Definition
Electromyography (EMG) is the recording of electrical potential of skeletal muscles and the nerves supplying them by inserting small needle electrodes into the muscles.
Indications
- To diagnose myasthenia gravis and myotonia.
- To find out peripheral nerve injury or disease.
- To differentiate among lesions of the anterior horn cell, root, plexus, and specific nerves and muscles.
- To measure conduction velocity of nerves.
- To aid in differential diagnosis of primary and secondary muscle disorders, such as motor neuron diseases and neurovascular junction disorders.
- To localize the site of peripheral nerve disorders, such as radiculopathy and axonopathy.
Interfering factors
- Conduction can vary with age and normally decreases with increasing age.
- Pain can yield false results.
- Electrical activity from extraneous persons and objects can produce false results.
- The test is ineffective in the presence of edema, hemorrhage, or thick subcutaneous fat.
Procedure for Electromyography
The procedure is performed in a special unit.
| Nursing action | Rationale | |
| 1. | Explain the procedure to the patient and obtain informed consent. | Helps in obtaining cooperation of the patient. |
| 2. | Instruct patient that the test may take more than 3 hours. | The length of test depends upon the clinical problem. |
| 3. | Tell the patient to lie down supine in the bed. | Promotes comfort of the patient. |
| 4. | Explain to patient that he may experience discomfort during insertion of needle electrode and there may be hematoma formation after removal of the needle. | Reduces patient’s anxiety. |
| 5. | Ascertain that patient is not on anticoagulants. | Prevents risk for developing hematoma. |
| 6. | A needle is attached to an electrode and inserted into the muscle. A mild electric charge is delivered to stimulate the muscle at rest and during voluntary contraction. The response of the muscle is measured on an oscilloscope screen. The electrode usually causes no pain unless the tip is near a terminal nerve. Ten or more needle insertions may be necessary. | The needle electrode detects electrical potential normally present in muscle. |
| 7. | The nurse and physician observe the oscilloscope for normal waveform and listen for normal quiet sound at rest. A “machine gun popping sound or a rattling sound, such as “hail on a tin roof” is normally heard when the patient contracts the muscle. | Identifies muscle activity. |
| 8. | Record the time and date of the procedure with patient’s response. | Documentation helps in communication with other staff members. |
Postprocedural care
- If the patient experiences pain, administer analgesics as per physician’s order.
- Promote rest and relaxation.
- Interpret test results and monitor appropriately for nerve and muscle diseases.
- Observe needle sites for hematoma formation.
Special considerations
- Enzyme levels that reflect muscle activity (e.g., aspartate aminotransferase, lactate dehydrogenase, creatinine phosphokinase) must be determined before actual testing because the EMG causes elevation of these enzymes for up to 10 days postprocedure.
- There may be hematoma formation at the needle site. Measures, such as application of pressure at the site, controls bleeding.
- During insertion of needle if patient complains of pain, remove the needle because the pain stimulus yields false results.
REFERENCES
- Annamma Jacob, Rekha, Jhadav Sonali Tarachand: Clinical Nursing Procedures: The Art of Nursing Practice, 5th Edition, March 2023, Jaypee Publishers, ISBN-13: 978-9356961845 ISBN-10: 9356961840
- Omayalachi CON, Manual of Nursing Procedures and Practice, Vol 1, 3 Edition 2023, Published by Wolters Kluwer’s, ISBN: 978-9393553294
- Sandra Nettina, Lippincott Manual of Nursing Practice, 11th Edition, January 2019, Published by Wolters Kluwers, ISBN-13:978-9388313285
- Adrianne Dill Linton, Medical-Surgical Nursing, 8th Edition, 2023, Elsevier Publications, ISBN: 978-0323826716
- Donna Ignatavicius, Medical-Surgical Nursing: Concepts for Clinical Judgment and Collaborative Care, 11th Edition ,2024, Elsevier Publications, ISBN: 978-0323878265
- Lewis’s Medical-Surgical Nursing, 12th Edition,2024, Elsevier Publications, ISBN: 978-0323789615
- AACN Essentials of Critical Care Nursing, 5th Ed. Sarah. Delgado, 2023, Published by American Association of Critical-Care Nurses ISBN: 978-1264269884
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