TENSILON TEST (EDROPHONIUM BROMIDE) – Indications, Purpose, Equipment, Procedure, Method, Follow-up, Cholinergic Side Effects of Edrophonium, Positive Test, Utility of Tensilon Test, False Positive Results, Client Preparation, Preparation and After Care
The Tensilon test is a pharmacological challenge study performed to assist in the diagnosis of myasthenia gravis. The drug used in edrophonium chloride (Tensilon), a short-acting form of the drug used to treat this disorder. The test involves the IV administration of the drug before and during the performance of various muscular movements and the evaluation of these movements for changes in muscle strength. A positive diagnosis is made when the administration of the drug results in an improvement in muscle function. A negative diagnosis is made if muscle fasciculations occur as a result of the drug
Myasthenia gravis (MG) is a disease affecting the neuromuscular junction. It is caused by a deficiency of acetylcholine receptor sites on the muscle side of the junction. It is thought that the reduction in these sites is caused by an autoimmune response that blocks the receptor site and is responsible for receptor destruction. The most prominent symptom of the disease is weakness of the involved muscles, which progresses in severity to all areas of the body
Interfering factors: corticosteroids, muscle relaxants, and anticholinergics, which can alter test results by their effect on muscle function or on the action of Tensilon
INDICATIONS
- Diagnosing myasthenia gravis when fatigue and muscle weakness are present, as revealed by an immediate improvement after injection of Tensilon
- Monitoring medication regimen of oral anti-cholinesterase to determine whether increase in dose is advised, as revealed by an improvement in muscle strength after IV Tensilon
- Determining whether an overdose is present, which can place the client in cholinergic crisis, as revealed by an exaggeration of muscle weakness after IV Tensilon
Contraindications: breathing difficulties or apneic conditions, because the disease can cause respiratory difficulties severe enough to require ventilatory support
Acetylcholine is a neurotransmitter chemical that nerve cells release to stimulate your muscles. People with a chronic disease called myasthenia
Definition: A provocative best to diagnose myasthenia gravis, using endroonium bromide
PURPOSE
- To diagnose myasthenia gravis
- To differentiate between myasthenia and cholinergic crisis
EQUIPMENT
- Injection tray with tensilon
- Atropine
- Tuberculin syringe
- 1.5 ml syringe
- 500 ml saline or dextrose as ordered
- Tourniquet
- Spirit
- Cotton balls
- K-basin
- Duster
- Resuscitation equipment
- 12 ventilator and ECG monitor
PROCEDURE
A medicine called Tensilon (also called edrophonium) or a dummy medicine (inactive placebo) is given during this test. The health care provider gives the medicine through one of your veins (intravenously, through an IV). You may also be given a medicine called atropine before receiving Tensilon so that you do not know you are getting the medicine. You will be asked to perform some muscle movements over and over again, such as crossing and uncrossing your legs or getting up from a sitting position in a chair. The provider will check whether the Tensilon improves your muscle strength. If you have weakness of the eye or face muscles, the effect of the Tensilon on this will also be monitored. The test may be repeated and you may have other Tensilon tests to help tell the difference between myasthenia gravis and other conditions
METHOD
Initially
- Dosing: 2 mg of edrophonium is administered intravenously as a test dose
- Monitoring heart rate: bradycardia or ventricular fibrillation may develop
FOLLOW-UP
- After observing for about 2 minutes, if no clear response develops
- Up to 8 additional mg of edrophonium is injected
A double-blind protocol with a saline injection as placebo has been advocated
Testing should be performed with patient free of all cholinesterase-inhibitor medications
CHOLINERGIC SIDE EFFECTS OF EDROPHONIUM
- May include increased salivation and lacrimation, mild sweating, flushing, urgency and perioral fasciculations,
- Atropine should be readily available to reverse effects of edrophonium in case of hemodynamic instability
- Extra precautions are especially important in elderly patients
POSITIVE TEST
- Most myasthenic muscles respond in 30 to 45 seconds after injection
- Improvement in strength that may persist for up to 5 minutes
- Requires objective improvement in muscle strength
- Subjective or minor responses, such as reduction of a sense of fatigue, should not be over interpreted
UTILITY OF TENSILON TEST
- Only useful in patients with objective, preferably measurable, findings on physical examination
- Rarely helpful in the diagnostic evaluation of equivocal cases of MG
- Sensitivity for MG is relatively low (60%) compared to other diagnostic tests
- Tensilon testing should not be used to determine adjustments in the dose of pyridostigmine
FALSE POSITIVE RESULTS
- Can occur in patients with LES, ALS or even localized, intracranial mass lesions
- Positive testing does not necessarily predict response to a longer-acting anticholinesterase drug
CLIENT PREPARATION
- Instruct the client that the test will aid in finding actual causes of muscle weakness
- Check whether the client is taking anticholinesterases drug, whether allergic to any drugs and whether any respiratory problems
- Inform that test will done in semi-intensive care unit
PREPARATION
- Place the client in comfortable position on treatment table
- Load 10 ml of tensilon into syringe with 10 ml of normal saline and administer 2 mg initially
- Watch for respiratory distress and other symptoms
- Inject the remaining 8 ml if no symptoms appear
- Assist in giving exercise to client to reduce fatigue of muscles
- Assist for repeating test if no improvement is found within 5 minutes
- Watch for respiratory failure
- Keep resuscitation equipment and ventilator ready
- Administer adrenaline 2 mg as prophylactic measures
AFTER CARE
- Keep the client in semi ICU for a few hours to monitor for complications, e.g. respiratory failure
- Watch for cardiac changes, e.g. tachycardia
- Assess neurological signs every half hourly for 2 hours
- Transfer the client ward if stable
