Basic Principles and Difficult Pain

Dr Pete NightingaleMacmillan GP

Objectives

By the end of this session I hope that you will have refreshed your ability to diagnose the type of pain a patient has and have in mind a strategy to deal with each pain.

Incidence in Cancer About ¼ of patients never

have pain Of those that do:-1. 1/3 have a single pain2. 1/3 have three or more

different pains

Overview of Pain Classification

Definitions

Classification

Nociceptive and Neuropathic

Definitions

Definitions of Pain Pain

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

AllodyniaPain due to a stimulus that does not normally provoke pain

DysaesthesiaAn unpleasant abnormal sensation, whether spontaneous or evoked

Causes of Pain Pain caused by cancer and other

medical illnesses may be caused by either direct effect of the disease

OR

By the treatment associated with the disease which injure organs,muscles and nerves.E.G. Surgery, Chemo, XRT

Classification of Pain

Which type of pain could be classified as visceral nociceptive pain?

A Dull or aching, well localised B Intermittant, burning or

shooting C Associated with an area of

abnormal sensation D Poorly localised, colic or

sensation of pressure

Classification of Pain

Nociceptive Pain Neuropathic Pain

Pain pathways intact Anatomical or functional abnormality of pain pathway

In area of abnormal sensationSomatic Visceral

Pain TypesSomati

cVisceral Neuropathi

c

Source Skin or Deep

Tissues

Organs Damaged Nerves

Character

Dull or achingWell

localised

Tender pressurePoorly

LocalisedColic

Burning or Shooting

Intermittent

Causes TraumaBone Mets

MILiver Mets

Post-herpeticPhantom

Limb

Nociceptive Pain

SomaticActivation of pain receptors (nociceptors) by chemical stimuli in cutaneous or deep tissues

VisceralActivation of nociceptors as a result of infiltration/compression/extension or stretching of viscera (organs)

Neurophysiology Normal physiology of pain

CNS

DRG

Stimulus Response

Pain neurone

Normal Sensation

Low intensity stimulation

Innocuous Sensation

High Intensity Stimulation

PAIN

Neuropathic Pain Spontaneous firing of damaged nerves

Pain due to a disturbance or pathological change in a nerve

A form of pain that occurs in up to 1% of population.

Virtually any condition that damages neural tissue or causes neuronal dysfunction can result in neuropathic pain

Pain in an area of abnormal sensation

DiagnosisSYMPTOMS SIGNS

Positive

•Pain

•Paraesthesia

•Hyperaesthesia

Negative

•Numbness

Normal

Motor

•Distal Wasting

•Absent reflexes

Sensory

•Reduced Vibration/ light touch/ Pinprick

Pain Assessment

Assessment of Pain

i. History ‘ Pain is what the patient says it is’

There is evidence health workers tend to underestimate pain.PQRSTResponse to previous treatmentNew Pain or Exacerbation

P P Q R S T P Palliative factors ‘what makes it better?’ P Provocative factors ‘what makes it worse?’ Q Quality of pain ‘what exactly is it like?’ R Radiation ‘Does it spread anywhere?’ S Severity ‘How much is it affecting life?’ T Temporal factors ‘Does the pain come and

go?’

Assessing Consequences of Pain

depression Anxiety Ability to

interact socially

physical performance working ability

family income

PAIN MAY LEAD TO

Factors Affecting Pain ThresholdThreshold Threshold

Discomfort Relief of other symptoms

Insomnia Sleep

Fatigue Sympathy

Anxiety Understanding

Fear Companionship

Anger Creative Activity

Sadness Relaxation

Depression Anxiety

Boredom Mood

Mental Isolation Analgesics

Social abandonment Anxiolytics

Antidepressants

Principles of Pain Management

Treating the Underlying Cause

Palliative Anti-cancer TreatmentRadiotherapyChemotherapyHormone therapy

Modifying the effects of the diseaseCorrect HypercalcaemiaTreat LymphoedemaSurgery – spinal stabilisation

WHO Analgesic LadderWill deal with 80% of Cancer Pain

strong opioid(morphine)

weak opioid(Codeine or Tramadol)

non-opioid

(Paracetamol)

+/- Adjuvant

Tramadol

Dual MOA Via opioid receptors By blocking 5HT and NA

1/5th as potent as morphine orally

Less constipating than codeine/morphine

?role in neuropathic pain

?lowers seizure threshold

Rules for Step 2

A weak opioid should be added to a non-opioid

If a weak opioid is inadequate at regular optimal dose, change to morphine

Codeine is 1/10th as potent as morphine

Do not ‘kangaroo’ from weak opioid to weak opioid

Step3: Strong Opioids Morphine Diamorphine Oxycodone Methadone Hydromorphone Fentanyl Alfentanil

Yet another A B C ! A-Anti-emetic-usually

Haloperidol 1.5mg for 7-10 days

B- Breakthrough pain. Use 1/6 of daily dose (4 hrly equivalent) as ‘rescue’

C-Constipation – Laxative always required

Morphine preparations

Modified Release:

Zomorph /MST Continus 12 hourly regularly

MXL capsules 24 hourly regularly

Initiation of Morphine For uncontrolled pain, start 4

hourly I/R morphine for rapid titration

Prescribe prn I/R at the same dose

If the patient responds to rescue doses, use them as needed

(? double night-time dose)

Conversion to long acting Once pain controlled on 4 hourly

dose I/R morphine, can convert to M/R morphine

Tot up total daily morphine

For Zomorph: divide by 2 and prescribe Zomorph at this dose bd

For MXL: prescribe the total dose once daily

Conversion

Prescribe prn breakthrough dose 1/6th of total daily morphine dose

Give the 1st dose of M/R morphine with the last regular dose of I/R

Patient Explanation1) The first goal is reduction in

discomfort (setting targets)

2) Common side-effects are sleepiness, nausea and constipation.

