Definition

“Pain is whatever the experiencing person says it is, existing where

he/she says it does”

McCaffery (1980)

Physiology of pain

In its simplest form, the pain circuit in the body can be described as follows• pain stimulates pain receptors, and this

stimulus is transferred via specialised nerves to the spinal cord and from there to the brain.

• The pain stimulus is processed in the brain, which then sends an impulse down the spinal cord and via appropriate nerves which command the body to react, for instance by withdrawing the hand from a very hot object.

Pain Receptors

• Pain receptors are present everywhere in the body;

• Pain receptors are free nerve endings. • There are three types of pain receptor

stimuli: mechanical, thermal and chemical. • A mechanical stimulus e.g. high pressure

or stretching; thermal pain stimulus would be extreme heat or cold.

• Chemical pain receptors can be stimulated by chemicals from within and outside the body.

Pain nerve fibres

• Pain stimulus is transmitted from the receptors through peripheral nerves to the spinal cord and from there to the brain.

• This happens via two different types of nerve fibre: “fast pain” and “slow pain” fibres

• Fast pain is well localised, sharp and “cutting” and do not radiate.

Fast Pain Nerve Fibres

• They are thick nerve fibres called A-delta fibres. Because of their relative thickness.

• Pain stimulus are transferred very fast at a speed of 2-5s/m

• This allows the body to withdraw immediately from the painful and harmful stimulus in order to avoid further damage

Slow Pain Nerve Fibre

• They are thin nerve fibres called c nerve fibres.

• Pain impulse are transmitted slowly to the brain, at a speed of less than 2 m/s.

• The body responds by holding the affected part immobile (guarding, spasm or rigidity), so that healing can take place.

Pain transmission in the spinal cord and the brain

• The peripheral nerves carry the pain impulse to the spinal cord.

• In the spinal cord, fast pain and slow pain are carried up to the brain via different pathways

• The impulse of the fast pain goes to the cortex, allowing for the relatively precise localisation of the pain stimulus.

• The impulse from slow pain is distributed diffusely in the brain, with each area eliciting a different response

Characteristics of fast pain and slow pain

Slow Pain• Transmitted by very thin

nerve fibres• Poorly localised• All internal organs (except

the brain)• Body wants to be immobile

to allow healing (guarding, spasm, rigidity)

• Pain often radiates, or is referred

Fast Pain• Transmitted by relatively

thicker (and therefore faster conducting) nerve fibres

• Well localised• Mainly skin, mouth, anus• Immediate withdrawal of

stimulation to avoid further damage

• Pain does not radiate• Little relief from opioids

11/04/2023

Reviewed by Prof CL Odendal, senior specialist at the

department of anaesthesiology at the University of the Free State, April 2010.

Pain in the Elderly

• Effects of aging on pain sensation, perception, and behaviour are not well established

• Compared with younger adults, elderly persons rely more on slow/second pain (C fibre) than on fast/ first pain (A fibre).

• Another well-documented finding in the elderly is a slower response time to pain

• No evidence exists that pain intensity lessens with age

• Altered reactions to painful events may be due to loss of communications skills, cognitive abilities, or the failure of basic reflexes due to aging

• Additionally, pain in the elderly may be manifested as something other than pain, such as delirium

Pain in Children

• Children and young people have a right to appropriate prevention, assessment and control of their pain

• Historically, pain has been underestimated and under treated in children and particularly babies.

• Evidence shows that pain is inadequately dealt with for children, requiring better prevention, assessment and treatment.

• In order to treat children's pain effectively, a thorough pain assessment is necessary; a number of guides are available to do this

• British association for Emergency MedicineClinical Effectiveness committee: Guideline for the management of pain in children

How do we assess pain?

• Self report• Use pain rating tools• Non-verbal signs• Assess on movement• Document

Pain Assessment

No Pain (0)‘Happy because I

don’t hurt at all’

Mild Pain (1)

‘Hurts just a little bit’

Moderate Pain (2)

‘Hurts more’

Severe Pain (3)‘Hurts as much

as I can imagine

“Pain is whatever the patient says it is”

Always assess on movement

Other Pain tools

• Intensity scores - VAS, Categorical• Pain relief scales• Cognitively impaired• Paediatric• Critical care• Chronic Pain

– McGill Questionnaire– Quality of Life Questionnaire– Brief Pain Inventory– Pain Self Efficacy Questionnaire

What do we assess?

