Managing Pain (effectively!)

Alec Price-Forbes

Consultant Rheumatologist

December 15th 2010

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 to use a walking aid, visited 4 doctors for the “right diagnosis”, alcohol to “knock me off the pain”

Behavior

Pain in cancer and non-cancer diseases

What % approximates the correct amount of

distressing pain in the following conditions?

10%, 30%, 60%, 80%

• Cancer

• MND/Neurological disease

• End-stage cardiac disease

• AIDS

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

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

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 (& (5mg – 10mg) 4hrly + 30mins prn (& laxative) (2.5 mg 4hrly if previously on laxative) (2.5 mg 4hrly if previously on non-opioid)non-opioid)

• 4hrly dose plus prn dose over 24hrs=TDD 4hrly dose plus prn dose over 24hrs=TDD (total daily dose)(total daily dose)

• TDD/2= 12 hourly (bd) doseTDD/2= 12 hourly (bd) dose

• TDD/6= prn doseTDD/6= prn dose

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

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