Myasthenic crisis

Myasthenia CrisisDr Pravin GareSKH

I am a Resident Physician…

Amitabh Bachchan

Snow White and the Seven Dwarfs

To Discuss…Some interesting factsPathology of MG Definition Clinical presentationHow to diagnoseEvaluation and Management

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.

Coined the term Myasthenia Gravis.

Mya-muscleAsthenia-weaknessGravis-serious

Mary Walker discovered use of physostigmine in MGFriedrich Jolly 1895

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 .

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

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

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

Pathophysiology

Clinical presentation

Skeletal muscle weakness with true muscle fatigue.

c/o specific muscle weaknessMost commonly worse later in a

day or evening or after exercise.Earlier in the disease symptoms

may be absent on awakening.

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.

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

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.

Precipitants Concurrent infections Pregnancy Surgical interventionTapering of immunosuppressive

drugsDrugs

Diagnosis Simple bedside testsLab investigations Electromyographic studies

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).

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).

Nursing recommendation: Nurses shouldbe familiar with electrodiagnostic testingin MG. Nurses should prepare patients fortheir experience, including the likelihoodof some discomfort (Level 2).

Management Admit to ICUAssessment of respiratory

functionElective intubationRapid therapyImmunomodulating therapyCareful weaningTaking care of complications

Admit to ICURapidly 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

Measures of respiratory muscle functon

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.

MIPProvides 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.

Monitoring spo2ABG

 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.

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

Elective intubationVC falls below 15 to 20 mL/kgMIP 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 .

Succinyl choline can be used but dose required is high.

Rapid sequence intubation.NIV is avoided in MS Use of chest physio , suction and

bronchodilatorsCholinesterase inhibitors should

be stopped after intubation.

TreatmentRapid therapy – IV IG ,

PlasmapheresisImmunomodulators Anticholinesterase inhibitorsThymectomy

Weaning off ventilatorPrinciples 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)

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

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