Electroanalgesia

Question 1

According to Wall and Melzak, what is the method by with TENS works on pain? Describe both the conventional method and “acupuncture like” method.

Answer 1

Gate control theory: stimulation of large myelinated afferents with high frequency blocks pain input (conventional). Stimulation at a low rate promotes the release of endogenous opiates (endorphins and enkephalins)(acupuncture-like).

Question 2

What type of waveform does TENS use?

Answer 2

Pulsed current, often asymmetrical biphasic.

Question 3

Name 4 indications for electroanalgesia.

Answer 3

1. Acute and chronic pain syndromes - musculoskeletal, neurological
2. Post operative pain
3. Labor and delivery pain*
4. Prior to painful procedures

Question 4

Name the contraindications (8).

Answer 4

1. Demand type cardiac pacemakers or other implanted stimulating devices
2. Over eyes
3. Over the carotid sinus
4. Over the chest in the presence of cardiac dysfunction
5. In the presence of seizure disorders, avoid the head and neck area
6. With patients with cognitive impairment
7. Over open wounds or compromised skin including friable skin
8. Over areas in which movement is contraindicated if stimulating in a mode which creates visible muscle contractions

Question 5

High-rate, conventional TENS is used for ___ level stimulation, and low-rate, acupuncture is use for ___ level. What theory supports each?

Answer 5

Sensory (gate control theory, afferent blocking); motor (some tingling with a little muscle movement, no tetanic contraction).

Question 6

For what types of pain is sensory-level stimulation (high rate, low pulse) most appropriate?

Answer 6

Acute superficial musculoskeletal conditions
Labor and delivery pain
Post-operative incisional pain

Question 7

Sensory-level TENS is non-noxious and can be used for long periods of time. Are there any lasting effects when the device is turned off?

Answer 7

No. There is very little carry-over when device is turned off.

Question 8

Where should the TENS unit be placed for sensory-level stimulation?

Answer 8

Directly over the site or over a related dermatome or spinal root level. Can be places over pain or “sandwiched”.

Question 9

In motor-level TENS, what types of pain fibers are stimulated? What type of pain is this appropriate for?

Answer 9

Small, unmyelinated A delta and C fibers which motor efferents to stimulated muscles rhythmically. Used for deep, aching or chronic pain by producing a visible muscle contraction.

Question 10

Describe a quadripolar setup with an interferential current (IFC).

Answer 10

A quadripolar setup uses 4 pads with criss-crossed polarity to create an electrical interference where they intersect, resulting in a “beat”.

Question 11

How is IFC different than Russian? They are both medium frequency currents.

Answer 11

IFC uses sinusoidal, polyphasic AC waveforms and can be used for electroanalgesia or muscle stimulation (under different parameters).

Question 12

Describe vector scan and pre-modulated current (not related).

Answer 12

Vector scan is a variation in frequency to avoid adaptation to stimulus (can only be done with quadripolar setup).
Pre-modulated current is for smaller joint areas.

Question 13

What are the two types of beat frequencies that an IFC can produce?

Answer 13

Variable (sweep) mode where beats vary within a range (1-15bps or 100-120bps).
Constant mode: unchanging beat frequency.