Pain, Electricity and TENS Dr

Mark Johnson (Ph.D.)

Professor of Pain and Analgesia Leeds Metropolitan University

Centre for Pain Research at Leedsmet http://www.leedsmet.ac.uk/health/painresearch/

TENS has been tried on virtually every known pain

Johnson (2001) In. Electrotherapy Evidence Based Practice

•

Undiagnosed pain•

Pacemakers

•

Epilepsy ??•

Pregnancy ??

•

Cardiac condItions

•

Carotid sinus •

Broken Skin

•

Dysaesthetic

skin•

Internally (mouth)

•

Cognitive impaired

Contraindications/Precautions

Some useful Guidelines

www.csp.org.uk

Physiological Rationale

Conventional TENS

Touch

Pain

Rubbing

Body Spinal Cord

Brain

Skin stimulation

Touch receptors

Pain

TouchRubbing

Body Spinal Cord

Brain

Skin stimulation

Touch receptors

Electrical

device that passes currents...

… across the surface of the skin

Transcutaneous

... to produce Nerve Stimulation

Transcutaneous

ElectricalNerve Stimulation (TENS)

..stops “pain” messages getting to the brain

Tingle

Body Spinal Cord

Brain

Skin stimulation

Touch receptors

Electricity

Pain

Pain

Tingle

Body Spinal Cord

Brain

Skin stimulation

Touch receptors

Electricity

Tissue Damage

NociceptorC fibresAβ

fibres

Synaptic inhibition

Prevents onward transmission

TENS

No nociceptivesignals reach

brain

MUSCLE

SKINA-β

A-δC

TENS Currents

TENS Electrodes

Purpose conventional TENS = selective activation touch fibres-Aβ

©

Prof. M. Johnson Leeds Met.

Examine the following pain charts completed by some patients (shaded area = pain).Draw two squares on the diagram to identify where you would attach TENS electrodesfor each condition.

Low back pain Post-Herpetic Neuralgia Phantom Limb Pain

So what’s the best way to apply TENS using a ‘standard’ device?

©

Prof. M. Johnson Leeds Met.

C6-C8 Unilateral

L-S

T9-T12

TENS electrode placement

Apply electrodes to ‘tingle’......–

the pain

–

the main nerve trunk–

sites proximal to pain

–

spinal segments ~ origin of pain

©

Prof. M. Johnson Leeds Met.

AMPLITUDE

HIGH

LOW

BCM

On

Off 4F

76

910 1

5

238

23

46

89

10 1

7 5

I4

D7

6

910 1

5

238

DURATION

SHORT LONG

FREQUENCYHIGH (250pps) LOW (1pps)

AMPLITUDE MODULATED

PATTERN

BURST

CONTINUOUS

What are the best settings for TENS?

Studies using experimental pain on students at Leeds Met

ColdPain

PressurePain

ElectricalPain

IschaemicPain

Cuff

TENS

Best TENS settings are….•

Strong but comfortable tingling

•

Site of pain (segmental)–

nerves proximal/dermatomes

•

Adjust other settings on trial and error basis

Settings for conventional TENS

Electrical pulse…..•

amplitude

•

strong but comfortable•

pattern

•

continuous (experiment)•

frequency

•

midrange ~80pps (experiment)•

duration

•

~100-200μs (experiment)

©

Prof. M. Johnson Leeds Met.

