dose forbreakthrough dose for
• MST 10mg bd and 4 doses of oramorph MST 10mg bd and 4 doses of oramorph 2.5 mg2.5 mg
• MST 120 mg bd and 2 doses of oramorph MST 120 mg bd and 2 doses of oramorph 40mg40mg
• MST 600 mg and 6 doses of oramorph MST 600 mg and 6 doses of oramorph 200mg200mg
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 rareREAL 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 impairmentAPPARENT INTOLERANCE• Dose too high• Titration too rapid• Conversion ratio incorrect• Other cause of confusion (biochemical, infections, other drugs)• Constipation
Changing the route of administrationChanging the route of administration
• po morphine > sc morphinepo morphine > sc morphine
• po morphine > sc diamorphinepo morphine > sc diamorphine
• po morphine > sc oxycodonepo morphine > sc oxycodone
• po oxycodone > sc oxycodonepo oxycodone > sc oxycodone
• 1/21/2
• 1/31/3
• 1/41/4
• 1/21/2
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 morphineTranstec 3-4 day patch 35 micrograms/h = 50-100mg oral morphine
In practice main route used is transdermalUseful in renal disease or when oral route not possibleFor CONTROLLED pain
Alternative OpioidsFentanyl 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
• 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