6 Electrical Currents for Pain Control

acute vs chronic pain

acute: warning system, want to reduce contributing factors such as inflammation, wound care, and stabilizing joints

chronic: less well-defined, no biologic benefit, pain that persists beyond the normal time frame of healing

3 months generically divide acute and chronic

what are the types of pain nerve fibers?

A-delta (myelinated) and C fibers (non-myelinated)

A-delta fibers vs C-fibers

A-delta: fast, myelinated, well-localized, activated for withdrawal reflex

C-fibers: slow, unmyelinated, diffuse/dull ache/pain, slower transmission and longer lasting

what are the gates in the gate-control theory of pain?

spinal cord, brainstem, prefrontal cortex

how does estim work in gate-control theory?

activating a-beta nerves can close a gate by activating inhibitory interneurons in spinal cord

what is the most common waveform for TENS?

pulsed biphasic

what are the types of TENS?

conventional (high-rate) TENS

low-rate TENS

burst mode TENS

brief intense TENS

what is high-rate TENS?

at the sensory level (no motor response), block pain by stimulating A-beta sensory nerve fibers

for high-rate TENS, frequency is _____. intensity is ____, and duration is _____. Electrodes are placed _______.

high, low, short

around the site of pain

what are the parameters for conventional TENS? frequency, pulse duration, on:off time, amplitude, tx time, effect time

frequency: 80-150 Hz/pps

pulse duration: 50-100µsec

on:off time: continuous

amplitude: strongest, comfortable paresthesia (sensory level)

tx time: varies, usually 15-20 min

effect time: 2-3 hours max

what is conventional TENS MOA?

gating at spinal cord (stimulating A-beta sensory n fibers)

what is low-rate TENS?

at the motor level (contraction), acupuncture-like, based on endogenous opioid release

for low-rate TENS, frequency is _____. intensity is ____, and duration is _____. Electrodes are placed _______.

low, high, long

on trigger point/muscle tension

what are the parameters for low-rate TENS? frequency, pulse duration, on:off time, amplitude, tx time, effect time

frequency: <10 Hz/pps (1-4 pps)

pulse duration: 200-300µsec

on:off time: continuous

amplitude: rhythmic muscle twitches

tx time: 20-30 min, <45 min to avoid DOMS

effect time: 4-5 hours max

what is low-rate TENS MOA?

endorphin release

what is burst mode TENS?

a combination of conventional and low-rate TENS

at the motor level

for burst mode TENS, frequency is _____. intensity is ____, and duration is _____.

high, low, long

when would you use burst mode TENS?

for more comfortable muscle contractions if low-rate TENS is intolerable

what are the parameters for burst mode TENS? frequency, pulse duration, on:off time, amplitude, tx time, effect time

frequency: 100 Hz/pps, delivered at 2 pps

pulse duration: 150-200µsec

on:off time: continuous

amplitude: rhythmic muscle twitches

tx time: 20-30 min, <45 min to avoid DOMS

effect time: 4-5 hours max

what parameters are usually preset for burst mode TENS?

pulse frequency (100 pps delivered at 2 pps) and pulse duration (150-200µsec)

what is burst mode TENS MOA?

endorphin release

what is brief intense TENS?

short, local hypoalgesia for minor painful procedures

noxious level effect

for brief intense TENS, frequency is _____. intensity is ____, and duration is _____.

high, highest tolerable (noxious), long

when to use high-rate TENS?

recent injury, inflammation, tissues may be damaged by contraction

when to use low-rate TENS?

muscle contraction can be tolerated, chronic pain (often has a longer duration of pain control)

T/F channels should be placed 2 inches apart and should cross channels

F, do not cross channels

steps to application of TENS

1. ensure patient is appropriate for tx

2. clean skin, remove excess hair

3. connect lead wires to unit and electrodes

4. securely place electrodes

5. adjust parameters

6. slowly increase amplitude until patient reports initial sensation

7. gently remove electrodes and assess patient skin condition - sensation, circulation, skin status

8. patient education

what is IFC?

interference of 2 medium frequency alternating currents with slightly different frequencies

delivered through 2 sets of electrodes from separate channels in the same stimulator

what is the frequency of IFC usually?

100-10,000 Hz

constructive vs destructive interference

constructive: insync/phase

destructive: out of sync/phase

why would you choose IFC as a treatment option?

possibly more comfortable than other waveforms and may affect larger and deeper area

medium freq/low amplitude at skin but at deeper tissues, functionally it becomes low freq/higher amplitude due to interference → more comfort at skin, greater effectiveness in deeper tissues

what is beat frequency?

difference between the frequencies in IFC

ex: frequency 1 is at 5000 Hz, frequency 2 is at 5100 Hz so beat frequency is 100

what is the MOA for IFC?

generally sensory level, could be motor

increases circulation and stimulates superficial and deep tissues

what are IFC modulation options?

sweep and vector scan

what does sweep modulation option for IFC do?

the machine varies beat frequency, usually in a shape

either pre-set or user set ranges

(lack of evidence)

prevents pt from adjusting to single freq, “sweeps” through range

what does vector scan modulation option for IFC do?

alters amplitude on one or both currents, like agitator on washing machine bc it rotates interferential field

may provide stimulation to a larger area

TENS vs IFC

TENS generally provides superior pain relief but IFC may be alternative if patient dislikes the sensation of TENS

what are the indications for IFC?

same as TENS

pain from swelling, pain with MSK conditions, chronic inflammatory conditions, chronic LBP

what is patient set-up for IFC?

setup: 2 channels that cross, electrodes are placed 2 inches apart

what are parameters for IFC? carrier frequency, beat frequency, vector scan, intensity, tx time

carrier frequency: 4000 Hz (default)

beat frequency: high: 80-150 Hz, low: 1-10 Hz (defaults)

vector scan: automatic at 100%

intensity: patient tolerance, strong but comfortable

treatment time: 15-20 min

what is premodulated current for pain control?

alternative current of medium frequency; mimics IFC but has 2 leads (single circuit, 2 electrodes)

same waveform as IFC requiring 4 electrodes - amplitude of wave automatically increases and decreases

IFC vs Premod

premod may not go as deep in tissue, does not cover larger area of stimulation and is better for smaller area

what is the evidence surrounding TENS with acute and chronic pain?

quality of evidence was weak in both, but pts generally showed improvement in pain for acute

not possible to conclude whether TENS is safe/beneficial for pain control, disability, health-related quality of life or analgesic use

evidence surrounding TENS vs IFC

both improved pain and functional outcomes with no statistical difference between which one was better

what are contraindications for TENS/IFC/premod?

cardiac pacemakers/electronic implants

unstable arrhythmias

malignant tumors

over carotid sinus/ant neck/head/reproductive organs/chest

active DVT or thrombophlebitis

in area of hemorrhage or active infection

over damaged skin; recently radiated skin

pregnancy (over/near abdomen or low back)

low-rate/burst TENS should not be used if muscle twitch is contraindicated

what are precautions for TENS/IFC/Premod?

impaired sensation

impaired mentation

impaired circulation

skin disease/irritation

neuropathies/denervation

active epiphysis

cardiac disease