TENS is a TechniqueTENS is a Technique

Standard TENS

Descending Pain Inhibitory

Pathways

Inhibit Nociceptive

Transmission

Aβ

Activity

Muscle contractions

Acupuncture-Like

Painful skin stimulation

Intense

Conventional

Non-painful skin stimulation

Electrical Stimulation of the skin for Pain Relief

Physiological Rationale Acupuncture-Like TENS

Defining AL-TENS

Used in 2 main

circumstancesLF/HI TENS producing visible muscle twitches

myotomal

to pain

TENS administered at acupuncture

points

AL-TENS Application

•

short treatment session•

post TENS analgesia

•

powerful analgesia•

administer sites remote from pain

•

patient education–

difficult

–

time consuming•

uncomfortable sensation

•

produce muscle fatigue •

reduced mobility during stimulation

Advantages Disadvantages

Spinal Cord Brain

Pain

Descending Pain Inhibitory PathwaysA-delta fibers

PeripheryAcupuncture

Descending Pain Inhibitory PathwaysGIII Muscle afferents

Spinal Cord Brain

Pain

AL-TENSPeriphery

MUSCLE

TENS electrodes

GI

Cathode Anode

CONTRACTION

MUSCLE GIIIextrasegmental

Aβsegmental

AL-TENS

Motor point

TENS Currents

Main indications for AL-TENS

•

When pain resistant to conventional TENS

•

When pain widespread

•

When long post TENS analgesia is required

•

When marked hyperaesthesia

/ reduced or changed skin sensitivity and cTENS

won’t produce electrical

paraesthesia

•

When pain deep seated pain myalgia

•

Irradiating neurogenic

pain in the limbs

Tissue Damage

Skin

TENS induced impulse

extinguishes impulse arising from noxious

stimulus

TENS currents

TENS electrodes

TENS induced impulses travel to

CNSAntidromic activation

of axon by TENS

Peripheral mechanisms•

nerve block/slowing conduction–

large diameter non-nociceptive

afferents

–

small diameter nociceptive

afferents

Impulses generated by noxious

event

Summary - TENS action

Central mechanisms• segmental inhibition (spinal gate)

• supraspinal inhibition (endorphins)

Peripheral mechanisms• nerve block/slowing conduction

Yes it doesI use it

No it doesn’tI read the research

Do physiological effects translate into clinically meaningful effects?

©

Prof. M. Johnson Leeds Met.

Does TENS work?

Health fraud (FDA)•

promotion, for profit, of a medical remedy known to be false or unproven

Quackery•

a pretender to medical skill; a charlatan

www.quackwatch.org/

There’s nowt

peculiar about …medical quackery

To be clinically effective therapeutic effects must be attributed to the active ingredient of the treatment

[RCT] Clinical Trials

Systematic Reviews

Meta analysis

Clinical Research

19-10-09 No Limits Search•

Transcutaneous

Electric Nerve Stimulation

= 4654 hits•

Clinical Trials = 939

hits

•

RCTs

= 640

hits•

Meta-Analysis = 24 hits

Not effective•

LBP (CR -

Milne 2001)

•

Labour

Pain (SR -

Carroll 1997a,b)•

Postop. Pain (SR -

Carroll 1996)

Effective•

Mechanical Neck Disorders (CR -

Kroeling

2005/09)

•

Musculoskeletal Pain (MA -

Johnson 2007)•

Knee OA (MA -

Bjordal and Johnson 2007)

•

Knee OA (CR -

Osiri

2002)•

RA Hand (CR -

Brosseau

2003)

•

Post-op. Pain (MA –

Bjordal 2003)•

Primary Dysmenorrhoea

(CR -

Proctor 2002)

•

LBP (CR -

Flowerdew

& Gadsby

1998)

Inconclusive•

Knee OA (CR -

Rutjes

2009)

•

Labor pain (CR -

Dowswell

2009)•

Acute pain (CR –

Walsh 2009)

•

Chronic Pain (CR -

Nnoaham

2008)•

Cancer Pain (Robb 2008)

•

LBP (CR -

Khadilkar

2008)•

Chronic Headache (CR-

Bronfort

2004)

•

Chronic Pain (CR -

Carroll 2001)•

Post-Stroke Shoulder Pain (CR -

Price 2001)

CR Cochrane ReviewSR –

Systematic ReviewMA –

Meta-analysis

Meta-analysis TENS PubMed

[2-11-09 > 20 hits]

[RCT] Clinical Trials

Systematic Reviews

Meta analysis

So what does this mean?

Clinical bottom lines ..and NICE

(Chronic Pain)

Clinical experience often differs to clinical research

Bandolier’s Bottom Lines for TENS

Transcutaneous

electrical nerve stimulation (TENS) should not be offered to women in established labour.

People with RA should have access to specialist physiotherapy, with periodic review to: ……learn about the short-term pain relief provided by methods such as transcutaneous

electrical nerve stimulators [TENS] and wax baths.

R14 Healthcare professionals should consider the use of transcutaneous

electrical nerve stimulation (TENS) as an adjunct to core treatment for pain relief.