• Location • Duration• Type• Intensity

What needs to be considered when assessing pain?

• Subjective• Age• Communication• Psychiatric factors• Cognitively

impaired• Culture• Knowledge of pain

treatments

• Expectations of pain treatments

• Language barriers

Barriers to pain assessment in the older person

• Failure to recognise• Failure to assess• Assume stoicism• Patients & carers expectations of

pain in ageing• May use different words e.g.

discomfort, ache, soreness • Time consuming

Inadequate pain management can cause:• physiological effects (increased HR, BP,

delayed gastric emptying, increased adrenaline production)

• post-operative complications (respiratory infection, VTE, PE)

• delayed discharge • mobilisation difficulties• restlessness, irritability, aggression• raised levels of anxiety• sleep disturbances• distress and suffering

(Sjostrom et al 2000, Macintyre & Ready 2002, Carr et al 2005)

Pain Management and the role of

Psychology

Acute Vs Chronic Pain

Acute Pain– Short Term– Less than 3

months– Natural Healing

Occurs

Chronic Pain– Long Lasting– Longer than 3

months– Natural Healing

occurs– but huge IMPACT– Pain as a result

of Central NS changes- local, spinal cord, brain

Why do people react so differently to Pain?

Leventhal’s Common Sense Model

PainAction Taken /

CopingBeliefs About

Pain

Chronic Pain and Psychological Distress

Chronic PainAnxiety &

Depression

How does psychological distress affect pain experience and management?

?

The BioPsychoSocial Model

Psychological Interventions

Cognitive Behavioural Therapy shown to be effective – Has impact on biopsychosocial variables

However, psychological interventions for chronic pain most effective when incorporate other treatment components– e.g. physiotherapy, education– Pain Management Programmes

Impact of Chronic Pain

Pain

Reduction in activity

Failed Treatmentseg physio, med

Loss of Job, Financial Stress

Relationships

Being Blamed/Faking it

PhysicalDeconditioning

DepressionHopelessness, Helplessness

AnxietyFear re Future

FrustrationAnger

Loss of Independence

Boom and Bust

ExcessSuffering

Pain Management Aims

NOT cure or pain reduction

Change the person’s relationship with pain– Reduce disability and distress – Manage increases in pain (flare-ups)– Develop confidence in ability to carry out

activities despite pain– Reduce unhelpful encounters with public and

private health systems– Self-Management

Aims of Pain Management

Pain

• Education re Pain Model

• Pacing

• Communication

•Identifying unhelpful thoughts

Improve Fitness

Improve daily functioning

Reduce anxiety/depression

Increase confidence

Reduce dependence

Reduce incidence of Flare-Ups

ReduceDistress

• Goal Setting &Practice

• Flare-up Planning

• Exercising

• Relaxation

MDT Consultants, physios, psychologists,

nurses Pain Management Programmes

– Good evidence base, improve functioning NICE guidance 88, May 2009

– Outpatient Programmes PMP @ Whittington, COPE @ UCH

– Inpatient Programmes INPUT Pain Management Unit @ St Thomas’ Bath Pain Management Unit

References Sharp & Keefe (2006). Psychiatry in Chronic Pain: A review and

Update. Focus, American Psychiatric Association.

Turk & Okifuji (2002). Psychological factors in chronic pain: Evolution and revolution. Journal of Consulting and Clinical Psychology.

Vlaeyen & Linton, (2006). Are we ‘fear avoidant’. Pain.

Vlaeyen & Morley (2005). Cognitive-Behavioural Treatments for Chronic Pain: What works for whom? Clinical Journal of Pain.

Morley, Eccleston & Williams (1999). Systematic review and meta-analysis of randomized controlled trials of cognitive behaviour therapy and behaviour therapy for chronic pain in adults, excluding headache. Pain.

Nicholas M, Molloy A, Tonkin I and Beeston L (2000) Manage your Pain ABC Books, Sydney

Nice, Nice Guideline 88 (2009) – Early management of persistent non-specific low back pain, http://www.nice.org.uk/CG88