Myaesthenia gravis

Anaesthesia in myasthenia

Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab.

DCA, Dip. Software statistics, PhD (physio)

Mahatma Gandhi Medical college and research institute ,

puducherry India

What is myasthenia gravis • MG is an autoimmune disorder – • circulating antibodies to nicotinic

acetylcholine receptors at the neuromuscular junction

• antibodies reduce the numbers of receptors• Symptoms if only 30% receptors are presentreUp to 25% of patients have a concurrent

thymoma, • About 10% have evidence for other

autoimmune diseases

ors reduced to 30% of normal

Clinical features• muscle weakness -an overall fatigability increases with exertion over the course of the day. 14:100,000 age 10 and 40. (bimodal ) Females are more frequently affected• diplopia and ptosis resulting from weakness of the

ocular muscles. • slowly spread to bulbar muscles, which may lead to

aspiration and respiratory failure, and later affect the proximal extremities

Osserman and Genkins• class I (ocular muscles only); • class II (eye symptoms plus mild

generalize weakness); • class III (eye plus moderate

weakness);• class IV (eye plus severe

weakness); • class V (intubation, ventilation)

How to diagnose ?• blood tests for antibodies; • electromyographic recordings; • electrophysiologic evaluation is

often performed and shows a classic decrement in the compound muscle action potential after repetitive nerve stimulation.

cholinesterase inhibitor test (edrophonium test);

• Tensilon test (administration of an

anticholinesterase, e.g., edrophonium).

Improvement is usually seen within 5 minutes

after administration of the drug and lasts for

about 10 minutes

• Imaging (to identify thymoma).

Drugs aggravate Neuromuscular weakness

• Penicillamine • Nondepolarizing muscle relaxants • Aminoglycosides • Procainamide

Some other DD s of myasthenia • Graves' disease• Eaton lambert syndrome • Cranial nerve palsies • Congenital myasthenic

syndromes

Other autoimmune diseases coexisting

• hyperthyroidism is present in

approximately 10% of patients with myasthenia gravis.

• Rheumatoid arthritis, SLE, and pernicious anemia occur more commonly in MG

Treatment • Two problems • I. muscle weakness • Cholinesterase inhibitors

(neostigmine,• Pyridostigmine • (maximal dose )120 mg every 3

hours)

Problem 2. immunosupression

• corticosteroids and• immunosuppressive drugs (cyclosporine,

azathioprine)• Plasmapheresis-(four to eight treatments

over 2 weeks• thymectomy is performed if general

symptoms are present

Anaesthetic challenges Preop evaluation

• preoperative interview that they may be intubated and ventilated when they awaken

• All routine investigations • ECG -- Cardiac arrhythmias and

myocarditis

Preop preparation• pyridostigmine ↓• Bad response ↓ good response• Young old ↓ ↓• Steroids steroids + azathioprine• ↓ ↓• Imp. Not imp imp.→taper steroids →thy• ↓ ↓• Thy add plasma

Preop preparation

• Only plasmapheresis

Preop • Lung function testing• Respiratory and bulbar functions should

be carefully evaluated during the preoperative evaluation

• Preop neurologist evaluation • Preoperative plasmapheresis

Post op ventilation ?? Four Factors disease duration of longer than 6 years, chronic obstructive pulmonary

disease(COPD) unrelated to myasthenia gravis,

• a daily dose of pyridostigmine higher than 750 mg,

• and a vital capacity less than 2.9 L.

Premed

• Anticholinesterase to continue ??• Small dose benzodiazepine • Anticholinergics

Anaesthetics-Nondepolarizing Neuromuscular Blockers

• Long acting NDNMB (pancuronium, pipecuronium, doxacuronium) :avoided

• Intermediate and short acting: used with careful monitoring..

Depolarizers nondepolarizers

Succinylcholine

• resistance to depolarizing agents.( ED95 : 2.6 times of control)

• because of the decreased number of functional acetylcholine receptors

• more likely to develop phase II block• decrease in cholinesterase activity

achieved by anticholinesterase treatment

So regarding relaxants

• NDP s more sensitive • Depolarizers more resistant

Inhaled Anaesthetics• Isoflurane , enflurane: decrease

TOF responses

• Sevoflurane at 2.5% depresses EMG responses

• effects of desflurane in MG ??

