Transcutaneous Electrical Nerve Stimulation, Phonophoresis, and Iontophoresis

CHAPTER 229 Transcutaneous Electrical Nerve Stimulation, Phonophoresis, and Iontophoresis



Russell D. White, Mary Beth Brown


The procedures described in this chapter—transcutaneous electrical nerve stimulation (TENS), phonophoresis, and iontophoresis—can be performed either by primary care clinicians in their office or by physical therapists when ordered by a clinician. The procedures are often used with other physical therapy modalities such as manual therapy or therapeutic exercise. The choice of procedure depends on the size (localized vs. diffuse) and depth (superficial vs. deep) of the proposed treatment area as well as the specific pathologic process.



Equipment



• Scissors to trim hair

• Isopropyl alcohol 70% to cleanse skin

• For TENS: TENS unit with either disposable or reusable electrodes and gel

• For phonophoresis: therapeutic ultrasound unit, appropriate medication, and coupling gel

• For iontophoresis: direct-current generator with constant current output (calibrated in milliamperes), electrodes, and appropriate medications


Preprocedure Patient Preparation


After discussing the patient’s diagnosis, the risks and benefits of the selected treatment should be explained, along with any treatment options. Oral or written consent should be obtained from the patient. Patients should be aware that their skin will be cleansed and that their hair may be trimmed. The anticipated treatment plan and total number of treatments should also be discussed.



Transcutaneous Electrical Nerve Stimulation


Transcutaneous electrical nerve stimulation therapy uses low-voltage electrical pulses to stimulate the nervous system and is used for the treatment of pain syndromes. Skin surface electrodes are used to pass the electricity into the affected area. TENS units are Class II, U.S. Food and Drug Administration–approved devices and are typically selected for larger, generalized areas of pain, for chronic joint pains, or for persistent myalgias. This procedure can be performed in the clinician’s office and is reimbursable if performed by the clinician. However, TENS therapy is usually prescribed by a clinician and performed by the physical therapist. When prescribed for home use, the patient must be competent in operating a TENS unit.


TENS therapy is based on the gate theory of pain. According to this theory, nociperception (injury information) is transmitted through T cells that convey information to the higher brain centers. This information is presynaptically inhibited by interneurons in the substantia gelatinosa. TENS therapy bombards these interneurons, attempting to modulate or decrease the pain transmission by effectively blocking transmission of pain sensation. Other theories suggest that TENS therapy achieves its result by an acupuncture effect, by release of natural opiates, or by direct local vasodilation, which may reduce relative ischemia.


The goal of TENS therapy is to reduce or relieve pain and discomfort. This result may be either short lived or prolonged. TENS therapy may slowly break the pain–spasm–pain cycle and reduce perceived discomfort. Unfortunately, TENS therapy is not effective for pain of central origin (e.g., headache).


Treatment parameters are chosen based on several factors:


• Intensity: Small unmyelinated fibers require more current than large myelinated fibers. (Intensity is set according to patient comfort [strong but not painful] and can vary widely by body part undergoing treatment, by device used, and by individual sensation and tolerance.)

• Pulse rate: Small unmyelinated fibers respond better to a low-frequency rate (<100 Hz), whereas large myelinated fibers respond better to a high-frequency rate (>100 Hz).

• Wave characteristics: These characteristics are either monophasic (positive rectangular pattern) or biphasic (negative spike pattern).

• Pulse width: Small unmyelinated fibers respond to a long pulse (200 milliseconds [msec]), whereas large myelinated fibers respond to a short pulse (50 msec).

• Modulation: Modulation allows gradual variation of the frequency or pulse width and retards accommodation of the nervous tissue.


Indications



• Chronic pain

• Acute pain

• Musculoskeletal pain

• Neurologic pain (e.g., herpes zoster)

• Phantom limb pain

• Before another procedure to elevate the pain threshold and to decrease patient discomfort after the procedure

• Postoperative pain

• Obstetric pain (after the first trimester)


Contraindications



• Patients with demand-type pacemakers (Newer pacemakers with improved shielding are not affected by TENS units. Check with a cardiologist or the manufacturer.)

• Patients in first-trimester pregnancy

• Patients with known cardiac dysrhythmias

• Mentally incompetent patients, uncooperative patients, those with paranoid disorders, or pediatric patients without adult supervision

• Undiagnosed pain syndromes without established etiology

• TENS therapy is also contraindicated over the following areas:
• Carotid sinuses

• Chest areas in patients with a cardiac history

• Head or neck area of patients with an epileptic history

• Laryngeal or pharyngeal muscles

• Local areas of skin irritation or loss of skin integrity

• Mucosal surfaces

• Eyes


Technique



1 Before initiating therapy, organize the necessary materials (Fig. 229-1) and prepare the skin area to which the electrodes will be attached. Trimming hair and cleansing the skin with 70% isopropyl alcohol will promote the adhesion and conductivity of the electrodes.

