Myasthenic crisis

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Information about Myasthenic crisis

Published on June 19, 2016

Author: PravinGare


1. Myasthenia Crisis Dr Pravin Gare SKH

2. I am a Resident Physician…

3. Amitabh Bachchan

4. Snow White and the Seven Dwarfs

5. To Discuss…  Some interesting facts  Pathology of MG  Definition  Clinical presentation  How to diagnose  Evaluation and Management

6.  Most common disorder of neuromuscular transmission.  Best characterized and understood autoimmune disorder.  Fluctuating degree and variable combination of weakness in ocular, bulbar, limb and respiratory muscles.  Antibodies against acetylcholine receptor and/or receptor associated proteins.

7. Coined the term Myasthenia Gravis. Mya-muscle Asthenia-weakness Gravis-serious Mary Walker discovered use of physostigmine in MGFriedrich Jolly 1895

8. Epidemiology  10 to 20% of the patients of MG can have at least 1 episode of crisis in lifetime  13 to 20% of the patients , crisis can be the first manifestation of the disease.  Annual risk of myasthenic crisis among patients with myasthenia gravis is approximately 2 to 3 percent .

9.  MG occurs at any age, involves either sex and begins insidiously  Second and third decades commonest age of onset in women. Seventh and eighth decades in men  Patients complain of specific muscle weakness, not generalized fatigue

10. Definition  Myasthenic crisis is a life-threatening condition, which is defined as weakness from acquired myasthenia gravis that is severe enough to necessitate intubation or to delay extubation following surgery

11.  Respiratory failure can be because of respiratory muscle weakness and/or oropharyngeal muscle weakness leading to upper airway obstruction .

12. Pathophysiology

13. Clinical presentation  Skeletal muscle weakness with true muscle fatigue.  c/o specific muscle weakness  Most commonly worse later in a day or evening or after exercise.  Earlier in the disease symptoms may be absent on awakening.

14.  More than 50% patients present with ocular symptoms of ptosis and/or diplopia, about half will progress to generalized disease in 2 years.  15% patients will present with bulbar weakness c/o dysarthria dysphagia and fatigable chewing.  Less than 5% will present with proximal limb muscle weakness.

15. Crisis..  Increasing generalized or bulbar weakness as a warning.  Respiratory insufficiency can be out of proportion to limb or bulbar weakness.  In a report of 44 patients who developed 63 episodes of myasthenic crises, the crisis began with generalized weakness, bulbar symptoms, or weakness of respiratory muscles in 76, 19, and 5 percent, respectively

16.  Generalized weakness can mask signs of respiratory distress.  Weak respiratory muscles may fatigue suddenly and can lead to respiratory collapse.  Bulbar weakness may cause aspiration upper airway obstruction leading to intubation.

17. Precipitants  Concurrent infections  Pregnancy  Surgical intervention  Tapering of immunosuppressive drugs  Drugs

18. Diagnosis  Simple bedside tests  Lab investigations  Electromyographic studies

19.  Nursing recommendation: Nurses should understand and explain the “ice pack test” and diagnostic imaging to the patient and family to lessen fear and anxiety and elicit cooperation and participation (Level 2).

20. AANN  Nursing recommendation: Nurses should know the adverse events associated with diagnostic testing in MG and how to manage those side effects as needed. Nurses should monitor for results and adverse events associated with the use of edrophonium for diagnostic testing in MG and manage adverse events appropriately (Level 2).

21. Nursing recommendation: Nurses should be familiar with electrodiagnostic testing in MG. Nurses should prepare patients for their experience, including the likelihood of some discomfort (Level 2).

22. Management  Admit to ICU  Assessment of respiratory function  Elective intubation  Rapid therapy  Immunomodulating therapy  Careful weaning  Taking care of complications

23. Admit to ICU  Rapidly increasing weakness secondary to an exacerbation of MG  Frequent monitoring  Symptoms of dyspnoea, severe dysphagia with weak cough and difficulty in clearing secretions.  Signs of respiratory muscle weakness such as poor respiratory effort , shallow breathing , paradoxical breathing

24. Measures of respiratory muscle functon

25. Vital capacity  The VC reflects the mechanical function of both inspiratory and expiratory muscle strength. It can be performed easily at the bedside.  Some experts recommend assessing both supine and sitting VC, as diaphragmatic weakness is more apparent on the supine measurement.

26. MIP  Provides information on inspiratory muscle strength. The patient is instructed to maximally inhale against a closed valve and the force/pressure that is generated at the mouth is recorded.  Inspiration is a negatively generating force and thus values are recorded as negative numbers; a MIP below one-third of normal (eg, 0 to -30 cmH2O) predicts severe respiratory muscle weakness and probable hypercarbic respiratory failure while a MIP of -60 cmH2O is usually associated with a weak cough only.

27.  Monitoring spo2  ABG  Insensitive measures of respiratory muscle weakness because they often develop only after the onset of life- threatening respiratory failure.  However, the development of progressive hypercarbic respiratory acidosis despite therapy may provide supportive evidence that prompts early rather than late intubation.

28.  Nursing recommendation: Nurses should administer drugs that may worsen MG with caution. Review medication profiles with the pharmacist and licensed independent provider (Level 3).

29. Elective intubation  VC falls below 15 to 20 mL/kg  MIP is less negative than -25 to -30 cmH20 (ie, between 0 and -30 cmH20)  clinical signs of respiratory distress, progressive hypercapnic respiratory acidosis despite therapy, and inadequate secretion clearance .

30.  Succinyl choline can be used but dose required is high.  Rapid sequence intubation.  NIV is avoided in MS  Use of chest physio , suction and bronchodilators  Cholinesterase inhibitors should be stopped after intubation.

31. Treatment  Rapid therapy – IV IG , Plasmapheresis  Immunomodulators  Anticholinesterase inhibitors  Thymectomy

32. Weaning off ventilator  Principles of weaning should be the same as for the general population. However, particular attention should be paid to measuring indices of respiratory muscle strength and secretion clearance.  SBTs should only begin after the patient has started treatment with plasma exchange or IVIG and the patient shows evidence of improving respiratory muscle strength, ie, with a VC >15 to 20 mL/kg and a MIP more negative than -25 to -30 cmH2O (eg, -30 to - 60 cmH2O)

33.  Adequate cough and less secretions.  Closely monitor following extubation for early failure using VC and MIP measurements to detect those who may need reintubation.  Tracheostomy

34. Complications  Pneumonia, bronchitis, urinary tract infection,  Colitis caused by Clostridium difficile, bacteremia, and sepsis.  Patients with myasthenic crisis are at increased risk for vascular complications including deep vein thrombosis, heart failure, acute myocardial infarction, cardiac arrhythmias, and cardiac arrest.  There are also several case reports of stress- induced cardiomyopathy (Takotsubo cardiomyopathy) associated with myasthenic crisis

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