3) The drowsiness/nausea tend to wear off

4) Prophylactic Rx nausea and constipation

THEN REGULARLY REVIEW PATIENT

Alternative Strong Opiates

Choosing the right opioid 

Subcutaneous infusion: diamorphine

Stable pain, unable to swallow: SC diamorphine or transdermal fentanyl

Afraid of using morphine: oxycodone or fentanyl

Infection with pyrexia: any can be used except transdermal fentanyl

Mild - moderate renal impairment: Possibly use hydromorphone

Severe renal failure: fentanyl

Liver impairment: morphine (with care)

Please rank the following in order of potency:- 

A Codeine 60mg B Tramadol 100mg C Morphine 5mg D Fentanyl 25mcg/hr patch.

 

FENTANYL (eg Durogesic D Trans)

Alternative strong opioid (Change patch every 72 hrs)

Take 12-48hrs to achieve maximum blood levels

Oral Morphine used for breakthrough pain

Indications for use Intolerable adverse effects of morphine Tablet phobia or difficulty swallowing Poor compliance with oral medication When the patient won’t have anything called morphine!

FENTANYL(e.g Durogesic D Trans)

4HRLY MORPHINE DOSE

MST b.d. FENTANYL DOSE

5-20mg 30mg 25µg/h

25-35mg 90mg 50µg/h

40-50mg 120mg 75µg/h

55-65mg 180mg 100µg/h

70-80mg 240mg 125µg/h

85-95mg 260mg 150µg/h

100-110mg 330mg 175µg/h

Oxycodone MR – Oxycontin IR – Oxynorm

Oxycodone twice as potent as morphine

MST 10mg bd Oxycontin 5mg bd

Tolerated better by some

More expensive

Adjuvant Analgesics (1)Analgesic Indication Example

NSAIDs Bone Pain Diclofenac

Steroids SOL/ Organ Infiltration

Dexamethasone

Anti-depressants

Neuropathic Pain Amitriptyline

Anti-convulsants Neuropathic Pain Gabapentin

Anti-spasmodics Colic Buscopan

Anti-spastics Skeletal Muscle Spasm

Baclofen

Benzodiazepines Muscle Spasm Diazepam

Non-drug Treatments (1) Nerve Blocks

Local Anaesthetic

Neurolytic (phenol)

NeurosurgeryCordotomy

ImmobilisationRest / Slings /Splints/ Corset

Walking Aids / Wheelchair

Non-drug Treatments (2) Psychology

IndividualGroup

RelaxationEducationCognitive TherapyMulti-disciplinary Approach

Distraction

Hypnosis

Mannix K et al Palliative Medicine 2006; 20:579-584

Cognitive Behaviour Therapy (CBT) can be used by palliative care staff to help patients.

Training may become more widely available

CBTCognitive Behaviour

Therapy

PhysicalPain

ABC of CBT!

A is the activating event B is your beliefs and thoughts

C is the consequences, such as emotions you feel

The Mercedes Model

THINKING EMOTIONS

PHYSIOLOGY

Our ever present internal states consist of:

Balloon challenge!

Non-drug Treatments (3) Counter-irritation

Massage – Gate Control TheoryTENS – Gate Control TheoryAcupuncture – stimulates release of

endorphins

PhysicalExercise and mobilityPhysiotherapyHydrotherapyMusic/ Art therapy

Lifestyle Modification

Reasons for Unresolved Pain

A belief that symptoms are untreatable

Fear or ignorance (docs/patients/carers)

Inadequate assessment

Inappropriate treatment No adjuvants / wrong drug or dose

Total pain

Failure of patient and doctor to ask for help

Neuropathic Pain Management

What is a commonly accepted ‘batting order’ of drugs to treat

neuropathic pain

A Gabapentin B Amitriptyline C Dexamethasone D Ketamine

Neuropathic Pain Pharmacological

Invasive/injection therapy

Physical therapies

Psychological therapy

Complementary therapy

WHO Ladder +/- NSAIDs Compound analgesics

Nsaids- use for trial of 3-7 days and then review

Opioids do work

Responsiveness reduces with time

?In combination with neuropathic agents

No evidence for one opioid above another except Methadone

Anti-depressants

Best evidence base is amitriptylline

Small NNT

High NNH

Usually well tolerated

Rapid response

1 wk to reach steady state

Anti-convulsants Gabapentin Short acting Safe/ Good side-effect profile Can use in severe renal compromise Memory loss and reduced concentration More expensive Improved sleep pattern Mood enhancement

Clonazepam good for night pain

Ketamine

NMDA antagonist

Beneficial for incident related and pressure area pain

Can use as little as 2.5mg sublingual for procedure pain (effect within 10 minutes)

Breaking the cycle of pain with ketamine or spinal intervention

Methadone - Indications for use

Intolerable side-effects with other opioids

Inadequate analgesia despite dose titration

Morphine hyperexcitability, allodynia

Morphine poorly responsive pain

Nociceptive & Neuropathic pain

Severe renal failure

Antitussive

Management StrategyAmitriptyline

Gabapentin

Ketamine

Spinal

??? Methadone

Pregabalin

Clonazepam

Sodium Valproate

(Carbamezpaine)

Steroids

Summary Assessment of each pain is essential

Calm Reassuring Approach

Analgesic ladder and adjuvants

Non-drug measures

Realistic goals

Clear Plan of Action

Regular reassessment