2 Select the proper electrodes. For 24 hours or more of use, select either a carbon-impregnated rubber electrode with gel or a carbon-filled silicone electrode.

3 Attach electrodes to the selected treatment site, whether isolated trigger points, individual dermatomes or myotomes, or in the distribution of a specific nerve. Position the electrodes so that a paresthesia will be felt in the area of pain or dysfunction (Fig. 229-2). If the electrodes are secured poorly to the skin, they may cause a burning sensation instead of a paresthesia. In addition, electrodes should be placed at least 2 inches apart. Placing electrodes closer together can cause a burning sensation. The electrodes should also be placed so that the perimeter of the painful area is entirely surrounded by the electrodes.

4 Select the treatment parameters. Conventional settings use a high-frequency rate with a narrow pulse width. The intensity level is less than that which results in muscle stimulation.

5 With the amplitude control in the off position, attach wires to the TENS unit. Turn on the generator unit and increase the amplitude slowly, up to the patient’s comfort level. Again, paresthesia should be felt by the patient before the threshold for motor stimulation.

6 If desired results (paresthesia with control of pain) are not achieved, change the stimulation sites or adjust the treatment settings.

7 Typically, patients are treated once or twice daily for a duration of 30 to 60 minutes. Some patients may benefit from more frequent treatments and may require a home unit for therapy.

8 When the treatment is completed, turn off the unit, return the settings to zero, and remove the electrodes.

image

Figure 229-1 Transcutaneous electrical nerve stimulation (TENS) unit (generator) with supplies for skin preparation, electrodes, and electrode wires.


image

Figure 229-2 TENS treatment.



Complications



• Skin irritation from electrode placement

• Contact dermatitis resulting from electrode gels

• Pacemaker malfunction (typically an older pacemaker)

• Twitch response secondary to stimulation of a motor nerve or end plate in the treatment area by inappropriate current


Phonophoresis


Phonophoresis uses therapeutic ultrasound to enhance the diffusion of medications across the skin and into body tissues. Commonly used medications include dexamethasone, hydrocortisone, and lidocaine. Although phonophoresis is usually performed by the physical therapist, some clinicians provide this modality in the office setting. Clinicians can be reimbursed for phonophoresis, even if not performed by a physical therapist.


The dual action of phonophoresis—thermal and mechanical—counteracts the inflammatory response by a process called acoustic streaming, which increases cell membrane permeability. This effect also facilitates the passage of medications into body tissue. With acute inflammation, using pulse-mode ultrasound avoids an increase in tissue temperature. In addition to the alteration of tissue permeability, beneficial effects are obtained through nonthermal changes (e.g., stimulation of fibroblasts). With chronic inflammation, using continuous or nonpulsed ultrasound can produce thermal changes that counteract or prevent the chronic changes of scarring and tissue edema.


Ultrasound dose is measured in intensity (intensity = W/cm2), which is the acoustic energy delivered through the surface area of the head of the transducer. Areas of inflammation are usually treated with 1 to 2 W/cm2 for 5 to 10 minutes. Results are measured by the improvement (either immediate or gradual) in pain or function of the treated area.



Indications



• Superficial periarticular disorders: bursitis, tendinitis, ligament sprains

• Contracture of joint capsules or adhesive scars

• Neuromas

• Reflex sympathetic dystrophy

• Plantar warts

• Muscular strains, fibrosis, spasm, myositis (limited evidence)


Contraindications



• Allergy to medications being used

• Tumors

• Thrombophlebitis

• Pregnancy (therapeutic ultrasound is contraindicated over the abdomen and pelvis)

• Hemorrhagic or infected areas

• Cardiac disease (therapeutic ultrasound over the cervical ganglia, cardiac area, or an implanted pacemaker may produce a detrimental cardiac reflex)

• Unhealed fracture sites

• Phonophoresis should also be avoided over the following areas:
• Epiphyseal plate in growing bones

• Spinal cord

• Area of previous radiation therapy (wait 6 months before applying ultrasound)

• Eyes


Technique



1 A clinician’s prescription is required for the medications when phonophoresis is administered by a physical therapist.

2 Select an area of inflammation for treatment that is no greater than twice the surface area of the sound head.

3 Select the proper ultrasound equipment (Figs. 229-3 and 229-4).

4 Cleanse the general area to be treated. Inspect the skin for excessive dryness and trim excess hair. Skin areas may be pretreated with moist heat packs to facilitate drug absorption by dilating the hair follicles.

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  4. Compartment Syndrome Evaluation

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May 14, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Transcutaneous Electrical Nerve Stimulation, Phonophoresis, and Iontophoresis

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