Negative outcomes often due to inadequate technique

Raised the issue for acupuncture Investigated the issue for TENS

Optimal settings

Non-optimal settings11/21RCTs

(n=964)

9/21RCTs

Appropriate intensity Intensity too lowElectrodes -

site of pain

Electrodes -

distant

35% reduction intake

4% reduction intake

TENS, when applied appropriately, reduces postop. analgesic consumption

Adequate v inadequate TENS

TENS, EA ad LLLT produce short term reductions in OAK pain

•

36 RCTs

(2434 pat.) –

33RCTs >3 on Jadad

•

Efficacy at 1-4 week –

Acup/Magnets/US = placebo

–

TENS/EA/LLLT > placebo (~20% on VAS)

•

Limited data for 12 week follow-up

TENS reduces musculoskeletal pain•

32 studies on TENS

•

6 studies on PENS

•

meta analysis of 29 ENS studies

•

ENS>sham decrease pain at rest and on movement

Insufficient good evidence for chronic pain

25 RCTs

(1281 participants)•

13/22 TENS>inactive control

•

8/15 multiple dose TENS>inactive control

•

7/9 no diff between HF-LF TENS

•

Meta-analysis not possible

Method•

acute pain (<12 weeks),

•

no concurrent medication•

v. placebo, v. no treat., v. treat

Results•

12 RCTs

(919 participants)

•

116 excluded -

concurrent med.•

procedural pain•

(cervical laser treatment, venipuncture, sigmoidoscopy)

•

nonprocedural pain•

(postpartum uterine contractions, rib fractures)

•

Study heterogeneity-no meta-AConclusion•

Insufficient good studies

Insufficient good evidence for acute pain

Evidence of no effect for chronic LBP

•

4 high-quality RCTs

(585 patients)

•

meta-analysis not possible -

qualitative

synthesis used•

conflicting evidence for pain intensity

•

consistent evidence in two trials (410 patients) TENS did not improve back-specific functional status

Does TENS relieve pain?

•

Possibly if given appropriately

•

It is inexpensive, safe and patients can administer it themselves

©

Prof. M. Johnson Leeds Met.

TENS

Take home message•

TENS devices = blunt instruments

–

stimulate nerves in skin–

create muscle contractions

•

nerve stimulation more important than stimulator

–

conventional TENS•

‘Strong but comfortable paraesthesia’

•

Site of pain (segmental)

TENS-Like Devices

•

Interferential (IFT)•

Neuromuscular Electrical Stimulation (NMES / FES)

•

Microcurrent

(MENS)•

Russian Currents

•

High Voltage Pulsed spike currents

•

Transcutaneous

Spinal Electroanalgesia

(TSE)

TENS-like devices(Mystical Medicine)

Defining TENS and TENS-likeStandard device

TENS

TENS-Like -

Electrical Characteristics and theoretical action

Similar to standard

TENS

Unlike standard

TENS

•

High voltage pens •

TSE

•

Microcurrent

TENS•

Microcurrent

EA pens

•

Codetron•

VHF (2KHz) TENS

•

IFT

•

H-Wave Therapy •

Action Potential Simulation (APS)

Interferential Current Therapy (IFT)

Johnson (1999) Physiotherapy 85: 294-297

•

Most pains in physiotherapy ~ £100-2000•

Output–

Amplitude Modulated Interference Wave

–

20-30 min supervised session•

Theory–

deeper stimulation than TENS

•

Evidence (lots -

equivalent to TENS)–

Tabasam / Johnson 1999 onwards

Pain®Gone Pen

•

Most pains ~ £49.95•

Output–

High voltage single spike pulse short duration

–

press button 30-40 times on painful area•

Theory–

Non-invasive acupuncture -

endorphins

•

Evidence (none)–

pilot trials no control group -

60% pat. satisfied

–

Asbjorn

1999 / Ivanova-Stoilova

2002 (abstracts)

Transcutaneous

Spinal Electroanalgesia

(TSE)

•

Most pains ~ £290.00•

Output

•

Pulsed 250V, 0.5-4μs, 2-20KHz, ~ 30mins, spine

•

Theory•

no skin stimulation/no impulse generation

•

affect spinal cord cells -

?central sensitisation

•

Evidence (weak)•

Simpson 2004 TSE = Sham vascular disease

•

Macdonald 1995: TSE>TENS msk•

Towell

et al 1997: TSE ↑mood healthy subjects

•

Royle

2002... TSE / Remedi

patients satisfied

Non-invasive electroacupuncture (microcurrent)

•

Most pains ~ £89.95 •

Acupuncture points

•

190μA -

1.5mA / 5-20pps •

Claimed to release endorphins -

!

Evidence•

limited

•

Don’t be fooled by over ambitious claims of effectiveness

•

“the search for optimal ‘magic bullet’ settings is often egged on by manufacturers with half an eye on competitive in the market place”

Lessons From TENS

Take home message•

It is tissue [nerve] stimulation not the stimulator that is the active component

•

TENS devices are “blunt instruments”– to stimulate nerves in skin– to create muscle contractions

TENS