Intravenous Anaesthetic Agents

• Propofol √• -- no effect on NMJ • Etomidate, althesin and ketamine :

Reports of uneventful anesthesia.• Opioids

– do not appear to depress NM transmission in MG muscle.

– Central respiratory depression may be a problem

Anaesthesia -1 • IV induction • + inh. Drugs + • intubation • Maintain on N2O ,O2, Inh. Agent • No NonDepolarizers • Extubate without reversal

Anaesthesia - 2• Propofol• Scoline • N2O ,O2, Inh. Agent• Nondepolarizers (10% dose with NMJ monitor)• unsuccessful extubation, longer postoperative

mechanical ventilation and hospital stay• Suggamadex or post op ventilation

Regional Anesthesia• Ester anesthetics, metabolized by

cholinesterase, may present particular problems in patients taking anticholinesterases.

• Use reduced doses of amide (lidocaine, bupivacaine) to avoid high blood levels.

• Remember drugs and coexisting diseases

Anaesthesia 3, 4• TIVA for the management of myasthenics

has been reported.

• Local anaesthesia is successful

Postoperative considerations• Weakness • Pain (local ,epidural opioids )• Myasthenic crisis • Cholinergic crisis • Resume the anticholinergic therapy as soon as possible

after surgery. The postop requirements may be different from the routine preoperative dose and

• careful titration because the IV dose is only about 1/30 to 1/120

Post op problems • Nerve stimulator - bulbar Vs limb muscles • Inspiratory force of > - 25 cm is OK • Trans sternal thymectomy – 50 % req.

ventilation • Trans cervical thymectomy OR• video-assisted thorascopic (VATS)– • less post op ventilation ,remission more ??• Early thymectomy better !!

Your icu ready

Myasthenic crisis • Myasthenic crisis is a life-threatening

condition, which is defined as weakness from acquired myasthenia gravis (MG) that is severe enough to necessitate intubation

precipitants• infection.• Surgery• Pregnancy,• certain antibiotics (aminoglycosides,

erythromycin and azithromycin), cardiac drugs (beta-blockers, procainamide, and quinidine), and magnesium.

• TREAT VIGOROUS WITH POSSIBLE OPTIONS

Cholinergic crisis• excess of cholinesterase inhibitors (ie,

neostigmine, pyridostigmine, physostigmine)

• resembles organophosphate poisoning.

• excessive ACh stimulation of striated muscle at nicotinic junctions produces flaccid muscle paralysis that is clinically indistinguishable from weakness due to MG.

Cholinergic crisis• Miosis and the SLUDGE syndrome (ie,

salivation, lacrimation, urinary incontinence, diarrhea, GI upset and hypermotility, emesis) also may mark cholinergic crisis.

• Despite muscle weakness, deep tendon reflexes are preserved.

Cholinergic crisis• When muscarinic effects are obvious ,

diagnosis is easily made. Antimuscarinics and respiratory support are given

• EDROPHONIUM TEST WILL DIFFERENTIATE BOTH CRISES

Myasthenia and pregnancy• Exacerbations of myasthenia must be

anticipated during pregnancy• Epidural analgesia and anaesthesia can be

used for labour and delivery• Muscle relaxation induced by regional

anaesthesia may compound the weakness caused by myasthenia.

Myasthenic syndrome • Acq. Disorder • Small cell ca of lungs • IgG antibodies to pre synaptic voltage dep.

Calcium channels• Abn. Vesicular release • Exercise improves • Diaminopyridine improves • Sensitive to both DPs and NDPs • anticholinesterase agent - not dependable

SUMMARY• Preop bulbar? Anticholinestrase ,

plasmapheresis , premed atropine • GA with propofol, inh. agents ,no NDPs• Post op ventilation • Or GA, relaxants, suggamadex, ventilation • Other surgeries – possible RA, LA • Post op epidural opioids, muscle weakness

Thank you all