{"id":5134,"date":"2011-07-14T20:23:46","date_gmt":"2011-07-14T20:23:46","guid":{"rendered":"http:\/\/crashtext.org\/misc\/5134.htm\/"},"modified":"2014-12-25T12:49:34","modified_gmt":"2014-12-25T17:49:34","slug":"neuromuscular-disorders","status":"publish","type":"post","link":"https:\/\/crashingpatient.com\/medical-surgical\/neuromuscular-disorders.htm\/","title":{"rendered":"Neuromuscular Disorders"},"content":{"rendered":"

Alan Ropper on who needs intubation<\/a><\/p>\n

<\/span>Myasthenia Gravis<\/span><\/h2>\n

ACh receptor antibodies<\/p>\n

Assoc c thymus disorders<\/p>\n

Pathologic fatigability of muscles.<\/p>\n

The most common presenting symptoms are ocular (Ptosis, diplopia).\u00a0\u00a0 If limb weakness is involved it is usually greatest in upper extremities.<\/p>\n

Normal pupils, dtrs, and sensory exam.<\/p>\n

<\/span>Testing<\/span><\/h3>\n

Gaze Testing<\/p>\n

Easiest is extended gaze testing.<\/p>\n

Cold Testing<\/p>\n

If there is ptosis or EOM abnormalities, can perform cold testing.\u00a0 Cover eye c ice pack for 2 minutes and see if sx improve.<\/p>\n

Tensilon\/edrophonium\u00a0 test<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 There are reports of false positives in cases of botulism, eaton-lambert, ALS, GBS, and Cavernous sinus lesions<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Measure the distance from the upper to the lower eyelid in the most severely affected eye<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 intravenous test dose of 1 to 2 mg is given first.<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 If no adverse reaction is found, and the patient does not dramatically improve in 30 to 90 seconds, a second dose of 3 mg is given.<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 If there is still no response, a final dose of 5 mg is given for a total maximum dosage of 10 mg.<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Potential bradycardia from edrophonium, atropine should be available at the bedside. Also, because of the potential cholinergic effect of increased airway secretions, this test should be used with caution in asthmatics and patients with COPD<\/p>\n

Below from Jama 2005;293:1906-1914.<\/p>\n

Box. Edrophonium Test<\/strong><\/p>\n

Establish reliable peripheral intravenousaccess<\/p>\n

Prepare a syringe with 2 mg of atropine (available in0.4-mg\/mL or 1-mg\/mL ampules) to have handy<\/p>\n

Prepare 1 mL (10mg) of edrophonium in a tuberculin syringe (edrophonium is availablein a 10-mg\/mL solution in a 1-mL ampule [10 mg] or in a 10-mLvial [total of 100 mg])<\/p>\n

Inject 2 mg (0.2 mL) slowly over 15seconds while observing for an objective improvement in target muscles<\/p>\n

Improvement should occur within 30 seconds and disappearin 5 minutes; if no response and no significant adverse effects,administer the remaining edrophonium (8 mg [0.8 mL]) for a totaldose of 10 mg<\/p>\n

Atropine should be injected (0.5 or 1 mg) incase of clinically significant bradycardia, respiratory distress,or syncope*<\/p>\n

*Routine administration of atropine simultaneously with edrophonium for the purpose of diagnostic testing for myastheniagravis is not recommended. Bartley and Bullock29<\/a> recommend usinga 3-way stopcock with the edrophonium-containing syringe attachedto the direct port and the atropine-containing syringe attachedto the side port, so that atropine may be quickly injected in case of severe adverse effects<\/p>\n

 <\/p>\n

\"\"<\/a><\/p>\n

<\/span>Diagnostic Dilemma<\/span><\/h3>\n

In treated pts, you must differentiate between too little ACh from myasthenic crisis (undertreatment) or Cholinergic Crisis (Overtreatment)<\/p>\n

Often physical exam can help with cholinergics giving gastric hyperactivity, sweating, and other signs similar to organophosphate toxicity.\u00a0 Sometimes the safer strategy is to withdraw all cholinergic medicine, support patient\u0092s respiratory status and allow the consultant to interpret the patient\u0092s sx as cholinergic crisis can be superimposed on myasthenic crisis.<\/p>\n

<\/span>Assess Resp Status<\/span><\/h3>\n

Patients often look good until just before they require emergent intubation<\/p>\n

 <\/p>\n

An easy bedside assessment used to follow ventilatory status is to have the patient count from 1 to 25 with one breath. With sequential performance of this, a decline in respiratory function will be detected as the patient fails to count as high as before<\/p>\n

Ask the patient to cough and observe the force generated<\/p>\n

Bedside spirometry for NIF and FVC<\/p>\n

FVC (forced vital capacity less 10-12 cc\/kg or a<\/p>\n

NIF (negative inspiratory force) <20 cmH2O may indicate the need for mechanical ventilation. These results may be thrown off by the inability of the patient to make a tight seal around the pulmonary function mouthpiece.<\/p>\n

<\/span>Intubation<\/span><\/h3>\n

Need ~ 50% the dose of non-depol or<\/p>\n

2.6 x the dose of succinylcholine<\/p>\n

(Mt Sinai J of Med 2002;69(1):31<\/p>\n

<\/span>Management<\/span><\/h3>\n

anticholinesterase therapy:\u00a0 pyridostigmine is the oral agent of choice, neostigmine can be used parenterally<\/p>\n

immunosuppressive therapy:\u00a0 prednisone 60-150 mg\/day<\/p>\n

thymectomy:<\/p>\n

plasmapheresis:<\/p>\n

<\/span>Antibiotic Choices<\/span><\/h3>\n

Antibiotics, Myasthenia Gravis, and Risk of Weakness<\/a><\/p><\/blockquote>\n